Thread: Aux batteries - Choices & options - Here's where I'm at ...

G'day Kev

Seeing that no one has yet commented,thought I had better get the ball rolling.I have just spent a few weeks looking for a dual battery setup for my Defender,and did a lot of research,whilst I am limited by the physical location of the battery in the Defender ie under the seat,most of my requirements would also meet your requirements.
I won't get into specific brands/model batteries as things like price and availability and warranty all come into the equation.
Having worked in the Automotive field for over 30 yrs and been involved with 4wds for nearly 40 yrs I have seen a lot of batteries fail.Now the funny thing is,aftermarket batteries never seem to last as long as the original fitment battery,even if the same brand and model is refitted??? Why I don't know,and many others in the field have also noted this phenomenon.
So I never try and get into the argument that Brand x will last longer than brand y.
With regards to Pb Ca batteries,they require a higher voltage to fully recharge than a normal normal Pb acid battery.It is not uncommon to have vehicles that come with standard fitment Pb Ca batteries to have a regulator output of over 14.5 volts.Also PbCa batteries require specialised battery chargers,to enable them to get to a full charge and prolong their life.Having not looked at the type of battery fitted to a D2 as original fitment,or checked the alternator output,I am unsure as to what is fitted.
Allowing for the best laid plans of mice and men,which we all know never seem to work out the way we plan.Looking at your scenario of time taken to charge your PbCa battery to only 75% capacity will in my experience, after a while lead to the battery prematurely failing,as they don't like to be operated regularly from a less than full charged state.
With the AGM type battery,you will get faster charging to its fully charged state,and depending on you needs is loads to be placed on the batteries,ie winch,fridge, lights etc you can run dual purpose batteries that will give high CCA as well as having the deep cycle ability to operate your other accessories.I ended up running 2 dual purpose batteries,due to having to operate my winch,and the ability with help from the SC80 and Marine switch to couple the batteries together if required.And also have enough CCA available in the 2nd battery to start the diesel in cold weather if the main battery happens to fail.The other thing with having 2 batteries the same is that,if 1 fails you can use the 2nd battery,and when you replace the faulty battery,it is just a matter of fitting into place .

Extended stays will remain an issue,no matter which way you go,as you say,solar panel are a pain to carry,especially as I hate roof racks.And carrying a generator and fuel has its problems in more ways than one.
But it is still easier to bring your AGM type batteries up to charge in a much quicker time,by running the vehicle for an hour or so per day,even if it was only running whilst parked,than it would be to charge the other batteries.
All this would be incidental if it came down to cost though

Wayne

Hi Kev, there is another option.

With the way the SC80 works, and that you mention leaving one battery and the fridge behind while you go for a drive.

You could, on returning from your drive, leave the battery and fridge out of your disco and using an inverter, a standard 240vac extension cord and small battery charger, you can recharge the fridge battery continuously with out ever needing to put it back in the disco.

Im pretty sure there is no right or wrong answer here and Im also pretty sure it comes down to personal choice.

However, here's what I do and its worked a treat for the last 10 years or so (multiple overlanding Defenders vehicles).

Shoe-horn 2 x Odyssey PC1700's into the battery box and use a decent, automatic battery management unit (I use a Swiss product from IBS).

Those batteries do fit (just), along with my HD winch solenoid, 4 x 40A relays and a 12-way aux fuse board and all necessery cables.

That setup will keep the fridge (MT17 Engel) and freezer (MT60 Engel) running for 1.5days without problems and using the fridge only alows me to pull up on a Friday night and drive home on a Sunday night. I also have some decent LED lights that I use in the back of the car at the same time.

HTH.
J

Wayne. Thanks for the thoughts.

"With regards to Pb Ca batteries,they require a higher voltage to fully recharge than a normal normal Pb acid battery.It is not uncommon to have vehicles that come with standard fitment Pb Ca batteries to have a regulator output of over 14.5 volts.
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The D2 comes std with a Pb Ca battery, and the alternator seems to charge at around 14.2-14.6 volts. It's a 950CCA (100AHr) battery, so it's no lite-weight!


Also PbCa batteries require specialised battery chargers,to enable them to get to a full charge and prolong their life.Having not looked at the type of battery fitted to a D2 as original fitment,or checked the alternator output,I am unsure as to what is fitted.
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I purchased a 21A battery charger that specifically has a setting for Pb Ca. Everytime you charge a Pb Ca battery on the appropriate setting, it does an equalization charge pushing the battery up to 16.4 volts. The aux' battery (wet Pb deep cycle) needs to be disconnected when I charge the starting battery ... but now with Tims USI-160, when the charger goes into equalization for the Pb Ca battery, at 14.8v it disconnects the aux' battery until the voltage drops to 14.4v .... don't have to worry about boiling the aux' battery anymore


Allowing for the best laid plans of mice and men,which we all know never seem to work out the way we plan.Looking at your scenario of time taken to charge your PbCa battery to only 75% capacity will in my experience, after a while lead to the battery prematurely failing,as they don't like to be operated regularly from a less than full charged state."
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Well, the cranking battery is probaly close to 7 years old now, and still seems to be in good shape (must be close to end of life though), and lots of short stop/start trips in it's life ... but every 4-6 weeks I always put my cars batteries on charge, which helps life expectancy .... the catch is the time it takes for that last 25% charge.


With the AGM type battery,you will get faster charging to its fully charged state,and depending on you needs is loads to be placed on the batteries,ie winch,fridge, lights etc you can run dual purpose batteries that will give high CCA as well as having the deep cycle ability to operate your other accessories.
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After much re-consideration, I think the dual AGM setup has more positives than trying to lug around a solar setup (which is basically deaed weight until you've stopped for more than 2-3 days ... it don't work whilst you're driving). I already have a 120A charger onboard!


I ended up running 2 dual purpose batteries,due to having to operate my winch,and the ability with help from the SC80 and Marine switch to couple the batteries together if required.And also have enough CCA available in the 2nd battery to start the diesel in cold weather if the main battery happens to fail.The other thing with having 2 batteries the same is that,if 1 fails you can use the 2nd battery,and when you replace the faulty battery,it is just a matter of fitting into place .
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I can't run identical dual batteries, but the smaller D34 optima is still enough to crank the Td5, and using Tims USI-160, I can bridge them from the in-cab controller for jump start/winching .... if I add a 3rd battery in the rear, then a second D31A Optima would be a double for the cranking battery.


But it is still easier to bring your AGM type batteries up to charge in a much quicker time,by running the vehicle for an hour or so per day,even if it was only running whilst parked,than it would be to charge the other batteries.
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With the 120A alternator in the D2, and Optima AGM's, 1/2Hr running would give me approx' 2days worth of charge ....

...... ouch .... A D31A + D34 ex Ebay delivered is $690.00 (cheapest I've found so far) .... Pb Ca equiv's would be around $435 .... but recharging them becomes the issue. They give more capacity when fully charged, but at 75% charge only give the capacity that I get from the AGM's at 100% charged.

AGM's it is. As the current batteries approach end-of-life I'll go that way.

Thanks for your informative reply.

Originally Posted by Fluids

After much re-consideration, I think the dual AGM setup has more positives than trying to lug around a solar setup (which is basically deaed weight until you've stopped for more than 2-3 days ... it don't work whilst you're driving). I already have a 120A charger onboard!

I would not totally agree here. I lug around solar. The more you discharge a battery, even deep cycle, the shorter it's life. So if I only stop for say one night and my battery capacity will alow me two nights, I still pull out the solar panel. I try to never take any more than 30% from my batteries.

I must say, you have done well to get 7 years out of a battery. These days you are going well if you get 4 years out of a starting battery.

Dave.

Evening Dave.

I'm not adverse to using solar, but setting up the D2 as a tourer for 3x, space becomes an issue, and we anticipate that we'll be going more day by day more often than not, with an occaisional 2-3 day stop over. Solar becomes a bit pointless for an overnight stop, the batteries are charged after a day of driving, and the useful sunlight has gone by the time we stop ... AGM's will allow a better discharge/recharge after a short days stop/start driving than the Pb Ca types, and if they can do an occaisional 2-3 day stop-over, then that's the best choice I believe .... I only need to run a 47L ARB fridge and a couple of LED camp lights. I get around 1.5 days on the 50Ahr wet cell deep cycle I currently have .... should get at least an extra day or two now I have Tims USI-60 installed .... with new Optima's I believe 3-4 days will be easily acheiveable. A 3rd Optima in the rear would maybe get to me 5-7 days ... again, with quick recharge time.

I'm sure the D2 battery is the original ... car was built 02/04 ... so that's 7.5yrs. I usually get 5-6+ years from a car battery (but always recharge periodically as "preventative" maintenance) .... D2 was a bit over 5yrs old when we purchased it.

I believe the Pb Ca batteries hold up really well to the bitter end, then fail without warning. Even at its current age, after a full charge & 12hrs idle, it reads around 12.65v.

I definitley agree with lower discharge, but space & weight are an issue, and I have to comprimise somewhere.

Ultimatley if I'm wrong ... it's a very expensive lesson

For me space is not a problem. I made a purpose built frame under my roof rack which is dead space otherwise. Obviously weight can be a problem if you are packed to the rafters as I think from memory it weighs 12 kg.

As yes I agree if you are driving every day you would not need it. Last Easter I did a trip with LROCV and we weren't sure if we were going to be driving every day so I took the panel. We did drive every day and I never used it.

Having said that if I was going bush on my own I would not go without it as it is good security if you ever got caught with a flat starting battery, and if your alternator died you could mount it on the roof and still be able to drive until able to get it fixed.

Dave.

Originally Posted by Mr Whippy

For me space is not a problem. I made a purpose built frame under my roof rack which is dead space otherwise. Obviously weight can be a problem if you are packed to the rafters as I think from memory it weighs 12 kg.

Having said that if I was going bush on my own I would not go without it as it is good security if you ever got caught with a flat starting battery, and if your alternator died you could mount it on the roof and still be able to drive until able to get it fixed.

Dave.

I looked at that idea, but because no.1 objective was to keep my overall height as low as possible, and because I used shorter (and modified) than reccomended Rhino legs for the cross bars, I have less than 15mm under the two rear crossbars ... and with the tray on the bars, there's lucky to be 45mm under the tray ... a panel might just squeeze in between the two back bars, but when I walk on the tray, it will deflect downwards and crack the solar panel glass ... all just too much effort for very occaisional use.

If I was going bush in 1 spot for weeks, then I'd just strap a folding panel on the tray with the other gear.

... I'm more inclined to look at a 3rd battery in the back if I need more capacity. I thought solar was going to be the answer ... if I had a 130, different story