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tekochip
User Rank
Platinum
Re: Weight
tekochip   4/19/2013 9:45:41 AM
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Weight is a major issue. I have an electric mower that I modified so I could run from a battery pack and charge it with solar panels. Yes, a green lawn mower. It cost more than I will ever save in fuel, and the original 17AH SLA cells only last about three years. I repacked the mower with a 10AH NiMh that produces the same run time at about 1/3 the weight, a huge savings.
 
I only have one season in the NiMh pack, so I can't comment on life, but there is one downside. It's very easy to monitor the State Of Charge (SOC) for SLA cells, but impossible with NiMh. Since I charge with solar panels I have no way of knowing how much energy is going into the cells, so I had to add a Coulomb counter to monitor the charge. There are plenty of charge monitors on the market used for model aircraft and the like, but they have quiescent currents in the tens of mA range, not suitable when a cloudy day only yields that much from the panels, so I had to build my own monitor that idles in the uA range. Like I said, I'm never going to recoup the cost from fuel savings, but it's been a good learning experience.
 
So, from what I've learned, SLA is heavy, has a poor service life for a constant draw in the 1/2C range, but is very easy to monitor the SOC. The current NiMh technology is fairly light and handles a 1C draw very well, but you can't monitor the SOC very well.


AnandY
User Rank
Gold
Re: Weight
AnandY   4/19/2013 2:17:08 AM
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Lead-acid batteries have lowest energy-to-weight and energy-to-volume designs, making them very big and heavy for the total amount of power that they can put out. But they do have a very high surge-to-weight ratio, which means that they have the capacity to deliver a big jolt of electricity all at once. This feature makes lead-acid battries perfect for applications that need a big, sudden surge of power, such as car starters.

TJ McDermott
User Rank
Blogger
Weight
TJ McDermott   4/18/2013 4:02:13 PM
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Weight wasn't mentioned at all.  That characteristic weighs against lead/acid (forgive the pun), especially for smaller vehicles.

Rob Spiegel
User Rank
Blogger
Re: Lithium ion on the way out?
Rob Spiegel   4/18/2013 11:09:22 AM
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Alternatives to the internal combustion engine. A dressed up older battery technology may help break through the difficulties. Or perhaps something else. So far it looks like lithium-ion will see some challenges.

tekochip
User Rank
Platinum
New Improvements
tekochip   4/18/2013 9:39:54 AM
NO RATINGS
If they could do something to improve the old technology that would be fantastic. Lead-acid is forgiving and easily remanufactured, but it's also heavy and has a poor life-cycle under constant use. It's great for starting cars, though.


Elizabeth M
User Rank
Blogger
Lithium ion on the way out?
Elizabeth M   4/18/2013 9:33:51 AM
NO RATINGS
Interesting story, Chuck. I think it's a bit early to count out lithium ion, especially with some new research in different chemistries. But with all the negative publicity and the current limitations of the technology, there is certainly room for another battery chemistry to take its place.

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