Your understanding of batteries needs some help. There are many good
battery tech web sites, some at manufacturer's web sites (trojanbattery,
for instance), and some just out there, not associated with any
manufacturer. I would suggest you might spend some time on
http://www.uuhome.de/william.darden/carfaq4.htm
http://www.batterystuff.com/tutorial_battery.html
http://www.batteryfaq.org/
One of the first things these sites tell us is that "A fully charged
sealed VRLA Gel Cell or AGM battery ... has a terminal voltage from
12.85 to 13.1 VDC. An open circuit terminal voltage of 12.8 volts
represents complete discharge."
So your initial assumption that 11.4 volts represents almost a full
charge is exactly wrong. It represents complete discharge.
Re charging of gel cells, these sites tell you that "This is probably
the most sensitive cell in terms of adverse reactions to over-voltage
charging....If the incorrect battery charger is used on a Gel Cell,
battery poor performance and premature failure is certain." I would NOT
use a cheap garage-style 10amp/2amp charger on a gel cell. These
chargers are made for occasional use on flooded batteries.
Bounceback, which you described, is more properly known as "surface
charge". A battery is a series of lead plates immersed in an electrolyte
(acid). When you charge a battery, the concentration of electrolyte
(specific gravity) increases; when you discharge it, the concentration
decreases. This effect does not happen evenly throughout the battery -
the electrolyte that is directly in contact with the plate changes
first, so that there is a thin layer of high-concentration acid against
the plates. This is "surface charge". Then, as the battery sits and
rests, the electrolyte slowly mixes and the concentration evens out. As
a result, if you charge a battery, then take the charger off and
immediately measure the voltage, it will be artificially high, and will
slowly drop to the proper reading over the next half hour or so.
Similarly, if you discharge a battery, then measure the terminal
voltage, it will be artificially low, and then will gradually rise.
This process is slower in gel batteries than in flooded batteries,
because the electrolyte doesn't mix quite as fast.
What did you determine the amp-hour rating of the battery to be? More
particularly, what is the suggested discharge rate for the battery? Two
of the applications you mentioned (small boat, lawn-mower) are not
particularly similar to the way you are using it. A trolling motor on a
small boat draws a relatively small but long-term current. In the lawn
mower, the battery simply puts out of short jolt to the starting motor
to get the gas engine running. Then there is no further discharge.
Hope this helps
Bill
-------------------
rutman wrote:
Hello.
To being with, please accept my apologies for the noobie questions I
am about to make.
Heres the info.
1. Two small electrical motors rated 12volts 230 watts powers a
Peg-Perego electrical jeep. it looks like one of them power wheels
ride on toys. Since the original battery died, I started asking
questions and reading previous usenet posts as to replacing the
expensive power wheels battery for an ordinary car battery.
I received quite a few replies. Some were cons others pros regarding
the car battery adaptation idea. Apparently this has been done
sucessfully before my many people. Some replies were concern as to the
safety etc. Following advice from this group as well as having read
meny hours of googles 
, I decided to install a new heavy duty deep
cycle GEL battery. It cost me almost triple as much as buying a
regular 12vs car battery. However, from my own personal research as
other people advices as well, it looks like this was the way to go.
I also bought an inline 40a fuse and installed it on the positive
cable.
My kid took out the jeep for a ride, and he was having a blast,
until..... the jeep started slowing down. WAYYY down.. almost to a
crawl. This is odd, i told myself.. it surely did not seem like the
so called deep cycle battery lasted any longer that the orginal small
power wheel jeep battery! we are talking like 40 minutes of play time
with my kid going around for a ride or two.
So I popped the hood. Checked all the cables. The positive and
negative cable were warm but not Hot.. good sign I guess. I touched
the battery just to get a touchy feeling.. cold.. I went under the
vehicle and touched both motors. I was thinking that maybe the motors
were over heating or something as that, which might caused the jeep to
crawl. They were warm , not hot at all.
Took out my volt meter. Checked the battery for power.
It was reading at 11.40 volts!. thats almost a full charge.!
now heres the really odd part.
left the jeep sitting there for about 40 minutes while i went to a
local canadian tire to purchase a battery charger ( I didnt have one,
and since I just bought this deep cycle.. arghh.. more money )
came back. I was unpacking the goodies and noticed that my son had
already jumped back onto the truck and he was doing some wheelies! all
of sudden the power came back for about 5 minutes before dropping to a
crawl again. Check the battery's voltage. It was reading at 11.20
volts. Had my son drive the jeep until it wouldnt move anymore to see
how fast the deep cycle battery drained.. when the jeep coulnt move
anymore and I connected the volt meter, it read at 10.20 volts.
now here are my questions.
If the battery is reading at 11.40 volts ( almost a full charge ) why
are the motors turning sooo slow.
I know that the motors are rated at 12v 230 watts.. so if the battery
drops below 11 volts should this caused the motors to simply quit
turning the wheel?
I didnt check for the battery Ah rating. I took it for granted that a
deep cycle battery meant for a small boat, rideon lawn mover , or even
a small vehicle should be enough to put out enough juice to run two
12v motors rated at 230watts... but maybe i am wrong?
the original batteries the jeep uses are 12v 10Ah....
Could it be that the deep cycle battery may be defective? could this
explain the drop of power being supplied to the motors?
Finally.
whats the best setting to charge the deep cycle battery? My charger
has a setting for 10a and 2a. I am currently using 2a setting. (
trickle charge )