Battery change for Fluke 732A DC standard?

[carl_lab]

Which battery (cells) do I need?
Is a there special procedure to follow?

[HighVoltage]

Did you buy this one from the ebay seller in the USA?

[carl_lab]

Did you buy this one from the ebay seller in the USA?

No. That's our calibration lab DC standard since many years (photo is stolen from www  ).
Why do you want to know?

[ManateeMafia]

Typically, you need 4 6v 4-5Ah SLA batteries. Some units were modified to take 2 12V 5Ah batteries.

The only problem I have had was that I purchased some Panasonic batteries where the tabs were too close to the edge of the body. This prevented me from using them safely without risking a short to the chassis. I ended using them for a BBU on my Z3801A.
https://www.digikey.com/short/3nqvn0

Also, try to use name brand batteries. I wasted a lot of money buying some at my local battery store. My DC electronic load proved these batteries couldn't meet their Ah rating by half the stated value.
I ended up modding my battery tray to take 12V batteries but there are issues going that route. You will need a nibbling tool and there will be left over space inside the tray that I fill with a spacer. It doesn't look pretty but I find it easier to manage considering I have several of these references.

I recently purchased a 732A. I can take pictures for you to show how easy it is. I don't think you need anything more than a phillips screwdriver.

Before I install the batteries, I charge them individually for several hours.

[HighVoltage]

Did you buy this one from the ebay seller in the USA?

No. That's our calibration lab DC standard since many years (photo is stolen from www  ).
Why do you want to know?

I was hoping someone here on eevblog would have bought one of these Fluke 732A references from the USA seller:
http://www.ebay.com/itm/Fluke-732A-VOLTAGE-Reference-STANDARD-/302176388032?hash=item465b1dc3c0:g:wKgAAOSwW6JYX5Om

He has sold 5 of 8 and it would be interesting to know how stable they are.
The batteries are probably empty and dead, I would guess.
Probably too risky to buy one of these.

[carl_lab]

Thanks for your reply Manatee and HV.

Changing procedure is
1) old batteries out
2) new in
3) resetting "in cal" indicator ?

[TiN]

I recently purchased a 732A. I can take pictures for you to show how easy it is.

I surely want those pictures. Let's have a 732A teardown thread, shall we? 

[carl_lab]

I recently purchased a 732A. I can take pictures for you to show how easy it is.

I surely want those pictures. Let's have a 732A teardown thread, shall we? 

Definitely... 

[ManateeMafia]

You got it.

It will be a repair / teardown of one of my older 732A. Luckily, I have several months of data to show how bad it is.

I will combine it with adjustments to the latest 732A.

[dacman]

It can take several months to recover if it has been powered down for awhile, but as long as it hasn't been frozen (with no battery or external power), it should be ok.  (The cargo hold is supposed to be heated on commercial aircraft.)

There is a manual at Fluke (search for Fluke 732A manual).

For battery replacement, power from acV, set the battery switch to OFF (or 0),  remove the screws that are in the corners of the battery module and pull it out, disconnect the battery terminals, remove the screws from all four sides near the bottom (the rear faceplate covers three screws near the bottom and should also be removed, although it has wires attached that will tether it), remove the top screws from the left side (the side without the wire attached) and remove the left side panel and bottom panel,  remove the batteries.  On the replacement batteries, bend all four black terminals and two red terminals up about 60 degrees (bend at the elbow, not at the exit).  On the other two batteries, bend one red terminal almost straight up and leave the other red terminal as-is.  Insert the battery with the factory bent red terminal against the back panel.  Install the battery with the red terminal bent almost straight up next to it, and install the other two batteries.  (Consider installing padding.)  Reinstall the panels.  Attach the battery terminals (crimp or replace any terminal that fits loosely).  Reinstall the module and set the battery switch to ON (or 1).  Monitor battery voltage from the rear terminals.  It should float between 27.0 and 27.6 Vdc after being fully charged.  (It can be near 28 or 29 Vdc when fast charging.)

[carl_lab]

Thank you for quoting exact procedure! 

[dacman]

To answer the first question, batteries it can use include an NP4-6, NP4.5-6, and NP5-6.  It takes four.  The battery with the Fluke part number (739961) is available, but it is expensive because it has been pre tested.  (The same battery is used by the Fluke 792A, which is still sold by Fluke.)

[Tony_G]

Resurrecting this thread as I've come into possession of a 732A without batteries.

I bought the same battery that Newark is showing as the Fluke part (P/N 739961 Genesis NP4-6) but when I put the batteries in the terminals touch the metal:



Before I break out the nibbler to create some more space I was wondering, for those of you that have replaced the batteries was there a "trick" to getting the tabs to have more clearance? Or is this a case that the genuine Genesis batteries I got are in fact not genuine?

Any guidance is appreciated.

Thanks,

TonyG

[Bill158]

Tony_G:
I have long ago nibbled out the battery tab holes.  I have used many, many brands of batteries and have found that some, could have been Genesis?, didn't fit and could short out.  I had one case where I think one of the batteries shorted out to the metal ( ground ) and caused a failure in the charging/float supply.  I also place a very short piece of heat shrink around the base of the tab ( 1/8" or maybe a little longer ) of each battery just to insure none of the tabs touch the metal.  I have also adjusted the change over from charging to float to be about 29.2 volts.  I have done this by trial and error.  Monitor the voltage across the battery pack and adjust the appropriate pot until the circuit changes over at about 29.2 volts, forget what the manual says about adjusting this.  Why 29.2 volts?  Because this comes from the spec sheets of the batteries.  7.3 volts per cell at the 0.4 A charging current that the 732A supplies.  Once the battery pack changes over from charging to float I give the pack a day on float and then set the float voltage to between 27.2 and 27.4 volts, again from the spec sheet 6.8 to 6.9 volts float across each cell.  Also keep a close eye on the battery pack when they are first installed and are on charging.  Some batteries simply won't reach the 29.2 volt peak and will continue to charge at .4 A and will overheat and fry themselves into early failure.  One easy way to force a change from charge to float is to simply use the battery pack switch.  With they power connected, put it in the "off" position for a few seconds and then back "on".  The supply will now be in float.  Then give the pack a day on float, pull the power plug for a second, plug back in and again monitor and see what happens and all the time it will rapidly rise to 29.2 V and then go into float.

I have found that no matter what brand, these batteries fail in about 2.5 to 3 years.  Usually one cell in one battery will not hold a charge.  Then replace all 4 at the same time!!!  I have friends that have tried the 12 v/ 5ah replacement.  Same results in failures.  One cell gives up in the same time period.  I have checked the float current and it meets specs.  I don't understand or pretend to understand when the spec sheet says something different about float and lifetime at floating.  I blame this on CCC.  But I have noticed that my favorite brand has changed manufacturing from China to Vietnam recently so I will wait for 3 years and see what happens.

The voice of experience,
Bill

[CalibrationGuy]

How about this battery:

https://www.amazon.com/Interstate-Batteries-Rechargeable-SLA0905-Terminal/dp/B000BPELKY?th=1

Would that fit? I have 2 732s that are due for battery changes.

TomG.

[Bill158]

How about this battery:

https://www.amazon.com/Interstate-Batteries-Rechargeable-SLA0905-Terminal/dp/B000BPELKY?th=1

Would that fit? I have 2 732s that are due for battery changes.

TomG.

Those should work just fine.  You will need to bend the tabs up to vertical to get the "fast on" connectors installed.   All of the batteries I have ever gotten have those tabs bent in the opposite direction and down against the red and black "filler" in the top of the battery.  The red tab in the battery that is at the rear of the holder needs to be about  a 45 degree angle to allow the "fast on" connector to fit under the on/off switch that is just above.  A little care here is all that is necessary.  Sometimes I have had to put a thin filler in between the batteries, front to back, so that they don't "wiggle" around.  Some of the batteries are slightly thinner in that direction.  I just want to make sure that they stay in place relative to the holes in the top of the plate.
Bill

[CalibrationGuy]

One of our 732a units has drifted less than .6ppm since October 2022. We do a Standards Lab Calibration at Keysight because they verify the 10 volt range with their JVS. Thanks for the reply.

TomG.