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Originally Posted by P-hack
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Thanks,
The last set of LiON specs didn't look that good to me and their prices were excessive. But it is good to see the technology getting more affordable.
Quote:
Originally Posted by P-hack
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If you are bent on 30 year old technology then I don't know what to tell ya. Also I'm not sure what ECU you are referring to since you are talking about a plane one minute then a prius the next. I don't know why the ECU can't be disconnected (or the whole battery) in either event, or if it is custom arduino why data can't be stashed on eeprom on shutdown.
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Sorry it wasn't clear but hopefully this will help:
- LiON - still evolving as prices are changing on a day-by-day basis. In contrast, the NiMH is fairly well bottomed out and have relatively benign characteristics. I'm confident about using the NiMH but would prefer to let others explore the LiON replacement batteries . . . for now. Still, I need to research the vendor's specs, not just the Amazon sales page.
- Prius vs airplane - it has been insights gained from the Prius that have made it easier to adopt new technology in my plane. Aviation is a curious mix of advanced and anchient and having the Prius experience has made it easier to adopt 1990s and later technology into the plane.
- Disconnecting the fuel injection ECU and/or fuel pump turns off the engine. It is in effect a critical part of the engine.
- Arduino nano has significantly improved characteristics over the MSP430 I was originally planning to use . . . five years of Moore's Law.
Since it looks like LiON is approaching a commodity, at least in the motorcycle world, I'm interested. But I have this project and need solutions I can trust in a timely fashion.
I went to the Shorai web site and started reading their FAQ. Sure enough, I found risks I don't want to tackle:
- 13.1V maximum charge - over charging a LiON battery is bad news, very bad, as some of the laptop battery fires attest. In contrast, the Hirth alternator will be using a standard, lead-acid regulator and they typically charge at 13.8-13.9 V. The 11-cell, NiMH battery will be within this limit and has some tolerance for overcharge by generating excess H{2} that recombines within the sealed cells.
- -18-32C temperature range - HUH! This is not even automotive grade temperature ranges. Other source put LiFeP0{4} operating temperature maximum at 55C. Still too heat sensitive for my Alabama climate.
- cold cranking - they recognize the same thing I've seen that non-spinning, motor inrush current is the enemy BUT it turns out 'soft-start' is not that hard today with power semiconductors and micro-controllers. This is a solvable problem if the battery and load are considered to be parts of a system and NOT treated as separate parts.
- charger regulator table - their voltage ranges are about 1V higher than a traditional 12V, lead-acid battery system. It is one of the reasons why I am not using two, 6-cell, Prius battery modules. The 3.2V of this battery pretty well puts it out of the range I'm comfortable with handling.
Depending upon how my NiMH experiment turns out, I may revisit this approach. But it is good to know LiON batteries are starting to show up in off-the-shelf solutions at reasonable prices.
Bob Wilson