question

motylu avatar image

Overpowered MPPT with Pylontech batteries?

Hello,

for my house I will install PV during next spring and I want to use Victron devices with Pylontech 48 V LiFePO4 batteries (4x US2000C or 3x US3000C). I will have 2 strings - one string to south-east (10 panels 330 Wp, 5S2P - 2 parallel sections with 5 panels in series, 3300 Wp in total) and one to south-west (12 panels 330 Wp, 4S3P, 3960 Wp in total).

I was planning to use MPPT SmartSolar 250/60 for S-E string and 250/70 for S-W string. For example type 250/70 is (according to datasheet) suitable for nominal power 4000 W, but its apparently valid for charge "absorption" voltage approx. 57 V. For this voltage max. output current of 70 A should be sufficient without any significant PV power limitation according to my calculations including losses (<70 A for panel temperature >10°C). If I will use Pylontech batteries I must set charge "absorption" voltage only to 52 V (due to problems with overvoltage warnings), so theoretical PV max. power with 250/70 will be only 3640 W (practically <3600 W due to MPPT efficiency.

So I must use more expensive 250/85 (which is only in VE.Can modification) instead of 250/70 only due to Pylontech batteries, if I am right? Similar situation is also for S-E string with 250/60...


Many thanks for you answers!

MPPT - Solar Charge ControllerPylontech
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1 Answer
Murray van Graan avatar image
Murray van Graan answered ·

Hi @motylu

The 250/60 and 250/70 MPPT’s should be fine as is, the PV panel rated power is not really achieved 99% of the time therefore you won’t loose any potential power production. In the odd occasion that the PV array does produce its rated power the MPPT will just limit to the rated charge current

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