12 volt or 24 volt?

pfromero

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Jan 30, 2017
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Hi all,

I've wired up 6 batteries like this, thinking it was simple to do. Now, I checked the leads with a small inexpensive multimeter, and it seems to be reading 10volts DC. I was intending to build 24 volt packs. Did I wire this wrong?

Please see picture.

Thanks!

Paul
 
That looks like one large 3.7v (nominal voltage) pack. Would be 4.2v at maximum charge.

What do others think?
 
Hi Bob thanks for replying, whatever it is I think I can combine these packs to get the 24 volt I need, but it would help to know whether the problem is with the gauge or with the wiring. The way I see it it's 7p by 28s. The other, positive, side looks exactly the same as far as wiring. By the way, I also have smaller wire ...about 12 gauge solid copper that I could maybe run lengthwise to get the voltage up. Thanks again Paul
 
Yes, it is indeed wired for 3.7/4.2 Voltage. You'll get LOTS of capacity, though :p But you won't be able to run much.

You need to do a combination of series and parallel setup. Usually the setup for 12V =4sXp (tho 3s sometimes is uses), 24V = 8sXp, 48V = 14sXp. The parallel add capacity and amperage draw ability. Whereas series adds voltage. (Did I get that right, guys?)

So you would put, say, 11 cells in parallel in each sub-batch. Then you connect each of the parallel sub-batches into series, of say 14 where each Neg to Pos, Neg to Pos, .... till you're done.

Check out daromer's video here for an example. Altho he is building a 48V system, the principle is





Just thought, what you could do is add them in series with your other packs, that would boost your voltage. So what you do is alternate which side is facing negative up (if they were laying down on the cell ends) and connect one pack Neg to another pack Pos, and so on. So yes, you are doing it correctly overall, just not usually done in that large of a parallel pack ;)
 
As usual, tons of great info. I was incorrect as you noted it is adding voltage when you do things in series not parallel.

So you're saying I need seven of these to get 24 volts? Cool! Thats exactly how many I have!

What I don't understand, is why my seven cells wired together (see pic)or 7s comma doesn't translate into 24 volts as is???
Paul
 
You've joined all the + poles together on the one side and all the - poles on the other. That's a massive parallel connected battery which adds the capacity of all cells but maintains the voltage. You need to do more research about parallel and series connections and understand the theory before trying to put it all into practice. There are plenty of examples on this forum.
 
Another thing you need to remember is that you base it off of the "nominal" voltage, not the max voltage. The nominal voltage for 18650 Li-Ion cells is 3.7v, and their maximum voltage is 4.2v. What that kinda means is that it will quickly drop from 4.2 (if max charged) down to about 3.9v, and then slowly go down to 3.7v on through to about 3.4v. At 3.4v it will again start to drop quickly.

Think of a reverse hour glass where the middle is fat and the ends are tiny. The fat part in the middle is your nominal voltage. From this large area you can loose, say, 1000 grains of sand (in this example) and it not be all that perceptible. However, on the ends where they are narrow, you loose a 1000 grains, it's very noticeable.

Now when you charge your pack, you should try not to charge above 4.1v, as this greatly increases the life span of the cells. And likewise, don't drain below 3.4v; again, drastically increasing life span.
 
pfromero said:
As usual, tons of great info. I was incorrect as you noted it is adding voltage when you do things in series not parallel.

So you're saying I need seven of these to get 24 volts? Cool! Thats exactly how many I have!

What I don't understand, is why my seven cells wired together (see pic)or 7s comma doesn't translate into 24 volts as is???
Paul

It appears that you did not wire anything in series.

Did you connect any POSITIVES to NEGATIVES?

What you built is a 196 P battery.

If you connect 7 of these together, IN SERIES, positive to negative, you will get a battery of 7S 196P at approximately 24v.

The only way a multimeter could show 10 volts is if you did a 3S configuration, and the cells are all discharged to about 3.3-3.4 volts.
So either the MM is wrong, you are reading it wrong, or your wiring is wrong.
Your wiring is definitely wrong if you wanted to achieve 7S 28 P
If you wanted to achieve 7S 196P then you are all good....except the 10 volt issue.


Sounds like you dont quite get the SERIES-PARALLEL thing yet....Figure it out with just a few cells first until you understand how to wire it. Because if you connect the wrong POS and NEG in a big battery like that, you will see some fireworks.
There are tons of pictures and videos online of how to wire it.
 
APD said:
Sounds like you dont quite get the SERIES-PARALLEL thing yet....Figure it out with just a few cells first until you understand how to wire it. Because if you connect the wrong POS and NEG in a big battery like that, you will see some fireworks.
There are tons of pictures and videos online of how to wire it.

Yep, I can concur. Big Badda Boom! if wrong ends connected. Especially with your size of parallel packs. Really Big Badda Boom! And hopefully, 'if' you make that mistake, it's no where near your house; because it would most likely not survive. :s
 
Sounds like some good info I appreciate it. I think I'll go ahead and wire these up 7 in series to get my 24 volts and call it a day.

Paul
 
I'll listen for the big badda boom :p


Seriously, gl on that. Let us know how it turns out. Whats the rest of the setup look like?
 
Please, don't go ahead with anything until you understand battery coonections thoroughly, or you could be making a big mistake and ? could be the result.
 
Hi again, it's apparent I made a mistake on the bus bars but I can still go in series and and get my 24 volts. However I need to look into the size of the cabling and capacity of the quick disconnects. Or possibly rewire each pack to bring it up to 24
Korishan: 7 battery packs are going into the deck box build pictured in the other Forum

Paul
 
pfromero said:
Hi again, it's apparent I made a mistake on the bus bars but I can still go in series and and get my 24 volts. However I need to look into the size of the cabling and capacity of the quick disconnects. Or possibly rewire each pack to bring it up to 24
Korishan: 7 battery packs are going into the deck box build pictured in the other Forum

Paul

Hold on. The photos just aren't clear enough to see what you did. I'm seeing seven rows of about 30cells across. Due to how your bus bars are arranged, with rows of 2, 3 and 2, I can only guess that you have 1s60p, 1s90p and 1s60p in series. That will never balance during charging and discharging, because the sets of parallel cells combine with different capacities. If that is the case, DO NOT puto those in series! Take it all apart and put it together correctly.

You can see better what you did. That's what I'm seeing, considering your reported voltage measurement.


Or maybe you have 3s60p, 2s60p and 2s60p in parallel. It's shocking that things didn't get very hot very quickly. Cell damage would be a concern.


60p=30p


In the case of 3s30p, 2s30p and 2s30p in parallel, the 3s would dump into the 2s on contact. Are your fuses any good? Are those even fuses? I'm scared.
 
skyfridge said:
pfromero said:
Hi again, it's apparent I made a mistake on the bus bars but I can still go in series and and get my 24 volts. However I need to look into the size of the cabling and capacity of the quick disconnects. Or possibly rewire each pack to bring it up to 24
Korishan: 7 battery packs are going into the deck box build pictured in the other Forum

Paul

Hold on. The photos just aren't clear enough to see what you did. I'm seeing seven rows of about 30cells across. Due to how your bus bars are arranged, with rows of 2, 3 and 2, I can only guess that you have 1s60p, 1s90p and 1s60p in series. That will never balance during charging and discharging, because the sets of parallel cells combine with different capacities. If that is the case, DO NOT puto those in series! Take it all apart and put it together correctly.

You can see better what you did. That's what I'm seeing, considering your reported voltage measurement.


Or maybe you have 3s60p, 2s60p and 2s60p in parallel. It's shocking that things didn't get very hot very quickly. Cell damage would be a concern.


60p=30p


In the case of 3s30p, 2s30p and 2s30p in parallel, the 3s would dump into the 2s on contact. Are your fuses any good? Are those even fuses? I'm scared.





I agree with other comments, you definitely want to understand series / parallel connections before you wire anything up.
I too am new to this but after asking questions and watching youtube vids I got my head around it.
Stay safe
 
This is not my image but it kind of explains what it is all about:

image_pchrdm.jpg


I also made this video:
 
I checked the meter manual. From the photo, it appearsthat the meter is set for DC voltage at the 50V range, so the meter is definitely reading about 10V, which would be 3S at~3.33VPC. 1S doesn't make sense, unless it's 10VPC. Is 10VPC even possible without flames?

I'm still trying to grasp how it could have been wired. It appears that the columns are wired together between the bus bars, but I can't see the orientation of individual cells.I'm guessing that things would get really hot with trying to connect 2s, 3s and 2s in parallel, especially in connecting 3s to 2s or even 1s to to 2s. 3.7V difference with little resistance other than internal resistance between them is going to get HOT! That's like shorting a cell, and I've seen that briefly. In shorting a cell the connection will get very hot, very quickly. Could that be mistaken for the heat of soldering? The problem should be immediately apparent while test fitting, so that doesn't make sense.

It doesn't make sense. It has to be 1s56p, 1s84p and 1s56p in series, with cells at low voltage. Trying to fully charged that pack likely would cook a good portion of thecells. Trying to discharge it likely would kill a good portion by overdischarging.
 
pfromero said:
Hi again, it's apparent I made a mistake on the bus bars but I can still go in series and and get my 24 volts. However I need to look into the size of the cabling and capacity of the quick disconnects. Or possibly rewire each pack to bring it up to 24
Korishan: 7 battery packs are going into the deck box build pictured in the other Forum

Paul

You need to post a clear pic of the OTHER SIDE of that battery pack....
Is it wired the same way as your first photo?
It appears that all your negatives are wired together onto the same bus bars

There is no way to have any SERIES connection with all your negatives connected together.
So there is no way you could also have 10 volts!


I suspect the the battery in your MM is going bad. Have you checked it?
And you need to confirm your plan:
Do you want each pack to be 24v?
...or do you want seven 3.7v packs?
 
Thank you all for taking the time to help me through the battery building process. I'm going to go straight to Walmart and get a new multi meter because that multi meter is very very old. Per your request, have attached a photo of the other side of a typical battery.I also have attached a photo of my intended setup. My goal is to have each battery pack connected in series per the photo and then thru larger cabling to the 24vDC inverter charger. Also, I intend to place larger #2 AWG gauge bus wires on the last two batteries connected and then 2 aut aluminum wire to the inverter via 175amp disconnects.(the rest have #7wire and 50 amp disconnects. All batteries have 20 AWG TCW "fuse" wirewhich blows at about 19 amps at 4 volts, if my memory serves me right.

Thanks All, Paul

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Have you replaced the Multimeter's battery?

They will read high when the battery is low.

...as for your pack: if that pack has all its positives on top, and all negatives on the bottom, it should read 3.7-4.2 volts.
 
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