Quote:
Originally Posted by pinballlooking
Does anyway know if a car battery will work to run a 8amp 12 Volt dc motor with a small battery charger to top it back off at night.
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First you need to figure out what the maximum time that motor will run. That number in hours x 8amp will give you the amp hours you need from the battery. You don't want to run the battery dead so it needs to be big enough not to drop below 75-80% of charge to be safe on a automotive lead acid battery.
So for example you draw 8amps for a total of 4 hours. That's 32AH So you would need at the very least an 120AH battery. Charging is the reverse so if you have an 8ah charger it will charge in 4 hours.
Car batteries are not really designed for long current draws, they are just designed for a quick surge to start the car.
Deep cycle will fair better with repeated discharges and can be run as low as 20% of charge, so a 50AH deep cycle would work in place of the above car battery and last longer as it's designed for the long, low current draw.
Hope that all makes sense.