can a house battery that shows that it is fully charged be indeed stuffed? reason I ask this is 2-3hours after putting a load on the 12v fridge stops working through exssive draw. I have tried it with 2 different fridges, same story, regards oh wise ones
Well sitting here at my computer keyboard it sounds like it is stuffed.
But the answer will be known if you meter it and see what is happening over those 2-3hrs and then what happens when you charge it up again. Do you have a voltage meter or multi meter to take some voltage readings. Cheap to buy one ! If there is some other problem then you could use it to find a problem also.
can a house battery that shows that it is fully charged be indeed stuffed?
Yes.
A lead acid battery is manufactured with a given capacity. Over time some natural chemical processes occur which cause the capacity of the battery to fall. As the battery approaches the end of its life its capacity may have fallen to, perhaps, only 5% of its original level. Such a battery will still accept a charge and will show a terminal voltage of around 12V6 after charging.
With a quality battery which is well treated the above process may, typically, take five or six years (often more) but if a battery is mistreated its life may be as short two years. Always be nice to your batteries - it will save you a lot of money :)
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Measure your battery terminal voltage after it has been on charge (no load). Then check 15 mins later after it has stabilised.
Put the load on & measure the voltage each 15 mins. Do NOT let it discharge lower than 12.2-12.3v!
If possible put a separate Smart charger on the battery & leave it there for say 6-8 hours. Then repeat "Putting the load on & measuring the voltage each 15 mins. Do not let it discharge lower than 12.2-12.3v".
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Warren
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Charge the battery for 24hrs with a mains charger, is it hot or does it smell like rotten eggs, if yes, disconnect the battery because is in dead stuffed and could do damage including catching fire or exploding spraying acid everywhere. If it's not hot or smelly, attach a 60w light across the battery and time how long it takes for the voltage to drop below 12v. If it's under 2 hrs, you have a door stop, if you get more than 2 hrs, recharge for another 24hrs and repeat the test. If you get more hrs before it drops below 12v you might be able to recue some of the lost capacity, if the result is exactly the same or less, you have a door stop.
T1 Terry
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Nobody has asked you the all important question, "What sort of fridge is it?"
Compressor or absorption?
A 2/3 way absorption fridge can run on 12 volts, but will indeed flatten at battery inside 2 to 3 hours because they draw between 25 to 35 amps depending on the size of the heating element.
A modern 12volt compressor fridge shouldn't draw more than 5 to 6 amps at the most and will usually cycle on and off just like your home fridge.