Inverter/battery problems

delapan · Senior Member

Inverter/battery problems

bill12 · Guru

135 w at 12v is 11 amps, and a lot of draw on any battery. That way your 110 amp hr battery would be 50% flat in 4 or 5 hours, if it was fully charged to start.The 3 way frdges draw big amps on 12v, and run better on gas. The compressor types, like my 55 ltr waeco average about 2.5 amps per hr, and get colder also. Mine will go to -18c, if I want to. 1.5 amps is probably what it draws on 240v.I hope this helps you, Bill

ParamountCruiser · Senior Member

I believe that if powering your fridge by this method the inverter should be wired via an anderson plug to the tow vehicle, not to the van battery.

delapan · Senior Member

hi there, thank you for the replies, that solves my problem or at least answers my question, many thanks, gary

liddle · Senior Member

hi bill

could you tell me the model number of your waeco please

Liddle

bill12 · Guru

Cdf 55 . I bought it at supercheap on sale a few years ago. Works well when on the road . I have a dual battery system , one 120 amp hr in the car, and a 150 amp hr in the van. Lasts about 5 days before I have to hook up to the car or start the genny. I also have 2 -60 watt panels that put in about 6 amps per hr. Seems to work. Freezes my fish, and my beer if I don,t watch out. Bill

jimricho · Guru

Assuming this is a Dometic 3way fridge, running it from your house battery either directly on 12v or via an inverter is a lost cause due to the current drawn, which, as Bill points out, is 11 amps (I don't know where you got the 1.5amps from?)

Normally 3way fridges are only used on 12v while on the move, the 12v being supplied by the main (starting) battery of the tow vehicle and there should be no interconnection with the house battery.

It is recommended that there be a relay (or solenoid switch) installed in the circuit from the tug to the van so that it disconnects the fridge and doesn't flatten the tug's battery when the engine is not running. An alternative to the relay is a "Fridge Switch" that can be DIY installed in the van. This will automatically disconnect the fridge from the 12v when the rig is stationary. (click on the underlined link for more details).

When on a powered site obviously you can use it on 240v or if camping away from power use it on gas.

Be aware that regularly flattening any battery (deep cycle included) will seriously reduce its lifespan.

Mccanic · Veteran Member

Inverters suck for powering fridges as the higher the current draw the higher the losses are through the inverter.

All inverters have a % of power usage to convert to the desired voltage which is lost in heat and resistance, this adds to the current draw that the fridge is pulling.

A good quality battery (e.g. Optimer or Delcor) will give you better life and faster recovery charging but you will never get a full charge on any deep cycle battery off an Alternator feed, gen set or standard charger.

To get the best out of a deep cycle battery it needs to be pulse charged which means it gives a series of high voltage charges over set intervals so not to damage the battery but removes any "memory" the battery might have.

It will also give you 10 to 25% more charge in the battery holding charge at probably around 13 to 14 volts rather than 12 to 13 volts.

Very technical I know and is hard to explain why without getting into the chemistry and physics of it all.

My suggestion would be to fit either a relay based power feed (with a manually operated switch to turn it off when not in use) to the Auxiliary pin on the trailer plug to charge your in house battery or, fit a proper duel battery system (e.g. Piranha) and Anderson plugs with a minimum of 6mm Positive and Negative feed drawing from a 25a fuse at the battery main.

Hope that helps,

Cheers Damien