Battery Care and Handling
For sealed lead acid electric scooter batteries.
Safety
Lead Acid batteries can give off explosive hydrogen gas while being charged. While most
scooter batteries are sealed, they can, in rare cases, still vent hydrogen, and therefore
care should be taken to avoid smoking, open flames, or sparks around a charging battery.
Always connect a charger to the battery before plugging it in.
While there is almost no danger of electric shock* from low voltage
batteries (under 40-50 volts), you can still receive a serious burn if wires from opposite
terminals come in contact with each other. I have seen a wire that accidentally came in
contact with both terminals of a 12 volt battery turn white hot and vaporize instantly
(don't try this at home, it can also cause the battery to explode)! If I had been holding
on to that wire, I probably would have been branded for life. So always take great care
not to allow the terminals to be shorted together.
Battery chargers have been known to occasionally malfunction and throw sparks or even flames.
It is therefore not recommended that you leave your battery charger plugged in and unattended.
Batteries contain poisonous lead, and corrosive acid. Do not attempt to open these
batteries, or allow your skin or clothing to come in contact with a damaged or leaking
battery.
Charging
Note: Always charge your battery(s) as soon as you are finished with your ride.
SLA (sealed lead-acid) batteries must not be allowed to remain in a discharged state.
While in a discharged state, sulfate compounds build up on the plates, effectively
insulating them from electrical/chemical interaction. While this sulfate compound builds
up slowly, it is permanent, and cannot be removed. The damage will be proportionate to the
length of time the battery remains in a discharged state. A battery that remains discharged
for a month or more will likely be completely ruined, but even a relatively short period of
time will cause some damage. Usually, this damage results in shorter riding times before the
batteries die, and in extreme cases, though the batteries appear fully charged, they will not
power the scooter at all. Often, attempting to charge a damaged battery will cause it to
overheat, and sometimes melt the case. Good battery chargers will not attempt to charge
batteries whose voltage has dropped below a certain point.
Never use any charger other than the one recommended by the manufacturer to charge
SLA batteries. These are specialty batteries and are sealed. Charging these batteries
at a higher than recommended rate can cause the battery to vent hydrogen, which will upset
the chemical balance in the battery, shortening its life. It can also overheat the battery,
cause the case to melt, and possibly cause an internal short. In extreme cases, the battery
can explode! Quality chargers for SLA batteries sense the voltage of the battery and
apply an appropriate level of charge. They also know when to stop charging, or switch
to a maintenance mode.
If the charger that came with your scooter is fully automatic (check the instructions that
came with the charger, or contact the manufacturer to be sure), you should be able to just
plug it in and just let it do its thing (see safety section). If you have any
doubts, you should check the batteries frequently to make sure they are not becoming too hot
at any time during the charging process. SLA batteries sometimes get warm while charging,
but if it is uncomfortable to hold your hand on the battery, you should unplug the charger
until the battery has cooled. If your charger is not fully automatic (or you are not sure),
you should watch the batteries closely, and make sure that they are never on the charger for
more than 8 hours. I recommend an inexpensive ($5-$10) appliance timer to ensure that the
charger is turned off at 8 hours (or less if the batteries are not
fully discharged**).
Storage
Lead-Acid batteries will slowly discharge on their own during storage. In order to prevent
damage, SLA batteries need to be charged periodically during long-term storage. Be sure
to charge them every month or two.
Testing the Batteries
You can use an inexpensive voltmeter to check the state of the battery's charge. If there
is more than one battery in your scooter, you must disconnect each one (make sure to note
which lead goes where, as you can damage the scooter if you hook them up incorrectly), and
test each battery individually. Just set the meter to measure 15 volts (or higher) DC, and
touch the red lead of the tester to the red or positive terminal (the one marked with a '+'
sign), and the black lead to the black or negative (marked with a minus sign) terminal of
the battery, and read the voltage on the 15 volt scale. You can use a higher scale if the
meter doesn't have a 15 volt scale. See the fully discharged**
section below for interpretation of readings.
This test will only tell you the state of charge of the batteries. It will not tell you
if the batteries have been damaged or not. That requires a 'load' tester. I have not been
able to find an appropriate load tester for these batteries on the market, and have been
forced to make my own. Automotive battery testers should only be used on SLA batteries of
17Ahs or larger. Even then, you should be careful not to apply an excessive load while
testing.
*Why can't I be shocked by a battery?
You've probably heard that it's not the volts that kill you, it's the amps, right? Well,
that's true, but you need the volts to generate the amps. There is a third piece to the
puzzle, and that is resistance. Resistance is provided by anything that does not easily
conduct electricity, like the plastic insulation around most electrical wires. The amount
of current (amps) that can flow depends on the voltage and the resistance. Voltage provides
the potential for current to flow, while resistance impedes that flow. Insulation has so
much resistance that it prevents current (amps) from flowing at all.
Your skin actually has a fair amount of resistance. You can place your fingers across a
nine volt (or twelve volt) battery and feel nothing at all, but put it on your tongue, and
it's a different story. If a surgeon were to place that same battery on a patient's exposed
heart during surgery, it would provide more than enough amps to stop the patient's heart.
On the flip side, if there is little or no resistance, like shorting battery terminals
together with something metal, a great deal of current can flow from even that nine volt
battery, which can generate a lot of heat. That principle is used for welding. A welder
that can weld one inch thick steel, will hardly give you a shock if you touch the electrodes
with your hands (not your tongue!).
Of course, if the potential (voltage) is high enough, like the 120 volts provided by household
outlets, it can easily overcome the resistance in the skin and can be very dangerous.
**Fully discharged means different things depending on
whether the batteries have been resting or were discharged while being used. If the scooter
has not been used for a long time, the batteries are fully discharged at 11.5 volts for 12
volt batteries. If the scooter has been ridden recently, the voltage can be as low as 7.5
volts before the batteries are fully discharged, but that would only be in the most extreme
usage scenario (and the battery would have to be recharged immediately to avoid damage). A
fully charged battery should read between 13.5 and 13.8 volts.
© 2002, MotorManMike Co. Seattle, WA.
|
