Dual battery setup

Steve what are you running from your auxilliary battery?

Steve, just as a matter of interest, for 30 minutes running for two days, and two hours the third day, you would have at best put back 20 amp hours. With the battery being close to flat by the third day, I would estimage the figure of 20 amp hours to be reasonably accurate. At most it would probably be 26 amp hours.

Your alternator does not charge 80 amps into the auxillary battery. On the first day of driving around for 30 mins as the battery was not to flat you probably got in the 30 minutes driving 8 amp hours, on the second day, 4 amp hours and on the third day due to the battery now being close to flat 8 amp hours, and at best 14 amp hours.

To charge a second battery at full alternator capability requires a totally different system.

An independant charge isolator (like the Rotronics RFC12 or better) would cope with your situation better, but even so, if you've nearly flattened a battery then the alternator won't do much to bring it back. If your only using an alternator to recharge then try to avoid going below 11.5 volts (measured with load off).

A flattened battery needs a mains charger and many hours to bring it back to full charge.

An alternator will only charge a battery to about 80% in any case.

A good investment is a decent charger (eg 8 amps DC - 12 amps RMS) that at least has an auto cutout - but don't leave it on for days.

Hi Steve, I can't fully answer your question without having more info as OzExplorer has explained, however here are some useful web sites on batteries, charging cycles & isolators you might find of interest to give a better insight to your problem.
www.batterytender.com
www.uuhome.de/william.darden
www.surepower.com/ebrochures.html
I myself run a 40amp Rotronics charge unit to my deepcycle battery bank & a 600amp rotary isolating switch between start & aux batteries. It is a fail safe method of making sure the start battery is isolated when engine is not running. (i.e provided you don't forget to switch it over!!!)
Cheers.

Hello steveA I am thinking of buying the same system as you but now I wonder will I have the same problem as you, I will be running a waeco 52lt have been quoted $810.00 fully installed in my 80 serries petrol.did you not go back to the people and complain they told me that it would be peace of mind fitting this system.

Hi Stev
One of the problems is the type of battery you are using. From experience it takes 5-6 hours to totally recharge a deepcycle battery. The two solutions that I have come across are:
(1) I use a 32 watt solar panel (flexible type,easier to sore) to help keep the battery up.
(2) Seriously considering going over to a exide coil battery which only requires 2-3 hours of running. One problem they are only 55 amp hours and are about $350
So far the solar panel is working well
Ray

Hi Stev
One of the problems is the type of battery you are using. From experience it takes 5-6 hours to totally recharge a deepcycle battery. The two solutions that I have come across are:
(1) I use a 32 watt solar panel (flexible type,easier to sore) to help keep the battery up.
(2) Seriously considering going over to a exide coil battery which only requires 2-3 hours of running. One problem they are only 55 amp hours and are about $350
So far the solar panel is working well
Ray

hi stevea,

I have the same one fitted to my GQ and I had the same problem, mine got replaced under warranty.
I pulled apart the second one to look inside, I was quite alarmed at what I found. The unit is just a box with wires sticking out and some smart electronics inside. There were two issues I saw. Firstly from the outside, the main power cables, as they enter, do not have any sort of weather protection. You have a gap around the cables thru which dust/water can pass thru. Secondly, they use open relays in the electronics. Coupled with the gap around the cables, dust/grime/moisture fowl the contacts. End result is your aux battery is not being charged.
Quick and simple fix, seal the gap with silicon sealant.
If your unit is out of warranty, try this. Pull the unit apart. You will notice several relays, use a sensitive brush and clean the contacts with metho (don't use turps or anything that leaves a residue) and alow to dry.
This may not be the cause of your problem, but its a start.

Good luck.