Originally Posted by mitiempo
As far as I know it is not resistance that is needed, but voltage. If the charger
sees zero voltage it remains inactive. By paralleling another battery
you are providing that needed voltage.
I fail to see why an Optima or any other lead acid battery
would be different as far as charging
one with zero voltage is concerned - regardless of which form the acid is in.
According to Optima; their AGM
(Absorbed Glass Mat) batteries have a very low internal resistance which partly accounts for their good performance. So when they are "flat" there is an open circuit. I.E. no current
can flow through the battery. A flooded cell battery has a higher internal resistance so even if it's "flat" current
can still flow. The battery that was completely discharged in my car is actually an Exide AGM
. With the Exide I still needed to use another battery in parallel to start the charge process. If you do a google
search you will find out more.
I have been very pleased with my 3 Optima AGM batteries in my boat and Exide AGM in my car. I also have another smaller Chinese AGM on a separate circuit with solar
only charge for my boat instruments. This is to avoid voltage spike damage from the inverter
fridge, and alternator
in the house battery circuit. I previously had trouble but that's too long a story.
Getting back to the original question about gel batteries. I previously had expensive German gel batteries in my boat (can't remember their make at the moment). They only lasted 2 or 3 years. Since then I discovered that gel don't like being overcharged. I did not have a separate regulator
then, just the standard regulated Hitachi alternator
output. I now suspect that the alternator voltage regulator
needed a lower setting then for my gel batteries. Maybe 13 / 13.5 v instead of 13.8 / 14 v??
I now have a Next Step, (made in Seattle) smart regulator for my boat AGMs which as I earlier mentioned are 12 plus years still going strong except the start battery that I have just replaced after about 11 years. That's my experience anyway. I'm not suggesting one type of battery is better than another, just that each needs correct charging