Electric bike battery question

[msmith1199]

I have a pair of electric bikes that I bought for my wife and I probably over 10 years ago. We almost never used them and they sat in the garage so they are practically brand new. Now I have more time and I want to start using them again, but the lead acid batteries are shot on them. So I'm doing some research on trying to get new batteries, but I wanted to upgrade to a Lithium Ion battery for both of them. They are more expensive, but a lot lighter and carry a better charge.

I stopped by a local bike shop that does electric bike conversions and talked to a young kid there. I told him what I had and what I wanted to do and he didn't think I could do it, but couldn't tell me exactly why. He didn't think you could use a Lithium Ion battery on a motor designed for Lead Acid. I'm no electrician so I have no idea if that's true or not. Anybody here with knowledge on this? The motor is a 24 volt .5 HP Currie motor. Currently it uses two lead acid 12 volt batteries linked together to make one 24 volt battery. Can I just get a 24 volt Lithium Ion battery and use it?

[RickW]

1. Call central republic about the Dakota battery (leave message). They may be able to answer your questions.

2. Buy 1 pair of batteries and charger to see how you wife likes it first.

I have the hilltoper kit supplied from the same company. If you pedal too, 10 AH is about 10 miles.

[hershey]

What ever lipo battery you find that will work is the big part of the conversion. The other big part is finding a battery charger that will "SAFELY" charge a lipo battery. It has to be the proper battery or charging the batteries will be a sure fire disaster in the making...emphasis on the word FIRE.

[wa8yxm]

Short answer: The motor does not care, 12 volts or (xx volts) is 12 volts (or xx volts) it needs the proper voltage likewise the motor controller, all it needs is the proper voltage, and of course enough amp hours to haul you about.

The battery CHARGER however,,,, that you will need to upgrade.

[msmith1199]

You load that into your car easily because it's small and all the weight is at the bottom.

[2oldman]

msmith1199 wrote:
So these batteries should cut that weight by 15 pounds per bike.

And that'll really make things much easier. Congrats!

[RJsfishin]

I been play'n w/ an E Bike lately.
I just found this in Quartzsite,.....don't know what it is. It runs on 24v (2 18 AH 12v batteries,....really runs good. I load it in my car quite easily.
I can't imagine buying Lithium batteries for it, but what ever.

[msmith1199]

With what you taught me here, I looked at the specs on those batteries versus what I currently have in the lead acid and they look identical. Basically 12 volt, 10Ah. Both say 20 amp max continuous draw. The big difference I like is the lead acid batteries weigh at least 10 pounds each for a 20 pound total. These batteries say 2 pounds 9 oz each. That is a huge difference. The electric motor is probably 15 pounds too. Adding 35 pounds to the back of a bike makes really unstable. My wife was always dropping hers. So these batteries should cut that weight by 15 pounds per bike.

[2oldman]

msmith1199 wrote:
So if it doesn't work 2oldman I'll send you the bill!! 🙂

LOL.. do that!

YES, Li doesn't come cheap. Hey, I have 8 AGMs.. talk about cash!

[msmith1199]

Those Dakota batteries appear to be about the cheapest I can find. I hope cheap price doesn't mean poor performance. But even at cheap price I'm still going to have to spend $400 for four of them, plus two chargers, so It's going to be a $500 upgrade. So if it doesn't work 2oldman I'll send you the bill!! 🙂

[2oldman]

msmith1199 wrote:
The current lead acid batteries have 10 amp batteries also. So does that mean the batteries in my link should be at least just as good?

In my estimation, yes. I made a small error on the watts, but it's still ok.

[msmith1199]

2oldman wrote:

msmith1199 wrote:
Think they will work? (Li batteries).

The gobbledy-gook is something like this:

One horsepower is 768watts. Divided by 2 (for 0.5 hp) = 368w.
368 watts/24volts = 15 amperes of current. That's assuming your motor is ALWAYS running at 1/2 HP, but I doubt it is.

About those batteries in your link: They are 10ah. They show a discharge rate of 20A max continuous, 60A max 2-second pulse. ... For longest lifetime recommended discharge rate 1-5Amps

My opinion ( and that's all it is):
Let's say your bike draws 8 amps at 24v. (running at 1/4hp) That's 8 amps from EACH 12v battery, since they're in series. 8 amps for 1 hour = 8 ah. 8ah is almost depleting those batteries.

If you keep your ride time to something under one hour, you might be ok. Even then, the life of those batteries will be cut pretty short.

If any of this is wrong, I'm sure it will be corrected.

Hey somebody who can speak English! I can almost understand this one. The current lead acid batteries have 10 amp batteries also. So does that mean the batteries in my link should be at least just as good?

Electric bikes are a lot different than electric cars in how you use them. Most of your locomotion is done by pedaling. (After all we can't be too lazy) You use the electric power to give a boost up hills, or maybe help into headwinds, or if you stop suddenly without having a chance to gear down, the electric motor is nice to get you back up to speed. So if you have a battery that will get you 10 miles at 15 miles per hour with zero pedaling, that's only 40 minutes of run time. But using it just as a boost, that means you'll likely have a range of 30 or more miles with several hours of run time.

When the lead acid batteries were new and we did use the bikes, I ran out of juice and rear end capacity before the batteries ever did.

[msmith1199]

StevenH wrote:
What he is saying is not just any 24v Lithium battery will work.

For example a stack of 16 D flashlight batteries (16 x 1.5v =24v) won't work. Two 12v car batteries would because they have enough capacity.

You will have to find one designed to provide the current the motor requires.

Lithium battery will need a different charger than the one for lead acid battery that came with the bike. You need one designed for lithium charge curve.

A lot of expense probably better staying with lead acid, maybe going to a gel or AGM.

One of the reasons we haven't used the bikes much in 10 years is because the lead acid batteries weigh a ton! It's very difficult to even get the bikes into the back of the truck and they are very top heavy. I was thinking about just getting rid of these bikes and buying new ones, but were looking at $1500 or up each for what I would get. So I figured I'd try upgrading these first.

[2oldman]

msmith1199 wrote:
Think they will work? (Li batteries).

The gobbledy-gook is something like this:

One horsepower is 768watts. Divided by 2 (for 0.5 hp) = 368w.
368 watts/24volts = 15 amperes of current. That's assuming your motor is ALWAYS running at 1/2 HP, but I doubt it is.

About those batteries in your link: They are 10ah. They show a discharge rate of 20A max continuous, 60A max 2-second pulse. ... For longest lifetime recommended discharge rate 1-5Amps

My opinion ( and that's all it is):
Let's say your bike draws 8 amps at 24v. (running at 1/4hp) That's 8 amps from EACH 12v battery, since they're in series. 8 amps for 1 hour = 8 ah. 8ah is almost depleting those batteries.

If you keep your ride time to something under one hour, you might be ok. Even then, the life of those batteries will be cut pretty short.

If any of this is wrong, I'm sure it will be corrected.

[SlowBro]

If you do ask there be sure to clearly state that you are new to this. They can get technical, but you are likely to get an accurate answer. I think they'll keep things simple if you make it clear you're no electrician.