How do you test a battery?

[arbarnhart]

OK, it's the cheap guy. Not the only cheap guy, but the one who regularly admits it...

Anyway, I am selling my little Cruise-N-Carry to go electric and screening buyers because believe it or not I don't like to piss people off and that motor is capable of doing that if they don't understand it is a weed whacker with a prop on it. Well, one guy has a Fatty Knees and wants something like this for when the wind dies and he wants to go home. He knows about these motors; in fact, he knows enough to low ball me. But, in e-chatting back and forth, it turns out he has a marine battery from a power boat he had that he has been keeping charged (he knew letting it go dead would be the end of it) in case he needed it again and he is kinda tired of that. So it appears we may work a deal - I will take his low ball offer for the motor plus his battery if we are both happy. His part is easy - he comes over and yanks the cord a few times and the motor fires up (or there will be a thread of lament tomorrow) and he runs it for a couple of minutes and decides whether or not it is too obnoxious. But what do I do with the battery? I have a little trolling motor. I have a meter that I can sorta use (give instructions as if you don't believe that). I know that a used battery won't last near as long as a new one. Duh! But it will allow me to wire things and figure a lot out. I would like it to last his season and maybe next. Any way to know?

[PBzeer]

If the voltage is lower than 12.25, it's over 50% gone. (As I understand it)

[eMKay]

12.8 100%, 12.6 75%, 12.4 50%, 12.2 25%, 12.0 about discharged, anything less than 12 is dead. If he just took the charger off you will not get an accurate reading as it will have a surface charge, a good way to get rid of that is start your car with it, shut it off, turn the lights on for about 20 seconds. Don't worry about killing a deep cycle battery by using it to start a car, a starter in good condition on a warm day only draws around 120 amps. Is your troller electric? You could hook that up and run it for a few minutes (in water, like a 2-stroke the water cools the motor)

[Stillraining]

Voltage alone wont do it.....Carbon pile load tester....or a cheaper version sold at Auto part or tool houses..

Heres the cheap one...

[eMKay]

Originally Posted by Stillraining

Carbon pile load tester....or a cheaper version sold at Auto part or tool houses..

I was going to suggest that, but seemed overkill for a next to free battery.

[capngregg]

Most auto parts stores will do the load test for free. Auto Zone has stores just about everywhere and they all have the tester. Same with Sears and some of the other department type stores.

[Stillraining]

Originally Posted by eMKay

I was going to suggest that, but seemed overkill for a next to free battery.

Ya...But the cheap ones work fairly well actually so for less then 40 bucks you have a tool every one will want to rent for a dollar...

[hellosailor]

Yeah, you need to LOAD TEST the battery. If you ask at Autozone and some of the other chains, they will lend you a surprising number of tools. You pay up front for the tool, you bring it back within xx days and they give you a full refund.

Without a load test, there's no fast way to tell how good the battery really is. Or, the two of you could take the battery into a shop and have them load test it. Make the deal up front: If the battery passes the load test, fine. If not, you get $$ instead and the deal still goes through.

[arbarnhart]

OK, here is what I plan to do. I have both motors (the little stinker and my eletric troller) on brackets with the electric's prop in a bucket or water (the stinker is air cooled; I did not realize that electrics required the water). As soon as he gets here, I will hook up the electric and turn it on and just leave iton while we chat about boats and motors and start the other one and he looks it over. Then I will check the voltage on the battery.