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#21
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LiFePO4 batteries
On 10/11/2012 7:05 PM, Uncle Fuzzy wrote:
On Thursday, October 11, 2012 3:10:36 PM UTC-7, JohnDeRosa wrote: On Wednesday, October 10, 2012 9:04:15 PM UTC-5, Uncle Fuzzy wrote: "His charging system is a piece of lamp cord cut to a length that delivers his desired charge current." Huh? The wire length limits the charge current? I may be dense but you are going to have to explain this to me a bit more. Wire has resistance, enough wire (his cord is approximately 30 feet long)has enough resistance to drop the charge current to his target 10 amps. That's an extrememly mild charge rate for an A123 cell pack that will happily discharge at 80 amps. Was that cheaper than buying a charger? Even if the wire was free, I think it'd be safer and cheaper in the long run to buy a charger that was smarter than a piece of wire. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) |
#22
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LiFePO4 batteries
At 22:10 11 October 2012, JohnDeRosa wrote:
On Wednesday, October 10, 2012 9:04:15 PM UTC-5, Uncle Fuzzy wrote: "His charging system is a piece of lamp cord cut to a length that delivers his desired charge current." Huh? The wire length limits the charge current? I may be dense but you are going to have to explain this to me a bit more. How else would you control current other than with an appropriate length/size of wire? You can if you wish coil it and package it and call it a resistor. |
#23
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LiFePO4 batteries
On 10/13/2012 1:45 AM, Don Johnstone wrote:
At 22:10 11 October 2012, JohnDeRosa wrote: On Wednesday, October 10, 2012 9:04:15 PM UTC-5, Uncle Fuzzy wrote: "His charging system is a piece of lamp cord cut to a length that delivers his desired charge current." Huh? The wire length limits the charge current? I may be dense but you are going to have to explain this to me a bit more. How else would you control current other than with an appropriate length/size of wire? You can if you wish coil it and package it and call it a resistor. Perhaps he is able and willing to stand by the battery and monitor the process, but I'd rather buy a charger: it could regulate the current, measure the amp hours delivered, and shut down automatically when the battery is fully charged or the time has run out. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)nz |
#24
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LiFePO4 batteries
I'm still having trouble with the concept of charging a battery with AC
power. I saw no mention of a rectifier... Maybe he flip-flops the wires 60 times per second? "Eric Greenwell" wrote in message ... On 10/13/2012 1:45 AM, Don Johnstone wrote: At 22:10 11 October 2012, JohnDeRosa wrote: On Wednesday, October 10, 2012 9:04:15 PM UTC-5, Uncle Fuzzy wrote: "His charging system is a piece of lamp cord cut to a length that delivers his desired charge current." Huh? The wire length limits the charge current? I may be dense but you are going to have to explain this to me a bit more. How else would you control current other than with an appropriate length/size of wire? You can if you wish coil it and package it and call it a resistor. Perhaps he is able and willing to stand by the battery and monitor the process, but I'd rather buy a charger: it could regulate the current, measure the amp hours delivered, and shut down automatically when the battery is fully charged or the time has run out. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)nz |
#25
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LiFePO4 batteries
On Thursday, October 11, 2012 7:25:17 PM UTC-7, wrote:
My K2 w/o BMS has just two terminals just like any Pb acid, so I don't see how a charger can monitor each cell. I also don't know what a balance plug is, so I'll stop commenting. I'm just relaying what K2 and B-T Jr. told me. Okay, perhaps when they assemble/manufacture these batteries they ensure the cells are very well matched. The typical A123 and LiFe batteries used in RC have a special plug, often a JST-XH/(JR in the case of ElectroDynamics) type that allows the cells to be balance charged when using a capable charger. It is an absolute must in the case of Lipos (for safety)but with Life/LifePo/A123 you can get away without balance charging to some degree. |
#26
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LiFePO4 batteries
On Saturday, October 13, 2012 1:17:23 PM UTC-7, Dan Marotta wrote:
I'm still having trouble with the concept of charging a battery with AC power. I saw no mention of a rectifier... Maybe he flip-flops the wires 60 times per second? "Eric Greenwell" wrote in message Okay, now I see your confusion. Based on a lack of information in my post. My mistake. He's connecting his 3 cell LiFePo to a car battery, using the 30(ish) feet of zip cord as a dropping resistor (I just talked to him today, last year he got fancy and added a springwound cutoff timer). I was just trying to point out that the A123 cells are pretty robust, and while using the recommended charger and charge profile will likely lead to the longest possible life of your LiFePo batteries, he's been beating the hell out of the same 3 battery packs for 2+ years now, and has subjected them to more cycles than I would be able to put on a battery used in my glider in 5 years. ... On 10/13/2012 1:45 AM, Don Johnstone wrote: At 22:10 11 October 2012, JohnDeRosa wrote: On Wednesday, October 10, 2012 9:04:15 PM UTC-5, Uncle Fuzzy wrote: "His charging system is a piece of lamp cord cut to a length that delivers his desired charge current." Huh? The wire length limits the charge current? I may be dense but you are going to have to explain this to me a bit more. How else would you control current other than with an appropriate length/size of wire? You can if you wish coil it and package it and call it a resistor. Perhaps he is able and willing to stand by the battery and monitor the process, but I'd rather buy a charger: it could regulate the current, measure the amp hours delivered, and shut down automatically when the battery is fully charged or the time has run out. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)nz |
#27
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LiFePO4 batteries
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