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Why does 0-30v power supply "lock down" to 25.4v max when charging scooter?

This is a question about a Mas Tech power supply (which looks like most of the inexpensive single-output power supplies from China these days) and its shutdown circuit: When I connect to a 33AH disability scooter battery pack with approx. 25.2v the Mas Tech won't dial higher than 25.4v until the supply has had about 5+ hours of non-use.

The lock-down is immediate, but I sometimes, the supply works, and I'm able to charge the battery pack.

Doesn't seem to make any difference if I connect the load first, then turn it on, or vice versa. It is very baffling.

This is a new model, with auto-switching 115v-230v AC, no fuses from the outside.

All suggestions appreciated.

FYI it seems to be well protected from reverse polarity -- didn't get damaged from reverse currect high enough to weld connectors!

Reply to
Denny
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Could be an over-current protection circuit kicking in.

Reply to
Charles Schuler

Not at all clear what you mean by "lock-down" The supply can't go any higher in voltage than the battery will let it. What's the current in this mode? If it's hard limit, it should be the max limit of the supply. If it's foldback limit, it could be anything.

Again not clear...did you mean that you connected it in reverse across the battery. IF so, you may well have damaged it.

mike

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Reply to
mike

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