Second battery to combat line loss?

[velacreations]

I've got a 12 volt fridge about 40 feet from my batteries with a 10 AWG line running to it.  The fridge pulls 10 amps when running, and I experience a 1v voltage drop.  The problem is that this triggers the low voltage disconnect on the fridge when the batteries are below 12.6.

Would it be possible to add a smaller battery close to the fridge to reduce this loss?  I'd put in a one-way diode to prevent discharge, but I would think that the smaller battery would trickle charge, and then provide enough of a voltage boost to keep the fridge running.

Anyone have experience with a solution like this?

[dnix71]

A boost cap array like the kind used to buffer remote mounted car stereos would be more efficient, but if the line losses cause failure during run time, then the only proper fix is bigger wire.

http://www.ebay.com/itm/Boss-Audio-Cpbk3-5-3-5-Farad-Capacitor-Black-BOSCPBK35-/400579598237

This audio supercap is plug and play.

[velacreations]

yeah, I'd really hate to have to pull all that wire and change it.  Something like a cap might work, but would a battery also work?

[Mary B]

Wire is cheaper but they do make a battery voltage booster http://www.hamradio.com/detail.cfm?pid=H0-008745

[OperaHouse]

Caps would never provide a long enough surge for a compressor start.  Generally the low voltage detect ignores that initial surge anyway.  You need bigger wire to prevent the voltage drop or an additional parallel wire run.

[velacreations]

yeah, it's not the compressor start that's the problem, it's the running of the compressor for long periods.

I know changing the wire is the best solution, but it's one heck of a job to change the wire, so I'm looking at other possible options right now.

so, a second battery close to the fridge won't work? 

Also, to change the wire, I assume I have to change both positive and negatives, right?  If I added another parallel positive line, that probably wouldn't do it, right?

[Frank S]

to parallel your wire you need both the + &- wires.
 Placing a battery close to the fridge would do the trick providing the battery is large enough to run the fridge.
 electricity is going to take the path of least resistance. so paralleling a battery close to the fridge will only result in most of the draw coming from it.
 Connecting the fridge directly to the near battery and the #10 ga wires from your bank with an idolater or diode to prevent the bank from drawing from the fridge battery would be the way to go IMO.   

[oztules]

"so, a second battery close to the fridge won't work?  "
Yes it will "work"... not the best result, but will cover the cracks in your system..... I favor the direct connect... no diodes no nothing.... else you will get another .7v drop through the silicon.

So first try is to just dump another battery next to the fridge, and see what happens.. it should charge when there is no fridge action, but a lot of things will influence this.... suck it and see is the only way to know for sure.


.................oztules

[velacreations]

ok, was going to put a battery over there to test. Behind the fridge found an open conduit, so added another parallel 10 awg, and the fridge is running fine now, still see a voltage drop of about .4 volts, but that should keep it well above the low voltage trigger.  I'll eventually replace that with a 6 AWG, but I had 10 laying around.

I know a parallel string is not as good as replacing the whole wire, but it's certainly better than the battery over there.