Fazua Battery Mystery how do you get 36V from 17 Batteries

[Waynemarlow]

OK, sort of a battery mystery. I have a Fazua battery that looks like its completely flat, 2.2 volts on the output wires. On opening it up it has 2 groups of 6 Samsung 18650 cells and 1 group of 5 built in a cylinder type arrangement of the 3 groups put end for end. The BMS looks as though it is a 10S setup with 10 wires leading back to the PCB board. I was expecting 20 batteries in a 10S2P arrangement to output a standard 36 volt lithium setup. To confuse me even further it would seem there is only 1 interconnection between the groups with a +ve at one and a negative at the other.

Now without stripping it completely out, which is going to mean removing the interconnecting wires, how does this setup work, I can only think that the its in some form of 9S setup with 1 battery as a solo battery ( thats got to be tough on that 1 cell ) that is stepped up to 36 volts. But then the charger is a fairly standard looking 36 volt charger with a fancy Rosenberger plug with only the main 2 wires are connected back to the PCB board.

What I had thought to do was to individually recharge each cell and see if they could be recovered, I suspect this bike has sat for a very long time and the BMS has run the unit completely flat. The battery is fairly complex to strip out as individual units, any risk of putting a very low current through at say 30 volts to see if they all will pick up. Even if they only recover say 50% then it maybe worthwhile as a get me home battery.

Any help on this one would be appreciated.

 

[Hillhater]

What is the pack spec ? Volts, Ah capacity , or even Wh ??
Are you sure they are groups of 6 cells ?
When i group 18650s like that i get 7 cells by putting one in the center “core”.
And if there is just one missing in that last group, it would be 6.
So, 7+7+6 would be 20 cells , 10s, 2p....36v ??

 

[Waynemarlow]

Ah that explains it, I didn't think there was enough room down the centre but on closer inspection, there is a cell in there.

36 volt 7Ah 252 Wh on the pack. I'm presuming Samsung 35E batteries then.

Any views on whether to run a very light charge through the pack via a bench supply to see if they will recover ?

 

[Hillhater]

Have you tried a MMeter on those balance wires ?
The BMS may have isolated the output on safety shutdown,. So test the cells/groups directly.
Or a low charge Maybe worth a try, 0.1 -0.2 A....but don’t hold your breath, the BMS may prevent recharging, requiring a individual charge for each cell group..or the cells may be just dead !

 

[docw009]

This must be the balance connector - 10 wires. The batteries are surely not down to 2.2V. That's the open circuit volatge across the output when the BMS has shut off.

Think of the BMS as controlling a switch between the negative terminal of the cells and the negative pin of your output connector, The BMS will turn off that switch when any of the ten series groups is under 3 volts. The first thing you can do is remove the connector, and probe across each pair of pins in it. You will get 9 of the group voltages.The 10th group is probably between the most negative pin on your connector and the negative end of the battery.

Your voltage results will dictate whether you can safely force a recharge or have to scrap the pack.

 

[Waynemarlow]

Thanks guys.

Sadly the battery cells are down to just over 0.2V, almost totally flat.

OK do we put a bench supply on them and bring them back to life really slowly across each group pack of 7 cells ( quite easy to get to ) or is the pack toast ? What are the risks of trying to charge them slowly ?

Thanks.

 

[Hillhater]

There is little to lose by trying one group at very low charge....carefully monitored of course !
But at that voltage level, there is little chance of success, and even if some do come back to life, it is unlikely they will ever perform reliably/ safely !

 

[docw009]

All the groups are down to .2V? If that was true, I'd make sure they were dead probing the voltage from one cell case to another cell case, so they could be scrapped.

 

[eMark]

Here's one review (3/23/21) of the same Fauza battery pack as yours ...

A 252 wh pack it’s a ridiculously small capacity, no matter how light the ebike is.

With 20% deterioration it will be a 200wh pack actually 160WH usable. Don’t use the last 20% b/c we’ve learned many lessons why not....

So. 200WH USABLE Capacity for a NEW battery, 160WH after 400-500cycles maybe less. I know better not to fall for this gimmick

Suggest you carefully remove all 20 cells and test individual cells to see how many are dead. You may find it's best to discharge all 20 and take to a recycle center.

There are 6 rows of 3 cells end-to-end equals 18 cells. Plus 2 more cells end-to-end (that can seen at the top of photo) equals 20 cells total.

Even when new the usable 35e cell rating is closer to 3200mAh or a 6.4Ah (10S2P) realistic rating for a new Fauza pack. Even if you could revive the cells the pack probably doesn't have more than a 6.0Ah rating at best. Is it worth rebuilding the pack with new 35e Grade A cells costing $150, if there's only a 50/50 chance that the BMS is OK.

If you have some usable salvaged cells you could try rebuilding the pack to determine if BMS is OK before ordering new 35e cells. Think most would agree it's best to discharge and scrap the old 35e cells.

 

[docw009]

I do wonder if I steered the OP wrong with that ribbon cable. There's also a mylar ribbon cble at the far end of the battery.

Usually what I've seen happen on my batteries is that the one or two groups that power the BMS can see a heavier discharge, but the rest of the groups will hang in, slowly discharging art 1-2% per month.

That said, I refuse to revive cells. Seen enough posts from people who done so and had flammable results.

 

[Waynemarlow]

I know people are a bit derisory of these very small capacity batteries but these are designed as an aide to a cyclist, not to power a cyclist. On a 30K off road Emtb ride of about 1000m of climb I'm only using about 300 - 350Wh's which is just outside of one battery. The pain is carrying another full battery in my back pack, which sort of undoes the nicety of having only about a 19Kg bike instead of the 24kg monster truck full fat bike I have.

I bought the battery as a spare to dismantle, mainly to see what and how they are built and if possible to shoe horn in a battery of my own of 10S3P in lieu of the pack or to work out a way to have a small 10S1P pack in a small bottle on the outside paralleling into the existing pack, to give me the 400W'hs Im looking for.

The mylar cable is for the on off switch on the end of the pack.

OK get out the metal can out in the yard and lets see if the individual packs will charge.

Thanks so far for the advice.

 

[docw009]

You can make a 10S-1P cylindrical battery out of 21700 cells. You could get 5AH and 15A peak with these BAK cells. $60 for cells. $50 for a spot welder. $15 for a BMS. Put it inside a plastic water bottle.


https://www.18650batterystore.com/collections/21700-batteries/products/bak-n21700cg-battery

 

[Waynemarlow]

Yes, we have been building packs with Samsung 21700 50E's with great success, they are a super battery cell that seems to perform better than the spec's.

I had originally thought I could get a 21700 10S2P pack inside the motor drive unit but it looks like the BMS on these packs are far more than just a BMS for the battery and do part of the motor control. I'm not sure what is what as there is a 4 wire data leading from the motor connector to the battery. This could be as simple as interregating the battery for monitoring the number of charges etc.

 

[eMark]

Are you sure there aren't 20 cells instead of only 17 cells ?

It looks like there are six rows with each havng 3 cells = 18.
It looks like there is another row at top havng only 2 cells. Altogether 20 cells for a 10S2P battery.

Are you just trying to play a trick on us or could it be possible that you need glasses :wink:

 

[Hillhater]

Are you sure there aren't 20 cells instead of only 17 cells ?

Are you just trying to play a trick on us or could it be possible that you need glasses :wink:

are you sure you have actually read the thread ?

 

[eMark]

are you sure you have actually read the thread ?

FUNNY - Ha Ha ... was going to ask you the same question

Exterior length of his Fauza battery is only 11.6 inches (29.5cm). Do the math ... (six rows of three 35e cells placed end-to-end) ... plus 2 more 35e cells (end-to-end) on the top row is the Fauza 250W 36V 7A rated capacity (10s2p). Room enuf for 7 rows (7th row at top with 2 cells end-to-end). You're possibly thinking of a "7+7+6" much lenthier battery like that of the bottom photo posted below.

Circumference is 7.5cm x 8.0cm(3.15") ... do the math ... Three 35e strings (9 cells) plus one 35e cell in the top row of two 35e cells . The other three 35e strings (9 cells) plus the other 35e cell in the top row completes the Fauza 250W 18650 36V 10s2p battery ...

What is the pack spec ? Volts, Ah capacity , or even Wh ??
Are you sure they are groups of 6 cells ?
When i group 18650s like that i get 7 cells by putting one in the center “core”.
And if there is just one missing in that last group, it would be 6.
So, 7+7+6 would be 20 cells , 10s, 2p....36v ??

There's not enuf length for "7" 18650 li-ion cells end-to-end when the inside length of his 10s2p 250W Fauza isn't even 11 inches. Also due to the roomy inside circumference there is room enuf for six 3-cell strings plus room enuf for two more 35e cells on the top (see his above photo) .

Apparently you mistakenly thought his battery only had room for three rows of cells. Possibly more along the lines like the one shown below allowing enuf length for 7 cells end-to-end plus 3 more end-to-end cells in another row of 6 end-to-end cells ... 7+3=10 and another 7+3=10 (10s2p) ...

Actually even with it's longer length than his shorter Fauza battery there's only enuf length for six 18650 cells end-to-end. Two rows of six and two rows of 4 equals 10S2p (6.4Ah or 7.0Ah). Enuf space for the BMS iafter the two rows with only 4 cells.

 

[Hillhater]

Re read the thread,
Look at the photos,
And think again .!

 

[Waynemarlow]

Thanks,

Politely saying that we established that I had not seen the 2 centre cells and that indeed the configuration is 7-7-6 cells, quite early on.

 

[eMark]

... had not seen the 2 centre cells and that indeed the configuration is 7-7-6 cells.

7-7-6 equals 20 ... but incorrect way of expressing your Fauza 10s2p wiring configuration. The following is one of two possible wiring configurations for your 10s2p Fauza 250W (when new) Battery...

• One Series/Parallel ... String/Group of 10-35e Cells Equals 10s1p
  9-35e cells (3 rows/strings with each having three 35e cells = 9-35e cells + 1 of the top 2 centre 35e cells = 10-35e cells) = 36V-(nominal if all cells in ok condition)

• Second Series/Parallel ... String/Group of 10-35e Cells Equals 10s2p
  9-35e cells (3 rows/strings with each having three 35e cells = 9-35e cells + the other 1) of the 2 centre 35e cells = 10-35e cells) = 36V-(nominal if all cells in ok condition)

You're Fauza 10s2p wired configuration should not be expressed as: 7-7-6 ... instead as: 9-1 plus 9-1 = 10s2p ... OR ... 8-2 plus 8-2 = 10s2p . . . Either way takes into account the two 35e cells in the top row ("2 centre cells") of your Fauza photo ... not as 7-7-6

7-7-6 equals 20 (not 17) ... but doesn't make sense for your Fauza 10s2p wiring run configuration. Neither does this part of your thread title ... "how do you get 36V from 17 Batteries"

 

[Hillhater]

.7-7-6 equals 20 ... but incorrect way of expressing your Fauza 10s2p wiring configuration.

7-7-6, is the pack layout. .
We knew that from post 4, but why did you take so long to catch up ?

 

[eMark]

On opening it up it has 2 groups of 6 Samsung 18650 cells and 1 group of 5 built in a cylinder type arrangement of the 3 groups put end for end. ... I was expecting 20 batteries in a 10S2P arrangement to output a standard 36 volt lithium setup. To confuse me even further it would seem there is only 1 interconnection between the groups with a +ve at one and a negative at the other.

I can only think that the its in some form of 9S setup with 1 battery as a solo battery ( thats got to be tough on that 1 cell ) that is stepped up to 36 volts.

It's plausible the OP's confusing post led to your confusing "7+7+6" configuration reply...

What is the pack spec ? Volts, Ah capacity , or even Wh ??
Are you sure they are groups of 6 cells ?
When i group 18650s like that i get 7 cells by putting one in the center “core”.
And if there is just one missing in that last group, it would be 6.
So, 7+7+6 would be 20 cells , 10s, 2p....36v ??

If you would have taken time to study the OP's photo you would've realized that there are only 3 cells in each of 6 rows and only 2 cells in the top row thus making your "7+7+6" configuraton OP's FAUZA battery. You really need to GO BACK and study the OP's photo to resolve your confusion.

Is it really that hard to admit your "7+7+6" configuration isn't helpful -- rather confusing

Hopefully the following photo(s) will correct any confusion you still have with your wrong 7+7+6 configuration. You're only digging a deeper hole for yourself by insisting the configuration is 7+7+6.

Exterior dimensions of his FAUZA 10s2p 36V 250W are: 29.5cm x 8cm x 7.5cm. Do the math ... 11.61" x 3.15" x 2.95".

The outside circumference dimensions of the 7 rows (see photo below) are approximately: 2.70" x 2.35" that will fit inside of the Op's FAUZA 36V 250W 18650 10S2P battery.

 

[Hillhater]

Buddy,...step away from those fumes,....then go play with your cells again !
Reading the thread again might help you also.!

.When i group 18650s like that i get 7 cells by putting one in the center “core”.
And if there is just one missing in that last group, it would be 6.

And Wayne replied..

I didn't think there was enough room down the centre but on closer inspection, there is a cell in there.
.

 

[Hillhater]

.......
You're Fauza 10s2p wired configuration should not be expressed as: 7-7-6 ... instead as: 9-1 plus 9-1 = 10s2p ... OR ... 8-2 plus 8-2 = 10s2p . . .
......

I copied that for future reference.....
....when i need a good laugh ! :lol:

 

[Hillhater]

Deleted

 

[jbalat]

Hi Wayne Have you made any progress with that pack.. occasionally my pack is going into an error state after charging, if I leave it for a few days it’s good again. I’m guessing a few bad cells are triggering high voltage cutoff and it takes a while for the bms to pull them down again.
So I may need to replace some of the cells.

Also I’ve heard with bosch batteries you need to keep the bms alive since the firmware is written in ram and not eprom, hope this isn’t the case with fazua.

Nice to know that the charger doesn’t do anything special like the extra 5v line on the bosch so hopefully I can make an adapter to use a smaller charger so I can also charge at work.