From xavier.carcelle at gmail.com Wed May 15 10:15:18 2013 From: xavier.carcelle at gmail.com (Xavier Carcelle) Date: Wed, 15 May 2013 16:15:18 +0200 Subject: [Power] Checking the life battery of XOs batteries deployed after 3 years of usage Message-ID: Dear power OLPC folks, As we work on the NosyKomba, Madagascar team of OLPC France, we are keeping on expertizing the states of the 200+ xos we deployed there and we are wondering if we can estimate the life duration of the batteries we have for the XOs after 3+ years of usage there. The only simple solution we see if logging the "forth" test of the battery : ok Testing /battery at 0 AC:off Battery: BYD LiFePO4 68% 6.46V -0.60A 34C discharging Okay Is there any way of plugging an equipment to check the battery life and check their states ? I think there is one-wire protocol between the battery and the motherboard bus that may be used ? Thanks for your prompt support as we are on-site currently. Cheers, Xavier Carcelle From richard at laptop.org Wed May 15 11:16:34 2013 From: richard at laptop.org (Richard Smith) Date: Wed, 15 May 2013 11:16:34 -0400 Subject: [Power] Checking the life battery of XOs batteries deployed after 3 years of usage In-Reply-To: References: Message-ID: On Wed, May 15, 2013 at 10:15 AM, Xavier Carcelle wrote: > Dear power OLPC folks, > > As we work on the NosyKomba, Madagascar team of OLPC France, we are > keeping on expertizing the states of the 200+ xos we deployed there > and we are wondering if we can estimate the life duration of the > batteries we have for the XOs after 3+ years of usage there. > > The only simple solution we see if logging the "forth" test of the battery : > ok Testing /battery at 0 > AC:off Battery: BYD LiFePO4 68% 6.46V -0.60A 34C discharging Okay > > Is there any way of plugging an equipment to check the battery life > and check their states ? Yes. I have a tool for doing exatly that. Actually I have 2 tools but the 2nd tool which is used at the factory is designed for a 1.75 or XO-4. I've made it run on the 1.5 but it needs some firmware mods. Its not much different than what I'm describing below. The tool that works on all laptops however is called olpc-pwr-log. It has been in the OS build since XO-1 days. So its guaranteed to be there. However, you may want to get the latest copy for doing tests. The most recent copy can be found here: http://dev.laptop.org/~rsmith/pwr_scripts/olpc-pwr-log Basically what this does is just log the data from the battery. Information on the output and usage is here: http://wiki.laptop.org/go/XO_power_draw#olpc-pwr-log Basically to measure capacity you would: 1) Charge up the laptop. 2) Disable auto power management (if enabled) 3) run olpc-pwr-log from a terminal 4) disconnect external power 5) let the laptop sit until it powers off. Then power the laptop back up and look at the logfile that olpc-pwr-log created. If you are using a new version of the script then the 8th column is your net capacity in mAh. Newer scripts have 9 columns and the 9th is net time in minutes. I'm very interested in your data. Please send me copies of all the log files you generate. I'd like to see what a 3 year usage looks like as well. I have python tool(s) for processing files in build or for looking at various things. Let me know if you want to learn how to use them. Net mAh however should give you a good indication of your current capacity. 2800mAh is the number I use for capacity of a new battery on its first cycle. Some batteries can be higher but all batteries should start out at at least 2800mAh. -- Richard A. Smith One Laptop per Child From richard at laptop.org Wed May 15 11:16:34 2013 From: richard at laptop.org (Richard Smith) Date: Wed, 15 May 2013 11:16:34 -0400 Subject: [Power] Checking the life battery of XOs batteries deployed after 3 years of usage In-Reply-To: References: Message-ID: On Wed, May 15, 2013 at 10:15 AM, Xavier Carcelle wrote: > Dear power OLPC folks, > > As we work on the NosyKomba, Madagascar team of OLPC France, we are > keeping on expertizing the states of the 200+ xos we deployed there > and we are wondering if we can estimate the life duration of the > batteries we have for the XOs after 3+ years of usage there. > > The only simple solution we see if logging the "forth" test of the battery : > ok Testing /battery at 0 > AC:off Battery: BYD LiFePO4 68% 6.46V -0.60A 34C discharging Okay > > Is there any way of plugging an equipment to check the battery life > and check their states ? Yes. I have a tool for doing exatly that. Actually I have 2 tools but the 2nd tool which is used at the factory is designed for a 1.75 or XO-4. I've made it run on the 1.5 but it needs some firmware mods. Its not much different than what I'm describing below. The tool that works on all laptops however is called olpc-pwr-log. It has been in the OS build since XO-1 days. So its guaranteed to be there. However, you may want to get the latest copy for doing tests. The most recent copy can be found here: http://dev.laptop.org/~rsmith/pwr_scripts/olpc-pwr-log Basically what this does is just log the data from the battery. Information on the output and usage is here: http://wiki.laptop.org/go/XO_power_draw#olpc-pwr-log Basically to measure capacity you would: 1) Charge up the laptop. 2) Disable auto power management (if enabled) 3) run olpc-pwr-log from a terminal 4) disconnect external power 5) let the laptop sit until it powers off. Then power the laptop back up and look at the logfile that olpc-pwr-log created. If you are using a new version of the script then the 8th column is your net capacity in mAh. Newer scripts have 9 columns and the 9th is net time in minutes. I'm very interested in your data. Please send me copies of all the log files you generate. I'd like to see what a 3 year usage looks like as well. I have python tool(s) for processing files in build or for looking at various things. Let me know if you want to learn how to use them. Net mAh however should give you a good indication of your current capacity. 2800mAh is the number I use for capacity of a new battery on its first cycle. Some batteries can be higher but all batteries should start out at at least 2800mAh. -- Richard A. Smith One Laptop per Child From richard at laptop.org Wed May 15 11:36:27 2013 From: richard at laptop.org (Richard Smith) Date: Wed, 15 May 2013 11:36:27 -0400 Subject: [Power] Checking the life battery of XOs batteries deployed after 3 years of usage In-Reply-To: References: Message-ID: > > Then power the laptop back up and look at the logfile that > olpc-pwr-log created. If you are using a new version of the script > then the 8th column is your net capacity in mAh. Newer scripts have 9 > columns and the 9th is net time in minutes. I forgot to include what to do if you don't have an 8th column. If you are using a version of the script that is old enough not to have a net mAh column (8th). Then you can compute the net mAh by subtracting the starting and stopping values of the ACR register. The wiki page info is from when it was reported in raw units but since XO-1.5 the kernel now reports the value in uAh (micro Ah). Unless you have a really, really old build the ACR values should be in uAh. So you can just take the difference in ACR and then / 1000 to get mAh. This is all handled for you if you use the newer versions of the script. -- Richard A. Smith One Laptop per Child From richard at laptop.org Wed May 15 11:36:27 2013 From: richard at laptop.org (Richard Smith) Date: Wed, 15 May 2013 11:36:27 -0400 Subject: [Power] Checking the life battery of XOs batteries deployed after 3 years of usage In-Reply-To: References: Message-ID: > > Then power the laptop back up and look at the logfile that > olpc-pwr-log created. If you are using a new version of the script > then the 8th column is your net capacity in mAh. Newer scripts have 9 > columns and the 9th is net time in minutes. I forgot to include what to do if you don't have an 8th column. If you are using a version of the script that is old enough not to have a net mAh column (8th). Then you can compute the net mAh by subtracting the starting and stopping values of the ACR register. The wiki page info is from when it was reported in raw units but since XO-1.5 the kernel now reports the value in uAh (micro Ah). Unless you have a really, really old build the ACR values should be in uAh. So you can just take the difference in ACR and then / 1000 to get mAh. This is all handled for you if you use the newer versions of the script. -- Richard A. Smith One Laptop per Child From xavier.carcelle at gmail.com Wed May 15 16:25:51 2013 From: xavier.carcelle at gmail.com (Xavier Carcelle) Date: Wed, 15 May 2013 22:25:51 +0200 Subject: [Power] Checking the life battery of XOs batteries deployed after 3 years of usage In-Reply-To: References: Message-ID: Dear Richard, Thanks a lot for your quick reply > Yes. I have a tool for doing exatly that. Actually I have 2 tools but > the 2nd tool which is used at the factory is designed for a 1.75 or > XO-4. I've made it run on the 1.5 but it needs some firmware mods. > Its not much different than what I'm describing below. Excellent! We have XOs 1.0 and 1.5 deployed and 1.75 in Paris but currently our expertise will be on 1.0/1.5 > The tool that works on all laptops however is called olpc-pwr-log. It > has been in the OS build since XO-1 days. So its guaranteed to be > there. However, you may want to get the latest copy for doing tests. > The most recent copy can be found here: > > http://dev.laptop.org/~rsmith/pwr_scripts/olpc-pwr-log > > Basically what this does is just log the data from the battery. > Information on the output and usage is here: > > http://wiki.laptop.org/go/XO_power_draw#olpc-pwr-log Very accurate infos. These data are written into the eeprom by which process ? reading info from the batteries that are written into eeprom through one-wire ? spi ? > Basically to measure capacity you would: > > 1) Charge up the laptop. > 2) Disable auto power management (if enabled) how do i know if this is enable/disable on my XO ? > 3) run olpc-pwr-log from a terminal > 4) disconnect external power > 5) let the laptop sit until it powers off. > > Then power the laptop back up and look at the logfile that > olpc-pwr-log created. If you are using a new version of the script > then the 8th column is your net capacity in mAh. Newer scripts have 9 > columns and the 9th is net time in minutes. > > I'm very interested in your data. Please send me copies of all the > log files you generate. I'd like to see what a 3 year usage looks > like as well. We have decided to backup all 200+ XOs power-logs so I will tarball everything over the next days but here are sample for first approach of the data. > I have python tool(s) for processing files in build or for looking at > various things. Let me know if you want to learn how to use them. > Net mAh however should give you a good indication of your current > capacity. Would it be possible to test your python tool also over our logs and get some feedbacks of the batteries ? > 2800mAh is the number I use for capacity of a new battery on its first > cycle. Some batteries can be higher but all batteries should start > out at at least 2800mAh. Excellent, we should find out interesting data from our logs and maybe extract the low level batteries. Is there a way to desulfate or regenerate some of the insider liquid/acid of the batteries ? any RMA for the OLPC fondation on the batteries ? Lionel told me that you will be in Paris early June and we could meet up to share experiences about power and OLPC deployments ? Cheers, Xavier. > -- > Richard A. Smith > One Laptop per Child > _______________________________________________ > Power mailing list > Power at lists.laptop.org > http://lists.laptop.org/listinfo/power -------------- next part -------------- A non-text attachment was scrubbed... Name: pwr-SHF8160017F-130427_102852.csv Type: text/csv Size: 2116 bytes Desc: not available URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: pwr-SHF8160017F-120809_182051.csv Type: text/csv Size: 4416 bytes Desc: not available URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: pwr-SHF8160017F-120623_145630.csv Type: text/csv Size: 830 bytes Desc: not available URL: -------------- next part -------------- A non-text attachment was scrubbed... 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Name: pwr-SHF8160017F-120811_104233.csv Type: text/csv Size: 901 bytes Desc: not available URL: From xavier.carcelle at gmail.com Wed May 15 16:25:51 2013 From: xavier.carcelle at gmail.com (Xavier Carcelle) Date: Wed, 15 May 2013 22:25:51 +0200 Subject: [Power] Checking the life battery of XOs batteries deployed after 3 years of usage In-Reply-To: References: Message-ID: Dear Richard, Thanks a lot for your quick reply > Yes. I have a tool for doing exatly that. Actually I have 2 tools but > the 2nd tool which is used at the factory is designed for a 1.75 or > XO-4. I've made it run on the 1.5 but it needs some firmware mods. > Its not much different than what I'm describing below. Excellent! We have XOs 1.0 and 1.5 deployed and 1.75 in Paris but currently our expertise will be on 1.0/1.5 > The tool that works on all laptops however is called olpc-pwr-log. It > has been in the OS build since XO-1 days. So its guaranteed to be > there. However, you may want to get the latest copy for doing tests. > The most recent copy can be found here: > > http://dev.laptop.org/~rsmith/pwr_scripts/olpc-pwr-log > > Basically what this does is just log the data from the battery. > Information on the output and usage is here: > > http://wiki.laptop.org/go/XO_power_draw#olpc-pwr-log Very accurate infos. These data are written into the eeprom by which process ? reading info from the batteries that are written into eeprom through one-wire ? spi ? > Basically to measure capacity you would: > > 1) Charge up the laptop. > 2) Disable auto power management (if enabled) how do i know if this is enable/disable on my XO ? > 3) run olpc-pwr-log from a terminal > 4) disconnect external power > 5) let the laptop sit until it powers off. > > Then power the laptop back up and look at the logfile that > olpc-pwr-log created. If you are using a new version of the script > then the 8th column is your net capacity in mAh. Newer scripts have 9 > columns and the 9th is net time in minutes. > > I'm very interested in your data. Please send me copies of all the > log files you generate. I'd like to see what a 3 year usage looks > like as well. We have decided to backup all 200+ XOs power-logs so I will tarball everything over the next days but here are sample for first approach of the data. > I have python tool(s) for processing files in build or for looking at > various things. Let me know if you want to learn how to use them. > Net mAh however should give you a good indication of your current > capacity. Would it be possible to test your python tool also over our logs and get some feedbacks of the batteries ? > 2800mAh is the number I use for capacity of a new battery on its first > cycle. Some batteries can be higher but all batteries should start > out at at least 2800mAh. Excellent, we should find out interesting data from our logs and maybe extract the low level batteries. Is there a way to desulfate or regenerate some of the insider liquid/acid of the batteries ? any RMA for the OLPC fondation on the batteries ? Lionel told me that you will be in Paris early June and we could meet up to share experiences about power and OLPC deployments ? Cheers, Xavier. > -- > Richard A. Smith > One Laptop per Child > _______________________________________________ > Power mailing list > Power at lists.laptop.org > http://lists.laptop.org/listinfo/power -------------- next part -------------- A non-text attachment was scrubbed... Name: pwr-SHF8160017F-130427_102852.csv Type: text/csv Size: 2116 bytes Desc: not available URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: pwr-SHF8160017F-120809_182051.csv Type: text/csv Size: 4416 bytes Desc: not available URL: -------------- next part -------------- A non-text attachment was scrubbed... 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Name: pwr-SHF8160017F-120808_210345.csv Type: text/csv Size: 1965 bytes Desc: not available URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: pwr-SHF8160017F-120808_184510.csv Type: text/csv Size: 945 bytes Desc: not available URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: pwr-SHF8160017F-120623_162231.csv Type: text/csv Size: 850 bytes Desc: not available URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: pwr-SHF8160017F-120808_190849.csv Type: text/csv Size: 1022 bytes Desc: not available URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: pwr-SHF8160017F-120623_161328.csv Type: text/csv Size: 1145 bytes Desc: not available URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: pwr-SHF8160017F-120808_195438.csv Type: text/csv Size: 2870 bytes Desc: not available URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: pwr-SHF8160017F-120811_104233.csv Type: text/csv Size: 901 bytes Desc: not available URL: From richard at laptop.org Wed May 15 17:45:24 2013 From: richard at laptop.org (Richard A. Smith) Date: Wed, 15 May 2013 17:45:24 -0400 Subject: [Power] Checking the life battery of XOs batteries deployed after 3 years of usage In-Reply-To: References: Message-ID: <519401F4.1080905@laptop.org> On 05/15/2013 04:25 PM, Xavier Carcelle wrote: > Very accurate infos. These data are written into the eeprom by which > process ? reading info from the batteries that are written into eeprom > through one-wire ? spi ? The eeprom inside the battery gauge contains very little data that is of importance to anything except the EC battery code. The mechanism is via the olpc battery driver which talks to the EC via EC commands. All the in the log are not eeprom values but rather the decoded values from registers in the battery gauge chip. ie voltage, current, ACR. The EC reads these registers from the battery via one-wire and then the kernel gets them from the EC via the command channel. >> 2) Disable auto power management (if enabled) > how do i know if this is enable/disable on my XO ? Power management is disabled by default on an XO-1 so unless you turned it on its off. XO-1.5s shipped with power management enabled. You can tell if its enabled by looking in the sugar control panel. http://wiki.laptop.org/go/Sugar_Control_Panel#Automatic_power_management > We have decided to backup all 200+ XOs power-logs so I will tarball > everything over the next days but here are sample for first approach > of the data. Great. Thank you. >> I have python tool(s) for processing files in build or for looking at >> various things. Let me know if you want to learn how to use them. >> Net mAh however should give you a good indication of your current >> capacity. > > Would it be possible to test your python tool also over our logs and > get some feedbacks of the batteries ? We can for log files that have enough battery runtime. Looking at the sample log files you sent most of them are when the laptop is connected to external power. In that case there isn't much power usage information. > > Excellent, we should find out interesting data from our logs and maybe > extract the low level batteries. Is there a way to desulfate or > regenerate some of the insider liquid/acid of the batteries ? Nope. LiFePO4 batteries do not have those issues. There were some problems with cell balancing on early XO-1 batteries but if you were having problem with that you would probably have noticed. Batteries that have a capacity that has dropped to below what you consider a usable level should be recycled and new ones purchased. Log files that have long runs of where the XO is on battery only should be able to give you an approximate battery capacity. > any RMA > for the OLPC fondation on the batteries ? Nope. > Lionel told me that you will be in Paris early June and we could meet > up to share experiences about power and OLPC deployments ? Yes I'll be there but only briefly. I'll be on vacation in London and my girlfriend and I decided to take an overnight trip to Paris. We arrive June 5th (noonish) plan to spend the day wandering around, and then leave the morning of the 6th. We are planning to have a dinner with a friend of mine on the 6th. We want to go to a good Raclette place but have not yet decided where. You are welcome to join us for dinner and/or drinks before hand. I'll email you off list to work out the details. -- Richard A. Smith One Laptop per Child From xavier.carcelle at gmail.com Tue May 28 04:52:15 2013 From: xavier.carcelle at gmail.com (Xavier Carcelle) Date: Tue, 28 May 2013 10:52:15 +0200 Subject: [Power] Power solutions for charging 150+ XOs1.0/1.5 Message-ID: Dear power-list, Richard, Concerning the deployment at Madagascar, we are looking at replacing our current "diesel group" that we use to charge the XO batteries (a zoo of 100 XO-1.0s and 50+ XO-1.5s). We then want to redo the math calculation of the load needed during the charge to see if we can support the charge of 50, 100, 150 XOs batteries at the same time with different energy solutions (diesel, wind turbine, water turbine...) Can you recall us : -the max current needed during the charge (and probably higher at the beginning of the charge) ? -the difference of current needed for 1.0 and 1.5 ? -what the recommandations regarding the diesel group for 50, 100, 150 XOs to recharge at the same time during the XOs class ? My warm "power" regards, Xavier. PS : Of course you guys have seen the fast recharge process found by Eesha Khare http://www.policymic.com/articles/43337/supercapacitor-phone-charger-eesha-khare-s-invention-charges-phones-instantly From richard at laptop.org Tue May 28 12:28:38 2013 From: richard at laptop.org (Richard Smith) Date: Tue, 28 May 2013 12:28:38 -0400 Subject: [Power] Power solutions for charging 150+ XOs1.0/1.5 In-Reply-To: References: Message-ID: On Tue, May 28, 2013 at 4:52 AM, Xavier Carcelle wrote: > > Can you recall us : > -the max current needed during the charge (and probably higher at the > beginning of the charge) ? Are you talking @ 240Vac? or at DC? > -the difference of current needed for 1.0 and 1.5 ? For 240Vac see the numbers I gave for George's SF presentation. https://docs.google.com/presentation/d/1HL2Ok_9E6VIzEh0G-d_iQ5RoSAtwMZ74pw_Nme84Dbg/edit#slide=id.g22073e4d_0_0 Basically if you allocate a peak of 30W per XO (all XOs) you should be ok. If you know it would only be XO-1 on the circuit then you could plan for 21W/XO. Then 30Wh of energy for the full charge. XO off. If the XO is powered on then its a bit harder to come up with the energy needed because it depends on workload but it would be at least 15Wh more and probably closer to 20Wh. > -what the recommandations regarding the diesel group for 50, 100, 150 > XOs to recharge at the same time during the XOs class ? I'm not clear on what recommendations you want. You want recommendations for a Diesel generator or for a replacement of the generator with another technology? > PS : Of course you guys have seen the fast recharge process found by Eesha Khare > http://www.policymic.com/articles/43337/supercapacitor-phone-charger-eesha-khare-s-invention-charges-phones-instantly Not to be cynical but I would not hold your breath. Various people have sent me articles about this and none of them actually say what this magic is. Considering the only thing she has powered so far is an LED its a long ways off from any sort of usable product even if it really is some revolutionary device. LEDs take mW and a device like a cell phone or batteries deal in Watts. Thats 3 orders of magnitude of difference. -- Richard A. Smith One Laptop per Child From richard at laptop.org Tue May 28 12:28:38 2013 From: richard at laptop.org (Richard Smith) Date: Tue, 28 May 2013 12:28:38 -0400 Subject: [Power] Power solutions for charging 150+ XOs1.0/1.5 In-Reply-To: References: Message-ID: On Tue, May 28, 2013 at 4:52 AM, Xavier Carcelle wrote: > > Can you recall us : > -the max current needed during the charge (and probably higher at the > beginning of the charge) ? Are you talking @ 240Vac? or at DC? > -the difference of current needed for 1.0 and 1.5 ? For 240Vac see the numbers I gave for George's SF presentation. https://docs.google.com/presentation/d/1HL2Ok_9E6VIzEh0G-d_iQ5RoSAtwMZ74pw_Nme84Dbg/edit#slide=id.g22073e4d_0_0 Basically if you allocate a peak of 30W per XO (all XOs) you should be ok. If you know it would only be XO-1 on the circuit then you could plan for 21W/XO. Then 30Wh of energy for the full charge. XO off. If the XO is powered on then its a bit harder to come up with the energy needed because it depends on workload but it would be at least 15Wh more and probably closer to 20Wh. > -what the recommandations regarding the diesel group for 50, 100, 150 > XOs to recharge at the same time during the XOs class ? I'm not clear on what recommendations you want. You want recommendations for a Diesel generator or for a replacement of the generator with another technology? > PS : Of course you guys have seen the fast recharge process found by Eesha Khare > http://www.policymic.com/articles/43337/supercapacitor-phone-charger-eesha-khare-s-invention-charges-phones-instantly Not to be cynical but I would not hold your breath. Various people have sent me articles about this and none of them actually say what this magic is. Considering the only thing she has powered so far is an LED its a long ways off from any sort of usable product even if it really is some revolutionary device. LEDs take mW and a device like a cell phone or batteries deal in Watts. Thats 3 orders of magnitude of difference. -- Richard A. Smith One Laptop per Child From scott at solarnetone.org Tue May 28 12:45:40 2013 From: scott at solarnetone.org (scott) Date: Tue, 28 May 2013 12:45:40 -0400 (EDT) Subject: [Power] Power solutions for charging 150+ XOs1.0/1.5 In-Reply-To: References: Message-ID: I must recommend solar for this. Generators can easily become untenable if the supply line providing fuel is interrupted, notwithstanding the pollution and maintenence issues. On Tue, 28 May 2013, Richard Smith wrote: > On Tue, May 28, 2013 at 4:52 AM, Xavier Carcelle > wrote: >> >> Can you recall us : >> -the max current needed during the charge (and probably higher at the >> beginning of the charge) ? > > Are you talking @ 240Vac? or at DC? > >> -the difference of current needed for 1.0 and 1.5 ? > > For 240Vac see the numbers I gave for George's SF presentation. > > https://docs.google.com/presentation/d/1HL2Ok_9E6VIzEh0G-d_iQ5RoSAtwMZ74pw_Nme84Dbg/edit#slide=id.g22073e4d_0_0 > > Basically if you allocate a peak of 30W per XO (all XOs) you should be > ok. If you know it would only be XO-1 on the circuit then you could > plan for 21W/XO. Then 30Wh of energy for the full charge. XO off. If > the XO is powered on then its a bit harder to come up with the energy > needed because it depends on workload but it would be at least 15Wh > more and probably closer to 20Wh. > >> -what the recommandations regarding the diesel group for 50, 100, 150 >> XOs to recharge at the same time during the XOs class ? > > I'm not clear on what recommendations you want. You want > recommendations for a Diesel generator or for a replacement of the > generator with another technology? > >> PS : Of course you guys have seen the fast recharge process found by Eesha Khare >> http://www.policymic.com/articles/43337/supercapacitor-phone-charger-eesha-khare-s-invention-charges-phones-instantly > > Not to be cynical but I would not hold your breath. Various people > have sent me articles about this and none of them actually say what > this magic is. Considering the only thing she has powered so far is > an LED its a long ways off from any sort of usable product even if it > really is some revolutionary device. LEDs take mW and a device like a > cell phone or batteries deal in Watts. Thats 3 orders of magnitude of > difference. > > -- > Richard A. Smith > One Laptop per Child > _______________________________________________ > Power mailing list > Power at lists.laptop.org > http://lists.laptop.org/listinfo/power > From scott at solarnetone.org Tue May 28 12:45:40 2013 From: scott at solarnetone.org (scott) Date: Tue, 28 May 2013 12:45:40 -0400 (EDT) Subject: [Power] Power solutions for charging 150+ XOs1.0/1.5 In-Reply-To: References: Message-ID: I must recommend solar for this. Generators can easily become untenable if the supply line providing fuel is interrupted, notwithstanding the pollution and maintenence issues. On Tue, 28 May 2013, Richard Smith wrote: > On Tue, May 28, 2013 at 4:52 AM, Xavier Carcelle > wrote: >> >> Can you recall us : >> -the max current needed during the charge (and probably higher at the >> beginning of the charge) ? > > Are you talking @ 240Vac? or at DC? > >> -the difference of current needed for 1.0 and 1.5 ? > > For 240Vac see the numbers I gave for George's SF presentation. > > https://docs.google.com/presentation/d/1HL2Ok_9E6VIzEh0G-d_iQ5RoSAtwMZ74pw_Nme84Dbg/edit#slide=id.g22073e4d_0_0 > > Basically if you allocate a peak of 30W per XO (all XOs) you should be > ok. If you know it would only be XO-1 on the circuit then you could > plan for 21W/XO. Then 30Wh of energy for the full charge. XO off. If > the XO is powered on then its a bit harder to come up with the energy > needed because it depends on workload but it would be at least 15Wh > more and probably closer to 20Wh. > >> -what the recommandations regarding the diesel group for 50, 100, 150 >> XOs to recharge at the same time during the XOs class ? > > I'm not clear on what recommendations you want. You want > recommendations for a Diesel generator or for a replacement of the > generator with another technology? > >> PS : Of course you guys have seen the fast recharge process found by Eesha Khare >> http://www.policymic.com/articles/43337/supercapacitor-phone-charger-eesha-khare-s-invention-charges-phones-instantly > > Not to be cynical but I would not hold your breath. Various people > have sent me articles about this and none of them actually say what > this magic is. Considering the only thing she has powered so far is > an LED its a long ways off from any sort of usable product even if it > really is some revolutionary device. LEDs take mW and a device like a > cell phone or batteries deal in Watts. Thats 3 orders of magnitude of > difference. > > -- > Richard A. Smith > One Laptop per Child > _______________________________________________ > Power mailing list > Power at lists.laptop.org > http://lists.laptop.org/listinfo/power > From richard at laptop.org Wed May 29 02:37:57 2013 From: richard at laptop.org (Richard Smith) Date: Wed, 29 May 2013 02:37:57 -0400 Subject: [Power] Power solutions for charging 150+ XOs1.0/1.5 In-Reply-To: References: Message-ID: > Not to be cynical but I would not hold your breath. Various people > have sent me articles about this and none of them actually say what > this magic is. So I finally found some details. http://www.usc.edu/CSSF/Current/Projects/S0912.pdf Basically she claims to have found material useful in making better supercapacitors. However, its still a long ways off. The energy density is 20Wh/kg. As a comparison the energy density of the LiPO4 battery in the XO over 102 Wh/kg. I say over because my weight measurement includes the _entire_ battery, plastics, metal case around the battery, electronics and connector. While her finding seems to be a step in the right direction its not going to supplant the battery in your cell phone anytime soon. Its slowly getting closer though. -- Richard A. Smith One Laptop per Child From richard at laptop.org Wed May 29 02:37:57 2013 From: richard at laptop.org (Richard Smith) Date: Wed, 29 May 2013 02:37:57 -0400 Subject: [Power] Power solutions for charging 150+ XOs1.0/1.5 In-Reply-To: References: Message-ID: > Not to be cynical but I would not hold your breath. Various people > have sent me articles about this and none of them actually say what > this magic is. So I finally found some details. http://www.usc.edu/CSSF/Current/Projects/S0912.pdf Basically she claims to have found material useful in making better supercapacitors. However, its still a long ways off. The energy density is 20Wh/kg. As a comparison the energy density of the LiPO4 battery in the XO over 102 Wh/kg. I say over because my weight measurement includes the _entire_ battery, plastics, metal case around the battery, electronics and connector. While her finding seems to be a step in the right direction its not going to supplant the battery in your cell phone anytime soon. Its slowly getting closer though. -- Richard A. Smith One Laptop per Child