Can you overcharge a lawn mower battery really?

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So, can you overcharge a lawn mower battery really?

Occasionally, your lawn mower battery needs to be charged especially if you’re just coming out of the winter cold- prolonged storage tends to discharge the battery fully.

And as with cars and trucks batteries, not properly charging the battery could shorten the battery life- you could quite simply kill the battery if you don’t properly charge it.

So, can you overcharge a lawn mower battery really?

Short answer: YES (technically)… You can easily overcharge your lawn mower battery (and damage it) if you leave it plugged into the charger for too long (some of us love leaving it connected overnight).

Put another way, if your charger doesn’t automatically cut off, it will end up overcharging leading to the battery overheating and damaging it or reducing its life expectancy.

What happens when you overcharge a battery?

So, what exactly happens if a lawn battery is overcharged (leading to probable damage)?

Now, in general, lead acid batteries overcharging corrodes the cathodes, heightens water consumption, and raises the temperature (inside the battery).

The best you can hope for with this is reduced capacity and, of course, shorter life cycle.

At the worst, this could trigger thermal runaway- a situation in which the current flowing through cells (or the battery on charge) makes the cell’s temperature rise.

This will increase the current (with the continued rise in temperature).

I should add that lead acid batteries may emit toxic gases once overcharged.

The scenario is mirrored in lithium-ion batteries too…

To be clear, if your lawn mower uses a lithium-ion battery, you’re likely to create unstable conditions (again inside the battery) when you leave it under charge for too long.

The result is excessive pressure build-up and the other issues I mentioned previously such as the possibility of causing thermal runaway (this can damage cells and possibly cause fire).

Quick Tip: If you notice a bulge in the battery case (it may even be warped) after leaving it to charge unattended, this is a pointer to it entering the state of getting overcharged. There are other signs such as a super strong smell, the battery being scalding hot on touch, and battery acid leaking at the top (for lead acid batteries).


How to prevent a lawn mower battery from overcharging

I have seen folks with chargers that don’t cut off result to setting an alarm on their phones so that the phone reminds them to keep checking the battery’s charging state every 1 or so hours.

Fortunately, there are several less cumbersome ways of preventing your battery from being overcharged.

Here are some great suggestions:

· Use the right charger

Now, the first secret is using the right charger when charging your lawn mower battery.

This simply means the charger you’re using must match your battery with respect to the AH rating output and voltage.

Other than that, it is important to make sure the charger you’re using features built-in protection mechanism to prevent overcharging (most modern chargers have this handy feature).

If not, upgrade to a good compatible charger.

Shop for the best lawn mower battery charger on Amazon

· Build an overcharge protection circuit

The other alternative that you could consider is building an overcharge protection circuit that you can use with your current battery charger.

Needless to say, this can only be feasible if you know your way around electronic circuits.

· Use a battery tender

Perhaps the easiest option is to invest in a battery tender.

It fully charges your mower’s battery and then switches to float mode automatically to maintain the right voltage levels to prevent overcharging.

The other advantage of a battery tender is that it charges in 4 steps (Initialization, Bulk Charge, Absorption, and the aforementioned Float Mode) so the battery power is better optimized.

A word on lawn mower voltage regulator

As you may be aware, a voltage regulator is extremely handy in controlling the re-charging of batteries used in a lawn mower.

You can check your lawn mower but, in general, a voltage regulator is typically introduced between alternator output & the input to a battery to prevent it from overcharging.

That being the case, a lawn mower battery will surely overcharge if the built-in voltage regulator is faulty.

It is, therefore, important to test the voltage regulator from time to time to make sure it is working properly.

Shop for the best voltage regulator for lawn mower battery on Amazon

Can you overcharge a lawn mower battery?- other frequently asked questions

Can you charge a lawn mower battery with a car?

For the most part, yes! since many modern lawn mowers use the  same 12-volt batteries used in cars. The battery should charge without being overcharged as long as it is in tiptop condition.

How often should I charge my lawn mower battery?

To be sure that it maintains a full charge during the entire off season, hook up a battery tender to the uninstalled battery and leave it connected throughout.

Your battery will be in excellent condition and ready to go when you return for the new season.

Do you have to charge a new lawn mower battery?

No! Your lawn mower battery should have enough charge on it right out of the box.

Thus, you don’t need to charge it – they tend to have sufficient cranking power unless it has sat for too long on the shelf.

That means you should go ahead and charge it before you throw it in the mower (preferably on slow charge) if you’re unsure how long it has been sitting there.

Wrapping it up

Other than cooking the battery before its time, there are other bad things -some quite dangerous as mentioned above- that can happen once a battery is overcharged.

As such, it is in your best interest to take the right measures- and we have highlighted a couple of them in this guide- to prevent it from being overcharged.

Good luck mate!


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