Low Voltage Alarm

[Sonosailor]

I did a search, and this does not seem to be covered.

Anybody recommend a good, simple low voltage alarm? I've been in the marine catalogues, and looked up and down the rows, and can't seem to find much. Don't we all want a little buzzer when our primary bank goes below a certain capacity?

Me, I'd want an adjustable setpoint too.

[Ziggy]

Try this: DC Digital Voltmeter with Alarm - PN 8251 - Blue Sea Systems

[Sonosailor]

Thanks, Ziggy. Blue Sea is typically good stuff. At $210, it is a little steep, though.

Any others out there?

[DeepFrz]

Sure, here is one for $310.
http://www.cruisersforum.com/forums/...tml#post870404

Google works well...

[hellosailor]

Sono, if you can solder...there are single-chip IC voltage controllers and regulators that have low-voltage alarm functions built into them. Typically an under $5 chip, and another $5 worth of parts, with the circuits given in the data sheets for the chips. I don't recall specific chips to look up but a call to Digikey or Newark, etc, should turn the up for you. And best of all, they consume flea-power, micro-amps, in operation.

[CarlF]

Big thumbs up for the Victron 600 battery monitor. This monitors a large number of electrical system items and you can program thresholds for many items to turn on a relay (which could have a buzzer connected). Low voltage can also set off an internal buzzer alarm so you can have two different alarms for low voltage set at different alarm thresholds if you want. You can also set an alarm for percent of charge which may well be a better alarm item. It's about $160. The manual can be downloaded from Victron Energy's website.

Victron BMV 600 Battery Monitor

Carl

[Ziggy]

That looks like an interesting product, Carl

[Sonosailor]

I finally purchased a little $30 battery minder from Batterystuff.com. It works rather well. Of course, the true reading of a battery happens only if it is left alone for 24 hours, making it all a little silly. Well, too silly to spend 7-10 times as much for a marine battery monitor, anyway. I'm happy. I mounted it in a highly visible place, and find myself checking it regularly. I am more aware as to what is running, whether the wind is blowing the windmill, the sun is hitting the panels at a good angle, and if the alternators are working.

[Andina Marie]

We sold 3 bank low battery alarms for many years for about $45 but there was so little demand it did not justify continuing it when one of the components became obsolete and it needed re-designing. In the last 15 years more and more instruments included a low voltage alarm (even if it was just that the instrument shut down) so demand dropped off to a trickle.

[Lake-Effect]

A dependable panel meter will help you monitor the battery. Ours is a good-quality expanded-range analog meter (measures from 10 to 15 volts), and I can tell when it's getting low.

As suggested, it's not hard to make simple inexpensive low-voltage alarm. This one is about as simple as they come. As long as it has an OFF position

This ebay seller in the UK has some interesting 12v monitors, some with alarms.

[goboatingnow]

Using a voltmeter to measure the state of a battery under load is very misleading.

Dave

[Lake-Effect]

Originally Posted by goboatingnow

Using a voltmeter to measure the state of a battery under load is very misleading.

That's true in general, so yes, an alarm with a set voltage threshold might not be that useful.

Under light or no load, like when you first come to the boat, voltage is still a useful check. Also, when you get used to your boat's batteries and typical voltages under known loads, you will see when something's amiss.

[Sonosailor]

Originally Posted by Lake-Effect

That's true in general, so yes, an alarm with a set voltage threshold might not be that useful.

Under light or no load, like when you first come to the boat, voltage is still a useful check. Also, when you get used to your boat's batteries and typical voltages under known loads, you will see when something's amiss.

EXACTLY!

[SailFastTri]

IMHO, a low voltage disconnect on the circuits that control refrigeration or lighting is much more useful than an alarm. The LVD should be set for around 11.9v or 12.0v so you don't run your batteries dead flat. I'd rather spoil some food or have warm beer than destroy the house bank.

Of course, the bilge pumps should not be limited by the LVD, and I think it's better to have an audible alarm on those pumps.

[RUSTYNAIL]

What ever you get, get a low/high voltage alarm with a delay that will allow a bilge pump or something else to cycle on for 10 seconds w/o alarming. If not, you will need to set the alarm set point too low.The good digital meters with an alarm have the delay in their alarm feature. You will sleep much better once you get a low voltage alarm. It can let you know that your bilge pump is constantly running due to something like a stuck float switch.