Dual Battery set up

Submitted: Saturday, Feb 28, 2004 at 13:50
ThreadID: 10873 Views:3428 Replies:13 FollowUps:21
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Why do we really need all this fancy electronic bells and whistles gizmo's for keeping both batteries charged.
I have had a simple relay which only allows me to draw down from 2nd for the fridge and inverter etc. The main battery is dedicated to the car.
Th alternator charges either or automatically.

Whats wrong with this setup? Wow, am I cute! The extra long legs are built-in prevention against ducks disease. Great looks and a real goer. Doesnt waddle along like some.
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Reply By: Member - Frank - Saturday, Feb 28, 2004 at 14:05

Saturday, Feb 28, 2004 at 14:05
you are right all I did was talk to my auto elec about my needs I have a Heavy Duty one way solinoid ( power in from main) two extra power points fited (at back seat and rear toolbox) all done internaly with 30/50 fusing and heavy cable the only thing showing are the outlets the hole thing cost under 300 dollors cant remember exact amount he has done most of my toys.

we are in the same town I belive call if you want and I will give you his number
it is at work (8 to 4.30) 82668602 if at meeting leave message will call back

frankCBS
Cant Bl**dy Sitstill
AnswerID: 48520

Reply By: Member - Slim - Saturday, Feb 28, 2004 at 14:27

Saturday, Feb 28, 2004 at 14:27
Eskimo and Frank,

I think you are right also. I have always worked on the keep it simple theory and my setup is almost the same as you describe. The only variation I can think of is a push in switch under the steering column which will activate a solenoid which allows the second battery into the cranking circuit should the cranking battery fail.
I think it's fair to say all these systems diverting charge and giving LED readouts are really just toys!

Slim2002 4.2 TD Patrol
AnswerID: 48523

Follow Up By: Member - Bruce and Anne - Saturday, Feb 28, 2004 at 15:00

Saturday, Feb 28, 2004 at 15:00
The dearest part of my set up is the flash battery box, (battery has to go in the back as no room in the engine bay) I have a 30amp fuse at each battery about 5mm wire (going up to about 8mm soon) an isolator switch at the rear battery. At present when the motor is running main bat shows 14.2 volts he other 14.1. Fuses incase it shorts out along the line some where. This set up run my 80 litre Waeco to Darwin and back last year and probably another four weeks running around Qld since. The whole cost without the battery box about $30.
I play around with boats alot and we have a saying (probably a lot of other people have it to) KISS " keep it simple stupid".
All the best. Bruce MU-ving on
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FollowupID: 310354

Reply By: Bilbo - Saturday, Feb 28, 2004 at 15:10

Saturday, Feb 28, 2004 at 15:10
Having existed as a prospector for many years in the WA bush it has been my experience that the "KISS" principle is best. I had a 1898 ford Maverick tray back ute that carried all sorts of electrical goodies. None of which had fancy LEDS, sensory relays and such like. I used two batteries with a simpe relay that charged the cranking battery first and the fridge battery second. These are very common. If they break down they are easy to rig up again or bypass as temporary solution. What's happening with a lot of us is that we are wiring things onto our trucks that are nothing more than an attempt to get an electrical circuit to do the thinking for us. In the bush that's dangerous. Keep the wiring simple, ditch the fancy stuff that's liable to break and let you down and think about how much current you can generate and how much power you use. There are simple calcs. The cranking battery must be protected before anything else. In the bush you can live without a fridge and lights, CD player ec, but without a engine that will start you could be in serious manure. Let yer head do the thinking, not an "easy fix" bit of electrical gear that, when it lets you down, you wil be unbale to figure out how to get around it.
Bilbo
AnswerID: 48526

Follow Up By: Member - Eskimo - Saturday, Feb 28, 2004 at 15:51

Saturday, Feb 28, 2004 at 15:51
Of course you right with those words Bilbo "that are nothing more than an attempt to get an electrical circuit to do the thinking for us"
Bit like having a a thesaurus and dictionary in Word

Wish I could get my staff to just think!....just once would be lovely hahahaWow, am I cute! The extra long legs are built-in prevention against ducks disease. Great looks and a real goer. Doesnt waddle along like some.
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FollowupID: 310356

Follow Up By: Moneypit - Monday, Mar 01, 2004 at 02:28

Monday, Mar 01, 2004 at 02:28
Billbo,

You have solved the eternal question. Which came first, the Maverick or the Patrol. Given that you have an 1898 Maverick you win, game over!! Must have ticked over some bloody miles by now but!!

Dave
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FollowupID: 310511

Reply By: ianmc - Saturday, Feb 28, 2004 at 15:41

Saturday, Feb 28, 2004 at 15:41
I have read with interest all the different twin battery set ups & electronic gadgetry
controlling the vitals worries me.
4X4 Aust a while back mentioned that 7 out of 9 4wd's towed out of the Simpson at great expense were due to computer/electronic failures. The tow costs & replacement parts if out of warranty would amout to the price of a rw secondhand 4wd or close.
I used to have an International AA120 4wd van with high speed diffs & 283 cu.i six.
Heaps of torque & low first was about 60 to 1. It would idle along in low first at 500 rpm or less & you could walk along beside it.
Sorry I digress! The AA120 had twin batteries & a simple heavy duty switch whereby I could switch from one battery to the other for starting or charging & it depended only on the nut behind the wheel to work OK.

Wish I could post a pic for Willem as he likes old tech!
AnswerID: 48530

Follow Up By: Member - Eskimo - Saturday, Feb 28, 2004 at 15:57

Saturday, Feb 28, 2004 at 15:57
Infering Willem is old eh?
he'll have your guts for garters lol lolWow, am I cute! The extra long legs are built-in prevention against ducks disease. Great looks and a real goer. Doesnt waddle along like some.
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FollowupID: 310357

Follow Up By: Willem - Saturday, Feb 28, 2004 at 21:07

Saturday, Feb 28, 2004 at 21:07
Well, my brain still thinks like a 20yo but the body says otherwise.

The one thing I have over most of you fellas with the electronic stuff is a crank handle. If all else fails I can still crank the old truck to start !!!Willem
Little Dip Cons Park S.A.
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FollowupID: 310387

Follow Up By: Member - Eskimo - Saturday, Feb 28, 2004 at 21:18

Saturday, Feb 28, 2004 at 21:18
But what ya gunna do when ya get a newie
How ya gunna make it fa err start then Wow, am I cute! The extra long legs are built-in prevention against ducks disease. Great looks and a real goer. Doesnt waddle along like some.
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FollowupID: 310388

Follow Up By: Willem - Saturday, Feb 28, 2004 at 22:00

Saturday, Feb 28, 2004 at 22:00
I am looking for a newbie without a computer...fat chance!! Maybe I'll just stick an airconditoner and power steering in the old truck. Had a Suzuki once with a stuffed starter motor. Just jacked it up and started it with as piece of rope 'round the rear wheel. Ignition on, third gear and pull start like a Victa. No worries.Willem
Little Dip Cons Park S.A.
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FollowupID: 310394

Follow Up By: Perry - Sunday, Feb 29, 2004 at 16:41

Sunday, Feb 29, 2004 at 16:41
Same set up in my old Landie. Big marine switch and you decide which battery to use when stopped or charge when mobile. Something to be said about the old trucks, mine even with v8 can be crank started too.
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FollowupID: 310464

Reply By: Dave from Fraser Coast 4WD Club - Saturday, Feb 28, 2004 at 15:55

Saturday, Feb 28, 2004 at 15:55
Keeping it simple is all well and good, but if you do not at least use a diode setup, then when you start the car and close the solenoid, the charged (starting) battery will dump half its charge to the flat (aux) battery.

Should you stall at this time , you will have two half flat (or half charged depending on your outlook on life) batteries. That might still be enough to start the car, it might not.

When two batteries are joined, they will try to equalise, the internal construction of each battery and the cabling joining them will determine how quickly they will achieve this.

The advantage of the gizmos is that they can 'keep an eye' on you starter battery, and open the solenoid (isolate the aux) if (when ) the charge starts to drop, then reopen it again when the starter reaches a fully charged state.
AnswerID: 48534

Follow Up By: Mad Dog Morgan (Geelong) - Saturday, Feb 28, 2004 at 20:00

Saturday, Feb 28, 2004 at 20:00
Every time a relay collapses or a contact is broken damaging transients and high voltage spikes can result so it's not only the dual battery system we need to be concerned about. Ideally we should all have an antizap device installed at the battery to protect the vehicle and our expensive toys...cheap insurance

BEAM ME UP SCOTTY


Hooroo
Ray
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FollowupID: 310379

Follow Up By: Mad Dog Morgan (Geelong) - Saturday, Feb 28, 2004 at 20:02

Saturday, Feb 28, 2004 at 20:02
Sorry dave, I put that in the wrong thread. BEAM ME UP SCOTTY


Hooroo
Ray
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FollowupID: 310380

Reply By: Wayne (NSW) - Saturday, Feb 28, 2004 at 17:25

Saturday, Feb 28, 2004 at 17:25
In the 11 years I was fitting 4wd accessories that would have been one of the most asked question.

Just looking at the replies so far and the photos of the vehicles, most are late model and could have some form of electronic engine management system. Fuel injection is one example (petrol). Electrical plugs that are pluged in the air cleaner chamber or in the air pipes from the air cleaner to the manifold are another give away that you have some thing thinking for you.

With a simple methiod, when the motor starts the alternator will try and charge both batteries at the same time. If one battery is low, below 10.5 volts it will try and charge it up quick. This is were a power spike could come from.

A alternator will stop charging a battery when it sences it is fully charged and will then free wheel until required, just like the air con compressor, with a good isolating system instead of the alternator free wheeling it will charge the second battery and when that is fully chareged it will then free wheel.

Once a spike goes through the system, that is when on board computer system goes down.

If one of the batteries drops a cell the alternator keeps on charging and will over charge the good battery.

You are also asking a alternator to charge two batteries at one time when it is only made to charge one at a time.

If a deep cycle battery is fitted the alternator can not sence this and tries to charge it at a cranking battery rate. The deep cycle battery will soon die.

You are going to have to put some form of isolating system in the set up or both batteries could go flat if running acessories when the motor is stopped.

I have always fitted the Piranha dual battery isolator for the following reasons

1 Spike protection built in
2 Charges the second battery (deep cycle) at a slower rate
3 Printed circuit, no moving parts or diodes to build up heat or create voltage drop
4 Simple to install, one x150amp cable to the main battery, one x150 amp cable to the second battery, one 2mm wire to earth and one 2mm wire to turn the system on.
5 The system once installed is maintiance free and there are no switches for the driver to forget to flick.

One of the replies to this thread mention the cost of recovery from the desert because of battery failure add to that the cost of blown engine management system which would not be covered by warrenty and the amount of down time and I for one can not see the value in a simple setup.

Piranha also do a system if you are running two cranking batteries, works the same but has the option of joining both batteries to gether, via a button on the in cabin controll box. The controll box also has led lights to show volts in each battery and the amount of charge is put out by the alternator.

I hope this will explain why on a average I would fit 2 of these units a week.

WayneAlways Out'N About
AnswerID: 48540

Follow Up By: Rosco - Bris. - Saturday, Feb 28, 2004 at 19:20

Saturday, Feb 28, 2004 at 19:20
Well said Wayne

I also preferred the KISS principle ..... until the issue of spikes etc was explained to me.Fidei defensor

Rosco
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FollowupID: 310374

Follow Up By: Mad Dog Morgan (Geelong) - Saturday, Feb 28, 2004 at 20:03

Saturday, Feb 28, 2004 at 20:03
Every time a relay collapses or a contact is broken damaging transients and high voltage spikes can result so it's not only the dual battery system we need to be concerned about. Ideally we should all have an antizap device installed at the battery to protect the vehicle and our expensive toys...cheap insurance

BEAM ME UP SCOTTY


Hooroo
Ray
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FollowupID: 310381

Follow Up By: Wayne (NSW) - Saturday, Feb 28, 2004 at 20:46

Saturday, Feb 28, 2004 at 20:46
Ray,

The Piranha has that spike protection built in. Spikes could harm any device connected to the batteries,GPS, Mobile Phones,Fridges,UHF and HF radioes

WayneAlways Out'N About
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FollowupID: 310385

Reply By: Phil G - Saturday, Feb 28, 2004 at 22:07

Saturday, Feb 28, 2004 at 22:07
This spike protection thing interests me. I think its a bit of a myth. You can't tell me that the manufacturer doesn't build spike protection in already. Lets face it, most of the computer glitches in the Simpson were from European 4wds - many of them were Mercedes. Japanese have got all this figured out. Spike protection is simply a $10 component added.

If you want a KISS system , then simply wire the 2 batteries together, like the Jackaroo TD or 100 series TD.

I have no problems with the electric isolators. Problems usually come from poor installation and not problems of manufacture. I've see some rediculously poor workmanship from both workshops and DIY - some people have never tought to use a solder iron - they just quick crimp everything.
AnswerID: 48580

Follow Up By: Wayne (NSW) - Sunday, Feb 29, 2004 at 17:37

Sunday, Feb 29, 2004 at 17:37
Phil,

Just read a reply to the thread about maintiance of deep cycle batteries. Pretty heavy stuff. Went into the surepower site . It is worth a read.

WayneAlways Out'N About
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FollowupID: 310468

Reply By: Eric Experience. - Saturday, Feb 28, 2004 at 22:50

Saturday, Feb 28, 2004 at 22:50
Eskimo.
There is a lot of missinformation about spikes, if what the spike merchants say is true then you could not switch on your lights wihout spiking your computor. the battery is like a large spike supressor it would take a huge spike to do any damage, there is no mechanism in the relay connecting the second battery that could generate such a spike. A battery looks like a resistive load, to get a spike you have to have a large inductor and there is not one there. Also this rubish about alternators sensing battery voltage, it does not happen, the output of the alternator is controlled by the regulator, the regulator sets the voltage at the main supply piont which is where the fusable links are commoned. the voltage regulator does not know what the battery voltage is. THe voltage is the same on a modern vehicle with a high current alternator regardles of wether the battery is flat ore fully charged. Eric.
AnswerID: 48590

Follow Up By: Phil G - Monday, Mar 01, 2004 at 08:51

Monday, Mar 01, 2004 at 08:51
Eric,

No argument about the spike stuff, but the regulators on many of the newer Toyotas work a little different. All regulators sense voltage and attempt to keep it about 14-14.2 volts. But the newer alternators also have "current sensing". They monitor how much current is coming out of the alternator. They measure current by detecting the millivolt different at two points between the alternator and battery.

Typically what happens is that the current output is high immediately after starting the vehicle - mine shoots up to 14.3 volts. When the alternator's current output drops off to a lowish level (my guess is about 3-4 amps), the regulator drops the voltage. It does this to protect the battery from overcharging and prolong its life. My voltage will drop below 13.8 volts when on the highway on a long trip, and has been down to 13.5v. This is at a time when you expect the battery to be 100% charged.

I think this system works - a friend's Prado is still on its original battery after 6 years. Main problem with this system is I don't believe it will properly charge wet cell Deep Cycle batteries. I suggest to people to either use a starting battery or gel cell for auxillary batteries.
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FollowupID: 310516

Reply By: Member Eric - Saturday, Feb 28, 2004 at 23:10

Saturday, Feb 28, 2004 at 23:10
i have both batteries connected in the one circit , no gismos switches , If I am out bush and am worried enough about draining both batteries over night, I disconect one of them . Works a treat , no electronics to fail or relays to stick , i now have also a cheep battery pack in the back , witch I use to run fluro lights in the tent and works as a back up if both batteries fail . Venus Bay
AnswerID: 48595

Reply By: Crackles - Saturday, Feb 28, 2004 at 23:23

Saturday, Feb 28, 2004 at 23:23
Another fault of the KISS relay system is when you fit an electric winch. At maximun load it may pull up to 400 Amps and seeing you usually have the motor running joining both batteries together, 1/2 the load (200 Amps) will be pulled through the 100 amp solinoid. 'BOOF'. It may burn it out or weld the contacts together either way it's cactus.
Keep it simple by having the two batteries joined together all the time then fitting a simple low voltage disconnect switch for the fridge set around 11.8 volts. You will always have enough power to start the car and avoid battery damage by never letting either drop below 25 %. Craig.........................
AnswerID: 48600

Follow Up By: Wayne (NSW) - Sunday, Feb 29, 2004 at 08:18

Sunday, Feb 29, 2004 at 08:18
Crackles,

Having a low voltage disconnect switch set at 11.8 volts, how long will the fridge run before it uses .2 volts?

Wayne

Always Out'N About
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FollowupID: 310424

Follow Up By: Crackles - Sunday, Feb 29, 2004 at 13:02

Sunday, Feb 29, 2004 at 13:02
Wayne, the battery voltage with the motor off is around 12.5 so you have a 7 volt drop before it disconnects. How long it will run depends on the size of the 2 batteries. I'm trialing 2, 115 amp hour Trojan deep cyce batteries in parallel.(no starting battery) In theory that gives me 170 amp hour to run the fridge & lights and a reserve of 60 amp hour to start the car. (25 %)
In reality up on the Cape in 32 degree heat I've run the 73 litre Autofridge & fluro lights for 4 days and it still started.
Most dual battery systems run an 80 amp deep cycle for the fridge so when it's isolated the best it can achieve in the heat is half of my system, around 2 days & nights . The other problem to be concidered is the majority of battery damage occurs when you discharge them below 25 % so it pays to keep some charge in reserve.
As a general rule batteries used in the one charging system should ideally be of the same size, age and constuction. ie: not mix starting and deep cycle. This is because they accept charge at a different rate.
As I said earlier this is a trial system which has been running perfecly for just over a year. Whether it works long term I hope to find out in another 4 years. Craig..............................
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FollowupID: 310454

Follow Up By: Crackles - Sunday, Feb 29, 2004 at 13:06

Sunday, Feb 29, 2004 at 13:06
Sorry you have a .7 volt drop. (missed the dot) Craig............
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FollowupID: 310455

Reply By: Big Trev - Sunday, Feb 29, 2004 at 08:02

Sunday, Feb 29, 2004 at 08:02
Form Maverick Diesel, 2 batteries in parallel, 1 hella isolator switch.

Stop to camp, open bonnet, turn red handle, batteries isolated.

When ready to leave, start car on main cranking battery, open bonnet, turn red handle back - both batteries being charged.

Simple really, never let me down, and this sytem was recomended by our towns leading auto elec. Only thing it relies on is your memory, but if you leave your bonnet open to the first click when camping, it is easy to remember.
AnswerID: 48612

Follow Up By: Wayne (NSW) - Sunday, Feb 29, 2004 at 08:48

Sunday, Feb 29, 2004 at 08:48
Big Trev,

That would be a part of the under bonnet check you would do, turn the red handle. Still relying on the human factor. I think trying to remember to isolate the system when you get into camp or when you arrive home could be a problem.

With your Maverick, like my 80, engine management is kept to a minimum. that is the KISS principle I like.

Wayne
Always Out'N About
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FollowupID: 310427

Follow Up By: Member - Mike (SA) - Sunday, Feb 29, 2004 at 14:24

Sunday, Feb 29, 2004 at 14:24
I have identical system in my GQ RB30 - only I place red handle inside vehicle to remind me to put it back! Batteries now in their 4th year (Deep Cycle for fridge) and no problems with approx 2 months in bush each year.Too little time in the bush!
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FollowupID: 310457

Follow Up By: Big Trev - Sunday, Feb 29, 2004 at 20:06

Sunday, Feb 29, 2004 at 20:06
Wayne, haven't forgotten in 11 years. I really, really like the KISS principle.
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FollowupID: 310478

Reply By: ianmc - Sunday, Feb 29, 2004 at 18:48

Sunday, Feb 29, 2004 at 18:48
Wayne, your reply makes sense for those with high tech electronically controlled trucks.
I personally am glad that my Triton is old mech. injection despite the greater power of newbies.
I think I can speak for Willem 2 (pun) as well & say we shal stick to what is simple & works.
I do have a 60w solar panel which I intend to add as back up this year.
Free, reliable but possibly slow back up charging.
AnswerID: 48668

Reply By: -OzyGuy- - Thursday, Mar 04, 2004 at 14:57

Thursday, Mar 04, 2004 at 14:57
yes,
the Piranha system is a fit and then FORGET system

.....totally K I S S .....

So Simple that you never have to think about it again, would be nothing worse than getting to a camp site in the wet and having to open the bonnet to change the 'red' handle, or forgetting to change the 'red handle' and waking up to flat batteries!

I have used the Piranha system for 6 or 7 years without any problems, that is what I call keeping it Simple, when you NEVER have to think about your battery system, you know that it is there and it will work for you.
AnswerID: 49132

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