Help choosing battery pack

[bleejean]

Hello
I have a Canadian Tire izip bike and currently I have a battery pack with two yardworks power tool batteries inside, hooked up in series. Each battery is 20v 6ah so my battery pack is 40v 6ah.

Recently one of the batteries in the pack has stopped charging and in case I can't get it working again, I am investigating possibilities for a replacement battery pack. I found a battery that seems to fit my needs and I just wanted some people with more experience than I to take a look and see what they think. It is this battery here:
http://www.batteryspace.com/lifepo4-battery-51.2v-6.6ah-337wh-30a-rate-with-pcm.aspxhttp://www.batteryspace.com/lifepo4-battery-51.2v-6.6ah-337wh-30a-rate-with-pcm.aspx

Since it is a bit higher voltage and amp hour, and also LiFePO4, am I correct in expecting that it should perform a bit better and likely last much longer than my current batteries (Lithium Manganese I think)?

Thanks for sharing your insight!

 

[wesnewell]

Here's a corrected link to the pack.
http://www.batteryspace.com/LiFePO4-Battery-51.2V-6.6Ah-337Wh-30A-rate-with-PCM.aspx
If your controller draws 30A max or less it should work fine. Short burst to 40A shouldn't hurt it either. You need to make sure your controller will work with the higher voltage (about 58V). As for 2000 cycle life4, you can probably forget that. If you note in the specs, that's based on a .2C rate, which is 1.32A. Even with a very conservative controller, you'll probably pull 10 times that on takeoff, and likely more like 20 times that, and probably 5 times or more that at cruise speed. I wouldn't expect more than 400 cycles out of it on your bike, if that. And it's very expensive for such a small battery pack. There are many better and less expensive options.
Cycle life
> 2000 cycles (80% of initial capacity @ 0.2C rate, IEC Standard)
2 times more than NiMH and 10 time more than SLA )
Forgot this.
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[dogman dan]

I would call two of those in paralell adequate for an Izip. 6 ah is going to only put out 6-10 amps reliably. Any more will damage the cells eventually.

Anybody disagree that that pack must contain 2c cells? That means 1.5c should be your max continuous amp IMO.

Might look at a price on a 36v 10 ah pingbattery before you pull the trigger on that one.

Do you know what your amps usage generally is? It could be 6-10 amps, but most pull more getting started, or climbing a steep hill.

 

[bleejean]

Thanks for the replies!

Forgive my ignorance, but if my current pack is 6ah and it is adequate, wouldn't this 6.6ah pack be fine?
I was looking at the pingbattery site (http://www.pingbattery.com/servlet/the-13/48V-10AH-V2.5-LiFePO4/Detail) and maybe I am not comparing the right numbers but it seemed that it didn't deliver as much amperage? The bateryspace pack says it does 30A and the pingbattery pack says 10A if I am reading correctly.

Since my current pack is 40v (a kind of odd number) I think I would rather replace it with a 48v pack to get a bit more speed rather than a 36v pack (and I have read on forums of people using a 60v pack with a Canadian Tire izip successfully).

As for lifetime, I want a long life and I am expecting a LiFePO4 pack to last a lot longer than my current pack but maybe that is not realistic. My current pack has been in use for 4 years now and I think it would keep going if it wasn't for my accidentally damaging one of the batteries inside.

Anyways, I am hoping to find a solution for a new pack and charger for around $400 and I would value your continued input.

 

[wesnewell]

All you need to be concerned with is that your controller won't draw more amps than your battery pack is rated for and the battery pack does not exceed the maximum voltage your controller can take. Meet those two things and you won't have a problem. Your pack was 240Wh (40V x 6AH). So if you need the same range, make sure your new pack is at least that big. There's literally hundreds of choices. Personally, I'd get a 12s rc charger and and 5-10ah of 12s rc lipo. That would be rated for 100-200A draw, have a nominal voltage of 44.4V and a charged voltage of 50.4V. Properly handled it should last 3-6 years, and cost about $300 for a 10ah pack and charger setup.

 

[friendly1uk]

I agree with Wesnewell. In fact it is what I'm using. 12s of 5Ah RC lipo from hobby king gives me 44.4v for about $85 delivered. Don't get excited though, a 240w charger takes 90 mins and costs me $60 delivered from ebay. A bms a further $60 from perhaps http://bestekpower.com/ But from then on you just have your $85 cells to replace.

Not every country gets good prices from HK due to disposal costs being built in to the sales price in many regions.

 

[Tommy L]

I sent you a PM check your messages

Tommy L sends....

 

[bleejean]

Thanks for the recommendations.

I am very interested but I am afraid that I might be too much of a noob to pull this off. The "12s of 5ah RC lipo" that you refer to, they are individual battery cells that I would need to connect together with a bms to create a pack right?

I searched on hobby king but couldn't figure out which one you were referring to friendly1uk. I browsed for lipoly (is that the same as lipo?) and then selected 12s and the one for 5000mah was $259.99 and not $85 as you said. Am I looking in the wrong section?

Also, if I am correct about your recommendation being a bunch of cells, are there simple wiring instructions for creating a battery pack somewhere? How do I choose an appropriate bms and charger? Would it be too much to ask for you to post links to products similar to what you used?

I don't mind spending around $300 if I can get a bit longer usage time out of the battery pack so if anyone can post links to the products I would need to accomplish that (wesnewell, you were saying I could get a good 10ah set-up for around $300) I would really appreciate it.

Thanks again everyone for trying to help me out!

 

[bleejean]

Ok, I did a bit more research about lipo batteries and I think I understand a bit better now but I still have a few questions.

If I want to make a 44.4v pack with 10ah I can buy 4 6s 5000mah lipos and then connect 2 in series and 2 in parallel, correct?
I have been looking at these ones here: http://www.hobbyking.com/hobbyking/...lightmax_5000mAh_6S1P_25C_USA_Warehouse_.html

If that is the case, is there a charger that can charge the whole pack at once or would I need to charge each of the 4 subpacks individually? What should I look for in a charger? Can you recommend one?

And lastly, how do I choose a bms? Are they easy to wire?

Thanks!

 

[wesnewell]

Yes, 4 of those 5ah 6s packs will make a 10ah 12s2p 44.4V pack in abut 2 minutes if you know what you're doing. Maybe 10 minutes if not. Wire them like this.

And charge as a single pack with this charger or any 12s charger.
http://www.hobbypartz.com/75p-1220-charger.html?gclid=CNa3z9_N57ICFayPPAod10MAPw
You'll need 2 of these to paralleling balance leads and chargeing.
http://www.hobbyking.com/hobbyking/store/__27080__JST_XH_Parallel_Balance_Lead_6S_250mm_2xJST_XH_.html
And lastly, you do not want or need a bms. The charger has a built in balancer to balance the pack when charging. This would be a good addition to monitor voltages while riding.
http://www.ebay.com/itm/Waterproof-Digital-Voltmeter-DC-15V-To-120V-Red-Led-Voltage-Digital-Panel-Meter-/170846310527

 

[bleejean]

Cool. Thanks for the picture and the info!

For wiring the battery for charging do I just need to plug 2 of the balancing wire harnesses into the charger (is that what the balancing leads are for?)? That would be the 2 from either both of the top 6s packs or bottom 6s packs in the picture right?

Would it be a good idea to also order some lipo flame resistance bags to store the packs in? I plan on putting all the packs in a big plastic case that fits on my bike and originally had sla batteries inside.

Is this (http://www.hobbypartz.com/73p-t350-power.html) a suitable power supply for the charger you recommended?

 

[wesnewell]

Yes, once you put the pack together, you'll have only 2 balance plugs since you'll parallel the 2 from each side together using the 2x parallel balance cables. They stay like that forever unless you need to replace a pack or something. The negative side of the battery pack is called the low side and the positive is the high side. Make sure you plug them in that way are the balance will be off. Low side goes to the balance port starting with cell 1.
Where you store them is up to you. I leave my pack on the bike most of the time and sit it on my wooden computer desk when I charge it. I'm not too worried about it to be honest.
That power supply is fine. A little expensive for my taste, but it will certainly work. I'd look for the best price for all this stuff. These were just links to items, not vender recommendations. I bought my 600W power supply used for $10 over 2 years ago and it's still going strong.

 

[bleejean]

Thanks for your patience with all my questions (I now realize how dumb some if them were).

I have one last question (hopefully, though I would like to post links to the items I choose after some more research if you wouldn't mind double checking the setup). I read that if lipos discharge too much they will be ruined. How do I make sure that they don't discharge too much while I am riding? Will they just stop providing power and the bike motor will stop automatically? Is that what a bms is for?

Thanks again. I appreciate all the help you have given me.

 

[MikeFairbanks]

Yes, the bms prevents you from completely draining your battery. It will cut off when there is only a certain percentage left.

A lot of guys order the cycle analyst from ebike.ca. It tells you how much power you have left and more. It's a dashboard for your bike.

Those ping batteries are good batteries, and they come ready to go. No worrying about wiring, charging time, etc. Just charge it and go.

 

[friendly1uk]

33% extra, For Free! http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=18631

You would want 3 of these, shown for simplicity. http://www.ebay.co.uk/itm/4S-JST-XH-Balance-Parallel-Wire-Adapter-to-2-Output-14-8v-Lipo-Battery-Balancer-/151090192433?pt=AU_Toys_Hobbies_Radio_Controlled_Vehicles&hash=item232dad6031

The charger never see's the balance leads. That is model car stuff(imo). The bms board watch's the cells. http://www.bestekpower.com/444v12spcmbmspcbforli-ionli-polymerbatterypack/

This is what go on (ish)

Looking at the 4s batteries and leads I have posted, can you see how it all works? Your extending the balance wires seen here, from the original cells as shown, and onwards to there parallel partners. You can add as many parallel cells as you like, and the bms will watch all of them, all the time.

http://www.greenbikekit.com/index.php/battery-charger/240w-lithium-ion-battery-charger.html 50.4V

 

[wesnewell]

1.How do I make sure that they don't discharge too much while I am riding? 2.Will they just stop providing power and the bike motor will stop automatically? 3.Is that what a bms is for?

1. Buy that voltage meter off ebay I posted earlier. When you get down to 42-43V stop using the battery until you recharge it. Or set controller LVC to 42V if you know how.
2. Relates to 1.They will continue providing power until controller LVC is reached, at which point the controller will no longer use the battery.
3. No. It's supposed to protect individual battery cells be being over discharged, but does a poor job imo. It also is supposed to balance the pack when charging, but also does a poor job of that imo. And it's supposed to keep you from overcharging individual cells, but also does a poor job of that imo. I will provide your pack with extra wiring, weight, and volume, and a greater chance for short and fire imo. It will also limit your battery amp out. And that's just a fact. The only thing it will do is provide a single point charge port. In case you can't tell, I don't like BMS's. For RC lipo I view them as a complete waste.

 

[bleejean]

Now I am not sure what to do. I don't really feel comfortable relying on watching a voltage meter to determine when to stop using my battery. At the same time I am pretty intimidated by the thought of wiring up all those smaller packs with a bms to make a battery that can self monitor when to stop supplying voltage.

Maybe I would be better off with a simpler pre-made pack after all? By the time I buy all the parts and get them shipped from different locations, the price will likely come out similar anyways.

What if I went with this battery http://www.greenbikekit.com/index.php/48v-10ah-headway-38120-battery.html and the charger friendly1uk mentioned? Or would this battery http://www.pingbattery.com/servlet/the-13/48V-10AH-V2.5-LiFePO4/Detail be better?

I am not trying to disregard anyone's advice (really, thanks for the input!) but I need to make sure that the solution I go with isn't something that I can screw up too easily.

 

[wesnewell]

Now I am not sure what to do. I don't really feel comfortable relying on watching a voltage meter to determine when to stop using my battery.

Do you feel the same way about the gas gauge on your car/truck/motorcycle/whatever? BTW, with a prebuilt pack with a bms, you're still going to need some sort of energy gauge to watch. Otherwise you you'll never know the state of your pack and the bike will just quit on you wherever it is when the BMS reads a low cell. With a voltmeter and lipo you know how full or empty your tank is.

 

[bleejean]

I see your point but I don't think it is an apt comparison. When my car runs out of gas it doesn't need to have the entire fuel system replaced. I can just put in more gas and be on my way. I have been using my ebike for 4-5 years so far without a gauge of any sort and you get to know the range of the battery pretty quickly. On the rare occasion that my battery dies while I am out riding, I just peddle myself home.

Are you convinced that a lipo battery set up made from rc/helicopter packs will really give that much better performance than a premade pack? As I mentioned before, I think after shipping the cost would likely be about the same either way.

 

[dnmun]

why not post up pictures of your battery and the BMS so we can help you fix it?

most likely there is nothing seriously wrong if the other one still works.

do you have a voltmeter and a watt meter?

 

[wesnewell]

I started with SLA. After a week, I knew I wanted to go to lithium. I researched both lifepo4 and rc lipo (a lot) and came to the conclusion that rc lipo was by far the best choice. I haven't changed my mind. Simplicity, size, weight, flexibility, energy density, and cost were major factors in my choice. I've yet to hear of a lifepo4 pack that cost twice as much even come close to the rated life cycle, while I've heard of lipo packs with close to 1000 cycles on them. As I summized when doing my research, a 3-4C load on a 20C pack is nothing and will extend its life, while the same load on a 1-2C lifepo4 pack will shorten it considerably. That has been proven true from what I've read here about pack failures.

 

[bleejean]

@dnmun: I think fixing it would be beyond my ability. I'll let you know what happened though in case it helps.

I have the 2 packs wired in series and they output to the bike. Each individual pack also has its own charging circuit and I use two chargers. I used Anderson pole connectors to connect the packs to the chargers. Last week, after charging, I unhooked the wires to the chargers but instead of pulling on both sides of the connectors like I should have, I pulled on the wires and the wires on the battery side pulled out from the connectors and touched each other creating a big spark!

I have a multimeter and when I check the charging circuit of pack #1 it reads 20v. Pack #2 (the one that shorted) reads 0v. Yet the battery output to the bike reads 40v still. I thought I could keep using the battery at half strength but, although the charger will still charge pack #1, the battery doesn't power the bike anymore. I do suspect that I could use it a bit if I tried right after pack #1 finished charging but by the time I go to use it, it is dead again.

I don't think I would have any luck attempting a repair. There is a circuit board thing on each pack (bms?) but they are covered in a clear thick gel that protects the board.

Maybe it would be best to just buy two more of these yard tool batteries (I think combining one new one with a 4 year old one would be a bad idea?)? They only cost $120 each and I already have the chargers and a likelihood of getting at least 4 years out of them.

@wesnewell: Very interesting. You make compelling points and I will consider them carefully. You mentioned before that I could expect a 3-6 year lifespan out of a rc lipo battery. I wonder if I should stick with my lithium yard tool packs as I have already had personal experience of them lasting 4 years and they likely would end up being a lot cheaper. The downside is that I would be really excited to try a pack with a bit stronger voltage (though my bike was already faster than is technically street legal).

 

[friendly1uk]

I am pretty intimidated by the thought of wiring up all those smaller packs with a bms to make a battery that can self monitor when to stop supplying voltage.

You have to connect everything just the once. If you use a balance charger you connect everything every time you charge. The eventuality of which is getting it wrong.

It will also limit your battery amp out. And that's just a fact.

Which is a good thing, right? They protect against overload and short circuit. They don't limit what you actually need though.
My bms is tiny. Most are just a circuit board occupying very little space compared to multiple devices with screens on.
It weighs 36g complete with pack temperature sensor. Something used to limit currant when your cells are struggling. More protection a voltmeter can't offer.

If I wanted 300 amps I might just use a basic 15 amp bms without the lvc as a 300 amp bms is getting quite big and costly. I would still use one though because it is easy. Wire it all up just once, then in future it is as hard to charge as your phone. For lvc I could then use a cheap model plane type buzzer, and perhaps just listen, or wire in a contactor. Anything to make sure I get every level of protection possible, and a proper charging solution that does not require moving dangerous wires about every day.

 

[wesnewell]

FYI, you can use a single plug connection point to balance charge a lipo pack up to 14s using a hyperion 1420i, or 12s using the thunder 1220. It's not that hard to do. Some here have done it. It's very simple to do.