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#21
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K2 battery endurance
2G wrote on 5/25/2020 2:20 PM:
On Wednesday, May 13, 2020 at 8:00:09 PM UTC-7, kinsell wrote: .... The BMS in all LFPs may not have the same functionality regarding balancing but at the very least they should start/stop accepting charge appropriately. It matters not what you think should happen, the truth is not all LFP batteries have a BMS, and of those that do, not all of them protect from over and under voltage. Which LFP batteries don't have a BMS? Tom The "powersports" (ie, for engine starting) LFP don't always have a BMS. A motorglider pilot might be tempted to use one for the engine, for example. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 |
#22
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K2 battery endurance
One of my early K2's experienced a cell failure which dropped that battery's voltage output and lowered it's capacity. I run two batteries in parallel and had an experience like yours. Individual testing of each found the bad battery. Replacement is the only fix for this.
Battery testing can be done pretty easily and low tech. Using a voltmeter and 12V side marker lights from your local tractor supply. , 2-4 of the side marker lights should approximate your gliders normal electrical load. Plug them into the battery then check and record the voltage every half hour until it drops to 11.5V. You can measure amperage with most multi-meters, just be careful to switch the leads back to voltage measurement. The cheap meters are not fused. Had a guy blow one up checking 480V with an un-fused meter set to measure current. It can cause serious injury, so exercise caution. The batteries we use in sailplanes can deliver enough energy to melt things if shorted out, so respect that potential when dealing with them. We had to evacuate a 300,000 SQFT manufacturing facility once because a technician shorted out a single lithium Ion battery cell in his test stand, The smoke from off-gassing was impressive. SF |
#23
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K2 battery endurance
Testing is always good, but John has a very reasonable suspicion the
problem was due to cold soaking the batteries. LFP's really don't like the cold, and can even be damaged if charged below freezing. Maybe he had a temporary loss of capacity that wouldn't show up under room temp testing. On 5/30/20 8:50 AM, SF wrote: One of my early K2's experienced a cell failure which dropped that battery's voltage output and lowered it's capacity. I run two batteries in parallel and had an experience like yours. Individual testing of each found the bad battery. Replacement is the only fix for this. Battery testing can be done pretty easily and low tech. Using a voltmeter and 12V side marker lights from your local tractor supply. , 2-4 of the side marker lights should approximate your gliders normal electrical load. Plug them into the battery then check and record the voltage every half hour until it drops to 11.5V. You can measure amperage with most multi-meters, just be careful to switch the leads back to voltage measurement. The cheap meters are not fused. Had a guy blow one up checking 480V with an un-fused meter set to measure current. It can cause serious injury, so exercise caution. The batteries we use in sailplanes can deliver enough energy to melt things if shorted out, so respect that potential when dealing with them. We had to evacuate a 300,000 SQFT manufacturing facility once because a technician shorted out a single lithium Ion battery cell in his test stand, The smoke from off-gassing was impressive. SF |
#24
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K2 battery endurance
On Saturday, May 30, 2020 at 5:47:01 PM UTC-4, kinsell wrote:
Testing is always good, but John has a very reasonable suspicion the problem was due to cold soaking the batteries. LFP's really don't like the cold, and can even be damaged if charged below freezing. Maybe he had a temporary loss of capacity that wouldn't show up under room temp testing. LFPs don't like to be charged while cold (below the freezing point of water is the rule of thumb, even though they are not made of water). But they discharge just fine while (reasonably) cold. Their capacity while cold doesn't suffer anything like the way SLAs capacity does. |
#25
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K2 battery endurance
On Sunday, May 31, 2020 at 4:15:11 PM UTC+2, wrote:
On Saturday, May 30, 2020 at 5:47:01 PM UTC-4, kinsell wrote: Testing is always good, but John has a very reasonable suspicion the problem was due to cold soaking the batteries. LFP's really don't like the cold, and can even be damaged if charged below freezing. Maybe he had a temporary loss of capacity that wouldn't show up under room temp testing. LFPs don't like to be charged while cold (below the freezing point of water is the rule of thumb, even though they are not made of water). But they discharge just fine while (reasonably) cold. Their capacity while cold doesn't suffer anything like the way SLAs capacity does. FYI the capacity does still suffer somewhat, -20% at -10c, http://liionbms.com/pdf/kokam/SLPB10...0Ah%20Nano.pdf |
#27
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K2 battery endurance
On 5/25/20 9:47 PM, Eric Greenwell wrote:
2G wrote on 5/25/2020 2:20 PM: On Wednesday, May 13, 2020 at 8:00:09 PM UTC-7, kinsell wrote: ... The BMS in all LFPs may not have the same functionality regarding balancing but at the very least they should start/stop accepting charge appropriately. It matters not what you think should happen, the truth is not all LFP batteries have a BMS, and of those that do, not all of them protect from over and under voltage. Which LFP batteries don't have a BMS? Tom The "powersports" (ie, for engine starting) LFP don't always have a BMS. A motorglider pilot might be tempted to use one for the engine, for example. StarkPower had a series of batteries aimed at motorcycles that they were quite open about not having a BMS. Unfortunately they're in Chapter 7 now and the website is gone. More commonly, some batteries with BMS don't have over and under voltage protection. Richard Pfiffner one time was testing batteries, and his vendor shipped 24 volt chargers accidentally for 12 volt batteries. All the white stuff leaked out of the battery. Some electrical genius on R.A.S. (don't remember which one) declared that they really had overvoltage protection, but 24 volts just wasn't enough to trigger it. One of our fellow Schleicher motorglider pilots had an LFP, left the transponder on, and ruined the battery. A 15-20 AH battery intended as a starter battery can easily find it's way into other applications. You may have read about the ASG 32 mi that got fried when the solar controller malfunctioned, drained the battery, and got quite hot when charged from another charger. Did it have a BMS? Doesn't really matter. Dave |
#28
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K2 battery endurance
On Monday, June 1, 2020 at 9:46:09 PM UTC-7, kinsell wrote:
On 5/25/20 9:47 PM, Eric Greenwell wrote: 2G wrote on 5/25/2020 2:20 PM: On Wednesday, May 13, 2020 at 8:00:09 PM UTC-7, kinsell wrote: ... The BMS in all LFPs may not have the same functionality regarding balancing but at the very least they should start/stop accepting charge appropriately. It matters not what you think should happen, the truth is not all LFP batteries have a BMS, and of those that do, not all of them protect from over and under voltage. Which LFP batteries don't have a BMS? Tom The "powersports" (ie, for engine starting) LFP don't always have a BMS. A motorglider pilot might be tempted to use one for the engine, for example. StarkPower had a series of batteries aimed at motorcycles that they were quite open about not having a BMS. Unfortunately they're in Chapter 7 now and the website is gone. More commonly, some batteries with BMS don't have over and under voltage protection. Richard Pfiffner one time was testing batteries, and his vendor shipped 24 volt chargers accidentally for 12 volt batteries. All the white stuff leaked out of the battery. Some electrical genius on R.A.S. (don't remember which one) declared that they really had overvoltage protection, but 24 volts just wasn't enough to trigger it. One of our fellow Schleicher motorglider pilots had an LFP, left the transponder on, and ruined the battery. A 15-20 AH battery intended as a starter battery can easily find it's way into other applications. You may have read about the ASG 32 mi that got fried when the solar controller malfunctioned, drained the battery, and got quite hot when charged from another charger. Did it have a BMS? Doesn't really matter. Dave I think it matters: what kind of battery was it? Tom |
#29
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K2 battery endurance
On Monday, June 1, 2020 at 9:46:09 PM UTC-7, kinsell wrote:
On 5/25/20 9:47 PM, Eric Greenwell wrote: 2G wrote on 5/25/2020 2:20 PM: On Wednesday, May 13, 2020 at 8:00:09 PM UTC-7, kinsell wrote: ... The BMS in all LFPs may not have the same functionality regarding balancing but at the very least they should start/stop accepting charge appropriately. It matters not what you think should happen, the truth is not all LFP batteries have a BMS, and of those that do, not all of them protect from over and under voltage. Which LFP batteries don't have a BMS? Tom The "powersports" (ie, for engine starting) LFP don't always have a BMS. A motorglider pilot might be tempted to use one for the engine, for example. StarkPower had a series of batteries aimed at motorcycles that they were quite open about not having a BMS. Unfortunately they're in Chapter 7 now and the website is gone. More commonly, some batteries with BMS don't have over and under voltage protection. Richard Pfiffner one time was testing batteries, and his vendor shipped 24 volt chargers accidentally for 12 volt batteries. All the white stuff leaked out of the battery. Some electrical genius on R.A.S. (don't remember which one) declared that they really had overvoltage protection, but 24 volts just wasn't enough to trigger it. One of our fellow Schleicher motorglider pilots had an LFP, left the transponder on, and ruined the battery. A 15-20 AH battery intended as a starter battery can easily find it's way into other applications. You may have read about the ASG 32 mi that got fried when the solar controller malfunctioned, drained the battery, and got quite hot when charged from another charger. Did it have a BMS? Doesn't really matter. Dave The problem batteries were Bioenno Batteries. Richard |
#30
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K2 battery endurance
Richard Pfiffner wrote on 6/2/2020 9:26 AM:
.... StarkPower had a series of batteries aimed at motorcycles that they were quite open about not having a BMS. Unfortunately they're in Chapter 7 now and the website is gone. More commonly, some batteries with BMS don't have over and under voltage protection. Richard Pfiffner one time was testing batteries, and his vendor shipped 24 volt chargers accidentally for 12 volt batteries. All the white stuff leaked out of the battery. Some electrical genius on R.A.S. (don't remember which one) declared that they really had overvoltage protection, but 24 volts just wasn't enough to trigger it. One of our fellow Schleicher motorglider pilots had an LFP, left the transponder on, and ruined the battery. A 15-20 AH battery intended as a starter battery can easily find it's way into other applications. You may have read about the ASG 32 mi that got fried when the solar controller malfunctioned, drained the battery, and got quite hot when charged from another charger. Did it have a BMS? Doesn't really matter. Dave The problem batteries were Bioenno Batteries. Were they Bioennos with a BMS that protects against overvoltage? For example, I use the BLF-1220AS, which .... "Includes built-in PCM (protection circuit module) which provides internal cell balancing and management, protection from overcurrent, undervoltage (overdischarge), overvoltage and short circuiting, and has integrated charging circuitry " I haven't tried applying 24 volts to it, but I'd expect it to protect against 24 VDC being applied to it. I've just emailed Bioenno this question, but have not heard back. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 |
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