Another UK member

zag2me

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Joined
Sep 11, 2017
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114
Hi all, the name is zag.

I've recently added solar to my camper van(charge controller and leisure battery) and house(via micro inverters) and looking to take things to the next level with battery storage.

I also work in IT where we have a number of older bits of IT equipment recycled so I may have access to some batteries available to build with.
 
Welcome!
 
So my n00b question is...

Now I have started collecting batteries, whats the best device to measure each batteries total capacity?
 
That question is asked often, however there is no definitive answer. Depends on your definition of "best" and the general circumstances like number of cells, budget and so on.

If you only have a few cells then you can use anything, even something like a charger from SkyRC's IMAX B6 series which only discharge one cell at a time. Especially useful if you have one of them already, it would be a start.
If you have many cells to test howver then this isn't really suitable. Then the Opus BT-C3100 is a cheap solution for four cells at a time. The slightly more expensive solution for four cells would be the SkyRC MC3000 for example. If four still isn't enough you can get multiple ones of either of them.
I think one of the more expensive XTAR chargers for four cells has a discharge function as well, I don't know the name from the top of my head though. I think it is more expensive than the Opus but cheaper than the SkyRC.

All of the named devices can also charge the cells of course. If you want to go big and process many cells you want even more capacity to charge and discharger bigger amounts of cells at the same time. Instead of doubling the amount of devices you could build your own charging array with TP4056 modules and 18650 holders.

If four per device and multiple devices is not what you want then you probably have to build a device yourself. There are videos from the user mrconstantin who is doing something like this right now: http://secondlifestorage.com/t-64-128-cells-DIY-Multi-Battery-Tester-Charger-Discharger
 
Thanks, this site could really do with a getting started thread with an equipment list ;)

Went with the Opus BT-C3100 myself.
 
It wouldn't be a very extensive list though but I will think about putting together a little something.
 
Peter have a rather large list with all prices as soo. Mine is not as detailed but yes you can check that out.. Beware of that we talk about 100s or even 1000s of dollars for some of us :)
 
It begins....


image_kxozwj.jpg
 
So now I have my first set of batteries sorted. What is the process of testing them?

I have the Opus BT-c3100

Do I do a quick test?
Do I do a full charge and refresh?
What rate should I set it to?
What is a "good cell"?
What is a "bad cell" that needs chucking?


image_cnxmic.jpg
 
You check their voltage first and separate them into two groups, low voltage and normal voltage. Low voltage is everything from 0V to ~2.5V, everything above is considered normal. I don't know if or where the Opus makes the cut between chargable and not chargeable cells. Most charger reject a low voltage cell if it is under a certain voltage.

Low voltage:
Charge with a small current. The lower the voltage the lower the current. If at 1V or below then 10mA is plenty. Don't know if the Opus can do that, you can use any CC/CV power supply for that. With the voltage going up you can also adjust the current to make the process faster. At 1.5V you can go up to maybe 50mA, closer to 2V you can go for 100mA. There are no definitive rules for this, it is a matter of the right feeling and most people, me included, are probably overly cautious.
You let the cell charge until 3V or so, above 2V you can raise the current to 200 or 300mA to make it faster. After that the cell goes over to the other group.

Normal voltage:
Charge the cell at 1A. Check its temperature, it shouldn't get warm. Once charged, discharge it at 1A. Check temperature again, it shouldn't get warm. Or hot, better say hot. If you don't have a infrared thermometer you can just touch the cells. If they feel warm they are above your bodies temperature. That's ok. If they feel hot they are way above your bodies temperature and that is too much -> bad cell.
When the discharge is fnished and the cell didn't get hot you can write down its capacity. If it is really low you will probably chuck them away. You have to find find your own thresholds there. I binned every cell under 1000~1100mAh. I kept every cell between 1100 and 1500 for smaller projects and testing. And at 1500 or above I sorted them into groups like 1500-1700, 1701-1900, 1901-2100, above 2100. What is suitable for you depends on the results you get und what you want to achieve.
You then charge the cell again and let it rest for some time. Check the voltage after a couple of days or weeks to see if the cell kept its voltage. Everything above 4.1V is fine, everything above 4.0V is ok. Below 4.0V isn't really.

Repeat until out of cells :)
 
With opus run discharge test mode. If to low voltage bump charge them over like 1.5V as DarkRaven said.
 
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