tag:blogger.com,1999:blog-3936311651117457138.post8151072881524804928..comments2022-12-25T21:06:34.825-08:00Comments on Electric Porsche: First Charge Complete: Balancing the Cells, part 2Joeyhttp://www.blogger.com/profile/01042435434585986098noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-3936311651117457138.post-32485578762853527172013-01-24T18:50:20.719-08:002013-01-24T18:50:20.719-08:00I'm considering the miniBMS or the Elithimate ...I'm considering the miniBMS or the Elithimate lite. For state of charge I want to get the EMW android display.Joeyhttps://www.blogger.com/profile/01042435434585986098noreply@blogger.comtag:blogger.com,1999:blog-3936311651117457138.post-78293926461086611122013-01-24T16:33:48.001-08:002013-01-24T16:33:48.001-08:00Hey Joey,
After reading about tracking the pack&#...Hey Joey,<br /><br />After reading about tracking the pack's state-of-charge, I wonder if you have decided on a BMS (or not!)<br /><br />MarkAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-3936311651117457138.post-31166033766088996872012-12-20T17:14:54.027-08:002012-12-20T17:14:54.027-08:00Hi Rufus. Thanks for the comments. The first cha...Hi Rufus. Thanks for the comments. The first charge graph is wavy because of the small resistance in each battery connection. Each cell is connected in parallel and the cells farther from the charger were seeing less voltage due to line losses. Some of the variation you see is me trying to move the charger leads around to get more voltage to the lower cells. The orange dashed line was one of the last measurements I made before turning the charger off. Then I just let the cells sit with the charger off, to passively balance.<br /><br />The point about the wildly variable discharge current is that the measured battery voltage after a charge or discharge event is unreliable until the cells rest for 12-24 hours. The charging procedure occurs under more controlled conditions. The charger sets voltage and current, and once I experimentally find the settings that yield the proper resting voltage, I can repeatably charge the cells under controlled conditions. Driving conditions are not as well controlled, and because non-resting voltage is not a reliable measure of battery state of charge, I must take other steps to avoid over discharging the pack – like counting electrons with an amp hour meter and not using the bottom 20% of the pack’s capacity.Joeyhttps://www.blogger.com/profile/01042435434585986098noreply@blogger.comtag:blogger.com,1999:blog-3936311651117457138.post-75501902604358049382012-12-20T16:26:22.013-08:002012-12-20T16:26:22.013-08:00Just so you know folks are reading: First charge ...Just so you know folks are reading: First charge graph was a bit hard to interpret until I looked down at the 2nd -- is orange dash before or after orange diamond? Now I see.<br /><br />"discharge current is wildly variable" -- at first I thought this was amusing (duh, he’s re-building a Porshe...) But I suppose that would still be true if you started with old AMC Gremlin and a smaller motor. In for a penny, in for a pound. <br /><br /> <br />Rufus.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3936311651117457138.post-7803893378200249722012-12-13T12:00:22.426-08:002012-12-13T12:00:22.426-08:00Me too. It is taking longer than I expected to ma...Me too. It is taking longer than I expected to make battery boxes. This car is full of curves.Joeyhttps://www.blogger.com/profile/01042435434585986098noreply@blogger.comtag:blogger.com,1999:blog-3936311651117457138.post-15314253213040845862012-12-13T10:39:09.370-08:002012-12-13T10:39:09.370-08:00Can't wait to see the performance of your car ...Can't wait to see the performance of your car with the new gray cells!.Rickyboyhttps://www.blogger.com/profile/12500410977835704570noreply@blogger.com