XT90 cap

All the others I've seen, don't actually stay on so I did one with some 'toothed' tabs that grip.
When you've charged your battery, simply pop this on and when you need the battery, remove it........ that way, you'll easily be able to see what batteries you've used :-)

Please note, I've found 2 sizes of XT90 - The bigger one makes for a very tight fitting and the other is very loose. For the tight fitting, the cap won't go on all the way so please don't force it!

Thanks to DanHanson for