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Originally Posted by ppc750 If my total commute everyday is 12.55 miles and I ride at about 40-43 mph with a theoretical safe range of 30 miles :1) Is it better for the battery lifespan to charge it every other day or to charge it every day?2) Which is more efficient for overall energy usage: to charge 2 days worth of commuting at one time or to charge it everyday?These questions seem like the same thing almost, but I'd thought I pose them just in case they're not. Thanks! Great question. Generally speaking, it is better for the cycle life of the batteries to be charged more frequently, at less than a full 100% discharge. However, the Valence batteries are rated to >2,000 cycles at 100% depth of discharge, so discharging the batteries fully are not going to harm them. At the rate we charge at (9-10A), we're only at .25C charge rate on the modules, so no need to worry about the charge heating up the cells or anything like that. There is another point to consider here, though, and that's battery balance. Individual batteries will begin to diverge in balance (relative voltage and state of charge compared to other cells) as they near 0% in discharge. If you never take your batts down this far (except for the conditioning period), then you'll likely end up with better balanced batteries. Ironically, the benefit of a better balanced pack is that you'll get more realized capacity and thus greater range (which you won't need because you have a short commute). Of course, the Enertia can "re-balance" it's batteries during the charge cycle, but only at the tail end of a full charge. Check out the "Zen" thread to see how to check the balance of your batteries using the "secret tank button" technique. As far as energy efficiency using the bike one way versus the next, I think the differences would be too small to measure conclusively unless I'm missing something. Also... a couple of points on your spreadsheet. 1. The MPG equivalent listed on your spreadsheet is really an "economic MPG" equivalent using current gas pricing. i.e... that number fluctuates most based on gas prices and not on the performance or efficiency of the bike. Our calculated "MPG" equivalent from an energy usage standpoint is closer to 450 MPG. I think it's a great stat to have on there, I would just add the word "economic". 2. You are measuring power drawn from an outlet and then extrapolating to vehicle efficiency numbers. To do this, you'd really need to know the amount of energy that actually made it to the batteries as the charging process is not 100% efficient (probably closer to 80-90%).This is why those fans kick on during the charge process - because some of that wall power is lost to heat. Also... the charger enters a "balancing" state after the bike reaches 99% SOC, which means it will continually draw power from the outlet, albiet at a reduced wattage. I've been told it's about 40W in this state. So... the numbers used to calculate Wh/mile may be a little high. However, as with your MPG calculation, I think it's a good way to look at it as you paid for the electricity regardless of how much made it into the battery or what the bike decided to do with it other than provide energy for motive purposes. I just wanted to point out why these numbers may seem high.[\quote]
Here is a post from Brian from another forum that does address charging efficiency:
