Li-ion replacement for 48V Rack UPS

[Galaxywide]

Hello! First I'd like to apologize if this is in the wrong spot, and while I know it's not the primary focus of the forum this seems to be the only place I've found good discussion on battery tech.

I'm looking to replace the batteries in my APC SUA3000R2X145 which uses 4S2P 5.5AH SLA batteries, and while I could just pick up some SLA replacements I figured "it's 2022, surely there must be a better way!" After some reading, I was looking into lifepo4 packs and cells, which seem ideally suited to 12v replacement, but appear to be significantly more than I was looking to spend (this is just a hobby, nothing critical nor something I can justify $600 worth of batteries on).

Then I stumbled on these Panasonic 48V Power Modules, which seem like a great option and cheap to boot. I'm thinking of combining them with DALY 13S 48V 50A Li-ion BMSs, and using a total of 2 modules and 2 BMSs in parallel to get the capacity I want. I know the BMSs are undersized for the modules, but given that the UPS can only pull ~56A in total and I'll have them in 2P, I don't think I'll ever get close to the full 100A (realistically this UPS will have MAYBE 500W coming out of of it, unless electricity suddenly becomes free {I realize the irony of that comment on a solar forum, it's something I'd like to look into someday!} and I get a LOT more servers).

Is there anything that I'm missing here, or any reason what I want to do isn't possible (or advised)? I believe I can edit the charge parameters of the UPS via serial based on some posts I've found, which should make it play nice with the different voltage and added capacity.


Thanks, this seems like a great forum!

 

[T-486 Ashepoo]

I would say if you can modify the charger parameters, it should be a fine. I built a portable powerwall with 13s Greenway packs from battery hookup. I use a 54.4 volt charger or Growatt all-in-one inverter to charge them. And the price was right for my budget.

 

[Galaxywide]

Thanks for the reply! I think even if I can't change the parameters, it should be pretty close based on 13S li-ion vs 4S 12V SLA voltages.

So I bought 6 of them Now I have to figure out what to do with the extra 4, since I only need 2...

Possibly stupid question, but do I strictly need 1 BMS per pack, or could I get away with 2 packs per BMS? Obviously keeping in mind BMS current limits, not that I have anything that can really stress them at the moment.

 

[PeSCaLo]

to use only one BMS, you need to parallel them first, and then treat them like one battery pack.
your still limited by the BMS Amps

 

[byteharmony]

Welcome to the form @Galaxywide

I'm starting a project with this same situation right now. 48v APC (schneider) UPS systems that I'm switching to Lithium.

I am thinking of using a little nicer BMS straight from China.

38.16US $ 28% OFF|Daly Smart Lifepo4 Bms 4s 12v 24v 36v 48v 30a 60a 80a 100a 120a 150a 200a 250a 300a 400a Li-ion Lto 3s 7s 8s 10s 12s 13s 16s 24s - Battery Accessories & Charger Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Then balance both packs and each cell set together safely (let me know if you need help learning how to do this safely) so I will have one BMS for the entire pack set. The 100 Amp with bluetooth for $69.
Before I start on any of this I think i have the AGM batteries I need to get one of these UPS bests up and running. Once I do I'll do a voltage test for the max the UPS charges the cells, and then discharge it down to auto power off to learn the UPS standard low voltage disconnect. On the way I'll have a shunt current / voltage / power measuring device telling me how the UPS treats the battery. Assuming all these things tell me it's compatible with that pack AND I can squeeze a them appropriately into some old rack mount boxes I have already I'll start buying them up to make this project work.

Once the engineering is done you can just add as many additional packs as desired to increase run time and reduce stress on each battery as the charge discharge cycles take place.

Maybe I'll even do a video and start the journey towards @Engineer775 and @Will Prowse status.

If I was really lucky maybe I could get @Engineer775 to help me with my plan to get a sol ark 15k on my house before 12/31/2022.

 

[byteharmony]

Thanks for the reply! I think even if I can't change the parameters, it should be pretty close based on 13S li-ion vs 4S 12V SLA voltages.

So I bought 6 of them Now I have to figure out what to do with the extra 4, since I only need 2...

Possibly stupid question, but do I strictly need 1 BMS per pack, or could I get away with 2 packs per BMS? Obviously keeping in mind BMS current limits, not that I have anything that can really stress them at the moment.

Please do not connect these cells to your APC ups system. My tests show the high voltage charge on my APC is 55.2 volts. A 13s pack of 18650 batteries would be charged to 4.26 volts each with this voltage which is bad.

I'll look more into this later but wanted to get you this info right away.