Newbie need help buying battery

[thatguy]

Hi everyone,

Complete newbie here. I need some help with buying a battery.

I bought a new ebike from a local shop going out of business but it didn't come with a battery (owner says the batteries were too old and basically dead, but he did give a good deal on the ebike). I've been told it's a 350w rear hub planetary gear motor, the controller is rated at around 22 to 25amps, and I need a 36v battery.

For me to get to work is 15km one way with hills. I want to pedal but I don't want to break into a sweat. At this point I'm looking into a lifepo4 36v12ah or 36v15ah as I assume 36v10ah might not be sufficient for a round trip. How am I doing so far?

http://www.greenbikekit.com/lithium-battery/lifepo4/36v-15ah-headway-40152-battery-pack.html

This pack appears to be cheapest, good quality, high C rating and relatively reliable reseller. To purchase, you have to select a discharge current: 20/40a, 30/60a or 50/100a. Which one do I select? Does this pack include a BMS, a connector and a case, or is this a DIY kit? Other than a charger, do I need anything else to connect this pack to my ebike? How is this pack so much cheaper than what I can get locally in Vancouver, Canada? Even if you add shipping and VAT charges, it's still way cheaper. From what I've read, international delivery of lithiums (hazardous goods) is an issue. Is this still the case from China to Canada?

If the above pack doesn't work, will this one work?
http://em3ev.com/store/index.php?route=product/product&path=35&product_id=160

These guys are local for me which is great, but price is double when you include taxes and it's currently out of stock:
http://www.ebikes.ca/shop/ebike-parts/batteries/b3614lim-ez.html

After hours of reading ebike forums, I must admit it's too much info and difficult to determine what is the latest news. Thanks in advance for any help on this.

 

[dogman dan]

The headway pack should work ok. 20-40 amps bms will match your 22 amp controller.

36v 15 ah will be a good size. You should have the full 30 k range, if you limit your speed to about 20 mph.

EM3ev is selling a very good battery too, if you have that in the budget.

Pingbattery.com is an old but reliable source for a different lifepo4 pack. You could get a 20 ah from him, and really have some good range.

 

[DAND214]

If yoou have room in the triangle, i would go for the EM#evbattery. you will need a charger also.

That's just my choice. And it does cost more for the AH neeeded.

Dan

 

[thatguy]

Ok, I think I get it, thanks for all input. Considering I paid $100 for the ebike, I'm not looking to spend $800+ on a battery.

http://www.greenbikekit.com/lithium-battery/lifepo4/36v-15ah-headway-40152-battery-pack.html
So, for this pack, you select the proper BMS to control the battery discharge based on your rated controller. I assume they put it all together for me, but I'll contact the reseller to ensure this is the case. As far as an outer protective case goes, where do I get one if it doesn't come with it? Do you need a case with a built-in fan for this type of battery?

http://www.greenbikekit.com/battery-charger.html
When I look at the battery chargers, they are rated by watts. How do I calculate how long a 240w charger will take to charge the above 36v-15ah-headway battery pack?

http://www.greenbikekit.com/battery-charger/240w-lithium-ion-battery-charger.html
Lastly, based on the required fields to purchase this charger, what "charging voltage" and "DC connector" do I need? My ebike has a computer power plug coming out of the controller which I assume should plug into the battery. It's probably non-standard so I assume I can order whatever the default DC connector is, then cut off the power cord plug and reattach??

Thanks

 

[teslanv]

Ok, I think I get it, thanks for all input. Considering I paid $100 for the ebike, I'm not looking to spend $800+ on a battery.

The Battery is the heart of the ebike. Further, a GOOD battery can move from your "starter" ebike to your "advanced" ebike, if you choose wisely. - A poor battery choice will leave you disappointed in the entire technology, and you may inappropriately decide that ebikes are not worthwhile.

When I look at the battery chargers, they are rated by watts. How do I calculate how long a 240w charger will take to charge the above 36v-15ah-headway battery pack?

It is best to think of batteries in terms of Watt-hours of capacity. To find out how many watt-hours a battery has, multiply Voltage X Amp-Hours. - So the 36V 15Ah battery is (36X15) = 540 Watt-hours. - If you use a 240 watt charger it will take (540/240) or about 2.25 Hours to charge it. - it will actually take a bit longer, since as the battery gets close to "full" the wattage of the charger will reduce until the battery is 100% full. So more like 3 hours to charge.

Lastly, based on the required fields to purchase this charger, what "charging voltage" and "DC connector" do I need? My ebike has a computer power plug coming out of the controller which I assume should plug into the battery.

The Charging voltage should match the Fully-Charged Voltage of the battery. If you are using Li-Ion or LiPo, that would generally be either 4.2V per Cell for modern cells. If the battery is a 10S (10 Cells) then the charging voltage should be 42V - Slightly lower voltage is OK (Some would argue even better), but higher voltage will damage the battery, and may cause a fire. - Since the Battery you linked to above is LiFePO4, the chemistry and per-cell voltages are different. In that battery you have 13 Cells and the charge voltage is listed at 43.8V

For DC connectors, there are many different styles - It shoud match your battery. If it doesn't you'll have to buy a matched set of connectors and solder them on to the charger and battery. Not a huge deal, really.

Thanks

 

[thatguy]

The Battery is the heart of the ebike. Further, a GOOD battery can move from your "starter" ebike to your "advanced" ebike, if you choose wisely. - A poor battery choice will leave you disappointed in the entire technology, and you may inappropriately decide that ebikes are not worthwhile.

I understand that there's a lot that I don't understand, and from this perspective, I assume these Headway cells are reasonable for a first ebike. One other thought is if I intend to have a second ebike (I'm interested in the Bafang bbs02 48V 750W motor), is it beneficial to get a 48v battery pack now and change out the 36V controller so I can share one battery for two ebikes (ie better to have both ebikes at same voltage)?

The Charging voltage should match the Fully-Charged Voltage of the battery. If you are using Li-Ion or LiPo, that would generally be either 4.2V per Cell for modern cells. If the battery is a 10S (10 Cells) then the charging voltage should be 42V - Slightly lower voltage is OK (Some would argue even better), but higher voltage will damage the battery, and may cause a fire. - Since the Battery you linked to above is LiFePO4, the chemistry and per-cell voltages are different. In that battery you have 13 Cells and the charge voltage is listed at 43.8V

Thanks for clearing this part up!

For DC connectors, there are many different styles - It should match your battery. If it doesn't you'll have to buy a matched set of connectors and solder them on to the charger and battery. Not a huge deal, really.

http://www.greenbikekit.com/lithium-battery/lifepo4/36v-15ah-headway-40152-battery-pack.html
What I have on the ebike is identical to a computer power cord (female). Is there an official name for this plug? There is no mention of any wires and connectors for this pack and the picture shows none either. Since this pack is 12S, can I assume I can simply solder on two wires on the two end cells leading to a male plug (ie like that of a computer power supply)?

 

[thatguy]

http://en.wikipedia.org/wiki/IEC_60320

Computer power cord official name is IEC 60320 C13 and C14. Interestingly, it's 10A rated. If my controller is 22 to 25A, is this a big problem I need to worry about?

 

[dogman dan]

Most of us here would say yes. You can cut off that plug, and substitute one that is better. Anderson power poles, or 4 mm RC bullets are two popular connectors.

 

[dnmun]

Ok, I think I get it, thanks for all input. Considering I paid $100 for the ebike, I'm not looking to spend $800+ on a battery.

http://www.greenbikekit.com/lithium-battery/lifepo4/36v-15ah-headway-40152-battery-pack.html
So, for this pack, you select the proper BMS to control the battery discharge based on your rated controller. I assume they put it all together for me, but I'll contact the reseller to ensure this is the case. As far as an outer protective case goes, where do I get one if it doesn't come with it? Do you need a case with a built-in fan for this type of battery?

http://www.greenbikekit.com/battery-charger.html
When I look at the battery chargers, they are rated by watts. How do I calculate how long a 240w charger will take to charge the above 36v-15ah-headway battery pack?

http://www.greenbikekit.com/battery-charger/240w-lithium-ion-battery-charger.html
Lastly, based on the required fields to purchase this charger, what "charging voltage" and "DC connector" do I need? My ebike has a computer power plug coming out of the controller which I assume should plug into the battery. It's probably non-standard so I assume I can order whatever the default DC connector is, then cut off the power cord plug and reattach??

Thanks

the battery is the heart of these machines. so why would it not cost more than the little hub motor? you need to use real conductors and not use lamp cord for the current path from the battery to the mosfets in the controller. the circuit side of the controller is ok for the little wire. here is a cheap battery:

http://www.ebay.com/itm/181148272576?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT