Fogstar drift 24v 280ah not a good idea to put 2 batteries in series

Not working well when connected in series.

[@amydennett4871]

Hi , I also had this issue, I bought 4 x 12v 560ah , and I first noticed when my solar watts dropped out but the battery was 83 percent as yours , did you raise a complaint with fogstar and how did you get on? They just ignored our emails at least 5 of ,shocking customer service, however it does seem like the battery's have settled down now but I'm still sceptical on the issue, has this happened since or still happening with yours ???

[@trickydicky6788]

Hi, originally I was using a 24volt system so my 2 x 24v batteries were wired in parallel and worked well. But since then I changed my system to 48V so my batteries are wired in series, that's what is causing the issue. No I haven't contacted fogstar, I can't really see the point. What voltage system are you running, if it's 12V you should be OK, if its 24v or 48v then yes I expect you to be having problems. Regards Richard

[@amydennett4871]

Yes I have a 24v system, 2 s 2 p if makes sense, I was gonna cut them open to see there was different bms like you thought there might be but this makes my warranty a bit useless can't think of any other reason as to why they behave in such a way in series after all they have been marketed to be connected in such a configuration

[@benfacer2961]

Please don't cut them open, the BMS is exactly the same. Errors in reporting are common with most LiFePo4 BMS. We find the JBD we use to be the most accurate of them all. The 'jump' to 100% is triggered by cells being 3.5V, then is a pre-programmed jump to 100%, to reset the counting and any errors that may have occured. The JBD BMS cannot measure under 1A, so overtime this can create errors. If you want 100% accuracy, then an external shunt is recommended. @@amydennett4871