tag:blogger.com,1999:blog-7683526616307057319.post6294760241043210179..comments2023-04-06T05:49:36.625-07:00Comments on Honda S2000 Electric Vehicle Conversion: Volt BlocherBrianhttp://www.blogger.com/profile/11065813696724781338noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-7683526616307057319.post-31284395588229038242009-03-23T11:27:00.000-07:002009-03-23T11:27:00.000-07:00As the voltage increases the amount of energy shun...As the voltage increases the amount of energy shunted also increases to try and keep the cell voltage down.<BR/><BR/>The following are approximate numbers:<BR/>3.6v - 1.5 amps<BR/>3.8v - 1.8 amps<BR/>4.0v - 2.0+ (Only tested this once just to see the amps continue to rise, I like to keep mine at 3.8 max also)<BR/><BR/>So these numbers are what the balancers will shunt. How many amps are still going into the cells is based on your charger.<BR/><BR/>For example if your cells are at 3.6 volts but you are charging at 5 amps then 3.5 amps is still making it into the cells. If the cells are at 3.8 volts then only 3.2 amps are making it into the cells.<BR/><BR/>Most chargers have options for setting voltage and/or amperage to some degree. You can decrease your final charge amps to just slightly above the balancers shunting ability. This allows for a very slow final charge stage in which the cells will be able to balance nicely. Using higher amperage will give less time for balancing but not waste as much energy in shunting. You can adjust this as needed to meant your requirements for balancing. Typically you'll do a nice slow balance up front and then a much shorter balance cycle since these cells stay fairly well balanced. You can then always come back later when you want and change it back to do a slow and more complete balance.Brianhttps://www.blogger.com/profile/11065813696724781338noreply@blogger.comtag:blogger.com,1999:blog-7683526616307057319.post-36497959569569772132009-03-22T19:25:00.000-07:002009-03-22T19:25:00.000-07:00>>>The cell balancer is designed to start...>>>The cell balancer is designed to start shunting energy at 3.6 volts that would otherwise be going into the cell. The balancer shunts 1.5 amps at 3.6v and goes up from there as the voltage increases<<<<BR/><BR/>Goes up from there? What is the max amps it can shunt? Are they basically shunting everything at 3.8 Volts? (A good place to stop charging)<BR/><BR/>Does it do anything when you are not charging?LeftLibertarianhttps://www.blogger.com/profile/00658939383725543092noreply@blogger.comtag:blogger.com,1999:blog-7683526616307057319.post-63884928559321927702009-03-17T15:21:00.000-07:002009-03-17T15:21:00.000-07:00Nice work!You should also check out http://www.lit...Nice work!<BR/>You should also check out http://www.lithiumbalance.com/technology.htmlMads Aaruphttps://www.blogger.com/profile/15127856885507178133noreply@blogger.comtag:blogger.com,1999:blog-7683526616307057319.post-90669670664311144252009-03-17T14:39:00.000-07:002009-03-17T14:39:00.000-07:00Wow thanks for the link that is amazing that they ...Wow thanks for the link that is amazing that they caught fire, if indeed they did.<BR/><BR/>I'm not using a link 10. I'm using the BMS system from TS which is not a full manaagement system but partial. The BMS and charger are fully itegrated. <BR/><BR/>The BMS will:<BR/>* Monitors for high voltage and reduce the amp output on the charger until the voltage drops below a safe level.<BR/><BR/>* Monitors for high temperature and take the same action as high temp when charging.<BR/><BR/>* Monitors for low voltage and will not charge at all until the voltage is raised.<BR/><BR/>During non charging conditions the BMS will beep rather loudly if you reach low/high voltage, high temperature and high current but it doesn't have an active role (i.e. cut back on the motor controller). You just have to listen and make the corrections yourself based on the problem which is shown nicely on a 7" LCD touchscreen.<BR/><BR/>The new cell balancers that I've designed just work hand-in-hand with this BMS. Since I already have high voltage protection these balancers don't protect completely from high voltage, they just delay it to give the lower cells time to catch up in charge. The higher rates you charge at, the less time you'll be giving the balancers to work. However, once balanced for the first time I doubt I'll ever need to charge it slowly again. <BR/><BR/>I don't have regen and if I did I wouldn't have full protection from high voltage while driving. What would happen is the cell balancers would kick in and start burning off energy as needed. They would not be able to keep with regen but would help.<BR/><BR/>The real question is would you ever be in a scenario where you are fully charged (just pulled the car off the charger so at 3.6v or so) and then start heading down a hill for awhile? If not I seriously doubt you'll ever see enough power regenerated to cause a problem.Brianhttps://www.blogger.com/profile/11065813696724781338noreply@blogger.comtag:blogger.com,1999:blog-7683526616307057319.post-26368665638861345562009-03-17T12:21:00.000-07:002009-03-17T12:21:00.000-07:00Brian, two questions: 1) do you have any low volta...Brian, two questions: 1) do you have any low voltage protection at cell level in your system (if I remember you have a Link 10 for the pack) and 2) if you use regen, do you have any over voltage protection when driving? I just ask because at present on my project I have charge balancing, but no low/high voltage protection for the LiFePo cells when driving and wondered if you think that's an issue. SimonUnknownhttps://www.blogger.com/profile/06761409491967720258noreply@blogger.comtag:blogger.com,1999:blog-7683526616307057319.post-65207235934729304382009-03-17T12:17:00.000-07:002009-03-17T12:17:00.000-07:00Looks like a nice piece of work, as usual, Brian. ...Looks like a nice piece of work, as usual, Brian. The way you describe your system it seems to protect against over voltage, but you might want to take note of this recent discussion:<BR/><BR/>http://www.batteryvehiclesociety.org.uk/forums/viewtopic.php?t=1825&postdays=0&postorder=asc&start=0<BR/><BR/>Where LiFePo4s are suspected of overheating and burning (!), <I>possibly</I> as a result of a BMS/charge management problem not detecting an individual failure in a cell. If I understand your system it could still deliver full charge to a cell/pack when there is a failure? Anyway you might want to take a look.Unknownhttps://www.blogger.com/profile/06761409491967720258noreply@blogger.com