tag:blogger.com,1999:blog-8791349899507304778.post8328419394780855840..comments2017-09-18T06:30:59.825-07:00Comments on Geppetto Electronics: Hydra II EVSE variant now availableNickhttp://www.blogger.com/profile/10500722547077537044noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-8791349899507304778.post-9391584821901860842014-05-10T19:00:53.824-07:002014-05-10T19:00:53.824-07:00Oh... One more thing. I read your comment again an...Oh... One more thing. I read your comment again and you spoke of 20A when sharing 40A. Don't forget that you must derate a 40A circuit breaker 20% because EVSEs are continuous duty. You're only going to be able to charge at a total of 32A, not 40A. This goes on up too. A 50A breaker affords 40A for charging. To charge at the maximum rate the spec allows - 80A - you must use a 100A breaker. Nickhttps://www.blogger.com/profile/10500722547077537044noreply@blogger.comtag:blogger.com,1999:blog-8791349899507304778.post-37933961327676618292014-05-10T13:47:58.819-07:002014-05-10T13:47:58.819-07:00I have thought of arrangements like that, but not ...I have thought of arrangements like that, but not implemented them only because at least from my perspective the cost:benefit ratio doesn't work out. <br /><br />The reference design calls for a 40A circuit, so can deliver up to 32A, shared between two vehicles at a maximum of 30A for any one. Most cars that draw less than 30 will draw close enough to 16A that trying to optimize isn't going to be of much benefit in terms of charge time - a few minutes out of 3-4 hours. <br /><br />There's also balancing time. Most cars will draw 100% of their offered power until the battery gets close to 100% and then drop down to 6A or less (6A is the lowest offer allowed by the spec). It might be possible to detect, say, 5 minutes of sub-6A draw and then just drop them to a 6A pilot and give the rest to the other car, but it adds complication to the state machine for a potential benefit of giving around 10A to the other car for a half an hour perhaps.<br /><br />In the "worse is better" school, tremendous value is placed on simplification of the design at the potential expense of extra features. That's one that just didn't make the cut so far. <br /><br />That said, the firmware is on GitHub, and I certainly am not adverse to pull requests. Nickhttps://www.blogger.com/profile/10500722547077537044noreply@blogger.comtag:blogger.com,1999:blog-8791349899507304778.post-29799515994298208702014-05-10T13:35:18.110-07:002014-05-10T13:35:18.110-07:00Hi Nick,
I was wondering if it would be possible ...Hi Nick,<br /><br />I was wondering if it would be possible to program the Hydra to detect when one of the 2 vehicles doesn't require the full amount of power that it is alloted and then reduce the power accordingly, while increasing the power offered to the 2nd vehicle. I believe you have amp meters on each outlet, so you might be able to do it.<br /><br />For example, let's say that there are 2 cars and a 40 amp Hydra II. Car A requires 32 amps, so when plugged in alone, it gets the full allotment. However, when a second car is plugged in, the 40 amps are shared equally: 20 amps for car A and 20 amps for car B. However, car B is a PHEV and can only charge at 16 amps. Instead of "wasting" 4 amps, the Hydra could sense that car B never pulls more than 16 amps and then adjust the pilot signals so that it offers 24 amps to car A and 16 amps to car B, therefore allowing car A to charge slightly faster and maximizing the use of available power from the Hydra.<br /><br />I don't know if it's doable, but it would certainly be a great feature that would take advantage of your design and be more advanced than what the current generation of EVSE offer.Anonymoushttps://www.blogger.com/profile/00065443845338354963noreply@blogger.com