Maintaining Batteries...?

Hello and some questions regarding battery use/recharging when free-camping...

I run a N.Patrol with dual batt setup (AGM 100Ah Fullriver) at rear that drives a Waeco 50L (on Freeze) and HF Radio (intermittent). I'm having an AGM 120Ah fitted to my 17-55.3 Jayco Dscvry - presume will "run" from existing Setec in the van?? (I have no idea if that batt will 'charge' from the vehicle alternator when on the move..?)
So I will have a triple batt setup when I arrive at Stuarts Well on April 23rd.
(1) Vehicle Crank Batt
(2) Rear Tug Batt - charged from alt and isolated from crank batt
(3) 120 Ah AGM in van (charging and distribution as yet unknown)
Q's: So how do I maintain the charge on Batts (2) and (3)..??
Enough to keep Waeco at freeze level for 4-5 days... (That's the big one... from (2) the AGM in the rear of the tug...)
And enough to provide lights and radio/??TV news (3) in the van...
I see three options:
Genny - smelly noisy things - not welcome in NP's...
Solar - costly fiddly things... 26 degrees - solar tracking - Nah...
Vehicle Alternator..?? - So is it realistic that I can plug the van into the Patrol via the 7 pin for an hour and actually recharge/top-up the van batt...
How many hours/kms would I need to do daily to keep the 100Ah AGN in the rear of the tug topped up to keep the Waeco running on freeze..?
Just learning the basics..

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Reply By:- Sunday, Jan 31, 2010 at 00:04

Sunday, Jan 31, 2010 at 00:04
Your batteries inside the Patrol will be charged by the alternator, as long as you're cruising along. Fridge draws only a couple of amps in average, which will be chickenfeed for the alternator. So these two batteries will be sitting at around 13.8V for much of the time.
I'm not sure how the van battery gets charged, by the ctek? I presume this is a mains powered charger?
If it is, then you have three options:
Opportunistic charging whenever being close to a power point.
Wiring it up in parallel to your second Patrol battery by means of heavy duty wires/connection plug.
Supplying the mains powered? ctek with 240VAC from an inverter which gets its power from the starter battery/alternator.

Your single biggest load will be the fridge, with a daily demand of around 40Ah?, plus some other loads drawing a combined 20Ah per day?.
Under this scenario, you'll have to put back at least 70Ah per day.
Some readers here suggest that in average your alternator won't deliver much more than 10A to a partially discharged 220Ah AGM battery (combined) due to the low charging voltage of 13.8V. This means you'd have to run your engine for more than 6 hours every day - not the best option.
Solar is definitely worth a second look (2x120W panels?), plus a gennie for backup.
Another option is to go DC/DC alternator to second/third battery charging.
This way you could increase the charge acceptance somewhat due to the higher charging voltage, but you'd still have to run your engine for a few hours every day.

But I tell you what I'd do:
If it's only for 4 to 5 days if I understand you right, then I'd purchase one more 100Ah AGM deep cycle battery.
With a combined 320Ah you'll be able to run your gear for this shortish period and not worry about recharging for the time being.
When back home, recharge all your batteries as soon as possible with your ctek.

Let's see other readers' hands on experience now...

Best regards, batterymeister
AnswerID: 401838

Reply By: Member - The Bushwhackers -NSW - Sunday, Jan 31, 2010 at 00:08

Sunday, Jan 31, 2010 at 00:08
Hi Jedo, first thing you will be advised here is to use heavy wire, with anderson plug connections to charge your #2 & #3 batteries. I don't believe that the wire gauge on a seven pin plug would be sufficient.

Have a look at John & Val's blog on electricity for camping Here, it may help with your calculations re: charging and useage of the fridge and lights etc.

I am no expert on this subject, but there are plenty here who are, have a search around the site.

Cheers, Dave
AnswerID: 401839

Reply By: Ross H (QLD) - Sunday, Jan 31, 2010 at 00:29

Sunday, Jan 31, 2010 at 00:29
Hi Jedo

I have a Nissan Navara and tow a Jayco Flamingo S/T. I have a duel batt sys in the car 105amp starter 68amp aux under bonnet 2x 105amp built into the rear drawer sys and 2x 120amp agms in the camper. I have a Setec in the van for when hooked up to 240 or genset but mostly use a nice and heavy cable with anderson plugs for charging the van while on the road. I also run a 50lt waeco in the back of the ute but only on fridge. Have stayed for 5 days and batteries have not gone below 12.6 in the van ( I also use led lights aswell ).
I dont usually stay this long in one spot and usually drive between 6 to 7 hours between stops. Have generator and solar but dont bother using them as haven't had the need yet!!!!
As others have said maybe get another agm and give it a good charge before you go and when you get back and in the mean time just charge off the car as you drive or when needed.

Others will have their opinions Im just telling you what works for me everyones needs are different.

There have been a lot of post on this subject so do a search on battery charge and have read there will bound to be an option that will suite your needs and budget.

Regards Rossco
AnswerID: 401841

Reply By: Motherhen - Sunday, Jan 31, 2010 at 00:48

Sunday, Jan 31, 2010 at 00:48
Hi Jedo

With our previous camper, we went solar. One 80 w panel put out to face the sun when we stopped late afternoon, and set to face east for the sunrise was enough to keep one 100 a/h battery on charge to run the caravan upright fridge of around 120 litres plus a couple of lights. There was no other electric stuff in the camper; water pump was manual. There was trickle charge from the Nissan while moving, but this did little as even late in the afternoon, the battery volts rose much quicker when the panel was put out. The one panel was not enough to run an Engel as a freezer as well. Present caravan will do that and lots more. We have 4 x 130 w panels and 4 x 110 a/h batteries, and regardless of the weather, the batteries are on full charge when we stop for lunch.


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AnswerID: 401844

Reply By: Member - John and Val - Sunday, Jan 31, 2010 at 08:33

Sunday, Jan 31, 2010 at 08:33

I think your best option would be a DC-DC charger powered by the alternator. The big issue with charging batteries over a fair length of wire is the voltage loss along that wire. This is compounded by the fact that the alternator output voltage is a bit low for charging deep cycle batteries anyway. These DC-DC chargers take what voltage is available and output it at a higher voltage to provide suitable charging for the remote battery. There are a few listed on ebay, including some from Derek Bester, a valued contributor to this forum. (Have a look here to see what I'm talking about, or contact Derek for good advice. A good DC-DC charger will cost you less than an extra battery, though I think the one I've pointed to may be a bit big for your purposes.

Ideally you'd have two, one at each deep cycle battery, or move one to each battery in turn.

As already said you will need good solid cable from alternator to the batteries and good connectors. As Dave suggested, it's worth checking out our blog here for further ideas.



J and V
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AnswerID: 401862

Reply By: Maîneÿ . . .- Sunday, Jan 31, 2010 at 11:17

Sunday, Jan 31, 2010 at 11:17
Connect the 120ah van battery to the 100ah vehicle battery via a 175 Amp (N0T 50 amp) Anderson plug and use 1/0 AWG cable, keep it easy and cost effective.

That way the Vehicle Aux and also the Van Aux battery (combined 220 ah system) are both *sharing the load* of powering all accessories connected to each battery system.

Maîneÿ . . .
AnswerID: 401886

Follow Up By: Member - Scrubby (VIC) - Sunday, Jan 31, 2010 at 13:15

Sunday, Jan 31, 2010 at 13:15
G`day Mainey,

When you say,
"Connect the 120ah van battery to the 100ah vehicle battery via a 175 Amp (N0T 50 amp) Anderson plug and use 1/0 AWG cable, keep it easy and cost effective.
That way the Vehicle Aux and also the Van Aux battery (combined 220 ah system) are both *sharing the load* of powering all accessories connected to each battery system. "

The combined capacity may be 220 a/h but the charger will read that the 100 a/h battery is full and stop charging thus only getting a combined total charge of 200 a/h.
Is this correct ? as I have a similar set up with two banks in my van.
(1) 2v - 250 a/h x 6 --- in series = 12v - 250 a/h ( 8 yrs old )
(2) 6v - 200 a/h x 2 --- in series = 12v - 200 a/h ( 10 yrs old)

The two banks (1) + (2) in parallel = 12v - 450 a/h but I was told that I would only have 400 a/h for the reason stated above.
Charging is by 2 x 125w solar panels assisted by a xantrex 20 amp charger when required.

Also, at the moment I am in the process of fitting 2 x 6v - 200 a/h gel batteries in series in the rear of the 60 series.
These are charged by a Sterling DC-DC 12v - 50 amp battery to battery charger. ( see RV Powerstream on this site for specs on the charger and Battery for battery specs )
Batteries have 20 year life, guaranteed for 5 years providing I set it up as instructed.

I am expecting some here to question my set-up, but the batteries have been proven in the c/van having done some very offroad travelling.
The DC-DC charger is a much better/easier option than generator or solar.

Just wanting to put it all to some tests soon.



FollowupID: 671325

Follow Up By: Maîneÿ . . .- Sunday, Jan 31, 2010 at 13:34

Sunday, Jan 31, 2010 at 13:34
If 2 x batteries are wired in *parallel* it's only one battery of 12 Volts.

The total Amperage will be the sum of the two batteries, 220ah
(120 + 100 = 220)

With the original post it was about "free camping" where you want to enjoy the surrounding countryside and not have to worry about charging batteries etc.

Does the charge regime you have require the batteries to be monitored ??

Do you have to run engine when they get low for charging to work ??

With Solar there's no need to monitor anything, it's done automatically.

Maîneÿ . . .
FollowupID: 671333

Follow Up By: Member - Scrubby (VIC) - Sunday, Jan 31, 2010 at 23:22

Sunday, Jan 31, 2010 at 23:22
G`day again Mainey,

Yes I have solar, as I said previously the c/van has 2 x 125w panels on the roof and I also have a folding 100w portable panel.
The problem is neither lot of panels were, or would be, suitable for charging the vehicle auxiliary battery while the vehicle was not connected to the c/van.
e.g. when shopping , on a tour out to the Barrier Reef or on the Sky Rail etc.....,climbing Kings Canyon etc. etc. Or even fishing for the day.
Any time the vehicle is not connected to the c/van and is parked for any length of time away from camp, the 80 ltr fridge running as a deep freeze @-12 > -15 oc will not be running when we return due to a flat aux battery. (only 80 a/h)
So the solution is ....... as previous "FollowUp", larger capacity batteries and a quick and efficient method of charging them.

Thanks for the info, that`s what makes this site so good.

Cheers ,


P.S. Hope to meet you at Wiluna all going well.
I want to travel in the wagon only,no c/van, no generator and hopefully no solar panel, but still need the fridge.
FollowupID: 671420

Reply By: Jedo_03 - Sunday, Jan 31, 2010 at 21:03

Sunday, Jan 31, 2010 at 21:03
Thanks for your time Mates...
Informative replies

Am looking at the 12/12 option
Will tell you how I go
AnswerID: 401968

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