July 26, 20224 yr Hi guys. Has anyone experience with runing Pylontech batteries in parallel with DIY LifePo4 packs ? I have started to look for 3.2 LiFePo4 batteries 280-300Ah and thinking to start changing my 5 Pylontech's with some "home made" packs. Pylontech is good , stable but expensive when thinking at $/kwh Right now my Pylontechs give me 321Ah and total cost was over 6000USD. With 6000USD i can build 3 x 300Ah packs... As I do not have the 6000 at habnd I was thinking to buy 16 x 3.2V LifePo batteries , build one pack and then sell 2 of my Pylontechs ... then buy 16 more , build one bank more and sell the rest of the pylontechs. So when I make this , I was thinking to run the Pylontech in parallel with the self made pack ... if possible ??
July 26, 20224 yr 4 minutes ago, Jaxone said: Has anyone experience with runing Pylontech batteries in parallel with DIY LifePo4 packs ? Don't have, but keep the following in mind, your Pylontechs, are they 15S or 16S batteries, in other words, how many cells do they contain each? if you want to run a DIY bank in parallel, it must be the same amount of cells for the DIY bank, I personally would not consider a 15 cell LiFePO4 battery and will be going your proposed route in the future, this I had already planned, my battery is a 16 cell, so I should have no trouble paralleling up a DIY bank, when I do go down this road... Next issue is what charge controller/inverter are you using, if you are using CANbus or RS485 comms between the Pylontechs and your charge controller/inverter, then this would make a DIY parallel setup difficult again, you would have to use voltage control parameters to make this work...
July 26, 20224 yr Author Pylontech is indeed 15S but I don't think that is important ... Pylontech has it's own BMS , my DIY will have it's own BMS. Will supply same voltage to both and BMS should do it's job for each pack. I don't charge my Pylontech to 100% anyway so if inverter is charging with 52.2-3 will be ok for all banks. Well, if I get my hands on some good quality 300Ah+ cells and build a pack , I can safely switch off the Pylontechs and run only with the home made pack. For now , I am studying Alibaba for some sellers with EU stock and thinking to take the plunge and buy 16. Kinda risky on Alibaba but don't see many alternatives.
July 26, 20224 yr 2 hours ago, Jaxone said: Pylontech is indeed 15S but I don't think that is important ... Pylontech has it's own BMS , my DIY will have it's own BMS. Will supply same voltage to both and BMS should do it's job for each pack. I don't charge my Pylontech to 100% anyway so if inverter is charging with 52.2-3 will be ok for all banks. No, The BMS tells the inverter what to do and only offers protection and balancing features to the cells within them. If you use different cell numbers then you must deal with that outside of the battery packs. It is possible though. 52.5V is the minimum charge voltage for the Pylontech, if you don't reach that sort of voltage then the cells won't balance. If your adding 16 cell packs your going to need higher then 52.5v to balance them. Edited July 26, 20224 yr by Tinbum
July 26, 20224 yr 11 hours ago, Jaxone said: Pylontech is indeed 15S but I don't think that is important ... Pylontech has it's own BMS , my DIY will have it's own BMS. Will supply same voltage to both and BMS should do it's job for each pack. I don't charge my Pylontech to 100% anyway so if inverter is charging with 52.2-3 will be ok for all banks. Oh this is very important. Voltage is potential difference. Meaning, if pack A is a 16s & pack B is 15s they have very different charge & discharge profiles. The nominal Voltages are different. So the two BMS will constantly be Charging & discharging each other. It's really not a good idea at all to mix 15s & 16s packs of any brand. If however, the packs have the same series count by all means one can go ahead with your strategy. Connect them to a DC busbar & keep the cable lengths the same for the resistance & current sharing to be equal or proportional to the pack size. I would look a lot deeper than relying on a BMS to try to oppose the physics of what 15s Vs 16s can do. It's like having two horses of widely different caliber pulling a cart. At some point one will drag.
July 27, 20224 yr 21 hours ago, Jaxone said: Pylontech is indeed 15S but I don't think that is important Just make a 15s pack. Putting 16s and 15s in parallel is just asking for trouble.
July 27, 20224 yr Author Thanks everyone for the input. P1000's Idea with 15s for the DIY pack is not bad either Anyway , this is a project for next year as the budget for my solar system is exhausted and the priority would be to buy a Deye inverter first so I can start injecting to the grid. Thanks everyone for the input , will study the possibilities some more until next year when I would have money for this.
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.