LiPo packs that are homebuilt (without a BMS) can be extremely dangerous if you do not approach your battery with a lot of knowledge and care. Be sure to research extensively before building such a pack. Many E-bikers construct packs with no BMS using Turnigy/Zippy packs, acquired cheaply online through the Hobby King company which is based in China.  For those who risk running their batteries without BMS they still use sophisticated chargers to balance their packs and constantly monitor the health of their cells.

A 48 volt 20-Ah pack  contains 960 watt hours and once you get close to 1000 watt hours you are getting serious commuting range which most e-bike manufacturers promise but do not deliver…think 30 miles.

RC motors and RC batteries used what E-bikers considered to be fairly lower voltages (14V-22V), which RC enthusiasts needed in order to keep the batteries small in the compact RC planes. The number of E-bikes outside of China is low compared to the the number of global RC products. People who would never ride a bicycle under any circumstances might have several expensive RC models. Since RC components were designed to use lower voltages, the users tweaked their systems to draw more amps for better performance. RC buyers didn’t care about the occasional fire (a rare event), they wanted higher-amp batteries.

Hi Colleen! My experience with Sealed Lead Acid batteries is that they should be recharged monthly, even if you’re not using them. They tend to be more sensitive to cold weather and can get damaged if they fully discharge (even if you didn’t use it… the battery goes down on its own over time). I cannot say how long you’d need to charge it but probably at least 6 hours? Most of the time ebike chargers will have a light that goes from red to green when the pack is full, but otherwise I’d just try for six hours or so and then unplug it 🙂

I have now come to the conclusion however that i want a pack that is 48V and capable of running a 1000w motor for atleast an hour. I live in a hilly area, i use a downhill bike (heavy) and im not the smallest guy. Im feeling a bit insecure about putting too many cells in parallel. Through the years i’ve read that the consesus is that more than 4 cells in parallel is a risk. Since a 13S4P pack is about 12Ah (with good batteries) i was wondering if you had any input on how i should move on?

Lithium Polymer cells, used mostly in the e-bike community to describe soft-pack RC like cells, generally have a lighter weight per watt-hour, and they have a high percentage of cobalt in its anode, which makes them very power-dense (lots of amp-hours in a small package) and also capable of very high amps of discharge (for high performance). Single cell LiPos are connected together in series to form a battery pack.

Spot welders for batteries aren’t the same as most home spot welders. Unlike the large jaw spot welders for home workshops, battery spot welders have the electrodes on the same side. I’ve never seen them for sale in the US, but they can be found pretty easily on eBay and other international commerce websites. My full time use welder is a fairly simple model that I got here. A highly recommended source for a slightly nicer spot welder design (pictured below) with both mounted and handheld electrodes can be found here.

Samsung SDI’s superb cell balance technology contributes to the uniform quality of the packs and driving units, and ultimately to the quality of the E-bike. Our batteries help to provide E-bikes with quality to the consumers. As a testimony to their outstanding quality and safety, Samsung SDI’s Li-ion battery cells are preferred by high-end E-bike makers and driving unit companies that lead the E-bike market.

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.

Great article! Have ordered everything BUT i have a big problem with the spotwelder. Most homes in europe are limited to 10A and this spotwelder alone drags 15A just to powerupp!!!! I can even start it without blowing both fuses! And when welding it wants 50A-800A which you need a an actual POWERPLANT for!

I guess I’ll just have to risk some deterioration on the cells. I don’t think there’s much of an effect, as I did it on an old 18650 cell to test. The joint and surrounding areas were cool to the touch within 1-2s of removing the heat.

Actually, the protected cells aren’t a great option for ebike packs. The protection circuit on every cell can overcomplicate things, not to mention that it usually isn’t rated to handle the same current the cell could without a protection circuit.

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Sealed Lead Acid (SLA) remains the most affordable entry-level battery option. However, their life-cycle is so short, it is more cost-effective to pay twice as much to get a lithium-based battery that will last 6-times longer.

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.

If the 4P10S multi-tube arrangement was for occasional use on long journeys, then it would be reasonable to release all of the cells and to charge them individually or in parallel to about 4V using a normal little single cell charger. Each would then be “top balanced” yes? Then mount them in the tubes, compress and connect the top terminal array and good to go. I’ve still got the quandary about whether to connect them in parallel to the main battery large output terminal.

I hope not to have to replace the whole battery pack and wondering if it can be salvaged by replacing the just the dead cells and burnt connectors, or do you think the damage is too extensive to be worth repairing it? [redirect url=’’ sec=’7′]