DIY Electric Conversions - Lithium Battery Bottom Balancing
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- čas přidán 7. 05. 2013
- An example of how to bottom balance your lithium battery pack.
This video was filmed in 2013. Components used may not be what is currently used for a current conversion. For up to date information regarding converting an internal combustion vehicle to electric, visit www.EV4Unow.com. Please address all questions or comments to info@EV4Unow.com.
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I had not found this information elsewhere and it's exactly what I needed, thanks!
We draw them down in groups of four (in series) to around 12 volts or a little less. From there you want to address them individually. It is a time consuming process but it can be a life saver to your cells. We do it with four in series as it is easy to find a 12 volt load. But you could also do it with a parallel configuration. Remember to closely monitor your cells as to not over discharge one.
Thanks Richard, I get that. Thanks again for all you do for all of us out here. My business start-up is well under way, and I am going to try to get out there for one of your weekend classes. I'm starting my fund raising now, hopefully I will see you in June or July.
Right you are. We typically are only doing one cycle.
Thanks for your input and for watching.
Thanks for watching and sharing.
Hi, I like your videos, they are very informative and enjoyable, thanks for making them.
I have both the Powerlab and JLD5740 and prefer the JLD5740 a little more because it doesn't matter how many times it has to cycle, it could be 10 or 50, it just keeps cycleing till it quits. I've bottom balanced 6 cells hooked up in parallel with 20 feet of 3/8" rebar as a load running 160 amps.
I look forward to meeting you in person, and wish you all the best in business.
The PowerLab 8 will run through a cycle also. Just not going into that degree of detail for this video.
Appreciate you sharing your experience. As you know there is more than one way to skin a cat, and perhaps in the future, we can do videos showing multiple procedures to accomplish a given task. A good idea, just not enough time.
Informative video, thanks for the details! I'm jealous of all your cells :P
Great vid,,thanks. You would not have to inspect the brushes if you used a AC motor. Then there would not be any maintenance except for charging the batteries.
It's the little things. You are screwing down the cables and repeat the Powerlab 8 discharge.
I use the JLD5740 cause it's switching on again automaticly. Great work.
Regards
Mathieu
Can you tell me in which other video you explain the why of bottom balancing? I looked through your uploads, and didn't see it in the titles. Thanks!
Richard, do you have to draw down one battery at a time or can you hook the group of four up in parallel and draw them down together?
Hi!
Thanks for the video. I really like the idea of bottom balancing.
I'm working with 18650 cells mostly, I still hope you could answer these questions:
- While the nominal voltage of the 18650 is 3,7 mostly, could you discharge them to below 3 volts regularly, and would his give more capacity?
- Why do you only charge the batteries you are using to 3,5, while Lithium Ion can be charged up to 4,15/4,2? Has this anything to do the the composition of these specific batteries, or is this a choice because of safety?
Battery cells have three voltages to be aware of. Maximum voltage, nominal voltage, and minimum voltage. Nominal voltage is used to calculate capacity. Minimum and maximum voltages are limits that you must not exceed.
Could you provide a link to the video referenced at the beginning that is the prior video that discusses why you want to bottom balance?
I believe this is the video you are referring to.czcams.com/video/84oseQR1jpY/video.html
Check out our "How-to Convert to Electric, Part 6" video.
Hi Richard, great video, thanks for the help. May I ask a question.
is the technique the same for cells that are paired in my pack? , can I bottom balance while the cell pairs are still connected in series to the rest of the pack? and finally do I need to disconnect my mini-bms boards from the cells while bottom balancing?
thanks again
If you are using a battery management system, then bottom balancing is a waste of time. It's one or the other. Why would you bottom balance your cells when the BMS is going to be top balancing the cells?
I thought that the pack had to be bottom balanced before fully charging, as the mini bms can only move very small amounts of energy to "fine tune" the balance at the end of the charge cycle
Please direct all questions and comments to info@EV4Unow.com
Thank you for watching.
Dear.... After we do the bottom balancing to the voltage... Lets say from 3 Volts to 2.6volts( from each cell), What abt the Capacity ( Amp)? do we have to do the balancing too?.. Waiting for your reply.. Thank alloot.
Address questions to: info@EV4Unow.com
Is one of those devices necessary bottom balance, how do you do it without one of those devices
You can do manually, but it takes a lot of time and attention. There are also other methods for bottom balancing. Please address questions and/or comments to info@EV4Unow.com Thank you for watching.
So basically discharge them together in series until they get to 12v(wait is that 12v total for all the 4? So average 3v each?), then discharge them individually for a fine discharge until they are 2.75v each and then hook them back up in series and charge them together?
If you discharge them to a specific voltage how long will it stay at that voltage?
Thank you for your videos
Bottom line...discharge to 2.75 volts per cell. Wire your pack in series and charge the pack to a total voltage of (number of cells times 3.5) After 38,000 miles of driving we have a pack that all of the cells are still exactly the same voltage as when installed. Makes me a believer in bottom balancing.
+EV4U Custom Conversions So let me ask you this, would it be any different if you just charged each cell separately to full capacity and then connect them together and start using? I would call that top balancing :-) I am in the process of building small battery pack and that's my strategy plus measuring each cell capacity and try to match cells in parallel packs, please let me know if this is wrong and why.
Please address all correspondence to info@EV4Unow.com.
Thank you very much.
+EV4U Custom Conversions It would be greater benefit for everyone if you would respond here so that other people could read the answer as well.
Hey Guy.. Just saw your video,, I'm building a power wall and using a large BMW hybrid pack, i'll be modifying it for a 48V system.
from what i have learned, I won't need a BMS as i thought, and that bottom balancing is the way to go for such a large pack. BMS is better for smaller things. the cells i am using are used of course, just fine for beginning system. I will have a bank capacity of over 660Ah worth.
It will be a lot of work.. all the cells are the same, but the packs are different sizes ( 3s , 4s, and 5s ) i have to arranged them to where i obtained 13s6p
Any advice you can give ? I'm not a novice at this,, but i am a novice for dealing with such a huge size bank.
Thanks for your videos..
Please address questions to: info@EV4Unow.com
what is the easier way to equalise battery quickly?
Please address your question to info@EV4Unow.com Thank you for watching.
How are these GBS cells doing long term?
The LiFeMnPO4 chemistry seems to have more of a voltage drop under load and they don't perform as well in cooler temperatures as the LiFePO4 chemistry. The terminal connects require much more attention on the GBS also.
We have not used them for years. We prefer the CALB cells.
But these GBS cells are LiFePo4 right?
And let me know why do you prefer CALB?
No they are not. As per my first reply they are LiFeMNPO4.
See my original reply.
What's the capacity of those cells? thanks a lot for the video ! it is very important to this world believe it :)
100 Ah
I got 95 lithium ion batteries of 3.7v each for my inverter. What device or where can I buy device to bottom balance the cells.
This is how I arranged the cells.
I connected 19 cells in series and made five stack of them. Then connected five of the 19 cells in series in parallel. Each 19 cells in series is 70.3 volts.
I want my lithium ion batteries to go so many cycles so I will never charge to the 70.3 volts normal capacity.
I want to charge it to maximum of 64 volts . For this reason, I think I shoukd not do top balancing rather only bottom balancing.
Is there any deceive I can buy to bottom balance my 95 cells or how do I bottom balance it?
Check out this video. czcams.com/video/4rS2j77oMDE/video.html