Lithium Battery Requirement for Mikrotek 2KW/36V Solar Inverter

Nairspecht

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Hi, I'm looking to setup a off grid system using Mikrotek 2KW/36V MPPT Solar inverter with Okaya lithium ferrous phosphate batteries. My query is, how many lithium batteries should I connect to this system? The options available are 12.8V/80Ah |12.8V/100Ah | 12.8V/120Ah. Battery support by inverter is 80Ah to 200Ah. Can I connect 3 batteries of 12.8 V/100Ah in series. I have attached the tech specs for the inverter as well as the battery. Also, would connecting 2 solar panels of 395W suffice for charging the batteries?
 

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Turponieminen

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Hi.

I did not see any specs for the batteries. Based on quick Google search batteries look like a cheap lead acid replacement, and datasheet of 100Ah and 120Ah versions are supporting only 10/25A of charging and discharging current. (80Ah version even less) I'm guessing that is maximum continuous/momentary current.
10Ah continous at 38.4 v is only 384 watts. Also no confirmation can they be connected in series.
I would not use these batteries in a solar storage setup (or in any setup for that matter).

What comes to charge controller, if you are going with LiFepo4 chemistry, you want to make sure that the controller has manual and working settings for equalize/bulk/absorption/float voltages, otherwise you will shorten their lifespan to no more or even less than lead acid batteries.
 
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Nairspecht

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Hi, thanks for the insight. I thought of going with these lithium batteries, as they're the most preferred ones for solar setups in my country. I have attached the battery specs and solar panel specs for clarity. I improved the panel to a pair of 440W. Could you please advise, what battery spec would be the best setup for this inverter and solar panel? and should I go for the bifacial panel (attached spec). Costs almost similar to the 440W panel.Screenshot_2021-08-02-10-02-59-907_cn.wps.moffice_eng.jpgScreenshot_2021-07-30-16-57-09-346_cn.wps.moffice_eng.jpg
 

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Turponieminen

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Yes, there is no confirmation can the batteries connected in series safely. Even the maximum Charge/discharge current would be 25A it is still just around 960w. That is too close to the maximum power output of two 440w panels. And less than half of what that AC inverter you are going to use can provide. Now i don't know if the datasheet is wrong, but I'm guessing this battery manufacturer is sourcing their LiFepo4 cells from wherever it can find them more cheaply. Then using very small 25Amp BMS not to damage those already b-grade cells.

Now there are similar LiFepo4 batteries that claim decent specs, you might consider them or even lead acid.

What comes to panels. If bifacials are off same price you might want to go with them.
 
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