Powerchair battery charger with fuse

[martin007]

Hello.


Old mobility battery chargers have a fuse to protect the current input.

New chargers don't have that input fuse.

imagen_2021-02-01_230834.png (51.24 KiB) Viewed 1607 times

Advantages and disadvantages.
Opinions about it.

[Burgerman]

There are all kinds of ways to protect electronics. The chargers can be reverse polarity, over current and short circuit protected internally without a fuse. This is the wheelchair side.

The AC side does not need a fuse in the UK as theres one in every AC plug. But even if not visible there may be one internally.

So advantages, disadvantages? Not sure. As long as its been thought through carefully its safe.

[martin007]

The AC side does not need a fuse in the UK as theres one in every AC plug. But even if not visible there may be one internally.

In Spain it isn't so.

[Burgerman]

If its sold in spain and no fuse in plug there will be one internally. It may look like an electrical component soldered to the board, or fusable link, or a glass fuse. It has to have some means of protection to conform to the CE markings. Legally. Unless its chinese ad they dont care!

[Burgerman]

Take a look at these 2 pictures. BOTH are of fuses. May not be obvious.

[martin007]

I mean replaceable fuses.

[Burgerman]

Well they may use these instead. Both work. The internal ones are not replacable unless you know how to work a soldering iron.

dEPENDING on who designes it internal fuses can be better. There are automatic resettable ones. So they break the circuit when too many Amps. They reset themselves. https://www.littelfuse.com/products/pol ... -ptcs.aspx

[ex-Gooserider]

Worth noting that if something blows on the mains side with a modern switching type charger, the charger is almost certainly toast... The DC output side has the protection on it that limits how much can be drawn by the AC side. So short the output and the DC protection will limit the drain on the entire unit.... Only way to get excess draw on the AC side is for something in the switching circuitry to die. (nothing like that "magic smoke" aroma...)

Since we don't have schematics, a non-replaceable fuse isn't a problem as the rest of the unit is ready to be binned anyway.

ex-Gooserider

[martin007]

Worth noting that if something blows on the mains side with a modern switching type charger, the charger is almost certainly toast... The DC output side has the protection on it that limits how much can be drawn by the AC side. So short the output and the DC protection will limit the drain on the entire unit.... Only way to get excess draw on the AC side is for something in the switching circuitry to die. (nothing like that "magic smoke" aroma...)

Since we don't have schematics, a non-replaceable fuse isn't a problem as the rest of the unit is ready to be binned anyway.

ex-Gooserider

Do you have any kind of extra protection for PSUs?

[Burgerman]

No.

[martin007]

The AC side does not need a fuse in the UK as theres one in every AC plug. But even if not visible there may be one internally.

This?

[Burgerman]

Yes.

[ex-Gooserider]

Worth noting that if something blows on the mains side with a modern switching type charger, the charger is almost certainly toast... The DC output side has the protection on it that limits how much can be drawn by the AC side. So short the output and the DC protection will limit the drain on the entire unit.... Only way to get excess draw on the AC side is for something in the switching circuitry to die. (nothing like that "magic smoke" aroma...)

Since we don't have schematics, a non-replaceable fuse isn't a problem as the rest of the unit is ready to be binned anyway.

ex-Gooserider

Do you have any kind of extra protection for PSUs?

Same thing applies to modern switching style PSU's, wall warts, etc... Remember that the typical 'mobility brick' charger is basically just a PSU with some added circuitry to give (supposedly, pretending they actually did it right) it the appropriate charge curve output when connected to a battery....

So the same basic thing applies, typically they will have some sort of protection on the DC output, either a fuse, or some sort of current limiting shutoff circuitry. Optional is a diode to prevent harm if hooking it up backwards... (often depends on the use case) This protects the AC side if everything is working right. The AC side will typically have either a component or circuit board trace very close to the input that will fail open if something in the supply itself fails... (generally it is considered bad to rely on popping the fuse / breaker on the mains, since the manufacturer has no knowledge / control over that.)

ex-Gooserider

[martin007]

Worth noting that if something blows on the mains side with a modern switching type charger, the charger is almost certainly toast... The DC output side has the protection on it that limits how much can be drawn by the AC side. So short the output and the DC protection will limit the drain on the entire unit.... Only way to get excess draw on the AC side is for something in the switching circuitry to die. (nothing like that "magic smoke" aroma...)

Since we don't have schematics, a non-replaceable fuse isn't a problem as the rest of the unit is ready to be binned anyway.

ex-Gooserider

Do you have any kind of extra protection for PSUs?

Same thing applies to modern switching style PSU's, wall warts, etc... Remember that the typical 'mobility brick' charger is basically just a PSU with some added circuitry to give (supposedly, pretending they actually did it right) it the appropriate charge curve output when connected to a battery....

So the same basic thing applies, typically they will have some sort of protection on the DC output, either a fuse, or some sort of current limiting shutoff circuitry. Optional is a diode to prevent harm if hooking it up backwards... (often depends on the use case) This protects the AC side if everything is working right. The AC side will typically have either a component or circuit board trace very close to the input that will fail open if something in the supply itself fails... (generally it is considered bad to rely on popping the fuse / breaker on the mains, since the manufacturer has no knowledge / control over that.)

ex-Gooserider

I understand.