Panasonic BR-2/3A chemistry change - Page 1
Forum section: electronics / projects

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: October 14, 2019, 03:10:16 pm
content: I was looking into replacement of the battery in HP3457A. In my meter there is a Panasonic Lithium BR-2/3A with date code 2612 measuring 3.45 V. After some googling here on the forum I find two really annoying things:It seems Panasonic changed the chemistry of the battery at some point from Lithium Thionyl Chloride with nominal voltage of 3.5V to Lithium Polycarbon Monofluoride with nominal voltage of 3Vwithout changing the part numberTheir date code has the form YMWD, where Y is only a single digit. So no way to tell which decade the battery was made in.For a battery whose primary purpose is to maintain voltage for more than a decade, that makes perfect senseSo, if the battery reads around 3V, it can either be totally new or 20 years old and about to die.

author: duak
author_rank: Super Contributor
timestamp: October 14, 2019, 06:31:31 pm
content: I help out a friend who owns a CNC machine shop where the machine controls use lithium batteries of various types. The 2/3A size is also called a "PLC backup battery". SAFT still makes the 3.6 V type:https://www.onlybatteries.com/showitem.asp?ItemID=18594.148I don't know if it's still a pain to get unusual lithium batteries because of air cargo limitations. One 6 V battery would only last a year and at over $100 a pop was cheaper to replace with four D alkaline cells.

author: tooki
author_rank: Super Contributor
timestamp: October 14, 2019, 08:27:12 pm
content: Quote from: maxwell3e10 on October 14, 2019, 03:10:16 pmNot a chance. There is no way (and I do meanzero) that they would make such a change without a different part number. Above all, the BR prefix for batteries with lithium carbon monofluoride chemistry is not a random Panasonic product code, butan IEC standard. By definition, a BR battery (regardless of manufacturer) is a lithium carbon monofluoride battery. An ER battery is a lithium thionyl chloride type, which I can't find any evidence of Panasonic ever manufacturing. And it definitely would make no sense whatsoever to make such a major change without changing part numbers, since that would screw up all kinds of things.I suspect you're just reading a high open circuit voltage on a healthy cell. Every single mention of the HP3457A battery is of a 3V type. Between that and the nonexistence of Panasonic lithium thionyl chloride batteries, it's fair to say that your meter's 3V battery is still perfectly fine.Lithium thionyl chloride is nominal 3.6V (though a handful of vendors call it 3.7V), by the way, not 3.5V.

author: floobydust
author_rank: Super Contributor
timestamp: October 14, 2019, 09:15:27 pm
content: All the Panasonic lithium batteries seem to be only 3V ? Cataloguehttps://industrial.panasonic.com/cdbs/www-data/pdf/AAA4000/AAA4000COL32.pdfTadiran TL-49552/3AA is 3.6V like all of their cells.Don't forget lithium primary batteries have a passivation layer. An unused battery will read low in voltage "voltage delay" until that layer is consumed, then terminal voltage climbs up to normal. I put a resistor dummy load on a cell for a minute until the voltage stays up.So you can't always rely on terminal voltage to tell you the battery's state.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: October 14, 2019, 10:10:47 pm
content: Quote from: tooki on October 14, 2019, 08:27:12 pmLook at this threadhttps://www.eevblog.com/forum/beginners/changing-battery-in-a-hp-3478a-can-i-use-a-3v-lithium/?allMy battery looks exactly like this.Also, if you notice the mounting tabs are oriented in such a way that when the battery is soldered in, its impossible to see the part number. In that thread the old battery was measured to be 3.417V. In a teardown video of HP3478 Dave measured another one of these to be 3.49V. These voltages seem too high for a lithium carbon monofluoride.If I look at all the plots shown for Panasonic BR batteries, they all give output voltages around 3V.https://industrial.panasonic.com/ww/products/batteries/primary-batteries/lithium-batteries/cylindrical-type-lithium-batteries-br-series/BR-2%252F3APerhaps the chemical formulation was changed in some subtle way, so for recent batteries the starting voltage is closer to 3V.Actually if someone has a new fresh BR 2/3A battery, it would be interesting to measure with a high-impedance meter to see what the no-load voltage of a recently-made battery.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: October 14, 2019, 11:13:02 pm
content: Found this document that shows that BR 2/3A cells manufactured in 1990 had a mean starting voltage of 3.4 V.Also shows longevity of >20 years with small load current and relatively slow decay with larger current. So it seems if the battery measures over 3V, it is not in danger of imminent death.

author: tooki
author_rank: Super Contributor
timestamp: October 15, 2019, 12:12:30 am
content: Quote from: maxwell3e10 on October 14, 2019, 11:13:02 pm...and in extended storage, the voltage wentup. The 10uA current draw in the meter is so low that it might actually behave more like an open circuit. In other words, I see no evidence whatsoever that that voltage is uncharacteristic for the BR type battery, contrary to your claim in an earlier reply.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: October 15, 2019, 02:05:52 am
content: Well, the problem is that all the recent data sheets for these cells show only voltages of 3V, for example these:And with a date code uncertain about the decade, one can still equally well have an old battery with 3V which indicates it is about to die or a new one with 3V that is just fine.

author: tooki
author_rank: Super Contributor
timestamp: October 15, 2019, 11:11:19 am
content: Quote from: maxwell3e10 on October 15, 2019, 02:05:52 amAll that means is that they're not specifying its voltage below a 10µA load. But also, the first graph is showing the voltageat 50% discharge, not fresh!The second one is irrelevant since it pertains to a button cell, with a load 1/8 the size of yours.Quote from: maxwell3e10 on October 15, 2019, 02:05:52 amYou could put a higher load on it to see how much it drops. But if the first graph is to be believed, then at the 10µA load the meter is specified at, the voltage at 50% at 20C will beunder3V. So if you're seeing 3V, it's still got plenty of life left.I think you're overthinking this, and jumping to conclusions that just aren't justified by the information.

author: dom0
author_rank: Super Contributor
timestamp: October 15, 2019, 12:44:14 pm
content: I don't think it matters whether this is a 3 V or 3.6 V (nominal) battery in this application.QuoteCell-to-cell variation and the relatively fast degradation at end of life means measuring the cell voltage to decide whether to replace it is not such a good idea. These should be replaced by date code. (Although they normally exceed the replacement interval by a big margin, which is probably because manufacturers don't guarantee low-current performance and designers being cautious. In my 3478A the SRAM battery was some 30 years old and was still good. I replaced it, of course.)

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: October 15, 2019, 01:40:10 pm
content: Quote from: dom0 on October 15, 2019, 12:44:14 pmThis is exactly the problem. What is cell-to-cell variation? The plot from 1990 shows fairly small scatter with a mean of 3.38V. What is the initial open cell voltage of more recent cells? I couldn't find any comparable histogram in recent datasheets, but they suggest around 3 V. What was the voltage of the new battery that you put into 3478A?The date code is also uncertain as to thedecadewhen the battery was made.On the other hand, the data above show that the degradation is not so fast. With 10 uA current it takes years for it to drop. So it seems checking the battery every few years would be sufficient and in most cases a replacement is not necessary even after >20 years.

author: dom0
author_rank: Super Contributor
timestamp: October 15, 2019, 02:24:40 pm
content: Instrument built 1983. The battery in it when I received it has obviously been replaced at least once; it was a Eternacell SDX datecode B9511 (week 11, 1995); consistent with the 10 year or so replacement interval. That cell is sitting at 3.032 V right now. The replacement cell is a Varta 3 V Lithium (Made in Germany, surprisingly), which is at 3.272 V.Since the battery is outguard, you can simply use the multimeter to measure it's own SRAM battery voltage. 30 V range represents a 10 MΩ load.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: October 15, 2019, 05:00:54 pm
content: Eternalcell has more sensible date code. I believe that my Panasonic BR-2/3A with date code 2612 is from 1992, simply because most other components in the multimeter are from 1992. I suppose if someone had a rigorous calibration schedule (as many big companies do), it could have been replaced in 2002 or 2012. But there is no evidence of it being desoldered.Also there are subtle marking differences. Sometime before 2000 they added "Do not recharge" warning and around 2010 batteries started to have black background for the battery name.Anyone has a recent Panasonic BR-2/3A to measure the voltage?

author: pe2ben
author_rank: Contributor
timestamp: May 07, 2023, 02:41:41 pm
content: mine was only 3 volt and after installation in the 3457a it drops to 2.85 volt (Old stock maybe)Now i wil try Saft Lithium Thionyl Chloride 3.6V, 2/3 A 2/3 A Battery ordered by RS