Found this interesting video from Will Prowse on using different make batteries in the same bank. Assuming the battery operating voltages are the same and you are not trying to mix Pylontech’s with almost anything else, it makes sense, although not best practice.
Andy from Off Grid Garage did similar, he used different size cells in one Frankenstein bank.
I did it before any of them. Connected 100ah 2nd Life Lifepo4 cells to brand new 280ah cells.
It worked quite nicely, as a 100ah bank.
But not long term.
It is interesting to see that someone else also tried this. I did the same test in our test center , but I went a bit further and found a way for different brand bricks to communicate as a combined pack, even made bricks from brand x to think his a brand y resulting in a bank of up to 5 bricks of different brands running as a pack of 5 from the same brand. At the time I told my friend down in Somerset West that I would most probably never make the results public out of fear that someone would try it because I said its possible and then run into warranty issues in the future.
I did the test to challenge some myths and sales pitches (Maybe just out of curiosity) and was surprised to see what is possible.
Do not risk your warranty just to save some money by adding cheaper bricks to your existing bank. I did not test it long enough to tell you what would happen after a few months.
For me… if the BMS is good (refer back to Andy) and has the settings that allow proper management then you should be able to combine banks with no issue. Note: 15S (Pylontech) vs 16s is not going to work due to voltage differences.
Well, to let the cat out of the bag, they were two competing brands with the same BMS on the inside. So simply reprogramming them to think they are of the other brand… and they work together seamlessly.
I had similar with different DIY BMS and it mostly work well. But as each BMS has it’s own logic they do tend to influence each other more, balance at different times, etc.
If you want to install and forget then I also suggest you stay with the same BMS for everything in your bank.
The biggest issue is when one battery has a “fully charged” voltage that is lower than the other’s start balancing voltage (eg. BSL requests a very low voltage of 45V, which is lower than the voltage at which some of the batteries with the same BMS will start to balance). If you reprogram them to have the same balance and full voltage thresholds they should be good.
Agreed! Stick to the same make/model of battery and PV panels if possible.
Mixing and matching will only complicate your life!