questions about 18650 batteries and they're management. ( RE: what ive learned)

The original post was pretty daft.

although i removed it from the first post but i have Posted it in a later reply, Unmodified, so you can understand which mistakes i made.

srnet:
Dont try that again please, for everyones safety.

You need a current limited AND voltage limited regime to charge lithium batteries.

I suggest you edit your first post, to remove the description of how you charged the batteries, it would be very easy for anyone following your advice to set fire to the batteries, workshop, house etc.

thank you for pointing this out, I almost forgot that even i took ideas from what people say in the forum.

Now to the actual question.
I have some tested and perfectly working set of lithium batteries. I am currently looking at a tp4056 MODULE ( they have dw01 and a few other protective measures on them). But given the fact that I have 9 batteries, How many of these modules do i need? They are pretty cheap, but even then..

Should I get 1 module for 1 battery? And then tie the 9 inputs/outputs together and power them ( the module input ) with a 5V 10A source?
Or
Should I keep all the batteries in parallel and Get 3 or 4 modules, basically enough modules to Charge the batteries fast enough and have enough current output to not trip protection measures?

I saw but did not reply to your other post because I have never used lithium ion cells and thus don't have any experience with them. I did not think your post was 'idiotic'.

To deal with your questions as best I can:

  1. No. Regardless of chemistry all the cells in a battery should be the same, that is, same type from the same manufacturer with the same history. Same batch too if possible but that's probably asking too much. Don't mix different cells in the same battery.

If space and weight are not a problem I suggest a 6 cell lead acid battery, maybe between 6 and 12Ah. Dead cheap, robust and easy to maintain. All you need is a 13V2 power supply to float across them and a buck converter for your 5V. Do that and you don't need any switching at all.

  1. Ideally every cell in a parallel arrangement should have a fuse as physically close to the cell as possible, this is to prevent a fire. Most types of battery can easily start a fire if shorted out, especially lithium batteries.

  2. Don't know.

  3. Don't know.

  4. Don't know.

Hope that helps a bit.

PerryBebbington:
I saw but did not reply to your other post because I have never used lithium ion cells and thus don't have any experience with them. I did not think your post was 'idiotic'.

I said i realized.. IF i came across a post such as mine, i would be unsure of what the OP wants to know.. basically that was a plea for diagnosis over the internet without any self diagnosis.. so yeah, realization.

PerryBebbington:
1.Don't mix different cells in the same battery.

2.If space and weight are not a problem I suggest a 6 cell lead acid battery, maybe between 6 and 12Ah. Dead cheap, robust and easy to maintain. All you need is a 13V2 power supply to float across them and a buck converter for your 5V. Do that and you don't need any switching at all.

  1. Ideally every cell in a parallel arrangement should have a fuse as physically close to the cell as possible, this is to prevent a fire. Most types of battery can easily start a fire if shorted out, especially lithium batteries.
  1. Thats the part that isnt making much sense to me... Why ? If its about the batteries falling below or going over the safe limits, then the other "good" cells in the Pack should prevent it, As i wrote before, say the bad cell has really low charge and gets drained really fast. so when it drops from 4.2 to 4.1, then charge is flowing in it so it shouldnt discharge to 3 V and so on.

2.Size and weight is just an eyesore, nothing more. But with anything and everything going on in the world, i would love to make do with the 13 cells i have now.. 9 actually , for this. I do have a 12v battery but i use it for odd jobs around the house..

  1. Its so hard to find correct fuses locally, and my country doesnt have sites like digikey and so on. Which is why i wanted to use limiting resistors. From an electrical standpoint, Wouldnt this be usable instead of a fuse? because i already know how much current i might draw, with headroom.
  1. Good question! AFAIK you risk that the bad batteries will drag down the good ones. I can't be more specific. This is one of those things I 'know' to be true, seems right but I am struggling with the specifics. Maybe there is a battery expert on here who will say something and we'll all learn something.

  2. Up to you, my recommendation is my recommendation, you have to decide what's best for you. I like lead acid batteries, they are cheap and easy to manage, no fancy battery management system needed.

  3. Can you find any fuses? Putting something in series with each cell is important because of the fire risk from a short circuit. If you can't get proper fuses can you get fuse wire or even thin stands of wire from cable? If you have to improvise fuses from thin wire stretched across 2 nails that would be better than no fuses. Check the cells can blow them. The trouble with resistors is you will lose voltage. Maybe low value low wattage resistors will also blow from a short across a cell. I guess you need to experiment.

  1. It is a bad idea to use salvaged lithium-based cells, PERIOD. It is a worse idea to mix bad cells with good.

  2. It is a bad idea to "charge overnight with a current limited power supply". That will eventually destroy the good ones.

  3. For your safety, you really need to read up on how to charge lithium based batteries. They can be extremely dangerous when mistreated, as you are doing.

kaseftamjid:
I have 9 salvaged 18650 batteries ( from different sources ). I connected all 9 of the batteries in parallel and left them to charge overnight with a current limited power supply for safety. And the whole pack shows 4.2V and no sign of any heating. Sweet!

Dont try that again please, for everyones safety.

You need a current limited AND voltage limited regime to charge lithium batteries.

I suggest you edit your first post, to remove the description of how you charged the batteries, it would be very easy for anyone following your advice to set fire to the batteries, workshop, house etc.

This is wrong. wrong as in it doesnt actually portray what i actually did and tries to over simplify things. And also wrong as in It would waste a bunch of power on the limiting resistors.

So I want to build An automated backup supply for my router and its ONU. I have 9 salvaged 18650 batteries ( from different sources, all tested multiple times to make sure that they wont explode). I checked the Voltage of each battery and made sure that they are not more than a few milivolts different and THEN connected the ones with nearly same voltage in parallel. The ones with greater than 300mV difference were set up with another dedicated charger. No makeshift chargers were used, If you are reading this with the same problem, stop. There are NO shortcuts in this realm. 

But now, this simple-looking project is starting to look like a nightmare. My original plans were simple. 1.solder 5 Ohm resistor with EACH battery to limit current to near 600~800mA.
2. Put the batteries in parallel (1s)
3. Connect the USB power bank circuit with the battery (It was intended for 6 cells 1s), Use a good quality current limited 10-watt USB wall adapter to power the circuit.
4. Connect a boost converter to the battery pack to get 12V For the ONU ( never uses more than 10 watts, let's say 1A at 12V)

5. Use an attiny13A (cheap  :confused:  ) to monitor the voltage of the battery pack so it doesn't go below 3 volts, for safety 3.1V. If it reaches a certain limit, Disconnect the batteries from the boost converter.
* This is so that the boost converter doesn't drain the batteries below the safe limit, the charger circuit already has protective measures on it*

6. Draw 5V for the router from the USB port of the Charging circuit, Draws less than 500mA so should be fine.

7. Put this whole thing in an NC config of a relay. ( meaning the circuit will be switched off ( except the charger) and the router & ONU will draw power from a different Adapter. Power Outage=Relay off NC= boost converter enabled. And when the power comes back = Relay on = different circuit )




Now for the problems i see and cant grasp. 

1.All of the cells are not from the same place, so given that im not drawing too much power, is it okay to connect them in parallel?
 I was thinking if a battery was losing charge faster then others, it would get charged/balanced with its falling voltage because not every cell is discharging at the same rate and some other cell has higher voltage with just a few mV difference.

2.Is it plausible to connect series resistor with the cells to limit current?

3.As i understand, The charging circuit previously used 6 cells in 1s config, So the charging time might be higher with 9 cells, but im okay with this. is it okay?

4.I cant find any suitable 1s BMS board with enough current rating for my needs, so i have to use a attiny, is this okay?

5.Another option is buying small 1 cell intended power bank circuits for all 9 cells and then Boosting voltage from The 5V 1A * 9 Outputs to 12V and tying all there USB input pins to 1 USB pin for charging. But this takes a BIG hit on the cost of the project. plus im not big on smd soldering.
Thanks, I hope this wasnt as idiotic as the previous one.