Small Engines (Lawn Mowers, etc.)/riding mower battery


QUESTION: I have a riding mower whose battery gets low (based on charger) after 3-4 hours of use. Battery measures 50-75% (only measures 25% intervals) after this this use.

Is this likely the alternator? How do I diagnose it?

It is a Cub Cadet HDS 2135.

ANSWER: The best method to test the charging system is to use a DC shunt.  Shunts can be expensive but you could make one yourself as there are plans/directions on the internet.

You will need a digital multimeter as well.  

Do you have a multimeter to test for voltage, current and resistance?

Let me know.

---------- FOLLOW-UP ----------

QUESTION: I do not have a digital multimeter (may be possible to borrow one) and am not sure how many amps a DC shunt would need to handle.

Maybe I should just replace the alternator and see if that fixes it. Are there any other likely causes of the problem?

Electrical parts for mower engine can be quite pricey.

Have you dis-connected the battery and cleaned the battery terminals and cable ends with a wirebrush?  I have fixed a lot of charging problems just by dis-connecting and cleaning the terminals even though they looked clean.

You purchase a cheap multimeter at you local hardware store or Harbor Freight.  Less than $5 at Harbor Freight and they work fine.

I rarely use my shunt....99% of the time just verifying the voltage is correct, mower off and mower running, works well. All you need is a meter that can read 10-15 volts DC...the HF models have a 20 volt DC scale.

Have you watched the You Tube videos on how to check the charging system?


Small Engines (Lawn Mowers, etc.)

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Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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