Battery Advice Needed Please

[alan_fincher]

Talking about fridges, I have a three way one but I turn it off when I go to bed. I normally run travel about six huse. do you think I am taking out more than I am putting in.ours a day and have a 90 amp alternator for domestic

3 way fridges powered off the 12 volts are one of the most disastrous things you can use.

 

Few have a thermostat, and IIRC, even the small ones draw about 8 amps continually, (so maybe 4 times as much as a thermostatically controlled compressor fridge that draws 4 amps, but only 50% of the time).

 

A typical leisure battery can supply 8 amps continually for maybe only 6 or 7 hours before being discharged to the maximum sensible point of 50% charge, so you might need 4 leisure batteries just to run one of these fridges satisfactorily for 24 hours, with no charging.

 

In practice your 90 amp alternator will only deliver very much less in normal charging situations, (depends on engine RPM, pulley ratios, and more). I wouldn't like to predict how long you would need to run the engine to put back just what the fridge would use, but it's going to be a very long while.

[colin loach]

taking that answer on board i will use gas only. many thanks Colin.

[alan_fincher]

taking that answer on board i will use gas only. many thanks Colin.

That's all we ever do - I've never tried 12 volts or 240 volts.

 

I suspect it was the 3-way fridge not run on gas, that had caused the previous owner to buy a generator. (We didn't get the generator, but did get the instruction manual, the rust marks where it had been, and some highly suspect cabling as a result. )

[RobinJ]

taking that answer on board i will use gas only. many thanks Colin.

The old blue split charge relays (30A) used to have an additional contact to drive the fridge, very useful - only takes power off the alternator when the engine is running! Must remmber to light the gas when you stop though!

[smileypete]

Which reminds me.......

 

I've been contracted (yet again) to test (yet) a (nother) battery pulse desulfator.

 

Apparently this one is (yet again) different and this one does indeed (yet again) work unlike the others.

 

It's becoming a reccurring theme this! I do believe there is some merit in the process but so far all the one's I have tested have resulted in inconclusive data.

 

Depends how they're tested I suppose.

 

I'd try desulphating batteries using more conventional methods, then see how much additional improvement the desulphator gives.

 

I desulphate as follows, where C is the battery capacity in Ah:

 

C/25 - C/50 constant current for 1 hour a day.

C/250 - C/500 constant current for the remaining 23 hours.

 

Caveats:

 

Must NOT be used for sealed batteries(!) and usual precautions apply

The battery must not be in use.

The lower charge rates are less likely to work.

It takes time!

 

cheers,

Pete.

Edited April 29, 2009 by smileypete

[Justme]

Just remember that when the engine is actualy running the alt is providing the power not the battery so 6 or 7 of the 24 (or in your case 16 as you turn it of overnight) hours in a day are not coming from the battery at all.

 

 

Justme