Battery discharge while in use

PeterJones

Member
Joined
Jan 3, 2017
Threads
6
Messages
36
Hi,

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?

TIA - Peter
 

mechanic mark

Lawn Pro
Joined
Jul 15, 2013
Threads
152
Messages
5,641

PeterJones

Member
Joined
Jan 3, 2017
Threads
6
Messages
36
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
 

Scrubcadet10

Lawn Addict
Joined
Sep 24, 2017
Threads
128
Messages
2,894
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.
 

Hammermechanicman

Lawn Addict
Joined
Jan 10, 2020
Threads
8
Messages
1,271
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?
 

mechanic mark

Lawn Pro
Joined
Jul 15, 2013
Threads
152
Messages
5,641
Remove battery & take to local auto parts store & have them load test battery, should be of no cost to you.
 

Born2Mow

Member
Joined
Sep 18, 2020
Threads
2
Messages
34
• 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.
 

Hammermechanicman

Lawn Addict
Joined
Jan 10, 2020
Threads
8
Messages
1,271
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.
 

PeterJones

Member
Joined
Jan 3, 2017
Threads
6
Messages
36
For all that have replied, thank you! I haven't been getting e-mails saying my post had replies and I didn't know I had any until just now.

I will carry out the suggested checks and report back....

Cheers, Peter
 
Top