What keeps draining my lawn mower battery?

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We received this question from a frustrated lawn mower owner: “What keeps draining my lawn mower battery?

You want to read this to the end if you have the same question…

What keeps draining my lawn mower battery?

Picture this: Your lawn battery has been fine all along then suddenly, it stops holding its charge anymore (and starts to drain extremely fast).

And by now you have checked all the connections and you have made sure you don’t have a short somewhere.

Curiously, the battery recharges without problems and has not shown signs of damage.

In short, you cannot find a reason why your lawn battery keeps draining.

Well, don’t write off the battery yet; here are some possible reasons and their workarounds….

What keeps draining my lawn mower battery? – Common causes and solutions

If your lawn tractor battery can’t hold a charge at the moment and keeps draining really fast, you need to check the following:

You could be having a loose connection somewhere

You may not have noticed signs of the connections having a short but it is possible that there is a loose connection on the battery.

The most common culprit here is loose cables -check where they usually connect to battery posts.

Just to be clear, such a loose connection (if it is indeed there) makes the battery work harder, a situation that causes it to drain power more quickly.

Suggested Solution:

As hinted above, check if the cables are loose and tighten the connection.

Before that, be sure to clean any corrosion off the battery posts.

Believe it or not, this could be all you need to do to restore your battery’s ability to retain a charge.


A faulty voltage regulator

A bad voltage regulator has been known to cause a battery to keep draining pretty fast.

It should be mentioned that a voltage regulator and an alternator are included in the electrical system/set-up that recharges most riding mower batteries.

Thus, the battery is unlikely to retain charge long enough if the components have issues.

Suggested Solution:

Test the voltage regulator first through the battery (A multimeter will be needed).


  1. Set multimeter to be able to read volts(∆V).
  2. Start the engine.
  3. Partially turn the key on the mower- you want the headlights to come on to create some load.
  4. Hook up the +ve (red) cable from the multimeter to the battery’s +ve terminal.
  5. Connect the -ve (black) cable from the multimeter to the battery’s -ve terminal.
  6. Check the reading on the multimeter – if the voltage regulator is fine, it should read 13.8 – 14.5 volts.

A reading above 14.5 volts is the clearest sign that the voltage regulator is dying/dead meaning a replacement could be needed.

If this is the case, you can order a compatible replacement lawn mower voltage regulator.

If this was indeed the issue, it should solve the problem of your battery draining rapidly and it may again start to stay charged.

Here is a voltage regulator that works perfectly for mowers with 18-24HP Briggs & Stratton engine (with 10A, 13A, 14A, and 16A electrical charging systems) including brands such as EZTRAK, John Deere, Cub Cadet, and more.

Quick Tip: To check the alternator, just turn on the mower’s headlights. Then, turn the engine off. If the lights go dim, your alternator works. If they do not, it doesn’t and needs replacement.

You’re not running the lawn tractor at full throttle

Another possible cause is failing to run your lawnmower at full throttle while trimming grass.

You see: It is important to ensure you’re running the machine at full throttle during the operation as it can only achieve the RPMs (revolutions per minute) required to recharge the battery that way.

In fact, the mower’s battery charging system becomes way less effective with just a small reduction in RPMs.

This will potentially cause the battery to die between mowings.

Suggested Solution:

Simply run it at full throttle next time and see if the charge will last.

You are leaving some mower components running

As you may be aware, the mower’s electrical system runs components such as headlamps and horns.

But when you have turned off the engine, these draw juice from the battery.

Thus, it goes without saying that leaving any of the components on unknowingly (while the engine is off) can make the battery to drain unusually quickly.

Suggested Solution:

The fix is straightforward here: make sure you have not left any of the battery-draining components on after turning off the engine.


The battery could be dying (sorry!)

If all the above has failed, perhaps it is time to replace the battery- it cannot hold a charge long enough if it has reached the end of the road.

In truth, this is the most likely cause if you have an older lawn mower battery that can no longer stay charged for that long.

It is worth adding that lawn mower batteries generally last for between 3 – 5 years with proper care.

Speaking of proper care, it simply means disconnecting the battery when winter comes and storing it where it can’t freeze.

In addition, it may be worth using a 12 Volt float charger/A battery tender to keep the battery in tiptop condition for the new season.

Quick Tip: To be sure, consider testing the voltage your battery is outputting- you again use a multimeter. For the test, any battery outputting 11.5-volts or less is most probably worn out and needs to be replaced.

Suggested Solution:

If you suspect that the battery has exhausted its serviceable life (or you have confirmed that it has degraded beyond reversal), the best remedy is to replace the battery.

Shop for a replacement battery on Amazon now



We hope that this gives you a solution if your lawn mower battery just began to drain strangely fast.

Try the suggestions and see if it will go back to retaining charge as it has always done.

That is it, guys!


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