My 18volt Ryobi battery needs the inside batteries replaced. Is there a cheap way to do it? Can I buy just the inside batteries for my 18 Volt?

you dont

you can but it will take longer to charge and prob will be at 16 volts give or take 1 volt.

you don't.. just replace all the 18volt system with this..( I did,,and YES!! GREAT!)
http://www.homedepot.com/p/DEWALT-20-Volt-MAX-Battery-Adapter-Kit-for-18-Volt-Tools-DCA2203C/206526033

After looking at the manual for your charger, it looks like most of the Ryobi chargers like the P113, P114, P117, P118 will charge your battery. The connector on the battery looks the same as the P103 and P104 used here in the U.S.

Yes. Dewalt says the 18volt XRP battery is compatible with all Dewalt 18volt tools

Have a great day.

Hello Tom, Here's a link to the Ryobi US web site with a free downloadable copy of the manuals for bothe the Ryobi electric chainsaw and a copy of the manual for the 18 Volt Battery versions

Electric Chainsaw
http://www.ryobitools.com/product_manual/file_url/252/RY43006_640_eng.pdf

18Volt Battery Chainsaw
http://www.ryobitools.com/product_manual/file_url/254/P540_P540A_P540B_eng.pdf

I included both, just in case you have a corded version too, since sometimes the Fixya site provides "fill in" information for askers.

I hope you find this Very Helpful and best regards!

Yes you can, as long as the batteries are the same style and fit the older Ryobi tools. The Ah rating is a capacity rating. The higher the Ah, the longer the battery will last so the 1.7Ah will just last a bit longer than the 1.5Ah batteries, but yes you can use them on older 18v Ryobi tools. I do it all the time.

If the drill has a short in it, then yes, it could short the battery out. Probably in the trigger switch.

the newer type of battery had an electronic inside only. older style battery had sensor only.

I have two 18volt chargers doing the same thing. I have had them apart and it seems to be the transformer not pushing any power thru. If you can find a transformer that fits and has the right voltage that should fix the problem. From what I can make out if you leave the battery in for too long on charge it cooks the transformer. Hope this helps