[what to do now?] 1st 13s 20Ah battery pack surgery

[made_in_the_alps_legacy]

Help,
My EMC 120 48V 2A charger seems to charge my 48V 20Ah battery to 53.6V only

The charger :
http://www.enerise.net/products/135.html

The battery :
http://res.bht-diffusion.com/velo/batterie/bht-48V-20ah-2C-DATASHEET.pdf

I am hardly getting 800Wh from the battery, I think if the charger would charge to 1 or 2V more,
I would be closer to the expected capcity of 960Wh

What should I do ?

 

[dnmun]

how do you know if the voltmeter is accurate? did you measure the output voltage of the charger without the battery present?

 

[made_in_the_alps_legacy]

Thxs for your follow up

how do you know if the voltmeter is accurate?

the voltage was measured by 3 different ways, 2 different voltmeters and a powermeter :
the discrepency between those 3 measurements has been found to be about 0.2V
(1 voltmeter shows 53.5, the powermeter 53.4, 1 voltmeter shows 53.6)

did you measure the output voltage of the charger without the battery present?

Yes, is it wrong ?
please see also this extract from my built thread if it helps :


I am getting familiar with this set up. I think the autonomy should be higher,
I checked the voltages after several hours battery connected to the charger (even after charger stopped charging):
- the voltage measured at the charger output is 53.6V
- the battery voltage is also 53.6V at the end of charge
- the powermeter shows a bit less - 53,4V

I seek for advice : the battery datasheet mentions a
"Charge Voltage limit" of 54.6V and a "Protected Charge Voltage" of 55. 25V -
dnmun mentions even more...

I am pretty sure I could get closer to the specified battery capacity if the charger would charge 1 or 2V more
Does the charger needs some tweeking ?
If the charger supplies more than the battery specs values above,
does it mean the BMS will take over to stop charging ?
Sorry, I am a bit lost there



I am willing to open up this charger if you help me deciding that it's needed,
(it's clearly written "CAUTION : Amateur technicians do not open the box" )

 

[dogman dan]

I don't know the charger, but if it has one, the voltage adjust pot is usually very close to the place on the board where the DC cord attaches. Look for a tiny box with a top you can put a screwdriver.

 

[made_in_the_alps_legacy]

Thxs, yes, I went through those topic below
and understand I have a chance to set the charger output voltage a bit higher by a trimpot which is likely to be located in the LED / DC cord corner

http://endless-sphere.com/forums/viewtopic.php?f=14&t=62058&p=934521&hilit=charger+voltage#p934521
http://endless-sphere.com/forums/viewtopic.php?f=14&t=51407

Before I do that,
- what should I do with respect of the caution message "high voltage Inside machine" ? is it still true once unplugged from AC ? which components should I stay the most away from - all the capacities I guess ?
- Something I hardly understood along above topic, which way is best to know at which voltage I go ? just leave a multimeter connected and turn the trim pot ?

 

[made_in_the_alps_legacy]

I just opened it and see the mentionned trim pot "VR2" :

 

[made_in_the_alps_legacy]

hummm...

Now I am cross checking the charger specs with the baterry specs from the links posted above
From the battery specs, 54.6V "charge limit voltage" mentionned, charger specs 54.6V as charge voltage is for Li Ion...

Unclear for me is if my battery is Li Ion or Li Po, it was always mentionned as Li Po,
even along the other manufacturer specs for this model ("48V 20Ah 4P13S 7063135") is announced as LiPo
but still with a "charge limit voltage" looking like a LiIon (54.6V)

so... when tuning the charger voltage, should I go to 58.4V as for a Lifepo4 ?

 

[dnmun]

you did not have to remove the pcb from the alloy case. you have to be able to put it back together first before adjusting the voltage. those two switching transistors have 340V across them and that can hurt a lot.

when you put it back together, pay very close attention to how the little insulating rubber shields fit behind the switching transistors. the back side of the transistor is at 340V DC and the case is ground so if they are not aligned carefully so that the shields cover the entire backside of the transistor then it will short to the case and blow up.

if the case is not grounded because you left off the case ground or have a bad ground at the AC outlet you can be shocked by touching the case if the transistor shorts. so do that and be careful when you power it up.

then you can adjust the output voltage.

in terms of technique: put the pcb back in and as you slide it in bend the transistors away from the case a little so they don't hook on the little insulating pads as it slides past them. you wanna keep those little insulators in their original spots stuck in the white heat sink compound. you should be able to see the original outline. so pay attention there.

when you have them all aligned, push the transistors back against the insulators, use new heat sink compound if you have some but keep dirt and especially keep any metal filings out of the layer behind the transistor. then line up the holes for the clamps and put the screws in loosely for all of the clamps first and when it is all aligned and you know it will fit then tighten the screws, and be sure to reconnect the ground to the case. the case ground on these alloy chargers is critical and they should be used on a grounded outlet and if you have GFCI that helps too if the switching transistor ends up shorting through the insulator to the case.

 

[made_in_the_alps_legacy]

dude! 340V DC between the case and the backside of the transistor ?? thxs for letting me know - I got the point

Luckily I dropped the case and realized the upper cover can be removed... amaizing what we can learn without endless sphere...
and thanks mr. Newton for helping me to truly be able to put it back together...

Now I see they grounded the case by the clamps which also holds the transistors... by the isolated part of the transistor I guess...

 

[dnmun]

yes, the clamp squeezes against the plastic that covers the silicon bit that the transistor is on. the transistor is bonded to that metal tab which is the collector of the npn transistor.

 

[dogman dan]

Maybe what you have is supposed to charge to 53.6v only.

I assumed you knew what the battery was. Better find out before turning up to 58v.

 

[made_in_the_alps_legacy]

Maybe what you have is supposed to charge to 53.6v only.

I assumed you knew what the battery was. Better find out before turning up to 58v.

He he he... well... too late
I did carefully follow dnumm advice, set the trimpot to have 55v as chearger output, plugged the batery for charging, monitored thé voltage with the powermeter and fond Nice to see the charger stopping with thé powermeter showing 55.02v

But then, as soon as i unplugged the charger, thé powermeter shutted down
Now i mesure 54.0v at thé charging plug, and 48v at thé battery plug (the powermeter does not start anymore when plugged at the battery
But thé bike is not running anymore...
I did not notice any heat build up or battery deformation...

At least we can fairly state that you are/were right dog man...

What to do now? If it's the BMS hvc which kicked any chance to draw some current to get back as before?

 

[dogman dan]

Tap the main leads of the pack before the bms, and discharge from there. 110v lightbulb should work.

 

[made_in_the_alps_legacy]

OK dogman- I guess I have to take the battery apart since the BMS is heat shrinked within the battery?

I don't understand why I can measure 48v at the battery female plugs going to the controller - when I plug the controller nothing happens - if I plug the powermeter, it doesn't power-up and I measure 2.5v on the "load" side of the powermeter with controller unplugged.
Now I measure 48v at the battery charging plug (was 54v few hours ago)

Anyway, will leave it as it is until I feel less "amateur technician" if it ever happens
I think I got fooled by the battery specs but I don't think 55,0v instead of 53,6v was such a risk

 

[dnmun]

did you post up a picture of the battery? there should not be need to cut it open. if you measured voltage on the output of the battery then it is working. sounds like your connector to the battery itself is bad or wired improperly.

 

[made_in_the_alps_legacy]

There is picture of this battery in my built thread (linked below), the specifications were also repeated at the beginning of this topic and there are plenty of cross references along the manufacturers for this "48V 20Ah 4P13S 7063135" as mentioned few posts above.

Edit: I just got it back to life - checked charger voltage 55.1v - plugged the charger back to the bat - got no charging & no power to the poweemeter - unplugged the charger - reduced the voltage to 54.4v - plugged the charger back to the bat - got no charging but got powermeter showing 54.37v- unplugged the charger - plugged the controller and went for a ride

Weird?

 

[dnmun]

no, not weird, the charging stops when one cell climbs above the HVC and you have to discharge the cells down to the reset voltage before it will charge again.

 

[made_in_the_alps_legacy]

I haven't discharged the cells. I was not expecting the charger to restart charging since I was confident that the battery was still above 54v - what remains weird for me was to recover those 54v at the battery output while tuning down from 55v charger voltage

 

[dnmun]

when the shunt balancing resistors on the high channel drain it down to the reset voltage then the charging mosfet turns on again so it charges again.

 

[made_in_the_alps_legacy]

OK thxs, but it did not charge, it was a like a BMS protection which got removed, the power came back instantly
Went for a 500wh ride this morning, now charging, will see what happens
Thxs again dnmun and dogman - any idea if this is actually a li ion battery?

 

[dnmun]

appears to be. 13S li ion at full charge is 54.6V

 

[made_in_the_alps_legacy]

OK, I adjusted to 54.6v - charger stopped nicely - at least from the fan point of view
Just the green led which stays off now, any adjustment I could do about this one?
Any suggestion welcome before I put the cover back
Thxs!

 

[made_in_the_alps_legacy]

Rephrasing...
What are the other trimpots for?
What else can be adjusted?

 

[dnmun]

maximum current and current level at point it goes to CV. you do not need to adjust either one.

 

[made_in_the_alps_legacy]

I am "recycling" this topic :

My supplier gives a 2 years warranty on its batteries, the one I got from him is showing "power cuts" even right after a charge.
(Battery specs HERE
Arguing that one of the cells might be damaged and activates the "one cell below 3V" protection by the BMS,
he agreed that I open it up to look for a damaged cell :
He would send me a new cell Under warranty if that is the case.

So... I started my 1st "battery surgery" :




I could measure the voltage of each cells with a FLUKE 87 and found them all in between 4,18 to 4,19V
Then I told myself: "add a load": I connected a 250W resistance and adjusted that resistance to pull 2A (MAX rated was 1.4A on the resistance name plate)

the voltage of each cells in those conditions : all in between 4,17 to 4,19V

I informed the supplier and we "started to agree" that the power cuts must be due to "30A nominal current exceeded" protection.
Then I tried to argue about the kit inconsistencies : a 30A protection while the controller is rated 50A ?
but got no further arguments since under those conditions, the kit is already 50% more powerfull than rated (1500W i.o 1000W)

What to do now ?
I will probably pack it back and try to find a controller + motor which would please this battery... a 500W something... IDK

Any other suggestions ?