Power - 12volt to 240 volt via Inverter

Submitted: Thursday, Apr 22, 2004 at 10:54
ThreadID: 12286 Views:2927 Replies:6 FollowUps:9
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Hello All, As per post 12187..... I am trying to work out if it is better (more efficent) to run an inverter in the back of the vehicle which charges a battery in the camper via a battery charger which obviously while driving does not present a problem but and sounds like a pretty good idea.
However whilst camped, and running a 75 watt solar panel to charge the second battery is it better to just run the accessories (fridge, lights etc) straight from the vehicle or keep the inverter running and run the accessories off the battery in the camper. My simple mind says it is line ball as whilst parked/camped run straight from vehicle as the solar panel will be putting in an average 20 amps per day and the accessories around 30amps. The same thing will apply if the camper battery is used as although the charger is putting in 8amps it is only doing this whilst the battery requires it. Where I am not sure is the conversion from the 12 volt to the 240 volt via the inverter is this using more amps per hour than the charger which is being run fromn the inverter is putting to the camper battery.
Does this make sense?

Technical feedback much appreciated...


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Reply By: Rosscoe - Thursday, Apr 22, 2004 at 12:01

Thursday, Apr 22, 2004 at 12:01
My simple approach is that the more devices in the line the more losses. The inverter has losses so to does battery charger.
Also I assume you will have the charger in the vehicle as well as the inverter. I wouldn't be keen on 240V AC between moving car and trailer.
If you have a reasonable solar controller it is the best way to fully charge your battery. If sized correctly you can put more in in a day than you take out.
For charging while driving I am looking at the ARRID twin Charge unit supplied by the 12 Volt shop in Sydney. Cost about $300.00 though.

This device can take as low as about 8Volts and is smart enough to do multi stage charging. Also uses pulse technology to help prevent sulphation.

Have yet to make up my mind on which way to go. Just Solar. Just the Arrid unit or both. $$$$$$$$
AnswerID: 55483

Follow Up By: Member - Eskimo - Thursday, Apr 22, 2004 at 14:15

Thursday, Apr 22, 2004 at 14:15
yep you dead right Rosscoe
more electrical stuff leads to more losses not to mention losses from all the extra electrical connections as well.

Ant thing that consumes power to operate is an additional load
FollowupID: 317344

Reply By: bob - Thursday, Apr 22, 2004 at 13:29

Thursday, Apr 22, 2004 at 13:29
Is it legal to run 240v AC from your vehicle to the trailer while mobile? What about unintentional cutting of active wire eg accident etc? Does your rescuer (or you) get electrocuted? I'm sure there would be an appropriate Aus Standard which deals with this.
I'm not an electrician but this just doesn't seem safe to me.
AnswerID: 55493

Reply By: bob - Thursday, Apr 22, 2004 at 13:37

Thursday, Apr 22, 2004 at 13:37
Australian Standard 3000? SAA wiring rules. Hope this helps.
AnswerID: 55495

Reply By: Boeing - Thursday, Apr 22, 2004 at 13:52

Thursday, Apr 22, 2004 at 13:52
Thanks for the replys. The word that I have found out is it is illegal to have the the 240volt line between the vehicle and trailer ... which you can understand for various reasons. Now working on the simple process of having a line from the vehicle second battery (good thickness) to an Anderson plug at the rear which can then be attached to the camper trailer battery by the same method good fuses either end.

Thanks again


AnswerID: 55503

Follow Up By: Rosscoe - Thursday, Apr 22, 2004 at 17:00

Thursday, Apr 22, 2004 at 17:00

I suggest MINIMUM wire size of 6mm square. Be careful here if you use 6mm auto cable that's only about 4.9mm square, OK but not good enough in my opinion.
Better still, you can consider 8 AWG (about 10 mm square) audio power supply cable which you can buy from Jaycar or Dick Smiths. Seems relative if you are going to the trouble and expense of an Anderson plug which are about $15 each.
You should install a circuit breaker close to the vehicle second battery and a fuse in the trailer close to the fridge.

Also, most people recommend you run an earth cable (same gauge has the positve) all the way back to the vehicle engine rather than the negative post of the battery or just to the vehicle body.

Good luck with your mods.
FollowupID: 317376

Reply By: Member -Bob & Lex (Sydney) - Thursday, Apr 22, 2004 at 17:07

Thursday, Apr 22, 2004 at 17:07
Put the battery charger in the camper connected to camper battery, cable to anderson plug connection on tow bar to isolator in engine bay to main battery & bobs your uncle.
AnswerID: 55526

Follow Up By: Boeing - Thursday, Apr 22, 2004 at 17:34

Thursday, Apr 22, 2004 at 17:34
Bob, What runs the Battery Charger in the camper??


FollowupID: 317391

Follow Up By: Lynn2 - Thursday, Apr 22, 2004 at 18:56

Thursday, Apr 22, 2004 at 18:56
You can buy an ARRID Twin charger from the 12 Volt shop and install that in the trailer. Accepts voltages as low as 8 volts DC and is a smart multi-stage charger that also uses pulse technology to mimnimise sulphation. Ensures 100% battery charge. Cost about $300.00 though.
Eliminates the worry of voltage losses in the vehicles wiring system but does consume power.
IMO still better to use heavy wiring as well as this device.
FollowupID: 317411

Follow Up By: Member - Nigel (QLD) - Thursday, Apr 22, 2004 at 19:25

Thursday, Apr 22, 2004 at 19:25
$300 for the Arrid Twin Charge sounds reasonable comparted to a decent inverter and battery charger

a 20 amp multistage charger will cost around $300 for a budget model
FollowupID: 317417

Follow Up By: oldbuddy - Thursday, Apr 22, 2004 at 22:13

Thursday, Apr 22, 2004 at 22:13
Hi guys,

The ARRID Twin Charge is a good unit but the guys at ARRID assure me that it IS NOT a multi-stage smart charger. It puts out a constant voltage of around the 14.0+ volts. It is suitable for all types of batteries. It will not over charge due to the rising battey potential as charge is added. It can be slow to feed in the last 20-30% of charge due to this feature.

Regardless of this, it is still probably the best thing around. Also look at the Engel Battery Boost Charger ($134 at Campmart in BN) which does the same thing but is current limited to 10Amps and is really small. It also has another input which can turn it off unless the ignition is on.

Good luck - would like to hear more of other peoples experiences with these units.
FollowupID: 317448

Follow Up By: Rosscoe - Friday, Apr 23, 2004 at 10:53

Friday, Apr 23, 2004 at 10:53
Hi Nigel,

Seems you're right re the multi-stage bit.

Are the claims that the ARRID unit is "The Only Dual Battery Controller to Fully charge your batteries" correct?

I only have a 75AH deep cycle battery in the caravan and would like it to be 100% charged when I stop to camp. Not the 70 or 80% that is achieved by normal vehicle electrical system.

I now have prices from $78.00 supplied and fitted to the $300 Arrid unit???
FollowupID: 317491

Follow Up By: Rosscoe - Friday, Apr 23, 2004 at 11:01

Friday, Apr 23, 2004 at 11:01
Sorry oldbuddy it was you who pointed out that the ARRID is not a multi-stage charger.

If the ARRID only puts out a constant 14 volts how can it achieve 100% battery charge? At 14 volts the battery resistance is such that little current flows into the battery. My understanding is that it this level of voltage will only achieve 70 t0 80 %.
What else is in tha ARRID that allows them to make the claim of fully charging batteries?
FollowupID: 317494

Follow Up By: Member -Bob & Lex (Sydney) - Friday, Apr 23, 2004 at 19:57

Friday, Apr 23, 2004 at 19:57
You run a cable from charger to an Anderson plug on draw bar that then plugs to Anderson plug on tow bar ( seperate line to lights )
FollowupID: 317547

Reply By: Member - Nigel (QLD) - Thursday, Apr 22, 2004 at 22:27

Thursday, Apr 22, 2004 at 22:27
Each device (inverter, charger, etc) will have an efficiency rating (usually somewhere between 80% - 95%).

What that means is that only 80% - 95% of the input wattage makes it to the output, the rest is consumed by the device or wasted as heat.

Cable also losses power as heat, especially when the cable size is too small for the length of the run and the current it needs to carry.
AnswerID: 55601

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