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semiraue avatar image
semiraue asked

Sizing charge controller and panels for new battery pack


Hi All,

I have below off-grid setup at the moment for power most of my DC devices (lights,router,nas,nvr,etc..) on my remote house.

  • 2x JAM solar 460W panels in parallel this
  • victron smart solar mppt 100 1 20 charge controller (12/24/48v)
  • 12v 100AH deep cycle Sealed lead acid battery

I'm not sure these panels are too much for the controller. and most of the time I can only see max 291w of P Max(photo_2022-03-19_18-47-39.jpg). does this means controller reach it's maximum capacity?

I'm planning to upgrade my setup to more powerful AC off-grid system to power my entire house. also to run smaller server rack.

I'm planning to buy below new items

  • 4x sok 206Ah lifepo4 batteries
  • or 1x jakiper 48v 100ah rack mount lifepo4 battery
  • Meanwell TS-3000 inverter this

If I purchase these new equipment, can I use them with my existing PV array and charge controller ? or do I need to add more panels or change my charge controller ?

if can use, do I need to connect panels in series ? since each panel Voc is only 50.01V?

I was planning to buy 12v inverter with 1x 12v LFP battery. but on many sites I saw that if making off-grid setup more than 3000W better go with 48v system. invert from 48v->230v is better than 12v->230v as many sites suggested. Is this true ? my usage is not more than 2000w. but for future improvement I would like to have 3000w inverter.

battery chargingchargerSolar Panel
photo-2022-03-19-18-47-39.jpg (69.4 KiB)
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nickdb avatar image nickdb ♦♦ commented ·
You have chosen a non-victron ecosystem, apart from the mppt. You really should be asking the suppliers of your equipment if they will support your choices.

A 20A mppt can produce a maximum of 240W at 12V, 480W@24V and 960W@48V.

At 12V your mppt is the limiting factor for your panels.

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semiraue avatar image semiraue nickdb ♦♦ commented ·

Thanks for this. I would like to use victron products for everything. Unfortunately, I cannot buy victron products in this location easily. or have to pay four times the price of actual price for available victron equipment. So I decided to set up everything myself with the controller I bought when I'm traveling outside the country.

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wkirby answered ·

Change to 48V at your earliest convenience.
Your cabling can be smaller size for the same power. Your charge controller will output four times the power on a 48V system than a 12V system, like nickdb described earlier.
There are a much wider choice of 48V lithium batteries available.

Series connection of your panels would be necessary for a 48V system, because 50V PV Voltage will be too low. However with series connection your PV Voltage will be too high for a 100/20 charge controller and it will likely be damaged by excessive PV Voltage, the limit is 100V.

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semiraue avatar image semiraue commented ·

Thanks for this. I will go for the 48v system then. either with four 12v batteries or one 48v server rack battery. but as you said if I connect panels in series do I need to buy a larger controller ? when I check the datasheet it says


1a) If more PV power is connected, the controller will limit input power.
1b) The PV voltage must exceed Vbat + 5V for the controller to start. Thereafter the minimum PV voltage is Vbat + 1V
2) A PV array with a higher short circuit current may damage the controller.

Does this mean if I input more than 100V PV volts the controller will limit the input power and if I input more than 20A from PV it may damage the controller ?


Also my MAX PV Voltage never go beyond 46V so far.


Basically more Volts are ok but more Amps will damage it?

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