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Forum Index : Electronics : Small 18650  battery build

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BenandAmber
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Joined: 16/02/2019
Location: United States
Posts: 961
Posted: 09:20am 29 Aug 2020
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I have 130  ICR18650-28A SAMSUNG SDI batterys

I would like to build a small 48 volt battery

The battery would be for mobile use with the little China 4 mosfet inverter

The very first one we made with the help of the good people on this form



I gave it to my dad and we upgraded him with a larger inverter

I am very cheap/poor so if I have to spend
money on a bms I want a very cheap one

If I spend over 30 bucks on a bms I would like the battery to last a very long time

I have read if you don't fully charge and  discharge it will last much longer like electric cars

Can I use a small bms and relays for higher amp charge and discharge

Should I just fully charge and discharge

I have read a bunch so many opinions

I have had the best luck of my life by following the opinions on this site

That is why I want to know what you guys think

I still haven't finished the farm inverter I have to buy a large drill bit and a few feet of flexible wire to finish it


That chokes heat srink is a 20 ounce soda bottle that is why I am now saving them!!

All soda bottles make realy good easy to use large heat srink

I have also wound another Transformer after the farm inverter Transformer

It is a very ugly experimental Transformer



It is 120/240 volt secondary 32/64 volt primary

The core is close the size as a power Jack as4

I have used alot bigger wire than the as4

I was told by Sid that most of the heat in the power Jack tranformer was in the wire

So big wire on smaller core I will be testing the pefomance of it very soon

I have a gut filling a few of the people on this form can tell the results before testing

It would be nice to know what to expect

Thanks everyone have a blessed day
Edited 2020-08-29 19:28 by BenandAmber
be warned i am good parrot but Dumber than a box of rocks
 
Revlac

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Joined: 31/12/2016
Location: Australia
Posts: 1024
Posted: 11:26am 29 Aug 2020
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18650 2.8Ah  so that would be 13s 10p arrangement, that would be a little over 20ah on a good day, at about 53.3 volts.

To keep it within a good working range 3.6volts to a maximum of 4.15volts, running them at 4.1volts gives you a little headroom to keep them balanced, do not go 4.2 or more.

I have been running with these for years.

Are they all good new batteries of the same age?  if so a bms might work

if they are all different ages and used, then a BMS could be trouble.

Anyone using these batteries must be prepared use them with respect, to avoid failure,  same with any battery type really, they all should be treated well to get the best out of them.

20ah really isn't much, but light loads might be ok.
Cheers Aaron
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nickskethisniks
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Joined: 17/10/2017
Location: Belgium
Posts: 458
Posted: 09:12pm 29 Aug 2020
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Hi, it's getting a nice build.

Everyone has his own opinions about how something should be done. In my opinion the number one rule is: it's very important to threaten those batteries with respect, take a BMS! BUT, know your BMS as well, if you are going to under charge them, don't take a cheap/simple BMS, most BMS have a fixed under and over voltage protection in them. But also a fixed balancing function. So if you charge only to 4 or 4.1 it won't kick in and won't balance your cells properly.

I won't use them without, in the beginning it is all ok if they are from the same new "A" quality batch they are as good as identical. But they won't stay identical when they are aging...

I know in my bosch powertools there is only a high/ low protection and temp protection on the pack voltage, not the cells, even no balancing. But they die very fast too... when used oftenly. I can't understand it, yeah money...They didn't last more then 3 years under heavy use...

Sure they are no lipo, but they can do real damage and start fires under the right circumstances.


So if you want maximum lifespan you need to be able to set those parameters yourself and do wisely.

What you can do is take a cheap bms with balance function and ones in a while you do a balancing charge till balanced.
That's what they recommend with bicycle batteries.

Is it safe to use a cheap bms? Don't know, a faulty poor constructed BMS will harm your battery as well..
I had several broken due moisture getting in to the battery, so maybe my fault.

Those liions don't like to sit on 4.2V for long periods. So if they don't need to be charged don't charge them fully. Don't run them load higher then 1C continuous, they will heat up, and if your casing is not well ventilated it can't get away.
They don't like the heat.

I recommend you to read some articles on battery university.

This is a good one to start with:
https://batteryuniversity.com/index.php/learn/article/bu_808b_what_causes_li_ion_to_die


Set yourself some specifications first and work from there. And keep posting pictures.
Edited 2020-08-30 07:19 by nickskethisniks
 
BenandAmber
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Joined: 16/02/2019
Location: United States
Posts: 961
Posted: 09:27pm 30 Aug 2020
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Thanks for the info  Revlac and Nicks!!

All the batteries are the same color and same writing on them

The dell laptops rate the life of the battery in them

All these batteries tested good or excellent before taking them out

Thay are still paired up three in a row


Me being scared of these batteries is a under statement

I store them in that box with paper in between and taped in that wood stove




Had to clean the dust and wood chips out off the first inverter

Its idle current is 0.29 on the 48 volt battery side

I am really happy with it

I still think their may be a advantage
to a taller and skinny toroid Transformer

One day I will test this theory
Edited 2020-08-31 09:06 by BenandAmber
be warned i am good parrot but Dumber than a box of rocks
 
Revlac

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Joined: 31/12/2016
Location: Australia
Posts: 1024
Posted: 12:23am 31 Aug 2020
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That's well said Nick,  I have also seen many batteries ruined from faulty BMS, when they get a little damp they can drain some cells flat, really bad if someone tries to use a battery and doing so, drives the flat one into reverse.

Ben, Those laptop battery cells are the same as I have, some laptops would likely have used the batteries more than others, capacity wont be identical but perhaps close enough.
Will add a picture later.
Cheers Aaron
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BenandAmber
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Joined: 16/02/2019
Location: United States
Posts: 961
Posted: 07:39am 31 Aug 2020
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I bet I am the first person to find a use for a power Jack manual


My experimental Transformer primary wires

I put the current toroid there so when I solder leads on the secondary I won't forget to slide it on



I am going to have to put hood scoops on both sides the tranny is a little to be
Edited 2020-08-31 17:44 by BenandAmber
be warned i am good parrot but Dumber than a box of rocks
 
Revlac

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Location: Australia
Posts: 1024
Posted: 12:07pm 31 Aug 2020
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This is a set of 10, there would be 13 sets like this, I did them this way so I could stack them up depending on how many are available.
They should have wire strip spot welded joining them together, I soldered copper wire on to all of them and that apparently is a bad thing to do, I'm a dumb arse and Didn't know at the time, after doing this on over 2000 cells its never being any problem.

About a BMS, I have a bit of a dislike for the ones that cant be user configured to suit the type of batteries to be used.
I think you will need to find a suitably one because that will be a small bank to start with and I guess battery voltage will change rather quickly and get out of hand, were as a large bank like the one I have It could go for a week or 3 before things start to get out of hand.

Over the time I have run my setup I have only had 2 cells fail, over time I could see one pack of 100p the voltage was getting lower over 2-3 weeks until I give that lot a boost to bring them back up.
The first one was removed as soon as it was found due to a slightly higher temperature than the rest, the second one I left it in the pack for at least 3 months and no change, decided its time to remove it, removed the set of 10 to find 5 of them just slightly worm, separated them let them sit and the good ones cool and the bad cell was getting hotter and voltage dropping off, so the rest of the cells help keep the temp from running away on that cell, that's probably why all the battery packs I'v seen, the cells are packet tight together and work like a heatsink.

Now, for me this reveals a problem with using a not so smart BMS I believe it would hide the voltage drop on that pack and no one would know there is a problem there.

For large single cell battery bank 16s 1P this would not be a problem.

Now if there Is a BMS that can be user configured for the cell voltage required and if it could read the amount of power going in and out of the cells and do a comparison, this would be great, then the user can see there is a problem and perhaps fix it.

Also it is worth building a fireproof box to put them batteries in and they can go crazy without damage to anything els.

I have been really brutal with a few of these batteries from notebooks and never had any fire out of them yet, cant say the same for nickel iron or a few others, had a serious meltdown with them just on a light trickle charge.
That's all for now.
Cheers Aaron
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nickskethisniks
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Joined: 17/10/2017
Location: Belgium
Posts: 458
Posted: 01:02pm 31 Aug 2020
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I can only agree with you revlac, if you have tested them all, there is no reason not starting the build of the powerpack.

What you can do, is do a capacity test on each of the cells, then you can arrange accordingly, don't know if you have the testing gear. Don't know if you have some materials, but an arduino nano with a mosfet and resistor can do the trick, a small lcd screen can do the monitoring.  I can write a simple program for you.
Or put them all in a container and let an un harmful  hand pick them out for you, let statistics do the work. :)

If you are not space restricted I can only advice you to use those cell holders, but they increase the costs. I glued them together in the past without issues, but you need to be careful with soldering, because plastic is melting easily, and lead can make shorts. They don't recommend you to do soldering on them, but never had a problem doing so. Just do it as fast as possible, there is no reason to cover all the sides with solder, just enough will do.

I'm currently doing a 14S40P for my lawn mower, started with 1 part 7S40P but I'm going to change the design. I will post some pictures later. Those are all new batteries, but not the same capacity.

And I'm also preparing to do a 16S80P 18650 lifepo4 battery, last 2 years I selected those cells from batteries I ruined...   . I charged them fully, and let them rest for more than 6 months to watch self discharge and test capacity.

I'm still not sure (how) to proceed or combine the cells, capacity ranges from 700-1200mAh so there are huge differences.  First idea was to spread all sort of capacities over the "bricks".
 
BenandAmber
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Joined: 16/02/2019
Location: United States
Posts: 961
Posted: 06:12pm 31 Aug 2020
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Thanks guys I appreciate the wisdom

I need a small battery to test very small loads on inverters

I can't lug lead acid around anymore

I built a large power supply

I am wounding if there is a way i can use the batt pack and it together

I will try to up load pics later
be warned i am good parrot but Dumber than a box of rocks
 
BenandAmber
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Joined: 16/02/2019
Location: United States
Posts: 961
Posted: 06:21pm 31 Aug 2020
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This is that power supply I made no box yet

It can be wired for 120 or 240 volts it can put out 40 or 50 amps on 240

I have a little adjustable turn off board
for it also to use it as battery charger

It breaks one side of circuit on the high side

Here it is powering the experimental tranny in the power Jack



I have to build a good choke idle current is over two and a half amps
Edited 2020-09-01 13:25 by BenandAmber
be warned i am good parrot but Dumber than a box of rocks
 
Revlac

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Joined: 31/12/2016
Location: Australia
Posts: 1024
Posted: 10:12am 02 Sep 2020
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Nick, Your first idea (spreading the capacities over the brick) is the one go with, I have tried adding more cells on a brick that had less capacity and it was a lot of cells, over size and bulky compared to others, we work with what we have.


Ben, those cells will be ok to test the inverter with, I did mine the same way, just for a test run with a light or fan, thats all it needed.
You should still use a fuse or breaker, some sort of safety just in case there is a short.
The cells could be stacked in a way that make it nice and portable, I have seen some 48v E-Bike batteries, looks neat enough.

If you need the power supply hooked up to do testing the voltage should be close to the battery voltage, it may sage a bit under load, remember to disconnect it strait after use so the battery does not get overcharged.
I sure you will get it working the way you want for a test rig.
Cheers Aaron
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BenandAmber
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Joined: 16/02/2019
Location: United States
Posts: 961
Posted: 06:54am 05 Sep 2020
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Revlac thanks for safety tip and voltage of the power supply

I have gotten so much more than incredible advice and guidance

Bringing back a child like wonder is lots of fun and it's not illegal even though it is very habit forming

I have lost lots of time when tinkering with electronics and some tiny parts but definitely not many years or never lost anything as big as bright orange semi attached to a bright orange trailer

You guys blow my mind in a good way thanks!!
be warned i am good parrot but Dumber than a box of rocks
 
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