Tricking a cheap ESC

[KAE]

I have a rather cheap but very fun ebike, made in China that I have been riding for a while now. It came with a 48V Lead Acid battery pack that has become spongy and worn down. I have a wonderful and very well-made 36V Lithium Iron Phosphate pack that would work great with this bike. The problem is it has an ESC that is preset for a 48V setup with a low voltage cutoff that won't let the bike run on the 36V pack. Its a cheap ESC so its not programmable or re-configurable or any of that. My question is: Is there a way to trick the ESC into seeing 48V for the purposes of tricking the LVC so it doesn't trigger? Or possibly a way to bypass it somehow? The ESC does have a lot of important functions so I don't want to bypass it completely (for example it has sensors that cut off the power to the motor when the brakes are applied, etc. etc.), but I would like to fool it into seeing a 48V pack. Is there a way to "boost" the voltage by 12V or 14.4 or whatever it should be to avoid triggering the LVC, without adding more LiFePO cells????

 

[texaspyro]

It should be trivial to modify the voltage divider that cuts the battery voltage down to a level that the micro can measure... but what is not going to be trivial is finding which (usually pair of) resistors form that voltage divider. There should be two resistors connected in series between the battery input and ground. The junction of the two resistors should go to an analog input pin on the micro or perhaps a voltage comparator or op-amp chip.

Changing the voltage divider may also affect other aspects of the ESC performance...