Running 72v controller on 24s lipo

I bought the dual voltage controller here http://www.ebay.co.uk/itm/48V-72V-1...r-/360643190249?ssPageName=ADME:X:RTQ:GB:1123 It can be switched between 48 and 72v. The problem is, my battery has a nominal voltage of 88.8v and comes off the charger at 96v. I only charge it to 4v per cell or sometimes less for maximum life and safety. What modifications would need to be made to the controller? Is it as simple as just changing all the mosfets and replacing the input capacitor and finding a 5v regulator that can take the higher voltage? I currently have the battery configured as 44.4v 44.4ah 1.972 Kilowatt hours for the controller I have which can do 30mph maximum. My current controller is a 9fet one using IRFB4110 and it does 42 amps no problem. I wouldn't want to put any more current through the motor though as I worry that I might rip the magnets off the inside.

Most 72V controllers use 100V caps and fets, so most will work fine with 24s lipo even charged to 100.8V. I've been running mine on 24s fully charged for 2.5 years. It has 100V caps and 15 100V 4410 fets. You could open yours up and check the caps and fets first, but they likely are both 100V rated. You might want to adjust the controller LVC if you can figure out how. I had to adjust my LVC to 84V to get regen to work. Asuming that switch on it is to change LVC from 42V to 63V, it should be easy to figure out how to change it.

wesnewell said:

Most 72V controllers use 100V caps and fets, so most will work fine with 24s lipo even charged to 100.8V. I've been running mine on 24s fully charged for 2.5 years. It has 100V caps and 15 100V 4410 fets. You could open yours up and check the caps and fets first, but they likely are both 100V rated. You might want to adjust the controller LVC if you can figure out how. I had to adjust my LVC to 84V to get regen to work. Asuming that switch on it is to change LVC from 42V to 63V, it should be easy to figure out how to change it.

Click to expand...

It is coming from China to the UK so I will have a look at it if and when it arrives. As for the regen on my current setup, it only works when I am going down hill at 25mph with a 37v battery or going faster than the battery voltage allows. I plan to implement a dc boost converter so regen will work at any speed. This will consist of a spdt relay switching between the boost converter or the controller as the controllers seem to act as bridge rectifiers. I get a voltage out them when I spin the wheel and can power stuff by pedaling the bike.

Generic chinese controllers tend to use shitty caps.

Caps are rate to + OR - 10%

So a 100v cap might be fine at 110 volts.

Or

It might blow at 90volts.

The Mighty Volt said:

Generic chinese controllers tend to use shitty caps.

Caps are rate to + OR - 10%

So a 100v cap might be fine at 110 volts.

Or

It might blow at 90volts.

Click to expand...

I will get some Panasonic capacitors and IRFB4110 mosfets if the controller seems easy to modify.

These 100v 4700uF ones will do! Nothing like a good spark as you connect up your battery.

According to Lyens, for his controllers other stuff can blow above 90v. The circuitry that provides 5v is designed to handle 90v or less. It won't blow right away in most cases, and may never blow in some cases.

FWIW, 22s will pretty much stay below that 90v. 24s, will drop below 90v pretty quick during the ride, especially when under load. Even quicker to drop below 90v if you charge 24s to 4.1v.

Again, that 90v is not a hard ceiling, but if you plan to run 24s, wouldn't a 100v + controller be worth the cost? Nothing wrong with having a spare 72v for when you blow your other one.

dogman dan said:

According to Lyens, for his controllers other stuff can blow above 90v. The circuitry that provides 5v is designed to handle 90v or less. It won't blow right away in most cases, and may never blow in some cases.

FWIW, 22s will pretty much stay below that 90v. 24s, will drop below 90v pretty quick during the ride, especially when under load. Even quicker to drop below 90v if you charge 24s to 4.1v.

Again, that 90v is not a hard ceiling, but if you plan to run 24s, wouldn't a 100v + controller be worth the cost? Nothing wrong with having a spare 72v for when you blow your other one.

Click to expand...

I suppose that would be a good idea. You can never have too many controllers lying around. They have an 84v controller that would suit me. If my bike does 30mph on 12s I would expect about 50mph on 24s which would be scary at first. If the controller I receive is a 12 fet, I could get 55 amps from it after changing fets.