Intro battery pack

Hello, I am looking to build an e-bike to get me to and from class (2 miles, some somewhat serious hills). I have the controller/motor setup planned, but want some opinions on battery choice.
I have been reading a lot, and am a little nervous about LiPo chemistry, as I have no experience with it. LiFePo4 seems like a more beginner friendly composition, but most people are using LiPo, so I am unsure what cells would be good. I came across Headway batteries, and these seem like a good option, as they could be easily expanded on to increase voltage/capacity if I desire. I have searched the forums but haven't found many recent mentions of these cells. Are they still a good option? I also had a hard time finding suppliers. Any reccomendations?
My current goal is a pack between 5-10Ah at 36v with a continuous 30a discharge. Admittedly, this is probably a bit overkill, but sounds like fun.

Thanks!

Keep in mind that a 10Ah pack run at 3C is only going to last 20 minutes at that rate. But that *should* be long enough, at 15-20MPH, to cover a round trip of 4-5 miles, easily enough.


If you need 30A continous, Headway may not be a good option. They claim high C rates, but may heat up too much running continously at that, depending on how long you have to run them at that.

RC LiPo can easily do it, but they can be dangerous; if you are not familiar with them already, I don't recommend them until you read the various "LiPo care" and "lipo noob" type threads, so you know what you're dealing with, and are sure you can care for them properly. When they work they work great, but when they fail dramatically, it can have horrible results. (so can any other chemistry...but it happens more often with RC LiPo for various reasons).

Some of the 18650-type packs can handle 3C+ continuous, not sure about 6C, but the harder you push a battery, the less time it will last, and the hotter it will get. So if you get ones with quality brand name cells in them of the right model, a 10Ah pack could do 30A continuous. There are a lot of threads about various 18650 models, that will tell you what they are capable of, including some actual testing threads. Beware that when buying premade packs from ebay, alibaba, etc., the specs may or may not have anything to do with reality, and may or may not actually contain the cell brand/model they say they do. No way to tell until you get it and test it yourself, unless someone else has already done that.

In my experience the cheap LiFePO4 packs of any kind aren't going to do more than 1C continuous in reality, no matter what their specs say. So you'd need *at least* a 30Ah pack to do 30A with those. Ones made from A123 cells could do it, either prismatic or cylindrical, and there are probably other LiFePO4 cells that could do it, but not the typical cheapie cells. Some fo them could do short bursts of 2C, maybe 3C when closer to full than empty, but I wouldn't do it continuously.


There are some "reliable battery sellers / vendors" threads, some recent, that may have some useful info.


If you don't mind DIY packs, you can build a reliable pack that can do what you want, but may be larger than you're after, using recycled automotive EV cells, like those from the Leaf, etc. More info on those cells is in a thread for "Salvaged EV cells", IIRC.

Hmmmm... I see, the problem with adding more capacity is my costs will dramatically increase. I suppose I will do more research on LiPo.. Realistically, I doubt that I will use 30A for more than a couple minutes at a time, although this would be my first e-bike, so I am unsure what typical loads look like in real life. Would that time frame cause them to heat to a level where damage will start occurring?
I have seen the salvaged ev thread, but I think the leaf batteries will be too large and expensive for my needs.

Ongar said:

Hello, I am looking to build an e-bike to get me to and from class (2 miles, some somewhat serious hills). I have the controller/motor setup planned, but want some opinions on battery choice.
I have been reading a lot, and am a little nervous about LiPo chemistry, as I have no experience with it. LiFePo4 seems like a more beginner friendly composition, but most people are using LiPo, so I am unsure what cells would be good. I came across Headway batteries, and these seem like a good option, as they could be easily expanded on to increase voltage/capacity if I desire. I have searched the forums but haven't found many recent mentions of these cells. Are they still a good option? I also had a hard time finding suppliers. Any reccomendations?
My current goal is a pack between 5-10Ah at 36v with a continuous 30a discharge. Admittedly, this is probably a bit overkill, but sounds like fun.

Thanks!

Click to expand...

What you are not looking at comparing LiFePo4 and LiPoly are the relative weights for a given capacity. The LiFePo4 is the heaviest, while LiPoly is by far the lightest. Headways and LiFePo4 still have some endearing traits, but unless you are carrying them in a cart, I would go with Li-ion or LiPoly. Even 20Ah of the much lighter LiPoly starts to feel heavy for my pedal assist ebikes. I have been using Lipoly about 7 years and it was a learning process replete w/ charred fingers, but no fires(unintenionly I have refined the process to a point it is perfectly safe and easy, but it still requires more attention(time) than a "plug and play" chem. This is because it should be stored at a mid to mid/high state and only top charged when heading out.
LiPoly is still the best Value, but not as much as Hobbyking doesn't have it on sale much these days.
It is still the lightest
It is still the most modular allowing one to "build a pack" for the distance anticipated.
It is still the most linear in it's discharge rate, allowing a simple Voltmeter to be a pretty good "fuel gauge".
Here's a post I made the other night(which the OP never responded to);
<<<<Unfortunely, Hobbyking hasn 't been keeping lot's of LiPoly on sale like they used to, but some does go on sale now and then. You need to get on their alerts and watch(When broswering HK's awful website go straight to the last 3 battery pages). Look for the biggest bricks that will fit the space(for a reason I'll go into in a moment). The Multistar offers big bricks, 10Ah up to 20Ah, but I'm not sure they could handle the high discharge rates you mention. Maybe the new 12C stuff. I used to get the MS 6S, 10Ah bricks for $50 (free shipping) and make 12S, 20Ah packs for $200!
In the same vein, doing 12S (6S + 6S, or 4S + 4S + 4S) gives more and less expensive buying options. I run some 14S packs using the Zippy Compact 7S, 5.2Ah that were on sale for $50 ea. and 4 make a nice 14S, 10.4Ah pack.
Really, those bikes and your new packs deserve a serious charging system. Get a Mean Well HLG-320-54A, a really solid, potted CC/CV charger(it's really a power supply) that has an adjustable top charge Voltage. If you don't know, LiPoly should be stored @ 3.90V or below and only top charged before use. Not doing this will shorten the service life of the batt.s. Buy one Battery Medic per brick, that why going w/ the biggest bricks possible is way to go. For example, a 2S/2P pack would be only 4 bricks and only 4 BM's would be needed.
Using this adj. power supply and the BM's take care of the HVC and balancing, so if your LV alarm is reliable, you could lose the, often troubesome, BMS.
If you are interested in going this route, I could provide the link to the BM's and provide more details how I do it.>>>
Lastly, I would say, with Ebikes in general, but especially LiPoly, there never is any reason to run a 36 V system when a 48V one can be used. Well, maybe if the bike was purposed to be used on a boardwalk or ped path only, but in general, more performance(not just speed)can be had for no addtional money or complication w/ a 48V system . For LiPoly specifically, it is always best to have the controller provide the LVC (Low Voltage Cutoff) and 12S of LiPoly matches the common 41 or 42V LVC of a 48V controller better than 10S of LiPoly matches the LVC of a 36V controller. In fact, I have used 9S which was closer to the LVC of 31 V than 10S, but 9S w a low or mid speed range motor makes for a pretty slow ebike(16 to 18 mph)..

Ongar said:

Hmmmm... I see, the problem with adding more capacity is my costs will dramatically increase. I suppose I will do more research on LiPo.. Realistically, I doubt that I will use 30A for more than a couple minutes at a time, although this would be my first e-bike, so I am unsure what typical loads look like in real life. Would that time frame cause them to heat to a level where damage will start occurring?
I have seen the salvaged ev thread, but I think the leaf batteries will be too large and expensive for my needs.

Click to expand...

Electric motors are not at all like gas engines where you just hold on the throttle and the Horse-power builds as the revs climb. In fact, one needs to discard what one knows about IC engines and start w/ a blank sheet. One great learning tool(the whole site really)is the simulator @ Ebike CA (Grin). Build a system on the sim that you are interested in and start changing variables to see what does what.
Hills are everything w/ Ebikes. Anybody can build an ebike to cruise around in Flatland, almost anything will work ok, but it's the hills that present the challenges.
Basicly, it boils down to selecting the motor speed range and Voltage that matches whl. size and desired(that is attainable) road speed and retain some climbing ability. Hub motor systems especially will always be a compromise. The lower the power(the smaller the motor), means more compromise.

What you are not looking at comparing LiFePo4 and LiPoly are the relative weights for a given capacity. The LiFePo4 is the heaviest, while LiPoly is by far the lightest. Headways and LiFePo4 still have some endearing traits, but unless you are carrying them in a cart, I would go with Li-ion or LiPoly. Even 20Ah of the much lighter LiPoly starts to feel heavy for my pedal assist ebikes. I have been using Lipoly about 7 years and it was a learning process replete w/ charred fingers, but no fires(unintenionly I have refined the process to a point it is perfectly safe and easy, but it still requires more attention(time) than a "plug and play" chem. This is because it should be stored at a mid to mid/high state and only top charged when heading out.
LiPoly is still the best Value, but not as much as Hobbyking doesn't have it on sale much these days.
It is still the lightest
It is still the most modular allowing one to "build a pack" for the distance anticipated.
It is still the most linear in it's discharge rate, allowing a simple Voltmeter to be a pretty good "fuel gauge".
Here's a post I made the other night(which the OP never responded to);
<<<<Unfortunely, Hobbyking hasn 't been keeping lot's of LiPoly on sale like they used to, but some does go on sale now and then. You need to get on their alerts and watch(When broswering HK's awful website go straight to the last 3 battery pages). Look for the biggest bricks that will fit the space(for a reason I'll go into in a moment). The Multistar offers big bricks, 10Ah up to 20Ah, but I'm not sure they could handle the high discharge rates you mention. Maybe the new 12C stuff. I used to get the MS 6S, 10Ah bricks for $50 (free shipping) and make 12S, 20Ah packs for $200!
In the same vein, doing 12S (6S + 6S, or 4S + 4S + 4S) gives more and less expensive buying options. I run some 14S packs using the Zippy Compact 7S, 5.2Ah that were on sale for $50 ea. and 4 make a nice 14S, 10.4Ah pack.
Really, those bikes and your new packs deserve a serious charging system. Get a Mean Well HLG-320-54A, a really solid, potted CC/CV charger(it's really a power supply) that has an adjustable top charge Voltage. If you don't know, LiPoly should be stored @ 3.90V or below and only top charged before use. Not doing this will shorten the service life of the batt.s. Buy one Battery Medic per brick, that why going w/ the biggest bricks possible is way to go. For example, a 2S/2P pack would be only 4 bricks and only 4 BM's would be needed.
Using this adj. power supply and the BM's take care of the HVC and balancing, so if your LV alarm is reliable, you could lose the, often troubesome, BMS.
If you are interested in going this route, I could provide the link to the BM's and provide more details how I do it.>>>
Lastly, I would say, with Ebikes in general, but especially LiPoly, there never is any reason to run a 36 V system when a 48V one can be used. Well, maybe if the bike was purposed to be used on a boardwalk or ped path only, but in general, more performance(not just speed)can be had for no addtional money or complication. For LiPoly specifically, it is always best to have the controller provide the LVC (Low Voltage Cutoff) and 12S of LiPoly matches the common 41 or 42V LVC of a 48V controller better than 10S of LiPoly matches the LVC of a 36V controller. If fact, I have used 9S which was closer to the LVC of 31 V than 10S.

Click to expand...

Yes, weight was the other problem I thought I would run into, but I was not too concerned by it with a small Ah pack. I found your system interesting, I have not come across the battery medics before, and they look like a good cheap option. So if I understand correctly, you use the battery medics to balance the batteries before charging them with the Meanwell? Or do you have the Meanwell and battery medics connected simultaneously? If so I imagine that you would have to charge each pack one at a time, correct?
If you don't mind please explain your setup a bit more, it sounds like you have quite a bit of experience
I understand your reasoning for running 48v instead of 36, I was thinking that I could save some money here, but maybe not. I was considering using a vesc speed controller because it is programmable and I enjoy futzing around with settings, although the new version is quite expensive compared to ebay esc's with comparable specs.

motomech said:

Ongar said:

Hmmmm... I see, the problem with adding more capacity is my costs will dramatically increase. I suppose I will do more research on LiPo.. Realistically, I doubt that I will use 30A for more than a couple minutes at a time, although this would be my first e-bike, so I am unsure what typical loads look like in real life. Would that time frame cause them to heat to a level where damage will start occurring?
I have seen the salvaged ev thread, but I think the leaf batteries will be too large and expensive for my needs.

Click to expand...

Electric motors are not at all like gas engines where you just hold on the throttle and the Horse-power builds as the revs climb. In fact, one needs to discard what one knows about IC engines and start w/ a blank sheet. One great learning tool(the whole site really)is the simulator @ Ebike CA (Grin). Build a system on the sim that you are interested in and start changing variables to see what does what.
Hills are everything w/ Ebikes. Anybody can build an ebike to cruise around in Flatland, almost anything will work ok, but it's the hills that present the challenges.
Basicly, it boils down to selecting the motor speed range and Voltage that matches whl. size and desired(that is attainable) road speed and retain some climbing ability. Hub motor systems especially will always be a compromise. The lower the power(the smaller the motor), means more compromise.

Click to expand...

I am planning on implementing a mid-mounted motor so I can retain use of the rear cassette, so hopefully that will help with my motor's flexibility/hill climbing? Thank you for the link, I am playing with it now. I think this will definitely help me understand the power requirements for my use case.

Ongar said:

I understand your reasoning for running 48v instead of 36, I was thinking that I could save some money here, but maybe not.

Click to expand...

Note that as your voltage goes up, you're talking about less amps, your 30A discharge goes to less than 25A.

The story that came with my LiFePO4 battery is that the maximum continuous discharge is 50A, absolute limit is 100A. I rarely push it past 25A, and then for less than a minute.

There's no way on earth I'd consider LiPo.

I have not come across the battery medics before, and they look like a good cheap option. So if I understand correctly, you use the battery medics to balance the batteries before charging them with the Meanwell? Or do you have the Meanwell and battery medics connected simultaneously? If so I imagine that you would have to charge each pack one at a time, correct?

Click to expand...

You may be conflating "bricks" w/ packs.
Bricks are the single batt.s and my typical pack is comprised of 4 bricks configured 2S/2P(2 series/2 parallel). What we are talking about is bulk charging and as the name implies, I charge the whole thing, dis-connecting nothing. The pack can be 2S/3P or even 2S/4P, but that means more brick and more Battery Medics. That's why I like bricks of big capacity, in the 10AH to 20Ah range. Less wiring and neater too.The Mean Well HLG-320-54A will adjust to 57 Volts or so and will handle 14S. The HLG-320-48A goes to 54V and is perfect for 12S. I check balance at the end of storge charge(3.85V) and balance if necessary. They(the cells) don't usually stray on the top charge to 4.10V or so and if the start to, I just stop charging and go w/ what I have. If one obeys the 80% depth of discharge rule and don't continually dis-connect and connect the bricks, over time the cells seem to take a "set" and balancing becomes rare.
If you search my posts using search-words like; bulk charging. Mean Well or LiPoly, you will find lot's of posts, many w/ pics

I am planning on implementing a mid-mounted motor so I can retain use of the rear cassette, so hopefully that will help with my motor's flexibility/hill climbing? Thank you for the link, I am playing with it now. I think this will definitely help me understand the power requirements for my use case.

Click to expand...

Lot's of hub motors take a cassette, they are the ones w/ the suffix of C or CST. You need to review your needs and decide if your hills are so steep that you need to go w/ the added complication of a mid-motor. For speeds in the mid 20's mph and reasonable hills, a hub motor will be much less trouble. If you need a large performance envelope, then perhaps a mid-drive is the way to go

donn said:

Ongar said:

I understand your reasoning for running 48v instead of 36, I was thinking that I could save some money here, but maybe not.

Click to expand...

Note that as your voltage goes up, you're talking about less amps, your 30A discharge goes to less than 25A.

The story that came with my LiFePO4 battery is that the maximum continuous discharge is 50A, absolute limit is 100A. I rarely push it past 25A, and then for less than a minute.

There's no way on earth I'd consider LiPo.

Click to expand...

What does your LiFePO4 pack consist of?

Ongar said:

What does your LiFePO4 pack consist of?

Click to expand...

Beats me. 16 cells, they say.

Luna mighty mini any day over LiPo.

A mighty mini does look tempting, especially with the decrease in complexity and peace of mind compared to lipo.
Does anybody have opinions on This 7.8Ah 48v pack made from 20R cells? For the price of $200 it seems like a steal.
https://em3ev.com/shop/preditor-l-47v-8-4ah-11-8ah-frame-battery/

Casual riding with pedaling is 10-12wh/km
a mile is 1.6km
a wh is 36V x Ah

Ongar said:

A mighty mini does look tempting, especially with the decrease in complexity and peace of mind compared to lipo.
Does anybody have opinions on This 7.8Ah 48v pack made from 20R cells? For the price of $200 it seems like a steal.
https://em3ev.com/shop/preditor-l-47v-8-4ah-11-8ah-frame-battery/

Click to expand...

EM3EV have a 14S6P triangle battery on clearance at the moment.

52v 18.6Ah 40A pack made from Samsung 33G cells which are designed for long cycle life.

It's in the clarence section for $379.