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MarkusK avatar image

Extending my system with new panels and batteries

Hi,

I have a solar panel system with 4 x 150W panels (Voc 22,3V, Isc 9,1A) in series and 2 x 12V AGM 140Ah batteries in parallel controlled by a Bluesolar MPPT 100/50. Now I'm about to extend with 8 more panels of same type and 6 more AGM batteries of same kind as the previous ones. My plan is to make it a 24V system instead and setup the panels as 3p x 4s, thus keeping the panel voltage but increasing the current. I'm wondering is there a way I could use my around 2 years old batteries in this setup or do I need to leave them aside. Can a balancer help me here, I don't fully understand how it works, what would the wiring be? I would like to make a 4p x 2s batteries setup, but if I can't use them I will need to go for 3p x 2s and leave the old batteries to setup a separate system. I would really like to use them and have the capacity.

Thanks,

Markus

battery chargingBattery Balancer
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1 Answer
WKirby avatar image
WKirby answered ·

Stepping up to 24V will be great. You'll double the output power of your MPPT in the process. You'll have more PV power that the 100/50 can take full advantage of, but it won't be a problem.
90V of PV is close to that MPPT's maximum input Voltage, but if you've been fine for the last two years then no need to worry I suppose.
I don't like too many parallel battery strings, it can get unwieldy especially if an older bank is connected with new ones. The three new ones could dump a lot more energy into the old string if something were to go wrong with it or its ESR starts to rise with age.
I don't really like the idea of more than two parallel strings of batteries, but three will probably be fine if you keep an eye on them.

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Thank you for your answer. The controller can take 100V according to the data sheet so I guess 4 x 22,3V should be ok and the full voltage is not very often reached.