electricvehicles wrote:They are sealed for a purpose --- To stop tinkering fingers tinkering with them. Thats why the only way into them other than Curtis is via the programmer. Just leave them as they are !!! They work fine and exceed their specifications.
If you tinker with a combustion engine to get a bit more, as we all know you will you will reduce its life, same with a Curtis
I've modified many production engines, often for power, sometimes for economy (not always exclusive), but often to correct well known life limiting design defects that were not adressed during the production life of the engine. Triumph straight six engines for example, where the oil drains out of the filter when parked, so they're always oil starved when started cold.
Curtis pioneered transistor based controllers, first with bipolars and later with Mosfets.
THERY' RE GOOD CONTROLLERS and I've used them several times with sucess.
But they have their limitations and in our applications, which despite your opinion, really ARE often harder on controllers. Forklifts don't often climb a hills for several minutes at 50% PWM duty. They're not typically driven in traffic and so don't missjudge a gap and have to acclerate very quickly.
Several people have taken them apart after their second or third controller (whose application was recommended by a Curtis engineer) has failed. They've usually then decided they need to use another product.
Curtis controllers fail often enough, even in ordinary golf car applications, that there are several specialist firms offering a repair, exchange or outright purchase service for them in the US. They upgrade them becuase there are OEM only components inside and also because better components have been developed and are often cheaper.
The 12xx series have rather too many mosfets in parallel, are rather short on freewhweel diode current capacity, don't have high frequency filter capacitors, don't have a linear overheat shutdown, have taken an 'easy' approach to EMC compatability (increased switching losses), and have a slow current limiting scheme that causes failed controllers when driving low impeadance motors. The latter by the was is why Curtis introduced the 1221 and 1231C series controllers where the frequency is reduces to 1.5KHz below 10% PWM.
They were pretty much state of the art when introduced, but time marches on. Judging by the current ratings and on state resistance the uProcessor logic versions of the 12xx series are using the old power stages (But why do they no longer list the 1 hour current rating?).
The Americans went through the golf car/forklift components phase about 15 years ago. Here it's taken rather longer. When I first joined the BVS some 10 years ago, many people didn't trust electronic controllers at all!
Many of us ARE tinkerers and we DO push the technology.
Edited by ChrisB to remove certain comments that are non constructive