Next, I added the third parallel group after the second, hot gluing it in place in the same orientation as the first, so the top of the pack alternates from positive terminals to negative terminals and back to positive terminals along the first three parallel groups.

When you wire in series you only increase voltage, not amp hours. So you’d have a 48V 5AH pack in that setup. Not enough range, in my opinion. If you want my advice, the single best upgrade you can do to that bike is to replace the battery and controller for 48V units. It will give you about 30% more speed and power. You won’t need to drill vent holes or anything, that motor can handle 48V as long as you aren’t riding up any 5 mile long uphills with a 250 lb rider. Shorter uphills and flat land will be fine all day long.

A lot of DIY’ers these days are making the extra effort to install a BMS in their home built batteries. Adding a BMS is the way to go if you want your battery to be fire safe.  BMS’s can range from a simple hobby king cell log with an audible alarm if the pack gets too low or too high, to an expensive custom-made BMS complete with pack shut offs.

Grew up in Los Angeles California, US Navy submarine mechanic from 1977-81/SanDiego. Hydraulic mechanic in the 1980’s/Los Angeles. Heavy equipment operator in the 1990’s/traveled to various locations. Dump truck driver in the 2000’s/SW Utah. Currently a water plant operator since 2010/NW Kansas

While NCA is the clear winner by storing more capacity than other systems, this only applies to specific energy. In terms of specific power and thermal stability, Li-manganese and Li-phosphate are superior. Li-titanate may have low capacity but this chemistry outlives most other secondary batteries in terms of life span. It has also the best cold temperature performance. As we move towards electric powertrains, safety and cycle life are becoming more important than capacity alone.

If you are using 2.5AH cells then yes, it will be 5AH with a 2p configuration. If you use cells with higher capacity, like Sanyo GA cells that are 3.5AH, then you’ll have a 7AH pack with only 2p. Make sure your cells can handle the current that your electric scooter (and namely the controller) will try to draw from it.

One question regarding the specific battery BMS you used in this build: It uses a different wire for charging vs discharging the battery. Does this mean that the regenerative braking feature cannot be used for this battery?

Regarding that welder, I’ve used it on a 20A circuit but I don’t own it (it belongs to a friend of mine) so I can’t give you the best firsthand experience as I’ve only used it at his place on a 20A circuit. My welders, which are similar but a slightly earlier model, are run on a 20A circuit at my home. I live in Israel and we have 220V wiring at home like in Europe, so I can’t tell you for sure how it will work on 110V. If there is the option of running it off 220V in your garage or laundry room, that could be another option, but I’ve heard of people running on 110V in the US without problems so I can’t say for sure. Sorry I’m not more help on that front.

Once I’ve got all the cells I need checked out and ensured they have matching voltages, I like to arrange them on my work surface in the orientation of the intended pack. This gives me one final check to make sure the orientation will work as planned, and a chance to see the real-life size of the pack, minus a little bit of padding and heat shrink wrap.

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It’s not impossible, but I don’t have high hopes. When a few cells die like that, they tend to kill the other cells in the same parallel group and often can kill cells in the series groups adjacent to them. You could be looking at replacing a large number of cells outside of the ones with obvious damage, and it will be hard to confirm that you’ve found all the dead cells without pulling apart most of the pack. If you’d like to try, there’s a chance you can end up saving the pack for less than the cost of replacing it, but it’s going to be an uphill battle.

If I regroup my 12 paralled cells in 10 modules, can I then join these in series using single wires (one for neg, one for pos) between modules, instead of wiring each terminals of each cells like you are doing. Could this affect BMS and/or have any negative impact on cells balance?

Used PL-350 electric bike kit, The battery does not charge. Charger is fine but only shows a red light. It sat dead for about a year. Then the controller showed about 80% after charging. Everything wo…

Next, we’ll need to wire multiple 18650 cells in parallel to reach our desired pack capacity. Each of the cells I’m using are rated at 2,900 mAh. I plan to put 3 cells in parallel, for a combined capacity of 2.9Ah x 3 cells = 8.7 Ah. The industry abbreviation for parallel cells is ‘p’, meaning that my final pack configuration is considered a “10S3P pack” with a final specification of 36V 8.7AH.

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Rang: 18-25km(36v 6ah). Motor: 36V 250W brushless. Battery: 36V4/6AH lithium battery. The eco-friendly bicycle is 100% electric and emissions free, saving both your wallet and the environment. New Out…

36V 10ah Lithium battery (Included with the battery is the charger and mounting Bracket). Standard 26 in Front Wheel 500w brushless motor hub (works with V-brake or disc brakes). Pedal Assistance syst…

One term you will frequently come across is the ‘C’ rate of a battery pack. This is a way of normalizing the performance characteristics so that batteries of different capacity are compared on equal terms. Suppose you have an 8 amp-hour pack. Then 1C would be is 8 amps, 2C would be 16 amps, 0.25C would be 2 amps etc. A higher ‘C’ rate of discharge is more demanding on the cells, and often requires specialty high rate batteries.

This pattern continues until we’ve got all 10 parallel groups connected. In my case, you can see that the first and last parallel groups aren’t welded on the top side of the pack. That is because they are the “ends” of the pack, or the main positive and negative terminals of the entire 36V pack.

While it is possible to build packs with any number of cells for just about any voltage, most have standardized in 12V increments, with 24V, 36V, and 48V being most common, and 72V used on occasion. Battery chargers are usually only stocked for these voltages as well.

Almost all consumer electronics that have a plug-in charger these days are powered with lithium batteries because they can store about 3 times more energy than NiMH. Small devices like cell phones, mp3 players, and other gadgets typically have lithium-polymer packs, as these can be formed in conveniently shaped thin rectangular pouches. Larger devices like laptops and the new lithium cordless power tools generally use cylindrical Lithium-ion cells of a size smaller than a ‘C’ but bigger than a ‘AA’. These are spot welded in series/parallel combination to give an appropriate voltage and capacity for the job.

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.

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 batteries for motor scooters 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 .

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. Also be aware that all BMS’s are not alike, some are good and others are crap, just like anything else in life.

Make sure to consult the wiring diagram for your BMS, because some BMS’s have one more sense wire than cells (for example, 11 sense wires for a 10S pack). On these packs, the first wire will go on the negative terminal of the first parallel group, with all the rest of the wires going on the positive terminal of each successive parallel group. My BMS only has 10 sense wires though, so each will go on the positive terminal of the parallel groups.

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.

Nominal capacity: 12Ah (Fully charged after 0.5C discharge to 38V capacity). Cycle life: Standard charge and fast discharge cycle 500 times, the capacity will notless than 60% of the nominal capacity.

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.

Regarding the soldering of cells: generally it is not recommended as no matter how you do it, a soldering iron will still transfer more heat than a spot welder. That being said, I have seen packs that have been welded using both solid or braided copper wire. I’ve also seen someone use copper wick soldered to the cells terminals. It’s impossible to know exactly how much of an effect that the heat transfer had on the cells but if you don’t mind taking a risk of some level of deterioration of the cells performance, then it technically is possible to solder the cells together.

The very first thing I want to say is this: While it is true that lithium batteries, commonly used in ebikes today, can catch fire… it is VERY rare for them to do so, for several reasons. I suggest you are more likely to be injured by a falling coconut than to have a Lithium fire at home. Did you know that battery powered hand tools, laptops and even cell phones have burned down a number of homes and businesses? And yet to most people these products seem completely safe, even after being dropped or damaged they hold up well and never have an issue. Whether it’s some other portable electronic device or your electric bike, being alert and aware of how to treat the battery and what to do if there is a problem is advisable. [redirect url=’’ sec=’7′]

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