[frodus]

One thing confusing when you say 3p2s is you're talking modules, not cells. We normally discuss XsYp when talking cells, not modules. People do it a lot with Leaf cells and it's confusing.

So it looks like you want to build two 48s packs and parallel them. Correct?

If you want to balance, you'll need either a BMS that can do it, or hand balance the cells, which is a huge PITA. I'd look into Zeva BMS a little, as they're priced well and modular. They're 12s, but you can make harnesses so you'd use 4 boards for your 48s pack.

For charging, you want to charge just a single 16s pack temporarily? or do you want to charge the entire 48s pack? I suggest buying a charger that meets the final need, not the immediate desire.

If they're resting at a good voltage, don't worry about balancing until you're ready to install in vehicle, and charge/balance then. You don't want to fully charge them and let them sit for long periods. We recommend having maybe 50-60% SOC for storage. Charging to 100% and leaving sitting is not recommended by many battery manufacturers or OEMs.

 

[frodus]

Sorry, one more thing I need to clarify. The A7 modules are composed of (16) cells in series. When I say "3S2P" I'm talking about how I would connect the modules together once they're in the van

Thanks for clarifying. It's difficult with so many modules out there for people to memorize what each of them are. 3s2p looks like 3 cells in series, 2 cells in parallel, as that's the industry norm. There isn't really a clear way to state module configuration, other than just saying "3 modules of 16s in series for 48s and 2 of those packs in parallel.

So if possible, I'd avoid using s and p for discussing modules.

 

[frodus]

Travis, thanks for the response. I think I'm just muddying the waters because I'm not 100% sure what I'm doing right now.

My initial plan was to run the biggest/strongest 48v AC motor I could get away with and then run all of these battery modules as just a 6P configuration, so basically 60.5v @ 270Ah. I was told by a few people (who know more than I do) that these modules have issues running in parallel and I should consider going the other way with it and running it as a 320v+ @ 45Ah instead. It was mentioned that they shouldn't be run more than 2P. I'm guessing for logistical reasons.

My initial plan was to run the HPEVS AC-35 as it would be able to provide about 100+tq which is plenty for my build but if I can't run the batteries in a xP configuration then I'd have no usable range.

A tesla motor/gear drive will not work in my application without serious modification and I'm not interested in going that route. Currently the van has a DC motor in it (set up for 72v) but I figured a newer/better AC motor @ 60v would still be a vast improvement.


If I'm mistaken and the harnesses I got with these units aren't used for an internal BMS then I should be ok to run them in either a 6P or 3S2P configuration, right?? At that point it seems it would just come down to which motor I'd want to use. Am i overlooking something else?

60V and lower is good for golf carts or small, slow motorcycles. Not so much for a car. I'd suggest aiming for 72-120VDC, and run either a series wound motor and controller, or an HPEVS system like AC35. They have units that can go to 144VDC, or if you want lower, use something like 96V (2 modules in series for ~96V nominal and about 130V fully charged).

Concerning BMS, if you want to use a BMS, you will likely require a BMS for each parallel pack.

For example, if you try to put 2 modules in parallel at their main lugs, and try to tie all the balance wires together so the cells are essentially in parallel, it will likely result in some overheating/damage of the balance wires. When you charge, or discharge, the cells will naturally share current across those balance wires. Cells have different internal resistance and share current unequally, so each cell may discharge some into a paralleled cell. Balance wires are very small compared to the high current connections and will overheat. I've seen them fry before.

For this reason, you'd want to put the batteries in series first to get your voltage required, and then have multiple parallel battery packs. Unfortunately, this would also require you to have 2x the BMS. If you have a 48s setup (2 parallel packs of 3 modules in series), you'd need 8 12s balance boards of Zeva BMS, or two Orion BMS 48s BMS. Because of the balance wire issue above (low current wires between parallel groups), you can't use just one single 48s solution. You treat the packs as if they're independent. Zeva and Elithion can do parallel packs. I don't think the Orion can.

These batteries are great, but you do need to think out the system somewhat.

 

[frodus]

I'd rather discuss here, then it's useful for the next person You know what I mean?

What vehicle is this going into? What are your design constraints (Range, top speed, etc)?

I think they're good strong batteries that are great for an EV. I wouldn't start over at all. You just need to know some of the aforementioned design constraints before you move forward.

You really should look more at your drive train (motor/controller). IMHO, 60V is way too low. 400V is likely too high ($$$).

We know you have 6 modules to mess with?

1) You can go 96s (6 modules in series) for about 400V fully charged, but you're in a different power level than most easily purchased controllers and motors.

2) You can go 48s (3 modules in series, 2 packs in parallel) for ~200V fully charged, and you're pretty much the same place as above. If you use Zeva BMS, you'd need 4 modules per series pack, so 8 total.

3) You can go 32s (2 modules in series, 3 packs in parallel) for ~130V fully charged, and now you can use some of the HPEVS or Netgain equipment. For HPEVS, there's the 144V controller and the 96V controller. The 144V will work well. The 96V controller works up to 130VDC, so just undercharge slightly and you should be close to the cutoff. The Netgain 144V should work. If you use Zeva BMS, you'd need 3 modules per series pack, so 9 total.

4) You could go 16s, but you're going to have a golf cart, with underwhelming speed.

So I'd say stick to #3 above unless you want to put some $$$ into the project. The cost goes up and choices go down for #1 and 2.

 

[frodus]

You can parallel them, but I'm not sure you are understanding.

You wrote what EVWest said here:
https://www.diyelectriccar.com/forums/showpost.php?p=1037695&postcount=16

"Hi Matt,

Can’t dive in right this minute but I quickly scanned your email.

Sadly we don’t endorse putting those modules in parallel. Life would be SO much cooler (and cheaper and lighter) if we did, but because the BMS cannot see and control all it needs to when cells are in this configuration, it’s just not recommended without a lot of expensive mods and design time. We’ve been down this road a few times and always conclude to not do it. You might have seen others do it for short term races or whatev, but I know of no long term builds that attempted this.

Plus you mention building reliably for the next owner, so there’s another reason.

If you want to stick with these modules, I’d recommend using them in series with a high voltage motor. Unfortunately that rules out HPEVS and Netgain’s Hyper9 unless you use like only 2-3 LG modules.

This is kind of major, so wanted to let you know asap."

He is right, You cannot parallel them without having a more complex design. You need a BMS per parallel string. That doubles the cost if you parallel 2 packs. It Triples if you parallel 3 packs, etc.

They are NOT saying you can't parallel, they're saying there are caveats. They are saying you can create multiple "battery packs" and parallel them, as long as each parallel string has its own BMS and control.

Cells like from the Leaf, have high current connections for each cell, that you can parallel each cell group easily. The LG cells do not, and you CANNOT use the BMS wires to parallel the packs for balance purposes, as they'll use those connections to share current. It will likely cause the balance wires to overheat and you risk fire.

 

[frodus]

Please draw out your proposed system. Label everything, include your proposed connections.

It's likely the builder you reference doesn't want to mess with it or have to painstakingly support it, due to the extra wiring and work.

Slight correction: BMS doesn't charge the cells, it manages and balances them. The charger does the charging. You would only need a single charger to charge all packs that are wired in parallel. I'd highly recommend going to a BMS manufacturer website and reading some manuals to get familiar. We aren't going to want to explain in detail how a BMS works and functions.

One that I know does parallel packs is Zeva BMS. Since the BMS comes in 12s modules, and you have 48s, you'd need 4 of those per 48s string of cells. If you have 2 strings in parallel, then you'd need 8 12s modules and a master BMS controller and LCD. 3 parallel strings would be 12 12s modules.

Elcon charger is one that people like to use, but anything that does 48s is going to be fine.

Remember 48s, and 4.2V a cell (max) is ~200VDC, so ensure your motor/controller will handle that. If you choose 32s, you'd need 3 12s modules (you'd leave 4 unpopulated), and you'd need a charger and controller that handles ~135VDC.

 

[frodus]

Thanks again for the prompt replies. Admittedly I'm in a bit over my head so I appreciate the constructive feedback. I will work on a simple drawing tonight that lays out what I'm attempting to do and how I have it planned in my head.

To comment on your last topic about the controller needing to handle 200V+ : https://www.evwest.com/catalog/product_info.php?products_id=482&osCsid=0td1go2hqvsm45hr94ue5t33c0 This is what I was planning to purchase. I may be mistaken but I was under the impression the controller could see more volts than it's rated for but not use them all. This way I could feed 200v+ to the controller but it would only output the 180v the motor can use.

I was also told by the owner of HPEVS that motors don't "see" voltage, only amperage and that's regulated by the controller...so the controller feeds amps to the motor and the motor is then being "run at a specific voltage".

Is this accurate?

That's if the controller can handle over 200VDC, which it will not. Absolute max for the 144V X1 controller they use on the Netgain is about 180VDC.

See if the place you got the batteries will take them back, unused. It sounds like you may still be far off from needing batteries and it may not be a great design voltage for 2 of those modules in series, 3 strings.

The LG modules have cell voltage taps and temp sensor taps you can use, you don't need to take them apart to attach a BMS. It seems like you may not fully understand what a BMS is, and how it works and how it is connected. Take a look at Zeva BMS manuals or Orion BMS manuals to see how they do it.

You needed to do way more research before you started purchasing items. You're not in over your head, you just haven't gotten your "design" to a point you were ready to purchase. It needs refinement.