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alexandervich avatar image

LGChem RESU 6.4 - SOC only reaches 94%

System is LGChem RESU 6.4EX, Victron MultiPLus 48/3000/35-16

Settings are:

Charge Voltage Limit 58.1V

Charge Current Limit 110 A

The SOC never exceeds 94% - does this mean that it is full but the monitor is inaccurate? I note that the LGChem RESU is never charged to 100% but limited to 97-98% by LG. However I am getting 94%.

Note that I recall the installer tweaking the CVL up a little to try and get it to reach a higher SOC.

SOC
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2 Answers
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kevgermany answered ·

How are you measuring SOC?

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The SOC I mentioned is that reported by the VRM. So clearly I don't know the actual SOC.

Also I note that the Battery State of Health is reporting as 90%. Don't know if that is meaningful either!

So if the state of health is truly 90% and I cycle the battery once a day between 15% SOC and 94% SOC (the maximum it gives me) then in theory I get 6.4*0.9*0.79 = 4.5kWh. However, the Multiplus consumes power to invert. I reckon it uses around 250W, if discharging at maximum rate, then 2 hours to discharge and 0.5kWh. Hence I should get around 4kWh out of the battery. In fact I am getting between 3.5 and 3.9kWh each day according to VRM. So I guess I am not far off - it all depends on whether my duty cycle is 94% to 15% or whether the SOC values are unreliable. It feels that I am a little low.

If you have a GX device I suggest you connect the RESU to the GX which will get the correct information from the battery. Use the settings as per the instruction on the Victron site. Victron however does not support the LG batteries for the newer multis the last time I checked, but I found it works just fine with both the MP II 3 and 5 kVA I tested and installed it with. The 6.5 RESU has 6.5kw (126Ah at 51.8V nominal) capacity and 90% DOD leaving it with 5.9 kWh usable. With a greater than 95% roundtrip efficienct under STC, you maybe able to roughly guage better how it performs. Hope this helps to correctly configure the shunts, MP and whatever else you are using. Also ensure that you have set charging for lifepo4 profiles, fixed etc.

kevgermany avatar image
kevgermany answered ·

I think you have found the limitations of SOC estimates. Shunt based will give more accurate info.

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