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Longevity of storage battery

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kwame

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Hi folks
i have just bought this 600 watt chinese made inverter from the store.Unfortunately,storage batteries a hard to find and very expensive.I have a fairly new truck battery with ff spec. 12v 140AH (20) which i intend using with the inverter.
My question is,how long will this battery last when i use it to power a small wall fan that is 40W @ 240 vac.
THanks
Big UPS!
Kwame
 
A vehicle battery is designed to supply hundreds of AMPs for a few seconds to start an engine then immediately be recharged.
Your use will quickly kill a vehicle battery.

You need a circuit to sense the voltage then disconnect the load before the discharge is too deep.
Or you can buy a more expensive "deep discharge" battery designed for use in motor homes.

Why are you using a 240VAC fan instead of a 12VDC fan? The inverter uses a fair amount of current so it might draw 140W from the battery to run the 40W fan. A HUGE waste of energy.
 
Lead Acid Starting batteries are not designed for discharge to less than 90% of capacity. If you discharge a starting battery more than that, you greatly shorten its life. Get a "deep cycle" battery.
 
audioguru greetings
So you reckon this ordinary battery will last how many hours?
Kwame
Ghana-Africa
 
audioguru greetings
So you reckon this ordinary battery will last how many hours?
Kwame
Ghana-Africa
I don't know the efficiency of the inverter. It might use 140W to power the 40W fan.
140W/12V= 11.7A
140Ah/11.7A= 12 hours.
The battery will be able to provide 12 hours of fan power for a few times then it will be garbage and you will need a replacement battery.
 
I have acquired a few cheap Chinese made inverters over the years and the ones I had ran with what I would consider normal SMPS based efficiency of around 70 - 80% depending on load.

Given that I would expect it would be drawing around 50 watts off the battery so that would give you roughly a ~34 hours run time based on the 140 AH 20 hour discharge time rating.

Also being that it has a AH rating and time reference I would suspect it's a dual use type battery not just a starting battery. A combination deep cycle/starting battery so running it down slowly will not do much damage to it if it is getting recharged in a reasonable time.

Still that said I would try and keep the fan run times less than 25 hours before recharging the battery when at all possible.
 
Hello there,


I have to agree with audioguru in that a 12vdc fan would be a much better choice. Those inverters are not very efficient so you'll loose run time just because of that alone.

If you can run for 10 hours with a 12vdc fan of a given efficiency, with a 70 percent efficient inverter you can only run for 7 hours with a fan of equal efficiency.
If you need more flow than a single fan you may use more than one 12vdc fan to get more air flow like that as a 120vac or 220vac fan might give you, as long as the total power is the same.
 
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