Charging battery in car?

Hey Kroozer,
May be one of those Jumper battery packs will do the job, They can be charged from 240v or 12v cig lighter, Just get the biggest amp rating you can afford .
Cheers Dave....

If he already has the battery how does he charge it now ? He can recharge it in the motel using his batt charger on 240v ,,, another is to buy a 12v to 240v inverter , plug inverter into car - batt charger into inverter ect , not very effiecient but would suffice short term use.

Hi there. Setting aside the charging question, let's look at the load overnight: If the Waeco draws say 0.8amps, and the fridge is run from say 6:00 pm until 7:30am, that 13.5 hours at 0.8 = 10.8 amp hours. Most people on this site seems to support the idea that you cant safely draw more than about 60% of the nominal capacity of a lead acid battery without damaging the battery. That's 60% of 18, or 14.4 amp hours. This would not leave much of a margin.
If it was me, I think I would run the Waeco flat out during the day, while the car engine is running, (either to make ice and keep the food in an esky, cooled with the ice, or else run the Waeco close to freezing, so that it has a 'head start' to carry it through the night). Then, I'd leave the fridge off until around bedtime, and then run the Waeco on a moderate (fairly warm) setting until first thing off the small battery. This would reduce the load to, say, 8 hours at 0.8 amp load, or 6 amp hours.
As for recharging, I suspect that most of the technical power pack options will be far too expensive. If he already has a simple 4 amp charger in the shed, then an small (150W continuous)inverter, attached to the charger, might be a goer.
Hope this helps.
Chris (SA)

Hi Kroozer

1) Yes there is a device to do this called a car to car charger.

2) Draw would depend on setting and ambient temperature.

3) 18 a/h battery would be just about be dead after 10-12 hours (Again depending on the variables and if the battery was full to start with and the fridge was already cold)







Regards

Derek

I've used the 7Ah gel batteries for camping and to keep them charged, have simply used a relay that is energised by IGN power. So its charging off the alternator when you run the vehicle, and is isolated as soon as you turn off.

We run a Waeco CF40 in the back of our car. We have 2 batteries that we can use. We have a Waeco 36 amp/hour battery thar charges as we drive along and also runs the fridge. Depnding on the external temps, we can get up to 3 days use out of this battery in summer.

As a backup we also have an 18 amp/hour jump start battery that we can also use to power the fridge. This easily runs the fridge overnight.

I have no idea about chargers though.

Those 18A/h jumper packs (I have one) can be recharged through the cig lighter. It's a very crued way of doing it since you can only charge for a certain number of hours before you kill the SLA battery due to overcharging. If you keep on eye on the time then it's OK. Mine came with the cig lighter charging cable.

Those SLA batteries are also considered deep cycle so can be discharged to down near 20% SOC. However just because you can doesn't mean you should.

Thanks everyone for your advice. I think i will recommend friend to get either an inverter or one of Dereks car to car chargers. I think thats what he really wants and as its made by Derek i dare say its gotta be good. All he really wants is a cheap way to charge the battery during the day while travelling, kind of a lazy approach really. Not sure how he thinks sometimes.

Thanks again

I'm with Chris in an earlier reply in that you run the fridge on a colder setting while driving (sounds like there will be at least 5-6 hours of driving a day on this trip) and then run it on a less aggressive setting overnight.

I have a CF40 and did this while touring around in a Honda Civic before getting delivery of my Prado (with dual battery setup).

When I bought the fridge I also bought a Weaco branded powerpack (made by the blue-apple people who are now Home of 12 volt at Mt Barker SA) that is a 24AH SLA battery with two outlets and a test light on it. They are still available for about 300 to 400 bucks which is well overpriced for the capacity but you pay for the convenient packaging. these things come with a lead for plugging into the cigar lighter to recharge them while driving.

Even without the pack I would run the fridge in the boot of the Civic (I did pay TJM $100 to wire a socket in the boot for the purpose) on a setting of 4 or 5 lights and then I backed it off to 3 lights overnight. Even with the tiny battery in the Civic it was never an issue.

A 17AH Supercheap jump pack chucked it the boot would also be good insurance for a morning jump start if the car battery got a bit sluggish. You can get these for well under 100 bucks and they are a great backup as well as being a mobile power source around camp (Lights, air bed pumps etc).

The Weaco fridges also have a low battery cutout built in if it is a fairly recent model. Set this to the high (conservative) setting and it will automatically shut the fridge down before the car battery is drained.

Remember also that the 0.8Amp consumption figure quoted is an average, possibly over a 24 hour cycle. My experience with the CF40 is that it draws 4 to 5 amps when the compressor is running but it only runs about 20-30% of the time giving you the 0.8 to 1.0 Amp average usage figure. This would be at an average temp of around 25 degrees.

When it is hotter (try 50 degrees in the back of the wagon in full sun on a 35 degree day) then the fridge is going to be running the compressor virtually flat chat and it will be chugging down 4-5 amps every hour but overnight when it is 10 to 15 degrees or even colder on desert trips then it will hardly run at all so the fridge may only use 3-4 amp hours over the whole night.

As pointed out, some people even turn them off overnight and only run them when driving.

Hope the info assists.

Muddy