Battery discharge while in use

[PeterJones]

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

 

[Rivets]

You need to test the charging system. This manual may be of some. https://www.briggsandstratton.com/c...a/en_us/Files/FAQs/alternator_replacement.pdf

 

[mechanic mark]

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.

https://www.google.com/search?q=battery+hydrometer&oq=battery+hydrometer&aqs=chrome..69i57.30645j0j4&sourceid=chrome&ie=UTF-8

 

[PeterJones]

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]

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]

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]

Remove battery & take to local auto parts store & have them load test battery, should be of no cost to you.

 

[Born2Mow]

• 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]

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]

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