Navita Controller

[teecro]

What's the scoop on Navita Controller's? Neighbor had A 500 amp one put in his cart and it's not performing as it should . It's still got some crappy cables but I'm not sure if that's his only issues.

[cgtech]

Can't expect any performance with junk cables. Imagine running a foot race while breathing through a drinking straw.

[teecro]

Originally Posted by cgtech

Can't expect any performance with junk cables. Imagine running a foot race while breathing through a drinking straw.

Thanks, that was one of my most repeated comments to my friend was that the cables sold to him were junk as far as carts were concerned and barely acceptable in the automotive field. Told him to question the shops use of such low quality cables and why install a 250 amp main fuse on a 500 amp controller...

[cgtech]

The 250a fuse may not be the problem you think it is. I usually see "slow reacting fuses" on golf carts. Here's one example of the characteristics of a 200a slow reaction fuse. You may be shocked.

First column is amps required to melt, second column is time to melt.

6000a - 0.01s
2500a - 1.0s
1700a - 2.0s
1000a - 10.0s
450a - 100s
350a - 200s
250a- 1000s
200a - forever

As you can see, given the typical usage characteristics of even a high performance golf cart, even this little 200a fuse would likely never blow, even with as big of a golf cart controller you might find.

[teecro]

Agian thanks, learning this as I go. Was just hard for me as my only GC experience is with my CC and my 500 amp Curtis controller has no mention of main fuses. I'm thinking his biggest issue is cables as its a mix of low quality 4 gauge and some 6 gauge cables too...

[JohnnieB]

Originally Posted by cgtech

The 250a fuse may not be the problem you think it is. I usually see "slow reacting fuses" on golf carts. Here's one example of the characteristics of a 200a slow reaction fuse. You may be shocked.

First column is amps required to melt, second column is time to melt.

6000a - 0.01s
2500a - 1.0s
1700a - 2.0s
1000a - 10.0s
450a - 100s
350a - 200s
250a- 1000s
200a - forever

As you can see, given the typical usage characteristics of even a high performance golf cart, even this little 200a fuse would likely never blow, even with as big of a golf cart controller you might find.

Even a Very Fast Acting fuse like a ANN-250 will pass 1,050A for 0.1 Sec. and 650A for 1.0 Sec.

I'm speculating, but I don't think there are many, if any, motors typically used in EZGO golf carts that will draw over 500A during normal operation, and if they do they probably won't draw it more than 0.1 Seconds.

[teecro]

So a 250 amp fuse is ok on a 600 amp controller? It's not popped yet, so I'm assuming it's ok...

[cgtech]

Originally Posted by JohnnieB

Even a Very Fast Acting fuse like a ANN-250 will pass 1,050A for 0.1 Sec. and 650A for 1.0 Sec.

I'm speculating, but I don't think there are many, if any, motors typically used in EZGO golf carts that will draw over 500A during normal operation, and if they do they probably won't draw it more than 0.1 Seconds.

I feel that the likelyhood of a typical golf motor capable of drawing more than 500a finding itself in a situation where it's loading is stalled (or rpm kept low) long enough under full load to melt the fuse, while having a pack that the voltage won't sag enough to reduce amp flow by way of reduced voltage, and controller capable of keeping up, is rather unlikely (the perfect storm, if you will). There are a few examples out there, the race carts, but they are far from typical, far from even the typical "hd hunting buggie".

[JohnnieB]

Originally Posted by teecro

So a 250 amp fuse is ok on a 600 amp controller? It's not popped yet, so I'm assuming it's ok...

I don't what ampacity or type fuse Navitas recommends for use with their 600A controller, but whatever it is, that is the one I'd use. Alltrax recommends a 250A fuse for 400A and smaller controllers and a 400A fuse for controllers over 400A.

From an electrical point of view, just because a controller can pass 600A doesn't mean the motor it is attached to can draw 600A. Since the 250A fuse isn't blowing, the motor isn't drawing over 250A for excessive periods of time, or up to 600A for extended periods of time. If it blows, replace it with a 400A fuse.

[JohnnieB]

Originally Posted by cgtech

I feel that the likelyhood of a typical golf motor capable of drawing more than 500a finding itself in a situation where it's loading is stalled (or rpm kept low) long enough under full load to melt the fuse, while having a pack that the voltage won't sag enough to reduce amp flow by way of reduced voltage, and controller capable of keeping up, is rather unlikely (the perfect storm, if you will). There are a few examples out there, the race carts, but they are far from typical, far from even the typical "hd hunting buggie".

D&D dyno testing on the same model as my motor indicate it can draw 444.8A @ 1914RPM with 40.2V applied, so when Alltrax introduced the XCT48400-PDS (no release date for the XCT48500-PDS available at the time) I wasn't sure if it would starve my motor off the line or not, so I recorded some data logs from the DCX500 I was running at the time, while starting from a standstill on a steep incline. (Worst case scenario or as close to the perfect storm as I wanted to subject my cart to.)

I did manage to record 504A through the armature with 39.9V applied on one test run, but they were mostly less than the 460A peak the XCT 400 will pass, so I got the XCT48400 instead of waiting for the XCT48500.

The highest armature amps I've recorded with the XCT is just over 400A, but I've not started from a standstill on an incline, nor do I plan to.

In other words, my experimenting more or less verifies what you've said.