Re: [Aus-soaring] LiFePo4
John, that is really interesting. Have you sampled more than one battery or repeated the test on the same battery? Michael Scutter, Education Training Consultant, Email: michael_scut...@yahoo.com.au Mobile: 0417822330 (Int +614178223300) skype://michaelscutter I don't say anything here that I would not say to your face. From: John Parncutt jparn...@bigpond.net.au To: 'Discussion of issues relating to Soaring in Australia.' aus-soaring@lists.internode.on.net Sent: Tuesday, 26 February 2013 5:57 PM Subject: Re: [Aus-soaring] LiFePo4 Hi David, The link you provide is to exactly the same model of Shorai battery I have been evaluating. The load tests I have done give it an actual capacity of 4 A/H (far from the stated capacity of 14 A/H). I have attached an image of the results for your info, for comparison the results on one of our clubs existing (used) lead acid glider batteries is also included. This clearly demonstrates the ability of the Lithium battery to provide an almost constant voltage across its complete discharge period whereas the lead acid battery voltage continually drops to a point where some of our instrumentation and particularly the radio in transmit mode may fail about halfway through discharge. If you note the Shorai literature states an equivalent A/H rating to that of a 14 A/H lead acid battery not an actual A/H rating. This is misleading and I think a bit of sales spin! The comparison I think is based on the Cold Cranking capacity of the battery, ie. the ability to delivery large currents to a starter motor bearing in mind these batteries are designed to replace wet lead acid motorcycle batteries. The bottom line is that the 14 A/H Shorai battery will not deliver 1 amp continuously for 14 hours, well certainly not the one I tested!! John Parncutt From:aus-soaring-boun...@lists.internode.on.net [mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of David Conway Sent: Tuesday, 26 February 2013 4:38 PM To: 'Discussion of issues relating to Soaring in Australia.' Subject: Re: [Aus-soaring] LiFePo4 Agreed; something like this would be better http://www.shoraipower.com/s.nl/it.A/id.91/.f 14AH – twice that of a normal SLA glider battery – and less than half the weight @ 662g David From:aus-soaring-boun...@lists.internode.on.net [mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of Future Aviation Sent: 26 February 2013 15:02 To: 'Discussion of issues relating to Soaring in Australia.' Subject: Re: [Aus-soaring] LiFePo4 Hi Ian From a safety point of view this is much better than what the Boeing dreamliner is using. However, I would never put a battery like that in a glider unless it is securely placed in a much more impact resistant enclosure. Kind regards Bernard From:aus-soaring-boun...@lists.internode.on.net [mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of Ian Mc Phee Sent: Tuesday, 26 February 2013 2:15 PM To: Discussion of issues relating to Soaring in Australia. Subject: [Aus-soaring] LiFePo4 About $87 and notice a new Arcus M was fitted at factory with something similar. This is NOT what B787 is using. Ian M http://www.hobbyking.com/hobbyking/store/__22656__ZIPPY_Flightmax_8400mAh_4S2P_30C_LiFePo4_Pack_AUS_Warehouse_.html ___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
Re: [Aus-soaring] LiFePo4
Repeat of old info? The batteries in the new Schempps are sold on the accu-24.de website. Bernard, Schleicher #27053 has the Tenergy LiFePO4 batteries in the usual place. Still has the old school batteries in the tail, which needs the weight. The Shorai is the wrong chemistry, unless you're Boeing. Jim From: Future Aviation ec...@internode.on.net To: 'Discussion of issues relating to Soaring in Australia.' aus-soaring@lists.internode.on.net Sent: Monday, February 25, 2013 8:32 PM Subject: Re: [Aus-soaring] LiFePo4 Hi Ian From a safety point of view this is much better than what the Boeing dreamliner is using. However, I would never puta battery like that in a glider unless it is securely placed in a much more impact resistant enclosure. Kind regards Bernard From: aus-soaring-boun...@lists.internode.on.net [mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of Ian Mc Phee Sent: Tuesday, 26 February 2013 2:15 PM To: Discussion of issues relating to Soaring in Australia. Subject: [Aus-soaring] LiFePo4 About $87 and notice a new Arcus M was fitted at factory with something similar. This is NOT what B787 is using. Ian M http://www.hobbyking.com/hobbyking/store/__22656__ZIPPY_Flightmax_8400mAh_4S2P_30C_LiFePo4_Pack_AUS_Warehouse_.html ___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
Re: [Aus-soaring] LiFePo4
I have been trialling the shorai and can support Johns assessement . Shorai rate their capacities on a cold cranking equivalent, its is entirely misleading if you are looking for a battery to supply a steady current over a long period of time. Their 14 ah will not supply 14ah for 1 hour or 1 ah for 14 hours. I have used their 7ah rated cells and its equivalent capacity compared to SLA or Nimh is more like that of a 2 ah cell. Also they are destroyed by deep discharge. Luke dodd From: Michael Scutter Sent: Tuesday, February 26, 2013 3:55 AM To: Discussion of issues relating to Soaring in Australia. Subject: Re: [Aus-soaring] LiFePo4 John, that is really interesting. Have you sampled more than one battery or repeated the test on the same battery? Michael Scutter, Education Training Consultant, Email: michael_scut...@yahoo.com.au Mobile: 0417822330 (Int +614178223300) skype://michaelscutter I don't say anything here that I would not say to your face. From: John Parncutt jparn...@bigpond.net.au To: 'Discussion of issues relating to Soaring in Australia.' aus-soaring@lists.internode.on.net Sent: Tuesday, 26 February 2013 5:57 PM Subject: Re: [Aus-soaring] LiFePo4 Hi David, The link you provide is to exactly the same model of Shorai battery I have been evaluating. The load tests I have done give it an actual capacity of 4 A/H (far from the stated capacity of 14 A/H). I have attached an image of the results for your info, for comparison the results on one of our clubs existing (used) lead acid glider batteries is also included. This clearly demonstrates the ability of the Lithium battery to provide an almost constant voltage across its complete discharge period whereas the lead acid battery voltage continually drops to a point where some of our instrumentation and particularly the radio in transmit mode may fail about halfway through discharge. If you note the Shorai literature states an equivalent A/H rating to that of a 14 A/H lead acid battery not an actual A/H rating. This is misleading and I think a bit of sales spin! The comparison I think is based on the Cold Cranking capacity of the battery, ie. the ability to delivery large currents to a starter motor bearing in mind these batteries are designed to replace wet lead acid motorcycle batteries. The bottom line is that the 14 A/H Shorai battery will not deliver 1 amp continuously for 14 hours, well certainly not the one I tested!! John Parncutt From: aus-soaring-boun...@lists.internode.on.net [mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of David Conway Sent: Tuesday, 26 February 2013 4:38 PM To: 'Discussion of issues relating to Soaring in Australia.' Subject: Re: [Aus-soaring] LiFePo4 Agreed; something like this would be better http://www.shoraipower.com/s.nl/it.A/id.91/.f 14AH – twice that of a normal SLA glider battery – and less than half the weight @ 662g David From: aus-soaring-boun...@lists.internode.on.net [mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of Future Aviation Sent: 26 February 2013 15:02 To: 'Discussion of issues relating to Soaring in Australia.' Subject: Re: [Aus-soaring] LiFePo4 Hi Ian From a safety point of view this is much better than what the Boeing dreamliner is using. However, I would never put a battery like that in a glider unless it is securely placed in a much more impact resistant enclosure. Kind regards Bernard From: aus-soaring-boun...@lists.internode.on.net [mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of Ian Mc Phee Sent: Tuesday, 26 February 2013 2:15 PM To: Discussion of issues relating to Soaring in Australia. Subject: [Aus-soaring] LiFePo4 About $87 and notice a new Arcus M was fitted at factory with something similar. This is NOT what B787 is using. Ian M http://www.hobbyking.com/hobbyking/store/__22656__ZIPPY_Flightmax_8400mAh_4S2P_30C_LiFePo4_Pack_AUS_Warehouse_.html ___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring ___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
Re: [Aus-soaring] LiFePo4
I don't have any graphs or deep knowledge to back my decisions up, but personally I have moved back to SLA. In my glider I have used NiMH with some success, but the lifetime of the batteries (9Ah D cells with solder tabs) was only 2 years, and very expensive.. I think you have to be a lot more careful with NiMH than SLA. My SLA batteries on the other hand have lasted 3 years and a fraction of the price. I use LiPo batteries a lot at home for electronic equipment and Remote Control (well... toys)... and they are great for light weight and large discharge rates. So if you are powering an electric sustainer, by all means look into the lithium area. If you are mounting batteries in your panel (ie, very forward of CofG) or want a small backup systme, consider lithium but also look at more conventional NiMH. If you are trying to replace your standard battery behind the seat, my advice is stick with SLA. One reason I had moved to NiMH was to increase my Ah from 7Ah SLA, with a usable 4Ah to the 9Ah NiMH with a usable 7Ah. Since then I have found better SLA that are rated at 9Ah (same physical size as the 7Ah) - I have not tested real usable DoD but I have yet to flatten even one of my two batteries (now overkill) - well at least not in 5 hour flights. 10 hours might be a different story - although both batteries together should be fine. And... what ever you choose, don't leave your batteries flat, and don't leave them on charge. Scott smime.p7s Description: S/MIME cryptographic signature ___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
Re: [Aus-soaring] LiFePo4
Hi Luke, hello Scott Thank you both for your input. It is valuable and very much appreciated - just keep it coming!!! This highly relevant information is useful for most (if not all) glider pilots on this list. Kind regards to all! Bernard _ From: aus-soaring-boun...@lists.internode.on.net [mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of Luke Dodd Sent: Thursday, 28 February 2013 4:14 AM To: Michael Scutter; Discussion of issues relating to Soaring in Australia. Subject: Re: [Aus-soaring] LiFePo4 I have been trialling the shorai and can support Johns assessement . Shorai rate their capacities on a cold cranking equivalent, its is entirely misleading if you are looking for a battery to supply a steady current over a long period of time. Their 14 ah will not supply 14ah for 1 hour or 1 ah for 14 hours. I have used their 7ah rated cells and its equivalent capacity compared to SLA or Nimh is more like that of a 2 ah cell. Also they are destroyed by deep discharge. Luke dodd From: Michael Scutter mailto:michael_scut...@yahoo.com.au Sent: Tuesday, February 26, 2013 3:55 AM To: Discussion of issues relating mailto:aus-soaring@lists.internode.on.net to Soaring in Australia. Subject: Re: [Aus-soaring] LiFePo4 John, that is really interesting. Have you sampled more than one battery or repeated the test on the same battery? Michael Scutter, Education Training Consultant, Email: michael_scut...@yahoo.com.au Mobile: 0417822330 (Int +614178223300) skype://michaelscutter I don't say anything here that I would not say to your face. _ From: John Parncutt jparn...@bigpond.net.au To: 'Discussion of issues relating to Soaring in Australia.' aus-soaring@lists.internode.on.net Sent: Tuesday, 26 February 2013 5:57 PM Subject: Re: [Aus-soaring] LiFePo4 Hi David, The link you provide is to exactly the same model of Shorai battery I have been evaluating. The load tests I have done give it an actual capacity of 4 A/H (far from the stated capacity of 14 A/H). I have attached an image of the results for your info, for comparison the results on one of our clubs existing (used) lead acid glider batteries is also included. This clearly demonstrates the ability of the Lithium battery to provide an almost constant voltage across its complete discharge period whereas the lead acid battery voltage continually drops to a point where some of our instrumentation and particularly the radio in transmit mode may fail about halfway through discharge. If you note the Shorai literature states an equivalent A/H rating to that of a 14 A/H lead acid battery not an actual A/H rating. This is misleading and I think a bit of sales spin! The comparison I think is based on the Cold Cranking capacity of the battery, ie. the ability to delivery large currents to a starter motor bearing in mind these batteries are designed to replace wet lead acid motorcycle batteries. The bottom line is that the 14 A/H Shorai battery will not deliver 1 amp continuously for 14 hours, well certainly not the one I tested!! John Parncutt From: aus-soaring-boun...@lists.internode.on.net [mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of David Conway Sent: Tuesday, 26 February 2013 4:38 PM To: 'Discussion of issues relating to Soaring in Australia.' Subject: Re: [Aus-soaring] LiFePo4 Agreed; something like this would be better http://www.shoraipower.com/s.nl/it.A/id.91/.f 14AH - twice that of a normal SLA glider battery - and less than half the weight @ 662g David From: aus-soaring-boun...@lists.internode.on.net [mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of Future Aviation Sent: 26 February 2013 15:02 To: 'Discussion of issues relating to Soaring in Australia.' Subject: Re: [Aus-soaring] LiFePo4 Hi Ian From a safety point of view this is much better than what the Boeing dreamliner is using. However, I would never put a battery like that in a glider unless it is securely placed in a much more impact resistant enclosure. Kind regards Bernard _ From: aus-soaring-boun...@lists.internode.on.net [mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of Ian Mc Phee Sent: Tuesday, 26 February 2013 2:15 PM To: Discussion of issues relating to Soaring in Australia. Subject: [Aus-soaring] LiFePo4 About $87 and notice a new Arcus M was fitted at factory with something similar. This is NOT what B787 is using. Ian M http://www.hobbyking.com/hobbyking/store/__22656__ZIPPY_Flightmax_8400mAh_4S 2P_30C_LiFePo4_Pack_AUS_Warehouse_.html ___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring _ ___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit:
Re: [Aus-soaring] LiFePo4
As I said yesterday, do proper engineering on your battery installation. If you don't have real numbers for temperature limits, discharge curves at various rates, charging characteristics etc etc you aren't doing engineering, you're just guessing. A battery designed to start a racing motorbike and then be recharged by the alternator and floated at that voltage likely has quite different characteristics, design and longevity from one designed for charging and deep discharging over several hours then recharging. You can also just stop and get off the bike when the battery catches fire. Li batteries all need individual cell monitoring during charge and use or at least when charging after mostly charged. The problem with Ni MH batteries is the number of cells (10 for a nominal 12 V system). You will have at least one weaker cell which will deep discharge more than the others and will be undercharged or more likely the other cells will overcharge resulting in reduced battery life. Individual cell monitoring would help but with 10 cells vs 4 for Li it is a pain. 3 years isn't bad for a NiMH battery pack. Some people have a problem with max weight of non lifting parts and a few kilos saved may make the difference between flying in or outside the weight and balance envelope. For these LiFEPO4 may be worthwhile but use the correct cells. The cylindrical Tenergy cells sold by these people have engineering data and are Underwriter Labs tested. The tests are published there too. Start here:http://www.all-battery.com/lifepo4battery.aspx I've dealt with them and they did what they said they would. Also these people may be of interest: The batteries seem to be the same as the Tenergy cells but with a different colour outer sleeve. They have battery monitoring/cutoff circuitry available also. You must use a low voltage cutoff at least. http://lithbattoz.com.au The old sealed lead acid batteries are OK. They are heavier although in many installations that may not matter. The capacity is usually quoted at the 20 hour rate. In modern gliders 1 amp continuous is not an unusual load so that's the 7 hour rate. Likely it is a 5 A-H battery at this rate. Give it a couple of dozen charge cycles and it is a 3 or 4 A-H battery and you begin to have problems. Note also the number of cycles you get is non linear with depth of discharge. Small % discharge you'll get lots of cycles. Large % discharge many, many fewer cycles. Size the battery to handle the longest flights and then use two batteries. Use one routinely, keep the other charged then when the first battery dies due to low capacity you have a known good battery. Put that one in the first position then put a new one in the standby position. You should always have a good battery available then. If using some new type either learn enough to do an engineering analysis or find someone willing to do one for you. Otherwise these things may get needlessly banned or we have fires in gliders. It would be embarrassing to explain to your insurance compny why you had to bail out of your burning glider. Mike ___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
Re: [Aus-soaring] LiFePo4
Hi Mike. Really glad you mentioned the quoted rate, I forgot to mention that, as it is how I got better batteries in my glider - point being of course that it doesn't matter if SLA, NiMH or Li* - you have to check those discharge rates, and temperature curves. We recently sent equipment to Antarctica and learnt a heap about batteries then, but we are using primaries so no recharge to consider. Also, the point about multiple NiMH is good too. Multiple batteries without equalisers is quite common in SLA and NiMH - which of course is not ideal. In Li* the risk of combustion when charging has encouraged better balanced chargers which is good news. As for life expectancy of battery, I am probably cheap, but my expectation is that the battery should last 5 years. 2 seasons (not 3 btw) for NiMH was not enough - but likely damaged for exactly the reason you said here. The NiMH batteries I put in were about $100 worth (to get the larger 9Ah size), while the new SLA I put in were under $50, and so far going well... Not that those numbers are in any way scientific or anything but anecdotal. I had not really thought of the weight saving behind CofG being a big issue, but you are right, it could impact take off weights for some glider/pilots - my glider has a huge cargo weight, which includes batteries and old oxygen cylinders. My modern O2 system is so much lighter that I have many kg to spare. Thanks Scott On 27/02/2013, at 11:52 AM, Mike Borgelt mborg...@borgeltinstruments.com wrote: As I said yesterday, do proper engineering on your battery installation. If you don't have real numbers for temperature limits, discharge curves at various rates, charging characteristics etc etc you aren't doing engineering, you're just guessing. A battery designed to start a racing motorbike and then be recharged by the alternator and floated at that voltage likely has quite different characteristics, design and longevity from one designed for charging and deep discharging over several hours then recharging. You can also just stop and get off the bike when the battery catches fire. Li batteries all need individual cell monitoring during charge and use or at least when charging after mostly charged. The problem with Ni MH batteries is the number of cells (10 for a nominal 12 V system). You will have at least one weaker cell which will deep discharge more than the others and will be undercharged or more likely the other cells will overcharge resulting in reduced battery life. Individual cell monitoring would help but with 10 cells vs 4 for Li it is a pain. 3 years isn't bad for a NiMH battery pack. Some people have a problem with max weight of non lifting parts and a few kilos saved may make the difference between flying in or outside the weight and balance envelope. For these LiFEPO4 may be worthwhile but use the correct cells. The cylindrical Tenergy cells sold by these people have engineering data and are Underwriter Labs tested. The tests are published there too. Start here:http://www.all-battery.com/lifepo4battery.aspx I've dealt with them and they did what they said they would. Also these people may be of interest: The batteries seem to be the same as the Tenergy cells but with a different colour outer sleeve. They have battery monitoring/cutoff circuitry available also. You must use a low voltage cutoff at least. http://lithbattoz.com.au The old sealed lead acid batteries are OK. They are heavier although in many installations that may not matter. The capacity is usually quoted at the 20 hour rate. In modern gliders 1 amp continuous is not an unusual load so that's the 7 hour rate. Likely it is a 5 A-H battery at this rate. Give it a couple of dozen charge cycles and it is a 3 or 4 A-H battery and you begin to have problems. Note also the number of cycles you get is non linear with depth of discharge. Small % discharge you'll get lots of cycles. Large % discharge many, many fewer cycles. Size the battery to handle the longest flights and then use two batteries. Use one routinely, keep the other charged then when the first battery dies due to low capacity you have a known good battery. Put that one in the first position then put a new one in the standby position. You should always have a good battery available then. If using some new type either learn enough to do an engineering analysis or find someone willing to do one for you. Otherwise these things may get needlessly banned or we have fires in gliders. It would be embarrassing to explain to your insurance compny why you had to bail out of your burning glider. Mike ___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring -- Scott Penrose sco...@dd.com.au http://scott.dd.com.au/ smime.p7s
Re: [Aus-soaring] LiFePo4
Hello all It just occurred to me that I have omitted to thank John Parncutt for his research and his willingness to share the findings with us. Of course, in this context Mike Borgelt's professional advice must also be mentioned. Both contributions are extremely useful to many of my gliding friends including myself. Many thanks to both of you! Believe it or not, the last set of SLA batteries powering the engine circuit in my ASH 25 lasted for 10 years. At the time I opted for the most expensive SLA batteries I could get my hands on and now it appears that the old saying holds indeed true. You only get what you Kind regards to all. Bernard Eckey -Original Message- From: aus-soaring-boun...@lists.internode.on.net [mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of Mike Borgelt Sent: Wednesday, 27 February 2013 11:22 AM To: Discussion of issues relating to Soaring in Australia. Subject: Re: [Aus-soaring] LiFePo4 As I said yesterday, do proper engineering on your battery installation. If you don't have real numbers for temperature limits, discharge curves at various rates, charging characteristics etc etc you aren't doing engineering, you're just guessing. A battery designed to start a racing motorbike and then be recharged by the alternator and floated at that voltage likely has quite different characteristics, design and longevity from one designed for charging and deep discharging over several hours then recharging. You can also just stop and get off the bike when the battery catches fire. Li batteries all need individual cell monitoring during charge and use or at least when charging after mostly charged. The problem with Ni MH batteries is the number of cells (10 for a nominal 12 V system). You will have at least one weaker cell which will deep discharge more than the others and will be undercharged or more likely the other cells will overcharge resulting in reduced battery life. Individual cell monitoring would help but with 10 cells vs 4 for Li it is a pain. 3 years isn't bad for a NiMH battery pack. Some people have a problem with max weight of non lifting parts and a few kilos saved may make the difference between flying in or outside the weight and balance envelope. For these LiFEPO4 may be worthwhile but use the correct cells. The cylindrical Tenergy cells sold by these people have engineering data and are Underwriter Labs tested. The tests are published there too. Start here:http://www.all-battery.com/lifepo4battery.aspx I've dealt with them and they did what they said they would. Also these people may be of interest: The batteries seem to be the same as the Tenergy cells but with a different colour outer sleeve. They have battery monitoring/cutoff circuitry available also. You must use a low voltage cutoff at least. http://lithbattoz.com.au The old sealed lead acid batteries are OK. They are heavier although in many installations that may not matter. The capacity is usually quoted at the 20 hour rate. In modern gliders 1 amp continuous is not an unusual load so that's the 7 hour rate. Likely it is a 5 A-H battery at this rate. Give it a couple of dozen charge cycles and it is a 3 or 4 A-H battery and you begin to have problems. Note also the number of cycles you get is non linear with depth of discharge. Small % discharge you'll get lots of cycles. Large % discharge many, many fewer cycles. Size the battery to handle the longest flights and then use two batteries. Use one routinely, keep the other charged then when the first battery dies due to low capacity you have a known good battery. Put that one in the first position then put a new one in the standby position. You should always have a good battery available then. If using some new type either learn enough to do an engineering analysis or find someone willing to do one for you. Otherwise these things may get needlessly banned or we have fires in gliders. It would be embarrassing to explain to your insurance compny why you had to bail out of your burning glider. Mike ___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring ___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
[Aus-soaring] 100% electric VTOL
Hello all! Have a look and see how the beautiful fuselage design of the ASW 27,ASW 28 and ASG 29 can be misused! http://www.jobyaviation.com/animation Kind regards Bernard ___ Aus-soaring mailing list Aus-soaring@lists.internode.on.net To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
Re: [Aus-soaring] LiFePo4
Hi, When people start talking of glider batteries I laugh at their logic. We have a toy that cost anywhere between 2 - 10k and upwards to keep in the air each year(not including getting to and from the airfield and actually getting it in the air) and they are not willing to replace a couple of batteries each year for well under a $100. These fancy batteries may be ok but in the vast majority of gliders the simple still works best and is cheap and safe. Yes I do play with these fancy batteries in my radio control toys but withgreat care and they are always stored in a lipo safe bag. You only have to watch this video to agree http://www.youtube.com/watch?v=mw8jb1KmAG8 yes I know the newer ones are better but these are only small and look at how they go up and even the newer ones can still have problems. regards, Arie On 27/02/2013 12:52 PM, Future Aviation wrote: Hello all It just occurred to me that I have omitted to thank John Parncutt for his research and his willingness to share the findings with us. Of course, in this context Mike Borgelt's professional advice must also be mentioned. Both contributions are extremely useful to many of my gliding friends including myself. Many thanks to both of you! Believe it or not, the last set of SLA batteries powering the engine circuit in my ASH 25 lasted for 10 years. At the time I opted for the most expensive SLA batteries I could get my hands on and now it appears that the old saying holds indeed true. You only get what you Kind regards to all. Bernard Eckey -Original Message- From: aus-soaring-boun...@lists.internode.on.net [mailto:aus-soaring-boun...@lists.internode.on.net] On Behalf Of Mike Borgelt Sent: Wednesday, 27 February 2013 11:22 AM To: Discussion of issues relating to Soaring in Australia. Subject: Re: [Aus-soaring] LiFePo4 As I said yesterday, do proper engineering on your battery installation. If you don't have real numbers for temperature limits, discharge curves at various rates, charging characteristics etc etc you aren't doing engineering, you're just guessing. A battery designed to start a racing motorbike and then be recharged by the alternator and floated at that voltage likely has quite different characteristics, design and longevity from one designed for charging and deep discharging over several hours then recharging. You can also just stop and get off the bike when the battery catches fire. Li batteries all need individual cell monitoring during charge and use or at least when charging after mostly charged. The problem with Ni MH batteries is the number of cells (10 for a nominal 12 V system). You will have at least one weaker cell which will deep discharge more than the others and will be undercharged or more likely the other cells will overcharge resulting in reduced battery life. Individual cell monitoring would help but with 10 cells vs 4 for Li it is a pain. 3 years isn't bad for a NiMH battery pack. Some people have a problem with max weight of non lifting parts and a few kilos saved may make the difference between flying in or outside the weight and balance envelope. For these LiFEPO4 may be worthwhile but use the correct cells. The cylindrical Tenergy cells sold by these people have engineering data and are Underwriter Labs tested. The tests are published there too. Start here:http://www.all-battery.com/lifepo4battery.aspx I've dealt with them and they did what they said they would. Also these people may be of interest: The batteries seem to be the same as the Tenergy cells but with a different colour outer sleeve. They have battery monitoring/cutoff circuitry available also. You must use a low voltage cutoff at least. http://lithbattoz.com.au The old sealed lead acid batteries are OK. They are heavier although in many installations that may not matter. The capacity is usually quoted at the 20 hour rate. In modern gliders 1 amp continuous is not an unusual load so that's the 7 hour rate. Likely it is a 5 A-H battery at this rate. Give it a couple of dozen charge cycles and it is a 3 or 4 A-H battery and you begin to have problems. Note also the number of cycles you get is non linear with depth of discharge. Small % discharge you'll get lots of cycles. Large % discharge many, many fewer cycles. Size the battery to handle the longest flights and then use two batteries. Use one routinely, keep the other charged then when the first battery dies due to low capacity you have a known good battery. Put that one in the first position then put a new one in the standby position. You should always have a good battery available then. If using some new type either learn enough to do an engineering analysis or find someone willing to do one for you. Otherwise these things may get needlessly banned or we have fires in gliders. It would be embarrassing to explain to your insurance compny why you had to bail out of your burning glider. Mike ___
