Non-RC - 18V Battery into 12V kids Quad

[4stroker]

Hi guys this isn't RC related but was hoping someone may be able to give me some advice here.

My brother and I are looking to "hop-up" our kids little 12V ride on quads by putting our Makita 18V batteries in them.

There are loads of videos on the net where people just throw the battery in there and call it day, and apparently have no problems.

I want to be a little more scientific however, and make sure A: my kid isn't riding a death trap! and B: we don't kill our $100+ batteries.

Attached are some pics of the battery and charger, and of one of the quads in question.

My questions are:

1. Should I add a low voltage alarm, and what should I set it to?

2. Should I add a thermal switch/fuse?  If so how do I work out what switch/fuse to get?

Any other advice greatly appreciated!

[Nobbi1977]

I am not 100% but I think the lox voltage protection is built in the the batteries not the tools so you should be ok with that.