New Li-ion Battery Charger - 3 contacts on battery?

[Speakercon]

If anyone is interested I decided to risk a tenner and purchase one, and I have taken these pics of inside the charger. Any thoughts?

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[bernardgreen]

The obvious is that the third battery terminal is not connected so no temperature compensation of charging current is possible. Which means it will keep charging an overheating battery.

Nice and obviously marked separation between mains side and ELV side. It could be a bit wider though. If there is weak point it would that transformer.

One can only assume the resistor connected to the mains is a fusible device designed to fail open circuit and not one that could char into a low resistance which would be a fire risk.

 

[Speakercon]

Thanks for the information Bernard. Very interesting. My main worry was the circuit failing and 240V going into the battery.

I did notice that the middle contact was not connected which was worrying, there is an led on the charger that goes from red to green when charging is complete but that must just be an indicator and the battery is still being over charged.

I don't feel very happy using it tbh, and its worrying considering how many are being sold on eBay and amazon uk.

 

[bernardgreen]

The chances of 230 volts appearing across the battery terminals is zero. But the terminals are capacitively coupled to some point with a potential somewhere between Neutral and Live voltage as there is no earth. Not a hazard if someone touches the charger contacts as the current that could flow through the capacity would be very small.

The capacity is between the windings in the transformer. If the insulation between windings broke down then the battery terminals could both become live.

I would prefer to see a toroidal there with the windings separate from each other so there was ( virtually ) no risk of the windings shorting to each other.

 

[Speakercon]

Thanks for your advise, seems they are not as bad as I thought but still they're not brilliantly safe!

 

[JohnW2]

Thanks for your advise, seems they are not as bad as I thought but still they're not brilliantly safe!

To be honest, on the basis (only) of the pics you've showed us, I don't think that (other than the lack of temperature compensation) we've see anything which leads us to believe that it is necessarily any less safe than anything else you could/would find.

Kind Regards, John