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A Low Battery Voltage Switch


Mo Murphy

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Can you buy a switch that will cut the supply when a certain battery voltage is reached.

I want to leave my cool box running for as long as possible but I don't want to flatten the battery. I thought if I could find this type of switch then I could just leave the box connected all the time and the switch would cut the power before the battery gets flat.

TIA

Mo

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Guest diesel_jim

How about playing with one of the rear electric window cut off relay boxes?

my 200Tdi had one (with a 45amp alternator)... if i sat on tickover with lights/heater etc on full, the rear window would turn off. rev the engine it would come back on.

think i've got one in the garage somewhere. not sure if it's adjustable inside?

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PRC4427 keeps it all in the family and can be removed from a scrap Rangie if you're lucky.

It is adjustable if you pop the top off.

Edited to add: You'll need to use it to switch a relay though.

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Bit thick when it comes to electrics... would it be possible to use the maplin one to switch a relay in line with the 'sense' wire to my x charge? to stop the split charge working if main batt goes below 11.5v, if i just have the alternator connected to the main batt this will mean that the main will charge first then both right?

Mike

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Guest diesel_jim
Bit thick when it comes to electrics... would it be possible to use the maplin one to switch a relay in line with the 'sense' wire to my x charge? to stop the split charge working if main batt goes below 11.5v, if i just have the alternator connected to the main batt this will mean that the main will charge first then both right?

Mike

Yes, if you were to connect the voltage sense unit to your main battery, and have it's output controlling the x-charge relay, then if your main battery ever dropped to below 11.5v (or whatever it's set to) then the relay would open and just leave the main battery being charged.

however, an observation:

if your main battery ever did drop to below 11.5v when the engine was running, then i'd suggest your alternator was knackered. as they usually charge at about 13.4v

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Take a look at the Smartcom unit at Towsure - I've used one for the last two years and would highly recommend -

http://www.towsure.com/product/2973-Self-S...elay_Wiring_Kit

£13 and will power a second battery and fridge, and shuts off power to either the fridge or battery when voltage drops, then starts powering them again as soon as it hits a certain voltage. Very easy to install, I took a reasonably thick wire straight from the main battery into the input feed, then the same guage out to leisure battery and fridge. It has terminal block type connectors so a five minute job to set up and tuck out of the way, and it's very resiliant to knocks vibration and I've dunked mine under water a couple of times with no ill effect.. ;)

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