Submitted: Tuesday, Apr 27, 2004 at 20:08
ThreadID: 12429 Views:2122 Replies:9 FollowUps:8
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Had an interesting discussion with a bloke who sells batteries and also specialises in deep cycles for fork lifts. He told me that deep cycles need to be charged at 2.7 volts per cell whereas start batteries need 2.3. Hence a deep cycle will not perform properly without a charger designed specifically for deep cycle batteries (cost around $700). He said charging deep cycles from your car alternator will never properly charge them, probably only to about 60%, and then lead to premature failure. His opinion of 4wd drive stores is that they are happy to install a dual battery system and sell you a new battery every couple of years.

His suggestion is to fit a truck size start battery (or two in parallel) and dont flatten them. Top them up daily with a generator if in the one spot for long stays. Given that a decent 700 cca battery can be had for $115 and a genny can be bought for $200 (Kmart or Bunnings) I am wondering about the value of a dual battery system.


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Reply By: Mad Dog (Victoria) - Tuesday, Apr 27, 2004 at 20:16

Tuesday, Apr 27, 2004 at 20:16
True Jimbo but how many 4bs have true deep cycle batteries installed. All of the cheap batteries labelled deep cycle just have slightly thicker plates and will still give enough cranking amps to start a vehicle which is something a true deep cycle battery will not do.
AnswerID: 56265

Reply By: Member - Roachie (SA) - Tuesday, Apr 27, 2004 at 20:23

Tuesday, Apr 27, 2004 at 20:23
This is the train of thought I've had for quite a while now, although I wasn't aware of the bit about a special charger being needed. I've used a Deep Cycle battery as an aux and I couldn't keep it "full" even when driving long distances through the NT & Qld day after day. They are really designed for wheelchairs etc as far as I'm concerned.
I now use an Exide Extreme as my 2nd batt and a Exide Orbital in the Camper Trailer. (Nissan's original start batt is still going okay after 42 months).
AnswerID: 56266

Follow Up By: CHRIS - Wednesday, Apr 28, 2004 at 15:17

Wednesday, Apr 28, 2004 at 15:17
Couldn't help but notice your SL 240's on your vehicle.They are a terrific light; but the one I use is for spotlighting and is hand held. The point of my question is, how do you manage with the law with your lights protruding past the height of your bonnet. Wouldn't the lights also be a pain in the a-se with your forward vision. No offence, but was just wondering.
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Follow Up By: Member - Roachie (SA) - Wednesday, Apr 28, 2004 at 15:45

Wednesday, Apr 28, 2004 at 15:45
G'day Chris,
I know what you mean about the lights being a bit of a pain, but only because of the small amount of glare I get from the lense covers. I have previously put black tape around the edge and this worked real well, but looked real cheap and nasty. I'm now thinking I'll get hold of an old inner tube (say 31/10R 15) and cut 2 "donuts" about 40mm wide and see if they'll fit neatly and do the same job.
They are not a pain as far as restricting vision on open roads or in town, but occasionally get in the way when I'm trying to pick my best line through a rocky area etc.
As for the law enforcers.....touch wood, nobody has said anything to me yet. I live in country SA & I think we can get away with a few things that city-based drivers tend not to be able to.
I used to have the 240s in the "right spot" on the bullbar and only moved them when i was experiencing "over-warming issues". These have since been cured by the replacement of the fan clutch, so I guess I should move the lights back down and see if the old girl stays cool.
No offence taken mate.
FollowupID: 318140

Reply By: rooooboy - Tuesday, Apr 27, 2004 at 20:50

Tuesday, Apr 27, 2004 at 20:50
I have never believed in Deep cycle battery's, since i was a kid and went away with the folk's, my dads 60series was for ever needing a jump start!
I run two standard Powercrank Batterys, about 650cc amps, All my acessories run off the main battery (fridge, cb's, lights, amps etc), When the engine is running both batterys are charging, when the key is off They are separated!
If the vehicle wont start the morning after, I have a push button Switch (which i havent used yet!) which operates a solenoid that allows me to usee full power from the spare battery to start the vehicle!
All I needed was two batterys about $80 each and a solenoid and switch
the whole thing costg me under $200 to fit been, that was 3 years ago!

AnswerID: 56272

Follow Up By: Member - Jeff M (WA) - Wednesday, Apr 28, 2004 at 13:32

Wednesday, Apr 28, 2004 at 13:32
I gotta say that those powercrank bat's are great, I have a 750cca starter (I bought for $79) and it's just brilliant.
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Reply By: Topcat (WA) - Tuesday, Apr 27, 2004 at 21:01

Tuesday, Apr 27, 2004 at 21:01
Hi Jimbo, I've been using 'genuine' deep cycle batteries for over 15 years as I have mentioned on previous posts on this forum & I've never had a premature failure yet "touch wood"!!!!. with a dual battery setup in a 4WD. So what ever this person was telling you may occur in some circumstances but my charging setup certainly didn't cost me $700!!. All I do is trickle charge over a long period with solar power when the vehicle is stationary & charge by the vehicle alternator when travelling. I never let the battery get below 50% discharge, (I try to maintain 75%) & the last battery lasted me for nearly 8 years. I use Magnum deep cycle batteries which are American made & cost me around $400 for a 190 amp setup which gives me power to run my fridge & lighting for long periods, so I reckon I'm getting my moneys worth. Cheers
AnswerID: 56274

Reply By: Jimbo - Tuesday, Apr 27, 2004 at 23:39

Tuesday, Apr 27, 2004 at 23:39
Thankyou to you all, great feedback.

AnswerID: 56319

Follow Up By: -OzyGuy- - Wednesday, Apr 28, 2004 at 00:04

Wednesday, Apr 28, 2004 at 00:04
Hope the word ... rubbish.. does not offend you

I drive a forklift and have a decent Deep Cycle battery system, comparing the two is rediculous as a small forklift battery system is about 600 A/H and has to be lifted by a small crane :)
I think the guy was trying to sell you what he had in stock, did he use the system he was sugesting you buy?????

As to the cheap genny idea you are not permitted to use them in any National Park in Australia and neighbouring campers will also be a bit miffed if you run them at nite, killing the tranquility and the ambiance of the bush.

Read any battery manufacturers specifications sheet that makes BOTH Deep Cycle and also Cranking batteries and you will see that the Deep Cycle is heaps heavier than the equivelently sized Cranking battery, solely due to the extra size (not numbers) of the lead plates used in the DC batteries.
Cranking batteries are not suitable to be constantly cycled, they are only made for starting the 4x4 not running the fridge.

When did you last read a post here from someone stating how good their battery system is, they don't, the reason is simple, they don't have the hassle of turning their fridge off each nite to save battery power, they think it is normal to have a battery system that works.

FollowupID: 318066

Follow Up By: Member -Bob & Lex (Sydney) - Wednesday, Apr 28, 2004 at 18:34

Wednesday, Apr 28, 2004 at 18:34
Ive never heard you can't use a genny in a national park , cheap or not.
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Reply By: Mad Dog (Victoria) - Wednesday, Apr 28, 2004 at 13:53

Wednesday, Apr 28, 2004 at 13:53
some good info here on deep cycle batteries.

AnswerID: 56392

Follow Up By: Crackles - Wednesday, Apr 28, 2004 at 21:55

Wednesday, Apr 28, 2004 at 21:55
Very interesting reading Mr Dog. I particulary liked their views on using deep cycles as a starting Battery.
"There is generally no problem with this, providing that allowance is made for the lower cranking amps compared to a similar size starting battery. As a general rule, if you are going to use a true deep cycle battery also as a starting battery, it should be oversized about 20% compared to the existing or recommended starting battery group size to get the same cranking amps." Also their comments on expected life span of starting batteries if regulary deep discharged. (12 months!)
A great site that squashes many battery myths. Craig................

FollowupID: 318197

Follow Up By: -OzyGuy- - Thursday, Apr 29, 2004 at 12:58

Thursday, Apr 29, 2004 at 12:58
Further information re Rubish...

I checked some of our forklift batteries at work last nite and here are some interesting FACTS...

Weight: eight hundred and sixty kilo's (860 Kg) each
They are 48 Volts
Recharged by a 50 Amp battery charger
Rated as 640 Amp Hour

They are referred to as a Traction battery, not Deep Cycle battery,
I was advised by my forman that all forklifts are powered by Traction batteries.

FollowupID: 318297

Reply By: TheUndertaker - Wednesday, Apr 28, 2004 at 17:14

Wednesday, Apr 28, 2004 at 17:14
Go to
AnswerID: 56422

Reply By: mungunya - Wednesday, Apr 28, 2004 at 17:17

Wednesday, Apr 28, 2004 at 17:17
Mate, give Mick Christie (outback battery charger mob) @ christie engineering Horsely Park in Sydney a call, he is atop fulla , @ knows batteries. For my 2 bobs worth deep cycles are good for mother in laws wheelchairs when you dont want them to get home.
AnswerID: 56424

Reply By: Jimbo - Thursday, Apr 29, 2004 at 18:57

Thursday, Apr 29, 2004 at 18:57
Spoke to another bloke who sells Trojan Deep Cycles and he used to supply the police force who replace their start batteries with deep cycles to run lights while stopped. The deep cycle works fine as a start battery.

AnswerID: 56603

Follow Up By: Steve - Sunday, May 02, 2004 at 14:12

Sunday, May 02, 2004 at 14:12
mungunya: noticed the petrol battery charger he recommends...but isn't this getting back to the noise problem with gennies? What's the db count on the charger running off fuel? Surely the NP Ranger'd be just as tough on these as gennies?I'm trying out my Waeco FF70, which they claim draws 3.5 amps on a 25 degree day.That's running on the minimum setting which doesn't quite keep the beer at an optimum drinking temperature. They also claim that it only runs @ 33% of the time due to the compressor. I'm trying mine out now as I type and keep sticking my head into the car and the bloody things humming away every time, so I don't know about 30%. Whether that's just the fan I dunno
FollowupID: 318702

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