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Battery Charging from ZD30 90 amp alternator to caravan.
I have ordered a new Jayco van which will be fitted with a anderson plug and wired directly to the fridge. The fridge itself is a 3 way 12volt, 240 volt and LPG. This fridge requires 275 watts or 23 amps to run it on 12 volt that is why Jayco fit the anderson plug and wire it straight to the fridge and terminates there. The van is fitted with a 100amp hour battery and charged by Jayco's own 240 volt-12 volt system which I beleive is not a 3 or 5 stage charger but only a trickle charger. My previous Jayco van had a compressor fridge fitted which only required a maxium of about 7 amps to run. I charged the batteries in my previous van by installing heavy cable to the rear of the Nissan through an anderson plug and then directly to a device that allowed for voltage drop (12 volt shop) and then to the battery. This worked fine.
My question is- Will the standard nissan 90 amp alternator be sufficient to run the 3 way fridge (23 amps) and charge the battery in the van as well via the Red Arc Battery Management System that is capable of charging from the battery 12 volt-240 volt and solar imput. The maxium charing output on Red Arc System is 15 amps. (23 + 15= 38 amps) maxium draw with the battery in van flat and fridge running.
Thanks David
 

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That set-up should work fine.

The standard Redarc is rated to 100 Amp continuous and there is a 200 Amp model if you want it but they are a bit exxy.

23 amps is a fairly high load for a fridge but that will only be while its running and the Alternator might be a tad unhappy if you are pulling that juice plus driving at night with several Spotties ablaze, A/C fan on full blast, etc etc so maybe keep a bit of en eye on what you do have running. During the day it should be no hassle at all.

An Ammeter in the feed to the rear might be handy if you can find one with a suitable shunt. That will let you keep an eye on how much load the Van is pulling if indeed the Battery is down and the Fridge running at the same time.
 

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Vendor
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Hi Dave and these 3 way fridges are proving to be an absolute nightmare.

As Evil put, while day time driving, your alternator will have no problems meeting the amps and your battery, if in a low state cane easily draw 25 amps or more.

The problem is not just with Jayco, it is a problem for and camper trailer or caravan fitted with one of these fridges and note thats 23 amps at 12v. Your alternator runs at anything from 13.5v up.

The problem is that while your alternator can meet the amps required, no matter how thick your cable is, because of the almost constant current draw of the fridge, the voltage drop caused by the fridges current draw will mean you will never charge your house battery.

Now to make things even worse, if your like most RVers, after a few trips you will find your need more stored battery capacity and you will want to add another battery.

Your battery charging problem just became critical.

There are a number of options but the one in the diagram gives the best results.


 

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Hiya Drivesafe,

Great post and those Traxide schematics are the ducks guts :cool:

I must admit I didn't think about his house Battery charging because I interpreted his post to mean he is running a DC/DC converter in his Vehicle feed at the Van end.

Coupla questions about that schematic to salve my curiousity...
Why the 30 amp Fuse in the vehicle connection and the 10 amp fuse in the house battery connection?
Are these fridges in question only running on 12 Volts when connected to the vehicle ?
If so whats the 10 Amp house feed for... Fridge Light, LPG Igniter, all the above?
 

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The Bear
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First thing, chuck the stupid 3 way fridge and put in a small proper 240V compressor domestic fridge or similar and run it off an inverter. Thats whay I did, i bought a full size Aldi 2 door domestic fridge and chucked the 3 way out, what i got for it paid for the Aldi 210 liter jobbie with a proper freezer, Missus thinks she's in heaven when we go away. I run it off an inverter and 2 x 205 ah AGM batteries in the van charged directly from the alternator via a VSR off the main battery and anderson plugs between the patrol and the van, done 00's of hours, and never missed a beat. Always got Ice cream and Ice cubes.....Batteries always full after a normal days drive, runs for a couple of days no issues, then out with the honda and Ctek for an hour or so as required.
 

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I have an 06 expanda with the 3way fridge, I have set up a trickle charger for when hooked up at powered site or home as I found the standard Jayco built in unit didn't do the job sufficently.
I have a 120 upgraded alternator on th gq and can run on the 12 volt system whilst travelling with no dramas. I do however always use the LPG side of thing whenever camping and 240v is not available as it drains the batterys, 120 amp hr, way to fast.
Gazza!
 

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BORDERTREK 4X4 & FABRICATION
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Are these fridges in question only running on 12 Volts when connected to the vehicle ?
Most modern vans have a controller that automatically switches the fridge to 12V when 240V is disconnected and back to 240V when 240V power is applied.
 

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If you had a average current draw of 40A and a total circuit length of 16m (8+8) and used 10mm2 copper. You would have a 1.1 volt drop that is nearly 10% which is on the high side. But I think you would find that when the battery in the van charged up to about 11v it would reduce the volt drop by helping the main battery run the fridge and charging when the fridge was cycling.

The formula for the volt drop is.

(1.72x10E-8x16)/(10x10E-6) = 0.02752 ohms. Then use Ohms law 0.02752x40= 1.1volts
 

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Most modern vans have a controller that automatically switches the fridge to 12V when 240V is disconnected and back to 240V when 240V power is applied.
Yeah thats what I thought... but that schematic only has a 10 amp fuse in the 12 Volt supply from the House battery so it won't hack the current... if the Fridge cuts in then "Ferzaaat" goes the fuse.
 

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The schematic looks like it is designed to run the fridge off 12 volt when the ignition is on and gas when it is off. Hence only a 10A fuse to run the lights and stuff in the fridge.
 

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If you had a average current draw of 40A and a total circuit length of 16m (8+8) and used 10mm2 copper. You would have a 1.1 volt drop that is nearly 10% which is on the high side. But I think you would find that when the battery in the van charged up to about 11v it would reduce the volt drop by helping the main battery run the fridge and charging when the fridge was cycling.

The formula for the volt drop is.

(1.72x10E-8x16)/(10x10E-6) = 0.02752 ohms. Then use Ohms law 0.02752x40= 1.1volts
I'd go 16mm.sq in the above case. 0.34 volt drop then. Just below the 3% volt drop threshold for 12V. 10% is way too high for 12V. Even 240V has a 5% threshold.
 

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12vdc - 240vac 0 gas fridge in caravan

Had issues with our fridge in the caravan with respect to travel, 12vdc selected. Best you could call it was a cooler. Purchased a good 12vdc to 240vac 600 watt inverter which we fitted, and the fridge now runs 240vac for travel, 240vac in parks and gas on the bush camps.
As an added nicety - Phone is always charged and we never miss the State of Origin.

Have been using this arrangement for the last 40,000 k's or more ......

My 2 bobs worth
 

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Yep, a fridge will always run more efficiently on 240v. As long as your charging system keeps up the power to the inverter it's all good.
Personally I would run an inverter for a fridge when the engine's not running though. They tend to suck more juice from the battery than running it on 12v straight from the battery.
 
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