I bought a charger for my Nexus 5 but heard they start 'discharging' the phone once it's fully charged?!

I don't understand them really. Can they damage your phone?

Thanks

Is it not the same as a normal charger? What i mean is i thought after it charged to 100% it then discharged to 90% before charging again to 100% etc.

My HTC Desire used to do this, if i left it on charge overnight it could be anywhere between 90-100% when i unplugged it.

It is wise to have the 90% thing.

If you only ever charged to 90% then the battery would likely stay in good condition 2 to 3 times longer. Its the squeezing to 100% that does damage to a battery.

Yes, this is all chargers, not just wireless. I've been charging my nexus 4 wirelessly without any noticeable problems for 18 months.

In a good system that final 10% is via 'trickle charge' so maybe the problem with wireless is it is 'all or nothing'.

If so, are they bad for the battery when going to 100%?
I have no idea on the actual truth here but it is a thought.

My Nexus 5 is always at 100% charged when i take it off the wireless charger, as for any damage thats down to heat but mine is cooler charging wirelessly in the UK than what it was just walking around in Portugal so i guess the impact is relative to where you live.

Yep, mine too, and ditto the normal charger for that matter. I did once have a phone (either my Nexus 4 or my Galaxy Nexus, I forget now) which used to come off anywhere between 90% and 100%, which was annoying as it didn't have the greatest battery life at the best of times, let alone when you'd lost 10% before the day'd begun. I don't know if this was the charger's doing or the phone's.
Haha, I'd never thought about it like that but that's a very interesting point!