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χ1 has stopped charging

chi1

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χ1 has stopped charging

Postby Coughinhk » June 8th, 2012, 11:04 am

Hi,

One of my x1 boards seems to have died. It was working fine but I didn't use it for a while and then I got it out again and plugged in the 9V charger and ... nothing.

So first I checked batteries - both at roughly 3V and just over 6V in total. Well above the 5.6V threshold for charging. All the test points are correct. UV high, OV high, LPW low, VSS low. 9V on the x1/mini3 interconnections.

I removed the batteries anyway and charged them in another X1 with the same 9V charger. All good. They discharged and then went back in the dead X1 (jp1 shorted) reading about 3.3V each, removed the jp1 short and tried to charge. Still no joy and all test points correct.

The amp works fine so I'm thinking it must be one or both of the ICs. Do you have a set of checks I can follow to find out which or both IC has died ? Any idea why it would die, given it hasn't left its case since it was first built ?

Cheers
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Re: X1 has stopped charging

Postby amb » June 8th, 2012, 1:22 pm

Sounds like a problem with U1... Does the "charge" LED light up at all? If so what color?
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Re: X1 has stopped charging

Postby MisterX » June 8th, 2012, 1:49 pm

I was thinking U2...
What's the voltage between B+ and VSS?
1352.5 and counting.
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Re: X1 has stopped charging

Postby Coughinhk » June 8th, 2012, 7:43 pm

Hi,

Thanks for the replies.

No light from the LED at all - so no stat1 or stat2 indicators, unless the led has gone. However, I checked the battery voltages when the charger was plugged in, and they didn't rise, so charging didn't start.

Vss was low (0V) and B+ was 6V the first time and 6.6V the second, so I guess the pd between vss and B+ would be 6.6V. I can't check that right now because I've pulled both batteries out and I'm charging them separately using an MCP73861. I'll try installing them fully charged. I doubt it'll make any difference but it's worth a try - besides, not much else I can do as I will need to order any replacement parts, assuming an IC has died.

Thanks,

Tom
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Re: X1 has stopped charging

Postby Coughinhk » June 8th, 2012, 10:02 pm

Hi,

Tried the freshly charged batts. No change. Tried some partially charged spares. No change. I took off the amp and fitted a 9V supply at J1 interconnect on the x1 board and measured with the partially charged batts:

Test Points
B- Com 3.95V
Com B+ 3.89V
B- B+ 7.84V
B- LPW 0.000V
B- UV 7.84V
B- OV 7.84V
B- Vss 0.000V
J1 interconnect 9.02V/8.99V (center pin gnd)

U1 MCP73864 Pins (pd to B-)
1 7.93V (stat1)
2 7.78V (stat2)
3-5 9.01 (Vset, Vdd1, Vdd2)
6-7 0.000V (Vss, prog)
8 2.508V (Thref)
9 0.844V (Therm)
10 1.285-1.485 (ACV 0.48-0.55) (Timer)
11 0.000V (Vss3)
12-14 7.84V (Vbat1-3)
15 0.000V (Vss2)
16 9.02 (En)

I have no idea how to test this is working or not. Little help please ? I was thinking I could ground pin 16 but I see on the pcb that this would create a short on the output of the IC so that wouldn't be a good idea.

BTW for the program resistor, I chose 1.8K (instead of 1K) which gives a charge rate of 470mA (0.8C) because I wanted to keep it under 500mA. My psu can output 1.2A but I was planning to try other psu's at some point. I was thnking about using a boost reg from a dual/parallel USB input to get 9V @ 500mA. I haven't tried this yet. So many plans....

http://www.ebay.co.uk/itm/New-LM2577-DC ... 1767wt_922


U2 UCC3911-4 (not 3 = slightly higher voltage but otherwise the same so it shouldn't be a problem ?)

1 0.240 (varies up and down slightly) (NC)
2-3 7.84 (0V, UV)
4-8 0.000V (Subs, Gnd, LPWarn)
9 3.25V (varies up and own slightly) (CE)
10-11 0.000V (BO)
12-13 0.257 (varies up and own slightly) (Subs)
14 3.9V (B1)
15 0.007V (CDLY)
16 7.84V (B2)

Any idea if these readings are normal ? They seem so to me. I also tested the led using a gnd point and it is still working.

As I understand it, this has an FET between gnd and B0 that can switch the battery cells on and off. So to test this is working, I could try shorting the gnd and B0 pins and see if charging starts ?

EDIT I removed the batteries again and measured the resistances between the B0 (pin 10) and gnd (pin 7) and it was around 50M R. I then shorted JP1, fitted the batteries, removed the short and check the test points - all good. I measured the resistance between B0 and gnd and it is now 0.00 R, and no voltage across them either. So that seems to say that U2 is working and U1 is faulty.

The MCP73862 is 25% cheaper than the MCP73864, and they are the same except for the stat outputs, so I'll get some of the 2s to replace U1. Wait and see if it dies again I guess.

Here's a photo.

Image
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Re: X1 has stopped charging

Postby Coughinhk » June 11th, 2012, 1:18 am

Hi,

It's working again - the MCP73862 works fine. Now I have four spares for the next time ;-)

BTW I found a seller with the genuine Walkera batteries - US$5 each. They fit without grinding the boards.

http://www.ebay.com.hk/itm/261023821669 ... _591wt_905
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