kimberlysmoore wrote:
I've looked online for an audible house battery low warning system and the things that pop up are confusing to me. None of them seem like what I'm looking for..a simple, inexpensive, audible warning when my house batteries get to 50%. I have lights that tell me a general guess but checking them is not always an option and sometimes the "deadly drain" will happen at night when we are sleeping. ...
We have one. Not this, but similar:
Voltage Meter with Alarm ($11 at amazon.com).
However, there's an issue that I haven't solved yet, so maybe I can add to the OP's question. Say you don't want to drain the battery to more than 50% (which is about 12.1 volts). But that value occurs when the
resting voltage is 12.1 volts, not when the voltage
under load is 12.1 volts. So, I thought I'd just develop a table showing the relationship between resting voltage and voltage under load. That, however, is was way harder than I thought it would be. For example, turning on the roof fan causes the voltage to go way down momentarily (due to the starting current of the motor) even though the battery was nowhere near drained. Even measuring the under-load-voltage for simple things (like the interior lights), has yielded a couple pages of notes and no clear relationship between state of charge and under-load voltage. I've also spent a fair amount of time online and haven't found a good source of information.
So in addition to pointing the OP to the right alarm, for those of you out there with alarms and some technical savvy, what voltage are you using and how was it determined?
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