This is what happens when you overcharge a lead acid battery

[MowerMike]

So, I left the battery pack for my Earthwise 14" battery powered mower connected unattended in my spare bedroom to my "smart" charger, which is supposed to switch automatically to a trickle charge maintenance mode on the battery has fully recharged, when I noticed a very strong smell coming from the bedroom. When I walked in I was shocked to see that the battery was scalding hot, the plastic case was warped and there was battery acid leaking out at the top. I quickly turned off the charger, which was also extremely hot, and took the battery outside, where I removed the cover and took some pictures.



Note the the bottom of the case has bulged out and the case no longer sits flat on the ground. Also the top of the case and battery tops are bulged upwards as well. A replacement battery costs more than I paid for the entire mower, so I've just ordered a pair of wheelchair/scooter batteries that will cost less than half as much and just wire them directly into the mower. I will have to charge them in the mower and make up different wires for the F2 terminals, but that is the only downside.

 

[MowerMike]

My home made replacement battery saved me $63

Well, the replacement batteries arrived yesterday and I successfully wired them into my mower per the attached photos. I used 12 AWG wire and crimp connectors throughout and made up spacers with some old closed cell foam I had lying around. I was able to salvage the spring connector piece from the battery pack that connects it to the mower, so I will be able to unplug the batteries w/o cutting any wires or pulling apart the terminals. The battery can be charged inside the mower by plugging the charger into a port at the rear of the mower. Since the battery terminals are exposed, I can check the charging status directly with a voltmeter w/o having to start the mower. The only concern I have is that the manufacturing date codes on the batteries is April, 2011, which makes them over 2 years old and may mean a reduced service life. They did charge up properly and the mower works well so I'm crossing my fingers. I'm using the OEM charger instead of the aftermarket "smart" charger that destroyed the original battery.

 

[reynoldston]

Nice and neat looking wiring job.

 

[MowerMike]

I revised the battery wiring

Well, it's been over a year since I replaced the batteries, and it's still running great. One thing I was never happy with was the way I originally wired the batteries. For one thing, the two adjacent live battery terminals were only an inch apart with a 24 volt drop across them. I have a 24 volt charger with alligator clamps that I didn't dare use due fear of shorting them. Also, I had to use a lot of wire to connect the two batteries in series. So, I've rewired the batteries as shown with a short jumper piece in the middle and the + and - connections to the mower on the outside, which has reduced the total length of wire by over a foot. As you can see from the before and after photos, the wiring is a lot tidier and I can easily connect alligator clamps for attachment to my 24 volt fast charger.

 

[MowerMike]

So, one of the batteries is now dead and leaking acid. It was advertised as "non-spillable", so I guess that's what I get for buying cheap Chinese batteries on the internet. I haven't used this mower for quite awhile since getting several newer lithium-ion battery mowers, so I won't bother replacing the battery. It was quite heavy and had very small wheels, so it was very hard to push.

 

[7394]

What 'smart-charger' did the overcharging ?

I only use the brand Battery MINDers* myself.

 

[bertsmobile1]

Despite the fact this is a very old thread.
1) never trust "smart" chargers because they are not smart and they are not good for the battery either.
2) battery tenders are just the same as smart chargers, use the same control chip, cost 2 to 4 times as much and have a lower max charge rate & duty cycle.
3) almost none of them will recharge a dead flat battery and when they do they damage them thus shortening their life then the makers blame you for putting them on a dead flat battery.
Best way is to hook a standard charger to the battery through a timer switch.
for a charged battery, 15 minutes once a week is all they need to keep them in tip top condition.

 

[MowerMike]

What 'smart-charger' did the overcharging ?

I only use the brand Battery MINDers* myself.

The charger that destroyed the original battery was a Schumacher (DSR) INC-2405A, 24Vdc, 5A. Curiously, it works fine with a different battery that uses AGM technology, so I'm not quite sure if the problem may have been at least in part caused by the battery itself. In any event, I no longer leave any chargers connected for more than 12 hours at a time.

 

[7394]

I think it may have been the battery also.. 5Amp is a lot for a "smart charger" as you posted tho.

I leave my bikes & mowers hooked up to Battery MINDers* all winter long, never an issue. Mine are only 1.5 & a .75Ma

 

[Teds]

Charging lead-acid type batteries indoors or around living quarters is not advisable, not simply just because of the explosion hazard. Batteries produce hydrogen during charging as is well known but there are also other lesser known chemicals produced during outgassing that are toxic. When the battery manufacturers say use "good ventilation" they mean it.