[volt-nuts] fluke 731b battery pack
Most NiMH cells have a capacity of around twice what a NiCad has, so a NiCad charger that works at a C/10 charge rate will be charging NiMH cells at C/20. That can be an acceptable trickle rate for NiMH cells, but I prefer something in the C/40 neighborhood. I put some in an electric shaver (really crude charger) and they last longer than NiCads. Proper low self discharge NiMh cells have about 1/10th the self-discharge rate of NiCads. I have some in some test equipment that seldom gets used and after over a year of storage were still going strong and provided hours of run time. NiCads would be dead after a couple of months of storage. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] fluke 731b battery pack
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" To: "Discussion of precise voltage measurement" 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. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] fluke 731b battery pack
Eric wrote: NiMH cells seem to work in the 731b so I'd prefer to use them over NiCd because of the higher capacity and lower toxicity of potential leaks. Is there a downside to doing this? In my experience, good NiCDs are preferable to NiMHs. Good NiCds have substantially lower self-leakage than NiMHs (this is true even of the "NEW!! Low-discharge!!" NiMHs). NiCds also don't degrade nearly as fast if they are left too long on trickle charge. Both of these features translate directly into increased life for the NiCds. NiCds are also quieter, and capable of larger current drains, due to their lower internal (series) resistance (high current is not really an issue in your application). Consumer-type NiCds may suffer from the problem PHK noted (poor quality due to low production volumes), but there are still many industrial and military applications that specify NiCDs for some or all of the reasons given above. Excellent NiCds are readily available -- just look for aerospace-grade parts rather than consumer batteries. Many built-in charging circuits are crude and leave the batteries on a trickle current that is really too high, particularly given the temperatures inside electronic instruments. So whichever batteries you choose, plan on redesigning the charging circuit. That brings up the possibility of using either LiFePO4 or SLA (sealed lead-acid) batteries -- if you have to redesign the charging circuit anyway, you can just as easily design it for LiFePO4 or SLA. I have not evaluated the 731B power supply in particular, but LiFePO4 would be my presumptive choice unless I encountered an insurmountable obstacle. Best regards, Charles ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] fluke 731b battery pack
On Wed, 3 Aug 2016 14:30:33 -0700, you wrote: >On Wed, Aug 3, 2016 at 2:08 PM, David 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. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] fluke 731b battery pack
On Wed, Aug 3, 2016 at 2:08 PM, David 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. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
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. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] fluke 731b battery pack
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. - Original Message - From: "David" To: "Discussion of precise voltage measurement" Sent: Wednesday, August 03, 2016 5:08 PM Subject: Re: [volt-nuts] fluke 731b battery pack On Wed, 3 Aug 2016 16:34:31 -0400, you wrote: Eric wrote: NiMH cells seem to work in the 731b so I'd prefer to use them over NiCd because of the higher capacity and lower toxicity of potential leaks. Is there a downside to doing this? In my experience, good NiCDs are preferable to NiMHs. Good NiCds have substantially lower self-leakage than NiMHs (this is true even of the "NEW!! Low-discharge!!" NiMHs). NiCds also don't degrade nearly as fast if they are left too long on trickle charge. Both of these features translate directly into increased life for the NiCds. NiCds are also quieter, and capable of larger current drains, due to their lower internal (series) resistance (high current is not really an issue in your application). That is my experience as well however I do like the better low discharge NiMH cells. Some are better than other though. Consumer-type NiCds may suffer from the problem PHK noted (poor quality due to low production volumes), but there are still many industrial and military applications that specify NiCDs for some or all of the reasons given above. Excellent NiCds are readily available -- just look for aerospace-grade parts rather than consumer batteries. Low leakage and high temperature NiCd cells seem to last a lot longer than other types and you will not find any consumer versions of these but the price is high. Many built-in charging circuits are crude and leave the batteries on a trickle current that is really too high, particularly given the temperatures inside electronic instruments. So whichever batteries you choose, plan on redesigning the charging circuit. That brings up the possibility of using either LiFePO4 or SLA (sealed lead-acid) batteries -- if you have to redesign the charging circuit anyway, you can just as easily design it for LiFePO4 or SLA. I have not evaluated the 731B power supply in particular, but LiFePO4 would be my presumptive choice unless I encountered an insurmountable obstacle. Best regards, Charles 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 difficulty of maintaining charge in a backup application using NiMH cells would lead me to consider LiFePO4 cells instead. The only serious difficulty would be preventing excessive discharge which will ruin a lithium (or PbSO4) based rechargeable battery in short order. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] fluke 731b battery pack
The battery in the 731B is charged via a diode and 510 ohm resistor from the rectified DC, before the smoothing capacitor. The smoothing capacitor and power supply is fed by another diode, so the battery is charged with a pulse waveform. If you have no battery, then this pulse charge waveform will get around the power supply regulator (since the regulated supply and battery are diode switched) and increase noise on the output. I therefore don't recommend running without a battery installed... (though you could remove CR5 or or R30). Even with the battery installed, if it's good, at full charge, you can still get charging pulses bypassing the regulator. I built a high-side switch to switch between the battery and power supply on my 731B. I got the local Batteries Plus to build a new battery pack. They usually have NiCd cells of the right size and will build a battery pack while you wait. With an NiCd pack so easily available, I saw no reason to change battery type. Orin. On Wed, Aug 3, 2016 at 1:34 PM, Charles Steinmetz wrote: > Eric wrote: > > NiMH cells seem to work in the 731b so I'd prefer to use them over NiCd >> because of the higher capacity and lower toxicity of potential leaks. Is >> there a downside to doing this? >> > > In my experience, good NiCDs are preferable to NiMHs. Good NiCds have > substantially lower self-leakage than NiMHs (this is true even of the > "NEW!! Low-discharge!!" NiMHs). NiCds also don't degrade nearly as fast if > they are left too long on trickle charge. Both of these features > translate directly into increased life for the NiCds. NiCds are also > quieter, and capable of larger current drains, due to their lower internal > (series) resistance (high current is not really an issue in your > application). > > Consumer-type NiCds may suffer from the problem PHK noted (poor quality > due to low production volumes), but there are still many industrial and > military applications that specify NiCDs for some or all of the reasons > given above. Excellent NiCds are readily available -- just look for > aerospace-grade parts rather than consumer batteries. > > Many built-in charging circuits are crude and leave the batteries on a > trickle current that is really too high, particularly given the > temperatures inside electronic instruments. So whichever batteries you > choose, plan on redesigning the charging circuit. > > That brings up the possibility of using either LiFePO4 or SLA (sealed > lead-acid) batteries -- if you have to redesign the charging circuit > anyway, you can just as easily design it for LiFePO4 or SLA. > > I have not evaluated the 731B power supply in particular, but LiFePO4 > would be my presumptive choice unless I encountered an insurmountable > obstacle. > > Best regards, > > Charles > > > > ___ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] fluke 731b battery pack
On Wed, 3 Aug 2016 16:34:31 -0400, you wrote: >Eric wrote: > >> NiMH cells seem to work in the 731b so I'd prefer to use them over NiCd >> because of the higher capacity and lower toxicity of potential leaks. Is >> there a downside to doing this? > >In my experience, good NiCDs are preferable to NiMHs. Good NiCds have >substantially lower self-leakage than NiMHs (this is true even of the >"NEW!! Low-discharge!!" NiMHs). NiCds also don't degrade nearly as fast >if they are left too long on trickle charge. Both of these features >translate directly into increased life for the NiCds. NiCds are also >quieter, and capable of larger current drains, due to their lower >internal (series) resistance (high current is not really an issue in >your application). That is my experience as well however I do like the better low discharge NiMH cells. Some are better than other though. >Consumer-type NiCds may suffer from the problem PHK noted (poor quality >due to low production volumes), but there are still many industrial and >military applications that specify NiCDs for some or all of the reasons >given above. Excellent NiCds are readily available -- just look for >aerospace-grade parts rather than consumer batteries. Low leakage and high temperature NiCd cells seem to last a lot longer than other types and you will not find any consumer versions of these but the price is high. >Many built-in charging circuits are crude and leave the batteries on a >trickle current that is really too high, particularly given the >temperatures inside electronic instruments. So whichever batteries you >choose, plan on redesigning the charging circuit. > >That brings up the possibility of using either LiFePO4 or SLA (sealed >lead-acid) batteries -- if you have to redesign the charging circuit >anyway, you can just as easily design it for LiFePO4 or SLA. > >I have not evaluated the 731B power supply in particular, but LiFePO4 >would be my presumptive choice unless I encountered an insurmountable >obstacle. > >Best regards, > >Charles 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 difficulty of maintaining charge in a backup application using NiMH cells would lead me to consider LiFePO4 cells instead. The only serious difficulty would be preventing excessive discharge which will ruin a lithium (or PbSO4) based rechargeable battery in short order. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] fluke 731b battery pack
NiMH does not do too well in float charge conditions and that is the main state a 731B will spend its time. Regards, Tom - Original Message - From: "Eric Garner" To: "Discussion of precise voltage measurement" Sent: Wednesday, August 03, 2016 1:27 PM Subject: [volt-nuts] fluke 731b battery pack So I managed to get one of the Fluke 731b's mentioned on the list a while back. It was a little more chewed up than the description in the auction led me to believe: https://plus.google.com/u/0/112871219575380932919/posts/iDWyzwYYRdj?pid=6314634305601690930&oid=112871219575380932919 but it appears to be functional. The NiCd pack appears to have leaked some time in the past and was removed, which is fine since I was going to replace the batteries anyway. Looking through the archives, replacement battery packs for the 731b has been a popular topic but I have some questions that remain open. 1. NiMH cells seem to work in the 731b so I'd prefer to use them over NiCd because of the higher capacity and lower toxicity of potential leaks. Is there a downside to doing this? 2. If I go with NiMH, is there a manufacturer that's prefered? reading reviews of NiMH cells online leads me to believe that some manufacturers (Tenergy) have lower quality and are less reliable. 3. If I go with NiCd would you expect problems if I used larger cells (4/5A vs 2/3A) thanks --Eric _ Eric Garner ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] fluke 731b battery pack
Are the low discharge NiMH cells available now any more rugged than regular NiCd cells as far as charging current? One solution I would consider is using LiFePO4 cells and modifying the charger for current limited constant voltage. On Wed, 03 Aug 2016 19:37:12 +, you wrote: > >In message >, Eric >Garner writes: > >I would go with NiMH, since the NiCd production volume of small >cells is now so low now that quality suffers. > >You need to pay serious attention to the charging circuit, no >matter which chemistry you pick. > >The trickle charge current is probably too high for modern NiCd and >guaranteed too high for NiMH. > >If there is a bulk charge state, you should check the parameters >(current/timer) of that too. > >Finally, try to measure the final config (ie: on the right shelf, >in the pile of kit) temperature of the battery pack, before >deciding/adjusting charging parameters, both NiCd and NiMH change >properties rapidly above approx 40C/100F. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] fluke 731b battery pack
Eric: I have been using NiMH AA batteries in my 731B for at least 15 years now. I am sure that the specs say don't use them in a circuit designed for NiCd but I haven't had any problems with over heating or overcharging. You have to do some mods to the battery mounting to get them in there but once done you are good for a lifetime. I have never checked to see how long the NiMH batteries would run for but my guess would be longer than the original NiCds. Bill - Original Message - From: "Eric Garner" To: "Discussion of precise voltage measurement" Sent: Wednesday, August 03, 2016 10:27 AM Subject: [volt-nuts] fluke 731b battery pack > So I managed to get one of the Fluke 731b's mentioned on the list a while > back. It was a little more chewed up than the description in the auction > led me to believe: > > https://plus.google.com/u/0/112871219575380932919/posts/iDWyzwYYRdj?pid=6314634305601690930&oid=112871219575380932919 > > but it appears to be functional. > > The NiCd pack appears to have leaked some time in the past and was removed, > which is fine since I was going to replace the batteries anyway. > > Looking through the archives, replacement battery packs for the 731b has > been a popular topic but I have some questions that remain open. > > 1. NiMH cells seem to work in the 731b so I'd prefer to use them over NiCd > because of the higher capacity and lower toxicity of potential leaks. Is > there a downside to doing this? > > 2. If I go with NiMH, is there a manufacturer that's prefered? reading > reviews of NiMH cells online leads me to believe that some manufacturers > (Tenergy) have lower quality and are less reliable. > > 3. If I go with NiCd would you expect problems if I used larger cells (4/5A > vs 2/3A) > > > > > thanks > > --Eric > _ > Eric Garner > ___ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] fluke 731b battery pack
In message , Eric Garner writes: I would go with NiMH, since the NiCd production volume of small cells is now so low now that quality suffers. You need to pay serious attention to the charging circuit, no matter which chemistry you pick. The trickle charge current is probably too high for modern NiCd and guaranteed too high for NiMH. If there is a bulk charge state, you should check the parameters (current/timer) of that too. Finally, try to measure the final config (ie: on the right shelf, in the pile of kit) temperature of the battery pack, before deciding/adjusting charging parameters, both NiCd and NiMH change properties rapidly above approx 40C/100F. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
[volt-nuts] fluke 731b battery pack
So I managed to get one of the Fluke 731b's mentioned on the list a while back. It was a little more chewed up than the description in the auction led me to believe: https://plus.google.com/u/0/112871219575380932919/posts/iDWyzwYYRdj?pid=6314634305601690930&oid=112871219575380932919 but it appears to be functional. The NiCd pack appears to have leaked some time in the past and was removed, which is fine since I was going to replace the batteries anyway. Looking through the archives, replacement battery packs for the 731b has been a popular topic but I have some questions that remain open. 1. NiMH cells seem to work in the 731b so I'd prefer to use them over NiCd because of the higher capacity and lower toxicity of potential leaks. Is there a downside to doing this? 2. If I go with NiMH, is there a manufacturer that's prefered? reading reviews of NiMH cells online leads me to believe that some manufacturers (Tenergy) have lower quality and are less reliable. 3. If I go with NiCd would you expect problems if I used larger cells (4/5A vs 2/3A) thanks --Eric _ Eric Garner ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
