Datron 4910 battery replacement in UK plus Fluke 732a question

[Oldtestgear]

I have read various comments about replacing the batteries on the Datron 4910 including the link to Mouser for the recommended replacement. As Mouser will not ship these to the UK has anyone found a suitable battery available locally? The closest I have found so far is the Power sonic PS-610 type but this is only 1AH.

I was lucky enough to grab the Datron 4910 plus 3 of the fluke 732A references from a dealer that bought a lot of surplus stock from a cal lab in Hertfordshire in the last few weeks. As it is a Datron it is not working but the Flukes  all power up but need new batteries which I have ordered. I am wondering what to do with the 3 Flukes. Do I update as suggested on the XDevs site or only replace the batteries.  I do plan to sell these as I have spent way too much money buying  voltage standards recently. Thoughts anyone?

Phil

[alm]

I've been using this pack of 2x5 AA cells (also 1Ah) for my 4910, but it looks like Digikey discontinued all pre-made AA battery packs. My main concern would be that the cells are designed for continuous charging like a backup battery. So rather a 1Ah industrial cell over a high capacity consumer-grade cell. The one I ordered was the closest I could find. If you have a spot welder to make your own battery pack, then that might be the best option.

If the goal is for resale, I would do the minimum changes possible that make them work. It's unlikely that you'll make the extra money back in a higher selling price. Personally, when I'm buying, I'd rather do any refurbishment like capacitor replacement myself rather than hoping the seller did it well with good quality caps. If you choose to replace the batteries, then I would adjust the charging voltage so the new batteries are not getting cooked.

[Oldtestgear]

Thanks for the suggestions and that you are using 1AH battery packs in your 4910.  Like you I always am concerned about how well something has been refurbished by a seller unless I know the person involved.  The 4910 can be fully refurbished  as I plan to keep it. The Fluke 732As  are a different case as I need to sell these to get some money back in my account.  I will not, for example, change these to use 12V batteries but keep it original.  Electrolytic caps will certainly need to be changed if these are cooked & the battery charging circuit modified to prevent the new batteries being cooked. I will keep receipts for parts ordered to show what has been done. 

Phil

[tggzzz]

My understanding (and I use that word loosely) is that NiMH cells do not take well to trickle charging. (Yes, I know: there are too many adjectives in that sentence)

BTW, I'm up the M5 from you, should you want to measure and/or dispose of the references. But I don't need yet another voltage ref!

[alm]

Sorry, ignore my post about the 4910: I was confusing the 4910 with the 7001. I used 1Ah AA NiMH AA cells in the 7001, which was designed to use AA cells. So I imagine they built the proper charging circuit for it. I wouldn't replace the SLA cells in the 4910 with NiMH.

My 4910 survived well over 48h on battery, so I'm not too worried about the state of the batteries yet, and I couldn't find easily available cells with the right dimensions from a reputable brand.

I believe some people have used NiMH cells in the Fluke 731B which was originally designed for NiCd cells. Some industrial NiMH cells say they are okay with trickle charging at a very low current, and as you install higher capacities cells while the charging current remains the same, the current relative to the capacity goes down (so 0.01C becomes 0.005C if you double the capacity). So it's probably sort of possible under the right circumstances, but not worth refitting a unit designed for SLA cells with in my opinion.

[tggzzz]

I believe some people have used NiMH cells in the Fluke 731B which was originally designed for NiCd cells. Some industrial NiMH cells say they are okay with trickle charging at a very low current, and as you install higher capacities cells while the charging current remains the same, the current relative to the capacity goes down (so 0.01C becomes 0.005C if you double the capacity). So it's probably sort of possible under the right circumstances, but not worth refitting a unit designed for SLA cells with in my opinion.

I certainly agree about retrofitting/replacing SLAs.

I suspect part of the confusion about trickle charging NiMH is part ignorance, part Dunning-Kruger syndrome, part Boeing 737-MAX marketing, part subtly differing chemistries, part "optimistic" rating, and part truth. Not an topic on which I would like to make explicit statements!

[alm]

I suspect part of the confusion about trickle charging NiMH is part ignorance, part Dunning-Kruger syndrome, part Boeing 737-MAX marketing, part subtly differing chemistries, part "optimistic" rating, and part truth. Not an topic on which I would like to make explicit statements!

This is getting off-topic since neither the 4910 nor the 732A use NiCd or NiMH cells. I'd say the most authoritative information you're going to find is on the second to last page of this Panasonic catalog regarding their industrial infrastructure backup cells. Obviously this only applies to these specific cells.

[tggzzz]

I suspect part of the confusion about trickle charging NiMH is part ignorance, part Dunning-Kruger syndrome, part Boeing 737-MAX marketing, part subtly differing chemistries, part "optimistic" rating, and part truth. Not an topic on which I would like to make explicit statements!

This is getting off-topic since neither the 4910 nor the 732A use NiCd or NiMH cells. I'd say the most authoritative information you're going to find is on the second to last page of this Panasonic catalog regarding their industrial infrastructure backup cells. Obviously this only applies to these specific cells.

Useful; thanks.

The recommended mechanism for standby charging Panasonic NiMH is a 15 day cycle of self-discharge and charging.