Q about Battery Charging

[Norm Dresner]

A company called ZBattery.com is offering a "6V Sealed Lead Acid Battery
Charger" which, judging by the picture at
http://store.yahoo.com/zbattery/6v-chg.html
appears to be nothing but a 6V DC wall wart. Questions:

1. Is this product likely to charge a (6v sealed) lead acid battery?

2. Is this product likely to damage a (6v sealed) lead acid battery?

3. If the answer to #1 is "yes", would any reasonable 6V DC wall wart be
usable to charge a (6v sealed) lead acid battery?

TIA

Norm

 

[John Jardine.]

A company called ZBattery.com is offering a "6V Sealed Lead Acid Battery
Charger" which, judging by the picture at
http://store.yahoo.com/zbattery/6v-chg.html
appears to be nothing but a 6V DC wall wart. Questions:

1. Is this product likely to charge a (6v sealed) lead acid battery?

2. Is this product likely to damage a (6v sealed) lead acid battery?

3. If the answer to #1 is "yes", would any reasonable 6V DC wall wart be
usable to charge a (6v sealed) lead acid battery?

TIA

Norm

Yes!
Yes!
Yes!

john

 

[Rich Grise]

A company called ZBattery.com is offering a "6V Sealed Lead Acid Battery
Charger" which, judging by the picture at
http://store.yahoo.com/zbattery/6v-chg.html
appears to be nothing but a 6V DC wall wart. Questions:

1. Is this product likely to charge a (6v sealed) lead acid battery?

2. Is this product likely to damage a (6v sealed) lead acid battery?

3. If the answer to #1 is "yes", would any reasonable 6V DC wall wart be
usable to charge a (6v sealed) lead acid battery?

It's an ordinary wall wart.

1. yes, it probably can, "for capacities up to 18Ah".

2. Did you read any of the words there?

"Note:
Charger should not be left on battery indefinitely.
Optimum charging time can be calculated by figuring the following:

Capacity / 0.6= maximum charge time (assuming completely drained
battery)

So for a 4.5Ah battery use the following equation - 4.5 / 0.6 = 7.5
hours maximum charge

Please note that overcharging a sealed lead acid battery can permanently
damage the battery, or reduce the capacity of the battery."

So, yes, it's likely to damage the battery if you neglect to follow the
instructions.

Good Luck!
Rich

 

[Macgyver]

Interesting that the picture actually shows an AC adaptor with the
diagram on the front for a standard DC appliance plug on the output.
This, plus the fact that the unit is only rated for 6V 600mA (you are
not going to be able to charge an 18AH battery properly with this)
leads me to believe either the picture is wrong or that the Marketing
department were a little hung over when they wrote it (or more likely
both).

Misleading data supplied next to picture seems to indicate a 600mA
constant current sourceSomething is definitely not right.

Avoid this product as if it were a pile of dead chipmunks!

And no, you cannot use a standard wall wart to charge a sealed lead
acid battery, without additional circuitry to correctly charge and
protect the battery. At least they got the fact that the battery
should not be left on this "charger" indefinitely.

 

[Chris Jones]

A company called ZBattery.com is offering a "6V Sealed Lead Acid Battery
Charger" which, judging by the picture at
http://store.yahoo.com/zbattery/6v-chg.html
appears to be nothing but a 6V DC wall wart. Questions:

1. Is this product likely to charge a (6v sealed) lead acid battery?

2. Is this product likely to damage a (6v sealed) lead acid battery?

3. If the answer to #1 is "yes", would any reasonable 6V DC wall wart be
usable to charge a (6v sealed) lead acid battery?

TIA

Norm

If you want to charge a lead-acid battery without damaging it, then I
suggest one method is to build yourself a regulated power supply with a
LM317 or similar, which could then be powered by some kind of wall-wart.
You can adjust this to the voltage which the battery manufacturer
recommends, e.g. look on the Yuasa web page, they have quite a bit of info.
If the power source which is driving your LM317 would be damaged by a high
current flowing then my approach has been to put some form of current
limiting between the power source and the LM317, at its simplest this could
just be a resistor in series with the input terminal of the LM317, which
causes the LM317 to drop-out when the battery draws more current than the
power source could safely supply. I also was worried that the battery
might be discharged if the mains power failed during the charging process
so I put a diode between the LM317 and the battery, but note that if you do
this then the voltage from the LM317 definitely needs to be increased so
that you get the right voltage after the diode. It is very important to
measure the voltage at the battery terminals and check that this is correct
according to the battery maker's instructions. The LM317 will probably
need a heatsink. I suggest you put a fuse in series with the battery
terminal to reduce the risk of fire if something in your circuit gets
shorted.

Chris

 

[kell]

A company called ZBattery.com is offering a "6V Sealed Lead Acid Battery
Charger" which, judging by the picture at
http://store.yahoo.com/zbattery/6v-chg.html
appears to be nothing but a 6V DC wall wart. Questions:

1. Is this product likely to charge a (6v sealed) lead acid battery?

2. Is this product likely to damage a (6v sealed) lead acid battery?

3. If the answer to #1 is "yes", would any reasonable 6V DC wall wart be
usable to charge a (6v sealed) lead acid battery?

TIA

Norm

The wall wart puts out a nominal 600 mA at 6 volts. That's
approximate; those ratings they print on wall wart labels are not real
exact.
6 volts is pretty flat for a "6 volt" lead acid battery, but if a
battery really is that low and you put it on the wall wart, it would
deliver ballpark 600 mA into the battery.
As the battery takes on charge and its voltage rises, the current
coming from the wall wart decreases. If the wall wart is pretty well
matched for charging "6 volt" sealed lead acid batteries, then as the
voltage gets around 7.2 to 7.5 volts, there will still be some current,
but nowhere near the original 600 mA.
This is called "taper charging," which is a fancy word for CHEAP
UNREGULATED CHARGER.
The problem lies in the fact that open circuit voltage on the wall wart
is likely to be significantly higher than is healthy to expose the
battery to, which is why you can't leave a battery on a "taper" charger
indefinitely. It might go up to 10 volts eventually and damage your
battery. And in the worst case, maybe this could happen even without
the battery getting a full charge in the process!
Proper charging for lead acid batteries calls for putting enough charge
into them at a limited current until the voltage gets up to 2.4 volts
per cell (flooded type) or as much as 2.5 for AGM batteries (sometimes
called sealed or valve regulated). Then the charging protocol calls
for holding a constant voltage on the battery for some time; the
current flowing into the battery will decline eventually, and when it
gets to about 3% of the amp hour rating of the battery, the battery is
considered charged and should be taken off the charger or maintained at
a float voltage of about 2.2 or 2.3 volts per cell.
I charge batteries all the time with just a transformer and rectifier,
but I know what I'm doing. Timing the charge isn't really the best
approach.

 

[James D. Veale]

I've found the following site useful...

http://www.gotbatteries.com

They have "Powersonic" lead-acid chargers in a variety of capacities.
They also sell a 6 volt lead acid in a "lantern" form factor. I've
used these for several years and the PSC-61000A charger.

Jim Veale

A company called ZBattery.com is offering a "6V Sealed Lead Acid Battery
Charger" which, judging by the picture at
http://store.yahoo.com/zbattery/6v-chg.html
appears to be nothing but a 6V DC wall wart. Questions:

 

[Ted Wilson]

A company called ZBattery.com is offering a "6V Sealed Lead Acid Battery
Charger" which, judging by the picture at
http://store.yahoo.com/zbattery/6v-chg.html
appears to be nothing but a 6V DC wall wart. Questions:

1. Is this product likely to charge a (6v sealed) lead acid battery?

2. Is this product likely to damage a (6v sealed) lead acid battery?

3. If the answer to #1 is "yes", would any reasonable 6V DC wall wart be
usable to charge a (6v sealed) lead acid battery?

TIA

Norm

Sealed lead-acid batteries should be charged at constant voltage and a 6V
SLA requires a fixed voltage of nominally 6.8V. (If you really want to do
it properly, the voltage should be temperature compensated - can't remember
the mV/C adjustment required OTTOMH, but a quick Google should throw up all
the info you need. This would provide optimum protection for the battery
for long-term use, but charging at 6.8V at normal room temperatures is good
enough for most applications).

Any half decent charger will usually include some form of current limit, but
this is usually for the protection of the charger itself, as opposed to the
battery, which can handle quite large currents.

One of the appeals of sealed lead-acid batteries is that they can be left on
'float charge' on a suitable charger pretty much indefinitely, with the
charger and battery taking care of themselves without the need for
intervention or monitoring.

However, the charger shown in the link doesn't come close to being a 'good'
charger and should only be used with care - the SLA would almost certainly
be damaged if left connected to such a supply for any length of time.

Ted

 

[kell]

Sealed lead-acid batteries should be charged at constant voltage and a 6V
SLA requires a fixed voltage of nominally 6.8V. (If you really want to do
it properly, the voltage should be temperature compensated - can't remember
the mV/C adjustment required OTTOMH, but a quick Google should throw up all
the info you need. This would provide optimum protection for the battery
for long-term use, but charging at 6.8V at normal room temperatures is good
enough for most applications).

Any half decent charger will usually include some form of current limit, but
this is usually for the protection of the charger itself, as opposed to the
battery, which can handle quite large currents.

One of the appeals of sealed lead-acid batteries is that they can be left on
'float charge' on a suitable charger pretty much indefinitely, with the
charger and battery taking care of themselves without the need for
intervention or monitoring.

However, the charger shown in the link doesn't come close to being a 'good'
charger and should only be used with care - the SLA would almost certainly
be damaged if left connected to such a supply for any length of time.

Ted

6.8 volts is good for float, but if you want to charge a battery in any
reasonable time you need a higher voltage than that..