Low voltage disconnect help.

[bunce1260]

Hi.
I've installed my second battery which is being charged via an isolator when the vehicle is running. I've got an electric blanket for keeping warm while we sleep and therefore unable to monitor the battery. To prevent me from ruining the battery I'd like to install a shut off that happens automatically at a given voltage ( I don't know what that voltage is, whatever stops me from ruining the battery).
That doesn't sound like a terribly complicated part but I'm finding prices in the $60 and up range like this one http://amzn.to/1moekBl . When I do a search lots of solar charge controllers also come up like this one http://amzn.to/1PhGI2j . Can you use these for my intended purpose? They're considerably cheaper but don't seem to mention the shut off as a feature, maybe it's just built in.

Please school me. Thanks

 

[crusaderJK]

How big (in Ah) is your second battery? And is it a deep-cycle battery?

The solar charge controller does have a low voltage cut-off, but with 11.1V I think it's a little on the low side for your usage.
It's okay for a deep-cycle battery to be discharged that low once in a while.
But heated blankets draw a lot of power and you don't want to run your battery down to 11V every night.

 

[Chris Boyd]

I've used something similar to protect a radio from high transient voltage, but it also has a low voltage cutout at 11v. Fully automatic, rated for 40A and bulletproof.

http://www.westmountainradio.com/product_info.php?products_id=pwr_guard

 

[Chris Boyd]

The cutout on this is also 11v, which for deep cycle batteries isn't an issue.

I've never thought of using an electric blanket but this has me thinking... Where did you find a 12v electric blanket?

 

[plh]

Look into the: Automatic Power Off (APO3) - it has adjustable voltage shut-off points 11.8, 12.1, 12.7, 13.05 VDC - also about $60 on Amazon, down side is that it can only take a 20 amp draw - but that is probably way more than enough for your electric blanket.

http://www.aprsworld.com/apo3/

 

[bunce1260]

This is the battery I bought - http://amzn.to/1PibLey It's a 110Ah AGM battery.

I think the blanket is the same as this http://amzn.to/1Pic2Op .

It draws 4 Amps, It's not going to make us hot by any means, but will take the chill off. Driving back to Indiana for Christmas we had a night it the van at 14 degrees, I wish this was all hooked up then, it was a bit chilly.

That West mountain radio one is rather expensive, I was hoping to not spend a small fortune on this, I didn't think it would be an expensive part to be honest.

 

[Haf-E]

Looks like that electric blanket has "a patented 30 or 45 minute safety timer with auto shut-off" - so I don't think a low battery voltage cut off is necessary...

BTW - I have used a 12VDC mattress warmer pad that goes under you - it works better and it stays in one place (more or less) and heat rises - works great with a sleeping bag over the top and a good mattress pad underneath. Here is the supplier I recommend -

http://www.backwoodssolar.com/12v-bedwarmer-twin-size

This one doesn't shut off after 45 minutes either!