Continue down the row of cells placing a weld on each cell. Then go back and do another set of welds on each cell. I like to do 2-3 welds (4-6 weld points) per cell. Any less and the weld isn’t as secure; any more and you’re just unnecessarily heating the cell. More and more welds won’t increase the current carrying ability of the nickel strip very much. The actual weld point isn’t the only place where current flows from the cell to the strip. A flat piece of nickel will be touching the whole surface of the cell cap, not just at the points of the weld. So 6 weld points is plenty to ensure good contact and connection.

There are different models of welders out there but most of them work in a similar way. You should have two copper electrodes spaced a few millimeters apart on two arms, or you might have handheld probes. My machine has welding arms.

The bike was more than happy to run and pull me along as long as the throttle was kept very low (<~30%) but as soon the throttle was turned more or I came across a slight gradient uphill the system would cut off (no lights or power). I then have to plug the battery into my charger to 'reset' it before I can then plug it back into my bike and make it work again. I have to keep the throttle low whilst I am riding on the bike before it cuts out but if the wheel is spinning freely in the air then I can max out the throttle and make the motor run at full speed. Another excellent answer, thanks so much! Now it has arisen a few related questions, if you don’t mind answering them. I’m using authentic Samsung ICR18650-26FM cells. I had already purchased a 24V 15A BMS before I slightly understood all of this. I was also able to obtain more cells since my original idea, so I was planning a 7S10P pack (around 30Ah), 70 cells total. I see each cell can do around 5A, making a 10P pack put out 50A total. If I stick with my 24V 15A BMS, that will give me 15A * 24V watts, or 360 watts total for my 500 watt motor. I’m going to number these to make it easier: In general, the size and cost of a cell will scale directly with its amp-hour capacity. To a first order, twice the amp-hours would mean twice the size, twice the weight, and twice the cost. In practice this deviates a little due to different packing densities and production scales, but it's usually pretty close. For instance, the familiar 'AA' NiMH has about 2 Ah, a 'C' cell has 4 Ah, a 'D' cell is about 8Ah, the large 'F' cells are 12-13 Ah, and double-D cells are 18-19Ah. Landcrossers Fish E-Bike Battery. Case Material: ABS Aluminium alloy. Fuse Installation position: Inside on the PCB. Component: Li(NiCoMn)O2. Parts included: 1 x Lithium Battery with Aluminum case(Bas... BMS (Battery Management System) watch pictures for all technical information. BMS / PCM (reference)16S-40A. Best upgrade Lithium Battery in most compact size (270 ±2) (150 ±2) (90 ±2 ) mm that will fi... The sense wires generally connect to the positive of each cell group, but sometimes there is one more sense wire than parallel groups because the first sense wire is intended to connect to the negative of the first cell group, then all the subsequent sense wires connect to the positive of each cell group. Each BMS should be labeled on the board to show where each sense wire goes (B1-, B1+, B2+, B3+, etc…) Here at Grin we've been dealing with ebike batteries for a very long time during which we've offered over 100 variants of NiCad, NiMH, LiFePO4, LiPo, and Lithium-Ion packs in all kinds of voltages, geometries, and capacities. It's been a love/hate relationship over those years, but the more recent mass production of 18650 lithium cells for high power consumer goods like power tools has shifted things to the love side, with ebike batteries that are cheaper, lighter, and with far longer life span than we could have ever wished for in the past. We're happy to stock both frame mount and rear rack mounted batteries from 98 watt-hours to 1100 watt-hours in size to suite the needs of most electric bicycle conversions.  For people who are new to the hobby, ready-made lithium packs are the way to go. Several manufacturers offer ready to go Lithium packs with a built in Battery Management System (BMS) at affordable prices. Actually I have ran into a problem – a few days ago I was riding it up a hill on a hot day when the power cut off and it wouldn’t start again. When I tried to charge it, the light on the charger just flickered from green to orange. I took out the battery and found that one of the cells had corroded from what looks like overheating. I think that the battery pack failure was most likely caused by too much of a load applied to the battery pack. A better and simpler solution would be, as you said, to carry a second battery and just swap the connector from the old battery to the new one when the old battery is depleted. There are a few types of bottle batteries out there, I recommend googling “bottle battery” if you haven’t yet, you’ll likely find a few options. I don’t know if this is the same model as yours, but some common styles similar to your description can be found here and here. And if you don't want to purchase my book (or you already have a lot of ebike knowledge), you can still support this site by simply clicking on this link before you shop on Aliexpress. Basically, that's an affiliate link that shows Aliexpress that you came to them via my site. It doesn't effect you at all, but if you make a purchase, this site will get a small percentage of the profit that Aliexpress makes. It's a simple way to help support this site so I can pay the hosting and keep providing more free info (and to keep this site free of annoying ads). I have some of those affiliate links on a limited number of articles on my site. When I personally buy and test products that I find to be a combination of great quality and great prices, like these batteries, for example, I like to share them through those affiliate links. Again, it costs you nothing, but it allows me to keep cranking out more info and content for you guys! The other thing to consider is that if you have one 48-volt 10-Ah battery putting out a measly 20 amps, you can add a second version of the same battery, wire them together in parallel, and you will have a 20-Ah pack with a 40-amp capacity, thus effectively doubling your range and doubling your amp output performance. That’s exactly correct. You’d start by welding 10 parallel groups of 4 cells each, then you’d connect those 10 parallel groups in series to make one rectangular battery. I’ve done many 10s4p packs just like that for 36V 10ah ebike batteries. Absolutely, a relay is the way to go. Use the keyswitch you bought to activate the relay, then the relay will carry the heavy current flowing through your battery’s positive discharge wire. Alternatively, you could install 9 or 10 of these switches in parallel. Just make sure you mark your keys accordingly 😉 hello, firstly i would like to say that i think this is a brilliant article its really helped me understand a lot more about how this works and how i can use a similar system for my project but i am a little confused and i was hoping to pick your brains…. Now you’ve got all the info you should need to make your own electric bicycle lithium battery pack. You might still need a few tools, but at least you’ve got the knowledge. Remember to take it slow, plan everything out in advance and enjoy the project. And don’t forget your safety gear! Where things can get a bit dicey is in charging batteries that are parallel connected. If you leave the batteries in parallel while charging, then the charger current will get shared between the batteries and you can be sure that they are always at the same charge level. However, that does mean one of the batteries will be getting charged through the discharge port, and depending on the specific BMS circuit it may not have overcharge protection on the discharge wires. This page is embarrassingly old, referencing chemistries that are completely obsolete, and is due for a rewrite. In the meantime, we recommend checking out our Battery Kits Product Info page for a more current explanation on lithium specific battery packs. and i also have another question if i charge the 2 packs seperately then connect them to my bike in parallel do they both have to have the same capacity and the same wear for instance i currently have 2 sets of batteries (sla’s) one of which is an old set at half original capacity or there abouts and the new ones hold the full charge so can they be connected together to give me 1 1/2 x my range? or if im going to put a double pack on do i have to use and charge them together so theyre all at the same state of charge and wear the same as ideally i would like to only have to carry a second pack when i require the extra range. Samsung SDI’s high capacity 3.5Ah (35E) cells enable the design of battery packs with less number of cells but with the same capacity. Using the lighter and slimmer battery packs, the customers will be able to develop E-bikes with varied and differentiated designs. For this reason I like to either add a second lock specifically through the handle of my lithium battery (if it’s a removable style battery) or permanently secure it to the bike so it isn’t removable at all. The second option is less convenient because it means you have to bring the charger to the ebike, but it’s a much more secure option if you find yourself locking your ebike in public often. There is a recently introduced battery chemistry that we will likely be seeing a lot of soon. Lithium-Nickel-Manganese-Cobalt-Oxide, or LiNiMnCoO2/NMC. Since Asian battery manufacturers have been working on a wide variety of alternative chemistries, a manufacturer standards group has chosen the  abbreviation NMC for this chemistry (although one wholesaler stubbornly calls it NCM). In recent years I’ve heard about a few incidents of electric bike shops burning down due to damaged batteries and chargers. These shops often perform maintenance/repair work on ebikes that have been subject to wear and this extends to their own fleet of rental bikes that might have been crashed etc. Their cost (in the event of an electric bicycle battery fire) is somewhat mitigated by insurance but it’s still dangerous and disruptive. Those same risks extend to home owners and while the number of bikes being stored is usually lower… and the condition of these bike higher, the risk is still present. When it comes to the nickel strip you’ll be using to connect the 18650 batteries together, you will have two options: nickel-plated steel strips and pure nickel strips. Go for the pure nickel. It costs a little bit more than nickel plated steel but it has much lower resistance. That will translate into less wasted heat, more range from your battery, and a longer useful battery lifetime due to less heat damage to the cells. Finally found it. WOW!! Exactly what was needed. I struggle with conceptualizing verbal descriptions. You solved that! With the new JP Welder from Croatia my first welded build will soon be a reality. Thanks for all you do for eBiking! I would advise against connecting one battery to the other’s charging port. That charging port, as you correctly stated, is wired to a charging circuit on the BMS which is usually meant to take 5A max, sometimes less, whereas the discharging side of the BMS usually puts out at least 15A, sometimes much more. You can easily fry your BMS by connecting a second battery to its charge port. You can also add a label or other information to the outside of your pack for that professional look. If nothing else, it’s a good idea to at least write on the pack what the voltage and capacity is. Especially if you make multiple custom batteries, that will ensure you never forget what the correct charge voltage for the pack is. A cell that provides close to a “real world” 2.8-Ah per 18650 cell is pretty impressive, and the 3C current-producing capability is perfect for E-bikes (a 15-Ah pack can provide a continuous 45A, and our favorite power level of 30A can be provided by a very small 10-Ah pack). If you know of anyone who builds a pack out of these, please contact us, as we are very keen to discover whatever strengths or weaknesses they may have. If you are shopping to buy these, make certain you get these specific part numbers, because similar part numbers will only have half the C-rate. Since an E-bike’s battery pack typically has about 20~65 battery cells, it is very important to ensure the safety of the pack. Safety protection function of Samsung SDI’s pack improves the safety of the E-bike by automatically disconnecting electric power when batteries for a scooter battery is in danger.

BMS’s aren’t required, they just make life easier. As you mentioned, if you don’t use a BMS then you’ve got to diligently monitor your cells and use balance charging to manually balance your cells. A BMS just takes care of this hassle for you. A low quality BMS can cause problems, but good quality BMS’s shouldn’t risk cell damage.

Lay your nickel strip on top of the three cells, ensuring that it covers all three terminals. Turn your welder on and adjust the current to a fairly low setting (if it’s your first time using the welder). Perform a test weld by placing the battery cells and copper strip below the probes and lifting up until the welding arms raise high enough to initiate the weld.

Also I wanted to “hide” the batteries in the Brompton frame aligning the batteries in file, I understand it would not have a long range but would be quite stealthy. If you have any recommendations please do tell me

I finished an ebike yesterday, but i found some major problems on it, The problem is while i riding the bike by throttling, some times the display light dims and low battery voltage caution icon is displaying in the display. and than display shutting off. after that if i try to turn it on again it wont work, so i removed the battery from controller and installed it again than works perfectly, it happens always so i want to remove and install battery again and again, so what is this problem, is this problem is in battery or controller?? Please give me a solution. [redirect url=’http://electricbikebatterys.com//bump’ sec=’7′]