RE: glow starter
Tim:
To the best of my knowledge, all cells that develop 2 volts nominal open circuit, are lead acid cells.
Whether a liquid electrolyte or a "Gel" cell, they are all rechargeable.
"Officially," they are 2.2v per cell, an automotive lead acid battery being a 13.2v battery even though normally referred to as 12v.
When fresh off the charger the lead acid cells can show up to 2.5v per cell, this surface charge will disappear quickly under a light load, and you'll see the 2,2v per cell. This will then drop slowly as the charge is exhausted. They are useale down to roughly 1.8v per cell.
Any single lead acid cell, if high enough current capacity, can be used to light any glow plug. If you select the "Right" cell, it will be safe on either a 1.5v or 2v plug, as the internal cell resistance will limit the current, the plug wont blow from overvoltage.
A safer method, rather than a series resistor or a switchable voltage regulator, is a current limiter. If the circuit is set for a maximum of 4 amps it will then be safe for any plug, and you wont have to worry about picking the "Right" cell. Most power panels are current limiting devices.
The Radio South glow starter uses four NiCd cells with a current limiting circuit.
A single NiCd cell, being 1.2 or 1.25 v/cell, often wont work on the 2v plugs, as you have found.
Carbon/manganese or alkaline cells, flashlight batteries, will work for either, again observing the current capacity. A single "Dry cell," the big cell that weighs a pound and a half, works fine but it is too expensive these days. Two "D" cels parallelled work fine. A local friend uses four "AA" cells in parallel, he gets good life and it's not too expensive.
Charging lead acid is simple if you have a liquid electrolyte in yours. Do not add any water unless the levwel is below the plates, until it's charged. If it's low, add water just to cover the plates. So long as you don't overheat it, just about any charging current works. Just watch the cell, if it starts gassing off (bubbling) lower the charge rate. When it gasses at a low rate, 2A or so, let it bubble far 15 or 20 more minutes, it's fully charged. As the battery charges the electrolyte level will rise. Top the cells after it's charged, not when its charge is low.
A gel cell has no visible indication of charge level, and voltage is not a good indicator. A gel cell will gas at full charge too, but you can't see it. And if left on charge you will dry it out, and ruin it. Use your 500ma charger, leave it on overnight, and see how the charge lasts. If it's dead too soon, increase the charge time, if it lasts for your full flying session, decrease the charge time. Generally speaking, you can leave a gel cell on a 50ma rate indefinitely.
Which brings us to "My Way" of charging gel cells. After flying, they go on a trickle, and stay there until the next weekend. I'm running 50ma, my power panel battery is still going, it's about seven years old now.
If you "Cook" a starter type gel cell, often the top can be pried off exposing the cell caps. Opening the cells, and taking a few hours to do it, you can add water until the white felt looking separators are once again looking damp. This will take a while, you'll add water and they will look wet, look again 20 minutes later, they're dry again. When they stay wet for a half hour or so, add just a little more water, so the cells look like there's just a little excess water. Now put the battery on slow charge, and so long as the caps are off you will be able to see it gassing. Provided you got enough water in it. About seven times out of ten, you can rejuvenate a gel cell this way. Your failed starter battery? Give it a try. You might lose some time, but you might not need a new battery, either.
I've run on here, but hopefully there are some good ideas for you and others.
Bill.