ebike kit advice needed

[Deleted member 4366]

Looks like it.

The other possibility is that it's stuck open. Check that the gate voltage is zero. That's the left hand leg to ground. If It has somewhere around 12v to 18v on it, the peoblem is that something else is telling it to open.

 

[flying-chase]

Hi d8ve, thanks for your help. How can I do this as I can't apply any power to it without it blowing the fuse.

Are the middle 4 the green fet's ?
https://www.endless-sphere.com/forums/download/file.php?id=127078. I'll contact BMS and see what they suggest, otherwise I'll have to replace them myself. Do you have any idea why they would blow like this?

 

[Deleted member 4366]

Good point. Instead you need to measure the resistance between the right two legs of all the FETs on that phase to see if any of them are open when there's no power. Measure the resistance in both directions. If none are open, then the problem is the gate voltage stuck on.

 

[flying-chase]

Hi d8ve
I measured the resistances across the legs. On 8 it was 1 , but on the middle 4 it was 0.4. I also measured between left and right legs on the 8 it was 1 but on the four in question it was 4.3, 4.3, 89.5, 89.5. I hope you can make some sense of this?

 

[Deleted member 4366]

Can you tell me exactly which controller it is?

 

[flying-chase]

its the S12S 500W
http://www.bmsbattery.com/controller/552-s06-250w-imitation-torque-square-wave-controller.html

 

[Deleted member 4366]

OK, So there's four FETs on each phase. You determined that the green phase is open, so you only have to look at those four FETs. There's two adjacent ones in parallel for the up-side pulse and two in parallel for the down-side one.

Each in each pair should give the same result as its partner. It looks like the one that you call no.8 is faulty. What end are you counting from?

Can you take a decent detail high resolution photo of the back-side of the PCB in that area? Post as a link from Photobucket or another image host. Take the photo directly from above, not angled. I only need to see the area around those 4 FETs. I don't need to see what type of table it's sitting on, or what's in your workshop.

 

[flying-chase]

<a href="http://s100.photobucket.com/user/charleshartshorneying_chase/media/controller_zps6eb929a8.jpg.html" target="_blank"><img src="http://i100.photobucket.com/albums/m32/charleshartshorneying_chase/controller_zps6eb929a8.jpg" border="0" alt=" photo controller_zps6eb929a8.jpg"/></a>

Hi d8veh
I hope that the above link works and that the image is suitable. As regards my number, I meant that on 8 of the fets the value was 1. But on the other four it was 0.4 etc. i.e. the measurements that seem different were always on the middle set of four.

 

[Deleted member 4366]

Out of those four FETs, I'm looking at the second from the left in your photo. The track runs downwards from the middle leg to the thick track along the edge. No other part of it should touch any of the other tracks. In the photo, it looks like there's a bridge upwards. Can you verify that by scraping it with a sharp point. First, determine whethere there is a bridge, then scrape right through it to clear it if there is one.

 

[flying-chase]

By bridge I assume you mean a bit of varnish like material that I scraped off?

 

[Deleted member 4366]

No. I mean solder.

 

[flying-chase]

No solder I'm sorry to say. That fet is one of the two that reads 89.5 across the two outer legs (and the other fet is the one to its left).

 

[Deleted member 4366]

Can you measure the resistance again of only those 4 FETs. Start with the first one. Measure between the middle and right legs as you look at it from the front (black side with writing on it). Then repeat with your probes the other way round. Repeat for all four FETs, so there's eight results.

List those 8 results, and then do the same for one of the other two groups of four so that we get another eight results.

 

[flying-chase]

From l to r they all measure 00.4, measuring between middle and right legs. All other fets measure as 1.

If I measure between l and middle legs I get 89.8, 89.8, 4.4, 4.4. All others are 1

 

[Deleted member 4366]

I should see two lists of eight results. Please express them this way so that I can understand them. Please also give the units and scale. We should be seeing kilo-Ohms (K) or mega-Ohms (M).

 

[Deleted member 4366]

Green phase
FET 1 L to R = ? K
FET 1 R to L = ? K
FET 2 L to R = ? K
etc.

Blue phase
FET1 etc.

Only measure between the centre and left leg. L to R above refers to the direction of measuring, i.e which way round you position your probes.

 

[flying-chase]

Hi d8ve, wouldn't the resistance be the same? If I understand you correctly, I must measure between middle and right leg and then swap probes and repeat still measuring between middle and right leg. Is that correct?

 

[Deleted member 4366]

Resistance isn't necessarily the same. Think of diodes. Correct. Swap your probes and measure again.

 

[flying-chase]

Hi d8veh,

Looking at the front of the FET, measuring middle leg to right
Green phase
FET 1 L to R = 0.40 K
FET 1 R to L = 0.40 K
FET 2 L to R = 0.40 K
FET 2 L to R = 0.40 K
FET 3 R to L = 0.40 K
FET 3 L to R = 0.40 K
FET 4 L to R = 0.40 K
FET 4 R to L = 0.40K

Yellow phase
FET 1 L to R = 1
FET 1 R to L = 1
FET 2 L to R = 1
FET 2 L to R = 1
FET 3 R to L = 1
FET 3 L to R = 1
FET 4 L to R = 1
FET 4 R to L = 1


Looking at the front, measuring middle leg to left
Green phase
FET 1 L to R = 90.1 K
FET 1 R to L = 92.8 K
FET 2 L to R = 90.1 K
FET 2 L to R = 92.8 K
FET 3 R to L = 4.4 K
FET 3 L to R = 4.4 K
FET 4 L to R = 4.4 K
FET 4 R to L = 4.4K

Yellow phase
FET 1 L to R = 1
FET 1 R to L = 1
FET 2 L to R = 1
FET 2 L to R = 1
FET 3 R to L = 1
FET 3 L to R = 1
FET 4 L to R = 1
FET 4 R to L = 1

Hope this helps

 

[Deleted member 4366]

It certainly helps, but I'm very confused. When you touch your probes together, do you get 0 or 1 on the meter?

Before, your measurement of ground to green was zero, which means a short circuit. Now you have resistance between all the grounds and lives, so no short circuit. Instead, all the yellows are shorted and the greens are in the correct range!