Dual battery setup

[Old.Tony]

I've seen those Thumpa packs for a long time and every time I see it I wonder how they can continue selling them, they are SO overpriced it's not funny.

If you need to run the fridge, you could probably do it from a 50Ah deep cycle like I have in my tub. Assuming a full charge, I have 25Ah available (because I only rely on a max discharge of 50%). My fridge draws about 1.5A for about 50% of the time, so 25/0.75 = 33 hours of operation.

If your camp lights are LED based then ignore them in the equation. If they're fluoro, they will draw between 0.5 and 1 A each. Run a pair of those for say 3 hours and that's 6Ah lost to lights, so your fridge is left with (25-6)/0.75= 25 hours of run time.

That won't do you for 7-10 days - for that length of time (say 10 days), assuming the same fridge draw and the two 1A lights @ 3 hours a day you have 12*1.5*10 + 3*1*10 = 210Ah of power used for the entire period (notice, it's 21Ah a day).

Personally, I'd add a folding 80W regulated solar panel (5A in full sun, times 5 hours = 25Ah returned every day) and you won't have a problem, ever. You could get a generator but they're noisy buggers and it's rather cool having a folding solar panel that does the work for free and never needs fuel, oil or earmuffs.

 

[AN97RY]

thanks guys, i only need to run lights for cooking, kids portable dvd's and later a fridge??

 

[KraftyPg]

As Tony said LED lights will have minimal effect on your battery so if you're running LED it's not a huge issue. Portable DVD's are usually fairly low powered as well, I picked up a dual DVD unit yesterday and it's rated at 6W which really isn't much. Your fridge will obviously be the major power drain but unless you know exactly which fridge you're getting it's impossible to say just how much. Either way you don't need a $1000 set up.

 

[belly760]

I've seen those Thumpa packs for a long time and every time I see it I wonder how they can continue selling them, they are SO overpriced it's not funny.

Thanks Tony. I suppose i was seeing the 90ah battery pack with the 1000 inverter and charger all in one and was thinking that with all is componantry it could be priced reasonably. But had not really done the sums on what each componant is worth.

Thanks for the feedback

 

[NWQD22]

Not sure if it has been mentioned before, but I thinking about installing a battery box to the tray and having it connected via an anderson plug so as battery can be removed when camping/BBQ's etc. Was going to install a isolator switch in the engine bay so cabling can be terminated when not in use. Has any one else tried this and is there any pro's cons of this?

 

[joshman]

Not sure if it has been mentioned before, but I thinking about installing a battery box to the tray and having it connected via an anderson plug so as battery can be removed when camping/BBQ's etc. Was going to install a isolator switch in the engine bay so cabling can be terminated when not in use. Has any one else tried this and is there any pro's cons of this?

yeah mate, i did almost the exactly same thing. Off the positive terminal of my cranking battery I ran an 8AWG cable through a 30A self-resetting Circuit Breaker, along the chassis, and into my tub. I Picked up an earth about 2/3rds of the way along my chassis. In the tub I ran to an Anderson Plug (effective and solid method of connection and isolation). I then wired in a REDARC BCDC1220 (look it up) with the input Side to an anderson plug, and the output, through a 25A fuse then straight to a second battery. In my case i went for a 100Ah GEL type Deep Cycle.

Then off that battery I'm running a fridge and eventually lights, and other accessory points. Long story short, it's simple, cost effective (for my intended purpose) and easily do-able yourself.

 

[Old.Tony]

Not sure if it has been mentioned before, but I thinking about installing a battery box to the tray and having it connected via an anderson plug so as battery can be removed when camping/BBQ's etc. Was going to install a isolator switch in the engine bay so cabling can be terminated when not in use. Has any one else tried this and is there any pro's cons of this?

Are you saying that you want to remove the battery from the engine bay while camping, or just isolate it where it sits in the engine bay from the starter battery so that it doesn't drain it while you're camping?

Naturally both solutions are good, the second one requires less heavy lifting so that's a bonus, but does mean that you have to keep your car fairly close to proceedings AND you can't go get firewood and keep the fridge running at the campsite.

An isolator is a good idea in either scenario, and Jaycar sell a 500A isolator for $17.95 and it will do the job.

 

[terryc]

Joshman How much was the Redarc unit?

 

[joshman]

REDARC.com.au and ARB will try and sell it to you for $500, i found mine on eBay for $359 delivered.

It's a fantastic unit though. Isolator and DC Battery charger in one unit, very versatile and very awesome.

 

[glennm]

Joshman what model redarc have you got?
BTW great info on this thread and the site in general.

 

[NWQD22]

Not sure if it has been mentioned before, but I thinking about installing a battery box to the tray and having it connected via an anderson plug so as battery can be removed when camping/BBQ's etc. Was going to install a isolator switch in the engine bay so cabling can be terminated when not in use. Has any one else tried this and is there any pro's cons of this?

It would still essentially be a traditional dual battery system, with the bonus of being able to remove the battery box when not required to free up tray space or be able to use it in a mates car etc. Was thinking of the isolator switch in the engine bay so all wiring is terminated/tamper proof when battery not installed/in use. I have a battery box (bought from BCF $80) which has a LED battery gauge and several power outlets with a 100AH battery (not included) was thinking about something like a red arc unit to keep it charged when travelling etc. Will try and put some photos up later

 

[marke9892]

under bonnet duel battery

Has anybody put a second battery under the bonnet of a D22 Navara with a factory snorkal looks like a lot of trouble to move everything.

 

[terryc]

Has anybody put a second battery under the bonnet of a D22 Navara with a factory snorkal looks like a lot of trouble to move everything.

uMM, WHAT YEAR?
Mine already has two {.

 

[nic.t]

great read,

can some explain the importance of amps and should they be matched to battery CCA, AH etc?? I see a lot of dual battery kits ranging from 140amp through to 275. Is a higher amp rating better for certain accessories and why?

NICK

 

[Old.Tony]

CCA is how much power the battery can deliver to start your engine. Our starter motors use up to 550A just turning the engine over. A battery that isn't manufactured to deliver that much power at once will have a very short life.

With auxiliary items, the CCA is not important, the "RC" value - Reserve Current - is the figure to look at. It determines how many hours the battery can deliver a certain amount of power.

If you work out your load - say a 4A fridge that runs 50% of the time, and some lights that use 2A for 6 hours - then in a 24 hour period you'll use 4x12 + 2x6 = 60A. A good battery size to meet that demand is a 100Ah battery.

You can underspend and buy a battery that only just meets your needs. Doing that means your battery is 100% discharged by the end of the day. Fully discharging batteries kills them fairly quickly and many fridges these days will stop operating below a battery's 20% remaining power anyway.

You can also overspend. If you can charge a battery up every day, or you only need 2 days' worth of power, there's no point buying 4 275Ah batteries to supply that fridge and the lights "I got a good deal". Buy ONE decent battery and perhaps invest some in a good monocrystalline solar panel and charging regulator.

Which battery type? NEVER choose gel. Choose from high-maintenance but cheap "flooded" batteries, or low-maintenance but expensive AGM batteries.

 

[joshman]

Hey tony, I'm starting to suspect that you don't like gel batteries...

 

[Old.Tony]

You're right, but I'd be interested to see ONE good reason why I should choose a gel battery over a similarly-priced AGM.

Both are spill-proof. Both are structurally more sound than flooded batteries (the AGM is FAR moreso). Both are considerably more expensive than flooded batteries.

The problem with Gels is threefold: first, they have a different charging voltage limit - 14.1V, compared to 14.7 (alternator power) of an AGM/flooded. Second, a slight overcharge causing a little gassing in an AGM/flooded is no problem at all, whereas in a gel the bubbles that form at the surface of the plates STAY at the surface, becoming an insulator, killing the battery. Third, and AGM (or flooded battery) can have mild sulphation reversed by a decent charger (eg C-Tek) extending the battery's life. Attempting this on a gel battery kills it almost instantly.

Actually there's a fourth reason. Gel batteries can't be charged at anywhere near the same rate as flooded or AGM batteries. Charging them at too high a current also destroys them, so using a 50Ah gel battery (which can be charged at UP TO 2.5A) in a system with an 80W solar panel (5A) is going to kill the gel battery anyway. Plus, if you can only recover 2.5A per hour, and your usable solar time is 10 to 3 = 5 hours, at most you can put 12.5Ah back into the battery.

There's really NO point in using a gel battery. Here's another site that mentions them (and why they're bad, and compares the different types).

 

[Boxy]

hey old tony

you seem very up with all this electrical stuff just a quick question im about to fit my dual battery system for my second battery will be deep cycle , wondering wether it will be a problm to hook 2 brand new exactly the same batterys in parellel just to give me double the amp hour for running light and fridge

sorry not meaning to hi jack the thread just wanting to get some infor from someone that can probably give me pros and cons

cheers boxy

 

[Old.Tony]

As long as the batteries are identical and as close to the same manufacture date, then pairing them (running them in parallel) won't be a problem.

That sort of thing only causes problems with the batteries are not the same and the problems arise when charging.

Let's say you're got two batteries in parallel, one a 50Ah and the other a 100Ah. The battery charger will start charging and both will initially draw similar power from the charger (half the charger's output each).

The 50Ah battery will approach 'full' sooner, of course, and its voltage will rise faster. The battery charger will see the rising voltage and will assume the batteries are charged - thus cutting off (or reducing) the charge current. The larger battery will then draw power from the smaller battery to achieve balance - so neither battery will fully charge.

This is also a problem with in-car charging systems that rely on isolators alone. The way to prevent it is to isolate the auxiliary batteries from the voltage as well - which means either a DC-DC charger, or an inverter+240V charger.

 

[sparra04]

hey old tony

you seem very up with all this electrical stuff just a quick question im about to fit my dual battery system for my second battery will be deep cycle , wondering wether it will be a problm to hook 2 brand new exactly the same batterys in parellel just to give me double the amp hour for running light and fridge

sorry not meaning to hi jack the thread just wanting to get some infor from someone that can probably give me pros and cons

cheers boxy

mate check my build thread
i have just done exactly what your enquiring about