smart alternator vs aux battery

Hi Mudguard,

What is the model of your new vehicle?

If you are using the 'allrounder' for the starting battery then I hope it will be getting sufficient charge as there are no options for modifying an existing new vehicle charging system without voiding your warranty.

So as they say.....who you gonna call?


An 'allrounder' is just another name for a slightly different configured standard battery. No big deal. In fact they're old hat nowadays. Better options available.

Mudguard,
I'm not sure you'll do yourself any favours with the Allrounder as your only battery.

I have the battery manufacturer's instruction sheet for the Allrounder. It says:

1) Select a charger that will deliver a current of one tenth of the C20 amp-hour rating.
So if you have an MRV70 with a 105 Ahr rating, it should be charged at about 10 amps - not the 40 or 50 that your alternator might deliver to a low battery.

2) Charge (at C20/10 amps) until the battery voltage comes up to 15.5 and hold it constant for 2 to 4 hours.

If your Jeep has a low output charging system it will never get there - it will be about 2 volts short. Also, the 2 to 4 hour timing at that voltage - your alternator can't do that either. You need a multi-stage smart charger to do it properly. (DC-DC for your vehicle or mains powered for maintenance)

3) Float charge at 13.0 to 13.1 volts. Your alternator might do that when it's hot.

4) Avoid charging at battery temperatures above 45 deg C.

Typical engine bay temperatures are well above that, and your alternator will keep charging regardless. My Prado aux battery (Allrounder) gets to over 60 deg on a trip on a hot day. (My charger shuts off at 50 deg - a bit high for the Allrounder, but at least it shuts off - but continues to record peak battery temperature so I know the battery temp for a fact.)

For your information, mate.

Options?

Leave the engine bay standard and put a battery down the back with a dc-dc charger for it.

Can be a conventional lead-acid type (properly tied down, of course) but doesn't have to be. Have you thought about Lithium Iron Phosphate - a third the weight, smaller physical size and twice the useable amp-hours. These batteries are now going into Bushtrackers and Kimberley Kampers, Karavans and Kruisers with fabulous results. None of this lead-acid multi-stage charging stuff - just a simple dc-dc charger that fills it flat out until it's full, then goes to float. Only drawback is cost, but you'll get 3000 to 7000 cycles from it, provided you don't abuse it, which offsets the cost compared to a number of lead-acid replacements for the same number of cycles. All depends on use/abuse, of course.

Cheers

Firtsly don't get obsessed with this whole "calcium battery" thing, if it is a sealed battery appart from a cylindrical cell battery like an optima..it will have calcium in the plates.

If the standard battery is a sealed battery, it will have calcium in the plates.

Secondly, don't get obsessed with this smart alternator thing without knowing how that particular alternator behaves.....not all smart alternators are a bad thing.

third..no matter what type of battery you select.....you will not increase the capacity in the same space unless you do to some exotic technology like lithium.
The changing from the factory battery may not give you any real advantage...in fact you may well reduce capacity.

Remember the if you run the fridge too long, with a single battery you may well not be able to start the car.

cheers

Mudguard,

When you work out how you are going to charge your Aux battery in the car then do not connect your trailers charge wires (for the REDARC BCDC1240) to the Aux but to your start batt in the car.
It stops any smart chargers getting confused when the vans batteries are connected about what it is they see in terms of voltage.
As you will only draw power from the start battery when the engine is running and you have your trailer connected it is not a problem provided you disconnect your anderson plug when the engine is not running.

This leaves what ever set up you have in the car seperated from the van circuit