Overvolting a Giant Lafree

[tangent]

I am sure there must be people who have tried this. How much overvolting can a Giant Lafree take?

 

[flecc]

I don't know of anyone ever doing this, and I've been running the Lafree support website for years now and have many communications from all over the world on a wide variety of Lafree issues.

I'd advise against it, nothing to do with what the motor can take but much to do with the computer-like mainboard with it's CPU and other ICs. Those integrated circuits are designed to run with 5 volts and overvolting the system will overvolt them with probable damage. As it is the mainboard has suffered a number of failures and it's the main source of trouble necessitating a new unit or scrapping, well ahead of any other factor. Circuit board below:

 

[tangent]

Thanks, I thought that the circuit board would probably be the limiting factor. There must be a voltage regulator in there somewhere that reduces the supply to 5V, but it will clearly have it's limits. I would have thought the higher voltage components (e.g. capacitors) would probably be 35V ones, so only moderate overvolting would be possible.

My fully charged NIMH battery seems to be around 29V. This does not seem much of a problem and the bike is very perky at this level for the first few hundred yards, hence my interest. I am considering getting a LIPO or LiFePO4 battery. These are now becoming more reasonably priced and readily available. I am debating whether going for a 9 cell LiFePO4 or 8 cell LIPO, instead of 8/7 would be pushing things a bit too much.

 

[flecc]

The extra couple of volts on standard lithium batteries should be ok, but pushing that to around five to six volts over NiMh might be pushing it too far. Peak charged voltage of an 8 cell li-poly could be nearly 35 volts, a bit much for a nominal 24 volt system

It might work, but the risk of subsequent failure must be increased considerably, especially as that circuit board has been their main weakness in the past.
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