using Li-ion battery in Fluke 97 scopemeter

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I got this meter quite cheap with no accessories and no battery pack. Replacement Ni-CD and NI-MH packs are sold for $20-30, but, instead of spending money on obsolete technology, I decided to figure out if I can use Li-ion cells to build a pack for free. I have plenty of various used cells salvaged from laptop packs and such. It turned out that it is easy to use 2-cell Li-ion packs in this meter. Such configuration is not perfect, but works fine. I ended up adding a battery management module for about $3 for extra safety and, hopefully, longer life of the pack.

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Here is the battery management module I used:

[texaspyro]

One big advantage of only charging the cells to 4V is that they will last 10 .. 100 times longer than fully charging them.

I would also look at using low self discharge NiMH cells.  The 8V charge voltage is the open curcuit voltage.  The charger circuit is current driven, so it will limit the voltage to whatever it takes to get 170 mA to the pack.

I built a replacement pack for my Tek THS730A using 4500 mAh AcuEvolution C cells around 10 (?) years ago.  Avoid no-name Chinese cells like the plague.   It is still running fine.    At times, the scope has sat around un-used for months and still powered up and ran for a long time.  I have never felt the need to do a run-time test on the scope.

Since the NiMH cells have over twice the capacity of the nicads, the charge rate works out to around C/30.   OK-ish for a NiMH trickle charge.  I try to avoid leaving it on charge for extended periods, but occasionally left it charging for a week or so.  The cells get pleasantly warm. 

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Finally I monitored the discharge of the new LiPo pack from 8V in the meter. The runtime was about 10.7 hours.

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This is a followup to the Fluke 97 Li-ion Battery Upgrade video. A very cheap Fluke 99 was picked up on eBay with some problems. A Lipo pack was built for it. This time the charging voltage was adjusted from 8V to 8.4V, and also the charging current was doubled.

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Improvised battery door (I happened to have only white plastic of the right size and thickness handy).

[Swake]

These covers are not really visible, anyhow it is nothing that a lick of paint can't resolve if you want to.

Thank you for the video's on the battery. These made my quest for a modernized battery to help out a freshly acquired PM97 much easier.