Fluke 8000a DMM - Battery issue? FIXED

[jjasilli]

My Fluke 8000a DMM is malfunctioning.  It's the 8000A-01 battery pack version.  The LED display is very weak, to dead; it displays very weak changing numerals eratically when switched ON.

I suspect it's the old rechargeable batteries, but am not sure.  The troubleshooting chart in the manual (thanks FYL!) says to check the voltage across C19.  But the -01 Battery version doesn't seem to have this cap!  Also 2 of the 4 batteries are charging to 1.3 volts (rated @ 1.2V 4 Amp Hours); but the other 2 seem dead.  Though the manual says you can run the DMM off wall power while the batteries are charging, this was optimistic in my experience.  I found that unless the batteries were sufficiently charged, the unit would not run off of wall power.  

Anyway I found replacement batteries here: http://www.batterytex.com/product/detail/FLUKE/474353_REV_15/CUSTOM-19/0BF6F407-197E-9BFF-12D9AB78CAFEF82A
But @ $17 ea X 4 = $68 I wonder if it's worth it; especially since I'm not sure this is the fault.  Any thoughts or advice wojuld be appreciated.  Thanks.  

[FYL]

Two of the batteries are probably dead - NiCads are good for only a few hundred cycles. Invert the batteries, then recheck the DMM. If the problem subsists on the other side, you can be pretty sure that the batteries will have to be replaced. If not check connections and wiring.

You can do a kludge and use standard 1.2V NiCads for testing - they won't offer the same capacity but will be more than adequate for 30 minutes or so. If the DMM is OK with these, you can safely order a new set of big bad Fluke NiCads...

Re. the -01 and -015 models, yes, there's no smoothing C19 cap as they derive voltages from clean DC thru the batteries (check figs 5-1 and 5-2 in the manual). Fluke should mention that you should measure around app. 4.8V across the battery assy and not 5V across C19.

[jjasilli]

FYL:  I moved the batteries around so now the 2 dead batteries are in the known good charging positions.  The unit is recharghing.  I'll re-check it in the morning.   

(BTW - Fig 5-2 eventually got me to guess that maybe C19 and its companions don't exist in the battery model.  But I wasn't sure if they were cleverly relocated to make room for the batteries!)

Thanks for your suggestions.!

[jjasilli]

Progress - the 2 dead batteries have remained dead in the known good charging positions.  The 2 functioning batteries have fully recharged in their new positions.  This tends to confirm that these old batteries are the problem.  Meanwhile I ordered a set of more reasonably priced rechargeable NI-Cad D cells here:  http://www.all-battery.com/nicddsize5000mahrechargeableflattopbattery.aspx

Will report when I receive shipment of the new batteries.  Meanwhile, I guess it's possible to build a 5VDC supply inside the DMM off the PT secondary; but am not sure how to do this. 

[FYL]

(BTW - Fig 5-2 eventually got me to guess that maybe C19 and its companions don't exist in the battery model.  But I wasn't sure if they were cleverly relocated to make room for the batteries!)

Page 5-7 states "C19 Not used on (8000A-1 and 8000A-015)". One of the numerous changes between versions...

[FYL]

Progress - the 2 dead batteries have remained dead in the known good charging positions.  The 2 functioning batteries have fully recharged in their new positions.  This tends to confirm that these old batteries are the problem.

Yup. Dead NiCads. Not very surprising considering that you're dealing with a vintage DMM.

Meanwhile I ordered a set of more reasonably priced rechargeable NI-Cad D cells

A full set? You should change the 4 batteries.

Meanwhile, I guess it's possible to build a 5VDC supply inside the DMM off the PT secondary; but am not sure how to do this. 

That's possible, but the mod would be ugly...

[jjasilli]

Page 5-7 states "C19 Not used on (8000A-1 and 8000A-015)". Right you are!  But those very very nice people listed C19 twice; and I missed the 2nd listing.   

Yup. Dead NiCads. Not very surprising considering that you're dealing with a vintage DMM.  Well, if the darn thing has an AC plug . . .   


A full set? You should change the 4 batteries.  Yup!     These batteries even have the end tabs for soldering and all 4 were the price of 1 genuine replacement battery.

That's possible, but the mod would be ugly...  True, I guess even too ugly for inside the case! 

[jjasilli]

Installed 4 new batteries.   My meter is back to work, better than ever.  Now it can be used instantly even while the batteries are charging, just like the manual says.   I guess the old batteries were dying when I 1st rec'd the meter.  Now all my test equipment is finally working.  I am a happy camper!

Thanks FYL for all your help with this project.

[FYL]

Now all my test equipment is finally working.  I am a happy camper!