Ok. So the reason I am asking is simply because I am wanting to have an idea of how to monitor health from battery voltage reading.
Ugh, I know what you mean, but "health" and lead-acid battery voltage readings are a misnomer. A fully sulfated old battery charges up real fast and can have a 13.8v at rest voltage reading, but when you put *any* load on it, the voltage crashes to 9v - so health - even though I know what you mean, is elusive without taking other things into account
I have a 37 watt draw constant. Overnight battery voltage drops from 12.7-12.8 to 12.35 or sometimes 12.2.
We can do the old-school way too with the power formula (P/I*E) (Watts/amps*volts)
Simply put, 37 / 10 = 3.7A constant current. The reason for using 10 and not 12 is a fudge-factor for inverter inefficiency. If you were to measure it with a shunt or clamp-on ammeter, you'd be close to this. Good enough for back of the napkin-calc.
Multiply this by time. I'll take an average winter of 12 hours (6p - 6am), so that's 3.7A * 12 = 44.4ah taken from the battery daily. Your solar system needs to be able to replenish that, and being lead-acid, 15-20% more being how this chemistry behaves.
So not exact values, but a demonstration of napkin calc.
Going to check, equalize and water this weekend and check SG for the first time ever.
Aha. Since these are flooded, if you are not regularly recharging with at least .05C you run the risk of the electrolyte stratifying. That is, differing values of acidity within the battery's depth because the electrolyte isn't getting stirred or gently bubbled as would happen in a mobile / marine environment naturally from movement.
You can visualize stratification as kind of like what italian salad-oil dressing does in a bottle just sitting around.
So here the problem is that if you walk up to your flooded 8D's, and take an SG measurement from the top, that will be far different than what is deeper in depth inside the cell.
Since nobody is around to mandhandle / paint-shake your 8D's <grin> , make sure you have at least .05C charging current to get the electrolyte to bubble and stir a bit. If your recharge current is lower, (common with solar and insufficient panel power) stratification can and does happen requiring manual intervention and maintenance.
Did I mention LifeP04 relieving one of these hassles?
