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Directory:Batteries:Most Ah ratings are incorrect
In Reference to Bettery Involvement in John Bedini's "School Girl Radiant Energy Circuit and Motor"
Most Ah Ratings are Incorrect
From: "roamer1952004" <firstname.lastname@example.org*t>
Sent: Tuesday, October 26, 2004 2:05 PM
Subject: [Bedini_SG] Most Ah ratings are INCORRECT
Most lead-acid batteries are MISlabeled with a higher Ah rating than what they really usefully contain.
UNLESS you get a true deep-cycle battery, you're not getting what you expect.
Gel-cells are usually WAY overrated on useful Ah. The rating on the battery probably also includes the BTU's you'd get if you were to set it on fire after you powered your load with it.
For any "regular" lead-acid battery with a CCA rating, just divide that CCA number by 20 and you'll have it's true Ah capacity.
But, STARTING BATTERIES are not deep-cycle worthy. So, you can only have the first 20% of that CCA/20 figure without damaging that battery. As an example, a 600 CCA battery has 600/20 = 30Ah. Then take that 30Ah/5 = 6Ah of usable charge without damaging the battery.
Short answer is, DON'T bother with starting batteries, except for STARTING things.
Just buy deep-cycle batteries and be done with it for your storage bank needs.
In any case....
You don't need a lab to know approximately what you can get from a battery, just a CONSTANT CURRENT load.
Electrical charge is defined in measured quantities of electron charge called COULOMBS.
"Charge" in a battery is defined as Ampere-hours.
ONE "ampere" is defined as ONE COULOMB PER SECOND of "flow".
So, you COULD write this as (Coulombs per second)-hours.
"Ah" is much simpler.
Forget the "voltage" except as a starting and finishing point measurement. The batteries are rated in Ah NOT Watt-hours. Ah only considers the COULOMB content of the battery, not the voltage at which it is released.
1. Start by using 80% of your Ah rating as your REAL USEFUL CHARGE CAPACITY. This means a 100ah battery should be considered an 80Ah battery. Got it? Good.
2. Divide that 80% number by 20. So it's 80Ah/20 = 4 amperes. You can draw a steady 4 amperes for 20 hours from a 100Ah battery without damaging it.
3. Apply the 4amp load to the battery for 20 hours. Then remove the load and see where the battery voltage pops up to.
If it's below 12v, then the battery's labeled rating is wrong.
Recharge the battery with a charger that can get it's voltage up over 12.6v within a couple of hours. If it takes longer than that to get over 12.6v, the battery is already beginning to sulfate.
- Battery Characteristics - listing as part of the Bedini SG project.