Electronics > Repair
Tektronix TDS3BAT rebuild
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Dave Wise:
Not a photo, but I scoped the connector.

Pinout:

<locating key>
MINUS
NC
DATA
PLUS-TO-CHARGER
BAT-PLUS

The DATA line uses the Unitrode/Benchmarq/TI "DQ" 333 bit per second protocol.
I believe the TDS3BATB (maybe TDS3BATC too) contain a BQ2050 gas gauge chip.  TDS3BAT would be an older BQ20xx meant for NiCd.  Look at the TI site, filtering for fuel gauges using DQ protocol.  Not SDQ or HDQ or I2C or SMBUS.

When the scope is running from mains and charging the battery, once every second it reads six registers, 0x3 (Nominal Available Capacity High byte), 0x17 (NAC Low byte), 0x3 again (in case it rolled over I guess), 0x1 (FLGS1), 0x2 (TMP) and 0xB (VSB - battery voltage).  NAC increments approximately every five seconds.  The temp field of TMP reads a constant 7 (30-40C) while the gas gauge field incremented once in about a half hour.  FLGS1 returns 0x94 indicating Charging and Capacity Inaccurate.  I don't like CI but maybe the scope doesn't care.

The gauge's reply timing is unstable, I got good results using B Trigger in Event Count mode.  Commands are 9 negative edges, returned data is 8 edges.  So you can scroll through the commands and replies by setting the event count.
SMdude:
Excellent, thank you so much!
coppercone2:
Lol, I soldered a bunch of tabbed NiMH batteries and put them in the place of a missing NiCAD pack that is in some equipemnt I use like once a year max, since it would NEVER be charged on a NiCAD. Anyway, I charge it at like 1/10ish C on a lab constant current power supply and it seems to be holding up alright, after 6 months I got the expect runtime out of it, and after recharge without disassembly or modification everything seemed in order. Its probobly not ideal but I just slapped it in there.. kind of interested to see what will happen in 2-3 years when the batteries are aged and improperly charged a few more times.
Dave Wise:
About my TDS3BATB that reads Capacity Inaccurate: after a complete discharge and charge, now it reads Capacity Inaccurate + Valid Discharge.  I expect CI (and VDQ) to go away after one more full discharge, meaning the gas gauge is calibrated.

If you want fast charge but don't have a TDS3CHG/TDS3ION, it looks like a normal bench supply will do.  I set mine to 18V with 1.8A current limit, based on the TDS3CHG spec sheet.  Connecting it to the TDS3BATB external charge coaxial connector, I see about 1.3A which tapers after a couple hours then shuts down to a few tens of mA at charge complete.  I will probably charge them this way - outdoors - if Tek continues to refuse my packs for recall.  And store them in a metal box.  That should be safe.
To extend battery life I will store them only about half-charged.

On initial installation in a scope running off the mains, I see the usual six register reads, then this, once:

read 0x7 (PPD Program Pin Pull Down) == 09 i.e. Prog1 and Prog4 power-on straps were low
read 0x8 (PPU Program Pin Pull Up) == 80 i.e. no power-on straps were high, so Prog2/3/5/6 were all in 'Z' state
(By the way, one thing this means is the cells are coke anode, not graphite anode.)
write 0x8c (VTS End Of Discharge Threshold Select) = 0xA2 i.e. 10.63V
read 0x0c (VTS) to confirm it is 0xA2
(The exact value was probably stored in RTC RAM and depends on what the scope read on VSB just before it died.)

For more info, see "Battery voltage and pinout for Tektronix TDS 3000 series oscilloscope",
https://www.eevblog.com/forum/testgear/battery-voltage-and-for-tektronix-tds-3000-series-oscilloscope
Dave Wise:

--- Quote from: Dave Wise on October 30, 2021, 09:51:14 pm ---
--- Quote from: texaspyro on November 09, 2020, 12:58:28 am ---If you have a TDS2BAT,,, they have been recalled for safety issues.  Tek is still replacing them for free.

--- End quote ---

Not to me they wouldn't.  They claim they can't ship them in Oregon.  I don't believe it.

--- End quote ---

UPDATE: Tek finally replaced my battery packs!  (After I filed a Consumer Protection complaint with Oregon Department of Justice.  I don't know if that's what got them off the dime, or if they were just slow.  But eventually a manager got involved and overrode the script.)
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