# General purpose e-motorcycle



## frodus (Apr 12, 2008)

That's a great basic motorcycle system. 

For batteries:
Motorcycles use maybe 100Wh/mi using Lead Acid. So if you want 30 miles, you're going to need 100Wh* 30 = 3000Wh or thereabouts. Lead doesn't do well at high discharge rates, and are only good for about 1/2 capacity or a little better.... so maybe 6kwh of lead acid batteries total to hit 30miles of range consistently.

Lets say you use 85Ah 12V batteries (about 1020Wh each)... you'd need 6 of those. They're not that light either. Or if you used lifepo4, you could get away with only the 3000Wh (maybe a tad more) and get 72V worth of 40Ah lifepo4. Might be a little sluggish though, as 40Ah can't supply a ton of current. It'll last longer too.


So to answer your question, 12V 20Ah batteries would give you maybe 10Ah each, or 120Wh. You'd need maybe 50 of those to get a solid 30 mile range.


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## mdimarco (Oct 22, 2013)

I'd say run it at 12-18v with 2-3 6v 235 Ah golf cart batteries. 2800-4200 wh easy. It will only cost you $260-390. Pretty affordable huh? Frodus where do you get that 1/2 discharge number? That isn't true with real deep cycles flooded. They are designed to go down to 20% charge repetitively.

Is this a common theme of this forum to demonize lead acid? Sure seems like it.


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## frodus (Apr 12, 2008)

He'd be lucky to get to 25 mph at 12-18vdc mdimarco. Volts equals rpm. He'd be better off with higher voltage and less ah batteries... Like I said before. 

And yes it's pretty much the problem with lead acid. The energy density Sucks. Your results may vary a little.... But I'm giving him rule of thumb from my experience building my own, working with many customers, owning an Ev business, working on vehicles for a couple motorcycle companies... May not be dead nuts on but it's close. He Will need more than 3kwh on a lead motorcycle. Almost all of the home builds I've done or seen have used more than 100wh/mi...and that is conservative.

Reasons you need more lead than you think? You don't want to discharge them down past 70% if you want them to last more than a few months. You'll kill them if you use all their energy. Also... Lead has a very pronounced peukert effect... So the higher current you discharge.... The less total energy they'll put out. Thats not to mention the extra weight causing a higher wh/mi usage.


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## bob_sp (Oct 22, 2013)

thanks frodus and mdimarcus,

It seems i was too optmistic with the batteries. If i use 6* 85Ah 12V batteries, how much would that weigh?


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## ken will (Dec 19, 2009)

bob_sp said:


> thanks frodus and mdimarcus,
> 
> It seems i was too optmistic with the batteries. If i use 6* 85Ah 12V batteries, how much would that weigh?


They are about 55 lbs. each so, 6 x 55 = 330 lbs.


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## frodus (Apr 12, 2008)

Just make sure you check on the datasheet for your battery. They usually have a discharge curve for varying hour rates. 85Ah is the 20-hour rate. You want a 1hour rate or less. Also, there are some 85Ah that I see (just looking online) that are almost 80lbs, others are 50lbs. Lead makes a huge difference. They may both meet 85Ah 20hour rate, but I bet they perform differently at higher current discharge.

When in doubt, just ask.


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## pumpdatbass420 (Dec 3, 2013)

I'm not sure if they're realy deep cells but I've been using Kinetik power cells in all my cars to start and push my subs. Sometimes 15"s. I've discharge the crap out of those batteries, how far exactly I don't know. I've had my first set of 3 of they're 850 series batteries for 3 years now and 2 of them still currently start and supply power to my 10 Rockford Fosgate and the other runs my girlfriends cavalier. They are AGM SLA batteries and by far the best ones I have used myself. Even including optima. Great batteries I was thinking of using them for my first build or 2 for an electric gokart/motorcycle


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