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10S Battery Controller Module help please

Hi all,

I was asked to look at an electric scooter for a friend today. His friend bought it directly from China, ran it ok for a couple of months and then it just stopped working (so no point trying to send it back from the UK).

Whilst I'm reasonably comfortable with basic electrics and electronics I'm not familiar with the sort of things you find now days around Lixx type cells and packs and hence why I am looking for some advice here please.

FWIW, we connected the 36V, 40 cell pack (possibly 4 x 10 or 10 x 4 in parallel?) up to the scooter charger and saw the terminal voltage go from around 36 to 40V (charger max 42V) and the current initially sit at 2A and then start dropping to about 1.8A after maybe an hour. I believe the cells are these:

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(making the pack ~36V x 8.8 Ah)

Putting a load (3 x 12V x 21W lamps in series) across the battery output showed nothing. Putting the load across the cell monitoring wires (eg, directly on the battery) had the lamps shining brightly (indicating there was nothing wrong with the battery itself, at least with a load of around 2A)?

We then turned to the BCM, un wrapped it and found and tested a (65 degree) thermal switch and that seemed ok (short cct).

I've since split the BCM and this is the working side (the other half is the monitoring board [1] and connects the main board via a 4 pin link shown at the top):

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The two wires you just see top right go to the 5A thermal switch, the blue wire top left is the negative out ... and the pad J2, top right is as marked, connected directly to the battery -ve. So this board and all the cell monitoring connections work WRT the battery Ov?

The charging connector is basically across the output.

Now, from Googling about I think I understand some of the components on that board may control the charging and that seems to work (or at least not be dead), so I think we are looking at something that may enable the output, presumably as long as the battery voltage is sufficiently high and the pack temperature is less than 65 DegC etc?

The T0-220 devices seem to be 3 x RU75ND8R mosfets + 1 x HY1807.

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From what I can see the gates of the two devices to the left are driven from the two EL817 photocouplers seen bottom left.

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I found something that might give some hint of a similar issue here:

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And a more detailed description of how it might work on the last post:

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So, I'm not sure where to go next. I do have one of those little component testers so, assuming I couldn't test the power devices in circuit I could de-solder them (FETs) and may be able to test them but what are the chances of that being the fault and it not be some of the other (SM) circuitry please?

Cheers, T i m

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Reply to
T i m
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That driver board has a lot of bad solder joints on it...

Use loup if you have one put some clean solder on the joints where the power fets are especially.

Jamie

Reply to
M Philbrook

Where is R0?

Reply to
c4urs11

Good question. ;-)

The only thing I can offer is I don't think it's fallen off and if it was in parallel with the thermal trip, would only come into play if/when that tripped (went o/c)?

Cheers, T i m

Reply to
T i m

This one?

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Whilst I agree they don't look very pretty I do have a loup and have just given it a look over and *I* can't see anything obvious ... but then I many not be able to spot something that is obvious to others. ;-)

If I'm there re-doing the joints I might as well take the FETs off one at a time and put them in my tester and see what it says? Or at least do the two that don't seem to be involved in the charging (that I believe works etc).

Cheers, T i m

Reply to
T i m

FWIW, I've just desoldered the legs of the power FETs, tacked short wires into them and plugged them into my little component tester. I'd say the results suggest they are ok?

(Looking at the FETs left to right):

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Again, when I de-soldered them they looked ok so it may have just been a camera thing.

Whilst some of the joints look a bit 'iffy' under the loup, I think they are just that and are making electrical connection. The worst seem to be post manufacturer 'mods' rather than straight manufacturing faults.

I have found a generic BMS board on eBay that looks compatible so in light of the FET test (assuming the test means anything) I might just give one of those a go.

Cheers, T i m

Reply to
T i m

The 2 nd from the right To-220 looking FET seems to be shorter than the others. As the back of the FET is the 3 rd leg should it have a wire connecting to that long pad above it ?

Reply to
Ralph Mowery

Well spotted (and thanks for looking etc) but for some reason there is no tag on that FET but the whole back was soldered to what I think is the ground at the back.

In fact, I desoldered the tag on the right hand FET and the two leads from the pads but it was still stuck solid. It seems there are two soldered areas under the FETs, one under the tag and one right underneath.

Whilst de-soldering the 3rd FET it came off the board completely.

Cheers, T i m

Reply to
T i m

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