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

[Joseph Gray]

I just replaced the battery in my 3457A. From Mouser: Panasonic BR2/3AE2SP


Joe Gray
W5JG


On Sun, Jan 24, 2016 at 12:54 PM, Dr. David Kirkby (Kirkby Microwave
Ltd) <drkirkby at kirkbymicrowave.co.uk> wrote:
> 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
>
> https://groups.yahoo.com/neo/groups/hp_agilent_equipment/conversations/topics/48964
>
> 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
> http://www.mouser.co.uk/
> 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
> battery
>
> "CROMPTON ETERNACELL  T32/8AA8F  Battery, Single Cell, Lithium Thionyl
> Chloride, 2100 mAh, 3.6 V, 2/3A, Axial Leaded, 16.3 mm"
>
> http://uk.farnell.com/crompton-eternacell/t32-8aa8f/battery-lithium-2-3aa-axial-lead/dp/774017
>
> 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
> deal.
>
> 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,
> UK.
> Registered in England and Wales, company number 08914892.
> http://www.kirkbymicrowave.co.uk/
> Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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