I’m not familiar with this copper serial connection you’re talking about. I guess you mean to reinforce the series connections to handle more current? As long as you are using enough strips of nickel (and ensuring that it’s pure nickel and not nickel coated steel) then you shouldn’t need copper reinforcements. I try to use at least 1 strip of nickel for every 5A my battery will carry. So if I’m looking for a 20A max load, I’d use 4 strips of nickel in each series connection. That’s easy to do if each cell in a parallel group of 4 cells is connected to the next group by one strip each.
I’m mostly familiar with BesTech’s 72V BMS’s and haven’t used a 52V BMS from them, so I can’t give you a recommendation on a specific 52V (14s) BMS from them, sorry. I have used this 14s BMS twice and it’s worked great for me on two 14s7p packs I made with Samsung 26F http://huntnbike.com am new to the ofrum and to the ebike world so I would like to seek some advice please. I have recently bought a sondors fat bike to the UK and want to make some tweaks, I would like to upgrade the battery on a budget, I was thinking of 4 x 12v 5ah lead acid batteries in series, would this give me 48v 20ah or have I got this totally wrong? I want to replace the stock contoller for a 48v 25amp one, would this suffice? lastly it comes with a stock 350w bafang motor, if I make the battery and controller upgrades will the motor handle the increase in wattage? could I drill venting holes in the case cover to expell some heat? Your thoughts and advice would be most welcome,
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Now I’ve got all of my pack sealed in heat shrink with my wires exiting the seam between the two layers of shrink wrap. I could have stopped here, but I didn’t particularly like the way the shrink fell on the wire exit there, from a purely aesthetic standpoint. So I actually took a third piece of shrink wrap, the same size (285 mm) as that first piece and went around the long axis of the pack one more time to pull the wires down tight to the end of the pack.
LiMn was by far the most common chemistry in cheap (and expensive!) built up electric bikes for a long time. It’s a cheap, light, safe chemistry. The problem is low C, but much more importantly short life. And not just a short number of cycles but a short shelf life as well. Losing 20% capacity a year even if you don’t use the battery much leads to a lot of expense and warranty claims. LiNiCoMn has the same low cycle life, light and cheap characteristics, but it seems to have a longer shelf life and a slightly higher C.
Most lithium batteries that are designed to mount to ebikes also come with some form of locking system. These have varying degrees of effectiveness. The type with a little pin that slides into a thin sheet of steel are the easiest to steal by mangling the thin steel locking plate. Just take a look at your battery and ask yourself “how easily could I steal this battery if I had some basic hand tools and a 60 second window of opportunity?”
It’s best to try and match the cells as closely as possible based on capacity by using a lithium cell tester like this one. If you plan on using the battery you build for a high drain application, different current ratings will be more of an issue. If you have many cells in parallel and will only pull low current from each one, then different current ratings are less of an issue. It’s always best to use perfectly matched cells, though I know that’s not the cheapest option and is outside of the budget for many.
The lithium iron phosphate (LiFePO4) battery has had a lot of hype and media attention lately. This is the same chemistry used by A123 in the Dewalt power tool battery packs, where it has a 2000 charge and discharge cycle warrantee and has phenomenal current handling capability. The LiFePO4 batteries sold for ebike use generally have much lower current ratings, and the actual number of charge and discharge cycles that these generic packs will provide remains to be seen, although most manufacturers seem happy to claim 1500 to 2000 cycles. Iron Phosphate lithium packs are only slightly lighter than NiMH and a fair bit more expensive, but they could be the most economical in the long run.
At the same time though, think about if that is what you want. It could be that those cells died because of a malfunctioning BMS unit or old wiring. Putting new cells in their spots could just wind up killing those new cells in a few days or weeks. I’ve seen that happen as well. So make sure you check everything and consider all of your options!
Gotcha. Can you recommend a manufacturer that sells a two wire version? Maybe I can look around their products and see if they sell any 7S cells, rather than sifting through all the manufacturers on Alibaba. Searches for “2 wire MBS” didn’t yield much. Thanks again for your help with this!
your post have been extremely infomative, i am trying to DIY a pack for my electric scooter for a 36V and around 5AH pack should it be 10S 2P? sorry if i am not clear, kinda a beginner myself. and BMS wise what kind should i use?
One of the main disadvantages of lead acid batteries is their weight. There’s no beating around the bush here, SLAs are HEAVY, as you might guess by the inclusion of “lead” in the name. You’ll need a strong mounting solution on your ebike to handle the extra weight of SLAs. You should also be aware that lugging that extra weight around is going to negatively impact your range. The best way to improve the range of any electric vehicle is to reduce weight, and SLAs are kind of going the opposite way in that regard.
Introduce Yukon Trail 2018 new model Xpedition Features: 350w motor Battery: Samsung lithium battery (light weight 5 lbs with case) Speed/Mileage: up to 20MPH, up to 28 miles per full charge (varies b…
I placed the first parallel group positive side up, and the second parallel group negative side up. I laid the nickel strips on top of each of the three sets of cells, bridging the positive caps of the first parallel group with the negative terminal of the second parallel group, as shown in the picture.
My series connections are between each group of 3 parallel cells. So all the connections that go across the short side of the pack are parallel connections, and all the connections that run along the long end of the pack are series. It doesn’t always happen that way, but the shape of this pack forced that geometry.
Typically you can expect somewhere between 25 and 70 miles of travel on a single charge of an ebike. If you’re riding hard on full power expect less; manage your battery life well and you could get more.
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.
I was using that battery on an ebike with a 15A controller, so that BMS was capable of twice the power I need, meaning I would only be stressing it to 50% of it’s potential by pulling 15A. That’s why I said it’s more than I’ll need. But if I wanted to put it on a bike with a 45A controller, then it would NOT be enough, and I’d need a more powerful BMS.
This is a great article, I was thinking about making including the batteries and controller in the front Wheel/Motor hub ala (Copenhagen Wheel & FlyKly) and then create something like a solid acrylic or fiber wanted to cover the whole thing and rearrange the batteries.
However… I’m thinking about extending the range of my 250W ebike (a Greenedge CS2) by wiring a battery in parallel as a one-off project. My thinking is that as it would halve the load on each of the batteries, it would reduce output current and voltage drop under load. This I’m thinking would allow use of a simpler constructions, since the stress on each cell would be reduced.