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Discussion Starter #1
Hi all, I'm building an EV project right now and I'm using (6) of the LG Chem A7 battery modules. I was planning on running them in a 3P2S configuration as I was informed that they can't be run in anything more than 2S and even that is "pushing it".

Each module is a 16S pack and I'm unsure what I need to charge them collectively or even individually. Right now they're just sitting on my work bench because I'm wanting to top and bottom balance each pack prior to installing.

Can anyone provide me with some info about what equipment I need and any pertinent information about charging these batteries properly?

Thanks in advance.
 

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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.
 

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Discussion Starter #3
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?
 

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Discussion Starter #4
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
 

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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.
 

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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.
 

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Discussion Starter #7
That's very helpful insight. I'm located in the Alabama Gulf Coast and I'm really struggling to find local experts I can bounce ideas off here. I am worried I'm going to need to just ship everything to EVwest and wait several months and write them a giant check to finish this project.

I really jumped in before knowing exactly what I was doing. I saw the batteries as a great deal and jumped on it and now I'm trying to design a system around them and it may be better to cut my losses now and start over OR temper my expectations and work with what I have.

If you would be willing to chat on the phone sometime you could PM me your contact info and we could probably come up with a solution fairly quickly.

Thanks for your help
 

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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.
 

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You can certainly run them more than 2 in series. What matters is what they are connected to. Those batteries have a peak voltage of ~65 volts (4.2 x 16). Of course, you can set your BMS to have a lower max voltage to extend your battery life. So say you charge them to a max of 60 volts, you can put 3 in series as long as your motor/controller can handle 180 volts, etc.

By any chance, do you know what the rated peak discharge of those batteries is? Thanks and have fun. gw
 

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Discussion Starter #10
You can certainly run them more than 2 in series. What matters is what they are connected to. Those batteries have a peak voltage of ~65 volts (4.2 x 16). Of course, you can set your BMS to have a lower max voltage to extend your battery life. So say you charge them to a max of 60 volts, you can put 3 in series as long as your motor/controller can handle 180 volts, etc.

By any chance, do you know what the rated peak discharge of those batteries is? Thanks and have fun. gw
I may have misspoken earlier. I was told the LG modules could ONLY be connected in series, not parallel. I could easily run them as 360v+ but not 60v @ 270Ah.

I believe the way I'm going to try to wire this up will be (2) groups of 3 modules in series (48cells)
 

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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.
 

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Discussion Starter #12
That's great info. Just for clarification, it wasn't EV west who told me they couldn't be run parallel, only that's how they recommend it. That email is from another installer/builder.

I think I understand what you're saying now. I'm perfectly fine with buying a second BMS if it means I'm able to ensure the cells will stay in top shape and I can use all 17kwh I've purchased.

If each module contains 16cells and I'd have (3) modules connected in series I would need a BMS capable of charging 48cells at a time. Is that correct? Then I'd need two of those and I'd need a charger that could power both BMS' at the same time (ideally).

Can you suggest the appropriate BMS and Charger I would need to pull this off? My goal is to have a system I can just plug in like my regular Cmax and have it charge the batteries fully, appropriately and quickly. I'm trying to avoid charging one bank and then going out and charging up the second bank after the first is finished.
 

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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.
 

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Let's back up a step. You have six batteries and are asking which way they should be configured - cart before the horse.

Normally you (overly simplified):
i) pick the car you wish to convert conscious of its weight, drag, etc.
ii) pick the motor(s) and controller(s) you wish to use to provide the desired performance using one of the available performance models;
iii) choose a series of modules and cells necessary to produce the input voltage required to drive the controller
iv) choose the number of modules or cells necessary to produce the driving range (kWh) and/or the performance (peak current) you want.

gw
 

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Discussion Starter #15
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?
 

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Discussion Starter #16 (Edited)
Let's back up a step. You have six batteries and are asking which way they should be configured - cart before the horse.

Normally you (overly simplified):
i) pick the car you wish to convert conscious of its weight, drag, etc.
ii) pick the motor(s) and controller(s) you wish to use to provide the desired performance using one of the available performance models;
iii) choose a series of modules and cells necessary to produce the input voltage required to drive the controller
iv) choose the number of modules or cells necessary to produce the driving range (kWh) and/or the performance (peak current) you want.

gw
1. I already have the vehicle.

2. It was already an electric vehicle with a 72v DC motor. My plan was to replace the 72v DC motor with a stronger, "48v AC motor" (HPEVS AC-35)

3. The 60v LG batteries I purchased were just going to be run all in parallel for a 60v 270Ah pack which would've been far more powerful, provided double the range and increased the top speed.

4. I didn't do this. I only looked at the voltage of each module and the overall capacity to determine range. Although I should say I was GOING to purchase Smart fortwo modules from EVwest but they had a much lower rated continuous output. Michael from EVW told me that these LG modules would be capable of 800Ah where-as the Smart modules were only good for 100Ah (200Ah peak). At this point I decided that the LG modules were the ones I wanted to use. Admittedly I may not have had all of the information or wiring knowledge prior to buying them.


This vehicle I'm building is just a play thing. I'd like to take it to shows, do some burnouts and maybe tool around to the shops in it with my son. I'd really like to be able to make a profit on it when I decide to sell it on but that's not paramount. I'd just like to have some fun and turn some heads.

I'm confident that no matter what motor/controller I end up being forced to use I'm going to make a ton more power and range than I would if I just restored it to stock. If I'm able to run a 168tq Hyper9 or a 110tq AC-35, it's going to be a lot more fun than the standard 12hp DC motor I'm taking out.

also, this vehicle has a manual transmission and a Dana 44 rear end so I'm able to add limited slip and any rear end size I want to adjust for either top speed or acceleration.
 

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If you use the standard voltage Hyper 9, you can put 2 LG Chem modules in series. The High Voltage version won't do you much good since 2 modules in series gives you about 130 volts which is too low for the HV version. 3 modules in series gives you over 180 volts which is too high for the HV version. Good luck with your project. gw
 

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Discussion Starter #18
If you use the standard voltage Hyper 9, you can put 2 LG Chem modules in series. The High Voltage version won't do you much good since 2 modules in series gives you about 130 volts which is too low for the HV version. 3 modules in series gives you over 180 volts which is too high for the HV version. Good luck with your project. gw

You're suggesting I order the 120v Hyper9 kit and just run (3) sets of 2S modules? It would require me to buy 3 BMS' and the power is slightly less but if this reduces complexity in the system then I'm all for it.

I have a feeling,. from what we've been discussing here, that I'm going to have to take apart the LG modules and have the BMS' wired directly to each cell. One of the most attractive things about these modules was how tidy the packs were and easy to package. I hope the addition of the BMS' doesn't impact this too much.


Also, of the 6 modules I have (4) are at 60v+ and (2) are at 55v+. I was hoping to somehow condition them (bottom/top balancing) prior to using them. I've heard others mention they need to be used in the vehicle first and THEN balanced. Any opinions on this or what I would need to accomplish it?
 

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The standard Hyper 9 motor is good quality and produces much more power for the money then the HP-50. The reason EV West carries them is they provide very good power/$. I use 2 of them for a cobra kit car I've made and we are using 2 of the HV type for a conversion of a 1950 Chevy Pickup. Given the batteries you have, I'd run them 2S3P. That will fully power the motor and give you 75 miles of range or more depending upon how light your car is.

DO NOT open up the batteries. The plastic cases are factory welded shut. Those batteries have a voltage tap for each cell. Those batteries have a socket for 16 voltage taps and 4 thermister taps. The pin-outs are listed on the EV West site. If you need to get the matching plug, Thunderstruck should be able to provide you with the plugs and crimps, especially if you use their BMS. I would ask John at Thunderstruck for the best topology to wire their BMS to you 2 modules in series, 3 in parallel.

gw
 
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