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No that anyone here seems too interested anymore, but I figured out my issue. I had dutifully gone through and connected one balance lead to each battery post, and missing the fact that since I have one battery that wasn't part of the welded together pack, I have two posts for "one" cell in the...

Looks to me like with Overkill you pay a $100 premium for a JBD with better US support and a less sketchy app

Thanks all. @Robbert my plan is to add the battery to the front left spot in my picture there, on the negative end as you mentioned. As I'm already replacing the damaged BMS I figure they might as well match so I'm not going to get in to reprogramming the cheapo one that's in there. @chrisski...

I bought them. One worked with a quick fix but has a slightly wonky BMS. The one with the broken display I haven't touched yet Adventures to follow as they develop https://diysolarforum.com/threads/what-did-i-just-buy-for-400-two-48v-server-rack-batteries.77694/

Good to know, thanks. Glad I probably didn't do damage. For the second pack I'll series charge with the still functional BMS installed but I'll cap the voltage to 51.75 as you recommended. I'll then target that 3.45 volts to charge the new 100 Ah cell that's going in and let the 0.6A balance on...

@Robbert I quickly googled a seplos BMS and I agree it looks like what I have. They don't have pricing on their website but the Amazon listing has it at $240 which is more than the Overkill BMS and seems like a worse choice overall. To be fair one Seplos is less than two Overkills, but I think...

On initial charge before installing the BMS I took everything up to 3.6V each (the original 15s pack and the 1 new Eve cell) and then let it settle. Recharged with the BMS installed up to 56.5V, so 3.53/cell and let the BMS finish balancing down to 0 mA. Should I have done something...

Thanks for the heads up. I just got off the phone with Signature Solar. I think what I'm going to do is get a EG4 Chargeverter to keep the batteries topped off, and go 100% inverter powered on the circuits I wish to back up. As I see it this does two things for me. First, it will let me hold...

I pulled the one with the smashed screen apart tonight. It was dropped pretty darn hard on the front face, I'm surprised the case didn't show damage from that happening. The internal support bracket was crushed up against the back of the BMS and one of the negative cables was cut by the event...

I just fed my benchtop power supply through an RC wattmeter into the load tester. All aligned within a few milliamps, so the BMS calibration is off as I suspected. Looking around some more on calibrating the current I found one reference that alleged to have talked to a JK engineer who said the...

Thanks @MaikaiLifeDIY optimizers are a great thought to include. I'll have to look and see if I can get them with rapid shutdown built in to the optimizer as well. @zanydroid Is there any good way to test other than just for voltage? I guess I could try a short circuit amperage as well? More...

Battery hookup just told me it's okay to lay the cells on their sides so I'm going to try that assembly method.

Do you have a suggestion on where to purchase from? I had been planning on signature solar because I've heard good things about their support. Edit: also not sure that I really need as much as 5k anyway, though if it was the same price as I'm looking at I would go for it. My plan is to use this...

He said he had a bunch of people lined up for after work, first come first serve. I took advantage of my flex time at work amd took a long lunch instead 😜 He seemed fine enough to me and was nice enough in person I suppose. Sorry he was rude to you. Thanks for the links, I tried contacting a...

I was looking at Facebook Marketplace earlier today and came across someone selling a PAIR of server rack batteries in unknown condition for $400. Figured at that price I couldn't lose, so I hopped in the car and snagged them. Cases are pretty beat up looking with bent rack ears and some dents...

Sounds good thank you, I'm going to order these ones then https://srikobatteries.com/product/jk-smart-active-balance-inverter-bms-with-8s-16s-100a-with-1a-balance-current/

SOC has started coming up as I've gotten it charged over 50V. I can only charge at 5 amps and don't really trust this charger unattended so it'll take me a bit. I have it up to about 30% SOC now though

I couldn't actually tell you. I assumed that the BMSs needed cal as I've seen a few posts about it. I don't trust my clamp meter down to readings that low so didn't verify past it being in the same ballpark. I should probably just buy the SmartShunt. Currently recharging and the Eve cell is...

Alright, capacity test on the first pack is in! 102 Ah, 5.3 kWh. Looks like I really scored with this purchase! One thing that is curious to me however is the discharge curve I'm seeing. All the cells were in lockstep voltage wise up through about 80 Ah of discharge, at which point the brand...

@42OhmsPA @sunshine_eggo Well you guys were right, the end went really fast and the crappy BMS could not be trusted. Unfortunately I didn't read your replies in time and half fell asleep on the couch so it went 2 hours past my post there. Final cell voltages got higher than I intended in a...

Looks like the choice would be either of these? https://srikobatteries.com/product/smart-jiabaida-jbd-16s-48v-100a-lifepo4-common-port-battery-protection-module/ https://srikobatteries.com/product/jk-smart-active-balance-inverter-bms-with-8s-16s-100a-with-1a-balance-current/ I bring up the JK...

Can anyone with more balancing experience chime in on the merits of 0.6/1/2 amp balance current for this effort? I'm keeping in mind that theoretically there will be 15 cells with identical capacity and then one with presumably higher capacity in series. The current BMS appears to have 4.7 ohm...

I just picked up two no name brand 15s server rack batteries as detailed here. One of them (possibly both) needs a new BMS. I'm finding that options for 15s BMSes look relatively slim when thinking about overall features and compatibility with other packs in the future as most good server racks...

Ahh my misunderstanding, reading things on mobile makes me miss too much, I'll dig in when I get back home.

I will have two batteries in parallel at least, but yes I was thinking 100 amp would be appropriate anyway. It is likely to only be wired such that I'll use 1500 watts of its output at the most with what I have planned. Of course plans do have a way of expanding over time!

You're thinking I might benefit by going up to the 150 amp BMS to get up to 1 amp balance current? That's a $20 jump which isn't too bad, but the one with 2A balance is a $40 jump so that's getting a little large for my "cheap" project. (as if there's such a thing!)

@SeaGal I am nominally doing a top balance. I have about 0.25 V drop across the wires since finding some appropriate washers to clamp down on some wires. Multimeter on the cell is reading 3.4 V with the PSU currently supplying 3.65 V at 5 A. If I drop the PSU to 3.45 V current drops off to 1.5...

Oh my goodness I just went to move the working original BMS from the fully charged battery on to the damaged battery, and discovered that the cells in the two batteries are installed opposite of each other!! Same cell arrangement in the case, but one was built in each direction so one has the...

Okay, finally got all the parts in and got the first battery set up with the JKBMS. I'm getting an error that the cell count is not equal to settings. I changed the settings to 16 cells, however the BMS is only showing 15 cells. I have double checked my connections and the black wire goes to the...

@Robbert You mean that the JK app also would work with that cheaper JBD BMS linked above?