# Newbie help: Batteries for my 600Watt Schwinn Scooter.



## dskippy (Feb 11, 2010)

Hey everyone,

I just found this forum. Nice community. This is my first post. I am looking for some advice on batteries for a scooter I am improving.

I recently found a Schwinn S180 in the trash with no batteries, motor, or motor controller. I got a 24V 600 Watt DC brushless motor and a motor controller suitable for a 600W motor.

Now the problem part. I ordered four of these 12V 22Ah lead acid batteries:
http://www.monsterscooterparts.com/24-volt-20-ah-22-ah-mobility-battery-pack.html

I figured I'd put two in series and those two pairs in parallel for 24V at 44Ah. The problem is that the batteries cannot discharge more than 6.6A of current. This means my motor is only getting half power. I could get four more of these batteries, because I need roughly 25A of current, but 88Ah is excessive and way too heavy for my purposes.

I thought about getting, instead, eight of the 10Ah ones. But they can only discharge 2A, so that doesn't help at all.

I am now considering LiFeYPO4 batteries. Particularly the 40Ah cells from from EVComponents.
http://www.evcomponents.com/ProductDetails.asp?ProductCode=TS-LFP40AHA

Their rating is for "< 3CA constant current" and "<20CA impulse current". I don't know what this means. I am pretty sure that the lead acid batteries having printed "cycle use initial current = 6.6A" and "stand-by use initial current = 3.3A" that that means I'll be able to get 6.6A while riding. What does "<3CA" mean? Is constant current what I'd be using when I was riding along? Will 8 of these batteries in series make my 600W motor get max power?

I am really new to LiFeYPO4 and I'm not sure how to use them. I have read a little bit about needing to have a BMS between my batteries and the load so that I don't over discharge a cell. Are there BMS that would be suitable for a scooter? The chargers on evcomponents are really expensive ($2k) but I've seen some on line for $70. Does anyone have an recommendations for me?

Basically what I want from my batteries is this:
* 600W of power. A 24V system able to push 25A of current.
* At least 35Ah of storage. Preferably somewhere around 50Ah.
* <60lbs worth of battery
* < $500 total cost of the system

Any suggestions? Thanks for reading. I'll post pictures, videos, and a parts summary/how-to to my blog and this forum when I'm done.

-mike


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## EV-propulsion.com (Jun 1, 2009)

I'm not sure how you came up with the 6.6 amp discharge limit, but with an AGM lead acid battery (which this is), you should easily be able to pull 5C out of it, in this case 110 Amps (although with some voltage sag). You may be reading maximum charge amperage to get that 6.6 number.
Mike
www.EV-propulsion.com


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## dskippy (Feb 11, 2010)

I got 6.6 from information I'm not quite able to understand on the battery itself.

There is a table that says this: (written in comma-separated values but on the battery it's a table)

Constant voltage charge at 20 degrees Celsius,Voltage Regulation,Initial Current
Standyby usage,13.6V-13.8V,3.3A
Cyclic use,14.5V-14.9,6.6A

Is that charge or usage info? What's the difference between standby and cyclic?

Lead-Acid AGM batteries will give me 5C of current? I just learned what 5C means. It's very hard to Google for. Here's the issue, in terms of what I really know, not speculation:

I put four batteries (2 series, 2 pairs in parallel) on the scooter with a 600W motor. Going down a very, very slight hill is quite speedy. Going back up that same, very slight hill, is impossible. The scooter just gets no torque. I figured this was because my batteries were only providing half the current. I didn't consider the possibility that gearing is all wrong for the 600W motor but I suppose that's possible. It's the same gear used for the 180W motor. I figured with a 600W motor, if anything, I'd be getting more torque and the same top speed. So I don't quite understand the torque problem I'm seeing.

Any thoughts on that?

-mike


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## EV-propulsion.com (Jun 1, 2009)

That is charge current. Standby is the "float" charge maximum, meaning if left on charge it should be 13.7 volts. It sounds like you have been using a 180w motor, how did that perform? Also, are you using a speed control with this, or just on-off? What are the specs for the speed control, if used? Putting a temporary ammeter and voltmeter in the system would really help, to see what is going on electrically.....
Mike
www.EV-propulsion.com


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## dskippy (Feb 11, 2010)

I didn't use the 180W motor, so I don't know. What I was saying earlier which was a little confusing, is that the sprockets were designed for a 180W motor so I don't see why the 600W motor should get what, I imagine, is a lot less power. I mean this thing can't get up a tiny, tiny incline. So I don't know if the 180W even worse but I imagine this thing is either not getting current, or is geared way out of whack.

I am using a motor controller is this one:
Z09-1666 - Currie 24V 25A (22A) 3-Pin Controller
http://www.monsterscooterparts.com/cu24v25aco.html
I don't know what that (22A) is all about, but it should be providing exactly 600W on full throttle.

You're totally right about amp-metering the system. I'll do that now and see what I come up with. I'll post back when I've figured out how many amps are going to the motor and also how many are going into the controller.

-mike


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## dskippy (Feb 11, 2010)

Oh the batteries fit very nicely in any number of ways. I currently have then all four lines up on the platform where one's feet usually go. I have then just sitting in the cardboard boxes they were shipped in. I plan to make a more permanent case for them soon. My feet will now go on pegs that I'll put on there coming out the sides. Here's a picture of a some other guy's mod where he put way more batteries on there than I even came close to:

http://www.evalbum.com/img/1265/1265a.jpg

I got the peg idea from him. My scooter is missing its floor actually. I think I'll just make a new one, but make it one foot's width wider than my batteries on either side.

Regarding the electrical, I unfortunately don't have an amp meter rated up to 25A so I will have to wait to borrow one before I can post what's going on with my motor's power.

-mike


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## MN Driver (Sep 29, 2009)

It sounds like the controller you have isn't pumping enough amperage into that motor of yours. I'm not sure why there it is listed as 25A (22A) on that site, but if it is only providing roughly 20-25 amps this is likely the source of weekness climbing hills. You might benefit from going over the motors amperage rating and get a 30 amp controller.
I've bought controllers from TNC Scooters before and they have been helpful, even sent them an email once and got an answer back. When I asked questions they seemed to have a pretty good idea of what they were selling and gave me a suggestion based on what my criteria was for a controller and I've been plenty satisfied with their service. You want to make sure that if you go this route you aren't getting the motor hot when you run it hard. Also make sure that you get one that is compatible with the type of throttle you are using, the wiring diagrams should help with that, make sure everything else as far as connections go look compatible.
http://tncscooters.com/partsdb.php?type=ES


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## dskippy (Feb 11, 2010)

I have put a voltmeter and an amp meter to my scooter and I have found out somethings about what's going on. Though I still don't know why.

I did a bunch of test. Amp and volt meter between batteries and controller, between controller and motor, and also connecting the batteries directly to the motor (with the amp meter in the circuit. The results were always the same:

25.2V at 5A

I am expecting this thing to draw 25A. This is consistent with the fact that the scooters power, when riding around, is roughly 1/5 of what I would expect. The question is why?

The batteries I have are (as stated above with links) four 22Ah batteries connect two in series and those pairs in parallel. The motor is labeled 600W, 24V (which amounts to 25A. It does say on the label that it's maximum amp rating is 36A. Why would that be different from 600W/24V? Is that just the max it can take iwithout burning out? Is a 600W motor actually a 24V*36A=864W motor?

I think we can take the motor controller out of the equation for the moment, since this behavior without it is already very strange. Anyone have any tips?

Oh, by the way, I did sit on the scooter, so that the motor would have a hard time spinning the wheel. I figured making it harder to turn the wheel would increase the current draw, but it did not.

Thanks a bunch,
-mike


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## EV-propulsion.com (Jun 1, 2009)

What size wire are you using from the batteries to the motor? And what is the voltage of the batteries when they are hooked up to the motor with you sitting on it trying to move the bike? Something is definitely restricting power- with the motor hooked up direct to the batteries and the motor having a big load on it (trying to move the bike with you on it (not meant in an offensive way,btw)) the current draw should be pretty high...
Mike
www.EV-propulsion.com


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## dskippy (Feb 11, 2010)

Actually that quite likely could be the problem. I have really small gauge wire. I am not sure the gauge. I'm using some 22 or 18 gauge for part of it. The rest is speaker wire. I figured it'd just burn up if I put too much current through it. Not keep the current from flowing through. I'm going to try replacing all the small wire. Do you have a recommendation for the gauge of wire I'll need?

-mike

p.s. The voltage across the batteries when I sit on it is 25.2V as expected.


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## EV-propulsion.com (Jun 1, 2009)

I would use # 8 wire on all the high current wiring and try it. Make sure you have good, solid connections too. Any switches or relays have to be able to handle the highest expected DC current also. Oh, don't forget a fuse too.
Mike
www.EV-propulsion.com


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## MN Driver (Sep 29, 2009)

dskippy said:


> Actually that quite likely could be the problem. I have really small gauge wire. I am not sure the gauge. I'm using some 22 or 18 gauge for part of it. The rest is speaker wire. I figured it'd just burn up if I put too much current through it. Not keep the current from flowing through. I'm going to try replacing all the small wire. Do you have a recommendation for the gauge of wire I'll need?
> 
> -mike
> 
> p.s. The voltage across the batteries when I sit on it is 25.2V as expected.


18 gauge is too thin for the amperage you are trying to push through the wires. I've been using 8 gauge for 30 amps. I've played with 10 gauge aluminum that I got for a song but that stuff gets warmer than I feel is right for my ~30 amp draws. For the relatively short runs involved with a scooter, I think that 8 gauge wire would be a small part of the cost involved with this scooter. If you take a look at the size of wire coming out of the motor, if it is stamped with the gauge size, it is likely going to be 8 gauge, if it is larger than 8 gauge, I'd go with the same thicker size that it is using. Otherwise I'd go with 8 gauge myself.


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## dskippy (Feb 11, 2010)

My motor controller blew up. The saga continues...

I got myself some 12 gauge wire to replace all of the 18 gauge wire I that I had. That turned out to work *fairly* well. It brought the current up to 15A, which is great. I went scooting around and made it all the way to RadioShack to get 10 gauge wire which I didn't have any of. I replaced all of the wire with ten gauge and my motor controller blew up.

It popped and then smoke came out of it. I am pretty sure it's dead now. I don't understand quite why this happens, honestly. I thought that the controller would be happy to be provided plenty of current and only use what the motor needed to draw. I should take EV-Propulsion's advice and put a fuse in there next time. But then wouldn't I just keep blowing the fuse? What exactly is going on in there? How much current do I need and how much is too much? What kind of fuse should I put on there?

I'm planning to take everyone's advice at get 8 gauge wire. I got 10 because I didn't want to wait for shipping. I read some tables of wire gauge and current. Looks like 10 gauge only allows 14.8A to go threw. Why would that blow my controller? Is everyone agreed that 8 gauge is correct? That will carry 24A when really I'm going for 25A. Is 7 gauge necessary?

Most importantly what should get for a motor controller now that mine is dead and how should I make sure I don't kill the next one?

Thanks,
-mike


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