Aaaargh! Yet another fried Crystallite controller

[rhubarb]

I'm running a KMX kart with a Puma Motor and two 28V LiPOs.

I'm using a 20" wheel (unlike Knoxies and others which use 24") and there's no pedals or chain.

I've been using Crystallite 20A / 48V controllers which have IRF 2807 FETS rated 75V / 82A. These have been failing fairly often!

I decided to upgrade to higher voltage controller, the large cased crystallite 20A 72V. I had a couple of these a while ago and they had 12 FETs.

I hoooked it up and tried it out. It worked fine at 56V, but when I couldn't help myself and hooked up a third LiPO (=84V) it went like a rocket out the driveway and 50 meters up the road and then went phut.

Cursing, I opened the case up to discover that the new controller has the same board as my lower voltage controllers, only the Capacitors are rated 200V and the FETs are FB4710's (rated 100V, 75A).

A pair of FETs were blown.

Help! Why am I blowing so many controllers, and what should I be doing if I want to run my KMX on 84V reliably?

Can I still get a crystallite controller with 12 FETs or have they gone for a cheaper spec?

thanks! Help me in my quest to join the 40mph club!

 

[Lowell]

I'm not sure what's up with your setup, but I'm currently running a 72x35 controller, modified with IRFB4110 FETs. Peak voltage off the charger is 115v, and I've run over 100 amps burst current and routinely use 60 amps continuous. Ebikes.ca has the 4110 FETs in stock and might be able to help you out with a bomb proof controller like mine.

As far as I know, I'm the only one that's pushed over 7000W out of these controllers.

 

[Ypedal]

How bout a Clyte motor !!!

I don't understand why it would make a difference, but it seems like the Puma motor users ( as much as they seem great by all reports ) are having alot of problems with the clyte controllers....

To anyone who has opened them up ( where's knoxie these days ) .. is there any way that the motors could spin backwards when you let off the throttle ? what i mean is when you coast/freewheel with the motors, does the motor axle Stop or keep spinning ?

 

[Jozzer]

I still dont have my wheel back to try the puma, but I'm half expecting it to fry the controller at high voltage now...
Do you need it to run at 84v? If you can get the top speed you with 2 packs, how about letting a few more amps through to give you better accelleration?

 

[Doctorbass]

Does anoyne ever fried a modified controller using the 4110?

Are they really bolletproof or bomb proof? like people say?

I still wait to receive mine

Doc

 

[rhubarb]

I don't think the motor could spin backwards... I've got a dismembered puma on my bench that I crapped out probably from too many handbrakies.

It looks to me like a circlip failed and things moved sideways along the axle, wrecking the freewheel mechanism.

Anyway when I've got a moment I'll take a set of photos so you can all see what's inside. Much more complicated than a crystallite and really hard to disassemble the first time!

 

[rhubarb]

with 20" wheel, 20A controller and 56volt lithium top speed was 45-50kmh.

It's never enough

(altho I'd prefer a kart that does 45 rather than one that doesn't go at all) :?

 

[Roy]

Googling around with "IRF 2807" I find a Hitachi spec page talking about thermal sensing automatic shutdown.
http://www.ortodoxism.ro/datasheets/HitachiSemiconductor/mXwuyrs.pdf

I have no idea if this Hitachi is a possible replacement. But I'm just wondering, would using FET's with built in protection be a good idea? Is it already done?

I currently run one of these controllers 20A, 48V Crystalyte and want to experiment at 60 V (1 more SLA). It seems like a crapshoot as to whether the controller will blow at 60v.

Roy in Santa Clara