Dual battery setup in a standard car?

I would suggest put removable deep cycle one in back (i.e. remove it with fridge or still better make it on the same tray with fridge), install inverter in back (great thing anyway) and charge your second battery with good charger (like CTEK or similar). AFAIK there is nospace under bonnet and you will not be able to charge so remote battery efficient without complex charging system. I know people shifting battery to boot, but it is because they want bigger capacity to run audiosystem and have not seen any double installation. Check also audiophile forums.
Cheers

Great suggestion. I'm not really up to speed on the battery terminology. Is N70 slightly larger than the standard car batteries?

Oh, and can a deep cycle battery reliably start a car?

Garbage........... :-))
First thing is to see if the bigger battery will fit. The Exide Extreme N70ZZ for example is 300mm long, 220mm high and 175mm wide. It most likely to be the same height, equal or greater width and about 60mm longer. You may or may not need to slightly move something. This size battery is used in all the big diesel 4wds, and trucks - its a very common battery.

This battery (in good nick) will run a Waeco 52 litre for 2 nights, and still be able to crank a petrol powered Subaru. A 4cyl petrol vehicle cranks easily off a big battery.

"can a deep cycle battery reliably start a car?"
Yes, easily. I can crank my diesel with a deep cycle battery. But I'd warn you off deep cycle batteries. They take a bit longer to charge up, and may not easily become charged. As a result, they may not last as long as a cranking battery. I always use cranking batteries - even for deep cycle applications, because the number of times you actually cycle it will be few. They only come with a 6 month warranty because of this.

I also would not use a sealed gel or AGM battery under the bonnet - they are very costly, and anecdotally, I've had friends have them fail prematurely under the bonnet, perhaps because of heat.

Theres a downside to everything. If you go with a single battery, and that battery dies, you have no backup - really only an issue if you travel alone and in remote areas. Some people carry one of those jumpstart packs to back up a single battery.

If you put a sealed battery inside the cab, it can't be a wet cell battery because they can release hydrogen and go boom. Some people reckon an AGM battery is safe, but I believe its still possible for hydrogen to be released, and maybe the authorities would require any battery in the cab to be vented outside????? Up to you.

Thanks Phil! Some very good info in there. I guess all I'm after is a battery that can get my fridge through until the next time I hop into the car and drive for about 30 minutes (would do this everyday). The fridge I'm wanting to run is a generation II Bushman. The spiel on the web site claims:

With the refrigerator set @ -4C with an ambient temperature of +24C the BUSHMAN uses a mere 16amp hours per day

The fridge also has an auto cutout when the battery approaches the point where it won't start the car.

Now, I have no idea how many amp hours my current cranking battery is, but I did end up measuring the space available - 250 x 150 x 210 (approximately) so it looks like the Exide you mentioned won't fit. Without really knowing what I was looking at, I found a 60AH AGM battery that would fit there. If you know of any other cranking or AGM batteries that would fit this and give me as many amp hours as possible, do let me know.

Another question - what would I need to do so that I would not have to leave the keys in the ignition in order for the battery to be left running?

30minutes will get a lot of power back into a single large cranking battery.

Power consumption of a fridge - all the manufacturers quote different methods to confuse the buyer, but I'm sure the Bushman would be a good fridge. I dare say they assume that you'll never open the fridge :-)))

Test the auto-cutout at home, by running the battery down with headlights and then the fridge. Worth knowing what voltage it really cuts out at and whether you can easily crank the car at that temperature. Having a digital voltmeter is a very handy way of getting to know what your battery is doing.

Worth taking the vehicle to a battery dealer to see what is the biggest size you can fit. Can you move anything (fusible links, relays etc) to go for a bigger battery??? But next size down is an N50 battery - 261Lx173Wx225H. The N70 exide extreme is 80Ah battery. I'd guess the N50 to be about 65-70Ah. I'm a fan of wet cell deep cycle batteries under bonnets. They last well. Jury is still out on Chinese AGMs IMO.

Leave the keys in while running - sounds like a turbo timer is needed - not sure you'd get one that goes for 30 minutes. Theoretically theres a legal issue - not allowed to leave a car running then walk away. Up to you.

""Jury is still out on Chinese AGMs IMO""

Some Good batteries do come out of China (Asia) as it also could be said some fairly 'average' batteries are also made in the good ol US of A.
After all, some of these Chinese battery companies have AS of A connections lol.
Those who buy quality products are often happy, it's only when some-one says they have a cheap 'import' agm and they are happy with it, that it makes you wonder what they had previously to be able to make the comparison.

If the specifications are correct, using proven technology and it has a decent warranty to back it up, the place of manufacture is unimportant IMO.

Fair point about Chinese goods. I included it as Chinese AGMs seem to be the big sellers in the RV market, rather than any reflection on their quality.

If I can rephrase
"Jury is still out on the longevity of AGM batteries under the bonnet of a 4wd." I know a few anecdotal instances where someone has paid $300+ for an AGM or Gel battery, and had it fail in under 2 years.

In 10 years time, we'll have a better idea of how they last in an environment of heat, vibration, deep discharge and a 14.0V alternator. Specifications are worth didly squat with the way many of us need to use our batteries.

I would put battery in saloon, *BUT* (and it is big but) only fully sealed spill proof one (read expansive one). Please note then some such battery have different voltage - nothing to do to fridge, but something to charger.
Cheers.

Personally there is no way on gods earth I would place a battery anywhere near a person especially a child. Not having a go at you in any way as you just asked a question. BUT in the event some thing went wrong eg exploded, accident, faulty electrical, what ever, in the event that your child copped a facefull of acid you would never forgive yourself. The chance of it happening is probably zero but personally I would never take that chance. Regards Steve M

Thanks for the heads up :) Definitely be crossing that off my list then. Does that mean it's also unsafe to keep the battery in the back of the stationwagon?

Absolutely Steve and yes garbage keep the battery out of the car. I think the best suggestion is to use the car battery or a larger replacement if you choose and carry a Jump Starter. They are a great back up too because the best of batteries will fail with little or no warning at times and the Jump Starter will get you going.

Well, there are batteries and there are batteries.

My own experience tells me a portable battery system such as the "Thumper" will solve your problem. It can sit on the floor or anywhere else you decide. The only thing I would recommend is that it is secured in some way, "just in case".

These portable battery systems are perfectly sealed and come with their own in-car charging units. My recommendation is a unit of around 75Ah. The best thing is they can be easily removed from the vehicle along with the fridge if you are setting up camp with a tent, etc. They already have both cigarette style and merit style sockets to plug the fridge into and the in-car charging kit includes the correct cable, Anderson connector, etc.

Although I also have a dual battery system in the car, the Thumper gives me total flexibility and extra capacity at camp. I also use it to run a camp light. (piranha fluro)

You can buy versions that give you the backup of jump start capability, or you can save a little money and do without this feature if you wish.

Home of 12 Volt

Put an AGM Deep Cycle battery under the kids feet.

AGM's don't give off gas or explode, when has anyone heard of an AGM exploding when NOT in the engine bay Grrr.

AGM's are suitable as air freight because they don't gas and they can be placed on their end or side with-out any problems at all.

I sleep beside an 100+ AH AGM Deep Cycle battery in a plastic box every night.

Mainey,
Ever seen what happens to a battery when it gets accidentally shorted??

Phil,
Nope, I haven't had the experience of seeing a battery that has been shorted accidentally.
Probably because I've never advised installation of a battery in a way that would allow that to happen, as I believe fuses are dirt cheap insurance to avoid accidental shorting.


However the question was:-> ""There is some unused space on the floor area under my 2 year olds child seat.
IS THIS A SAFE PLACE to put a deep cycle battery, assuming it's SACURELY bolted down? ""

I didn't go into the complete details about each & every component of the installation of the battery & cables at the time of replying to a post that simply asks "where to & how safe" is it to place the AGM battery under a 2yo child's feet, because it's not HOW to install the battery, but WHERE to fit it in the car.

The battery would (obviously) be installed in a battery box, it would be fused to eliminate shorting due to poor shielding at the point of entry through the 'firewall' into the interior of the car.
The 2yo child could safely put their feet on the battery box and it would not cause it or the AGM battery any damage.

Mainey, I raised this point because there are a lot more safety issues than the theoretical ones that everyone reads on battery sites.

#1 This is a forum, and 99% of people are not autoelectricians.
#2 90% of the people on this forum would not put a fusible link on the battery thats sitting under the child's feet.
#3 99% would run the cable thru the firewall and into the cab to reach the battery.

Then say something simple happens - the passengers front seat is tilted forward and the pos lead gets stuck in the latch - this latch cuts thru the conduit and insulation. The battery will melt and may explode or catch fire, the cables catch fire from the huge amperage from a dead shorted battery. I've seen it happen twice under the bonnet. In both instances, a battery was changed to a marine battery - the posts were slightly wider spaced, and when the bonnet was shut, the edge of the bonnet came down on the pos terminal. Nothing was noticed until a few days later when the paint wore through, and the terminals were dead shorted causing a fire, which nearly destroyed one of the vehicle. Would be a disaster inside a vehicle.

IMO we can never be too careful with advice given on a forum.

Garbage, Waeco sell a 40 amp battery pack that would be safe in a vehicle.
Its not great value for the power,(about $345)but its compact and versatile with 12V plugs for lights etc and as I said before should be safe enough inside a vehicle if its secured.

Use it when stopped for the night and recharge whilst on the road

Phil, yes accidents happen, however I only posted WHERE to fit the battery, not HOW to fit it.

I always run cables under the carpet and against the wall where there is no chance of pressure from feet or loads being placed on them, to avoid the problems you have described.
I have at least 6 or more elect cables in my vehicle all running from front to back in this way.

As to fuses, I always advise fitting fuses close to the battery, at each battery if it's a long cable run.
That said, I don't have a fuse between my two AGM's, they are about 1.8 mt apart, I use 32mm sq cable (yeah, some may say overkill) which is protected by a shield at every position likely to touch anything, at close intervals the shield is tied with large cable ties to something stable so it can't rub on anything.

However the fridge circuit is protected by a ceramic fuse.

Obviously a case of 'do as I say' and definitely not do as I do :-((

Ross, I've seen those Waeco and Engel incarnations of deep cycle batteries around. The question is - can those be discharged below 50% regularly without damaging the battery?

Garbage,I dont know too much about the specs,but my brother had one when we went to Ayers Rock and back and he was happy with it.He had his Waeco 50 running off it when stopped overnight
It probably cuts out when its too low.
I just thought if you have to carry something inside a vehicle ,this would be the safest option if it was secured

Garbage,I have a 100 amp wet cell I bought for $240 and keep it in the back of my ute in a battery box and can run the fridge for about 4 days under ideal conditions(just me ,no kids) before it drops too low

In reference to the "thumpers" and Waeco battery packs, what 'type' of battery technology are they ?

Umm, are they common wet cell - agm - dry - ni-cad or just plain 'D' duracells ??

Reason I ask is, if thumpers and Waeco battery packs are actually "stated" to be safe to be used inside a vehicle then why not use the same 'type' of battery technology, but in a much larger capacity in the vehicle with-out the fancy (expensive) container ??

After all they cost more than a huge capacity AGM battery
(which are the 'only' battery safe enough to be sent as air freight)

Mainey,

The Thumper is an AGM technology.
Inside the case is a series of smaller AGM batteries, (about 17 Ah each I think) and the quantity of these determines the overall capacity of the "pack".

The thing I like about the Thumper is the overall "package".
The case is a quality, pupose designed unit containing the input Anderson connector for charging the unit from the in-car charger, both "cigarette" style and Merit style sockets for connecting devices to, a voltage display in the current models and in the model Thumper I own, another Anderson connector to connect a pair of included jumper leads for emergency starting, should the starting battery go flat.

I'm not tied up in any way with the manufacturer (Blue Apple) but the Thumper undeservedly obtained a poor reputation when it was previously linked with Waeco. People were using "Waeco Thumper" portable battery systems that were way under the capacity they required to run whatever devices they had, so they blamed the battery system.

As I understand it, Blue Apple wished to make higher capacity units for a myriad of different functions and under the arrangement with Waeco, were restricted in what they could market.

So the two companies split and now the Thumper is just one of a range of portable battery systems produced by Blue Apple.

You mentioned the cost of these systems, but when you look at the current range of what's available and the quality of the product, I believe it is justified. Blue Apple released models that don't have the "Jump Start" capability to reduce the cost to consumers that don't require this feature.

Mate, I just love the flexibility my Thumper gives me and I don't travel without it. I have the in-car charging kit to keep it charged whilst travelling and can also connect a solar panel to one of the ports to help maintain a charge while it is running the Engel at camp.

Why do I use the Thumper over other options?

I have in my shed, a battery "case" I once tried, containing a standard deep cycle battery. The lid was held on to the body with a strap and contained the handle to lift it. When you did so, the strap slipped and the lid departed company with the case body. My opinion is that these cases may be OK for some protection when resident in a camper or boat, but portable they are not.

The Thumper's case is a molded two piece unit that totally seals the contents and due to the AGM battery cells inside, can be used with complete safety, on any angle or plane. The use of the Anderson connectors mean there is no terminals that can accidently short out.

Hell, I'm sounding like a marketing person:-))

for more reference:-
Homeof12volt

Yes, AGM battery technology.

Thumper power pack

~$950 = 105 Amp Hour AGM battery capacity
~$349 = 30 Amp Hour AGM battery capacity

A 100 AH AGM battery in a $30 plastic box would be far less $$$ than the smaller 30AH system, and because it's the same AGM technology it will not be dangerous in the car.

It's a lot of money for a decent 'handle' lol

Are these essentially higher CCA and Amp hour batteries, just in a smaller package than the standard car ones?

Did a bit more research and came across a couple that would probably fit in the Soobie. Is there a way of figuring out how many amp hours these batteries are? I couldn't find it in any of the specs, nor did I know any formulas to convert any of their other specs.

Odyssey 925 battery
Pulse Battery PHB650

Thats a clever set up!

By last may I should have said May 2006

Thanks for the tip. I did end up going to the guys you recommended in Sylvania and picked up a 65 amp hour battery. It's been working well so far!

Cheers, nice to get a reply when a suggestion is found suitable :)

By now your last question about the ability of the alternator to charge an AGM has also been answered!

The hardest bit of installing mine was to lift it in - no handles, and pretty bloody heavy. Used a cloth sling in the end.

I ended up opting to just have a standalone battery charger as I'm never more than a couple of days away from 240v. Thanks for your help on this!

Short answer = yes.