Lead-Acid or Lithium-Ion

I'm having a kind of hard decision to make, I know lithium-ion is lighter & more powerful. Recently I blew 2 of the 5 batteries in my scooter-style electric bike. on 1 hand I have a tech saying to change to li-on I have to change motor, controller,& converter. Then on the other I have another tech at another shop saying that I don't have to change anything but the batteries. To make the switch do I have to run up a bill of almost $2000.00 if not more, or just 5 li-on batteries. Thanks for any help you can give.

You don't need to change anything. As a manager at a EV power company for more than 6 years, I can surely tell you that only need to replace batteries. If you are using 5 pcs 12V nominal SLA batteries in series. Then your scooter is a 60V scooter. You will need a LiFePo4 battery pack which is 20 cells in series.

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Your battery pack should probably a 60V12Ah one. The 60V12Ah headway LiFePO4 here is about 441USD.