I have similar wuestions that im wondering. I have AGM batteries, ”deep cycle” or whatever supposed to be able to draw 80% deep discharge. But in practice, seems that I can only draw to 80% SOC
At 80% SOC batteries have aproximately 12V voltage. Any voltage under that (unloaded) means that batteries are practically empty… is this right? I have drawn batteries to somewhere 50…60% SOC, and voltages drop neas 11V and at some point whole system shuts down…
Does the ”deep cycle” victron agm batteries mean that you can only safely utilise the top 20% of charged battery?
80% DOD mean using 80% of the battery capacity.
E.g. 100AH you cannuse 80AH.
FYI the full recharge afterward is very important. This is where most people trash their banks - not charging them up correctly.
But the battery voltage drops so rapidly, at 20% SOC it would be near 6V
Do I have something wrong, can this je parameter related issue?
This is also my soc vs voltage so battery is way dead before reaching even 80% SOC
I can’t say for sure.
How many amps are you pulling from it?
3500w from 12v is quite a load -that would be 291Amps. So your bank as mentioned is way too small for the job at hand.
I am not surprised the voltage drops so rapidly.
If you are drawing 50A (600watts), that battery will reach 50% DOD in under an hour.
It is only a 1.2kWh battery. At the very most will take 2 hours to reach 100% DOD.
I have only remote connection, around 7 watts constant consumption.
Problem is that SoC does not correlate bat voltage. Is there some settings for that?
4 pcs Victron 12V/220Ah batteries, in paraller and in series, so 24V/440Ah altogether. Deep cycle should give me 80% of that, so usable energy storage around 350Ah?
7W or 0.3A is currently drawn, almost constantly. 24h x 0.3A = 7.2Ah per day, times 30 days equals 216Ah per month. Should drain batteries from full to empty, without any charging, in aprox 1,5 months. That it does, but still, soc does not correlate
You need to read up on the Peukert effect. A simple overview is a 100Ah lead acid battery will deliver 100Ah with a 5A current. With a 20A current it will deliver say 80Ah and a 100A current only 50Ah. When drawn down slowly, say at 1A you may get 140Ah and at 0.1A 180Ah. The battery monitor allows for this. At your very low current consumption, the effective battery capacity is much higher so SOC falls more slowly.
