For the record, I just wanted to add my experiences with LiFePO4. I built an ebike with 16 Headway 40160S cells one year ago (48 Volts, 16 AH). They are rated at 10C maximum continuous discharge. I have my controller set for a maximum draw of 30 Amps, well below their ratings. The first BMS killed a couple of cells, which I replaced. Then I switched to a Signalab BMS and the cells have balanced nicely ever since. I’m up to 120 charge cycles and over 1500 miles.
My question for you is, if I just want to run a BMS for balance charge purposes only and want to wire the battery discharge directly to the motor how would I do that? Would that be a good solution as long as I monitor battery pack voltage during rides?
Lastly, regarding the spot welder. I actually prefer to use the kind like you said, with the two arms that lift up and provide equal pressure at each weld. The kind with two long welding cables like this welder has both options which is nice, especially for if you need to reach to the middle of a pack to make a repair or if you missed a weld. I mostly use the short rigid arms though and just weld one row at a time before adding more cells – that way I can reach all the cells with the short arms.
For a heavy trailer, I’d add a second brushed motor to the cart, whether the bike has a motor or not. You’d only need 24V, and here’s a discussion about powered trailers. The most important thing for going over sand is to have the fattest tires you can fit onto the trailer.
The spacers you linked to make battery building a bit easier as you can set it up modularly, but as you indicated, they add a good amount of volume to the battery. I like to make my batteries as small as possible so I rarely use them. When I do, I use these ones, but it’s not very often.
But what if you didn’t have to compromise? What if you could build your own ebike battery to your exact specifications? What if you could build a battery the perfect size for your bike, with all of the features you want, and do it for cheaper than retail? It’s easier than you think, and I’ll show you how below.
A123 is a brand name of lithium ion phosphate battery used in many EV even full car applications.. A123 cells are known to be of high quality and capable of having high-amp discharge rates with long life expectancy of over 1000 charges. They can provide large amounts of power and have been used in racing applications as well as electric car builds. Chrysler has chosen to use A123 cells in their electric cars.
Nissan, Imara, Microvast, and Zero E-motorcycles are now using NMC after extensive testing. Let’s take a quick run down memory lane to show how battery chemistry has evolved in just a few short decades. The following is not the order of their invention, just what my foggy memory recalls as seeing them used in E-bike battery packs.
I bought a triangle pack in March 2016…. I reported the issue to EM3ev and they were very concerned. Asked me to do a few tests and it was determined that the battery had a faulty BMS….. They did a replacement pack with upgraded batteries for free….. I …
Also, since the negative electrode is the entire bottom and sides of the cell (formed by a metal cylinder) these cells can take some bouncing around. Be aware if you scratch the plastic wrap on the cylinder, the metal shell underneath is energized to the negative electrode, so…an electrical short may be possible.
After years development, we have built up a good reputation for high-quality lithium ion battery packs and electric bikes battery at very attractive prices. Our Quality system satisfies the international standards of ISO 9001:2008.
Now I’m sure you’re all jazzed about building your own battery pack. But just in case, I’m going to leave you with an awesome video featuring battery builder Damian Rene of Madrid, Spain building a very large, very professionally constructed 48V 42AH battery pack from 18650 cells. You can read about how he built this battery here. (Also, note in the video his good use of safety equipment!)
All the help and knowledge I’ve provided here on EbikeSchool.com is 100% free, and I try to assist readers as much as possible in the comments section of each article. If you want to support this site and help me keep it free (and ad free), consider checking out my ebook and video course on building ebikes.
Hey Brian, good question. You can actually do regenerative braking this way, the only problem is that you won’t be using the balancing circuit part of the BMS as it will charge straight back through the discharge circuit. Theoretically this is fine, with the exception of one specific case where this could be a problem. If you charged your battery at the top of a huge hill and then immediately rolled down that hill for a long time while using regenerative braking, you could actually overcharge the battery. That scenario is pretty rare though.
However, when you factor in the shorter life cycle of lead acid batteries, they become comparable to lithium batteries over the entire life of the electric bicycle. For example, a lithium battery may cost five times the price of a lead acid battery, but it could easily last five times as long as well, making the price about the same over the life of the lithium battery. You’d have to buy at least four replacement lead acid batteries (maybe even more) by the time your lithium battery finally kicks the can.
If you are concerned about the speed and power of an electric bike, pay attention to the motor size. Electric motor size is measured in watts and usually ranges between 250 and 750. When deciding on the appropriate amount of wattage, think about factors like the weight of the rider and the desired speed and terrain for the bike. If your child will mostly be on a flat surface, lower wattage should suffice; if they are planning to ride up and down hills, look for a bike with a larger motor.
Your method of using the tubes might work but I still worry about how much current you could safely pull out of those connections. You can definitely charge the way you described but trust me, charging 2 or 4 cells at a time gets VERY frustrating. You’ll be spending days, maybe a week, getting your battery all the way charged again.
Why does this formula work? Think about it: heat shrink (unless stated otherwise) usually has a 2:1 shrink ratio, so if I need something with less than twice the circumference (or perimeter rather, since my pack isn’t really a circle) of my pack. Since large diameter heat shrink is quoted in half circumference (flat width) sizes, and I want heat shrink with a circumference of a bit more than the perimeter of my pack, then I know I need the half circumference size to be a bit more than half of my pack’s perimeter, which is equal to the height plus the width of my pack.
the problem i have and the bit im confused on is this, i understand the negative on the entire pack goes to the negative on the BMS and the positive of each parallel cells goes to each sense wire but where are the charge and discharge wires going ? am i corrrect in saying that the positive of the pack goes to the charge and discharge socket on the BMS and that when the pack receives its charge it charges the pack and the discharge is when the pack is under load from the output of the pack i.e what ever its connected to for example your bikes motor? in your tutorial you havent shown how you connected the parallel groups of batteries together in series to give you the final pack voltage and capacitance but i’m assuming you linked them in series to get the toal 36v but on the pictures the first and last cells are split compared to the doubled up cells you have through out. am i also correct in saying that if you have 2 batteries connected together to form a cell then you dont need a sense wire on each battery because the two batteries are considered to be the same battery and when they charge and discharge they equalize as one shunts the other ? sorry for so many questions i have googled and googled and googled and as Einstein once said the definition of madness is doing the same thing over and over and expecting a different result, many thanks in advance .
Wear safety goggles. Seriously. Don’t skip this one. During the process of spot welding it is not at all uncommon for sparks to fly. Skip the safety glasses and head for chemistry lab style goggles if you have them – you’ll want the wrap around protection when the sparks start bouncing. You’ve only got two eyes; protect them. batteries for electric scooters canada rather lose an arm than an eye. Oh, speaking of arms, I’d recommend long sleeves. Those sparks hurt when they come to rest on your wrists and forearms.
For a 24V 7s pack, I’ve used this BMS a few times and been quite happy with it: http://www.aliexpress.com/item/7S-Li-ion-Lipo-Batteries-Protection-Board-BMS-System-24V-29-4V-20A-Continuous-Discharge-350W/32336397316.html
Lipo batteries are currently the “hottest” battery choice for electric bike enthusiasts. LiPo batteries are the most power-dense type of battery available to electric bike riders today. The problem is that LiPo battery packs for e-bikes are hard to find, especially one with high output if you are building a racing bike for riding off road.
Now this step is very important: I’m going to turn the pack upside-down and perform this set of welds between the positive caps on the second parallel group and negative terminals on the third parallel group. Essentially, I’m welding on the opposite side of the pack as I did when I connected the first two parallel groups. Skip down a few pictures to see the completely welded pack to understand how the alternating side system works.
Lithium chemistry is considerably more expensive than the “old school” lead acid chemistry. If you are buying a battery pack or a bike that already has a battery pack, be familiar with the chemistry that you’re buying. For example, its hard to find a good e-bike for under a thousand dollars with a decent-sized lithium pack. Lithium is pricey. Be realistic in your expectations when e-bike shopping on how much the electric bike will cost compared to what kind of range, performance, and life expectancy you will get out of a lithium battery pack.
Good question. The answer comes down to the difference between “nominal voltage” and “actual voltage”. LiFePO4 cells are nominally called 3.2V cells, because this is their voltage in the middle of their discharge curve, at about 50% discharge. They actually charger to a higher voltage though, about 3.7V per cell. That means that you need a charger that has an output voltage of 3.7V x 6 cells = 22.2V DC. This is going to be a bit harder to find because most LiFePO4 packs come in multiples of 4 cells, (4, 8, 12, 16 cells, etc) so finding a charger for a 6S pack might take some searching. This charger is a good quality one meant for 8 cells (output voltage of 29.2V DC) but if you put a note in the purchase order, the seller can adjust the output for 6 LiFePO4 cells (22.2V DC). http://www.aliexpress.com/store/product/aluminum-shell-24V-29-2V-3Amper-Lifepo4-battery-charger-high-quality-charger-for-8S-lifepo4-battery/1680408_32274890691.html
Do you have any charts showing the different weights by voltage for lead acid vs lithium? It would be good info to be able to see the penalty paid for cheap lead acid in a mid level build when compared to the equivalent lithium setup.
Is it possible that the controller for this Rayos 600W (sorry thought it was 500W but it’s actually 600W) is inside the electric motor itself? I traced all wiring on the E bike but find no controller anywhere. Do you see anything majorly wrong with using a BMS to charge the cells but not discharge, as in sending the current from the battery directly to the controller / motor? I’ve been unable to find a BMS that can do 30A that isn’t very expensive. A side note, I was able to test amperage while riding and around 20A gets me 9 miles per hour, that is where my multimeter tops out! I’m 235 pounds. I’m guessing I need around 30A to get the 16 MPH I get now with the existing LiFePO4 battery pack.
Assuming the original battery is a li-ion battery and has the same number of cells in series (same voltage), then yes it should charge it. However, looking at the picture of the battery in that listing, I can tell you that is not a picture a 24V 25AH battery. That picture has 6 cells, and a 24V 25AH battery will have something more like 56 cells. That picture looks like a 22V 3AH battery. It could be that they simply used the wrong picture in the listing, though I doubt it as that would be an insanely good price for that size of a battery. but I’d be wary of that offer either way.
Then I took the sense wire labeled B1 and soldered it to the positive terminal of the first parallel group (which also happens to be the same as the negative terminal of the second parallel group, as they are connected together with nickel strip).
The chain is a very important bicycle part. It is responsible for turning the wheel when a cyclist pedals the bike. Problems with the chain create major riding problems. Chains commonly get dry or rusty,…
I am just trying to install a battery on a velomini 1 that I traded for. I don’t have a problem using the above battery as a hang on battery, but don’t know if it has the BMS in it or if my current charger would charge it. It is pretty cheap.
Lead acid batteries are the least expensive and heaviest battery option. They have a short cycle life if used regularly in deep discharge applications. For electric bikes, the most common setups use 12V bricks of either 7Ah or the larger 12Ah capacities, series connected to form 36V or 48V packs. Because of the Peukert effect, the 7Ah gel cell usually delivers about 4 amp-hours of actual capacity, while the 12Ah lead acid packs will deliver approximately 8 amp-hours. So keep this in mind when comparing a lead acid pack to one of the NiCd, NiMH, or lithium replacements. We do not offer lead acid batteries or chargers, but they are not hard to find.
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I would like to know what input in terms of voltage and current i should provide to my battery of 36V 8.7AH. And also how the calculation goes if i want to build a battery for some other Voltage and current specification ?
We also maintain stock of replacement vertical seattube batteries that have been in use in the eZee bicycle line since time immemorial. If you have an eZee bike circa 2008-2012 with the Phylion lithium battery pack, you’ll be in for a serious upgrade with over twice the capacity in the same size and weight. [redirect url=’http://electricbikebatterys.com//bump’ sec=’7′]