Battery Protector

BrentB · Posted: Mon Nov 30, 2009 4:27 pm Post subject: Battery Protector

This was discussed in another thread but today I found this and plan to install on start battery unless someone has another suggestion.

Battery voltage and starting power are monitored while the engine is off, and the draining load is automatically disconnected when voltage falls below 11.7 volts.
Complete battery discharge is prevented while holding reserve power for engine start up.

http://www.awdirect.com/battery-protectors-priority-start-standard-series-12v-psi-dp-12v/battery-protection/

thataway · Posted: Mon Nov 30, 2009 5:56 pm Post subject:

They certainly work, but the question I have to ask is are they necessary?
I have owned ocean going vessels since 1962, and 5 years before that outboard boats from 13 to 16 feet, which I cruised on the Gulf Coast ICW without a single time when I didn't have enough battery power to start an engine. The key is planing and battery monitering. Planing is having enough battery power--that means in a C Dory 16 to 25 at least 2 batteries, a transfer switch and a good volt meter. I have kept a small U1 or PWC start battery as a reserve, but never needed it. I moniter my batteries, and don't let them drop below 12.2 volts. If a battery were to fail--which can happen--then you have the other battery, or even the small and cheap U1 battery, which has enough power to start most our our engines. At a resting state, 11.7 volts is about 10% charged, or 90% discharged at 68 degrees F.

There may be another issue--this seems to be for constant loads, and when the constant drain causes the voltage to drop to 11.7 (pretty much a dead battery), then it disconnects. The PDF says that a draw of 2milli amps will restart the flow of current--I suspect that if you had refrigration where the unit cycles on and off, that this could be enough to allow current flow again--further discharging the battery (some ref units also have a voltage limiter). There is also a small parasetic draw of the electronics and LED of the unit, which further discharges the unit.

BrentB · Posted: Mon Nov 30, 2009 7:20 pm Post subject:

I was thinking they were a backup to a voltmeter

Doryman · Posted: Tue Dec 01, 2009 4:32 am Post subject:

I ran my batteries down twice (OK I am a slow learner!) by leaving the keys in the ignition in the on position (but with the engines not running.) I would have avoided some embarrassment had I had something like this installed. Now I have trained myself to remove the keys from the ignition immediately upon shutdown.

Warren