SLA batttery delivering high current

[frank9755]

I'm a bit mystified!

Does anyone know if it is possible for an SLA battery to start spontaneously supplying high currents without them being demanded by an attached device?

I bought a 36v charger for the SLA which I have been using as a test battery. On connecting the charger to my battery it immediately went 'pop', gave out a puff of smoke and started pulsing. As an extra test I first put a low fuse (5A) in my battery and connected it to my Wisper bike. The fuse blew immediately, despite there being no load and (I presume) no demand from the Wisper controller.

This battery had worked ok with my Tongxin motor but after a short while the Tongxin controller packed up, with the battery fuse blown. I put it down at the time to the controller demanding too much current but I'm beginning to suspect that it was my battery which caused that problem.

Has anyone come across batteries behaving in this way?

Frank

 

[flecc]

The only thing I can think of is a battery internal short circuit Frank.

That would allow excess current with the charger connected, blowing the fuse.

The only way that I can think of for the bike to reproduce a fuse blowing with such a battery condition is if a controller electrolytic capacitor discharged through the battery, though it seems very unlikely.
.

 

[frank9755]

Thanks Flecc,

As you say it seems odd. I don't think I'll risk using that battery again!

 

[giguana]

if there is a short circuit inside the battery it will overheat a lot and then will go flat, and it will probably be a different voltage from normal, in fact if you put it in a large glass container in case the sulphuric acid comes out it might be a good idea.

how do you mean the fuse blew up all by itself? when the wire of the fuse was not attached to anything? Maybe there is a short-circuit after the fuse? if the wire it's on is attached to something.

 

[frank9755]

It only blows fuses when it is connected to something. Indeed when it is connected to something it always blows a fuse.

Thinking about it, it is behaving as if the thing it is connected to (ie bike controller or charger) is completing a short circuit, or if the connectors short when they are connected to something. While the latter sounds like the most obvious explanation, I'm sure this is not happening. The connectors are powerpoles and I'm confident they are wired properly - but I will check again!

Thanks for the thought-provoking question!

Frank