Re: Fluke 732B battery float voltage

[kkayser]

The float voltage on my732B is 14.6, which is over the ideal  13.6 to 13.8.  Does anyone know how to reduce the maintenance voltage?

I have had battery problems with my 732B.  The latest battery failed at 5 months causing me to lose a recent calibration.  All SLA batteries are now made in ASIA.  I suppose the best we can do is test the battery before shipping the unit.  If anyone knows of an SLA battery not made in Asia, please let us know.


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[Bill158]

The float voltage on my732B is 14.6, which is over the ideal  13.6 to 13.8.  Does anyone know how to reduce the maintenance voltage?

I have had battery problems with my 732B.  The latest battery failed at 5 months causing me to lose a recent calibration.  All SLA batteries are now made in ASIA.  I suppose the best we can do is test the battery before shipping the unit.  If anyone knows of an SLA battery not made in Asia, please let us know.


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Question?  Does the "CHARGE" led come on after the power mains have been disconnect for a while and then reconnected to the mains?  Is the "CHARGE" led on all the time even after a reasonable charge time?  If yes, then IMHO your problem is that the charging circuit is not switching over, at 14.6 volts, from the constant current mode to the constant voltage mode.  I had this problem with my 732B when I first got it, used of course, and probably why it was on fleabay.  My trip point was set over 15.1V and of course would not ever change over.  I had to change a resistor in the circuit that sets the trip point for change over from constant I to constant V.  I can't remember which resistor I changed but I can look if this is the symptom of your high 14.6 voltage problem.  Once the trip point was occurring correctly my float voltage is 13.7V.

Bill

[kkayser]

The charging circuit works correctly.  I can't tell you the trip point, but it is over 14.6 volts.  The battery charges on constant current with the voltage rising slowly. Then, the voltage rapidly rises to over 14.6, then drops to 14.6 and stays there indefinitely. 

[ManateeMafia]

I started using this battery http://www.digikey.com/product-search/en?keywords=p682-nd

I looked through datasheets and Panasonic seemed to have the best choice for me. Only time will tell but so far the last three are working fine. The faston tab is the 0.187 size and the correct battery pn should be LC-P127R2P1 (0.250).
It will be difficult to find batteries not made in Asia, so I depend on name brand batteries not sold by Batteries Plus. For me it is Panasonic or BB Battery.

[Gyro]

I'm sure I've seen this problem discussed before, maybe a couple of years ago - It was something to do with a factory resistor mod on the PCB if I remember correctly. A detailed search may turn something up.

EDIT: Ah ha, Found it! https://www.eevblog.com/forum/testgear/fluke-732b-repair/

[ManateeMafia]

I have looked at a couple of different charger pcb's. One is marked rev F and the other M. The writing is faint but that is what my eyes are telling me. The F board has parts dated '94 and the other '97. There are obvious differences between the two and I will get some pics made to show them. The first thing I noticed is the DB-9 connector. The old one is all plastic while the newer one has the metal shield. Neither one has the axial capacitor mod installed.

I will check out a few other chargers looking for the mod and also see if I can spot the two resistors that were also changed.

[ManateeMafia]

These are my first two boards. I will still need to see if I have any other versions.

[ManateeMafia]

My rev F is behaving the same as kkayser's board. The rev M works as described in the 732B manual.

I compared both boards last night by measuring each resistor in the charger section and comparing them to the schematic. There were only two resistors that were different as mentioned by kkayser in the other thread linked above.

They are R506 and R520. On the rev F board R506 = 1.54K and R520 = 20.5K. The rev M board has R506 = 1.33K and R520 = 18.12K. All measured values were pretty close to their marked values. The rev M board also has a 1uF cap installed and not bodged in place. The connections match that of the schematic.

I have some parts on order from Digikey and they should arrive this weekend. I plan on swapping out R506 and R520 plus installing a C541. I will update this thread once I test it out. The parts I ordered are 1.33KXBK-ND, CMF18.2KQFCT-ND, and 338-3910-ND.

[aronake]

I started using this battery http://www.digikey.com/product-search/en?keywords=p682-nd

I looked through datasheets and Panasonic seemed to have the best choice for me. Only time will tell but so far the last three are working fine. The faston tab is the 0.187 size and the correct battery pn should be LC-P127R2P1 (0.250).
It will be difficult to find batteries not made in Asia, so I depend on name brand batteries not sold by Batteries Plus. For me it is Panasonic or BB Battery.

It seems Panasonic have stopped producing suitable lead acid batteries.

What could be a good high quality alternative?

[ManateeMafia]

I have been ordering these...

https://www.digikey.com/en/products/detail/b-b-battery/BC7-12-T2/10478930