fluke 731b battery pack
On Wed, Aug 3, 2016 at 2:08 PM, David davidwhess@gmail.com wrote:
I looked at the schematic and is seems feasible without excessive
effort. Either the existing simple series preregulator can be
modified or replaced allowing it to both charge the battery (through a
blocking diode) and power the instrument or a completely separate
power charging circuit can be added in parallel.
The existing charging circuit is in parallel with the pre-regulator; they
are separated by CR5 and CR6 and the pre-regulator/battery outputs are
combined by CR8 and CR9. The only problem with the existing circuit is
with a fresh, strong, fully charged battery pack, charging pulses will leak
past CR8 with only R1/C1 to filter them.
On Wed, 3 Aug 2016 14:30:33 -0700, you wrote:
On Wed, Aug 3, 2016 at 2:08 PM, David davidwhess@gmail.com wrote:
I looked at the schematic and is seems feasible without excessive
effort. Either the existing simple series preregulator can be
modified or replaced allowing it to both charge the battery (through a
blocking diode) and power the instrument or a completely separate
power charging circuit can be added in parallel.
The existing charging circuit is in parallel with the pre-regulator; they
are separated by CR5 and CR6 and the pre-regulator/battery outputs are
combined by CR8 and CR9. The only problem with the existing circuit is
with a fresh, strong, fully charged battery pack, charging pulses will leak
past CR8 with only R1/C1 to filter them.
Ah, I did not see that A1S1A is the same as switch A1S1B; I am used to
seeing a little dashed line connecting all of the elements of a single
switch. I guess that goes along with the symbol they used for
constant current diode CR10 which I have not seen in a long time.
Anyway, the changes I suggested still apply. Actually, using a
battery which accepts a constant voltage charge simplifies the
requirements.
If they are integrated with the device, the manufacturer must certify they
have tested the device and proved it can not cause a fire. If you change the
NiCd battery to a LiFe system, you will fail that requirement. When you
ship, you must certify there is no hazmat item in your package. There is a
minimum Wh capacity allowed but I am not sure what it is. Not much from
memory.
----- Original Message -----
From: "David" davidwhess@gmail.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Wednesday, August 03, 2016 5:29 PM
Subject: Re: [volt-nuts] fluke 731b battery pack
Does that restriction apply to batteries which are integrated with a
device? I thought it only applied to separate cells.
On Wed, 03 Aug 2016 17:20:00 -0400, you wrote:
I like the LiFe idea except for the restrictions on shipping by air or
USPS.
That shouldn't be too much of a problem for most that have access to a
local
cal lab.
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If even with a fully charged pack the batt charge side gets high enough
to feed into the ref you need to check the current value of the current
limiting resistor in the charge circuit.
Don't have the exact details in my head at the moment (was about 3 years
ago) but in both of my 731Bs that resistor had dropped in value by more
than a little and was floating the batteries at a higher voltage. I
replaced with a correct value over-rated metal film type and no more
issue, max floating voltage for ~ C/20 maint to the pack is below cutoff.
If it is climbing high enough compared to the other feed, then resistors
have drifted and the batt circuit is running to hot or the filter AC ->
ref supply is running too low.
On 8/3/16 13:30, Orin Eman wrote:
On Wed, Aug 3, 2016 at 2:08 PM, David davidwhess@gmail.com wrote:
I looked at the schematic and is seems feasible without excessive
effort. Either the existing simple series preregulator can be
modified or replaced allowing it to both charge the battery (through a
blocking diode) and power the instrument or a completely separate
power charging circuit can be added in parallel.
The existing charging circuit is in parallel with the pre-regulator; they
are separated by CR5 and CR6 and the pre-regulator/battery outputs are
combined by CR8 and CR9. The only problem with the existing circuit is
with a fresh, strong, fully charged battery pack, charging pulses will leak
past CR8 with only R1/C1 to filter them.
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and follow the instructions there.