I have Scag Cheetah with a 27HP B&S Commercial Series engine. Starting with a fully charged battery I can mow for about an hour and then, if I stop and try to restart, my battery doesn't have enough power to restart (starter motor just clicks). I apply booster power from a jump start kit and the engine starts ok and I carry on mowing.
After an overnight recharge the battery is at 12.9v. I start the engine and the battery is at 13.9v so I'm getting a charge into the battery while running and the amp meter shows about +3 amps. However, the battery will still discharge while mowing.
Any ideas about what can be happening to the battery charge while mowing? Is 13.9v with the engine running not enough?
Is battery maintenance free or have caps topside? Safety Glasses are a must around batteries. If you have caps remove them carefully with gloves on hands, are all six cells filled to top? If not use distilled water to top off, about $1 at Walmart per gallon. If you have a battery hydrometer you can check each cell, gauge on hydrometer will tell either pass or fail.
I have a maintenance free battery and its reasonably new (maybe 2 years old). That being said could it be the battery even though it charges overnight without any issues?
Cheers, Peter
#5
Scrubcadet10
i would charge the battery up, and remove the + and - cables from it, and check it with a multimeter every so often, if it drops while disconnected, bad battery.. if not, something on the mower is probably draining it.
#6
Hammermechanicman
Have you tested battery voltage with key off and then start the sngine and run at least half throttle and checked battery voltage? Then engage PTO and check battery voltage?
• Batteries are very strange beasts. They don't behave like other electrical components because they store electrical power as a chemical reaction. The only way to test or read a battery is with a "load test" which strips off the "surface charge" to reveal the true battery voltage. What you read with your handheld meter is NOT the true voltage.
• The quickest way to kill a battery is to over-charge it. The quickest way to over-charge a battery is to connect a "trickle charger" and walk away. So many of these chargers are sized for car batteries and deliver way too much charge. They literally "cook" the battery on the inside.
#9
Hammermechanicman
I have about a dozen of the harbor freight float chargers and use them on all my things with batteries for winter storage. They work good. I put them on fully charged batteies from a tractor, motor home (2), pickup truck, ZTR, snow blower. Boat. Batteries are good to go in the spring.
Did most of the diagnostic stuff (thanks for all the help) and generally things seemed to be ok so I did what I should have done early - bought a new battery and all is ok!
I have a maintenance free battery and its reasonably new (maybe 2 years old). That being said could it be the battery even though it charges overnight without any issues?
Cheers, Peter
I've had a few batteries like that in this past month. They would take a charge. But let them sit for any hour or so, and they wouldn't have enough left in them to crank the engine.
Peter, I would strongly suggest doing the simple charging system test with the new battery, if that's one of the things you didn't do prior, before declaring victory. Key off, measure batt voltage, engine running at regular operating speed, measure batt voltage. Measurement 1 = approx 12.5. Measurement 2 = 13-15. If meas 2 is LESS than meas 1, you still have a problem and soon enough, you'll be right back where you started! Please ignore this if you've already verified proper charging operation!
#14
StarTech
And he needs to doing the second test with the electric PTO engaged.
12.9v after overnight charge.
13.8v engine running. PTO off
12.5v engine running PTO on
12.8v after 2 hours mowing
12.5v after overnight stay in workshop not on charge. Started ok.
If my 12.8v (after mowing) reading was correct there looks to be an overnight discharge. I will let it sit over the weekend to see it discharges below 12.5v
Again, thanks for the follow up...
Cheers Peter
#17
Scrubcadet10
how long after mowing did you take the 4th reading? I may be wrong, but i think if you check a battery after it's been charging it will show a high voltage but it may not be the actual sitting battery voltage...
The good news Peter is your charging system looks to be working fine. Don't get too worried about a few tenths of a volt. Scrubcadet is right. The voltage will drop back down to 12.6 (in a perfect world with a new battery) over a bit of time when charging is stopped. Problems with batteries, bad connections, bad charging systems etc manifest themselves with voltage problems of a few volts, not tenths of volts, so you are good to go!
