is a battery of
cells. A group of them. Smaller batteries that make "12" volts from six "2.2" volt cells are conveniently packaged in one case. Larger batteries, like those on fork lifts, have rather large individual cells that can be individually replaced if need be. So can the voltage of your battery
be increased? Sure, add cell(s).
But if you've got a conventional battery, all in one case? Time to ante up and replace it. Screwing around with kludge jobs will be an ultimate waste of time and money
. And the concept
of adding a resistor in order to increase voltage, if I may be blunt, says that you really might want to have an electrician check over the entire system when you do that. Resistors never increase voltage, they only lower it. Chosen improperly (wrong wattage rating) they can be good heating
elements, and start a fire. Or explode like a blown fuse.
A "car" battery can put out over 3000 amps into a dead short. If that short is through your wedding ring, metal watchband, wrench in hand...you can get seriously injured. Which is why I suggest an electrician, to do things now, until you check out some books
on 12-volt systems and come up to speed on them.
Low battery voltage can be from a bad battery, but it can also be a good battery being measured incorrectly, not at the terminals but somewhere else like a panel meter, which allows for bad connections, thin wiring
, and other problems that show "low" voltage in the system, when the battery is OK.
Better to have a pro come in and check out the entire system, so it works properly and
so you're safe with it.