Battery Test

Well it's me again - new to all of this and certainly appreciate the help. I am wondering how to test the state of the battery charge. I am hooked up in the yard still and I put a 4 yr old deep cycle in the unit after charging in the house

When I hit the test button just below the sink, all 4 of the battery lights light up. I am thinking that this means the battery is fully charged and that if it started losing its charge, the green light would go off, then the yellow etc

Is this correct or should only one light be lighting up to indicate the state of charge? Sounds like a stupid question I know but as I said this is all new to me

thanks in advance for your help

jimBOW - Bow Washington

[ZekenSpider]

As best I can remember, what you described is correct. A fully charged battery should show all four lights....but, if you have the "shore power" cord plugged into the house/garage outlet it will show all up to green because the TM 120VAC to 12VDC converter/battery charger will be supplying the TM with 13.7 VDC instead of the batteries 12.5 VDC.

To test the battery state of charge you need to unplug shore power, wait about an hour and then look at the light display. A fully charged battery will be all to green. If you have a volt meter and are handy with electrical measurements you can verify the battery voltage. A fully charged battery will read about 12.6 VDC, a battery that is discharged to a level that needs recharge (50% of full) (red light) will read about 12 VDC. If the voltage goes below 11.5 VDC it is dangerously low and may result in damage that cannot be recovered from.

State of charge is difficult to measure, but if you assume the battery is something like a Group 27, it will have about 100 Amp-Hours of energy when fully charged. If you disconnect shore power and then turn on the porch lamp which draws about 1.5 Amps(assuming it is a standard lamp and not an LED) and run it for 24 hours, the battery will lose 24 x 1.5 = 36 Amp-Hours or about 1/3 of it's charge. The battery voltage should drop down to about 12.2 VDC and only the bottom two lights will be on when you press the test button. If it drops more than that or faster than that, the battery may not be holding a full charge.

The TM also has some small current draw all of the time (called parasitic load by some) even though everything is off. It is about 0.3 Amps continuous.

There is more to this of course and you can find out much more when you can access the full Forum. You will find it is well worth the $12.00 to join.

Hope this is some help.

Jerry

Great, thank you for the info - it is appreciated -

jimBOW