Electrical Battery & Dual Battery Question

**CraigE** · 29th September 2017, 04:49 PM

Leading on from a previous post by another poster, my cranking battery appears to have died, will charge but not hold. Now I elected to replace it with a SSB 1000CCA 130 AH battery same as secondary battery. They just fit. What I did notice in the Defender is it has 2 large diameter earthing cables. Now originally they both went to the negative of the cranking battery. When the dual battery system was fitted one was fixed to each earth.
The set up like this kept showing a charge rate of 13v going to secondary battery, but all else worked fine.
When I changed the batteries I hooked them both back up to the cranking battery just to test.
Well the second battery now shows a charge rate of 14v same as cranking when being driven, but for some reason initially high beam would not work (low beam fine) and when they did start working seem to be really dull.
Got me stumped.

**trout1105** · 29th September 2017, 04:58 PM

Have you tried replacing the earths to their original position and running a fresh new cable to the auxiliary battery?

**CraigE** · 29th September 2017, 05:14 PM

Originally Posted by trout1105

Have you tried replacing the earths to their original position and running a fresh new cable to the auxiliary battery?

The cables are good. Might change it back tomorrow and put one of the large earths back to the aux battery.

**trout1105** · 29th September 2017, 05:22 PM

I am thinking that one of those dual earths that connect to the cranking battery is used for the headlights and fitting a separate new cable for the aux would fix your problem.

**bee utey** · 29th September 2017, 05:23 PM

Dual earth cables would suggest one to the engine/trans and one to the chassis/body. They should not be separated.

**CraigE** · 29th September 2017, 05:48 PM

Originally Posted by bee utey

Dual earth cables would suggest one to the engine/trans and one to the chassis/body. They should not be separated.

Might try earth to earth

**sierrafery** · 29th September 2017, 07:56 PM

IMO the dead battery had some internal short which caused a voltage drop on the whole setup and now with the good one everything is back to normal, also when different power batteries are used in a dual system this can happen due to the different internal resistance of the batteries so having similar batteries is the best choice... if it will still make tricks better replace the alternator's regulator cos it's quite common for them to fail and cause voltage drop under load ... see description: Land Rover Discovery & Defender TD5 Series 2 Alternator Regulator 98-06 - Starter Motor Repair Kits Starter Motor Repair Kits

**350RRC** · 29th September 2017, 08:32 PM

Originally Posted by sierrafery

IMO the dead battery had some internal short which caused a voltage drop on the whole setup and now with the good one everything is back to normal, also when different power batteries are used in a dual system this can happen due to the different internal resistance of the batteries so having similar batteries is the best choice... if it will still make tricks better replace the alternator's regulator cos it's quite common for them to fail and cause voltage drop under load ... see description: Land Rover Discovery & Defender TD5 Series 2 Alternator Regulator 98-06 - Starter Motor Repair Kits Starter Motor Repair Kits

Yep, Redarc used to recommend same batteries with their isolator which I have.

I had a brand new Exide aux battery go to an early grave alongside a Willow.

Now both Willow for 2 years and showing perfect voltage for my POS, hopefully for the next 10 years like the the last Willow.

DL

**drivesafe** · 30th September 2017, 06:13 PM

Hi DL, when using a DC/DC device or a battery charger, unless it is set up correctly, you can have problems when trying to charge disimilar batteries.

This problem does not exist when charging mixed battery types with an alternator.

NOTE, if you set up a DC/DC device or battery charger correctly, you can safely charge mixed battery types.

**350RRC** · 30th September 2017, 08:14 PM

Thanks Drivesafe,

I have nowhere near your expertise in these matters, just relaying my experience with batteries and isolators.

Do you have a view on why Redarc would have suggested using similar batteries in dual set ups?

Also...... the Exide was only earthed to the body, whereas the much older Willow was obviously earthed to the body, chassis, etc as the main cranking battery.

Would this have caused an issue? Have noted the earlier post about common earths.

cheers, DL

Thread: Electrical Battery & Dual Battery Question

Thread Tools

Electrical Battery & Dual Battery Question

Tags for this Thread

Bookmarks

Bookmarks

Posting Permissions