Deep Cycle Battery Advice

Submitted: Tuesday, May 28, 2013 at 11:53
ThreadID: 102458 Views:2143 Replies:5 FollowUps:2
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I have searched for this topic but none of the replies match my particular requirements - not quite.
I am seeking advice regarding purchasing an AGM battery - probably a FullRiver. I realise they are expensive but l have read from most people that a higher quality battery will save me money in the long term.

I am unsure if a 105AH AGM will be more than sufficient for my needs - or whether a 120 or 150AH would be wiser at the outset.

I am not a 'huge' free-camper but now that our children are off our hands it is something we intend to pursue more of. I would basically only be running LED lights at night and possibly a small inverter for camera or iPad charging at a later stage. I would usually be away from 240V for only a day or two - plus charging from the car while in transit.

My only reason for considering a 120 or 150AH is that if L decide to do a lot more free-camping - I would already have the capacity although it may be just overkill in my circumstances.
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Reply By: olcoolone - Tuesday, May 28, 2013 at 12:08

Tuesday, May 28, 2013 at 12:08
QUOTE"My only reason for considering a 120 or 150AH is that if decide to do a lot more free-camping - I would already have the capacity although it may be just overkill in my circumstances."

You have answered your own question, if you think you have a need for the bigger battery then choose that one.

There is no substitute for aux battery capacity, in most applications I would recommend 200 amps of capacity as a good size.

The other thing to remember is the more you discharge a battery and the more often it is done (cycled) you are decreasing it's life.

So in theory the bigger the better, if you had a 100 amp battery you may discharge it to 30% SOC (capacity) where by if you had a 200 amp battery and used it for the same application you would only discharge it to 60% making the battery last longer in terms of service life.

A battery in ideal conditions on float charge most of it's life will last easily over 10 years and up to 30 years.

Doing something right the first time is the best way to save money, too many cut corners and then wonder why it has failed or doesn't work correctly.

AnswerID: 512000

Reply By: Member - Phil G (SA) - Tuesday, May 28, 2013 at 12:52

Tuesday, May 28, 2013 at 12:52
"I would basically only be running LED lights at night and possibly a small inverter for camera or iPad charging at a later stage."

Hi Gary,
You are currently using very little power from that battery. A secondhand Barina battery would do the job. Sio I guess an AGM is overkill unless your plan is to mount the battery in the cabin of the vehicle. And capacity will not be an issue in the future unless you plan on running a fridge from it.
AnswerID: 512008

Reply By: Member - Gerald V - Tuesday, May 28, 2013 at 13:01

Tuesday, May 28, 2013 at 13:01
hi garytee,

I have a 40Ah Lithium battery with a small 20w solar panel for our camper. I find that with this configuration I can maintain a large laptop, android tablets, 2 mobile phones and Kindles while operating led lights comfortably for a week or more without charging from the vehicle provided we have a few sunny days. We are a family of 6. The lithium does have the advantage of being able to discharge down to 10% without affecting the life of the battery significantly. We also run a small fridge on an independent 60Ah lithium battery that runs for 3-5 days depending on the weather.

Wherever you can get chargers that operate directly from 12v (eg car style charger for your iPad) so that you increase efficiency (if you use an inverter you convert 12vDC up 240vAC, then 240vAC back down to 5vDC and there are always power losses with these conversions).

I think that many of the configurations that people advise are overkill. It's a simple matter of adding up the power requirements of the equipment that you use, decide on a length of time that you need to use them for and calculating the battery size required. Our 40Ah battery with 20w panel was chosen based on a careful consideration of our power requirements and needs. For example, my smartphone battery has 5.11Wh stamped on it (Watt hour). So, at 13v (normal voltage for our Lithium) this equates to 0.79Ah of battery capacity (assuming 50% efficiency in conversion down from 12v + losses in the phone's internal charger circuit) to completely charge a dead flat smartphone battery with a car style charger. If all I was doing was charging my phone I could do it 40 times from completely flat and still have spare capacity! A small solar panel can also increase this time greatly - our 20w panel is just bolted to the toolbox on the front of our camper.

It's worth doing the maths, even if you have to borrow an ammeter to measure your equipment so that you get exactly what you need rather than what others assume that you need!

Good luck.

gerald v
AnswerID: 512009

Reply By: Member - John and Val - Tuesday, May 28, 2013 at 13:16

Tuesday, May 28, 2013 at 13:16
Hi Gary,

Your present requirements can probably be met without any auxilliary battery. Your cranking battery will handle a few led lights plus camera and ipad charging for a few days.

Suggest look for 12V chargers for the camera, ipad, phone etc rather than use an inverter - more efficient and cheaper than a decent little inverter.

For the longer term you really need to define your requirements before buying an auxilliary battery. The critical point is whether you will need to power a fridge. A fridge will take 2 or 3 times as much power as all your other low power camping gear. Suggest you may find Electricity for Camping a worthwhile read. It discusses system sizing and charging options and lots of other stuff.

To directly answer your questions - To meet your present requirements, you probably don't need an auxilliary battery, but a small one would be ample. In the longer term the size you'll need depends very much on just how you set up for camping, your travel habits, and personal preferences. I would avoid at the outset spending money on a bigger battery than you need at the outset - the cheapest little cranking battery, rather than an AGM type, could do the job for now (assuming you don't have to carry it inside the vehicle), and when the fridge comes along it will be time to get serious with battery/s.



J and V
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AnswerID: 512010

Follow Up By: Sand Man (SA) - Tuesday, May 28, 2013 at 19:05

Tuesday, May 28, 2013 at 19:05
Very sound advice John.
Agree wholeheartedly!


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FollowupID: 790319

Follow Up By: Member - Paul B (WA) - Sunday, Jun 02, 2013 at 12:43

Sunday, Jun 02, 2013 at 12:43
Absolutely. Well done John. The critical thing is fridge use, especially in hot weather being used to cool drinks. If you don't have heavy fridge use your power demands are quite low these days with LED lights.

I've spent thousands over the years on dual battery systems on various vehicles but now that I've seen Thumpers and battery starter kits, I don't think I'd do it again. For overnight camping a cheap 100A starter kit ($120-$150 from Repco) does us fine, and for extended camping, for us a 75A or 105A Thumper looks a far more viable option, especially with a DC-DC charger.

Interestingly, the thing that's caused us the most grief and people we've camped with in modern vehicles, is door lights flattening batteries. Not the interior dome lights that you can turn off, but the lights that come on to shine on the ground from the bottom of the door even when it's only slightly ajar, especially on the other side of the car where it isn't as obvious. Or if you've got kids with you, who have no concept in this world of plenty, about husbanding scarce resources like battery power by closing doors!
FollowupID: 790708

Reply By: MEMBER - Darian, SA - Tuesday, May 28, 2013 at 14:02

Tuesday, May 28, 2013 at 14:02
Agree with above comments - your needs are low end so a modest battery size will be plenty - keep weight in mind too - a Century 100Ah AGM DC for example is 29kg - a 165Ah is 53kg ! Because expensive batteries have to be charged and monitored quite regularly to maximise lifespan and preserve your $ outlay, its probably best not to buy a big one until you actually need it.
AnswerID: 512013

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