Is my Lawn Mower Battery Bad?

[Charles Wiggins]

Put the battery in the mower and jump start it with the truck. Should start and run even if battery is bad.

The mower won't start, which is what began this little adventure.

[Duane Meadows]

If you can't jump start it, you have other problems than just a battery!

[Randy Cohen]

what happens when you try to start it? is it completely dead?

[Myk Rian]

Get the mower fixed/running.

[Kev Williams]

A battery showing 11 volts is considered 'dead'. You're not far above that--

A battery that shows consistent immediate drain after charging is, as others have said, is indicative of a bad cell.

That said, the mower won't start, and it 'clicks'. That could be a bad starter, or bad solenoid.

Then there's the other 'won't start', which is, engine will turn over (not seized) but won't start.
Does the motor turn via rope pull, or moving the blade, or is it seized up?
If seized up, a check of something blocking the blade, a mechanic or a new mower is in order
If it DOES turn, will it manually start?
If no start, you may have a gooped up carburetor, or no spark-
--ethanol can cause this stuff to form in the float bowl. Plugs the jet very easily...I've had 3 different mowers in the past few years do this-
carbjelly.jpg
Checking for no spark is no fun, but the easiest way is to remove the spark plug- if it's covered in oil or carbon, get another plug, that might be all you need...
If the plug it looks good, then it probably is-- before putting the plug back in, spray a shot of starting fluid in the cylinder first. If you have spark, it WILL fire, at least briefly..
If no start-- did you recently hit something that stopped the motor suddenly?
If so, a common occurrence is that inertia of the flywheel in motion causes it to shear the woodruff key, and the flywheel moves out of ignition-firing position, and you get no spark.
If not... new plug or wire, or mechanic...

If it manually starts, and 11.9 volts only results in a 'click', chances are it's the starter. However, a bad cell could drop the amps to near nothing under load...
Try jump starting- if still a click, think starter. If it starts, battery, which you need anyway

[Art Mann]

The original poster has probably solved his problem during the 2.5 years since his first post.

[Lee Schierer]

I had two batteries that would not hold a full 13.5 volt charge, one from my boat and one from our lawn mower. I purchased a Battery Minder from amazon and charged both with that charger. Since then they have held a full charge for over a month. While there is no guarantee sometimes batteries get lead sulfate build up which causes them to not take a charge properly. This tender takes care of that by automatic high frequency pulse desulfator in addition to charging at a controlled rate.

[Ronald Blue]

A fully charged 12 volt battery should show 12.6 volts or a little above. I have never tested a battery unless it just came off charge that was above 13 volts. When running you should see above 13 and even into the mid 14 volt range. Alternators vary in their output voltage. Charging a battery off a vehicle isn't ideal but can be done. I doubt that 20 minutes would be sufficient though. As was suggested take it to someone to have a load test done. But if it shows the voltage is low they will say charge it and then test. I am sure he found the problem since he posted this a couple years ago.

[Rick Moyer]

The original poster has probably solved his problem during the 2.5 years since his first post.

2.5 years , plus yesterday!