Battery source selection

[kafka-cloud]

Hello,

I am looking for a good reliable battery for my to be built ebike. My specific case, I have about a 11km commute for a total of 22km (6.5 miles each way for a total of 13 miles), planning on ether a 36 volt or 48 volt setup. I will be speed limiting at 32 km/h (legal limit). 48v would be for better torque. Small hills mostly coming back from

I do not want to use lipo, because I am not willing to risk possible effect of bad balancing, overcharging or other. I would like to use probably LifePo4 or a similar stable chemistry type. SLA would be too heavy or big.

To be on the safe side I am looking for a 15Ah 36 volt or 10 Ah 48v minimum. And possibly more.

For the source, I've read good and bad review of Ping batteries and after looking at the inside of his packs (after reading about 5 pages on this subject), I am not sure I would like to have this as a battery. I have read some information about Thundersky battery (does this require some form of assembly?) but not enough to select them.

I am ready to get a soldering iron to make some battery if it includes a significantly better price or quality. I've heard about headway cells which I could use 16Ah cells and make a 12sP1(36v) or 16sP1(48V) pack.

I am looking at durability, quality, ease of use, and reasonable price.

Please enlightened me. The more I read on battery, the more I am confused.

Cheers

 

[Samba]

http://endless-sphere.com/forums/viewforum.php?f=14 is a battery-specific forum here.

Hills usually have both an up and a down. If its not especially steep then they tend to balance each other out.

Your 32km speed would take 3-400 watts - lower if you are pedaling, higher if you are carrying extra weight.
400 watts = 11.1amps@36v - 8.3amps@48v.
You are planning on 22km @ 32kmh = 35 minutes at 400 watts = 256 watt hours
256WH = 36v X 7.1AH
256WH = 48V X 5.33AH

If you want the battery to last, you will stop and recharge before its completely drained - you'd get to use about 80% of its total capacity.
As the battery ages it will loose capacity. It should have 80% left after 3 years. So you want to start with one thats bigger so
its still acceptable after it looses some to age.
So you want at least 55% more capacity than you calculate.
36V X 11AH
48V X 8.3 AH

Plan on even more spare capacity if you ride in very cold conditions. If you expect that you'd start exceeding the 32kmh speed over time you would want to plan more spare capacity. (50kmh uses about double the power that 32kmh does - more aerodynamic drag)

Your "15Ah 36 volt or 10 Ah 48v minimum" sounds fine.

The Thundersky are rectangular batteries - i've seen 20AH versions but usually you find them 40AH and up. 40AH - 3.2v Dimensions: H 190mm W 116mm T 46mm 1.6kg http://lithiumstorage.com/index.php?main_page=product_info&cPath=14&products_id=30
They are coming out with 12v packages to replace the lead acid batteries in cars - the EU is outlawing lead acid car batteries? they look like 4 of the regular 3.2v rectangular batteries in a larger package - But I haven't seen a good spec sheet yet. http://www.thunder-sky.com/products_en.asp?fid=66&fid2=82
The Headway are cylinders 38-42mm diameter and 120-160mm long. 8-16AH http://www.batteryspace.com/LiFePO4-40160S-Battery-12.8V-16Ah-204.8Wh-160A-rate-19.2.aspx Both use screw/bolt type terminals - use flat buss straps or large wire to interconnect them. Crimp-on ring ends work fine - you can do it with no soldering.

Ping uses pouch type LiFe - 5AH each so their batteries would be like 12s3p.
Many battery packs this size use smaller cells like 3AH cylindrical 26650 (26mm dia, 650mm length) cells.

 

[dogman dan]

15 AH size is good for commuters. You could go smaller with better cells, like A123, headways, etc. Especially if you charge at work. But you'll find the long way home a joy if you have at least 15 ah of battery

Pings definitely have limitations. But if you run a 20 amp controller on a 1000 watt motor, It's hard to beat the 48v 15 ah ping. The big downside for ping isn't reliablility, its carrying it if it doesn't fit in your frame triangle.

You might really want to look again at lipo. 12s lipo in 15 ah size would be really easy to carry on the bike, and two chargers would make charging it a snap. You'd only need to charge at home.

 

[max]

dogman
Do you think a my1020 36v 1000w + a yiyun 36v 800w ctrler + mrpings 36v 20ah lipo4 is ok.
I set fire to my last motor a my1020 750w36v and i found it was only runing on 3 bush's the 4th was never dropt onto motor arm in factory.
I just instald the 1000w but i remember trying this 1000w with a 1000w yiyun and my ping tript out.To big a amp pull.
I just did a test run 20 foot.and it pulls real good.on 800wctrlr.
This is why im askin if its ok.
Your coment above says you think this setup is good but u have 48v's/15ah .i only have 36v 20ah setup.

Thanks .
max midlands uk

 

[Jeremy Harris]

Max,

I'll admit to struggling a bit to understand your post, but here's what I think you might be asking:

1. I think you are running an MY1027 brushed motor, with a Yiyun 36V 800W (so presumably around 22A) controller and a Ping 36V, 20Ah LiFePO4 battery pack. Is this right?

If so, then the Ping pack will be fine at this current level. Generally, the Ping pouch type packs are OK up to about 2C maximum (40A in your case) but are best run at around 1C to 1.5C (20A to 30A for your 20Ah pack).

2. I think that you are trying to tell us that you had a burnt out MY1020 brushed motor and that you believe this to have been caused by one of the four motor brushes not being correctly fitted. If I've understood you correctly, then I think you believe that the faulty brush wasn't contacting the commutator properly, is this right?

If so, then the motor would have run way below its rated performance, and you may well be right about it being the cause of the failure.

3. I think that you're trying to tell us that you have/had a problem with the MY1020 and a 1000W (so presumably ~27A) Yiyun brushed motor controller. The problem seems to be the current limit on the Ping BMS tripping, which would indicate that this controller is really trying to pull at least 40 to 60A from the battery (I believe that the 20Ah Ping packs have a 40A continuous, 60A maximum rating).

If the current limit on the Ping BMS is tripping, then the controller is really trying to deliver around 2000W or so to the motor. It may be that this controller doesn't have any, or any adequate, form of current limiting, in which case it may well be that the motor will try and draw that sort of current, causing the Ping BMS to shut down.

In general terms, the sort of power that you are trying to pull from the battery pack you have is fine. A 36V 20Ah Ping pack should be OK up to around 800 to 1000W or so, although will struggle to deliver anything much above this.

Sorry if I've misunderstood your request, I'm afraid that I did struggle a bit to try and understand exactly what it is that your asking.

Jeremy

 

[max]

thanks Jeremy.
you are corect/
My my1020 brusht 36v 750w motor bernt out on 3 brush's so i swopt it for a my1020 36v 1000w.brusht motor.
Runing off a yiyun 36v 800w controler. and ping 36v 20ah.
realy my qeustion was concerning the motor pulling big amp and blowing my controler or shuting down the batt.
But going by what you said i will be ok.
I connot bleave i was runing my old motor for 2 years on 3 bush's.
Thanks again for your help you'v set my mind at ease now thanks.
All i need to do now is line the drive train up and test run my new 1000w motor on 4 bush's arrg
The thing is i was happy with the power levals on my old blowd 750w motor runing off 3bush's.
This 1000w on 4 bush will be a MONSTA !!!! hehe carnt w8 to ride now.
thanks again.
max
midlands uk

 

[dogman dan]

I put 2000 miles on my first ping, a 36v 20 ah v1, using a 35 amp controller and aotema brushed controller. I did have problems from time to time with the controller getting hot and shutting down, but the battery was fine, and still is now with nearly 6000 miles on it.

So I'd say yeah, you will be ok Max, depending on how you ride. Too steep hills, or a stop sign every corner can really hammer the battery. But if your ride is more normal, like cruising at full throttle most of the time you should be fine. And of course, keeping the depth of discharge no more than 80% most of the time will help a lot too, if you do that.

And unfortunately, one stinker cell in a battery changes everything. So that's still a possibility even if you baby the battery. I just spent half of yesterday trying to rebalance a lipo pack that had one whacky cell.

But the less efficient brushed motor will hit the battery harder than a brushless one, since you need extra amps to make all that heat.

 

[morph999]

Oh boy, I had some big post written and I lost it all.

Ok, I own the Thundersky batteries. I like them. They are probably the best value for lifepo4 on the internet as long as you can find them for around $120 or less per 12v20AH pack or $360 for a 36v20AH pack. The only drawback is that they are kind of bulky. They are about as big as a 48v9AH SLA pack but at half the weight. They are still lightweight but they seem take up a lot of room because of the extra plastic and stuff I guess. I didn't have to do any soldering, just a lot of crimping to put the pack together. I made a trip to radio shack to get some ring terminals and some wire from Lowes and that was about it. After over 500 miles and 10 months, the batteries are doing just fine. I use a 35 amp controller.

 

[RICK]

my 15 ah 48 v ping has held up fine through one season (on a 9c), a little over 2k mi so far. no headaches at all, just works. get 2 chargers leave 1 at work - i've heard the chargers don't travel well..

 

[dnmun]

i started that rumor.

my idea is that because the charger transformer is super heavy and is mounted in the middle of the pcb, when the charger is shaking while traveling on the bike, the mass of the transformer is causing the pcb to flex a bunch and this can cause the small surface mount capacitors and resistors to break internally because they are fixed to the surface of the pcb and are rigid themselves.

leave the cheap one at work so you won't miss it when it is stolen.