JK vs Overkill bms?

Setting up a 48V 16s2p system. Wanting to do a 200A bms on the system to handle the 6500 watt inverter. I'll never push anything near that, but better to have incase I need later rather then need and not have. Just looking for the basic safety features, low temp cut off, high amp/voltage/low voltage, BT, and anything else you guys would think would be good to have. I trust everyone here and their opinions, everyone has been extremely helpful.

Wills old video shows overkill as the bms he recommends and I can't find any newer videos on a setup, but the forum seems to recommend JK as the go to now.

Are either of these available for US shipping as id need in the next couple weeks and couldn't wait the 2-3 month shipping time of AliExpress.

Also if there's a video of will with the JK bms id greatly appreciate that so I can see the setup!

MrPsychedelic said:

16s2p

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This would require two BMS's.
I'm a big JK fan.
18650batterystore , used to carry them. Which was great, because they were at my door in two days.
But they have been out of stock for very long. I'm thinking that they may have decided to not carry them anymore.
I personally don't know if anyone else in the states have them.

https://bmsbatteries.com/ seems to have them. I ordered a cheap Daly BMS from them and it arrived quickly.

Docan have USA stock I believe

timselectric said:

This would require two BMS's.
I'm a big JK fan.
18650batterystore , used to carry them. Which was great, because they were at my door in two days.
But they have been out of stock for very long. I'm thinking that they may have decided to not carry them anymore.
I personally don't know if anyone else in the states have them.

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I saw they use to carry them, I just picked up the cells from them and was really hoping they'd get back in stock but never did.

Alan showed bmsbatterystore carries and docan but I'm not sure on how reliable the sites are I'll have to look into it.

Do you just use Alibaba now? And for needing 2 bms for mine does that mean I need (2) 200A or (2) 100A? I'm not sure if they double like the batteries, I assume no but want to be sure.

It looks like JK has a bunch of BMS also, how do you figure out which one to even get?

All of mine have now come from AliExpress.

I use the 200a BMS. And yes, the amperage adds up in parallel.

I use the B2A20S20P

2A = 2 amp active balancing
20S = up to 20 cells in series
20P = 200 amp

I would second getting two BMS, one for each string, even if you get two 200a, the added cost isn’t that much in the grand scheme of things.

timselectric said:

All of mine have now come from AliExpress.

I use the 200a BMS. And yes, the amperage adds up in parallel.

I use the B2A20S20P

2A = 2 amp active balancing
20S = up to 20 cells in series
20P = 200 amp

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How do you know what vendor to trust on AliExpress?

So with the amperage adding up does that mean the wiring needs to be rated for 400Amps since that's what the BMS will be rated for? There's no way I want to push that kind of power lol. That would be insane lol

Does that connect straight to the JK app also? And I think I will order the same one as you, I just want to verify about the BMS amps doubling first lol

740GLE said:

I would second getting two BMS, one for each string, even if you get two 200a, the added cost isn’t that much in the grand scheme of things.

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Ill definitely get 2 bms after the suggestions about it. I just have to find which vendor to trust from AliExpress, gonna do a little bit of research into that

MrPsychedelic said:

How do you know what vendor to trust on AliExpress?

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I usually go with recommendations from people that I trust.
But when I have taken risks, it's not been a problem.
I can't recommend anyone right now, as the stores that I have used are out of stock.

MrPsychedelic said:

So with the amperage adding up does that mean the wiring needs to be rated for 400Amps since that's what the BMS will be rated for? There's no way I want to push that kind of power lol. That would be insane lol

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It does add up, but don't put it all on one conductor.
The batteries positive should connect to a busbar and then to the loads.
Only the busbar will see all of the current used.
Same goes for the negative, with either a busbar or shunt.

MrPsychedelic said:

Does that connect straight to the JK app also? And I think I will order the same one as you, I just want to verify about the BMS amps doubling first lol

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Yes

To add on to Tim. Don't buy the cheap Amazon bus bars. Stick with Pike, Victron or something reputable. You don't need a fire waiting to happen!

Partimewages said:

To add on to Tim. Don't buy the cheap Amazon bus bars. Stick with Pike, Victron or something reputable. You don't need a fire waiting to happen!

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You can get Pike on Amazon if you want to stick with Amazon, just FYI.

I bought Signature Solar 600A 12 lug busbars. That may be overkill for you, but I wanted the space to expand my battery bank or stack another inverter. Not as pretty as something like Pike, but they're going in a box anyway, and they cost less too.

I did the cheap Amazon bus bar route first. Brass. Oops. I'll hang onto them for something. Meaning, they'll probably sit in a box for years before I throw them away.

Just to throw my $0.02 in here:

Overkill is a rebranded/certified JBD
I have about a dozen JBD units in service that run flawlessly
I have 2 JK's that made great range targets after they both died in critical applications

Doing 2 batteries instead of a 2p16s gives you redundancy for the low price of a single BMS which are pretty cheap in the long run. You can take one out of service for repair and still have the lights on to see by.

I've had nothing but great service from Docan, it's where I buy most of my cells from. No worries with them.

Rednecktek said:

Just to throw my $0.02 in here:

Overkill is a rebranded/certified JBD
I have about a dozen JBD units in service that run flawlessly
I have 2 JK's that made great range targets after they both died in critical applications

Doing 2 batteries instead of a 2p16s gives you redundancy for the low price of a single BMS which are pretty cheap in the long run. You can take one out of service for repair and still have the lights on to see by.

I've had nothing but great service from Docan, it's where I buy most of my cells from. No worries with them.

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Would love to have an Overkill BMS, primarily for their stellar warranty! But they top out at the 100A. My JK’s are 200A. But I’ve fried a couple one am in discussion with JK about one that I’m pretty sure is bad.

Anyone know anything about their new BMS being designed in America?

wsaharem said:

Would love to have an Overkill BMS, primarily for their stellar warranty! But they top out at the 100A. My JK’s are 200A. But I’ve fried a couple one am in discussion with JK about one that I’m pretty sure is bad.

Anyone know anything about their new BMS being designed in America?

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I'm a little confused on if I run 2 100A BMS would that make them each run at 200A? I wanted to install the batteries as a snake, going 16s2p but I'm confused how I could run 2 bms doing it that way also?

I'm trying to find some videos on it but there doesn't seem to be much info out there for it. Or I'm having trouble finding it

MrPsychedelic said:

I'm a little confused on if I run 2 100A BMS would that make them each run at 200A?

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They would each provide 100a, for a combined total of 200a.

MrPsychedelic said:

going 16s2p but I'm confused how I could run 2 bms doing it that way also?

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16s2p
Is 1 x 16s battery with a BMS, and another 16s battery with a BMS in parallel.

Configuration wise, both are good.

App support is adequate for both.

JBD likely has a passive balancer.

Depending on the model, JK can be an active or passive balancer.


Active balancing is good for batteries that have deeper discharges since they can be configured to actively balance the cells. Also better for those real B grade cells that are bloated and tend to have cell voltage deviations.


Passive balancing requires you to charge the batteries to full capacity more often to top balance the cells and mitigate cell voltage deviation. My guess is fully charge batteries at least once per month.

Longevity, I don’t have enough experience to say which is better.


Overall, I would chose JK with active balancer

You can trust Amy Wan of Luyuan on Alibaba (https://szluyuan.en.alibaba.com/).
Great reviews and she was awesome for me with great communication. She has had a great reputation on this site for a number of years. I don't think I could find a negative review in her. Amy at Luyuan is the only reason I signed up with Alibaba, and so far the only company I am comfortable ordering directly from China. (If anyone else knows other trustworthy companies on Alibaba, please let me know.)

For smaller items like a BMS, she can send it by air!
The key is not to use the cart, but chat with Amy (way better shipping prices). Do everything by chat. Also let her know you are from the forum. Keep in mind that she is in China so there is a 12 hour time difference than the East coast.

Amy sells JK, JBD, and a few other BMS's (https://szluyuan.en.alibaba.com/productgrouplist-915816607/BMS.html).
I am still charging and balancing my packs, so I haven't had a chance to fully test them out. the JK BMSs fired up and connected to their app flawlessly. I bought the JK-inverter type with 2A active balancing. If you decide to get the JK BMS be sure to specify what features you want such as heater controls and types of communication ports. The 4.3" screen with on/off switch is awesome.

I have the jk-B2A8s20P for my 12V batteries and jk-PB2A16s20P for my 24V batteries, because I basically told Amy to give me the parts to build the batteries like @Steve_S has (which were awesome and went together perfectly).
Here are some charts that compares JK's different active balance BMSs: