Fluke 287/289 Lithium Mod - No More Batteries in the Trash!

[Ingineer]

For your Fluke 287 or 289, This is a super simple mod, the hardest part is removing all the plastic from back of the battery cover.  (It's also fully reversible, just order a new battery cover.)  It's also almost 150% better battery life than even AA (primary) Lithiums!

I used this 12mm x 60mm x 95mm (126095) protected 5Ah 2-cell LiPo (Lithium Polymer) battery from Aliexpress, it fits perfectly:
https://www.aliexpress.us/item/3256803542999333.html

I used some dikes and a vibrating multitool with a straight saw blade to remove most of the plastic on the back of the battery door.  The only mods to the meter itself was soldering on the battery connector, but that's super easy to remove in the future if desired.   I used a JST PH 2.0 two-pin connector for the connection to the meter so the battery is removable for charging.

Because I didn't want to compromise the Cat ratings or safety, I didn't add an external charge jack.  It's also not like you'll need to charge this often because of the long run time.  There is a is a hollow area near the top on the battery door that easily accommodates the battery connector as you can see in the 3rd pic.  I have an external charger setup, and when the pack needs charging, I just remove the battery from the meter.   The Fluke's battery gauge works fine with this 2-cell chemistry, and even though the meter works down to almost 5 volts, the internal protection circuit in the LiPo will probably cut out first.





 

[coromonadalix]

the cell pack was made to go there   

[coppercone2]

I use a zero work mod called nimh batteries

[Black Phoenix]

Yes I saw that mod being sold on tmall.com.

But the one I saw doesn't need any cuts and uses the original battery contacts, so no change on the battery cover:

[BeBuLamar]

I wouldn't do that to my 289 and 287.

[Ingineer]

I was going for extremely long battery life.  NiMh doesn't give that, the best was Lithium AA primaries, but those are not cheap, and I still got almost 150% over them.  If I ever sell the meter and the new owner wants it original, a new back cover is only $45 USD.   The Tmall one looks good, but I bet it's only 1Ah, so 5x less capacity.

[coppercone2]

If there is a grievous fault (surge on line) could the battery explode? Does it maintain cat IV safety?

That is why I don't 'plastic weld' the chassis on multimeters together. It works well with metal staples but I figure that if there is plasma fault inside of the instrument then you could get possibly zapped by the stitches.

[Ingineer]

I don't see how the battery could explode, it would take a continuous overcharge that made past everything in the meter.   Any insane super high voltage/current faults would probably vaporize the connections instantly.

I think the cat rating is preserved, though I have removed some of the plastic, so there's not 100% assurance without a specific test, but I never measure anything over 500V anyway.   I'm comfortable with it.   A fluke with mods like this is still probably better than most cheaper meters!

[coppercone2]

just a heads up so no industrial electrician absent mindedly does this mod. i am still not sure what could happen.

Vaporize in a closed container means plasma conductor like a welding machine. I guess it mainly depends on the HRC fuse.

[Ingineer]

The only thing the HRC fuses protect are the current ratings.  To create plasma in a meter you'd need to send thousands of volts in there, and if you do, you probably have bigger problems at that point.

If you work around > 600V this isn't the right tool for the job anyway.

[scopeman]

Now I finally have a use for the old battery cover where all of the contacts were destroyed by alkaline batteries!

Sam

[coppercone2]

The only thing the HRC fuses protect are the current ratings.  To create plasma in a meter you'd need to send thousands of volts in there, and if you do, you probably have bigger problems at that point.

If you work around > 600V this isn't the right tool for the job anyway.

I have seen regular fuses explode and metalize everything nearby (it probes short circuit )... I have also seen fire shoot out of a meter on video. but the 289 is cat IV to 600V.
I would love to hear about fluke from this..

[DaneLaw]

It looks good, nice mod with a perfect-sized 7.4v 5000mah pack-

[Ingineer]

Sam has another good point.  I've had a lot of stuff destroyed by leaking alkalines, and it seems like the problem is only getting worse.  I wouldn't have that happen on something I use often because I usually notice the low batteries fast, but I've had some older stuff I forgot about succumb to the leaks.   This mod nips that problem in the bud!

[robert.rozee]

it looks like, with minimal effort, Fluke could release an alternative back that holds 2x 18650 Li-Ion cells in a north-south orientation, with spring-loaded contacts onto the cells so these are removable and can be externally charged. the diameter is an AA cell is around 14mm, while an 18650 is 18mm, so they only need to find an extra 4mm; the tilt stand design may also require reworking to accommodate this.

this is what i am looking at doing with a number of battery operated items around the home. good external chargers, like the NiteCore D4, are readily available and modern 18650 Li-Ion cells can hold a significant portion of their charge for longer than the lifespan of an AA Alkaline cell. it also seems that the world is filling up with spare (unprotected) 18650 cells that have good lifespan, left over from discarded laptop and electric scooter batteries.


cheers,
rob   :-)

[BeBuLamar]

I would not buy a 289 with rechargeable battery. For my kind of work I have no time to charge the battery. Replacing the batteries is much faster. The cost of the batteries is unimportant.

[Ingineer]

Yeah, that's why I purchased 2 of the 5Ah packs.  I leave one charged at 8v as a ready-spare.   Given that these (even charged to only 8v) will last longer than even the Energizer Lithiums, and the swap is actually a little faster, I posit that having this mod reduces the amount of time you have to spend fiddling with batteries.   The whole point was to not have to have batteries go dead at a inopportune time like they had been with NiMh.