I will add more information about these types of batteries..
Never let them go below 2.75 volts, or you well ruin the batteries. Your power wheelchair controllers well need an accurate voltage meter.
Here is how you prepare a new bank of batteries before first installing them into your chair.
Lithium Battery Bottom Balancing
An example of how to bottom balance your lithium battery pack.
http://www.EV4Unow.com
prior video that discusses why you want to bottom balance?
How to Convert to Electric Series Part 6.wmv
LiPo Explosion
(Eng.)
Someone heard something like a “fart” inside the plane while it was chargin their LiPo batteries, a bit of smoke went of the cowl, so, we had to take out the plane… then BOOOOOM!! FIRE!!, EXPLOSIONs!!, MORE FIRE!!, WALLET PAIN and more…
Lipo explosion – aka: idots with batteries!
Safely discharging a lipo for disposal
Battery Pack Balancing
A video about battery balancing! Mostly about the LiFePO4 chemistry.
Coulometric Efficiency Article
http://qnova.ca/uploads/3/1/7/2/3172593/a_high_precision_study_of_the_coulombic_efficiency_of_li-ion_batteries.pdf
Enjoy!
Bike Specs
Motor – ME-1003
Controller – Alltrax 7245
Batteries – LiFePO4, 70AH, ~80V
BMS – Custom
Front Tire – 110/70-17″
Rear Tire – 150/60 -18″
Chain – 428 O-Ring
Gearing 15T Front, 55T Rear
Range ~100km
Top Speed ~130km/hr
COMMENTS
FolkPhotographer
Thanks for the info..I used to be an automotive mechanic until I was run over by a car and now I am creating a custom power wheelchair with lithium ion batteries..
Is this true?
Johan Sagaert
Hi, there seem to be circuits ( LTC3300-1) available now doing the top and bottom balance without waste of energy, the cells with lowest voltage,get some help from the more fit ones by means of a convertor circuit. Complex, but worth its cost for high power packs.
Reply
Electric MotoVlog
Ah excellent. It probably goes in conjunction with the 68XX series by LTC. I have used the 6801-1 a while back (when it first came out). It was really nice except that the serial port on it was horribly unreliable. I think they have much better variants of it now though.
Zik Zak
What about supercapacitors? Do they have large disprecancies too and so a need for a charge balancer?
Reply
Electric MotoVlog
Yes you are correct. One technique is to put a resistor in parallel with each capacitor in the series string. All the resistors should be roughly the same value. As the voltage across any one capacitor goes up it will discharge more current into it’s parallel resistor. This is a very crude, but effective way of balancing and it is widely used in consumer electronics.
electrodacus
Good video. Not sure why it was not in my subscribers video list. Coulombic Efficiency has effect on the cell imbalance but you exaggerated a bit to much your example 🙂 and at hinger charge/discharge rates over C 1/10 the Coulombic Efficiency will be very, very close to 1 not that much parasitic reactions will occur because of the limited time.
On good quality cells the cell imbalance will be extremely small and cell balance will not be needed at every charge but the imbalance will grow larger with each recharge cycle so is a good idea to have a small balance done at every recharge to keep the battery pack for dropping in capacity.
Electric MotoVlog
Thanks! Yes you are correct. I exaggerated for sake of example… I’m no electro-chemist so I don’t understand some of the other effects that lead to pack imbalance. I did my best to comment only on what i learned from the technical article (in description). BTW i have been keeping an eye on your SolarBMS. Good stuff!
Inexpensive Lipo Discharger That Works!
3-in-1 Battery Balancer, Voltage Indicator and Discharger
I’m glad I finally found this device (thanks to a thread I am subscribed to on RC Groups).
There may be many of you that wonder why I would want one of these.
Let me see if I can explain why:
We do not have power at our flying site, I don’t have a generator and I choose not to charge at the field using my car battery etc. I end up buying as many batteries per plane that I can reasonably fly in one day.
I charge up enough batteries for each of the planes I will take to the field that will get me through the day. For a wide variety of reasons, I may not be able to get all my flights in so I might end up coming home with a few fully charged packs.
Lipo Storage Safety: I have come to believe there is a greatly reduced risk of a lipo fire or at least the intensity of a lipo fire if they are stored in a metal container at storage voltage.
Over the past few years, we have done a lot of experimenting destroying lipos and while we can get spectacular results setting off fully charged packs, we get nothing but a little fizz out of packs that are at storage voltage. I personally know of a few guys who burned down their homes because of Lipo mishaps and that’s a club I don’t want to join!
So, when I get home, I discharge any full packs left over from the day. I have six, good quality chargers (two duo chargers and two single chargers) and I have been using their discharge feature to draw down the packs. There is a lot of heat generated by the discharge function and I have never been happy about that. Recently, one of my Thunder Power 820 chargers started to act funny and started to perform functions at a greatly reduced speed (response to button pushes, etc.) Re-flashing the firmware did not help. I am thinking that I may have damaged it by overheating it by discharging two 5000 mAh lipos back to back.
I was looking for an affordable discharger and found a thread on RC Groups of like-minded individuals. These guys are electronic wizards and have designed and built one. I was in the midst of assembling all the bits and pieces to build one based on their design when someone posted a link to this device.
For about 20 bucks (including shipping), this was a no-brainer.
I have discharged about 10 packs so far and it works like a charm.
Note: I did not receive this unit free for evaluation and/or review, I bought a couple at full pop.
Here is a link to the product:
Here is a link to an even less expensive model that is exactly the same but only uses one 50W bulb as the load. I’d rather pay the extra 3 bucks for the 150W version to save a lot of time babysitting the packs as they discharge.
Here is the link to the thread on RC Groups if you’re keen to build your own. The total cost of the DIY version is more but it is more robust and can handle a bigger load.
http://www.rcgroups.com/forums/showthread.php?t=1901849
Thanks for watching!
Royalty Free Music:
Sex & the City by Re-Drum from Jamendo.com
Crimson Fly by Huma-Huma from YouTube’s Audio Library
DIY 55$ 24AH Lithium-Ion 18650 E-Bike battery 100+ Mile Range: complete build
Previous E-bike Video: https://www.youtube.com/watch?v=oYXre…
in this video i build the second 24v 24ah lithium battery block for my 48v 24ah bicycle battery. i built this pack from low quality 18650 cells. each 6 cell pack cost 4.99$ so thats only about 85 cents per cell. even if they are low quality that is wonderfully useful.
in this video when i say a cell is “unstable” i mean it is more likely to short out when it’s voltage is dropped due to metal buildup on the plates.
the main differances between good quality cells and poor quality cells such as these are due to the cheep cells being made of lower quality materials. some of the differances include
1: lower chemical-electrical conversion efficiency
2: lower capacity
3: faster self-discharge rate
4: shorter life span
these characteristics dont ruin their functionality though, they are wonderfully useful even at the worst quality.
Dangers with 18650 3.7 Volt Li-ion Batteries Exposed and How to Make Them Safer
Dangers with 18650 3.7 Volt Batteries Exposed and How to Make Them Safer. I was taking batteries out of laptop battery packs and I was getting flashes of shorts when I did not expect them. It turns out the positive and negative parts of the battery are less than 1/8″ apart from each other with only a very thin piece of mylar covering them for insulation.
I know many use these batteries for powering e-bikes, in fact I am planning on doing the same. But when i discovered just how close to danger we are to a horrific in-ride accident, I knew I had to find a better method for mounting and protecting them.
These batteries are being put together for my own e-bike build which I am creating here on Youtube, so subscribe and stay tuned 🙂
Wheelchair Rights - See Atruthsoldier.wordpress.com 