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:

http://www.ax-ps.com/pdf/datenblatt/LR1865_SI.pdf

(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):

https://dl.dropboxusercontent.com/u/5772409/BCM%201.jpg

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.

https://dl.dropboxusercontent.com/u/...0datasheet.pdf

https://dl.dropboxusercontent.com/u/...0datasheet.pdf

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

https://dl.dropboxusercontent.com/u/...0datasheet.pdf

I found something that might give some hint of a similar issue he
https://endless-sphere.com/forums/vi...p?f=14&t=67012

And a more detailed description of how it might work on the last post:
https://endless-sphere.com/forums/vi...67012#p1008437

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

[1] https://dl.dropboxusercontent.com/u/5772409/BCM%202.jpg
https://dl.dropboxusercontent.com/u/5772409/BCM%203.jpg

In article ,
says...

https://dl.dropboxusercontent.com/u/...0datasheet.pdf

I found something that might give some hint of a similar issue he
https://endless-sphere.com/forums/vi...p?f=14&t=67012

And a more detailed description of how it might work on the last post:
https://endless-sphere.com/forums/vi...67012#p1008437

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

[1] https://dl.dropboxusercontent.com/u/5772409/BCM%202.jpg
https://dl.dropboxusercontent.com/u/5772409/BCM%203.jpg




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

On Sat, 26 Mar 2016 21:38:52 +0000, T i m wrote:

and then it just stopped working

Where is R0?

On 27 Mar 2016 00:53:48 GMT, c4urs11 wrote:

On Sat, 26 Mar 2016 21:38:52 +0000, T i m wrote:

and then it just stopped working

Where is R0?

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)? shrug

Cheers, T i m

On Sat, 26 Mar 2016 19:06:00 -0500, M Philbrook
wrote:

snip



That driver board has a lot of bad solder joints on it...

This one?

https://dl.dropboxusercontent.com/u/5772409/BCM%201.jpg


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

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

On Sat, 26 Mar 2016 19:06:00 -0500, M Philbrook
wrote:

snip

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):

https://dl.dropboxusercontent.com/u/...ET%20board.jpg
https://dl.dropboxusercontent.com/u/5772409/FET%201.jpg
https://dl.dropboxusercontent.com/u/5772409/FET%202.jpg
https://dl.dropboxusercontent.com/u/5772409/FET%203.jpg
https://dl.dropboxusercontent.com/u/5772409/FET%204.jpg


That driver board has a lot of bad solder joints on it...

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

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

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

"T i m" wrote in message
...
On Sat, 26 Mar 2016 19:06:00 -0500, M Philbrook
wrote:

snip

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):

https://dl.dropboxusercontent.com/u/...ET%20board.jpg
https://dl.dropboxusercontent.com/u/5772409/FET%201.jpg
https://dl.dropboxusercontent.com/u/5772409/FET%202.jpg
https://dl.dropboxusercontent.com/u/5772409/FET%203.jpg
https://dl.dropboxusercontent.com/u/5772409/FET%204.jpg



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 ?

On Mon, 28 Mar 2016 10:59:19 -0400, "Ralph Mowery"
wrote:


"T i m" wrote in message
.. .
On Sat, 26 Mar 2016 19:06:00 -0500, M Philbrook
wrote:

snip

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):

https://dl.dropboxusercontent.com/u/...ET%20board.jpg
https://dl.dropboxusercontent.com/u/5772409/FET%201.jpg
https://dl.dropboxusercontent.com/u/5772409/FET%202.jpg
https://dl.dropboxusercontent.com/u/5772409/FET%203.jpg
https://dl.dropboxusercontent.com/u/5772409/FET%204.jpg



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 ?


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