Fitting 3rd Battery

Submitted: Tuesday, Apr 19, 2005 at 06:36
ThreadID: 22182 Views:3902 Replies:10 FollowUps:6
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I have a LC100 TD and run a Waeco CF110 fridge on extended trips. Before going to the Kimerleys last year I upgraded the start batteries to two Century severe service N70's which are not isolated. During our trip we avoided flat batteries by starting the vehicle two times a day plus each days drive.

I'm now looking to fit a third N70 and fit a rotronics isolator or similar. One 4WD store advised me to fit a deep cycle battery which is what I had in mind. I then went to Battery World to check prices and they advised that a deep cycle will not cope with the corrigated roads and I should fit a marine battery which can be discharged down to about 50%. I then went to another 4WD store and they say I should convert the exsisting twin start batteries to a proper dual system and change the second battery to a deep cycle. Battery World say this will cause premature failure of the start battery and leave the twin start batteries as is and fit a 3rd.

I'm happy to fit the third battery (Opposite Lock have a N70 tray for this) but don't really know who's right on this. My opinion is that the deep cycle batteries are not designed to handle the vibrations of a corrigated road but they are used successfully anyway.

Can some who knows enlighten me?

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Reply By: Sand Man (SA) - Tuesday, Apr 19, 2005 at 07:01

Tuesday, Apr 19, 2005 at 07:01
I think you are being given a bum steer Topend.

Never heard that Deep Cycle batteries can't handle corrugations. They are made with thicker plates than a standard Starting Battery.

Check the facts here:- Battery FAQ's


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AnswerID: 107330

Reply By: Peter 2 - Tuesday, Apr 19, 2005 at 08:04

Tuesday, Apr 19, 2005 at 08:04
I'd put the 3rd battery in but make it a gel cell, yes you 'may' reduce its life by not charging it fully but as they can last for anything up to ten years I don't consider that a worry.
By making it agel you can fit it inside the vehicle without a worry, Sonneschein are one of the better brands marketed under the Dryfit label.
Peace of mind by having a seperate battery to run the frig is worth heaps.
AnswerID: 107337

Reply By: drivesafe - Tuesday, Apr 19, 2005 at 08:13

Tuesday, Apr 19, 2005 at 08:13
Hi Topend, a deep cycle battery is constructed in the same way and of similar materials to your every day cranking battery. So how many cranking batteries have you heard of that spat the dummy because someone took their vehicle over corrugated roads?

If I were you I would give that particular Battery World a miss.

Now, do you need two starting batteries to get your reg going, if not or if your not sure try disconnecting one and drive around for a week or two and see if every thing works OK.

If it does then just fit a battery charge controller between the two batteries you already have and the jobs done and done for a lot less that most of the suggestions the different shops have been giving you.

AnswerID: 107339

Reply By: JohnN - Tuesday, Apr 19, 2005 at 08:15

Tuesday, Apr 19, 2005 at 08:15
Gday Topend
I have put the 3rd in my TD 100 and am pleased. I used a traxide sc40 (check it on google) isolator and had the stainless steel 3rd tray fiited by ARB as they have to relocate the fuel filter. Other than Tray fitment I did it myself and it is easy.

I went for a deep cycle marine from repco (75ah) for about $140 and it has worked faultlessly. Well worth doing. I dont have to run the car at all for 4 days ( if desired) during summer, and still have super cold beer.
AnswerID: 107340

Reply By: Jason M P - Tuesday, Apr 19, 2005 at 08:19

Tuesday, Apr 19, 2005 at 08:19
hi topend . as i have std.lc100.I have twin battery set up with a SURE POWER battery separator.Main battery is N70 and the other 1 i use is a ODYSSEY sealed lead battery 12v/ 1500amp.Went up to cape york last August for 4 week trip & use waeco cf 110 fridge.Had no problem with the battery and it still in the car now.I also put a thick rubber mat under the battery to protect it from corrigated roads.

cheers.. happy camping.
AnswerID: 107341

Reply By: Errol Flynn - Tuesday, Apr 19, 2005 at 10:59

Tuesday, Apr 19, 2005 at 10:59
SNAP!(-ish) I am running a 24V two battery land cruiser. I installed a third battery (deep cycle - as recommended by Battery World Burleigh Heads ) to charge via a dropdown unit.

When the motor is going, I run the CF110 off 24V and charge the deep cycle at 12V. When the motor is off, the fridge runs off the 12V deep cycle. It all works well. I believe my better option is to set up 2 x Deep cycle and a solenoid, but I got out of it for under $100 and it all works well. Luckily I was able to remember some stuff from my Electronics Engineering days!

Your second battery on the 12V system is the subject of much discussion as to weather deep cycle is better or not. I would certainly go to a deep cycle, as they are more bullet proof. It will also handle a crank if your other battery dies. It should not shorten the life of your other battery.

Your fridge also has an auto cut-off which prevents the battery charge dropping below crank voltage. The only way you will find yourself stuck is if you use the emergency override on the little switch at the bottom. Hope this helps.


AnswerID: 107357

Follow Up By: Jason M P - Tuesday, Apr 19, 2005 at 13:33

Tuesday, Apr 19, 2005 at 13:33
hi scott just wondering how do you run your fridge of 24v system???
Or do you mean 2 x 12v battery then switch it over on the 3rd single 12v battery.

FollowupID: 364300

Follow Up By: Errol Flynn - Tuesday, Apr 19, 2005 at 14:27

Tuesday, Apr 19, 2005 at 14:27
Hi Jason,

The Waeco has autosensing electronics. I run it on 24V while in motion and switch over to 12V when not. I can send you my circuit diagram if you wish.

FollowupID: 364310

Follow Up By: Jason M P - Friday, Apr 22, 2005 at 10:38

Friday, Apr 22, 2005 at 10:38
G'day .. yes. i didn't know that the Waeco can run on 24v thats all.No need for the circuit diagram. thanks anyway...
cheers ..
FollowupID: 364672

Reply By: Mainey (WA) - Tuesday, Apr 19, 2005 at 11:54

Tuesday, Apr 19, 2005 at 11:54
putting it very bluntly; the battery world guy is a seriously demented wanker.....

If you want some facts on what batteries, then ask people who have the system you want, ask what they think about them and also ask people who have the knowledge to be able to give you honest and factual answers....

Note, you can't, (well you can if you are obtuse) mix batteries when wiring them in parallel, even if it is only two batteries, so you can't add a gel battery or Deep Cycle battery to a wet cell battery and expect them to charge/discharge without problems as they will accept and also distribute charge at different rates.

A Rotronics isolator is a good brand, go the heavier model not the base model ($240?)
Use 2B&S wiring and tinned and crimped connections to ends of all leads to avoid power loss.
Use a third battery in the system, _ONLY_ if the existing two batteries are in as new condition internally, not their actual appearance, have them tested by a COMPETANT battery specialist, as by adding a third battery, even the same brand and specs to the existing 'average' batteries, will stuff the system so it is not getting the full benefit of the new battery, wasting your time and money.

Best method; add two ‘quality’ (N70 size) Deep Cycle batteries to your existing starter battery/s, and separated by the Rotronics isolator, giving you 160 (2x80a/h) to 210 (2x105a/h) Amp Hours.
As previously stated, DC batteries are not prone to shaking apart on corrugated roads any more than starter batteries.
AnswerID: 107364

Reply By: Errol Flynn - Tuesday, Apr 19, 2005 at 14:44

Tuesday, Apr 19, 2005 at 14:44
Hi Topend,

All of the posted replies make sense, and we are all operating successfully. I have a degree in this stuff, but you don't need one. Just ditch the bloke from your local Battery World. Also, the deep cycle are better designed for corrigations.

If you are interested I can email you my circuit diagram, although I suspect you are running a 12V system.

For another opinion, talk to Steve at TJM Underwood or
Battery World Burliegh Heads. I have nothing but confidence in these guys.

The people that sell you stuff at TJM are the same people who work under your car and compete in events around the place, unlike another well known over-priced megastore.

Cheers mate!
AnswerID: 107390

Follow Up By: Topend - Wednesday, Apr 20, 2005 at 06:35

Wednesday, Apr 20, 2005 at 06:35
Hi Errol,

My system is all 12 volt, all wired in parallel. Toyota fit the twin batteries for starting only as the glow plugs stay on for some time after starting for the first time of the day which can drain a single battery if you only travel short trips. I used to work at Holden and they upgraded the turbo diesel Jackaroo to twin batteries for the same reason. I can detect when the glow plugs switch off as the lights get brighter and the wipers get faster, so the glow plugs draw quite a bit of power.

Funny you mention TJM. The local store do not fit deep cycle batteries as they only have a 6 month warranty. They fit a battery similar to a marine battery. Can't remember which one. They get less come back apparently.

FollowupID: 364382

Follow Up By: Mainey (WA) - Wednesday, Apr 20, 2005 at 18:05

Wednesday, Apr 20, 2005 at 18:05
(Quote)The local store do not fit deep cycle batteries as they only have a 6 month warranty. They fit a battery similar to a marine battery. Can't remember which one. They get less come back apparently. (end quote)

Generally speeking, Deep Cycle batteries will all have a various length waranty, as do starter batteries, some DC batteries are guaranteed for at least two years.

As stated above, stick to the people who do know their business, and I also concurr, people who work on, race and use 4x4's will always have puperior knowledge than those who read books and have no experience!
FollowupID: 364452

Reply By: snailbate - Tuesday, Apr 19, 2005 at 20:58

Tuesday, Apr 19, 2005 at 20:58
just get a 100 amp triple isolater solanoid
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AnswerID: 107445

Reply By: Topend - Wednesday, Apr 20, 2005 at 06:47

Wednesday, Apr 20, 2005 at 06:47
Thanks for all the replies. I ended up fitting a 3rd severe service battery with a Pirahna isolator. This battery has a 18 month warranty compared to only 6 months for a true deep cycle.

I almost bought an absorbed glass mat deep cycle battery but when reading the instructions in the store it recommends not discharging below 50% to prolong the battery life. Therefore I did not see an advantage over the severe service battery which can be taken down to 50% and cost $100 less.

I will get a 125 watt solar panel before the next big trip.


AnswerID: 107485

Follow Up By: Errol Flynn - Wednesday, Apr 20, 2005 at 09:07

Wednesday, Apr 20, 2005 at 09:07
Well done Topend. Keep cruzin!
FollowupID: 364392

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