Great tips Bill. Thanks. I *finally* found a receipt for the battery. It's a "12V 45AH Sealed Battery". I called the vendor and found out it's an AGM battery. It's holding it's charge longer. 2 hours with DVD player via the inverter and it went down to ~60%. The bulb load test makes sense and is a good tip, but I really should learn how to use my digital VOM to test current draw. I know that one should use hard numbers to measure things. Cheers, Neil. On Thu, Sep 4, 2008 at 8:44 AM, Bill Prats <b.bill.p@gmail.com> wrote: >> 3. Did I hurt my Aux Battery? > > I have a large ham radio and have lots of battery experience, some of the > brands don't last more than a few years. Here is any easy way to test the > capacity of a smallish battery. Wire a tail light across it by itself and > time how long the light burns a decent glow. Since the wattage is on the > bulb you will get a good idea about the condition of the battery. Power in > Watts = Voltage times current. 6 watt bulb on 12 volts draws a 1/2 amp, 12 > watt lamp on 12 volts draws 1 amp. 24 watt lamp on 12 volt draws 2 amps. > A 100 watt sound system full on will draw around 9 amps and more depending > on other features and volume level. A older 40 amp hour battery might be > good for 2 hours in my opinion. > > Try not not to drain any battery below 11.5 volts, that level varies by > battery but its generally accepted as the bare minimum before the battery > plates warp and short together, bad news. > > Its possible the battery is ageing and the sound system draws far more power > than estimated. Put an amp meter in series with the system to measure. > > The only sure way to find out the battery chemistry type is to research the > brand/model number. Sometimes a deep cycle/gell or AGM will weigh a few > pounds more than it automotive type cousin. Well at least you get a rough > idea. I have the same problem, a 55 amp battery that weighs a ton. > |
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