Low voltage disconnect switch

sarabande

sarabande

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Having (I think) knackered a battery by allowing the top-up solar panel to fall over and fail to re-charge, I am considering the use of Low Voltage Disconnect switches to isolate a battery if the V falls below a pre-determined (choosable) figure.

The floppy solar panel problem is solved with hi-tack adhesive silage tape, but can I tap into (electrical joke :) the forum's experience in the value and effectiveness of LVD switches please ?

Or is there a real case to be made for using ordinary ON/OFF battery switches (the red T ones) so that when leaving the boat, the small 10W panel is securely connected only to the battery that runs the bilge pump and entry sensor, with all other batts isolated ?


Thanks in advance.
 
First question, what discharged the battery ?

Whatever that is, you may need to consider isolating it, if you can.

If you think it's the bilge pump or entry sensor, you could possibly connect those to the solar controller load terminals and have those disconnect at a preset low voltage, if your controller allows this.
 
One of the problems we have when we leave the boat in Greece for the winter is finding all those annoying little things that draw from the batteries and might be enough to outpace the trickle chargers. So we check for LED indicators on the regulators; odd little circuits that have a standby mode and anything else we can think of that requires even a little bit of current. One such device is a low voltage detecting switch. I've made a couple and ultimately thrown them away simply because they add to the problem rather than provide a solution. There was a circuit I published in July 2013 PBO for an alarm which could be changed to a switch by adding a relay - BUT - the relay would have to be held on so that it would default to off when the voltage dropped and holding the relay on would add to the drain. Semiconductor switches would be better but the philosophy still applies - you have to take current from somewhere to run the detector. I would recommend doing a measurement of the current drain and calculating how much you will get from the solar panels and see how it balances out. The solar panels article is still on the PBO site I think to show you how to calculate the energy you can get http://www.pbo.co.uk/solarpanels.
 
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