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Old 16-01-2012, 07:22   #16
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Location: Fredericton, NB, Canada in the summer and fall; Caribbean in winter and spring aboard Cat Tales.
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Re: Why as low as 10V

I have one dedicated inverter that runs a cold plate (former charter boat). As I have new batteries and am turning over a new leaf about maintaining them, I grabbed the manual, and found that there is an adjustable potentiometer (wee little screw) that can be turned to raise the low voltage cutout.

I now have a low voltage cutout around 12.3 volts, as well as an egg timer set for 1/2 hour, when I turn this guy on. I usually run it twice a day, when the solar panels are creating more energy than the stereo needs.

I, too, believe nobody should take their primary bank below 50% capacity if they can help it. I recommend that we all grab the manuals for all devices that might have adjustable low voltage cutout capabilities, and start "turning the screws".

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Old 16-01-2012, 08:36   #17
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Re: Why as low as 10V

Yeah, but....

Don't confuse resting voltages and voltages under load when you're thinking about cutoff voltage. Consider these two facts:

1. a flooded lead-acid battery which has been resting (no load and no charging) for 20-24 hours and which measures 10.5VDC is just about dead. Most research on battery capacity uses 10.5 volts as the "effectively dead" point; and

2. a similar battery under a considerable load...say 10 amps or more....may display a voltage considerably below it's resting voltage (and, therefore, its true state-of-charge). Example: a bank of two Trojan T-105's totaling 225AH total capacity and under a 12-amp load will display a voltage of about 1 volt less than its resting voltage as it nears the end of the tests.

There would be a larger difference under higher loads. Example: a fully charged 100AH starting battery may display as little as 10.5 volts when actually under load turning the starter. And, after the engine starts, the battery will be about 99% charged (it only takes about 0.5AH to start the typical diesel on a cruising boat).


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Old 17-01-2012, 20:58   #18
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Re: Why as Low as 10V

I would crap my pants if I ever saw our banks below 12v. Under 12.5 makes me happy, 12.4 I'm okay, 12.3 better be under load. 12.2 and I'm sweating bullets.

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