Battery question, old vs. new

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mikefish
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Battery question, old vs. new

Hello,

Graduated from 24 volt Ezip to this CL find. 48 volt rear wheel Amped Bikes kit with 8ah Lead acid (near dead) batteries.
Very nice build! I just put street tires on it since I am miles from anything off road.
The speed is better, and more miles to the charge. However this brings me to my question. I am wondering if 48 volt lead acid batteries were replaced with 36 volt LiFePo4 batteries, would I suffer much of a performance hit? I am sure I would gain miles for sure, but would I suffer hill climb, and "off the line" power a lot? These batteries are more than tired. 8ah batteries, that struggle to get me to work at 1.5 miles away, with me pedaling. I am 175lbs my ride has some hills, but not many. The batts can get me there, but if i had to turn around and go back home, they would barely make the 3 mile round trip. I have not tried to push them more than 3 miles because I can feel them drop to almost nothing right near the 3 mile mark.

thanks,

-Mike

colin9876
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Re: Battery question, old vs. new

Your controller may have a Low Voltage Cut off (LV) which means it was sense 36v wasnt enough.

Why not just get a 48v Lifepo4 pack? Why are you keen to go for a lower voltage? If cost is the issue go for a smaller Amphour 48v pack
You will probably see a huge improvement.

If your controller doesnt have a LVC then you could use 36v Lithium, Im sure the performance would be better than what you get now lol!

mikefish
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Re: Battery question, old vs. new

D'oh!

I knew I would forget something! sorry, I did leave out why I am thinking about down grading voltage. Right now, at 80 lbs, she will top out at 26 mph with my 175 lbs added to.. I don't need to go much more than 25 mph, but I do like the torque of the fresh 48 volts after a good charge! ;) Yes, money is another factor. I can get fresh lead acid batts for: 48v 8ah for 70.50 delivered. I like to pedal, so I dont care if its low ah. I would love the weight reduction though!
Amped kits are normally sold as 36v kits. They used to say it can go to 48v, but they just wont cover the warranty if you run 48v. I have not read the site in a while, so maybe the controllers have changed.

colin9876
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Re: Battery question, old vs. new

Ok so as ur saying it was designed for 36v the LVC thing wont be a problem, so u could go 36v or 48v depending on what you can afford.
You will get better performance from a Lifepo4 pack, especially as the batts you have are only 8amphr. Thats because those smaller batts cant deliver as many peak amps without voltage sag, along with the obvious range factor.
I would get at least a 15amphr Lifepo4 if going for a PING, 20amphr if possible - then your current draw rate (how many C) will be less in proportion to pack size.

I made my own pack buying 12 headway cells which were $19 each (10amphr cylindrical). I really like these as they have screw ends that can be connected easily. They can also do 3C discharge so I didnt have any problem with peak amps. Headway now do a 16amphr cylindrical aswell which would give you more!
In my experience they are great cells for bikes. Pings are also good (and come with BMS) but its more fiddly if you ever want to change just one cell, or add a couple of cells etc.
(Ping style packs are inter-connected with soldered tabs and covered in Tape so much harder to get at!)
IMG135.jpg

mikefish
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Re: Battery question, old vs. new

Thanks Colin!

I have been looking at this:

http://www.bmsbattery.com/packs/114-36v10ah-lifepo4-battery-38120-ebike-battery-pack-with-carrier.html

but i hear some negative remarks about the seller, but the price is good.

I dont care if the bikes top speed is only 22mph if i switch to 36v. Oh, and I do like trying to stay a bit stealthy. Living in LA, I am always worried someone may steal components, or the whole bike. A 500 dollar battery that is as big as a shoebox kinda attracts a lot of attention.

I also like Amped bikes tube battery, but its not a LiFePo4 battery, and its on the pricey side for me, but I do love the idea of frame mount.

So in your opinion, do you think I would take much of a torque loss going from 48v 8ah old lead to 36v 10ah LiFePo4?

-Mike

colin9876
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Re: Battery question, old vs. new

Just taken a look at that battery link, looks interesting. Im guessing that uses the cylindrical cells I was talking about?? Price looks very good as 12 Headways would cost you that much alone.
Let us know how it performs if you buy it.

Hey the only way to really tell is try it. You could always add a couple of cells in series with the batt if you find that 36v is not enough.

If u pay the postage I will be happy to send you a few extra Headway cells if u find you need them!

mikefish
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Re: Battery question, old vs. new

Thanks for the offer Colin.

I am not sure I am so technically handy as to do a mod like that on my own.

If I can rake a few more pennies together, I would love to buy that battery and try it out, but I just cant at this time :(

Hopefully things will change soon, and I will be able to test it out!

-Mike

JLGRAU
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Re: Battery question, old vs. new

I think that torque-wise you get nearly the same with 36 & 48 volts. from about 0 to 15 mph the acceleration is almost identical on my Aotema running on both 36 & 48.
So your main issues seem to be: controller compatablity, costs, range, and needs. Acceleration and torque might be more connected to maximum amp draw rather than volts..
Of course, a weighty pack can reduce acceleration.
If you're going to go with lifepo4, make sure the pack has enough amperage to work with the controller.
The BMS on lifepo packs can be sensitive to sudden overdraw and repond by shutting down.

mikefish
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Re: Battery question, old vs. new

Thanks JLGRAU!

Off the line torque for hills, and stop and go riding is what Im most concerned with. Size is next to that. Im leaning towards the 36 volt LiFePo4 so i dont have to carry my charger to work with me, and I wont be worried about ruining the battery if its not charged right away. Now just to get a good deal on a battery. Most likely will not happen any time soon since I have a move coming up in a month. That will consume everything, time, money, energy. I hate moving.

My needs for a battery, would be no more than 10 miles round trip. Stop and go city riding, with me pedaling a good amount. Thats why I dont want a huge battery. I imagine a bike that is light enough to pedal without too much extra weight making it almost pointless to pedal.

I am considering replacing the lead batteries on the bike now, so I can sell it with nearly new batteries, then use the money to build up a bike exactly as I want it.

All this requires free time...which I dont have a bunch of, and as the move date near, I have less and less of.

Thanks again to the replies fellas, helps a lot to have a feedback place1

-Mike

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