Well I have a Makita vac that's 7.2V and have been running it on 9.6V
going on 7 years now. It rocks. The end of the pack is identical and
the salesman that sold it to me showed me the battery switch. The only
thing that has happened is that the impeller needed replacement last
year. That cost about $7. The Makita batteries have built in thermal
protection.
Richard