More dual battery questions...

[Coupland]

After some reading and researching I think that I have finally sorted out what I want to do for my dual battery setup. I am putting fingers to the keys so that someone out there might answer some of my dumb questions or point out something I have missed before I start destroying the Lux.
My main aim for the dual battery setup is to run only my fridge (possibly two) while camping. I would not be in the one spot for more than two days and if I was, there would be 3-4 hours exploring in the vehicle during that time.


I am looking at getting a Redarc battery isolator, two AGM batteries (only crank, one auxiliary) and 6 gauge B&S cable to fit out the system. I am planning on sitting the auxiliary battery in the tray of the Lux next to my drawers that will be built. The auxiliary battery will be covered. Does it need to be vented to the outside world? Eg Is it safe for the dog to be snoozing in the back while it is charging?


Will this meet my needs or have I missed something?

Will an AGM battery give me the best possible amp hours for the above camping scenarios?

I take it is better to have the crank battery and auxiliary battery of the same type?

Cheers

Tim

[Phils Lux]

Tim,
i have a dual cab hi lux V6 with tjm canopy flip up vent plus slding window to help with ventilation i have my battery(n70zz) installed in the tray between the wheel arches, battery box then metal tray(bolted through battery box)to the tray, tjm battery system manages the chargeing.
Run an engel 40 lt only from the battery i tend to drive every few days so it charges ok, i went with wet cell battery for fast chargeing for my touring needs, also similer battery on drwa bar of my camper trailer to run the 12 volt lights, have a battery charger plus honda generator if i can't use power in caravan at least once per week, this setup suits my needs ok.

[100cruiser]

I use the Redarc system and have no problems with it. Most of the time all that runs of the aux is the fridge (50l waeco). To your question about having the same batteries. I have a Century Marine Pro as my aux battery and had a Century Severe Service for the starter, so having had no problems with the Century when it came time for a new starting battery i went looking for a Century to replace it with but i was told where i eventually purchased the new battery from that Yusa Severe Service was more closely matched to the Marine Pro than the Century Severe Service in the rate and way they charge, meaning less on the alternator and better for the batteries.. So just ask the question when buying batteries, maybe you might get a different answer.
Also when you install the Redarc use good size cables, i used 13mm,, (not sure what guage that is,,) and installing the button to link the two is a good idea as i found out last week when the old starter battery died.

[drivesafe]

Hi Coupland and 100cruiser, for the type of set you are both using or planning to use Phils Lux would not only be the perfect set up but would save you some money.

As both batteries are going to be permanently mounted in the vehicle, they are going to be kept fully charged at all time while you are using your vehicle as your day to day drive vehicle so any battery will do the job you want. So the advantage that AGMs offer in being able to be left for long periods of time would not be an advantage to you

Again, as you are not planning on giving your auxiliary battery a hard time, ( just powering your fridge and a few lights ) flooded wet cell batteries will do the job as well as any other battery but cost less.

Now, regardless of some of the misinformation that floats around these web sites, if you prefer to run an AGM as an auxiliary battery, THERE IS ABSOLUTELY NO REASON TO HAVE TO CHANGE YOUR CRANKING BATTERY TO AN AGM.

This is one of the many myths that float around the net. This crap that you have to have identical batteries or they won’t charge properly, it just that, crap.

If in both your situations, you decide to get two identical batteries and you go away and camp for a few days, when you start your vehicle you now have two totally different charged batteries which is exactly the same as have one fully charged wet cell cranking battery and one partially to fully discharged AGM or the reverse if you have an AGM as a cranker and a flooded wet cell as an auxiliary and yet they will both fully charge while your driving.

People who say you have to have identical batteries have absolutely no idea of what they are talking about.

There are laterally tens of thousands of vehicles out there operating dual battery systems with dissimilar batteries and they are not having any problems.

Have a look at any motor home, the cranker is a flooded wet cell while the house batteries are nearly always AGMs and again, you don’t see them having ANY issues.

This myth just doesn't stand up to reality.

[100 TD]

Having 2 different batteries is no problems if you are using them for that purpose. If you do wish to use the "start assist" function of the redarc solenoid then I would run a much heavier cable to the rear battery. Something like 25mm sqd (actual copper conductor size) or 35mm (my preference) so you have little voltage drop when you go to start. Your deep cycle battery may not be designed for crank starting, however it will get you out of trouble if it is charged. If you only want the 2nd battery for a fridge/lights etc,(no winching) then a pure deep cycle battery would be best. If you want to mount it and forget it then a sealed AGM battery is the go, otherwise you need to mount it where you can get access to it to top up the cells with water. If mounting inside the rear of your enclosed tub, then AGM is the way to go with a piece of foam on top to catch any stray vapours (minimal usually)
There are many different brands about and many different prices $100 - $500 easy or more, one I have had a good run with is GNB Marathon M12V90F which equates to 100Ah over 20 hours (the usual standard), they are an AGM industrial network power battery and weigh 33 Kg ( a standard Hilux battery probably weighs 18kg if yer lucky) but there are lots out there.

[andy_beachbum]

I have a projecta kit from repco installed, i use the second batt to run a waeco 80lt fridge on my monthly beach fishing trips i go 3 days on a 90 amp hour batt (exide) and has no proplems with charge or going flat. It charges when the batt gets down to 12.4v and cuts charge at13.5 v

[Stealth Fighter]

I'll try to answer your questions directly.

Will this meet my needs or have I missed something?

It will meet your needs, although there are some other things to think about. The AGM is a great battery type, although more expensive. If you intend to mount inside a canopy then an AGM is the way to go as it eliminates the need to vent (safer for puppy, and less stuffing around). They also accept charge quicker so quick trips while camping are more beneficial.

AGM batteries are MUCH more vibration-resistant, can be side-mounted and have many different terminal options. Ie. they're more adaptable and will last longer in serious off-road applications.

As someone else mentioned, the cables are important. My advice is to steer clear of the auto places and head straight to BOC gasses for some welder cable. This is identical to good quality battery cable, only a fraction of the price (you will have to get someone to affix the cable ends though).

Will an AGM battery give me the best possible amp hours for the above camping scenarios?

No. At this stage, the best amp hour ratings are still being achieved by wet cell batteries. AGM's are not that far behind though. As your battery will be tray-mounted, you are not restricted to a normal NZ70 size battery. Stepping up to the next size in an AGM will give you the equivalent amp-hour rating to the best NZ70 size wet-cell (about 120ampH). Remember that you can lie the AGM down to fit under a console!

In terms of which AGM to buy, it is important to look at the specs and think about what it will be used for and where it will be mounted. The casing type is important if it is to be under-bonnet mounted as heat can distort some AGM's. The batteries using casings that are distorted by heat are cheaper but no lesser in any other regard, ie perfect for tray mounting.

My picks are: Deca Intimidator for under-bonnet cranking, Full-river for under bonnet accessory use, and I forget the name of the cheaper one suitable for tray mounting (as mine are both under-bonnet).

I take it is better to have the crank battery and auxiliary battery of the same type?

Makes no difference at all!

BTW, If you may ever, even possibly maybe one-day might remove the cargo system to transport stuff in the tray, put the effort into installing an Anderson Plug into the 2 battery cables in the tray so the battery can easily be removed!

I hope that helps,
Bernie....

[sudso]

Now, regardless of some of the misinformation that floats around these web sites, if you prefer to run an AGM as an auxiliary battery, THERE IS ABSOLUTELY NO REASON TO HAVE TO CHANGE YOUR CRANKING BATTERY TO AN AGM.

This is one of the many myths that float around the net. This crap that you have to have identical batteries or they won’t charge properly, it just that, crap.

If in both your situations, you decide to get two identical batteries and you go away and camp for a few days, when you start your vehicle you now have two totally different charged batteries which is exactly the same as have one fully charged wet cell cranking battery and one partially to fully discharged AGM or the reverse if you have an AGM as a cranker and a flooded wet cell as an auxiliary and yet they will both fully charge while your driving.

People who say you have to have identical batteries have absolutely no idea of what they are talking about.
He didnt say identical, but the same type.
True that both batteries or more of different types will recharge but why is it then that so many auto electricians etc say that different types of batteries recharge best at rates particular to the battery type.
eg: I know an auto electrician who will only recharge certain batteries on an electronic pulse charger and he recommends the same types of batteries in a dual system unless theres the possibilty of the aux battery being totally drained then he recommends deep cycle for the aux because they can handle being drained over and over.

My dual system powers everything from both batteries when they are linked via a solenoid as soon as the key hits the Acc2 position, so naturally mine are the same type, although not identical.
All the "non essential" accessories not required for driving are connected to the aux battery so I can still use them off the aux battery only with the key off, and batteries are isolated from each other.
The aux is a wet cell Marine Pro with deep cycle ability although not a true deep cycle and the main is a 700CCA Yuasa.
What do you think of this set up?

[drivesafe]

Hi Sudso, the tag “Deep Cycle” is used as a label for many different batteries and many times, as in the statement by the autolec, it needs to be clarified as to what type of deep cycle they a actually talking about, but thats another story.

As to your system, battery wise, it’s fine but as to your means of connecting them together, a word of caution, this is a common set up with a common drawback.

12 volts relays can be energised with as little as 8 to 9 volts and this is where a problem come into play.

You can have a cranking battery that has dropped a cell. In this state the cranking battery will not start the vehicle but it has enough voltage to energise the relay which then brings the auxiliary battery on line and the vehicle is started.

The problem is that until the auxiliary battery gives up the ghost, you don’t know the cranking battery is stuff and as is now obvious, you now have two stuffed batteries.

[sudso]

Yep, understood. I have a hydrometer to check the cells, so far they've been good but both batteries are only just over a year old. I did have a ground problem where the negative lead from the main batt joined to the body (bottom of batt tray on the GQ) but I've cleaned it all up since and put some some anti corrosion gel around the joint. The 1st cell (next to the negative post) was low on water which made me look for a problem.

Hi Sudso, the tag “Deep Cycle” is used as a label for many different batteries and many times, as in the statement by the autolec, it needs to be clarified as to what type of deep cycle they a actually talking about, but thats another story.

A Marine Pro cranking battery with deep cycle ability in my case. My means of joining them together is an Ingram solenoid (no voltage sensor)
cheers

[sudso]

I take it is better to have the crank battery and auxiliary battery of the same type?

Makes no difference at all!

Many auto electricans will disagree with this if the batteries are being used in parallel. You're hardly going to use a deep cycle aux and a wet cell cranker together to winch or crank the engine are you?
They in fact recommend that parallel batteries are the same type and as closely matched as possible using a constant duty solenoid to link them.

When a fridge is connected to an aux battery and the aux is also used in starting the engine, would the current draw to start the engine be enough to drop the voltage enough to fridges (that have low voltage sensors) for them to trip out? (low voltage sensor shuts off fridge and display reads error) Just thinking of how headlights etc dim when starting an engine with them on.

[steveandviv]

Many auto electricans will disagree with this if the batteries are being used in parallel. You're hardly going to use a deep cycle aux and a wet cell cranker together to winch or crank the engine are you?
They in fact recommend that parallel batteries are the same type and as closely matched as possible using a constant duty solenoid to link them.

When a fridge is connected to an aux battery and the aux is also used in starting the engine, would the current draw to start the engine be enough to drop the voltage enough to fridges (that have low voltage sensors) for them to trip out? (low voltage sensor shuts off fridge and display reads error) Just thinking of how headlights etc dim when starting an engine with them on.

To right. In fact just the compressor starting can be enough to error the fridge while letting the fan run so the above is very true.

Persoanlly I just use a custom pair of jumper leads if I need help to start the truck. I'd rather keep the start battery and Aux battery seperate, no relays no switches. They are used for different things and that's the way I want it. If I get stuck though a quick jump does the trick or being a manual - I park on a slope - just in case :D

[ROVERNIT]

I have a projecta kit from repco installed, i use the second batt to run a waeco 80lt fridge on my monthly beach fishing trips i go 3 days on a 90 amp hour batt (exide) and has no proplems with charge or going flat. It charges when the batt gets down to 12.4v and cuts charge at13.5 v


Hi there Andy is this unit you talk about Projecta (http://www.projecta.com.au/catalogue/cid/22/asset_id/52/) what did it set you back

[chopper37]

Hi there Andy is this unit you talk about Projecta (http://www.projecta.com.au/catalogue/cid/22/asset_id/52/) what did it set you back


ROVERNIT
I got a Projecta kit from Repco for $266. It's the DBC150K model. I called a few places but they either didn't stock them or they were around that price anyway. I liked the simplicity of the Projecta kit, installed it myself a few months ago and it seems to be working fine.

[gprunescaper2]

excellent thread!!!

[chevrodeo1]

Yes, ace thread. As far as i know, wet cells have a build failure rate. It used to be @ 30%, but don;t know recent stats. I have always been told that a constant low draw on wet cells can wreck them after 20 to 30 times, i.e. mrs uses a car bat to pwer electric fence, runs to flat, then recharged, tested. In 2 yrs wrecked 3 batteries. She lashed on a deep cyc. Almost 4 yrs later,constant use, no probs.
It does something to acid and i can't remember details, but it boils at charge, shows 80%, but loses charge in a day just sitting.
Good book-The 12 volt bible second edition. Laymans terms, very informative, i'm not electrically minded as others, just basics, but learning heaps from this book.

[99disco]

hey guys just a quick word if you are going to put your second battery in the tray i would use bigger cable than 6 b&s i think you will find that you will have a little to much volt drop over that distance witch will make your second battery take longer to charge i would go about 2 b&s or so the extra few dollars will be worth it and make sure to run power and earth to make things work even better

[aaronb]

Having 2 different batteries is no problems if you are using them for that purpose. If you do wish to use the "start assist" function of the redarc solenoid then I would run a much heavier cable to the rear battery. Something like 25mm sqd (actual copper conductor size) or 35mm (my preference) so you have little voltage drop when you go to start. Your deep cycle battery may not be designed for crank starting, however it will get you out of trouble if it is charged. If you only want the 2nd battery for a fridge/lights etc,(no winching) then a pure deep cycle battery would be best. If you want to mount it and forget it then a sealed AGM battery is the go, otherwise you need to mount it where you can get access to it to top up the cells with water. If mounting inside the rear of your enclosed tub, then AGM is the way to go with a piece of foam on top to catch any stray vapours (minimal usually)
There are many different brands about and many different prices $100 - $500 easy or more, one I have had a good run with is GNB Marathon M12V90F which equates to 100Ah over 20 hours (the usual standard), they are an AGM industrial network power battery and weigh 33 Kg ( a standard Hilux battery probably weighs 18kg if yer lucky) but there are lots out there.

When you say "35mm sqd", would that be the same size as a 35mm sqd electrical cable that would be used in factory wiring, or submains into a house?

[100 TD]

When you say "35mm sqd", would that be the same size as a 35mm sqd electrical cable that would be used in factory wiring, or submains into a house?
CORRECT, however, mains cable in a house has a few strands of heavy wire, where auto cable has lots of strands of fine wire. This is the same as welding cable (a good source to buy it from is welding shops as well), it has lots of strands of fine wire to make it flexible for auto use. You can of course use solid copper bussbar if you want, (which I do between my battery and redarc solenoid and between my battery and fusible link block) but it has the disadvantage of not being flexible and easy to use.

[aaronb]

Question for experts- I have a GQ patrol, TD42, i just installed a second battery, now when the motor is running, just with one battery hooked up, the charge voltage is 14 volts, give or take a few millivolts. Now when I hook up the second battery in parralell, it jumps up to 18 volts, which I dont think is right. Thought it may have been a regulator, but i disconnect second battery again, and it drops back down?
Any ideas???

[aaronb]

I am also using a starter motor solenoid from super cheap, was working fine switching for a couple of days, now it blows the fuse everytime it goes to turn on.

[100 TD]

Where are you measuring the voltage?
Have your headlights turned on pointing at the garage wall and look at the brightness.
Measure the voltage at the battery POST and at the alternator terminal. It should be 13 to 15 volts DC - (make sure you select DC- on the meter not AC~)
Is your second battery dead flat?
Hook up your second battery in parallel (positive to positive, negative to negative) with your good quality heavy duty jumper leads.
You should see the voltage drop and then slowly rise again. You should also see your headlights dim slightly and then slowly increase. (if they get very bright then your voltmeter is probably telling the truth)
Possible reasons you may see 18 volts.
A poor quality volt meter is unable to filter out the ripple from the alternator and not give you correct DC readings.
Meter accidently set to AC instead of DC and is measuring ripple.
When you place your flat battery on your syatem, it puts too much load on the alternator and the regulator can't handle it and goes full noise and tries to output too much.
Your regulator could be faulty.
Depending on where you are measuring the voltage and where you are connecting the second battery, if your alternator is externally sensed, there may be a poor connection between the sense connection and the battery so the alternator is incorrectly setting the output voltage due to the fact there is a large voltage drop occurring when higher current is flowing.

[aaronb]

Alls good now, the cheaps shit solenoid from supercheap wasnt built for continuous duty, and was causing the voltage to read at 18 volts. Put in a continuous duty solenoid and all is well. Running the fridge and the kids DVD players nicely.
Thanks for your help 100 TD, I am an elecrtician, just couldnt figure out why the extra voltage, when all i did was add a battery

[Gixer]

Has anyone got any info about twin alternator systems? I am setting up Duel batteries and noticed that my truck has aftermarket brackets mounted that look like they have been used to set up a second alternator. I was thinking the second alternator might be a good idea as it wouldn’t cost much more than an isolator unit and with a good AGM battery and a dedicated charge it should decrease charging time. I have a 9 day trip planned:waycool: and am running a 95L fridge and a few other camping related items but will only have maybe an hour or two driving maybe none at all some days. What are your thoughts? If anyone has any wiring diagrams for Twin alternators that would be great.

[Coupland]

When earthing the second battery in a dual battery set up, do you have to earth to the chassis or can you earth to the tray well body?

Also, the Redarc instructions state that I need to use 2B&S cable (with 100amp fuse) if I intend to use the over function and the cable lenght between batteries is 5 meters. Is this excessive? I only need 6B&S (with 60amp fuse) if I don't use the over ride switch...

[100 TD]

Bigger cable means less voltage drop and faster and better battery charging and also allows jump starting, you have to decide what you are happy with, if you NEVER want to use your second battery to jump start your flat main battery then go with the smaller cable.
Earth to the chassis preferably (you body as well if you wish), your main battery should be earthed to the chassis and engine (as well as the body) however a chassis earth is the best for the lowest voltage drop, which also helps your cause for charging your second battery.
New heavy cable is expensive, second hand welding leads are good, you may be able to get some from a metal recylcer. Bigger cable is always better.(to a point)

[alex_cs]

im using a redarc with the optional overide function mounted under the steering wheel, with two supercharge gold 760cca batteries (MF95D31L). thing to remember is most deep cycle batteries dont have much of a warranty, these supercharges have a 24 month warranty. some testing by me and a deep cycle i already had, i got an extra 24 hours out of the supercharge before the engel stopped operating. for 160 bucks each, i have to say im a convert to dual starters, rather than a starter and deep cycle.

having said that, the longest i sit without driving again is 48 hours or so, there must be better agm or deep cycles out there that will last for 4+ days. it totally depends on what you want out of a dual batt setup.

[Coupland]

Well it has taken awhile since I first started the thread but I have wired up the dual battery system (with help from a mate) on the Lux. Now to head away for a few days and give it a work out.

[JayD]

Can a Fully sealed AGM battery be used as an aux battery in the rear of a wagon? I have a Suzuki GV, and there is no way I can get a battery under the bonnet, yet I would like to be able to run my frigde for a few days, without the stress of not being able to start the vehicle. Would it be safe, esp with two ruggies in the back seat??

[100 TD]

YES, as long as it is certified to do so, I'll let you check the specs of your battery against the regs!
I haven't a problem with AGM batteries internally in a vehicle, but with differing standards in nearly every juristiction in every country/state or territory worldwide, you have to be cautious. Lots of ventilation........ the list goes on!

[A1 Mech]

If the battery is a sealed type unit then yes u can fit it to the interior of the car as no charging gases are emitted. This is what I have done with my old girls prado as I could not be bothered moving stuff in the engine bay to accomode a large battery.

I recently bought a dualbattery kit from BCF for the prado designed for marine applications, It uses a single sense VSR as the switching relay and comes with lugs, 6m of 25mm cable, earth lead, cable ties etc for around $100, Works a charm and the VSR's are completely water proof.

There is a dual sense VSR which will accomodate and read charge from either battery but it isnt really neccessary in a 4x4.