Supermicro Server PSU mods (PWS-920P-1R) or rather: 3kW 43.2V Supply needed - Page 1
Forum section: electronics / projects

author: dj_ordje
author_rank: Newbie
timestamp: December 17, 2021, 06:42:11 pm
content: Hello guys,I've got a Supermicro Server PSU that I want to modify slightly.. The goal is to charge LiFePo4 Cells with 14.4V and as much Amperage as I can get. The PSU is rated for 75A, while the cells (Headway) allow for 80A max continuous. I'm guessing to keep it safe 64A should be the max. to keep it around 920W as specified.However, thats all theory, I need to get it working firstThe Board is called 35RO-921111-M16F and was manufactured around 2014 if the date codes are to be believed.I've started to look at the circuit and it seems like a PIC16F1937 is running the show, or should I rather sayruiningit... Apart from that there's only two LM324s, a mysterious 8 pin chip labeled "4424 YM 1401" (One is also on the primary side near the powerMOS so maybe something SOAR related or a gate driver?) and a CM6901X on the secondary side. Messing around on the primary is probably not nescessary as I only need toslightlyincrease the output Voltage and fool the PIC into thinking everythings fine.Also would be cool to have amperage control but that should be rather easy as the ACS756-SCA-100B current shunt outputs a analog signal thats then amplified or comparatored by one of the LM324s, so easy point of attack there. Current regulation seems to be done with a quad of IRF-3206G Hexfets.So now that you know what I'm up to heres my question for you:It would be of immense help if there was any sort of schematic or service manual available. Even a block diagram would make things a whole lot simpler.If there's nothing available, and atm it looks like thats the case, I'm going to trace it out but I'm currently not at all in the mood to spend a saturday tracing tiny circuits with lots of vias and such.And if you think I'm nuts and should stop what I'm doing immediately, here's the backstory:I want to build a concept ebike, that can charge with up to 10C like the cells are rated for. Basically it would be cool to drive 40km, have a coffe while recharging and then being able to drive another 40km instead of having to wait an hour or more.This can be accomplished by using EV chargers, they can deliver up to 22kW 3 Phase 230V on a Type2 connector...However, my main problem is finding a suitable charger that can deliver the 2 to 3kW needed at either 36V or 3x 12V. My idea was to split the pack into 3 groups of 4 cells each and use 12V Server PSUs which are cheaply available and built to last.But if you've got any other Idea how to achive 3kW at 36V(43.2V) without breaking the bank please let me know!Looking forward to seeing what you guys think of this!

author: tunk
author_rank: Super Contributor
timestamp: December 17, 2021, 06:53:46 pm
content: Looks like LiFePo4 is charged the same way as Li-ions, i.e. CC/CV/cutoff.How are you going to do the CC and cutoff parts?

author: dj_ordje
author_rank: Newbie
timestamp: December 17, 2021, 06:56:27 pm
content: QuoteIt can be charged with CC/CV but it doesn't strictly need to like Li-Ion or Li-Po. The PSU is able to limit both current and voltage so that should be fine.

author: tunk
author_rank: Super Contributor
timestamp: December 17, 2021, 07:46:54 pm
content: My impression of PC PSUs is that they will not do CC, but rather do over-current shutdown.

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 18, 2021, 01:23:30 am
content: Get a 48V telecom rectifier and turn it down? Or just upgrade to a 48V pack.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 18, 2021, 07:35:14 am
content: An standard computer pasu will not cc, only short and over current protectionThere is a web site for server psu converted in chargers RCGROUPS.COM some psu have been decrypted in their pinouts, just find the suitable ones for youYou can find some of them ultra cheap, some of them need forced air to work IE: no fans in them, that's a no go for me. Forgot this ''little big detail'' and saw a beautiful psu go pooofManaged to get some 12v 100 amps psu for dirt cheap 20 buck eachDont go thinking you coud easily replace or recode an psu mcu with basic knowledge, some of them have load balancing and others can communicate between them etc ...

author: Boscoe
author_rank: Frequent Contributor
timestamp: December 18, 2021, 09:36:43 pm
content: Forget modifying existing PSUs for dramatically different output voltages or CC. They weren’t designed for that and will almost certainly fail catastrophically in some corner state even if you get it working in simple cases. I suggest you get a telecoms 48V PSU (often referred to as a rectifier) and build / buy a DCDC converter to get the voltage and the CC you need.

author: TheMG
author_rank: Frequent Contributor
timestamp: December 19, 2021, 02:17:57 am
content: The nice thing about 48V telecom "rectifiers" is that with most of them their output voltage is adjustable and they do have a CC function (sometimes the current limit is also adjustable).This is because I'm the telecom world they are usually connected directly to a large lead-acid backup battery bank. If the batteries become deeply discharged (extended power outage) they would draw much more current to recharge than the power supplies can put out, so they must have CC capability, as well as voltage adjustability for bulk charge, float, and equalize.I have one such rectifier Argus Technologies RSM 48-50 that is rated 2.4kW and actually has a front panel display which allows it to be configured, I believe it is adjustable anywhere from about 40V up to 60V or so. Only thing I had to do to get it working (without the rack shelf that it would normally slot into) is to identify and connect the voltage sense pins to the output pins (otherwise the unit goes into fault since it "sees" no output).They (and other similar units) can be found second hand for not unreasonable prices on eBay and the likes.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 19, 2021, 06:30:25 am
content: They are sold around 180$ USD shipping not includedNeed 184-264 VAC 50/60 Hz inputA manual is attached