Prius NHW10 (MK1) Hybrids - How to test and resurrect them

Batteries, Chargers, and Battery Management Systems.

Re: Is this battery as dead as a dodo? Or a phoenix...

Postby Mr. Mik » Mon Jan 11, 2010 12:50 am

Here are the voltages following an 8 hr overnight rest following the third 1 hr charge with about 85mA:


Entire HP at start: 143.3V
1 7.31
2 -7.27
3 7.23
4 -7.10
5 7.02
6 -7.21
7 7.13
8 -7.15
9 7.30
10 -7.18
11 7.25
12 -7.15
13 7.23
14 -7.10
15 7.13
16 -7.03
17 7.15
18 -7.08
19 7.27
20 -7.29
Entire HP at end: 143.3


I think it means that there are no completely dead cells in this half-pack; otherwise the voltage of the affected stick would have to be around 6.0V !!!

All good so far!
Last edited by Mr. Mik on Fri Jan 15, 2010 4:54 am, edited 3 times in total.
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Re: Is this battery as dead as a dodo? Or a phoenix...

Postby Mr. Mik » Wed Jan 13, 2010 12:33 am

The initially very flat HP continues to do well during carefully stepped recharging.


After four initial charges at about 85mA I continued as follows:


Charging at 0.17A for one hour: 158.6Vmax ; 320.8Ohm

Ah gone in so far: 0.35Ah + 0.17Ah = 0.52Ah

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Stick voltages after 10hrs rest:

Entire HP at start: 148.1
1 7.49
2 -7.47
3 7.44
4 -7.37
5 7.32
6 -7.43
7 7.37
8 -7.39
9 7.49
10 -7.42
11 7.46
12 -7.41
13 7.45
14 -7.38
15 7.39
16 -7.33
17 7.39
18 -7.36
19 7.46
20 -7.47
Entire HP at end: 148.0

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Next step done:
Charging at 0.16A for 2 hrs: 321.0Ohm, 27.0degC; 148.7V at start.
At end of 2 hrs: 160.1V ; 320.9Ohm; 26.9degC; 0.16A

Ah gone in: 0.52Ah + 0.32Ah = 0.84Ah


Stick voltages just after charging finished: 2010-01-11, 1925pm:

Entire HP at start: 159.2V
1 7.98
2 -7.96
3 7.97
4 -7.95
5 7.94
6 -7.97
7 7.97
8 -7.97
9 8.00
10 -7.96
11 7.97
12 -7.95
13 7.97
14 -7.93
15 7.95
16 -7.93
17 7.94
18 -7.94
19 7.97
20 -7.98
Entire HP at end: 158.8V

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''


Next step done:

Charging at 0.32A = C/20 for 2 hrs: 163.1V max; 321.1 Ohm; 27.2degC

Ah gone in: 0.84Ah + 0.32 + 0.32 = 1.48Ah

No individual stick voltage test done - they were so balanced in the above test
that it seems not worth the risk and effort to test individual sticks
frequently. I'll test again once the HP is full, both under charge and after
rest. This allows me to leave the protective plastic covers on the sides of the
HP, making it a lot safer on the workbench!

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Next step done:

Charging at 0.78A = C/8.333, stopped after 5 min.

Decided to remain cautious and take a smaller step in current.


''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Next step done:

Charging at 0.47A = C/14 for 1 hr: 164.8Vmax; 321.3Ohm; 27.8degC

Ah gone in: 1.48Ah + 0.47Ah = 1.95Ah

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Next step done:
After about 8 hrs rest, with HP 159.4V; 320.9Ohm; 25.4degC (=ambient)

I made some changes to my charger and tested it at the following currents on the
HP1:

(microF / resulting charge current into HP at about 160V)
4 / 0.16A
8 / 0.34A
12 / 0.48A
16 / 0.64A
20 / 0.82A
24 / 0.97A
28 / 1.1A
30 / 1.3A
34 / 1.4A
38 / 1.6A
42 / 1.7A
46 / 1.9A
50 / 2.0A
54 / 2.16A
58 / 2.3A
These brief tests went well and as expected, no indication that the HP cannot
easily accept these currents by now.
......................................................................

Next steps:
Repeatedly charging at about 0.6A (= C/10) in 1hr installments (timer
controlled) with recording of Vmax and Rmax of thermistor strip.
(Ambient temperature is always around 25degC to 28degC)


1st Charging at C/10 = 0.6A for 1 hr:
164.8V just after start
166.7V max.
321.1Ohm max
Ah gone in: 1.95Ah + 0.6Ah = 2.55Ah


2nd Charging at 0.6A, 1hr timer.
Starting voltage: 162.2V; 321.0Ohm; 26.7degC
167.2Vmax; 321.2Ohm max; 27.3degC.
Ah gone in: 2.55+0.6=3.15Ah total


3rd Charging restarted for 1hr same settings:
166.0V at start
167.4Vmax.
321.3Ohm max
Ah gone in: 3.15+0.6=3.65Ah total



4th Charging restarted for 1hr same settings:
166.1V at start
167.8Vmax; 321.5Ohmmax; 28.0degC
Ah gone in: 3.65+0.6=4.25Ah total.



5th Charging at 0.6A for 1 hr:
168.3Vmax; 321.3Ohm; 0.6A; 28.7degC (3degC elevated)

Ah gone in: 4.25+0.6= 4.85Ah .


After about 8hrs rest period: 164.4V; 321.0Ohm; 25.2degC (=ambient)

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

And that's where it go to so far!

HP1 has been charged to 75% at C/10 without undue heating of the battery.

When I have time to observe then I'll continue to do C/10 charges for one hour
at a time, until I get a clear temperature rise during the C/10 charge. I might
repeat the C/10 charges a few times, with cooling periods inbetween, until I
think all cells are full to their present capacity level.

Then I'll take the plastic protectors of the HP sides again, check individual
stick voltages under charge and after some rest; and then start to test each
stick with the CBA III (@ 12A to 6.0V cutoff).
Last edited by Mr. Mik on Fri Jan 15, 2010 4:53 am, edited 1 time in total.
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Re: Is this battery as dead as a dodo? Or a phoenix...

Postby Mr. Mik » Fri Jan 15, 2010 4:47 am

The NHW10 HP1 is now fully charged and the sticks are nicely balanced (at least their voltages are)!

I did a total of 13 charges at 0.6A for one hour each (8 further charges since the last update).

During the last few of these "C/10 for 1 hr" charges the HP reached the appropriate voltage for a NIMH string with C/10 charge when full.
This is in my experience 1.44V to 1.445V per cell.
Continuing to charge (after this voltage has been reached) usually results in the ' - delta V ' (negative delta-V) phenomenon, which it also did here.

So far it appears as if the cells in HP1 have all recovered without a hitch!

But of course, only capacity testing can really show what is going on. Voltages alone can be very deceptive with NiMH batteries.

I'll repeat the stick level voltage test once more after a rest period, and then proceed to capacity test each stick individually.

Below are the details of the charges and measurements up to now:

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

2010-01-13: Charging at 0.6A to 1hr limit: Nr 6

163.7V before start; 321.0Ohm; 27.0degC (=ambient)
169.0Vmax; 321.2Ohm; 28.2degC

Total gone in: 4.85Ah + 0.6Ah = 5.45Ah

.....................................................................

Charging at 0.6A for 1 hr Nr. 7:

167.4V start ; 169.3Vmax; 321.5Ohm; 29.7degC (27degC ambient)

Total gone in: 5.45 + 0.6 = 6.05Ah.

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Charging at 0.6A for 1 hr Nr. 8:
167.1V at start. Clos to finish: 31.6degC ; 322.0Ohm; 170.1V; 0.61A
convective airflow apparent with incense stick test.

Total Ah gone in: 6.05 + 0.6 = 6.65Ah.

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Charging at 0.6A for 1 hr Nr. 9: immediate continuation from charge Nr. 8:
171.4Vmax; 322.9Ohmmax; 34.7degC;

Total gone in: 6.65 + 0.6 = 7.25Ah .

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Turned off to let rest overnight.

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Next morning: Charging at 0.6A for 1 hr Nr. 10:
Start V: 164.6V; 321.1Ohm; 26.4degC , 25degC ambient
173.6Vmax; 321.9Ohmmax; 30.2degC;

Total gone in: 7.25Ah + 0.6Ah = 7.85Ah

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Let rest during the day.

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Charging at 0.6A for 1 hr Nr. 11:

Before start: 164.6V ; 28.0degC; 321.0Ohm; 0.6A
At end: 173.7Vmax; 322.6Ohm; 33.3degC

Total gone in: 7.85Ah + 0.6Ah = 8.45Ah

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Charging at 0.6A for 1 hr Nr. 12:
171.5V at start.
173.1Vmax sometime before 28min into charge.
172.9V at 28min; 37.4degC; 324.0Ohm; 0.56A;


Stick voltages a few minutes before end of charge during 0.57A charging (with second DMM, reading slightly different):

Entire HP at start: 171.9
1 8.65
2 -8.62
3 8.61
4 -8.60
5 8.59
6 -8.60
7 8.62
8 -8.61
9 8.60
10 -8.58
11 8.58
12 -8.58
13 8.63
14 -8.62
15 8.63
16 -8.60
17 8.59
18 -8.59
19 8.60
20 -8.60
Entire HP at end: 171.8


6 min before charge end: 172.1V; 326.2Ohm; 41.9degC;

Just before finish: 171.9V; 326.3Ohm; 43.1degC;

10min after charge end: 166.2V; 43.7degC; 326.3Ohm.


Total gone in: 8.45Ah + 0.6Ah = 9.05Ah

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Let rest and cool overnight.

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''


9 hrs later: 163.2V; 321.7Ohm; 27.9degC


Stick Voltages (again with second DMM):

Entire HP at start: 162.6V
1 8.20
2 -8.16
3 8.15
4 -8.13
5 8.12
6 -8.12
7 8.15
8 -8.13
9 8.11
10 -8.10
11 8.12
12 -8.12
13 8.17
14 -8.18
15 8.20
16 -8.16
17 8.13
18 -8.13
19 8.12
20 -8.12
Entire HP at end: 162.6


'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Shortly after these measurements:

Charging at 0.6A for 1 hr Nr. 13:

174.2Vmax recorded during the charge; 174.0Vactual at end; 322.6Ohm; 32.8degC;

Total gone in: 9.05Ah + 0.6Ah = 9.65Ah

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

I declare it "FULL".

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Stick voltages 5 min after charge end:

Entire HP at start: 171.6
1 8.63 (second run at end of measurement: 8.60)
2 -8.60 (second run at end of measurement: -8.58)
3 8.59
4 -8.58
5 8.57
6 -8.58
7 8.60
8 -8.58
9 8.58
10 -8.56
11 8.55
12 -8.56
13 8.60
14 -8.58
15 8.60
16 -8.58
17 8.56
18 -8.56
19 8.57
20 -8.56
Entire HP at end: 171.1

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

The results of measurements after about 10hrs rest, before starting the capacity measurement, were:

322.0Ohm; 29.3degC.


Open voltages:

Entire HP at start: 163.1
1 8.21
2 -8.18
3 8.17
4 -8.16
5 8.15
6 -8.16
7 8.18
8 -8.17
9 8.15
10 -8.14
11 8.15
12 -8.15
13 8.19
14 -8.19
15 8.20
16 -8.18
17 8.15
18 -8.15
19 8.15
20 -8.16
Entire HP at end: 163.1

I don't think it gets much better than that, but my experience comes from working with damaged battery packs; maybe a new pack would be balanced even better?

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Now the CBA capacity test are under way.
Mr. Mik

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Re: Is this battery as dead as a dodo? Or a phoenix...

Postby Mr. Mik » Fri Jan 15, 2010 8:47 am

First 9 sticks done:

NHW10 BlueCar HP1 Stick 01 @ 12A to 6V: 1730pm: 5.83Ah, good curve.
NHW10 BlueCar HP1 Stick 02 @ 12A to 6V: 1812pm: 5.676Ah, good curve.
NHW10 BlueCar HP1 Stick 03 @ 12A to 6V: 1852pm: 5.703Ah, good curve.
NHW10 BlueCar HP1 Stick 04 @ 12A to 6V: 1922pm: 5.746Ah, good curve.
NHW10 BlueCar HP1 Stick 05 @ 12A to 6V: 2000pm: 5.663Ah, good curve.
NHW10 BlueCar HP1 Stick 06 @ 12A to 6V: 2030pm: 5.670Ah, good curve.
NHW10 BlueCar HP1 Stick 07 @ 12A to 6V: 2059pm: 5.761Ah, good curve.
NHW10 BlueCar HP1 Stick 08 @ 12A to 6V: 2134pm: 5.671Ah, good curve.
NHW10 BlueCar HP1 Stick 09 @ 12A to 6V: 2210pm: 5.55Ah, good curve.
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Re: Is this battery as dead as a dodo? Or a phoenix...

Postby Mr. Mik » Fri Jan 15, 2010 9:51 pm

All 20 sticks from the NHW10 BlueCar HP1 have now been capacity tested for the first time.

Here are the results:



NHW10 BlueCar HP1 Stick 01 @ 12A to 6V: 1730pm: 5.830Ah, good curve.
NHW10 BlueCar HP1 Stick 02 @ 12A to 6V: 1812pm: 5.676Ah, good curve.
NHW10 BlueCar HP1 Stick 03 @ 12A to 6V: 1852pm: 5.703Ah, good curve.
NHW10 BlueCar HP1 Stick 04 @ 12A to 6V: 1922pm: 5.746Ah, good curve.
NHW10 BlueCar HP1 Stick 05 @ 12A to 6V: 2000pm: 5.663Ah, good curve.
NHW10 BlueCar HP1 Stick 06 @ 12A to 6V: 2030pm: 5.670Ah, good curve.
NHW10 BlueCar HP1 Stick 07 @ 12A to 6V: 2059pm: 5.761Ah, good curve.
NHW10 BlueCar HP1 Stick 08 @ 12A to 6V: 2134pm: 5.671Ah, good curve.
NHW10 BlueCar HP1 Stick 09 @ 12A to 6V: 2210pm: 5.55Ah, good curve.
NHW10 BlueCar HP1 Stick 10 @ 12A to 6V: 2239pm: 5.635Ah, good curve.
NHW10 BlueCar HP1 Stick 11 @ 12A to 6V: 2313pn: 5.572Ah, good curve.
NHW10 BlueCar HP1 Stick 12 @ 12A to 6V: 2343pm: 5.591Ah, good curve.
NHW10 BlueCar HP1 Stick 13 @ 06A to 6V: 0725am: 5.691Ah, good curve. 6A in
error!
NHW10 BlueCar HP1 Stick 14 @ 12.1A to 6V: 0820am: 5.648Ah, good curve. 12.1A
in error.
NHW10 BlueCar HP1 Stick 15 @ 12A to 6V: 0851am: 5.683Ah, good curve.
NHW10 BlueCar HP1 Stick 16 @ 12A to 6V: 0934am: 5.629Ah, good curve.
NHW10 BlueCar HP1 Stick 17 @ 12A to 6V: 1008am: 5.582Ah, good curve.
NHW10 BlueCar HP1 Stick 18 @ 12A to 6V: 1047am: 5.613Ah, good curve.
NHW10 BlueCar HP1 Stick 19 @ 12A to 6V: 1120am: 5.569Ah, good curve.
NHW10 BlueCar HP1 Stick 20 @ 12A to 6V: 1151am: 5.502Ah, good curve.

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Image

The one test at 6A was due to operator error. The software had crashed and I was not careful enough when I set it up again!
Same for the 12.1A following it. Never mind...
Last edited by Mr. Mik on Mon Feb 08, 2010 5:31 am, edited 1 time in total.
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Re: The temperature sensor strip of the Prius MK1 battery

Postby Coulomb » Sat Feb 06, 2010 8:29 pm

Mr. Mik wrote:The print in the sensor strip:Image
Does anyone know what it means?

I thought that the PSR might stand for Polyswitch Resettable. It's probably now made by this company:
http://www.circuitprotection.com/polyswitch.asp
I didn't do much good searching for 24155 on that site, though there were some reasonable matches to devices with no information available on the website. This might be because they are now obsolete, or because Toyota wanted a paticular design custom made, so the details of that part aren't available to others.

These polyswitches are used in place of fuses, so they are rated by current, not temperature. So maybe these are really just positive coefficient thermistors, or at least should be replaced with PTC thermistors.
Last edited by Coulomb on Tue Nov 11, 2014 5:40 pm, edited 1 time in total. View post history.
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A Phoenix or a Dying Swan???

Postby Mr. Mik » Fri Feb 12, 2010 8:26 pm

I have had an unexpected result: A repeated capacity test after 5 recharge / discharge cycles shows reduced capacity of all sticks in the NHW10 BlueCar HP1 sticks!

The discharge curves with 6V cutoff are from the first capacity test, done after the first recharge from deeply discharged and neglected state.

The discharge curves down to 5.4V are the ones from the capacity test done after a further 5 charges and 4 discharges.

Image

Click thumbnail for better quality picture: Image

(I have misnamed several of the sticks tests in the overlay and cannot change what the CBAIII puts on the screen. All the tests are in fact the BlueCar HP1 sticks, not the NFG battery sticks.)

What I expected was a capacity increase with a few more cycles, but in fact the capacities of all sticks are reduced by about 5%.

Why is this the case?

Two possible explanations come to mind:

1) The prolonged, almost total discharge was acting as a reconditioning cycle, restoring the maximum capacity which the cells are still capable of. With the further 5 cycles (which were not over-discharging the cells past 0.9V) the capacity returned to the real level and will remain relatively stable there. (When I do reconditioning cycles on NiMH batteries on purpose, I discharge them at about C/50 to 0.4V cutoff with good results during the next discharge. But I have never systematically tested if these results disappear again, at least partially, over the next few cycles!)

2) The "Universal Freddy charger" might be doing some damage to the batteries, possibly due to excessive ripple in the output voltage / current.

I stopped using the Universal Freddy and ordered an oscilloscope to rule out damage due to the charger and/or improve it by adding smoothing measures to it's output and testing what works best. But the scope broke soon after I started to play with it, and the seller tells me that there is some spring festival holiday period going on in China, which stops apparently everything for the next 10 days or so. So it will be a while before I get a result with that broken scope! I might just fork out the money and buy one from Jaycar in the meantime.
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Re: Prius Mk1 Batteries - How to test and resurrect them

Postby Mr. Mik » Tue Feb 16, 2010 8:56 am

I got a USB scope now, and it works somewhat. I cannot really tell if the thing is malfunctioning or not, but it sometimes seems to do strange stuff until the program gets rebooted and the hardware disconnected and reconnected.

And I cannot figure out how to calibrate it and set the zero point...

So all these results might be rubbish!

The thumbnails below lead to screenshots of the USB scope measuring the voltage drop across a 10mOhm shunt. The shunt is in series with the Freddy charger and the HP2 out of the BlueCar NHW10 battery (120s NiMH, 6 or 6.5Ah). Battery is empty, started at around 145V, at end of experimenting it was about 155V.

The title of the scope graphs describe details about them: Charge current, motor run capacitor used to achieve this current, and either 12 Ohm resistor added in series or no resistor added. The resistor should probably be located between the smoothing capacitors, but for this experiment I simply put it in series with the charger output.

The actual zero line should be where 0.01V is, in the next post I will post the graph showing no charge current (the forum software will only allow 10 pictures per post).

Image
Image
Image
Image
Image
Image
Image
Image
Image
Image

If I interpret these graphs correctly, then the Freddy charger without resistor creates so much 100Hz ripple that the charge current becomes negative for a short time each 1/100th of a second. EDIT 2010-03-23: That's rubbish - faulty thinking. The diode in the charger prevents any reverse curent flow, ever. The charger output is ripply, but always directed into the battery.
With a 12 Ohm resistor, there is still a lot of ripple, but the current always goes into the cell.

I have been using the 8microF / 0.64A setting to cycle the HP1 5 times, without smoothing resistor.

Is that likely behind the 5% capacity reduction?
Last edited by Mr. Mik on Mon Mar 22, 2010 3:12 pm, edited 1 time in total.
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Re: Prius Mk1 Batteries - How to test and resurrect them

Postby Mr. Mik » Tue Feb 16, 2010 9:03 am

Here is what the scope shows when no current is going through the shunt. It stubbornly claims -0.01V when it should be zero....

Image

Any help with figuring out how to properly use this scope, and what the results mean (if anything), would be greatly appreciated!


The charger used is similar to this one (but has now a 16microF instead of the 20microF motor-run capacitor):

Image

I think it needs some more work! A few extra smoothing resistors, exact values to be determined experimentally as soon as I am more comfortable using the scope.

The scope is a PoScope USB scope similar to this package: http://www.poscope.com/product.php?pid=13
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Re: A Phoenix or a Dying Swan???

Postby Mr. Mik » Mon Mar 22, 2010 3:09 pm

Mr. Mik wrote:I have had an unexpected result: A repeated capacity test after 5 recharge / discharge cycles shows reduced capacity of all sticks in the NHW10 BlueCar HP1 sticks!

...
...
...

What I expected was a capacity increase with a few more cycles, but in fact the capacities of all sticks are reduced by about 5%.

Why is this the case?

Two possible explanations come to mind:

...
...
...


It turned out that I fell into the same old self-discharge trap that has gotten me a few times before - I'll learn one day!

It was the same problem that causes the early demise of many Vectrix packs and the destruction of the Prius MK1 batteries: Differential self-discharge rates at different temperatures.

I had tried to control the self discharge between the repeated tests by letting the same number of hours pass between charging fully and beginning capacity testing (about 9hrs).

But the first charge was terminated with a battery temperature of about 34degC, because I was cautious and gave it a top-up after several short charging bursts with frequent observation to rule out possible overheating.

As I got more experienced (and the battery characteristics became known to me), I was able to do a full charge in one relatively fast move. This caused the battery to be about 44degC warm when fully charged.

The self-discharge rate at 44degC is much higher than at 34degC, and although the ambient temperature was similar at about 26degC, the batteries would have spent the 9hr wait at a significantly higher temperature then the first time. That's the cause of the apparent capacity loss after 5 charges.

I have returned to using the charger with good success. The Prius I bought in December ran very well for 2.5 months, then started to show small signs of battery imbalance (ICE running at increased idle speed to charge the battery a few times, and a single "Turtle" on the dash display).

I stopped driving the car and did an EQ charge (with battery remaining in the car) - the cars performance has returned to very good immediately.

An EQ charge done on a friends car has also had a very good effect on the cars performance, time will tell if it lasts several months or just a few days. It depends on many variables, particularly the state of health of the battery.
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A Phoenix with a clipped wing....easily fixed!

Postby Mr. Mik » Mon Mar 29, 2010 7:42 am

The deeply discharged NHW10 battery described earlier has now undergone further testing which has shown that it is in in good health, except for a single "stick" out of the 40 sticks (with 6 cells each)!

In short, the test is a full charge followed by about 3 weeks rest to allow self-discharge to occur. This is then followed by a stick-level capacity test at 12A with the CBAIII.

Here are the results for HP1:
Image
Image

And here the results for HP2:
Image
Image

A nice battery except for the one stick (S34) that dropped off early in the self discharge test! And that is most likely due to a single cell in that stick. One cell out of 240, but the NHW10 ECU will detect it and limit vehicle performance severely each time the cell hits empty. And because I have spares, it is easily fixed!

I am quite certain that I will use this sort of test as the main testing procedure for the other batteries I have lying around. It requires a lot of time, but relatively little operator input during this time.

With hindsight this result was already apparent after the first capacity test (after HP2 charge number 5), in which stick S34 was the worst:
Image
Image
These test were done from 10hrs to 42hrs after end of charging; S34 was tested 40hrs after end of charging.

But the result was not as clearly visible, and I think I would have been worried that there might be other sticks with problems hiding. The three week test satisfies me that this S34 is the only problematic stick in the battery.

The optimised procedure to test an unknown NHW10 battery half-pack:

1) Slow charge to up to 140% capacity. Depending on ability to actively cool the batteries one may use up to C/10 = 0.6A charge current. But it may go up in flames without active cooling at that charge rate! 100mA is much safer until the battery is known to be good. If both half-packs are left in the battery housing, then the cooling impellers can be used to provide powerful active cooling.

2) Discharge half-pack through a 400W incandescent light globe array. Monitor for sudden 1.2V drop (within a minute or so) by recording with a DSO or similar device, drawing a graph.
For a single reversing cell it looks like this on the PoScope monitor graph (in this case in a Vectrix 102s NiMH pack):
Image
Channel A (red): Voltage measured by x100 probe (1/100 x battery voltage).
Channel B (blue): Voltage measured by x1 probe across a 10 Ohm resistor (10 x discharge current).
X-achsis: time in hrs:min:sec:msec
Using a scope this way makes it clearly visible when a single cell reverses in such a long string! Of course, other forms of monitoring would also work. It is also possible to build a relatively simple circuit which detects such a small voltage drop and automatically terminates the discharge.

3) Repeat 1) and 2) several times to exercise the battery. How often depends on how long it had been left unused (and other factors).

4) Leave battery to rest for several weeks after a full charge (temperature dependent). So far I figure 3 weeks is a good amount of time to wait in 25degC. This test will find out the bad cells which may have good immediate post-charge capacity, but increased self-discharge rate.

5) Capacity test after the rest period. Ideally individual sticks, but one could also discharge Half-packs (to find the weakest stick quickly) whilst monitoring with the scope as above. Once a reversing cell is being detected by the sudden drop in the discharge graph, the 20 sticks of the HP are voltage tested (still under load); the stick with the weakest cell will have a voltage of about 1.2V below all the others.


But only individual stick testing can give you the detailed information you need to decide how to best repair the battery. In the above example of the NHW10 BlueCar battery it is clear that the one outlier stick can be replaced and then the battery will be good. Testing HP's will only find the weakest stick, but will not tell you if another one has only slightly better capacity then the worst one.
With individual stick capacity testing you would also be able to identify the few good sticks in a badly damaged battery.
Last edited by Mr. Mik on Wed Aug 25, 2010 5:13 am, edited 7 times in total.
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Re: Prius Mk1 Batteries - How to test and resurrect them

Postby Mr. Mik » Mon Mar 29, 2010 8:05 am

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Re: Prius Mk1 Batteries - How to test and resurrect them

Postby Mr. Mik » Mon Mar 29, 2010 4:28 pm

The post viewtopic.php?f=14&t=12764&p=211975#p211975 was edited to show how to clean the MAF sensor of the NHW10 Prius MK1.
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Re: Prius Mk1 Batteries - How to test and resurrect them

Postby grindz145 » Tue Mar 30, 2010 8:14 am

In you're experience are these packs easy to find at junkyards etc? I am assuming they air fairly cheap. I am quite interested in getting some of the commutation inverters and possible even an electric motor out of one... :twisted: Very nice work!
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Re: Prius Mk1 Batteries - How to test and resurrect them

Postby Mr. Mik » Tue Mar 30, 2010 3:35 pm

grindz145 wrote:In you're experience are these packs easy to find at junkyards etc? I am assuming they air fairly cheap. I am quite interested in getting some of the commutation inverters and possible even an electric motor out of one... :twisted: Very nice work!

This depends very much on where you are!

AFAIK, the NHW10 has been exported as used vehicles in significant numbers to the UK, Australia and New Zealand. The does not seem to be a shortage of broken ones around Australia; I have two working ones now and one "Research Vessel" which I hope I will get into a good enough state to run it around on private property to test batteries, other components and maybe PHEV conversion options. All were very cheap because of problems with the main battery. The last two also had accident damage and needed to be re-combined into one good vehicle and one that's just for spares if needed later on.
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A link to the Powe Split Device (PSD)

Postby Mr. Mik » Wed Mar 31, 2010 8:18 am

This is very neat! An animated simulation of the Prius PSD where you can alter the parameters and see the result.

http://www.wind.sannet.ne.jp/m_matsu/prius/ThsSimu/

The heart of the Prius, so to say....

Is there any good reason to not use the PSD with a powerful electric engine instead of the ICE?
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Re: Prius Mk1 Batteries - How to test and resurrect them

Postby Mr. Mik » Fri Apr 16, 2010 9:25 pm

Something new about the battery which came with the car I bought in Dec 2009 posted above at: viewtopic.php?f=14&t=12764&p=252369#p252369

Looks very repairable!
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Re: Prius NHW10 (MK1) Hybrids - How to test and resurrect th

Postby peterperkins » Sun May 16, 2010 12:53 am

Interesting thread.

Identical cells are also used in the Honda IMA based vehicles Insight/Civic etc. They also suffer from imbalance issues over time mainly as a result of self discharge variations. Heat in the centre of packs also causes IR and self discharge variations between subpacks (a stick of six cells) The honda cars have no balancing or cycling capability so the imbalance fault is inevitable in the end.

The insight forum have a few members now who have considerable experience with repairing these packs. I repair them in the UK for Insight owners. The subpacks respond well to aggresive cycling on the bench with a decent charger such as the Overloader or similar. It can take upto 10 cycles to restore capacity with apparently poor subpacks. www.insightcentral.net

In order to repair packs here in the UK I dissasemble the batteries and cycle/exercise all the sticks noting capacity under charge and discharge until it recovers to an acceptable level. Critical is the self discharge rate which can be determined by leaving the sticks for a week and then discharging them to the cutoff point and working out lost capacity. Then I select/match the closest 20 sticks from my stock and reassemble them into a pack.

The temp sensor strip is a PTC resistor sensor and changes resistance rapidly as temp gets upto 70-90C. The cutoff PTC cell overheat alarm point in the Insight is an amazing 90C. The Insight battery fan which is controlled by four other sensors does not operate until the battery reaches 55C. This is too high IMO and leads to excessive heat in the batteries.

The completed packs respond well to CC low current charging and we use 250-350ma at 170V to charge a 144V nominal pack.

The sticks used in the Insight can deliver 100A or accept 50A regen.
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Re: Prius NHW10 (MK1) Hybrids - How to test and resurrect th

Postby Mr. Mik » Sun May 16, 2010 5:14 am

peterperkins wrote:Interesting thread.

Identical cells are also used in the Honda IMA based vehicles Insight/Civic etc. They also suffer from imbalance issues over time mainly as a result of self discharge variations. Heat in the centre of packs also causes IR and self discharge variations between subpacks (a stick of six cells) The honda cars have no balancing or cycling capability so the imbalance fault is inevitable in the end.

Do you know if they are 6.5Ah or 6Ah cells?

The imbalance can be fixed (temporarily) by EQ charging. I'm working on an EQ charger to do the whole 240s pack at once, it's almost ready.

The insight forum have a few members now who have considerable experience with repairing these packs. I repair them in the UK for Insight owners. The subpacks respond well to aggresive cycling on the bench with a decent charger such as the Overloader or similar. It can take upto 10 cycles to restore capacity with apparently poor subpacks. http://www.insightcentral.net

In order to repair packs here in the UK I dissasemble the batteries and cycle/exercise all the sticks noting capacity under charge and discharge until it recovers to an acceptable level. Critical is the self discharge rate which can be determined by leaving the sticks for a week and then discharging them to the cutoff point and working out lost capacity. Then I select/match the closest 20 sticks from my stock and reassemble them into a pack.

I have a charger that can do up to 5 charge/discharge cycles (discharge at only 0.7A) for a 6-cell stick. But I find it so very tedious and time consuming to do each stich that way!
How many cells are in the Honda packs? IIRC it 120cells, right?

I prefer to charge a 120s half-pack, then discharge it (also in series) for cycling. The problem is of course that I have no automated shut-off mechanism yet to detect a single cell dropping to zero V, and to stop the discharge automatically at that point. I have some suggestions (from someone who has given me lots of good advice and seems to know what he is talking about!) about how to build such a device, but have not had time to build it so far. I have managed to use a USB Digital Storage Oscilloscope in such a way that I can spot the 1.2V drop when a single cell in 120 cell string (or in 102 in my Vectrix) drops to zero V. But, I need to sit there and watch, and that is not good!

The temp sensor strip is a PTC resistor sensor and changes resistance rapidly as temp gets upto 70-90C. The cutoff PTC cell overheat alarm point in the Insight is an amazing 90C. The Insight battery fan which is controlled by four other sensors does not operate until the battery reaches 55C. This is too high IMO and leads to excessive heat in the batteries.

The EQ charger I am building can (on the bench so far...) detect a 120 Ohm rise from the 640 Ohm of a 20degC 240s pack. That equates to a battery temperature of 55degC or a single cell reaching 75 -80 degC. The charger automatically turns off the charge current (but continues the power supply to the cooling impellers) when the resistance of the PTC resistor sensors gets too high.
The trouble I am struggling with at the moment is how to turn off the charge current when the cooling impeller is not running. I want that double safety in the charger, because charging at 0.6A can possibly set the battery on fire.
The completed packs respond well to CC low current charging and we use 250-350ma at 170V to charge a 144V nominal pack.

The sticks used in the Insight can deliver 100A or accept 50A regen.


For regular EQ charges (every few months or so), I want to charge the entire 240s battery at 0.6A to keep the time for a complete EQ charge as low as possible. It will still take an entire day and night that way!

Measuring the current in and out of my NHW10 Prius battery I found this:

Maximum current draw: 108A

Maximum regen current: 60A
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Re: Prius NHW10 (MK1) Hybrids - How to test and resurrect th

Postby peterperkins » Sun May 16, 2010 12:16 pm

The cells are 6.5ah although only 4ah is used by the honda system 20-80% soc approx.

The robotronic overloader can charge at 8A and discharge at 20A so gives them a good workout.

I am working on a multisubpack balancer which has 20 subpacks fitted to it, and then uses a pic to manage charging each one in turn, all automated and dumps data to a netbook running excel. I'll post details when it's finished. it will have a 50A charge/discharge capability to really give them a work out.

It's a reaL doddle to make a high voltage CC supply to charge the cells in a complete pack at 350ma.

You need one of these

http://www.meanwelldirect.co.uk/product ... efault.htm

and as many of these as reqd in series with the above to bring the total output voltage upto you pack charged voltage.

http://www.meanwelldirect.co.uk/product ... efault.htm

Total price under £100 if you shop around.

The LED CC supply does all the work ;)

Total time for a full pack balancing charge assuming one cell in the pack is completely empty and needs a full 6.5ah < 20hrs

We tend to only do full pack balancing monthly or weekly maximum. if the cells/pack are going out of balance faster than that then the pack needs ovberhauling.
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Re: Prius NHW10 (MK1) Hybrids - How to test and resurrect th

Postby Mr. Mik » Sun May 16, 2010 4:58 pm

Interesting idea!

But, it does not do all the work!

It also needs to power the cooling impeller and turn the charger off when the battery is getting too hot, the impeller is not running and/or the charging time is over.

Otherwise one risks setting the battery, car and garage on fire!
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Re: Prius NHW10 (MK1) Hybrids - How to test and resurrect th

Postby peterperkins » Sun May 16, 2010 11:05 pm

In testing on numerous insights unless you live in arizona then the packs do not heat up to dangerous levels with 350ma charge current.

Some people do power the fan, most do not. We don't bother with a charger cut off, a simple plug in timer can do.

Guestimate soc from car soc gauge, dial in suffcient charge hours using timer to balance pack and let it get on with it.
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Re: Prius NHW10 (MK1) Hybrids - How to test and resurrect th

Postby Mr. Mik » Mon May 17, 2010 2:46 am

Thanks for the explanations! I have never seen the Insight battery pack. Does it allow for spontaneous convection cooling?

When I charge Prius NHW10 half-packs onto the bench, with relatively good spontaneous air flow through the half-pack (due to putting it on wooden "spacers"), then the top layer of cells still heats up to 35degC in 25degC ambient temps @ 100mA charge current.

I had to terminate attempts to charge at higher rates because I did not want the cells to go above 40degC. They self-discharge a significant part of their charge in such circumstances while they cool down. The self-discharge is not necessarily bad if you want to achieve equalisation, but I think the heat also ages the cells.

Have you actually used the current limiting SMPS and the other "booster" SMPS' which you suggested for this application? I ask because some SMPS seem to be producing a fully isolated or "floating" DC output, and others do not. I may work with some, but not with others!
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Re: Prius NHW10 (MK1) Hybrids - How to test and resurrect th

Postby peterperkins » Mon May 17, 2010 7:39 am

Have a look on Insight central for details/pics of the battery pack / chargers etc it has limited convection cooling.

Bear in mind the insight normal battery fan does not start operating until the pack reaches 55C. The PTC strip alarm for an individual cell overheating and the IMA shutting down is an incredible 90C

So you are being very conservative.

Yes the psus do work correctly and are fully isolated floating DC output I've sold quite a few as pack chargers for Insight owners.

I would say the insight does tend to let the pack get a bit hot, I think 45c as a normal maximum is more realistic and probably better for it in the long run.
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Re: Prius NHW10 (MK1) Hybrids - How to test and resurrect th

Postby Toorbough ULL-Zeveigh » Mon May 17, 2010 3:54 pm

Mr. Mik wrote:Do you know if they are 6.5Ah or 6Ah cells?



chart on this Prius page sez 6.0 Ah for the NHW10.
confident enuf to correct wiki?
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the optimist engineer sees that the glass has a 100% safety tolerance.
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