second battery fitted

[stewie32]

Hi Guys
Have just installed a second battery to run fridge etc, want to know cheapest or perhaps easiest way to hook it up so as to charge whilst going along. Its a deep cycle glass mat type battery.
Ideas??

[Patrol'n]

G'day mate, I bought a red arc SBI12 kit off ebay, cost about $215 or so for the whole kit, then a bit more to install a couple of power points from Super Cheap. Was overall a very easy install and has been working well now since late last year. This also comes with the ability to jump start off the second battery if the first one goes flat via a button on the dash. (Although I believe it's not a good idea to use that feature with a deep cycle battery). The kit came with all the wires, connectors etc, and a reasonable set of instructions, so I was able to get it wired up in one arvo.

There are very cheap dual battery kits at Super Cheap when they have sales, I can't offer an opinion on the quality though since I haven't used one myself.

[4bye4]

VSR Voltage sensing relay. Redarc is probably the favorite, I have a Projecta and have had no issues with it. From what I can see they are pretty much the same.
Beware of very cheap modules on line - they may not handle the power very well.

[Rock Trol]

So your battery is an AGM? Is it under the hood. These batteries don't like heat as much as wet cell batteries and also are better charged at under 20 amps. I have a DEKA Intimidator under the bonnet which is supposed to be rated for under bonnet use and charge via Redarc BCC 1220 which is not cheap. 2.5 years old so far and still working without bulging.

What brand of battery do you have? In your case the cheapest option may not be the best.

[Getaboutabit]

x2 for not installing under the bonnet.
They really don't like the heat. I use redarc
Solenoid and charge off the alternator

[threedogs]

have you thought about running the fridge from a battery pack,
and charge via some 8mm figure 8 and 50 amp anderson plug,
in the cargo area;

EDIT avoid using Cig sockets they will fail,
use either merit or Anderson style plugs

[Cuppa]

In your case the cheapest option may not be the best.

Definitely agree with that.
What you need depends mainly on your usage pattern & what you are charging the battery with. Some alternators need extra help. Note: the requirements for charging a cranking battery are different to charging an aux battery - a crank battery will happily start your vehicle when only 70% charged - that’s why they only last an average of 4 years or less. A well treated deep cycle battery can provide good service for 10 years+, but wont if charged like a crank battery which is what a VSR does.

A crank battery provides a high current for a brief period of time & is then quickly charged back to where it was ready for the next start. An aux battery running a fridge has a lower draw but sustained over time resulting in a much larger chunk of it’s capacity being used.

If you are driving daily for reasonable periods of time a VSR will get you by.
If you want the battery to run your fridge over weekend trips, with ability to plug into a mains smart charger as soon as you get home, & you will be driving a reasonable amount over the weekend a VSR will get you by.

Both the above statements are dependent upon you having sufficient auxiliary battery capacity to meet the needs of your fridge. This is determined by the size of the fridge. The bigger the fridge the bigger the current draw & the harder on the battery it will be.

If you want to tour for weeks or months at a time, stopping at camp spots without driving & without regular stops to plug into mains power you will need more than a VSR.

A VSR basically charges your aux battery from the alternator, the same as it does your crank battery - this will not charge either battery beyond about 75% to 80%. Useable battery capacity is around 50% of the total battery capacity - IF YOU WANT IT TO LAST. Therefore with a fully charged 100AH battery you have 50AH approx of ‘useable capacity’. If charging via a VSR that useable capacity falls to around 25Ah to 30AH. If your fridge draws say an average of 4 amps when running on a 50% duty cycle it will use 48AH per day. So in that scenario a VSR charged battery will not keep up, whilst using a means to charge the battery to 100% will.

That means is a combination of a smart charger, (i.e.. a dc to dc charger) &/or solar (Solar regulators are also smart chargers). Some units like Redarc BCDC’s & Cteks combo units combine both. This is obviously a more expensive option.

Nothing wrong with using a VSR, but if doing so means you will use your battery until low voltage alarms sound or the fridge cuts out on a regular basis, your battery will have a short life. In these circumstances it is wise to buy the cheapest battery you can. In fact I’d say that if using only a VSR use a cheap AGM battery.

Probably the best budget system is to use a VSR to charge the aux whilst driving & to have some portable solar to connect to the aux battery whilst in camp. This way solar can take over from the alternator to top up the aux battery.

Better still, at a cost of course, is a system with roof mounted solar which charges from that alternator via a dc to dc charger & automatically switches to solar when the ignition is turned off. All sorts of variations possible.

Aiming to have a balanced system (i.e. one which will fully recharge the battery in every 24 hour period whilst running the fridge) is the ideal. Anything less sooner or later sees you chasing your tail & the beer getting warm.

[threedogs]

Whats the purpose for the second battery?? is it just the fridge or do you want to
run some LED lights when camping as well. What size[ah] battery did you buy?

[the evil twin]

The easiest and cheapest is to run a 12 gauge wire from the cranker to the aux thru a 100 amp relay.
Trigger the relay from the wiper motor +ve thru a switch (optional).

That means Ign On and switch On then the relay energises and the Aux battery gets charged whilever the engine is running

The optional switch is so you can prioritise the Cranker or remove the paralleled Aux if it is way low SOC for starting.
The wiper feed is so that if you turn off the engine and forget the switch is on then the relay de-energises so your Cranker stays charged

The VSR's you buy IE Redarc, Projecta et al are basically only an automated version of the above

Your Aux AGM will be fine under the bonnet AS LONG as it is spec'd for the useage and temps.
There are gazillions of AGM's available and a lot of them are for industrial applications (UPS etc) and need low charging rates and stable temps

Disclaimer... I agree with others 'the cheapest and easiest isn't always the best'

[Patrol'n]

I have to agree with Cuppa, to expand on my post above, my setup includes a 105AH 'dual purpose' battery, (so I can start off it in an emergency if required), a red arc SBI12 VSR, and a 100 watt solar blanket to use when camped in one spot for multiple days. I find a couple of days power without solar or mains charging (straight to the aux battery posts), is all I get as I don't like letting my voltage drop below 12 volts, although I went three days once, but voltage got down to 11.2 which I wasn't happy with. Using the solar blanket and good WA sun, I've had it go 5 days without dropping below 12 volts and without running the car. I run a 40lt engel, LED camp lights and charge the kids iPad/iPods etc when required.

If I was setting up a dedicated deep cycle battery in my truck or a camper van / trailer I'd go high quality AGM (or whatever the appropriate battery type was for install location), and use a dcdc charger or similar as Cuppa suggested. I would also work out what battery capacity I thought I needed and add a bit more capacity..... Just my opinion