Givenergy Battery Capacity Problems

ispookie666

DougMLancs said:

I’ve been taking notes. Sending it all off to my installer who was down to fit us with a 9.5 kWh Givenergy battery as part of our installation in March ‘23. My place of work, my bosses’ house and a friend all have GE batteries fitted by the same installer we’re using and haven’t had any issues but it sounds like it’s worth talking it through and considering alternatives. 

I had my installer back yesterday, I showed him the dashboard which showed the SOC errors and he was surprised!  

ispookie666

28% difference.  I'm hoping to run this down tonight and then charge up.  

ispookie666

With no end in sight from GE, I guess this is in a limbo. 
On the plus side, the battery has not degraded yet! The battery did drop to 45.2 V before it cut off - that too only one of them! 

Still waiting for GE to get back to me to fix the EPS problems 🙄

QrizB

ispookie666 said:

The battery did drop to 45.2 V before it cut off

If the cells are perfectly balanced thats just over 2.8vpc - which is lower than I'd choose but still "safe", from my reading of the SOC charts.

I've told my Sofar not to discharge below 48V which is 3vpc and loses me about 10% of capacity but gives a bit more headroom for out-of-balance cells.

ispookie666

Very true @QrizB
The annoying this is, there is no way to use voltage as limits for charging and discharging.  Unfortunately I cannot see a way of implementing this, unless I set some sort of automation in HA using cell voltage as input.  
Joys of closed system!  

ispookie666

Still no end in sight.
But all is not bad!!!  except the company 

Based on the data from victron smart shunt the round trip efficiency for the batteries seems to be 97.5% 
I have managed to extract 18.8KWh or 9.4KWh(think design capacity is 10.4 but advertised is 8.2KWh) from each battery without going below 50V, I suspect there is another 0.5KWh extractable before hitting the low voltage cutoff. Provided I discharge at very low C or I dont use any device which would pull above 1kWh. 

All this brings the algorithm using Voltage to define SOC to be as good as useless.  

Anyway, I finally managed to use the output from the forecast.solar to define charging limits (using generous help from youtube). 

I do need to refine the forecast.solar to match what i'm actually generating!!! 

Solarchaser

97.5% efficiency round trip I seriously impressive.

This is you measuring independently the energy applied to the batteries and then the energy you are getting back out?

ispookie666

Solarchaser said:

97.5% efficiency round trip I seriously impressive.

This is you measuring independently the energy applied to the batteries and then the energy you are getting back out?

Using Victron smart shunt - its a seriously impressive kit, I have used ESP8266 to connect it to Home assistant

Solarchaser

I looked up the shunt, and I can kinda see what it does, bit it's based on voltage by the looks of it.
And in your earlier posts you were saying the capacity was being reported quite differently,  so how do you know it's accurate?

Like if you push 5kwh into your batteries, but they were actually already sitting with 5kwh stored, and you get 5kwh back out, but now you only have 2kwh stored, because you put in 5 and got out 5, it looks 100% efficient,  but actually isn't.

My lux appears to be around 82% efficient, some of that is lost to heat as the large heatsink gets hot during charge or discharge, id expect similar from the GivEnergy. 
I guess I'm asking.
A. Are you sure the figure is right.
B. does the GivEnergy inverter not get warm?

ispookie666

@Solarchaser

 A - I would hope so, Smart shunt is used a lot and it pretty much mirrors the power consumption by the inverter
B - Mine is in the garage, when heating it does get to 58C,  I dont have an accurate enough energy meter in the input to work out the efficiency of the inverter.  

I Waited for the battery bank to be empty, then reset the counters on the shunt.  subsequently,  had to wait till the batteries were pretty much empty to work out the efficiency.  

I think you probably might have misread the information - 97.5% is just the difference in Power into the battery and Power out, excluding the inverter.  The shunt sits between the inverter and battery.  The efficiency will depend a lot on the discharge C. 

There is enough information about how smart shunt works (coulomb counting)  and is not based only on voltage.