LED Voltmeter question

Alec_J

Alec_J

Member
Joined
Mar 16, 2017
Messages
89
I want to attach a little LED voltmeter to my packs to monitor the voltage of each pack. How do I wire it to each pack so it displays the pack voltage and not overall voltage?
 
That's a question I also have. So if anybody can answer it, thank you.
Edit: Ok I remember it now. Just wire the voltmeters in series between each battery pack. The difference in each is the pack's voltage. I'll try to draw a circuit to show you.
Edit 2 : Here it is.
Edit 3: Just in case you can't see it, I sent an attachment too. Seems the server is responding with 0 code.
 
There's really only 1 way to do it. And it only works on packs that are connected in serial.

So, you take your LED meter and connect Pos to Pos and Neg to Neg, and voila, you get your voltage.

Now, if you want to do that with parallel packs, it gets a bit complicated. Involves using diodes and I'm sure several other parts to make it work. It's not really feasible to do it this way as diodes lose voltage (they have a drop out voltage that must be overcome to work, and you lose that voltage to the diode).

So, only really works with serial packs. Which means that you have number of packs in serial that you need for your overall voltage. Like AveRage Joe and Pete (HBPowerwalls), they have 14 packs connected in series to give them their 48V setup.
 
Hey, Korishan. Do you have an idea why I can't upload any pictures? Seems like there's a problem.
 
You can't attach a picture "after" you've posted the comment, You have to create a new comment to add the picture to
If you add another comment fast enough, it'll append it to your previous comment (as long as someone hasn't responded first like i did)
 
@korishan. So I will have 14s20p. So when you say serial packs do you mean packs like mine or AveRage Joe's or do you mean a pack that is strictly serial?
 
Goddamn it then.

image_ftggnk.jpg


No wonder it didnt work. Thanks a lot Korishan :angel:

Here's the pic then. You have the parallel packs connected in series, with between them, the voltmeters.
And Alec_J, it only works in series, with parallel packs. As by wiring the batteries in parallel, it just becomes a bigger battery. You then wire it up in series with the voltmeters.
Edit: It's been uploaded now.
 
Pack: A complete set of cells that are connected in some arrangement to give a determined amount of voltage/capacity in output. This can be a all cells in series, all cells in parallel, or a combination thereof. If the pack is used by itself (say, on an electric bike), then we also call this a battery.
Bank: A batch of Packs that have been connected together either in series or parallel and usually charged by 1 charger and feeds only 1 inverter. Multiple packs make up a bank.

You can't reliably get the voltage of parallel packs. There's too much other stuff that needs to be done to accurately get the voltage. Doing this reduces the available voltage to the system.
If your packs are in series, then you can easily do this by connected the Neg wire of the meter to the Neg end of the pack, and the Pos wire of the meter to the Pos end of the pack. You can then have as many meters as there are packs and you will get an accurate reading of each pack. So as long as the meters have been calibrated (if you bought the kind that can be)

AveRage Joe has 14 Packs, and each pack has a voltmeter attached to it (this was shown in his latest video about the UPS and hooking it all up in the server rack) A voltmeter that has 1 wire per cell is basically doing sampling along the length and doing division to get the voltages of each cell. Neg lead to Neg series string. Pos lead to each pos lead in the string
+|===|- +|===|- +|===|-
|............||............||...........|
Pos3......Pos2.........Pos1.........Neg

Neg = 0V
Pos1 = 3.6V
Pos2 = 7.2V
Pos3 = 10.8V
(assuming each cell is 3.6V). It just does simple addition. This style is usually done at the cell level inside a pack, or a pack that has a set of cells connected in series.
 
Excuse the hijack :)
I have some with three wires, I know the red and black are + - what is the 3rd white wire for, I usually just combine it with the + ?
 
Wattsup: That White is usually for external power. So, you connect the black common to Neg, the Red Pos to the batter/pack, the White to a secondary source. They share the Black Neg common.
That's my understanding, at least. I could be wrong.
 
Nope you nailed it Korishan. You can use a separate power source to make sure the meter turns on, then use the VIN to measure the voltage of whatever your testing, you can tie them together if your powering it from the same thing you are measuring. Just make sure you run an extra black wire from the ground terminal if you want to prove stuff like a multimeter. Also these little 4 digit meters were less than $1 on eBay..the extra resolution is nice.
I'll do a quick video and upload it....gimme ten minutes and it'll be uploaded for ya.
Well done. Cells or packs in parallel should be st the same voltage or something is very wrong. Once you connect them in parallel, they balance themselves out to equal voltage potentials. Under load they may deviate a little due to internal resistance which is why you should match the cells in each pack by their IR prior to the build... in series, just wire up the meter to each packs +\- and make sure they are all at the same ground potential.

Video is up YouTube search "the combat engineer 18650" or click the link for my channel
 
Inverted 18650 said:
Nope you nailed it Korishan. You can use a separate power source to make sure the meter turns on, then use the VIN to measure the voltage of whatever your testing, you can tie them together if your powering it from the same thing you are measuring. Just make sure you run an extra black wire from the ground terminal if you want to prove stuff like a multimeter. Also these little 4 digit meters were less than $1 on eBay..the extra resolution is nice.
I'll do a quick video and upload it....gimme ten minutes and it'll be uploaded for ya.
Well done. Cells or packs in parallel should be st the same voltage or something is very wrong. Once you connect them in parallel, they balance themselves out to equal voltage potentials. Under load they may deviate a little due to internal resistance which is why you should match the cells in each pack by their IR prior to the build... in series, just wire up the meter to each packs +\- and make sure they are all at the same ground potential.

Video is up YouTube search "the combat engineer 18650" or click the link for my channel
Click to expand...



That video was a great help thanks! Can't wait to see more videos!
 
Inverted 18650 said:
Alec_J said:
That video was a great help thanks! Can't wait to see more videos!
Click to expand...

No worries brotha, also got your 'Hover Board BMS package' today. I'll start investigating the boards and see if I can find a way to use them in our projects and do so safely.

Cheers,

Chris
Click to expand...


Awesome! I'm happy they found you! Keep us updated with your experiments. I love reading your posts.
 
You must log in or register to reply here.
Back
Top