Layman's question: Digital display of power supply supposed to show actual or target voltage?

Good point about the gassing. It sounds like the OP tried it out, too. I'm glad he didn't get hurt.

Maybe I'm a bit paranoid, but I'm glad my UPS has a metal case. Those auto quick starters seem to have a sturdy enough case. But what about those cell phone batts blowing up under charge. Scary.

If the "scooter" came with a recharger, a mfg replacement is the way to go.

Safety First.

--
Best Regards,
Mike

On 5 Mar 2005 15:58:02 -0800, snipped-for-privacy@yahoo.com (fancy nospam tunes) wroth:

You are completely missing the second vital measurement, current.

The lower powered supply is probably supplying a constant current of 3 amps when it is connected to the battery as long as its voltage control is set to something over the voltage that the battery is showing before it's connected. So the voltage supply is showing the battery's terminal voltage as it charges.

The higher powered supply is apparently producing enough current to raise the battery's terminal voltage instantaneously to the value you set with its voltage control.

The proper supply to use for battery charging is one with separate current AND voltage setting knobs. That way you can set the charging current AND the voltage at which the supply will stop delivering charging current.

Jim

This is a terrible way to recharge a "gel cell" battery. Buy a charger designed for gel cell batteries or one that has a setting for them.

There are recommendations about current output as a function of battery capacity, but I don't know what the exact rule of thumb is.

The way these chargers work (more or less) is that they charge at max current until the voltage reaches some threshold (maybe 14 or 14.5 ?), then they charge at a constant voltage for some period of time (several hours?), and after that they go down to a smaller float voltage (~13 or

13.5 ? ). I like gel cells, but they are (according to what I have read) somewhat less forgiving of high-voltage charging than liquid electrolyte batteries. There is some kind of a battery newsgroup, sci.chem.electrochem.battery, I think, and they might have additional insight over there. Read the faq before posting, of course.

I don't think anyone can tell you which is a more professional design based on the few facts you have provided. However, I would definitely get a dedicated charger, not a variable DC power supply.

For example, a quick search led me to the Xantrex Xpower 15. I'm not sure this is a good charger, but it says that it supports sealed gel electrolyte lead acid batteries, and it has three stage charging, (which is what I described above). It is for batteries in the 6 to 200 Ah range. Your battery probably falls in there somewhere. At least I doubt it is more than 200 Ah. ;-)

Best of luck, whatever you decide to do.

--Mac

Both supplies will attempt to maintain the constant set voltage at their output terminals up to the maximum current limit, at which point they will abandon voltage regulation and maintain a constant maximum current drive into the load. Obviously the 3 Amp unit hit this threshold at a voltage lower than setting, the 10 Amp did not hit its maximum current threshold and was able to supply the full voltage. This is not the best way to charge gel cells, it is a taper charge method, where despite the capacity of the power supply, charge current does taper to zero strongly as battery cell voltage reaches full charge. You will get something like 70% the number of charge cycles to battery failure this way as compared to a three-stage lead acid battery charger. It's your call.

There's no reason for the power supply to fail if you exercise it thoroughly during the warranty period to accumulate hours. The most common failure mode is end user abuse.