how do you prevent draining the aux bty?

Submitted: Friday, May 28, 2004 at 08:38
ThreadID: 13232 Views:1471 Replies:4 FollowUps:3
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the aux bty (exide extreme 86EX) is now all wired up & lead run to the back for the fridge.
one final question .... how long should i let the bty run (ie power the fridge in this case) before it will cause damage to the battery. i know roughly that the bty has a reserve capacity of 180 (25A for 180' = 2.5A (Engel) for 15hr), but should i be disconnecting the load when the bty reaches a lower voltage so i don't stuff the bty? should i have a special gizmo in the circuit that disconnects the load when a lower voltage is reached?
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Reply By: Wayne (NSW) - Friday, May 28, 2004 at 09:19

Friday, May 28, 2004 at 09:19
Drew,
I belive that the Engle will stop running when the battery gets to 10.5v and that is about as low as the battery should be run down to.
Low voltage cut off switches are around and that would help save the battery if you are running a item that does not have a low volt cut off. I was thinking of a fluro light, they take a little to start but will run on just about nothing (.7amp) and if left on long enough will flatern the battery.

Wayne
AnswerID: 60562

Follow Up By: DrewT - Friday, May 28, 2004 at 10:02

Friday, May 28, 2004 at 10:02
the instructions that came with the engel only say "Should the DC voltage at the fridge input terminals fall below 10.7 volts, the cooling efficiency will immediately be reduced" ... i understood that to mean it will keep drawing power but won't be as efficient
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FollowupID: 322150

Follow Up By: Leroy - Friday, May 28, 2004 at 10:03

Friday, May 28, 2004 at 10:03
I have found my Engle will keep running even when the battery gets below 9v! You shouldn't discharge your batt below 10.5v which equates to 1.75v per cell. I have purchased but not installed yet a Piranah batt monitor that will cut out at 10.5v. The also sold one that cut out at 11.5v which is a little safer for your batt!! If you have a Waeco they have an inbuilt cut out a 10.5v.

Leroy
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FollowupID: 322151

Reply By: Magnus - Friday, May 28, 2004 at 10:04

Friday, May 28, 2004 at 10:04
Drew.

I agree with Wayne. If you are worried, get a low voltage cut off device. They do work and can save grief. Also get a voltmeter, available ex Jaycar, so you can monitor the aux batt voltage level.

Also visit the Panasonic web site. They have probably the best explanations of how lead acid batteries work and how to treat them especially Valve Regulated Sealed Lead Acid types. However the info applies to all lead acid batteries.

And add a solar panel to pump in some juice during the days you are not running the car or a gen set etc etc.

Have fun

Magnus
AnswerID: 60570

Reply By: Member - Jeff M (WA) - Friday, May 28, 2004 at 12:39

Friday, May 28, 2004 at 12:39
Yes, those digi volt meters are great, I got one from autospeed.com it cost me $39 and it has a blue backlight and inside, outside temp plus a clock and volt meter. Bloody excellent. It'll beep at you when you'r bat level get's to 11.5 volts. IMO that's getting flat, I can run my thristy 45L Waeco Cooler (draws 4 amps continously) for 18 hours, with lights, CB, GPS (with backlight) and MP3 player and it only just drops below 12v. I'm running a 85a/h Deep Cycle.
AnswerID: 60602

Reply By: DrewT - Friday, May 28, 2004 at 18:10

Friday, May 28, 2004 at 18:10
went to Jaycar today. all they could suggest was a $35 "automotive battery protector kit" which was rated to 10A max, looked a bit flimsy, & you have to assemble/solder yourself anyway (not a good option with my soldering skills ... i'm more of a weld - grind - reweld - grind - lots of paint .. kind of guy!!).

rang an auto electrician & he couldn't think of anything that would do the job

didn't think it would be that hard to find what i thought would be a common item! surely most folks would want something like this? (especially something that automatically opened the circuit to the load rather than just beeped at you in the middle of the night!!
AnswerID: 60670

Follow Up By: Utemad - Sunday, Jun 20, 2004 at 15:04

Sunday, Jun 20, 2004 at 15:04
Well if you wanted you could get one of those things that goes 'beep in the night' and hook the beeper up to a relay of some description instead. This relay could then control a relay of any size you like to control everything connected to your second battery.

Utemad
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FollowupID: 325201

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