Replacing fast blow fuse with PTC resettable...

[bigjoncoop]

Hello my fellow DiYer's,

Are there PTC resettable fuses that are fast acting?

I've found some PTC fuses that claim 0.1 second max time to trip which seems would be fast enough I'm assuming... Correct?

The fuse is on the output of a lithium battery RC charger. It's there for reverse polarity protection. I was looking to replace it with a resettable fuse if possible.

The stock fuse is a (Size 1206) SMD 30a fast blow / acting.

[T3sl4co1l]

Have to know the fusing rating of the protective element (antiparallel diode?).

You also need a PTC with low enough resistance to do the job, and high enough breaking capacity (peak current) to not destroy itself on a short-circuit battery.  These are not easy to come by; I don't know offhand, but there may not even be a combination that satisfies these constraints, as they all depend on each other to some extent.

Alternately, an electronic solution could be employed, basically a MOSFET, plus transient protection to ensure it handles hot-plugging.

Tim

[Geoff-AU]

A PTC needs to heat up, and this takes a lot of time.

You probably want a TBU.

[thm_w]

30A seems high for a stock fuse, what is the maximum charging current?