Products > Test Equipment

Fluke 867B, good or obsolete?

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jazz57:
Anyone have luck replacing their battery? The one I have doesn't seem to charge.  >:(

kripton2035:
I bought mine on ebay germany. so far it's working.
I still would like to get one lithium battery for the 867. did not find one !

mahi:

--- Quote from: jazz57 on October 11, 2018, 05:31:04 am ---Anyone have luck replacing their battery? The one I have doesn't seem to charge.  >:(
--- End quote ---

The Fluke 867B was sold with the BP7217 NiCd battery pack which could be charged inside the multimeter. Years after the 867B was discontinued, Fluke also stopped manufacturing the BP7217 battery pack and replaced it with the BP7235 NiMH battery pack. From the outside the new battery pack looks exactly the same but it will not charge inside the 867B! Clearly Fluke felt that the charging circuit of the 860 family was not suited for NiMH batteries and changed the contact wiring to make the multimeter see the pack as a non-rechargeable battery.

In the BP7217 contacts + (plus) and C are connected. In the BP7235 they are not. If you look at the back of the 867B with the battery removed you'll notice it had 3 pins that make contact with the battery. The pins line up with + (plus), C and - (minus). So the multimeter is using contact C to determine wether the battery is rechargeable.

You have 3 options (if you want to use the BP7235):
[*]Get the stupendously expensive Fluke BC7217 battery charger and make sure you get the later version with NiMH support. You still can't charge inside the multimeter but at least you can charge and use the battery pack.
[*]Charge the pack outside the multimeter with a hobby RC battery charger and leads with crocodile/alligator clips. Any charger that can do 6S NiMH at 1~2 amperes will do the job.
[*]Open the multimeter and make a short between the + (plus) and C contacts. From now on, any battery will be considered rechargeable - even if it is not (so pay attention when you are using alkaline cells - don't hook up the power supply).[/list]

I modified my 867B to be able to recharge the BP7235 but I undid it later again. Why? The charging circuit of the 867B is not worth the name. It's a constant charge @ ~170 mA for 16 hours (fixed timer starting whenever the power supply is inserted and regardless of battery condition), then drops to ~40 mA and never cuts off. Since there's no real battery status indicator either it's practically impossible to know when the battery pack is fully charged and the power supply should be disconnected. It's also annoying for extended measurement/logging sessions where the meter is powered from the external supply for tens of hours because you are basically cooking the battery pack.

So in the end I just resorted to using a hobby RC charger. I have two BP7235 packs so the charging time is not that relevant to me.

kwass:
I bought one of these replacements on Amazon years ago and it's been working fine every since: 

https://www.amazon.com/gp/product/B00B71NCMY/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

No modifications needed and pretty inexpensive.

jazz57:
Thank you, Mahi! This is just the info. I was looking for. Apparently the battery I received has the disconnected 'C' terminal. Since the rather simple charger in the meter isn't really ideal for NiMH chemistry, I think I'll just install some Eneloops for occasional use and connect the battery eliminator when I have a long bench session.

And thanks as well to kwass. If I ever decide to get a battery back I'll select an HQRP rather than the Cameron Sino.

The EEVBlog is the best for info. like this!

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