Leaving AGM battery on float charger indefinitely?

[heypete]

Hi folks,

I have one of these chargers that I use for charging my Kymco motor scooter's battery when needed. When a battery is charged, it holds the voltage at 13.3V (according to my multimeter) to prevent discharge. As it's automatic, I presume it adjusts the current and voltage accordingly.

I recently bought an EverStart ES9BS battery from Wal-Mart (sold by Wal-Mart, distributed by Johnson Controls, but made by GS Yuasa in Taiwan -- whew!), as I thought my original Kymco battery was on the way out.

It turns out the Kymco battery is fine (evidently I didn't close the seat lid all the way, and the tiny dome light ran the battery down over the course of a few weeks, as there's no auto-shutoff in the simple circuit), but I had already put acid in the EverStart and charged it. As Tucson gets rather hot and seems to eat batteries, I thought I'd just keep the EverStart sitting at home on the float charger in case the OEM battery went flat from the heat; I could just swap the batteries, rather than waiting for the OEM one to charge back up.

Is it reasonable to leave the battery connected to the automatic float charger indefinitely (i.e. for months at a time), or should I disconnect it and reconnect it at intervals? Would it make sense to switch out the batteries every other month or something?

While $45 isn't a huge outlay of money for a battery, I'd like to avoid needlessly damaging it if I can avoid it.

 

[JimPghPA]

The colder you keep the battery the longer it will last, as long as you do not get it so cold that it frezes.

Put the charger on a 24 hour timer and set it up to only come on for a brief amount of time every day.

 

[heypete]

Jim,

The charger (and whatever battery is being charged) is inside my apartment, which is kept in the mid-70s. Maybe 80 during the hottest days of summer, but my apartment's mostly in the shade, so it doesn't get that bad. Freezing or extreme heat is unlikely.

 

[RnR]

With indoor storage I don't imagine you need more than 30-minutes on a periodic basis. The best thing to do is check the V before your timer (if you decide to use one) fires off, negating any surface charge influence. You'll get a feel for how often you really need the float.

Unless you are using a smart charger, I don't like to see a continuous charge being placed on a battery sharing your living space.

 

[JimPghPA]

Every 10 degree C / 18 degree F colder reduces most chemical reactions by half. This includes the acid of the electrolyte eating away the plates in the battery. So every 10 degree C colder you keep the battery on average for the life of the battery doubles the life expectancy of the battery.

The inverse is every 10 degree C / 18 degree F warmer you keep the battery on average for its life half's the life expectancy.

If you let the battery freeze it sill be destroyed. The freezing temperature for batteries varies, and is colder for a charged battery.

Ps: Overcharging a battery is bad for it.

And storing it discharged is bad for it.

 

[heypete]

Originally Posted By: RnR
Unless you are using a smart charger, I don't like to see a continuous charge being placed on a battery sharing your living space.


Evidently the Schumacher charger is a "smart" one, and they advertise that batteries can be left on it for an entire season. I just wanted to check here.

As for keeping a battery in my living space, a lead-acid battery is probably the least-exciting of potentially-dangerous things that I keep in my small apartment.

 

[tonycarguy]

Float chargers won't overcharge the battery (unless something unexpectedly fails inside the charger). However, floating forever isn't good for the battery as it causes the battery to slowly sulfate. Every few months it needs to be charged at > 14V for a few hours. I'd leave the charger connected most of the time, then every couple of months, disconnect it for several days to let the battery drain slightly, then recharge. The charger should detect the battery is slightly drained and charge it at ~14.4

 

[kc8adu]

well regulated float will not hurt it.
most of the modern agm's have very low self discharge anyway.
if you hook it up once a month to the maintainer overnight it will be fine.float charging is a trade off between preventing sulphation and accelerating positive grid corrosion.thats why close regulation of voltage is critical.

 

[mechtech2]

Jim has a point about heat.
Southern cars eat batteries.
2-3 years is normal in Texas.
And this is with the special batteries for the South.
Northern batteries would not last as long down there!

 

[ahoier]

I'd be afraid to leave a battery unattended while on a charger....particularly those small motorcycle batteries; I've heard of them blowing acid everywhere.....but if you trust your charger/equipment, go along with it

 

[JimPghPA]

Put the battery in a glass tray with sides, so it would contain any over-flow.