Nissan Leaf set up for noob

Hi e-gurus,

I just received a 6 modules Nissan Leaf battery pack that I intend to use exactly as it is ( i.e. 6 2s2p modules in series to make a 48v 60 ah battery - I don't even know how many s and p it makes ).

I have 2 questions in mind :

- I am a bit lost regarding charging this. I was thinking of charging each module separately ( 7.6v 60 ah) but am unable to find a charger handling this, so should I use bulk charging ?

- I am trying to have the lightest set-up possible (trial motorcycle) and so try to avoid BMS at least on the bike, but is this mandatory for controller with regen function, I guess yes but am not sure.

Thanks for your tips !

Xavier

Hi, it looks like if you want to up the voltage to 48V you'll need to put the 6 modules in series (7.6V x 6 = 45.6 V) so you'd have an equivalent 12S2P pack.
Now, I don't know the specs of the Leaf cells, but if you say you want 48V 60Ah, this would mean each cell is 30Ah? Then the 2P would make for a total of 60Ah

About the rest of the questions, my 2 cents:
*recovery without BMS - risky business as you could overchange the battery; in practice it's very unlikely if the battery isn't close to 100% SOC (full) as regen doesn't amount to much, but if by any chance you're close to full battery and regen, without the BMS cutting power you'd overcharge.
*for charging you can do it however you want, all the pack or per module, just be sure the cutoff voltage of the charger really does correspond to your pack. What I mean is if the Leaf chemistry allows dunno, 3.85Vmax, and you have 12S2P pack, then the cutoff voltage must be 3.85x12=46.2V, not 48. Then you have the problem of balancing - I advice you charge at least every so often with a BMS to balance the pack.

Each cell is 3,8 V nominal 33 ah, and a module is 7,6 V 60 ah in a 2s2p configuration with a voltage sensor inclused for the whole module (not cell by cell). So I guess I have to find a BMS I can program to handle these specs and balance the modules and not the cells themselves , Any idea ?

Maximum voltage is 8,4 v per module, so 50,4 v for the whole battery, if I am not wrong, i need to find a 60amp (Max) charger that I can program to cut off at 50,4v, but d'ores it even exist ?

i use a set of four D131 BMSs on my battery pack. 2 on my 21S 44Ah lipo pack as master/slave and 2 on my 24S 87Ah lifepo4 pack with one of them used to charge from the drains of the lipo BMS so it does not lose charge control when charged in a parallel set up with my lifepo4 pack. i have to use diodes in the drains of the lifepo4 BMS to prevent the lipo pack from overcharging one channel on the lifepo4 pack by accident when removed from the charger at full voltage.

but i have already gone through battery exercises which would have ruined a pack without the protection of the BMSs.

the only time i melted a 10AWG wire and overcharged my lifepo4 pack at 400A was when i deliberately bypassed the BMS.

There are already a couple of threads on ES about these packs and many are charging with RC chargers and discharging without a bms. These packs are so dense there is probably no need to discharge them to lvc. If you don't use a bms I would recommend a wiring harness like an rc charger uses and a cell log cell meter so you can monitor individual cell voltage. :?

yep, that was what dogman talked me into thinking too. i keep a cellog on each battery, on the group of channels with the one i know will alarm first. i try to avoid discharging to the point that the LVC cuts in, but LVC is old hat now with people who use batteries so it is nothing new.

when my battery cuts out for LVC, i know i made a mistake and stop to find it. but i am still in, now i guess through, the break in phase on this battery pack. learning how to use it. how long to turn on the charger before i go somewhere so it is charged when i go. usually it just sits on the float charge of the SLA pack which is on 24/7/365. but the SLA charger does push all the lipo and lifepo4 up to the 84.3V or so it uses to fully charge the SLA. so i finish the lipo/lifepo4 charge with a 600W kingpan on 240V too.

How old are the batteries you got?

From my experience, even after roughly 150 cycles on a used nissan leaf pack, the cell voltage stay very balanced if you don't bring them below 3.7V per cell. Again read my post on these packs.

Personally I would leave the BMS out of this. Sure it makes charging and discharging safer... maybe and simpler, but IMO, it's more money and you can do without it. Like dogman said, monitor individual cell voltage during rides if you are really paranoid.

These cells are pretty hard to catch fire. So I do not monitor the individual cells during rides. I just balance charge them every time I charge. I make sure I don't go below 88.8V idling for my 24s pack during rides.

As for the 60Ah, expect to use only 50Ah because these packs are really 25Ah if you draw 1-2C from them. One final note, these cells are large so hopefully you know how big these cells are.

Thanks for your answers !

mvly said:

How old are the batteries you got?

Click to expand...

These are new cells, supposed to be unused ( By the way : Any precautions to be taken with new packs ?), and they are particularly well suited for my use, as I needed Big capacity on a motorbike conversion.

I read the previous thread where you've shown your setup and I saw you're using a hyperion rc charger. If I use a 2000w rc charger will it be able to charge each module individually as I won't separate the cells ?

Xpongebob said:

Thanks for your answers !

mvly said:

How old are the batteries you got?

Click to expand...

These are new cells, supposed to be unused ( By the way : Any precautions to be taken with new packs ?), and they are particularly well suited for my use, as I needed Big capacity on a motorbike conversion.

I read the previous thread where you've shown your setup and I saw you're using a hyperion rc charger. If I use a 2000w rc charger will it be able to charge each module individually as I won't separate the cells ?

Click to expand...

Yes you can charge the cells individually. Though I would check each pair of cells to begin with. They are in 2s2p so check if indeed they are like 3.9V from one end of terminal to the middle contact and from the middle to the high side. Point is, it should be very balanced. They should be similar or the same. For charging each pack, I would pick a voltage and set your RC charger to charge up to the desired voltage. So charge as 2s pack. Or 1s and do it for the other terminals. Just don't try to charge 2000W into these, they don't like fast charging. I would charge at max 0.5C so if you keep them in parallel, that would be 30A. Or 15A if you separate them into individual cells.

The screw ports should be used to charge these if you don't disassemble the pack.

Thanks mvly, that´s precise !

Just ordered a powerful rc charger, as a full noob , I had nothing decent for charging, and didn't want to buy a too specialised charger.

Get a powerful charger with a reasonably conservative 50.0V cutoff (4.17V/cell). Get a couple of multi-cell monitors with low voltage alarms, just a few buck ea from HK. Get an RC charger to use in case a cell or two get out of whack. As long as you stay away from deep discharges that battery chemistry is known to maintain really good cell balance. They also sag a lot more as the voltage gets somewhat low, so if you pay attention it's not hard to be a human BMS.

Those batteries, even in the module cans, require compression for full capacity and longer life, so make sure your mounting plan includes a way to compress them. Icecube demonstrated the increase cell capacity under compression. An example of how much they are compressed is my stack of 5 modules compressed by only gravity that is 18cm tall, 3.6cm each. My rack of 24 modules in the Nissan rack under factory compression is 81.5cm, 3.4cm per module. .2cm doesn't seem like much until you consider that the rack compresses the string of modules by about 1.9" in total.

Thx John, I thought these weren't compresses in the Leaf setup. I think I'll make compression plates part of the battery box structure as stiffeners. I should begin designing it tomorrow.