car Batteries

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=77557
Printed Date: May 14, 2024 at 5:58 PM

Topic: car Batteries

Posted By: cyruslam
Subject: car Batteries
Date Posted: May 10, 2006 at 7:55 AM

Hi everyone

I have a spare 12v car battery. i want to put into my car as a second battery to power the little 12v fridge.

I want to make a setup, when i start the ignition/engine of my car, both batteries on my car are being charged. And when i turn off, the second battery being isolated so that the frige wont use up the power on the main battery.

How can i connect the batteries? and how to make the above setup? can i do it with a relay?

Thanks a lot~~

Replies:

Posted By: mad550
Date Posted: May 10, 2006 at 8:21 AM

Battery isolator kit, most 4x4 shops stock them

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WOW Sight and Sound
Maroochydore
Nothing is impossible!
Do it right the first time or don't do it at all.

Posted By: ff-mike
Date Posted: May 10, 2006 at 9:11 AM

Another source for isolaters would be RV stores

Yes, it can be done with a relay, and using a relay will allow faster charging than an isolater which drops the voltage across it. The only issue would be if the battery was highly discharged then there may be too much current for the relay to handle.
30- Main battery positive
85- ground
86- ignition switched 12V
87- Second battery positive

Posted By: cyruslam
Date Posted: May 10, 2006 at 6:49 PM

Thanks for ur help.

no chance that i could DIY a isolator?

Posted By: mustangfoo
Date Posted: May 10, 2006 at 9:46 PM

read the above post, that is a DIY isolator, it is a bosch style relay that you would use on that

Posted By: cyruslam
Date Posted: May 11, 2006 at 3:32 AM

ic......Thx a lot~~

I connect the Second battery positive to 87, what about the Second battery negative?

Posted By: mustangfoo
Date Posted: May 14, 2006 at 3:49 AM

yup no problem bud

Posted By: cyruslam
Date Posted: May 14, 2006 at 3:55 AM

what about the Second battery negative? connect back to main battery??

Posted By: ff-mike
Date Posted: May 15, 2006 at 11:21 AM

Connect to ground, just like the primary battery.

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