# Lead acid battery charger plans

#### Doc Cox

Joined Nov 9, 2011
1
Good evening, currently building a battery desulphater and have been looking for a simple battery charger diagram where I can adjust the volts and amps seperately up to approximately 24volts, no luck so far so hoping someone can help me, many thanks Doc Cox

#### wayneh

Joined Sep 9, 2010
16,500
Voltage and current can't really be adjusted independently - one depends on the other and you don't have any degrees of freedom. You can set a current or voltage limit, however, while at a set voltage or current.

But anyway, just search this forum for desulfater or desulphater; I know there's been a recent thread on the topic.

#### SgtWookie

Joined Jul 17, 2007
22,220
I've been trying to discourage people from charging batteries in series as if they were one large battery of higher voltage. You can really shoot yourself in the proverbial foot that way.

If one cell develops a short in one of the batteries in the series string, then the remaining cells in the string will be overcharged, which will drastically shorten the lives of the remaining good cells. It more or less has a China syndrome effect; once one of them fails, the stress greatly increases on the rest of the cells, and they start dropping like flies.

You can wind up ruining several perfectly good batteries, due to just one bad battery in a series string.

The problem also occurs when you have a bank of batteries wired in series-parallel.
Say you have several 12v batteries wired as a 24v battery bank. One of the cells in one of the strings shorts.

While the batteries are being charged, the one in series with the battery that has a shorted cell gets overcharged, and gases excessively.

Once the charge cycle has completed, that pair of cells' voltage rapidly declines due to the shorted cell; the rest of the battery bank becomes discharged to the point where sulfation begins, or the charger kicks back on. If the charger cycles excessively, you can wind up with a higher electric bill than you thought you'd get.

You're much better off to charge the two batteries individually using a pair of 12v chargers.

Now if the battery is a military-type 24v battery for an aircraft or aviation GSE, that's a different matter; you really can't do anything but charge them at ~28v.

#### franny66

Joined May 6, 2012
1
i think this id: KA35S281 is the best way to charge the lead acid battery. it has a simple circuit to use.

#### SgtWookie

Joined Jul 17, 2007
22,220
Franny66,
I am not certain where you are, but the KA35S281 does not appear to be available anywhere in the USA.

The circuit you posted is indeed simple, but being a linear regulator, you would need a very large heat sink on the IRF9530.