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Newbie needs a Mentor
#1
Hey All,

I'm just getting into this.  I have a technical background in Aerospace/Astronautical Engineering, but do not have a EE focus.  While I work with power systems (PV and Li-Ion battery packs), I am not involved in the technical design so much.  I want to work toward becoming more independent electrically from the grid through the use of solar and power storage at home.  I'm starting small and would like to begin building power banks and power walls.  However, I need a mentor.  I am working with a journeymen's level knowledge of these systems, but there are many intricacies when it comes to batteries where experience is required.  I was wondering if anyone would have time to be my "go-to" person for questions as I worked on building my knowledge of these systems.  Questions like, how do you check individual cell battery health when its in a large pack of hundreds of cells?  When is it absolutely necessary to replace a cell...charging dos and don't with reclaimed 18650...etc.

I'd appreciate if anyone would be available!  Thanks!
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#2
Welcome to the forum. Glad to have more members to gain and spread the wealth of knowledge we have here.

I would recommend to please read over the FAQ section. It's located on the main page. Also read through several of the builds in the build section to get an idea of what's been done. Since there are so many members who have contributed to this community, there isn't really any "1" mentor, but more like a whole community of mentors.

To start off with, you need to collect the data that you will need to power what ever devices you have for how ever long you would like to do. This is information only you can provide. There are many ways of collecting that information, either by using the whole house power consumption (if going for a whole house set up), or reading the labels of all the specific devices you want to run in a separate panel.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
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#3
Hello Mobinik,

Welcome to the forum.  Like Korishan said there is a whole community of mentors.  Can you tell us more about what your first or most pressing project is with lithium ion batteries?  My "first" project is building a hybrid powered waterski boat, with reclaimed 18650 batteries.  However in the process of collecting lithium ion batteries and making small scale test and proof of concepts  I have a very small solar panel and very tiny powerwall that I use to power all my reclaimed lithium ion batteries and testing stuff.  I also just made a second "micro powerwall" out in my boat that I use to run a few small fans to keep it dry and mold free, and use as another test bed for wireless BMS stuff.    So don't be alarmed if you find other ways to use this new technology.  I will be making a big powerwall for our house after the boat project is functional (The boat project will never be done...I will probably always be improving it).

Anyway welcome to the board....Read a ton of stuff on the board and alot of your questions will be answered, as well as new questions will pop up, and tell us about how you plan to use lithium ion batteries.

-Rip.

P.S.  I have an Aerospace/Astronautical Background too.  Let me know if Boiler Up means anything to you.


Quote:Hey All,

I'm just getting into this.  I have a technical background in Aerospace/Astronautical Engineering, but do not have a EE focus.  While I work with power systems (PV and Li-Ion battery packs), I am not involved in the technical design so much.  I want to work toward becoming more independent electrically from the grid through the use of solar and power storage at home.  I'm starting small and would like to begin building power banks and power walls.  However, I need a mentor.  I am working with a journeymen's level knowledge of these systems, but there are many intricacies when it comes to batteries where experience is required.  I was wondering if anyone would have time to be my "go-to" person for questions as I worked on building my knowledge of these systems.  Questions like, how do you check individual cell battery health when its in a large pack of hundreds of cells?  When is it absolutely necessary to replace a cell...charging dos and don't with reclaimed 18650...etc.

I'd appreciate if anyone would be available!  Thanks!
Reply
#4
(03-26-2020, 04:49 PM)mobinick Wrote: how do you check individual cell battery health when its in a large pack of hundreds of cells?
Welcome.  Everyone is a mentor and a student here.
The best way is to monitor the voltages of the packs relative to each other.  If the voltage of one pack strays, you know that it has a problem.  It may just be natural degradation (gradual capacity loss), partial internal short (self discharger, or "SD"), full on short that breaks the fuse / pop the CID protection device.  For more in depth look into my procedures:
https://secondlifestorage.com/showthread...3#pid61023


(03-26-2020, 04:49 PM)mobinick Wrote: When is it absolutely necessary to replace a cell
Really, only when it is self-discharging more than your balancing circuit can compensate for, but not enough to break the fuse.  Oh, and when it's spewing fire.
Though I recommend staying on top of things and replacing cells sooner rather than later.  Makes identifying future problems easier.


(03-26-2020, 04:49 PM)mobinick Wrote: charging dos and don't with reclaimed 18650...etc.

*For daily use:
Stay below 4.1V, ideally less than 4.05V.  Not an exact science, but lithium ion cells degrade quicker when kept at high voltages.
Stay above 3.3V.  The cell will live (exponentially?) longer the shallower the discharge depth.
Not sure how accurate the data is, but it's a good guideline:
https://batteryuniversity.com/learn/arti..._batteries

*For initial testing, you'll want to do one full 4.2V charge/3.0V discharge/4.2V charge cycle to test the cell for capacity (capacity degradation, aka State of Health SoH%), and if it's got SD issues.
Modular PowerShelf using 3D printed packs.  50kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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#5
[quote="Riplash" pid='61024' dateline='1585537476']

P.S.  I have an Aerospace/Astronautical Background too.  Let me know if Boiler Up means anything to you.

[quote]
Hey All,

Haha not a Purdue guy, I went to Iowa State!

Yeah I plan I’m starting these projects small and scaling up. Long term I’d like to be able to install a PV system on my house and not pay for anything other than the electrician setting up my inverter/grid connection.

For now, I want to build a 12V pack that can be used for outdoor camping. Small refrigerator and hot plate.

I’m plan on first building a basic 3SXP pack to get the intricacy down.

Unless anyone thinks it’s a bad idea, I likely won’t invest in a spot welder for awhile and just solder all my connections.
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#6
(03-30-2020, 04:02 PM)mobinick Wrote: [quote pid='61024' dateline='1585537476']
Quote:For now, I want to build a 12V pack that can be used for outdoor camping.  Small refrigerator and hot plate.

I’m plan on first building a basic 3SXP pack to get the intricacy down.

Unless anyone thinks it’s a bad idea, I likely won’t invest in a spot welder for awhile and just solder all my connections.

[/quote]
Using Lithium Ion batteries to replace a 12V lead acid battery is not just straightforward as using a 3S.  Most 12V things have a high voltage limit of 14.5 to 15 volts, and a low limit of 9.5 volts or so.  So with a 3S system you can charge the batteries to 12.6Volts but then you can't use all the capacity once the voltage gets below 9.5 volts or so.  However with a 4S system you might burn some of the 12V stuff by overvolting them if you charge the batteries up to 16.8.

However I use this to my advantage.  I have a few 4s x 10p battery packs, that I keep in my car and truck as a jumper pack.  I put a small buck convertor and a USB power Jack as well as a 12V powersocket.  I only charge the battery packs to 14.5 volts and balance them.   This is only giving them about 50% capacity.  Which is plenty for my use.  They will still jumpstart my truck, a work forklift, and I can use it to charge my phone and run 12V stuff.  This is also better for the batteries too, because storing the batteries at 100% charge and then keeping them in a Hot Car, shortens the lifespan of the batteries.

So depending on how you are going to use your camping battery packs you might be better to use 4S rather than 3S.  Or you could also by a buck/boost converter too.  But that might be best saved for future learning.

Just something to think about.
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