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Forum Index : Electronics : Best charging scheme for small lead acid battery

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Haxby

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Joined: 07/07/2008
Location: Australia
Posts: 423
Posted: 07:09am 28 Nov 2020
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Hello brains trust. Quick question about small lead acid batteries:

I have a jetski that isn't used during winter. What's the best charging scheme to keep the battery alive?

Should I trickle charge all the time, or should I charge at a few amps say once a week for a couple of hours on a timer?
 
Warpspeed
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Joined: 09/08/2007
Location: Australia
Posts: 4406
Posted: 08:34am 28 Nov 2020
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Trickle charging (or constant float charging at 13.8v) all the time will result in gradual loss of battery capacity.  This can frequently be seen in standby batteries used in such things a burglar alarms.

Be very careful with "a few amps once a week". Any type of sealed battery must never be allowed to gas. Every time you do it, a little water is lost through electrolysis, and the battery will eventually dry out and be useless.

Sealed batteries are not really designed to be long life devices anyway.  They are designed for fully sealed convenience, not for long life.

Anyhow, about the best you can do is a constant current charge at a very low rate up to a voltage below the gassing point. That depends on temperature, but around 14v for a 12v battery might be about right.

When it reaches 14v, shut off charging totally, and allow it to self discharge over a period down to about 12.2 volts. When it hits that voltage, turn the charger back on.

The battery will constantly cycle between 12.2v and 14v over a period which may be from a day to several weeks, depending on battery size and condition, and charging rate.

This seems to work particularly well with flooded lead acid batteries, but should also work with sealed lead acid batteries. Its about the best you can hope for.
Cheers,  Tony.
 
Haxby

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Joined: 07/07/2008
Location: Australia
Posts: 423
Posted: 10:29pm 28 Nov 2020
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Thanks warpspeed!
 
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