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Please see the video’s on RCgroups under LiPo fires. A simple 2200maH 3S battery pack blew the lid off a secured 55caliber ammunition can. Putting a LiPo pack in a closed metal case is a real “bomb” waiting to happen. See all the videos on RCgroups that show what happens when a battery is over-charged or over-discharged inside air-tight causes. The real solution is to make the case have a “preferred direction” of discharge……which can be very powerful. This is done by drilling holes in the case. But it stops the explosion factor. The best thing is to have a BMS on or inside the battery. Even if the cheapy Hobby King voltage monitor, that is much better than nothing at all. Also consider putting in a voltage monitor that has a temperature guage attached. When ever the pack skin gets above 85 deg C, you are in real danger of “vent and flames”. The temperature and voltage are that two big things that can make your battery pack safe………….also store the pack where if it does go to “vent and flames”, no human being will get burned.
Common lithium cobalt oxide (LiCoO2) batteries can catch fire or explode during loading and even when just stored. The safety depends on user precautions and the quality of the Battery Management System (BMS).
The @blixbike Vika Travel is the perfect #multimodal companion. Few #ebikes get this small batteries electrical ride this well! #blixbike #electricbike #ebike #foldingbike #electricfoldingbike #nycewheels 07.03.2018 – 02:51
Another type of electric assist motor, often referred to as the mid-drive system, is increasing in popularity. With this system, the electric motor is not built into the wheel but is usually mounted near (often under) the bottom bracket shell. In more typical configurations, a cog or wheel on the motor drives a belt or chain that engages with a pulley or sprocket fixed to one of the arms of the bicycle’s crankset. Thus the propulsion is provided at the pedals rather than at the wheel, being eventually applied to the wheel via the bicycle’s standard drive train. An electric mid-drive combined with a hub gear at the back hub may require care due to the lack of a clutch mechanism to soften the shock to the gears at the moment of re-engagement. A stepless / coninuous ratio gear hub or a fully automatic gear hub may reduce the chocks due to the viscosity of oils used for liquid coupling instead of the mechanical couplings of the conventional gear hubs.
When you buy a Hobby King pack, it will have a number of these large cell LiPo’s strung together like this 6 cell in-series (6S) pack. The big downsides of this pack is that it will only last you in best case maybe 300 charges and it is volatile, and susceptible to possible fire if not well managed and cared for. When using cobalt-based LiPo, it is best to use some kind of BMS, and also you should charge it in a safe location.
This step is somewhat optional. You should seal your battery somehow to prevent it from shorting on all of that exposed nickel, but it doesn’t necessarily have to be with heat shrink wrap. Some people use duct tape, plastic wrap, fabric, etc. In my opinion though, shrink wrap is the best method because it not only provides a largely water resistant (though not water-proof) seal, but also provides constant and even pressure on all of your connections and wires, reducing the risk of vibration damage.
To answer your question, you can definitely build your own auxiliary battery. It looks like they used a fancy right angled female XLR connector, but I imagine a standard female XLR connector will fit just as well. I’m not sure if you’ll be voiding your warranty though by connecting your own battery. Those XLR connectors can be purchased all over ebay and probably even at your local electronics shop.
Thank you for the very informative post, and it has helped a lot. I plan on building a battery pack with 20 cells with blocks of 4 in parallel, and then I am going to put those in series to make an 18.5V, 13.6A pack. Sorry if these sounds a little bit foolish, but I am not sure what kind of BMS I should be using. Would I be able to use any BMS or would there be an issue with having extra wires if the BMS can power more batteries in series?
Micah is a mechanical engineer, tinkerer and husband. He’s spent the better part of a decade working in the electric bicycle industry, and is the author of The Ultimate DIY Ebike Guide. Micah can usually be found riding his electric bicycles around Florida, Tel Aviv, and anywhere else his ebikes wind up.
Lastly, there’s a small chance that it’s just a faulty BMS. This method is annoying, but if all else fails then you can try swapping out the BMS. More than likely though, the BMS is doing it’s job because one of the cutoff conditions is fulfilled and it’s just trying to protect the pack.
Hi Court and thanks for all the info. I am in Montréal and would like to know in minus 15 and minus 25 what range may i expect? I am 160 pounds and would pedal, mostly flat and asphalt with 1/3 old railroad now small gravel. I am looking at a Surface604 Element 60 pounds 3 assist levels plus throttle. Weekly i go to a secondairy house 65 km away wich i pedal in 2.75 hours on my 18 pounds summer road bike.
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.
To shift optimally I suggest gaining speed then relaxing the force being applied to the pedals, shifting, then maintaining a gentle cadence until the chain is correctly aligned before exerting more force. This may be difficult on a pedelec system where the rider relaxes their input but the motor continues to pull hard. In this kind of situation it may be ideal to shift on a flat surface where little force is required to keep the bike moving forward. The problem here is that often shifting is done when encountering hills or starting from rest; just as more force is required to maintain speed. Long story short, be gentle when shifting and recognize that mid-drive motors pull the same chain that you do as a rider.
If you don’t find that, there’s still a chance that it’s the problem, and that the cells simply rose up to a higher voltage and matched the others again once the load disappeared. But it also may be that the load is too high for the BMS. Do you have a cycle analyst? You could slowly increase the throttle and watch how much current you are drawing until the point of cutoff. If it’s well below 40A then you’ll know it’s not a high current cutoff.
Technically yes, you can bypass the BMS for discharging and just charge through the BMS but this is not recommended. It is better to just choose a BMS that can handle your 50A discharge. BesTechPower makes some great BMS units that can handle 50A and more, depending on the model. They have many options.
I would like to know what input in terms of voltage and current i should provide to my battery of 36V 8.7AH. And also how the calculation goes if i want to build a battery for some other Voltage and current specification ?
First thing is regarding the cells – I have just order some Panasonic 18650PF like yours by chance (I was looking for Samsung). The delivered cells were made and charged in 2014, and the measured voltage now is around 3V (+/- 0.1v). So the voltage is basically the same for all of them but there are old, I think, even thaw never used and stored in a warehouse.
Suitable for electric bicycle & scooter, mechanical or electric forklift. Speed governor :Thin green (Speed handlebar Signal input) /Thin black (Negtive Power) /thin red(5V Positive Power). Ignition S…
E-bikes can also provide a source of exercise for individuals who have trouble exercising for an extended time (due to injury or excessive weight, for example) as the bike can allow the rider to take short breaks from pedaling and also provide confidence to the rider that they’ll be able to complete the selected path without becoming too fatigued.
Full suspension fat bike with a high quality mid-drive motor from Bosch and their updated 500 watt hour battery pack for extended range. Cool fluorescent paint job that extends all the way through the fork, rear shock housing,……