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Post Info TOPIC: Time For New Battery?
oiddad


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Hey all. I have a feeling that my 105ah deep cycle aux battery in back of ute linked to redarc BCDC 25amp charger may be "gone"! Multi meter read 12.5v before leaving this morning for a 1hr 15min drive to Adelaide. We only had the 180litre Thetford van fridge connected through heavy cabling and grey anderson plug. Upon arriving the van fridge was still operating on battery but the aux battery was only reading 11.95v (engine not running). I would have thought that the redarc 1225 should have been enough to power fridge and keep the battery topped up? Now I have no way of topping up the battery except driving without fridge connected. Has the battery had it? I did have it under a fairly heavy load at the beginning of this trip. Cheers.

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johnhgh


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It may depend on your fridge, my 180L Dometic AES fridge draws 23 amps on 12 volts. Your 25 amp charger may not be keeping up.



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John
oiddad


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Thank you. I have tried to find how many amps the Thetford is drawing but get various answers. Is there a sure fire way of finding out what amps it is drawing?

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Are We Lost


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There should be a sticker on it with specifications, or look it up online. Johnhgh's comment about 23 amps aligns pretty well with my 25 amps for 186 litres. Your 180 Litre fridge should be pretty much the same.

So the Redarc would only just keep uo with the demand. Maybe the caravan battery was being charged as well? If the auxilliary battery was not fully charged when you set out your reading is quite understandable. With a 25 amp draw it would not take long to drop the voltage. Once the fridge is disconnected the voltage should show higher.

Note that on 12V (in mine at least), the thermostat is not used, so it consumes the full 25 amps continuously.

Once the fridge is cold, you could easily disconnect it without drama so there is enough current to recharge the auxilliary.

Your system should be designed to disconnect the fridge when the vehicle isn't running, or have voltage detection.


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oiddad


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Thank you. Yep the system is designed so that the fridge won't switch to 12v unless car is running and there us a low voltage sensor/cut out. Not sure whether it is charging van battery as well. I don't think so but will try and find out. The curious thing is a mate that I have been travelling with has the same van fridge and 105ah battery with charger and he has had no problems.

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oiddad


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Drawing 18amps. Label on inside of fridge.

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Whenarewethere


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It is almost frightening how much these 3 way fridges draw. Either get rid of it or custom build in a compressor unit so you have in effect 2 fridges in one. Something like this https://www.dcfridge.com.au/collections/diy-kits so you you could build in.

But still just get a comorecomp fridge.

If you are running the fridge from a battery you will also need capacity to recharge the battery as well.

 

Even my tiny 28L fridge at up to a maximum of 15Ah per 24 hours x 6.5 would work out at 98Ah for a 180 litre fridge. A big difference to 432Ah per 24 hours for a gas fridge running off its secondary 12v option.



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PeterD


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There is nothing wrong with absorption fridges (apart from perhaps the paranoia some have towards them.) If they are installed properly they run well and do not need the bandaid fan fix that some use on bad installations.

I admit they do have limitations in the 12 V operation area but if you know what you are doing they can be installed to operate correctly. To do this use cable that is heavier than most auto electricians and van builders use. Connect it directly to the tugs starting battery and use protection circuitry to prevent power draw from the battery when the alternator is not operating. It is more economical to get an absorption fridge operating correctly than to replace it.



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PeterD
Nissan Navara D23 diesel auto, Spaceland pop-top
Retired radio and electronics technician.
NSW Central Coast.

 
KFT


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I think I would be swapping the 25A charger for a 40A so there is enough to run the fridge and charge the battery.

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oiddad


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Cheers but I think I'll try finding a cheaper solution. Rewards aren't that cheap and the 25amp isn't even a tear old.

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Aus-Kiwi


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Run it on LPG .,

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oiddad


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While travelling? ....... I don't think so.

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Aus-Kiwi


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Didnt say while traveling ! How long are traveling ? Your alt should keep it going . Dc2Dc charger is not enough !! Although it should keep batteries a live for a few hours ? Unless load is tripping breakers !!

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oiddad


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Mate the problem I have I think is that the van fridge is wired to cone from the aux battery through the dcdc charger and not from the main battery and through the alternator. I originally had it through the main and alternator with a relay switch but the relay switch was causing problems.

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Aus-Kiwi


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You MAY have cable over distance issues ? With DC you require a larger safety load limit . Not much to play with ! A few volts down and your in trouble !! Increasing load !!

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oiddad


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Yeah thought of that. I measured volts at the aux battery and volts at the anderson plug at the back of the car and hardly any difference if any. I just didn't think that just just maintaining temp of already cold van fridge would use up so much battery. That's what made me think it may be the battery or something more complicated therefore expensive.

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Whenarewethere


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Probably similar to trying to cool your fridge with peltier coolers swallowing electricity.



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Gundog


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KFT wrote:

I think I would be swapping the 25A charger for a 40A so there is enough to run the fridge and charge the battery.

 I would ditch the DC charger altogether, and fit a decent VSR ie Sidewinder and if its a smart alternator get the smart feature turned off.

Tin hat and bulletproof vest is on, why throttle a 70ah or bigger alternator with a 25 or 40A DCDC charger.



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oiddad


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Cheers. What is meant by "why throttle a 70ah or bigger alternator with a 25 or 40A DCDC charger."? Are you saying power for the fridge should be coming from the main battery? If so any particular relay switch would be advised?

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Whenarewethere


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Let's say you have 12m ( both + & - ) to the battery & an additional 4 metres from the battery to the fridge. Charging at 25amps.

6awg = 0.52 voltage loss

4awg = 0.33 voltage loss

2awg = 0.21 voltage loss

The DC-DC charger should be indtinsta close to the caravan battery.

 



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Procrastination, mankind's greatest labour saving device!

50L custom fuel rack 6x20W 100/20mppt 4x26Ah gel 28L super insulated fridge TPMS 3 ARB compressors heatsink fan cooled 4L tank aftercooler Air/water OCD cleaning 4 stage car acoustic insulation.
oiddad


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ATM the dcdc charger is sitting on the aux battery in the back of the Ute.

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oldbloke


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6awg? only an electrician would know what that means

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Sta
Aus-Kiwi


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Are you measuring volts with fridge ON ??

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Dicko1


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Gundog wrote:
KFT wrote:

I think I would be swapping the 25A charger for a 40A so there is enough to run the fridge and charge the battery.

 I would ditch the DC charger altogether, and fit a decent VSR ie Sidewinder and if its a smart alternator get the smart feature turned off.

Tin hat and bulletproof vest is on, why throttle a 70ah or bigger alternator with a 25 or 40A DCDC charger.

 Several reasons Gundog...Google it as the answer has been done to death on many forums.



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oiddad


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Volts are measured at the aux battery while vehicle fridge is off.

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Aus-Kiwi


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Try with fridge ON ? You may find the volts lower ? Those little mice need to run harder in the tread mill !! I would be temp fitting some 6mm Sq wire from front battery so alternator is doing its work !! To test .

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oiddad


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Aus Kiwi. Managed to get multi meter onto the back of the anderson plug while fridge was running. 12.3v, waited till the compressor flicked on and volts went to 12.2v and hovered around there. But .... the 3 way fridge in the van will be pulling more amps compared to the Evercool car fridge so I think I may have a problem?

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mischief


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Why run the fridge in van on 12v while travelling, unless you travel 8hour days. A good 3 way will loose minimal cold in a 4 hour trip.. Disconnected my 12v to fridge years ago. Just keep door shut while on the move. Put snacks drinks in car fridge. Then all DC to van.

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rs wiseman
Aus-Kiwi


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When I had mine . I had bottles of water . They acted like a cold sink
!! The more in the fridge the better it stays cool !

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Dick0


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Well...in the end...is the battery ok or not? confuseconfuseconfuse



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"Home is where the Den is parked, Designer Orchid Special towed by Jeep Grand Cherokee Limited"

"4x250W solar panels, Epever 80A charger and 3x135Ah Voltax Prismatic LiFePO4 Batteries".
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