Purchased Undersized Chargery 100A BMS, but is there a solution to wire in series?

[myles]

Hey Guys, i am still learning GOBS of information, and i'll be making videos when all is said and done so people don't make the same mistakes i do.

#1 DO NOT PURCHASE ANYTHING, until you have a full GRASP of what each product is doing and its purpose!

Can you help me possible solve this one?

I have 3 battery packs that i'll be wiring in a 16s3p configuration. they are 3.2v 280AH cells for Amy. Matched.

I bought 4 Chargery BMS (with the intent of possibly adding a 4th pack of cells, i have 68 cells total purchased. But i made the mistake and bought the 100A version, when in hind sight i should have bought the 300A minimum for my application, since this will be powering a complete house overnight, sometimes with A/C minisplit running etc.

IS there a way to wire bms in series so that i can make 3 bms into a 300 amp? I talked to jason at chargery and its not as simple as just changing shunts, the 100a, 300a, 600a are all different internally as well.

If i have to purchase a new BMS, that is understandable, and i wouldn't be opposed to that because the more i read and use the chargery, the less I enjoy it, although it does work totally fine, i am only using it right now for top balancing to get used to it. these packs are not in service yet.

 

[sunshine_eggo]

In most cases, each BMS is capable of 100A, so your 3 batteries in parallel can do 100A each for a theoretical 300A. I say theoretical because you likely won't have perfectly balanced load sharing between the 3 batteries. I would hope 14kW of power is enough to meet your loads.

It's not clear to me which Chargery you have or how it's able to protect the battery. Do you have a set of relays for each battery?

 

[myles]

In most cases, each BMS is capable of 100A, so your 3 batteries in parallel can do 100A each for a theoretical 300A. I say theoretical because you likely won't have perfectly balanced load sharing between the 3 batteries. I would hope 14kW of power is enough to meet your loads.

It's not clear to me which Chargery you have or how it's able to protect the battery. Do you have a set of relays for each battery?

Yes so i will draw out a little diagram of my setup here:

 

[Steve_S]

3 Battery Packs in Parallel with 100A BMS should deliver a total of 300A as it is divided equally if properly wired.
This would also "technically" allow for 300A Charge to the Bank of battery, again being split between packs. 100A into a 280AH pack is still well within specs.
Depending on Relays/Contactors or if using a DCC that could be a limiter as well. The DCC will do as it should but if using say TE/Kilovac or ElectroMechanical relays it would be better to use 150A for such.
Chargery's Come in different amperages from 100A to 600A which applied to the BMS T & new P series models.

I built all of my production packs with BMS8T-300's with DCC-300's. I have only ever pushed them to 250A each during my Thrash testing process (they didn't blink at all btw). As the bank was 4 packs until just now none of them packs see an actual "heavy load" and don't go over 75A (per pack) unless I'm doing something "odd".

I am now in process of final change and converting all of my production & utility to JKBMS 150A with 2A Active balancer & RS485/CanBus to normalize everything and have the same communications interfaces and needed active balancing etc.

280AH pack can only deliver a max of 280A excluding burst discharge.

I will be posting a large list of new & used stuff BMS' and lots more when I am complete with the final system build.

 

[sunshine_eggo]

Yes so i will draw out a little diagram of my setup here:

Yep. That's a 300A setup. 100A per battery.

 

[myles]

Thank you so much for the help and confirmation guys. I don't need to purchase new BMS thankfully. I have another backup battery bank, same exact setup, i so i could have 4 total banks of batteries for a total of 400 Amps if needed.

appreciate the feedback!

 

[sunshine_eggo]

300A is theoretical.

As mentioned above, the sum of the 3 is 100A, but the likelihood that they'll all pass the exact same amount of current is low. They should be close. To be conservative, assume 10% isn't available, so 270A.

Once deployed confirm current flow through each battery with a DC clamp ammeter under heavy load and you can estimate your max amps as follows:

A1 is the highest current passing through any battery, A2 and A3 are the currents for the other batteries.

Max = (A1 + A2 + A3) * 100/A1

Example:

A1 = 60A
A2 = 58A
A3 = 55A

Max = (60+58+55) * 100/60 = 288A

 

[Steve_S]

Exactly, it is never as "Neat N Tidy" as it is in theory. because I'm sub-zero and have a heated powerhouse, the batteries being at a different height have a 1C Temp difference between each pack and that DOES affect the Charge & Discharge rates as well... I'm not kidding ! It surprised me too when I first saw this consistently, and same in summer but less so. That is something I am addressing with the reconfig of the powerhouse & packs.

 

[myles]

Exactly, it is never as "Neat N Tidy" as it is in theory. because I'm sub-zero and have a heated powerhouse, the batteries being at a different height have a 1C Temp difference between each pack and that DOES affect the Charge & Discharge rates as well... I'm not kidding ! It surprised me too when I first saw this consistently, and same in summer but less so. That is something I am addressing with the reconfig of the powerhouse & packs.

This is interesting! who would have thought they would be so sensitive, my guess is more sensitive the colder the temperature. I am going to keep my batteries in a heated environment as well within my building envelope, with many safety features should there be a failure of sorts.

 

[Bob B]

Hey Guys, i am still learning GOBS of information, and i'll be making videos when all is said and done so people don't make the same mistakes i do.

#1 DO NOT PURCHASE ANYTHING, until you have a full GRASP of what each product is doing and its purpose!

Can you help me possible solve this one?

I have 3 battery packs that i'll be wiring in a 16s3p configuration. they are 3.2v 280AH cells for Amy. Matched.

I bought 4 Chargery BMS (with the intent of possibly adding a 4th pack of cells, i have 68 cells total purchased. But i made the mistake and bought the 100A version, when in hind sight i should have bought the 300A minimum for my application, since this will be powering a complete house overnight, sometimes with A/C minisplit running etc.

IS there a way to wire bms in series so that i can make 3 bms into a 300 amp? I talked to jason at chargery and its not as simple as just changing shunts, the 100a, 300a, 600a are all different internally as well.

If i have to purchase a new BMS, that is understandable, and i wouldn't be opposed to that because the more i read and use the chargery, the less I enjoy it, although it does work totally fine, i am only using it right now for top balancing to get used to it. these packs are not in service yet.

The other guys have given you good advice .... but thought I'd add a tidbit.
You seem to have series and parallel concepts mixed up .... In parallel, the current adds but the voltage remains the same .... in series, the voltage adds but current remains the same.

It's an important concept to understand ... You've probably got it by now, but it might be worth some further study if not.

48V at 300 amps is a huge amount of power (14.4 KW) ... but I will trust that you have figured out that requirement.

 

[myles]

The other guys have given you good advice .... but thought I'd add a tidbit.
You seem to have series and parallel concepts mixed up .... In parallel, the current adds but the voltage remains the same .... in series, the voltage adds but current remains the same.

It's an important concept to understand ... You've probably got it by now, but it might be worth some further study if not.

48V at 300 amps is a huge amount of power (14.4 KW) ... but I will trust that you have figured out that requirement.

Thank you bob! It can never be re-iterated enough! We are dealing with large power loads for sure! It is powering an entire house, albeit all my heating demands are NOT electric, so the main electric draw will be a 48k btu four zone mini split in summer, which the solar panels should mainly take care of, as when the sun goes down A/C is alot less necessary, however the stipulation to going off grid was that my wife cannot know the difference between grid and no grid, so i am having an abundance of power for them, but they will also need to learn the art of shutting stuff off, and shutting lights off. Trying to teach our 3 little girls about good stewardship including gardening, and living off the land a bit!