If you can’t find the exact same battery to fit in that holder, you could aways open up the area where the controller is and lengthen the wires so they exit the case, then put your own connector there (rated for at least 20A). Then add that same connector to your second battery pack and you’ve got an easy plug and play setup for switching packs with the matching connector.

If not possible, try charging them individually. Some of them might come back but others might be dead. The tricky thing is that they will likely not be able to deliver their full capacity anymore and the actual capacity will likely vary from cell to cell. Two year old cells at a very low voltage are quite a gamble.

This had led me to believe that if there is too much load being exerted on the bike (i.e. the current being drawn from the battery is too high) then either the BMS or the controller trips and cuts out. However I am reluctant to believe that the BMS is causing the trouble as it has a 40A rating on it (this link shows the exact BMS) http://www.aliexpress.com/item/Electric-motor-car-13S-48V-40A-BMS-lithium-ion-battery-BMS-Used-for-48V-20Ah-30Ah/32484213150.html?spm=2114.13010608.0.62.evx6sX .

I should really change that $2 cutoff to more like $2.50, which is more reasonable for quality cells. Basically, the cheapest ‘good’ cells are Samsung 26F cells, which can be had for usually around $2.50 – $2.90 if you are buying in any large quantity, like at least 100. Expect to pay more like $3.00 or so if you’re buying only 40 cells. 26F cells are also limited to 5A discharge though, so you’ve got the same issue as with the NCR18650B cells from Panasonic.

You want to use unprotected cells because your BMS will be handling all the protection, and you don’t want individual cell protection circuits getting in the way or limiting current draw unnecessarily. So use only unprotected cells when building big multi-cell packs like these.

Is there same officially recognized method to come up with C ratings? Ping claims 2C on his LiFePo4 batteries, my Chinese-made “BMC” battery claims 3C. Can they just sort of say whatever they want? How do we determine the “real” C rating?

When it comes to choosing a BMS, the number of cells you have in parallel aren’t important. Only the number of series cells matters. The same BMS will work with 1 or 100 cells in parallel, as the voltage stays the same regardless of the number of parallel cells.

I want to build a 36v ebike battery for my 36v 500w motor. What battery you recommend for me which gives the enough current and capacity. My plane is to build a battery with 40 cells 10 in s and 4 in p,

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.

With the Multimeter I see that is everything OK, I see the voltage of the 4S in B+ and P-, but when I connect the motor nothing happens, the voltage goes to zero. At this moment I want to discharge the batteries and I connect B- to B+ and is working OK, of course.

Here is a an example of a large format soft pouch LiPo pack with 13 cells, and a BMS. This pack was built using cobalt LiPo soft cells with a BMS from a Chinese factory for an electric bike. You can see the top cell has been squished, causing the cell to fail and the BMS to shut down the battery, and not allowing it to charge or discharge. This pack is small and light (7lbs).  This $500 pack is now ruined, but  all is not lost since it did not start a fire, and it did NOT take the house with it.

In spite of the various chemical variations, lithium-ion batteries can generally be separated into two groups: lithium iron phosphate (LFP, LiFePO4) and metal oxides (NMC, NCA, Cobalt, Manganese).  Table 1outlines the differences between LFP and LiNMC chemistry classes on a cell level. The values in the table reflect average values as there is variation in each class.

Wear gloves. Work gloves, mechanic gloves, welding gloves, even latex gloves – just wear something. High enough voltage can conduct on the surface of your skin, especially if you have even slightly sweaty palms. I’ve felt the tingle enough times to always wear gloves now. In fact, my pair of choice for battery work are some old pink dish gloves. They are thin and provide great dexterity while protecting me from short circuits and sparks.

Since most welders have arms like mine, I’ll show you how I did it. I started by hot gluing two parallel groups together in an offset fashion, making sure the ends were opposite (one positive and one negative at each end, as shown in the picture). Then I snipped a pile of nickel strips long enough to bridge just two cells.

Nickel Metal Hydride is quite similar to Nickel Cadmium, but with a higher energy density and a safer environmental record when disposed of in landfills. This is the dominant rechargeable battery type in digital cameras and other consumer products that offer user replaceable cells.

I assume you mean 52V (14s, or 14 cells in series) which is a somewhat common lithium ion battery configuration. It works with most 48V setups but provides a little more power than a standard 48V (13s or 13 cell) battery. A good charger I recommend for 52V 14s batteries is this one.

There are six rechargeable battery types that have seen regular use in electric bicycle battery packs. We have never been involved with lead acid batteries, and discontinued dealing NiCad and NiMH packs in 2010.

This is how most Asian batteries are built, since they use the same size aluminum or plastic case, but offer different sizes and capacities of batteries in the same case. I’ve used arts and craft foam, which often comes in sheets up to about 5mm thick (and I use a few layers to fill larger gaps). For MUCH larger gaps where that thin foam is less desirable, I’ve seen people use styrofoam or even that green molding foam often used in pots to hold up fake plants. That stuff is a fairly rigid though, so maybe a combination of that stuff and a layer of softer foam for cushioning would be good.

I would prefer to go with lithium, but I have a couple of 75 volt (i think) cells from a UPS that are brand new. They are built from regular 12v (sixteen total) sealed lead units and would make the initial investment in an ebike that much more reasonable. One huge downside is that I hope to use the folding ebike in my homebuilt aircraft. As with ebikes, excess weight is to be avoided!

The watts (power) the battery can provide is totally dependent on the type of cells and the BMS rating. So until I know more about your cells, I can’t help you. But for an example, imagine you used cells that were rated at 5A each. 7p x 5A = 35A total power capacity. 35A * 24V = 840 watts, the total amount of power your battery can handle. But now let’s assume you used a 20A BMS, meaning the BMS can only handle 20A continuously. That’s your limiting factor, so your new total battery maximum power is 20A * 24V = 480 watts. Now just substitute the actual current rating of your cells and BMS to solve for your battery’s power capacity.

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?

Lithium batteries are not 100% fire-safe. Some batteries are more dangerous than others, depending on the chemistry, whether it has BMS or not, and what kind of casing the battery is in. If the battery is cased in metal its less likely to burn your garage down, than if its encased in plastic. batteries for electric bikes be aware that all BMS’s are not alike, some are good and others are crap, just like anything else in life.

Lithium battery: 36V. Motor: 250W high speed brushless gear motors. Type: Mountain Bicycle. Front Fork: High-strength carbon steel comfort shock absorption. Tire: High quality lithium tire. Charger: S… [redirect url=’http://electricbikebatterys.com//bump’ sec=’7′]