HI,

Firstly, thank you to all. This forum is excellent and has been absolutely invaluable in getting off grid.

I have an Axpert voltronic 5Kva 48v PF1 (with the 450v MPPT). Its attached to 12 x 335w JASolar poly panels, in strings of 2 x 6.

I am using two Lithium battery units, rated at 100Ah @ 48v. They have a BMS and their charge profile recommends a 53.5v for bulk and 51v for float.

Everything seems to work alright for the most part. The inverter and batteries hold a good load, the battery capacity seems to be what its rated at and I can usually charge the batteries fully during the day from the solar arrays.

However, I am getting some weird behaviour during solar charging during the day. The battery voltage slowly increases as it should, with the correct, set amount of amps going through to the batteries, from the MPPT. But every now and again, the inverter spikes to a battery voltage of 60v (which is accurate as I tested this with a multimeter on battery and inverter batt DC terminals).

 

When it does this, the batteries go into an overvolt state and temporarily shutdown. The inverter flashes a battery voltage too low error code. Then the voltage drops back down to where the charge left off, the error clears, the batteries reset and the charge continues.

I have checked all relevant settings for bulk, float, low volt disconnect and return to battery. I have checked the charging current versus the manufacturer rating and I am well and truly below (rated 50A per battery, only supplying 40A max)

Anyone seen this behaviour with lithium batteries on voltronic inverters before? Any help or advice is greatly appreciated.

 

Edited January 24, 20205 yr by theotherguy

7 minutes ago, theotherguy said:

They have a BMS and their charge profile recommends a 53.5v for bulk and 51v for float.

They are presumably 15S LFP. If so, 53.5 V is way too high. Even the PylonTech recommended value of 53.2 V is too high in my opinion, but you could try that, or any values down to 51.8 V.

Similarly, you could reduce the float voltage to as low as 50.3 V, but that's not as important.

But if they're 14S of one of the 3.7 / 3.75 V nominal per cell chemistries, then that's probably much different.

.

They are the same as the following post:
https://powerforum.co.za/topic/2722-esm-48100a1-li-ion-battery/I did try drop down the voltages considerably. We tried several settings on the way down to 50v float and 51v bulk. But we still saw the random spikes to 60v.

 

It does not do this when the load is completely removed, or when not charging.

Well aware of the SoC issues with voltronics and intend to avoid using the inverter for SoC readings (have a Victron BMV712 on the way for that), but the batteries going into overvolt protection worries me a bit. As does the flick on and off for charging, for seemingly no reason.

Edited January 24, 20205 yr by theotherguy

I have a similar setup - similar issue,    2 ESM 100AH 48v Huawei bats, Inverter & MPPT charge controller are EPEVER.     system completely stable charging or discharging but when both charge controller and inverter are running I get the high power spikes...  went back and forth with EPEVER support thinking it was their issue, but it looks like a combo.  a chance in power draw by the inverter while charging with a charging voltage above 52.5 (ish in my testing) , somehow spikes the voltage enough that the ESM's BMS seems to disconnect momentarily shooting the line voltage way up.   (I think my previous  5000W hybrid Growatt inverter fried because of this cycle of voltage spikes.)  After a month of emailing with EPEver ... I put long leads 2+ meters between charge controller and bat.  AND the main fix was to dial down my bulk & float charge to under 52.3.  There remains some minor voltage spikes (54v or so) occasionally, but not often.    I hope this helps