[volt-nuts] Wanted - UK source of a replacement battery (type LX 1634) for HP 3457A 6.5 digit multimeter

Dr. David Kirkby (Kirkby Microwave Ltd) drkirkby at kirkbymicrowave.co.uk
Sun Jan 24 14:54:34 EST 2016

I've got a HP 3457A 6.5 digit multimeter - S/N 2703A04579. It's working
fine, but I'm aware the battery must be at least 11 years old, as I first
bought the meter 11 years ago. I suspect its due for a change.  I'm trying
to find a *reputable* source for a replacement. I want to avoid eBay, due
to the number of fakes on there.

Opening the meter up, I see the PCB shows "BT 601". There's no name on the
battery I can see, but the type number of LX 1634. The voltage measured on
my 4.5 digit handheld DVM is 3.03 V. Googling around


would suggest the battery was made by Saft and is a Lithium-manganese
dioxide (Li-MnO2). The size appears to be known as 2/3A. One source
suggests a replacment is the Panasonic BR-2/3AE2SP

Mouser's uk site
says shipping is restricted, so only available in the USA.

The nearest I've found to anything remotely suitable is actually a 3.6 V

"CROMPTON ETERNACELL  T32/8AA8F  Battery, Single Cell, Lithium Thionyl
Chloride, 2100 mAh, 3.6 V, 2/3A, Axial Leaded, 16.3 mm"


I'd rather not fit a higher voltage battery, although given it provides
power to some 5 V static RAM, I would not expect it to be a problem. That
said, I believe when on mains power this battery is not needed, so there
may be some circuitry that would not like a 3.7 V battery. When power is on
the unit, there is 4.88 V across the static RAM. As mains is reduced, so
the voltage drops to about 2.8 V. I think there must be a Schottky diode
that stops the battery being drained when the mains power is on.

The battery needs to have either very thin pins or wire-ended. Some I have
seen have tags a 2~3 mm wide, which will not fit in the PCB. Others have 3
terminals, which stops you putting it in the wrong way around, but they
will not fit properly on the PCB.

In applications like the 3457A, when the SRAM needs to be kept alive when
power is off, I wish HP would have put two batteries in holders and diode
-OR'ed them. If they had done that, one could just pull out a battery from
holder A, and put a new one in B. Then when B gets old, put one in A.

My first problem though is finding a suitable battery. Next problem is
changing it without losing the RAM contents, but I don't think that's a big

The 3.6 V Lithium Thionyl Chloride is very tempting, as it has a higher
capacity than the Lithium-manganese dioxide and they have a very low
self-discharge (1%/year). I'm just not overly happy about fitting a higher
voltage battery than it is supposed to have, but phyysically it fits, and I
can get one easy enough from Farnell in the UK.

Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
Registered in England and Wales, company number 08914892.
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)

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