Originally Posted by zboss
But that seems to be one of the questions... 50% of what? From a volts perspective:
12.73 volts is 100% full
12.10 volts is 50% full
For flooded batteries at 80F fully rested/disconnected for at least 24 hours (it often takes longer) this may
be accurate but will be brand dependent.
I have two AGM's on my bench that have been there for three weeks 100% disconnected still at 12.97V... Shop is about 70F..... The flooded battery next to them has been off charge for two weeks and I just checked it at 12.76V
Originally Posted by zboss
From an amp perspective my 520 Amp-hour banks is:
100% charged at 0 amp-hours consumed
or 50% charged at 260 amp-hours consumed.
Unfortunately it is not that easy..
Your 520 amp hour bank can be considered full
when your battery voltage under alt or shore charger
is at 14.4V + (NOT FLOAT VOLTAGE!) and your net accepted current is less than 2% of bank capacity, but 1.5% is a better number to strive for.
his means (with charge source in absorption mode):
Battery Terminal Voltage Measures 14.4V or greater
Ammeter shows 7.8A or less flowing into the batteries
The bank can now be considered
Ah's consumed at 0 tells you nothing other than the monitor thinks
the bank is full and is most likely misleading you..
What was the temp during discharge?
Whats is the charge efficiency of the bank?
When was the bank last capacity tested and the Ah capacity adjusted?
What is the Peukerts constant for the bank?
The rate at which you drew the capacity from the bank changes the SOC. So 260 Ah's consumed may not always be 50% SOC.
Draw 260Ah's at 200A and you will not be at 50% SOC
Draw 260Ah's at 4A and you will not be at 50% SOC
Also your 520 Ah bank is only a 520Ah bank for a short period of time. What is the real capacity?
I could go on and on and on.....
The only time you know you are full
is when a shore charger
or alt is at 14.4V+ and your bank is accepting less than 2% of capacity in charge current but preferably less than 1.5%.
If the bank was truly full it would look like this:
That is 0.1A acceptance on a 400Ah bank at 14.4V..
A good cheat is to charge to full then draw 40-50% of the capacity at a fixed current = to the 20 hour rate ("C" / 20 = 20 hour load) when the batteries are at 75-80F. Try to hold the current as steady as possible to not inflict any Peukert effect.
Stop and let the batteries rest for 24-35 hours 100% disconnected, still at 75-80F. What is the open circuit voltage? Does it agree with the SOC you should be at? If not a full capacity test is in order.
If you have solar
and an Ah counting battery monitor please STOP relying on "auto-synch". Use only "known full" resets, 14.4V+ less than 1.5%, and program out auto reset....... Manually resynching the monitor is the only way to maintain any semblance of accuracy with an Ah counter and solar/wind...