How long will my battery last if...

[Keithy P38]

Hey everyone!

I've got myself a 105a/h battery which is sitting in an ark power pack at present. As you may/may not know you cannot charge the battery when it's in the vehicle due to it being primarily a 240v charger in the power pack.

I was running a few scenarios for my up and coming 5 day trip (moving every day with a minimum of 5hrs behind the wheel). I need to run my ARB 80 litre fridge, previously only ran it off my Rangie and turned it off at night.

1. Starter battery is exactly the same battery (dual purpose), so after 2 or so days, swap the two and charge the auxiliary as the new primary battery.

2. Run the fridge off the car during the day at lower temp and then use aux battery at night on slightly higher temp.

3. Take an esky.

4. Run the fridge off the power pack only and see how long it'll last before the fridge stops cooling at its "battery protection" voltage.

I'm not close to home for a few days so unsure on fridge specs. It will be pre-filled and pre-chilled before the trip.

Any advice welcomed. And if anyone has any tips or tricks on how to allow the power pack to be charged from my Rangie, much appreciated!

Cheers
Keithy

[Blknight.aus]

make a 12v charger for the pack that runs off of the aux circuit in the car.

I do a fairly primative version of it.

105AH driving an engel if used smartly will get you about 3 days worth of fridge working coldness.

[Keithy P38]

How would you suggest that I make a 12v charger for it? I'm great at running wires, soldering them together and mounting things but I'm very unfamiliar with dual battery setups and for most of what I do (2 night trips) my power pack lasts no worries.

Would it be worthwhile running a permanent feed from the crank battery to some kind of switch or relay then to a set of leads that I can attach/remove when needed?

Cheers

[THE BOOGER]

can it be charged through the cig lighter socket ? Or a small inverter to charge it while driving

[Blknight.aus]

it can, I make up primitive charging systems using lights and self resetting circuit breakers (and you dont have to have the circuit breaker if your doing a long enough run)

basically

from +ve in the ciggy socket run 2 connections one goes direct to the fridge outlet the next goes to a 5a circuit breaker with about a 20W 12v bulb wired across it and then to the aux battery.

Amp Regulator.jpg

heres the things you need to watch.

Watts = V*A

measure up the voltage of the system with the ignition on and the engine not running, give it a minute or 2 so that all the systems that only run for an initial 30 seconds or so turn off and the voltage normalises. Measure the voltage again with the engine running and the main battery fully charged (maximum system voltage is what you're after here. Use those 2 voltages to work out the maximum wattage draw of everything involved (the Circuit breaker the 12v bulb and your load) do the same thing for the Amps draw of the components.


the total number of watts should not exceed whats written on the socket (for those of you with those 120w style outlets in the back)

The total number of amps should not exceed the size of the fuse protecting the AUX outlet you are plugging into.

The size of the circuit breaker needs to be suitably rated for the load.

the 20A fuse is to protect the wiring from the aux battery to the plug for the AUX socket if your aux battery box/battery tank has a circuit breaker or fuse in it this can be omitted.

If you're using SLAB/Gel batteries you cant just run these directly off of an alternator without risking stuffing them up. If you're going to use this primitive charge regulator you need to set the size of the bulb and the circuit breaker so that they have a lower rating than the charge rating of the battery.

IF you need to drive something with a big amp draw (like an inverter or incandescent flood light) you need to drive it directly from the power outlet of the second battery (dont forget the fusing if its going to run from long cables) and unplug whole thing from the aux outlet.

This system will backfeed the aux socket, in some vehicles this will keep all the aux systems alive and drain all of your batteries.

The plug that goes into the Aux socket will be live at all times. you may want to provide a cover for it or fit a suitably rated switch or change the plug to one that has protected pins.

The voltage is not stable if the circuit breaker is cycling.

heres how it works

• When its all plugged in and the battery is charged (+90%ish)

the aux outlet runs the load, the circuit breaker keeps the aux battery topped up and everythings happy.

• When its all plugged in and the battery is flat (<90%ish)

the aux battery will try to draw all the amps it can. When this exceeds the amps of the circuit breaker the circuit breaker opens and the light allows some current to flow keeping the battery charging (albiet very slowly) while the circuit breaker is open the aux outlet is still running the load The circuit breaker will cycle on and off untill the batteries charge is such that the current draw drops below the rating of the circuit breaker

• When its not plugged in

the aux battery provides the power through the circuit breaker. if this trips the light will come on.

[Keithy P38]

Wow that's one hell of a description! I understand the logic behind it and how it works, it's also one of those jobs that I think would be better left to someone with more expertise than I!

Thanks heaps for that, must have taken a while to type up!

EDIT: just looked at the wiring diagram! Easy done!

[woody]

Is it the Ark Power Pack or the newer Arkpak?

It doesn't really matter as both can be charged by the car,

• for the Power pack connect to the terminals on the top and it will bypass the integrated smart charger. http://arklive.customercommunity.com...ack_manual.pdf
• with the Arkpak connect via the anderson plug to bypass the smart charger. http://www.arkcorp.com.au/images/a3_arkpak.pdf

I have the power pack set up as a third battery in the camper trailer fed via the Traxide SC80 and maintained by 20 watt solar panel.


woody

[Blknight.aus]

if youre pack has a proper charger built into it you're much better off using a traxride item to charge it.

That charge limiter is a workaround patch up that can be made pretty much anywhere and charge anything for when you wind up supporting something you werent expecting to.

[Keithy P38]

Yeah it's the older power pack. Was planning on going straight off the terminals - the charger won't charge if you are pulling a load off it as its only a small charger that's designed to charge in the isolated position.

I have been looking around at the various chargers on the market, the Baintech stands out to be pretty good value for money, simple and I could install it easily in a few hours. That would make my power pack more of a battery box than anything else!

I've got a few weeks til my little trip so plenty of time to prepare!

Cheers
Keithy

[woody]

Do you have, or have you considered the possibility of installing a dual battery controller?

The Traxide SC80 is relatively inexpensive and very easy to install and this will take away the problem of not having enough 12v power in the car.

woody