Question on Amp Hours

KennyS

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Mar 15, 2016
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The 1000w/48v ebike kit I bought said to use no less than 17ah batteries. Not wanting to spend the money on Lithiums, I went for 4x18ah SLA's and they're really just too heavy and I'll be using them on a trike build. I'll be fine with half the capacity on the 1000w 48v bike, so want to go with about 9AH batteries at half the weight but for some reason many if not all the 1000w kits advertise the need for no less than 17AH batteries. Isn't the difference just a matter of capacity? or is there something else going on there where less than 17AH batteries won't work? Not enough Amps to run the motor properly?
 

mattheww50

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Generally the higher the AH rating, the more plates and lower internal resistance. That in turn will determine what voltage is available with a ~20 amp draw. Without seeing the battery specifications, I don't know how well the 9Ah cells can deliver the ~20amps. The lower the internal resistance of the battery, the more power it can deliver.

What you need to find out is what sort of rating do the cells have at 20amp draw, because 1000 watts at 48V is about 21 amps. The secondary issue is of course how long will the motor run. 9Ah is about half the capacity of 17Ah, so you will only get about half the range.
 

KennyS

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Thanks so much Mathew, that gives me something to go on. I'm not real concerned with the capacity drop from 18 to 9ah, I mainly need to just get something cheap on the bike so it can be test driven if I should sell it or, for me to give it a try without the trailer that I originally had on the bike that contained the batteries so I can decide to keep it or not. Then either I or the customer can upgrade if need be.

Going to look around now and see what ebay has to offer but not sure what to look for on the battery when it comes to this: What you need to find out is what sort of rating do the cells have at 20amp draw.

The answer to that question may dawn on me when I see the specs, otherwise, I'll be back. Thanks again
 

KennyS

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Mat/anyone, here's a shot from the pdf on the 4 batteries I have in mind. Can you please tell me if they will work and what spec you are looking at to determine that?
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herektir

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Nov 16, 2015
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Looks to me you can get about 10 minutes of use at 20 amp draw. Max is 130 amp draw but im sure that is pulse only. Those batteries will likely face a shortened lifespan if put under a 20 amp draw on a regular basis.
 

KennyS

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Mar 15, 2016
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OK, that and the fact nearly all the ads for these kits make the comment of no less than 17AH batteries, think I'll just go with the trailer and what I have, sell the bike with no batteries or get the more expensive Lithium battery. Fact is, if building a 1000w bike, one pretty much needs to plan on going with the Lithium's, as the SLA are just going to be too heavy for a kit that requires that much power...now I know....Thanks
 
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