I have a Giant LaFree Pedelec and going to replace the SLA batteries with some Lithium batteries. The bike has a 400 watt motor and 2-12V 12Ah SLA batteries.
What is the best way to go?
Will the lithiums handle the "peak load" of the 400 watt motor?
1) Use a 24V 10Ah pack.
2) Use a 24V 15Ah pack.
3) Use a 24V 20Ah pack.
4) Use a 28V 10Ah pack.
5) Use a 28V 15Ah pack.
6) Use a 36V 10Ah pack.
With the 24V packs I could just swap in the batteries with no mods. Going with more amp hours costs more and adds weight. The extra amp hours adds range, the 10Ah batteries should have the same range as the stock 12Ah SLA batteries. Are there any other added benefits to the extra amp hours?
With the 28V battery pack I was thinking I could up the performance a little with hopefully no mods. What do you guys think?
Now with the 36V battery pack I would have to change the controller, did not really want to do this, but if it is something worth all the extra work I would probably go for it. What should I expect from this change?
Thanks, Deron.
One other thing I was wondering, what is the operating voltage of a SLA versus a Lithium? The reason I wondering this is will a Lithium give me a performance increase even though it's the same ratted voltage. This being because it has a slightly higher operating voltage.
Deron.
Deron - I'd probably go with the 10Ah / 24V set up - but then I'm cheap.
The higher amp batteries as well as giving you more range will have the added benefit of increased life span. This is because you will be operating at a lower C rate with these batteries.
Say your system peaks with a 30A load. With a 10Ah battery that's 3C (30/10) with a 30Ah battery that's 1C (30/30). The life of all batteries is affected by this characteristic. However, LiFe batteries in general will deal with higher C loads far more effectively than SLA (in other words in your scenario I doubt it's a big deal).
As far as voltages and performance goes. I'm not sure - but I expect that you will experience improved performance even with 10Ah/24V this is based on:
1) Everybody who has done this sort of conversion usually raves about it!
2) The batteries will be significantly lighter
3) The voltage sag is much less over the effective capacity of the battery and drops sharply at the end. This is different from SLA where the drop is more linear. (Although, if I remember right the LiFe's drop slightly more initially which likely "eats up" the advantage of the higher nominal voltage.
This is all based on stuff I've read on these forums - not on actual experience. Hope it helps.
John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.
John, yeah I'm cheap too, that is why I'm considering the 24V 10Ah batteries, other wise I would get the more powerful batteries.
One thing I need to consider too is, I can see the battery technology getting even better in the next few years. So do I want to invest a lot of money now (get the real expensive LiFe that may last me 5 years) , or get something that is cheaper (the LiFe's that can just get the job done and may only last a couple of years) and expect to upgrade in a couple of years.
Deron.
That sounds like another argument for the 10Ah/24V pack to me. Some other things that might make the decision easier - what are the prices of the packs? What range do you regular ride and how does this match to the available capacity of the pack? (i.e. are you regularly running your 12Ah SLAs down to 80% DOD? Or only 50% DOD?).
But, in your place I'd go cheap and re-evaluate next year...
John H. Founder of Current Motor Company - opinions on this site belong to me; not to my employer
Remember: " 'lectric for local. diesel for distance" - JTH, Amp Bros || "No Gas.
Sounds like an argument for lead.
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[url=/forum-topic/motorcycles-and-large-scooters/588-fixing-my-chinese-scooter]900 watt scooter[/url]
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John, I can get one of Ping's 10Ah 24V packs for around $220.00 shipped.
I usually ride less then 10 miles round trip. Although I been thinking about trips to the beach which would probably be about 25 miles round trip.
Not sure what the capacity of my 24V 12Ah SLA's are, I bought the bike with the batteries and they were already pretty used up.
Andrew, lead is all I have any experience with, I think it's worth the extra money to get the LiFe's just so I have better knowledge of what to look for in the way of better LiFe's in the future.
Lead is going to cost me about $100.00 when all is said and done, the LiFe's add $120.00 to that figure. Not too bad if I can get a couple of years out of them.
Deron.
Very true. Actually in your application, I'd highly recommend you get the LiFePo4, as they only need to last 2.2x as long to be cost competitive, and , it's less hassle buying and replacing batteries since they will probably last longer. If they turn out to be junk (which can be the case with any battery), its not a sever loss of investment, which could be the case for a larger pack of LiFePo4.
A few advantages to LiFePo4
Should have better cold weather performance
Can be left discharged without damage
Can be sold in the case of switching to higher voltage/different charging scheme. No one in their right mind will pay much for used lead-acid.
Roughly one might expect 55-60% of lead-acid nominal energy (nominal voltage * rated capacity), and I'd expect more like 90%+ for LiFePo4. So, provided 24v is about the nominal(average) voltage through the discharge curve for the LiFePo4:
Lead-acid: 24v * 12ah = 288whrs * .6 = 172.2 whrs usable
LiFePo4: 24v * 10ah = 240 whrs * .9 = 216 whrs or 25% more than lead-acid.
A few advantages of lead:
Less invested if the batteries are junk
Very efficient, and good for charging from solar/wind
Can buy a spare battery without too much expense
Can find high quality reliable chargers
[url=/forum-topic/motorcycles-and-large-scooters/587-my-kz750-electric-motorcycle-project]KZ750 Motorcycle Conversion[/url]
[url=/forum-topic/motorcycles-and-large-scooters/588-fixing-my-chinese-scooter]900 watt scooter[/url]
Pic from http://www.electri
Deron, there is LOADS of info on Ping's packs over on Endless-Sphere. Like 682 posts of info O_o.
Basically, those packs do best a 1C. They will handle 2C, though not as well. 3C is pretty much their limit. I'll think they'll do 4C momentarily, but that'll do some damage after a while.
But, they are generally regarded as the best you can get for the money, especially since he will build you a custom pack if you ask.
Link to the beginning of the 46 page long topic: http://endless-sphere.com/forums/viewtopic.php?f=14&t=2931&start=0
Remember to put them into some sort of protective shell if you get them; they're prismatic foil cells.
The author of this post isn't responsible for any injury, disability or dismemberment, death, financial loss, illness, addiction, hereditary disease, or any other undesirable consequence or general misfortune resulting from use of the "information" contai
I e-mailed Ping and he says I should use the 24V 20Ah pack for my application. I have a 400 watt motor and he says that's too much for the lower Ah packs. My motor peaks out at 1,000 watts. Do I really have to go with that many Ah's? What would happen if I just went ahead and got the 24V 10Ah pack?
I read the posts about Ping and his batteries, it sounds like there should be no problem getting a good set of batteries from him. I may end up ordering a set this coming week, just want to make sure I know that I will be happy with what I do decide on.
If I do get the 24V 20Ah battery pack, I should never run low on juice in my travels.
Deron.
Yes, you really do need the higer amperage pack.
While the smaller one will "work" it probably won't last very long. These are not expensive high rate cells. They will get quite hot if pushed to hard, which damages them, leading to much shorter cycle life.
Honestly, if I could use them, I would get them. However, I probably will only have space for 5Ah of a 72V (switchable to 10Ah @ 36V) pack. I will likely be running them at 30A (6C), which is far too much for a Ping Pack.
The author of this post isn't responsible for any injury, disability or dismemberment, death, financial loss, illness, addiction, hereditary disease, or any other undesirable consequence or general misfortune resulting from use of the "information" contai
All of a sudden I'm starting to get cold feet. People are bidding Ping's batteries up. If I go for the 24V 20Ah battery pack I could be looking at over $400.00, lead is starting to look real good again. I though I could get away with the cheaper 24V 10Ah pack, but it's not recommended because of the 400 watt motor I have. Hell I only paid $50.00 for the bike, anyways thinking about dumping that much money into it had me searching the internet for a bullet proof lock.
Whats the future look like guys? I'm guessing the only reason LiFe's are expensive is because they are not making billions of them.
Deron.
I think prices will come down. For now, I'd seriously look into a Nimh pack. The large cheap high-capacity D size are popular, but have poor performance. Instead I'd build a pack from sub-C 6 or 7 cell RC car packs. Here's one that could be used. Three of those could be wired in series for one module, wired in parallel with another module for riding, and charge each module individually. That's how I'd do it anyway.
[url=/forum-topic/motorcycles-and-large-scooters/587-my-kz750-electric-motorcycle-project]KZ750 Motorcycle Conversion[/url]
[url=/forum-topic/motorcycles-and-large-scooters/588-fixing-my-chinese-scooter]900 watt scooter[/url]
Pic from http://www.electri