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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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2 Lithium Manganese Dioxide cells in parallel. ?
Well nearly , the 2 negatives joined and 2 epitaxial diodes (avoiding mutual
discharge possibility) from the positives commoned and then on to the memory, is there some circuitwise reason? Both cells are from the same batch , so not as though "all your eggs in one basket" circumvention. Is the chemistry of this type of cell odd? 3V cells originally , could be 20 years, but removed from the pcb and out of circuit still 3V. Put 150K across either cell and it drops in voltage to 2.9V or so compared to just DVM loading. Remove and immediately recovers to 3V. Tried 5K6 over for 12 hours , dropped to 2.6V , measured a few minutes ago, removed the R and immediately recovered to 2.9V, I expect when I get back to it , it will be back to 3V with just DVM load |
#2
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2 Lithium Manganese Dioxide cells in parallel. ?
I'm not sure what your question is. Or if you have a question.
3V lithium coin cells are commonly used to back up memory, including 5V systems. They can last for years; I've never seen two used to add capacity. I have no idea why such a light load (150K) would cause the voltage to immediately drop by 3%. |
#3
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2 Lithium Manganese Dioxide cells in parallel. ?
William Sommerwerck wrote in message
... I'm not sure what your question is. Or if you have a question. 3V lithium coin cells are commonly used to back up memory, including 5V systems. They can last for years; I've never seen two used to add capacity. I have no idea why such a light load (150K) would cause the voltage to immediately drop by 3%. I've only ever seen a single cell or if multiple ones, then in series. On first confronting , much confusion. Realised they were tied together but not realised in parallel. Each one measured 3V , in turn, but put the DVM over the other 2 ends then near enough 0V, scatching head. Put DVM on resistance scale and measured a varying low resistance of 20 to 60 ohms , varying slowly like across a large C capacitor , but no large capacitors present. The approximately 0 ohms between 2 nearly equal 3V cells was being interpreted as low ohms. When I get replacement cell/cells? (why spend out on 2 ?) I'll try the 5K6 over night and see what effect on a known good cell , or at least new from the supplier. These cells were 1/2AA size Sanyo CR14250SE if that is relevant, ie not the usual PC large button cells |
#4
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2 Lithium Manganese Dioxide cells in parallel. ?
"William Sommerwerck" wrote in message ... I'm not sure what your question is. Or if you have a question. 3V lithium coin cells are commonly used to back up memory, including 5V systems. They can last for years; I've never seen two used to add capacity. I've never seen 2 cells used as memory backup either. My initial thoughts were that the two cells are wired in an OR configuration, meaning designed in redundancy rather than a need for an increase in capacity. Should one cell fail, the other will keep the memory intact. Is this equipment from the Space Shuttle by any chance? Gareth. |
#5
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2 Lithium Manganese Dioxide cells in parallel. ?
Gareth Magennis wrote: "William Sommerwerck" wrote in message ... I'm not sure what your question is. Or if you have a question. 3V lithium coin cells are commonly used to back up memory, including 5V systems. They can last for years; I've never seen two used to add capacity. I've never seen 2 cells used as memory backup either. My initial thoughts were that the two cells are wired in an OR configuration, meaning designed in redundancy rather than a need for an increase in capacity. Should one cell fail, the other will keep the memory intact. Is this equipment from the Space Shuttle by any chance? We had to use CapStore RAM in the equipment we built for NASA. No lithium batteries were allowed into space. Maybe they wanted to be able to replace the batteries one at a time, without losing what was stored in the RAM. |
#6
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2 Lithium Manganese Dioxide cells in parallel. ?
Michael A. Terrell wrote in message
m... Gareth Magennis wrote: "William Sommerwerck" wrote in message ... I'm not sure what your question is. Or if you have a question. 3V lithium coin cells are commonly used to back up memory, including 5V systems. They can last for years; I've never seen two used to add capacity. I've never seen 2 cells used as memory backup either. My initial thoughts were that the two cells are wired in an OR configuration, meaning designed in redundancy rather than a need for an increase in capacity. Should one cell fail, the other will keep the memory intact. Is this equipment from the Space Shuttle by any chance? We had to use CapStore RAM in the equipment we built for NASA. No lithium batteries were allowed into space. Maybe they wanted to be able to replace the batteries one at a time, without losing what was stored in the RAM. For the same reason that Boeing should have stopped them being incorporated on their recent product fiasco? Both batteries are tanged and would require desoldering/soldering to replace either. If designed to allow one failure then I'd expect at least for them to be from different batches if not different suppliers, both same make and batch number here |
#7
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2 Lithium Manganese Dioxide cells in parallel. ?
N_Cook wrote: Michael A. Terrell wrote in message m... Gareth Magennis wrote: "William Sommerwerck" wrote in message ... I'm not sure what your question is. Or if you have a question. 3V lithium coin cells are commonly used to back up memory, including 5V systems. They can last for years; I've never seen two used to add capacity. I've never seen 2 cells used as memory backup either. My initial thoughts were that the two cells are wired in an OR configuration, meaning designed in redundancy rather than a need for an increase in capacity. Should one cell fail, the other will keep the memory intact. Is this equipment from the Space Shuttle by any chance? We had to use CapStore RAM in the equipment we built for NASA. No lithium batteries were allowed into space. Maybe they wanted to be able to replace the batteries one at a time, without losing what was stored in the RAM. For the same reason that Boeing should have stopped them being incorporated on their recent product fiasco? Both batteries are tanged and would require desoldering/soldering to replace either. If designed to allow one failure then I'd expect at least for them to be from different batches if not different suppliers, both same make and batch number here I am taking about tiny coin cell sized lithium batteries that were used in battery backed RAM and Real Time Clock modules. NASA stated that if they failed, Lithium could contaminate the atmosphere inside the ISS. |
#8
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2 Lithium Manganese Dioxide cells in parallel. ?
I'm taking about lithium coin cells used in battery-backed
RAM and real-time clock modules. NASA said that if they failed, lithium could contaminate the atmosphere. NASA was "nuts" about such things. It was worried about outgassing from the rubber feet on HP calculators. These were removed. |
#9
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2 Lithium Manganese Dioxide cells in parallel. ?
Michael A. Terrell wrote:
N_Cook wrote: Michael A. Terrell wrote in message m... Gareth Magennis wrote: "William Sommerwerck" wrote in message ... I'm not sure what your question is. Or if you have a question. 3V lithium coin cells are commonly used to back up memory, including 5V systems. They can last for years; I've never seen two used to add capacity. I've never seen 2 cells used as memory backup either. My initial thoughts were that the two cells are wired in an OR configuration, meaning designed in redundancy rather than a need for an increase in capacity. Should one cell fail, the other will keep the memory intact. Is this equipment from the Space Shuttle by any chance? We had to use CapStore RAM in the equipment we built for NASA. No lithium batteries were allowed into space. Maybe they wanted to be able to replace the batteries one at a time, without losing what was stored in the RAM. For the same reason that Boeing should have stopped them being incorporated on their recent product fiasco? Both batteries are tanged and would require desoldering/soldering to replace either. If designed to allow one failure then I'd expect at least for them to be from different batches if not different suppliers, both same make and batch number here I am taking about tiny coin cell sized lithium batteries that were used in battery backed RAM and Real Time Clock modules. NASA stated that if they failed, Lithium could contaminate the atmosphere inside the ISS. burst lithium cells do smell truly awful. those things are up there in space though, so maybe nasa has exceptions, or just doesn't care about all of them. |
#10
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2 Lithium Manganese Dioxide cells in parallel. ?
William Sommerwerck wrote:
I'm taking about lithium coin cells used in battery-backed RAM and real-time clock modules. NASA said that if they failed, lithium could contaminate the atmosphere. NASA was "nuts" about such things. It was worried about outgassing from the rubber feet on HP calculators. These were removed. well, rubber does outgas, crappier types more than others, but how do you know which is which? It seems like an odd but sensible thing to do. |
#11
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2 Lithium Manganese Dioxide cells in parallel. ?
Cydrome Leader wrote: Michael A. Terrell wrote: I am taking about tiny coin cell sized lithium batteries that were used in battery backed RAM and Real Time Clock modules. NASA stated that if they failed, Lithium could contaminate the atmosphere inside the ISS. burst lithium cells do smell truly awful. those things are up there in space though, so maybe nasa has exceptions, or just doesn't care about all of them. Not all of the electronics are in living or working spaces. |
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