Which batteries?

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ejohn
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Joined: 03/28/2007
Points: 3

Hi

I am an ebike rookie and have some questions.

Why is the difference between normal batteries and rechargeable batteries so big?

OmniCel 3.6 Volt / 35 Ah "DD" Lithium Thionyl Chloride (Li-SOCI 2)

http://shopping.microbattery.com/s.nl/it.A/id.7412/.f

OmniCel 3.6 Volt / 19 Ah "D" Lithium Thionyl Chloride (Li-SOCI 2)

http://shopping.microbattery.com/s.nl/it.A/id.7409/.f

D-Size 1.2 V 10 Ah NiMH Rechargeable Battery

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=709

Are there any rechargeable Batteries (NiMH, Li-Ion or any other) with more than 10 Ah (D-Size)?

Thanks

ejohn

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andrew
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Joined: 11/28/2006
Points: 1361
Re: Which batteries?

There are some F cells from batteryspace with 13 ah capacity. Also some 15 ah NiMH cells from SAFT here: http://www.batterystore.com

One reason we don't see larger NiMH cells is because Texaco bought up the pantent from Ovonic for them. Also, there are not as many applications for large NiMH/NiCad/Li-ion cells meaning production is lower and cost is higher. Most applications requiring a lot of capacity (such as UPS systems) can use cheaper lead-acid which also have a lower self discharge rate.

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Fechter
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Joined: 11/17/2006
Points: 199
Re: Which batteries?

The Lithium Thionyl Chloride batteries are not rechargeable :(

The F size Nimh seem to be the largest capacity commonly available, but there have been mixed reports on the results. The maximum discharge current is not great, especially when compared to the smaller cells. Multiple strings of smaller cells might perform better, but then you have to separate the strings for charging and charge them independently. They can be put in parallel for discharge.

There are some reports of successful charging with parallel strings, but this would require a special charger, and I'm not convinced it's really safe.

If you check eBay, you might score a used Toyota Prius battery for a reasonable price. I saw one recently for $450. It has enough cells that you can toss out a few bad ones and still have a big pack (or two). I don't know anyone who has done this yet, but the supply of used Prius batteries is likely to get better over time.

Lithium batteries like A123 look like the best batteries available nowdays, but they are very expensive. Tearing the cells out of power tool packs seems to be the cheapest way to get them.

ejohn
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Joined: 03/28/2007
Points: 3
Re: Which batteries?

Thank you andrew and Fechter for the answers

Do you mean such battery packs?

http://www.dewalt.com/us/products/attachment_detail.asp?productID=14905

and

http://www.milwaukeeconnect.com/webapp/wcs/stores/servlet/product_27_40028_-1_729955_192355_192327#

Do I need a special charger then?

Thanks

ejohn

andrew
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Points: 1361
Re: Which batteries?

The milwaukee packs don't use A123 batteries.

You can find the Dewalt packs on ebay for $100 occasionally, search "dewalt lithium".

Before you spend thousands consider the "use lead now and wait" logic, as prices are coming down, and there is a lot of battery development going on. Even the NiMH and NiCad offered now are a lot better than they were a few years ago for the price.

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Avatar taken from http://www.electricmotorbike.org/
Anyone got one they might want to sell?
My KZ750 Project: here E.T.A. 1 mo

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