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Jonathan Carrasco avatar image
Jonathan Carrasco asked

Parallel connection to 4 solar controllers

Hi, I would like if someone with more experience than I can help me to solve this. Actually we have an Off-Grid site with 4 PV strings, every string have 16 50w solar pannels connected in serial-parallel to get 24V to the power bank (14 batteries 12V 100Ah each battery). Each string have a Morningstar PS-30M, but they are connected in parallel on the load port and works well, but we have to replace them, because they have more than 20 years in use. I have seen that a Smartsolar MPPT 150/35 is a good option, but we can't connect the battery banks in parallel to charge the batteries because they are in 2 different places with a distance between them of 4 meters (around 8 meters of cable difference between the longest cable and the short one, so they could have a difference of the charge voltage. How can we connect the battery banks to the load with the Smartsolar and maintain the 4 battery banks?

Thanks a lot for your help.

battery chargingSolar Panelbattery system voltagecharge controller compatibility
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JohnC avatar image
JohnC answered ·

Hi Jon. To be clear, you have 3200W of panels? And want 4x new mppt's to replace the old pwm's? Just to make sure we're talking about the same animal here..

You could do this with 4x 100/30 Victron mppt's. No 'load' ports needn't be an issue, just take the loads from the 'batt' ports (2 wires into 1 hole doing that, unless you use a bus). This is likely just the same in effect as what you've been doing for all those years.

It's unconventional, but I can *sorta* understand how you've got away with it for so long with so many paralleled batt strings. The issue is batt imbalance, and the textbook would say no, but if it works for you the Victron cc's shouldn't change anything really..

You'll need to restring your panels to suit mppt. Your 4x existing 16x panel 'blocks' are likely strung 2S8P, and 4S4P would work fine for mppt.

But I may have all this wrong. Come back, hey, I'm trying.. :)



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