48V MOTOR KITS MAX VOLTAGES

I HAVE 18V MILWAUKEE BATTS., AND WOULD LIKE TO USE 3 OF THEM. SINCE THEY PUT OUT OVER 20V BEFORE I LOAD THEM UP THE PACK WILL PUT OUT OVER 60V, WILL THE CHEAP 48V HUB MOTOR KIT HANDLE THIS?

Yes, most "48V" controllers of these cheap hub motor kits will tolerate up to 63V max.
Do you have a link to the kit you're looking at? And do you know what the max. continuous amp rating of these batteries is? As a "48V 1000W" hub motor kit will need 20A continuous and some will take up to 40A (some even more) peak from the battery. You'll probably need many more than just 3 of them...

My 48V, 1000w handles 52V with no difficulty, and it's been reported most (if not all) are good to 63V.

21V for each is the maximum charge. If you had 4, it would be better to put the other 2 in parallel.
It doesn't matter as far as distance goes if you put 4 in series, or ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Just your speed varies, and your controller internals would have 63V capacitors.
Grab one more tool pack battery!

You'll be fine many people have run over 100V. Ultimately the insulation should be good to a few hundred volts without any shorts.

I agree with the above posts. The kit should be fine eith that voltage. you might find that the controller won't go right off he charger but does after a few minutes as the voltage settles down. I am assuming they are 5s, so 15s is a little high for a stock controller, when fully charged.

What is the AH rating of the packs? You will see maybe 1.5 miles per AH if you ride it half throttle, maybe more but less if WOT. You should be running like 9 packs in 3series and 3 in parallel. One pack will power it but will not last very far and will heat up fast due to the high amp draw.

Dan