|Questions on charging 12volt sealed
lead acid batteries
I have just had to replace my 12volt 7-amp hour sealed lead acid
battery that is installed in my flight box and is used, via the power
panel, to power my starter; it also has outputs for a glow starter. The
reason for replacement was that, despite having charged the battery up,
it would only turn the starter over for a few moments before the power
faded to a point where there was insufficient power to turn the engine
over against compression and the starter just ground to a halt.
I use a Simprop
Multicharger for charging the 12 volt battery, using
the nominal 500mA output which, according to the manual, has a maximum
true output of 317 mA when charging a battery of 12V/10 cells. As far as
I can determine, of those available on
the charger (the others being nominal outputs of 50, 60, 140 and 180 mA),
this is the correct output to use for the lead acid battery
I do not know if the failure of my old battery is down to anything I
have been up to - I usually put it on charge for 12 - 16 hours when the
needle on the dial of my power panel gets down to about half way, and it
has performed all right for normal use over the last three years.
Can anyone help, please, with answers to several questions as I start
to use the new battery (with which there were absolutely no
- Is it likely the old battery has failed simply because of its age
and use to date?
- What is the correct procedure to follow before I use the new
battery? Do I give it a full 16-hour charge as usually recommended
for new nicads, or is it a different requirement for a lead acid
- What on-going charging procedure should I follow?
The Simprop manual states, "Lead-acid batteries should only
be charged at the nominal charging current when using constant current. [What
does that mean?]. The charging time should be kept to absolutely. Too
long a charging time leads to gassing the battery! The charge
still in the battery at the start of charging must at all events be
taken into account when calculating the charging time.
"For example: a battery has a charge of 30% remaining =>
the charging time is reduced by 30%. If overcharging occurs the
electrolyte of the battery dries out. With older type car batteries the
loss of electrolyte can, as a rule, be made up by distilled water. With
maintenance free lead batteries this is no longer possible. Gassing is
to be avoided at all costs, not only as dangerous gases are released but
also because the lifetime and capacity of the battery are substantially
- If I am to follow those instructions for recharging, how can I
determine what percentage of charge is remaining before proceeding?
- Is there any way to determine that the full charge has been
reachedor is it a question of timing?
Any advice - in simple language for one who just can't seem to grasp
this subject - will be very welcome.