Tek TDS3000 series, LI-PO battery conversion?

[Tracker]

Hi Folks,
Has anyone managed to make a LI-PO pack using 18650 batteries and a balanced charger board?

I figure it can't be too hard since the original tds3batc pack is 12v...

The TDS3000 series has 5 pins in the battery compartment, but without a schematic diagram its hard to know what they all do... any ideas?

Thanks
 

[rvalente]

A quick google search brings the battery module already is lithium (not sure if lipo or liion).

[Tracker]

yes saw that, but I want to make my own with 18650 and a balanced charger board.

I just don't know the pinput and function,

This is what I can measure...
pin 1  Gnd
pin 2  Gnd
pin 3 +3v with a 1 second pulse
pin 5 +14.4v
pin 5 +14.8v

For some reason i can't find a schematic, the 'service manual' has blank pages labeled Diagrams???
 

[Tracker]

So an update and a question....
I think I found a pinout over on another thread: https://www.eevblog.com/forum/testgear/battery-voltage-and-for-tektronix-tds-3000-series-oscilloscope/

<locating key>
MINUS
NC
DATA (used to query the battery status)
PLUS-TO-CHARGER
BAT-PLUS

I was thinking to just ignore the 'data' and hook up a 12.6v Li-PO balanced charger circuit...
PLUS-TO-CHARGER would be the charging input to the balance board
BAT-PLUS would be the Balance board output.

Using this balanced board... https://www.ebay.co.uk/itm/174692848077?hash=item28ac8151cd:g:vWsAAOSwH-BfvgR9

see anything wrong with this idea?
Apart from  no current limit on the lipo output...
 

[Extrasolar]

Hi Tracker,

What data protocol might be used here ?? 
Because I am only getting a "Wake Up" query from the scope, but the Module is not responding back !!

[Tracker]

Looks like proprietary communication developed by Tektronix, fair play if you manage to work it out.

[james_s]

Looking at the way that pack is constructed makes me think it was originally NiCd and then changed to Li-ion in later versions, possible they just made it the size it is in order to use the same space for probe storage though. The scope may run without using the data connection but I doubt it will charge the battery, but with access to a genuine pack it might not be too hard to reverse engineer the protocol.

[capt bullshot]

Some time ago, I took one of these Lithium powered packs apart (just because I'm nosy, not to dispose or destroy it). Indeed there's some rather complex electronics inside, converting the typical Li-Battery behaviour to the expected NiCd (or NiMH) behaviour of the scope (as in DC/DC converters, and probably a Li charge controller and balancer, all that stuff that isn't required for a Ni based battery). I'd guess neither the external charger brick nor the internal charger of the oscilloscope is able to correctly charge a Li based battery. Apparently they've built all the electronics (DC/DC etc.) to interface Li batteries to a scope and an external charger that expects to charge Ni based batteries. Didn't care about the data line and protocol while looking at it.

[Dave Wise]

TDS3BATB and TDS3BATC use a TI BQ2050 gas gauge IC.  I don't know what was used in the original Ni-Cd TDS3BAT, but the comm protocol must be the same because all packs are compatible with all TDS3000-series scopes.