Look at some of those battery powered toy cars and battery powered two
wheelers in the stores.The kind meant for kids to ride around the yard
on.Check the information on the batteries and the battery chargers for
those batteries.Sometimes,thrift stores and yard sales have second hand
battery powered kids cars and battery powered two wheelers.I see them
every once in a while at the Goodwill store near me.I have no idea how
much those gel cell batteries cost or how long gel cell batteries are
suppose to last,I have never used them before.
cuhulin

www.devilfinder.com Information about Gel Cell Batteries and Gel
Cell Battery Chargers

Some information there at that good old devilfinder.com search.
cuhulin

Look at some of those battery powered toy cars and battery powered two
wheelers in the stores.The kind meant for kids to ride around the yard
on.Check the information on the batteries and the battery chargers for
those batteries.Sometimes,thrift stores and yard sales have second hand

battery powered kids cars and battery powered two wheelers.I see them
every once in a while at the Goodwill store near me.I have no idea how
much those gel cell batteries cost or how long gel cell batteries are
suppose to last,I have never used them before.
cuhulin

The sites I checked seemed to have quality gel cells in about the right
size (I think) for my application - 12v, 18 or higher amp-hours -
starting at around $20 to $40, not bad at all. Chargers are all over
the place, from a 1-amp charger at 6 to 20 bucks up to 100-amp chargers
(overkill, I'd bet) for silly sums of money.

My kid has a toy motorcycle powered by a gel cell, now that I think of
it - requires about 2 hours charge for 1/2 hour use before it gets too
weak to be useful. The charger is probably near a trickle compared
with the optimal output of the battery, but I will check - thank for
the idea!

Bruce Jensen

I use small bench supplies because I have a lot of small bench
supplies. You set it up for 13.8VDC, and the current limit cuts in if
the battery wants more. Gell cells don't like excessive voltage, so I
avoid the cheaper car battery chargers. My bench suplies range from 1A
to 8A, no where near as heavy duty as a car battery charger.

You could buy a "cyclic" charger if you want faster charging. For
instance, for the np7-12, you could hit it with 14.5V to 15V at
1.75Amps to charge it. I personally don't like doing this, and rather
just set up the float voltage (13.5 to 13.8V). I only mention the
np7-12 because I have one next to me. The one I use in the field is
much larger, and unfortunately not handy. [I put it in a West Marine
battery carrier, so it's all locked up so to speak.] Note that you can
float a SLA (sealed lead acid) at the float voltage forever. That is
how you use the battery in backup mode.

The charge time at the float voltage won't be linear. As the battery
charges, it draws less current. If you want to quickly charge the SLA,
you can buy a cyclic charger. As I said, I use my infrequently, so the
bench supply works for me. http://www.xantrex.com/ has chargers meant
for SLA, but I still suggest getting two batteries and just floating
one on a good bench charger (HP, Labda, Sorensonmetc.] The only problem
with a bench supply is some jerk could crank up the voltage.

You can drain the SLA down to 10.5V (i.e. 1.75V/cell). In the field, I
use a cheap Harbor Freight DVM. No use getting a good meter all
scratched up.

I don't like the idea of using car batteries for this application. The
outgassing can ruin electronics or your lungs. SLA batteries are safe
enough to install inside electronics gear. I've use noise measuring
gear that would disconnect from the mains when making a measurement,
using an internal SLA to power the electronics.

bpnjensen wrote:
M...sushi.com wrote:

I suggest getting a gell cell to avoid battery acid spills or fumes. I
only use mine when in the field, so I don't have a set up as you
suggest. I charge my battery from a bench supply using 13.8v as a
float voltage.

Thanks, also to RHF and Cuhulin. I just took a look at these gel cells
on a couple of websites, incluidng the one recommended by RHF and some
others. This, of course, raises more questions :-)

How big a charger must one have? Must the current available on the
charger be some minimum fraction of the amp-hours of the battery, or
can one use a smaller charger and just leave it on longer?

Also, is the charge time a simple proportion between the charger
current and the battery amp-hour value? i.e., to recharge an 18
amp-hour battery with a 10-amp charger, the charge time is 1.8 hours -
?

Is it OK to drain a gel cell until it loses almost all of its charge?
Or is there some minimum level at which one must stop (25%, 50% or
etc)?

Finally, once the gel cell battery is fully charged, how does one know,
and will it hurt if the charger is kept on without checking? Does a
charger have a device to shut off when full charge is reached?

Thanks,
Bruce

Wet cell car type batteries.Back in the 1950's or 1960's,I read in one
of my Popular Science or Popular Mechanics magazines if you will drain
the acid out of the battery into a porcelain or glass container and
flush the crud out of the battery with a water hose (no nozzle on the
water hose and the water turned on at low pressure) and then pour the
acid through a piece of cloth (to filter out crud in the acid) and pour
the acid back into the battery,that will extend the life of the
battery.Pure Sulphuric battery acid has a chemical burn equal to 735
degrees temperture,same as a red hot poker at 735 degrees.I used to work
at a factory that manufactured auto/truck/lawnmower batteries and
believe you me,,, I do know about that pure sulphuric battery acid! One
drop of it on your hide will make you jump ten feet high! The acid in
the car type batteries is very,very watered down.
cuhulin

Freight on these SLA's can be an issue. Sometimes it pays just to buy
the battery in a store.

A bit OT, but depending on where you use the battery, it sometimes
helps to install rubber feet on the bottom IF you will have the battery
sitting on cold cement. I do this for outdoor applications.

bpnjensen wrote:
Look at some of those battery powered toy cars and battery powered two
wheelers in the stores.The kind meant for kids to ride around the yard
on.Check the information on the batteries and the battery chargers for
those batteries.Sometimes,thrift stores and yard sales have second hand

battery powered kids cars and battery powered two wheelers.I see them
every once in a while at the Goodwill store near me.I have no idea how
much those gel cell batteries cost or how long gel cell batteries are
suppose to last,I have never used them before.
cuhulin

The sites I checked seemed to have quality gel cells in about the right
size (I think) for my application - 12v, 18 or higher amp-hours -
starting at around $20 to $40, not bad at all. Chargers are all over
the place, from a 1-amp charger at 6 to 20 bucks up to 100-amp chargers
(overkill, I'd bet) for silly sums of money.

My kid has a toy motorcycle powered by a gel cell, now that I think of
it - requires about 2 hours charge for 1/2 hour use before it gets too
weak to be useful. The charger is probably near a trickle compared
with the optimal output of the battery, but I will check - thank for
the idea!

Bruce Jensen

Freight on these SLA's can be an issue. Sometimes it pays just to buy
the battery in a store.

Good tip.

A bit OT, but depending on where you use the battery, it sometimes
helps to install rubber feet on the bottom IF you will have the battery

sitting on cold cement. I do this for outdoor applications.

It will be in our bedroom, mounted on the inner back wall of the radio
table.

BJ

Whatever you do,don't smoke near a car type wet cell battery and don't
drop a car type wet cell battery,,, they can and sometimes do explode!
You can find pictures on the internet or see batteries that have
exploded in scrap metal/junk yards.Not a pretty sight at all.
cuhulin

www.devilfinder.com Exploded auto batteries.

Some of those cell phone batteries have been known to explode too.Always
buy a new cell phone battery for your cell phone (if you have a cell
phone,I don't own one) at a cell phone store that sells the same brand
name and model number of the required battery for your cell phone.
cuhulin

www.devilfinder.com Optima car batteries

If you plan on using a car type battery in your home,an Optima battery
might be best.Especially if an Optima battery will last much longer than
a regular wet cell car type battery.
cuhulin