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PostPosted: Wed Apr 11, 2012 5:16 am 
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Location: CLEARWATER, MN
Has any one had a long-term (>2years) ownership of Torqeedo motor for your Hobie? I was contemplating buying one but a relative of mine owns a pedal-assist bicycle with a lithium-polymer battery. Has to replace it every third year for about $400. I checked with local battery company and was told that three years was about all to expect it to last (80% capacity at 1 year/50%-2yr/10%-3yr). The Torqeedo uses a lithium-manganese battery...will it last longer than three years?


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PostPosted: Wed Apr 11, 2012 6:37 am 
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That's one of the reasons that Toyota still uses their Nickel-metal hydride battery for their hybrids. They're not as lightweight or energy dense as the newer batteries, but they have proven themselves to be reliable. It's still a concern with battery technology.

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PostPosted: Wed Apr 11, 2012 9:01 am 
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We have several kits here at our factory that we have used since before we started offering the eVolve kit to the public - nearly 4 years of use now, with no problems.

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PostPosted: Wed Apr 11, 2012 2:08 pm 
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I talked to another lithium battery 'expert' and was told that storage time was not very important, rather the number of times you recharge or top off the battery. It is better to run the battery nearly but not completely down than to repeatedly charge a partially charged battery. So if you use it only once in a while, it will last quite a long time. But if you put it on the charger every time you come in, this will cause the battery to loose its capacity in a fairly short time.
I thought that only NiCad batteries had such a 'memory problem'. If you repeatedly recharge a partially charged NiCad battery, the battery no longer has the full capacity. For Lithium batteries it's the number of times that it is recharged, not, how full the battery is, when you recharge.


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PostPosted: Wed Apr 11, 2012 3:19 pm 
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TIDALWAVE wrote:
I talked to another lithium battery 'expert' and was told that storage time was not very important, rather the number of times you recharge or top off the battery. It is better to run the battery nearly but not completely down than to repeatedly charge a partially charged battery. So if you use it only once in a while, it will last quite a long time. But if you put it on the charger every time you come in, this will cause the battery to loose its capacity in a fairly short time.
I thought that only NiCad batteries had such a 'memory problem'. If you repeatedly recharge a partially charged NiCad battery, the battery no longer has the full capacity. For Lithium batteries it's the number of times that it is recharged, not, how full the battery is, when you recharge.

I'd check that. I'm certainly no battery expert, but I've read in more than place lately, that lithium batteries should be kept charged and should only be nearly discharged occasionally. http://www.techrepublic.com/blog/five-a ... y-life/289

"Experts are people who avoid all the minor pitfalls on their way to the grand fallacy."

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PostPosted: Wed Apr 11, 2012 6:50 pm 
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Since Hobie has been having good luck with their evolve motors and batteries. Maybe they could share what they've been doing? I don't have an evolve, but am very interested in the technology.

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 Post subject: lithium recharging.
PostPosted: Thu Apr 12, 2012 6:26 am 
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I thought, also, that Lithium batteries should be kept charged. But my sister's lithium-polymer battery for her pedal assist bike had to be replaced after a little more than two biking seasons. She charged the battery after every ride. Replacement cost was $375 for a new 10aH battery (about same capacity as the Hobie battery). The battery company said it was common for the lithium batteries to have to be replaced every two to three years. Yikes!


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PostPosted: Fri Apr 13, 2012 12:09 pm 
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Guys - while I am not a battery "expert", I have been playing with Lithium Polymer batteries for almost 10 years now in my remote control Airplane hobby and have prolly spent over $2,000 in batteries and keep abreast on the latest news on care and feeding. LiPo batteries are described as having a nominal voltage of 3.7v / cell and a specific capacity rated in Ah/hr or Mah/hr rating. Battery packs are made by connecting individual cells in series to increase voltage (in 3.7v increments), and sometimes then again in parallel to increase total capacity.

1) storage - long term storage of LiPo batteries should be stored between 60-70* F. Batteries should be stored at a storage voltage of 3.85v/cell. Storage of a battery in a fully charged state has detrimental effects resulting in increased internal resistance of the cells and this is non-reversable and cumulative. Therefore, LiPo batteries should be charged before use, used within a few hours of charging, and brought back to their storage voltage of 3.85v/cell. If a pack is charged for use and then you won't be using it (say, you charge Fri nite for sat use but it rains all weekend and you won't use them until the next week) it should be discharged back to storage voltage. It has been proven that a pack has much better performance and longevity this way as opposed to trying to limit the total # of cycles by leaving it charged.

2) Discharge - Lipo batteries should NEVER be discharged below 3.0v/cell (known as deep discharge) and for logevity, should only be discharged to 20% capacity.

3) charge - LiPo batteries are charged by specific chargers that have "taps" to each individual cell as well as leads to the main +/- leads. This is done to balance the voltage across all cells in a pack by either limiting voltage to individual cells or discharging them. Cells are rated based on their ability to give up and absorb their given capacity and this determines their maximum charge and discharge rates. Common practice for longevity is to charge the cells at an amperage equal to their capacity, i.e. a 2a/hr pack is charged at 2a. Recent improvements in cell chemestry and charger technology that monitors individual cell votages has allowed for as high as 5c charge rates but long term effects on total life cycles and longevity at these higher charge rates has been exhibited. Regardless of capcity, LiPo cells should NEVER be charged to more than 4.2v/cell as there is serious fire hazards !!

So, lets talk plain english - why do cell phone / laptop batteries die prematurely ? mostly due to deep discharging - running until or almost until device shutdown ... and also overcharging by leaving device plugged in for extended periods after maximum charge is reached. The latter is bad, not because it keeps on trickle-charging like NiCad/NiMh battery charges used to (thats why your old power tools failed in a year) ... but because the pack reaches peak, shuts off, then the pack "stabilizes" to a slightly lower voltage and it thries to charge it again ... and again ... etc. Resting voltage after a full charge is not 4.2v/cell - that is the peak voltage during charging.

... back to more plain english (sorry) a LiPo pack that is properly cared for can last 3-5 years or more and sustain hundreds and hundreds of cycles. Yes, they do lose a small percentage of their usefulness over time, But, abuse of LiPo's as said above is cumulative and non-reversable which is why they usually last considerably less before performance is so poor you are looking to replace them.

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