Installing a battery meter in the pack

[Luis Medina]

Hi. Do I meet to disconect the positive and negative wires in the pack from the bms in order to open the wires and solder the aditional wires of the meter, or I can just open the wires and solder without disconecting . Is it safe ?

Is there an option to solder on the bms ? What is the best way ? To solder on the bms, or to solder on the positive and negative output wires ?

Thank you

 

[TPEHAK]

You can solder it to the charging wires near the charging connector. I guess those charging wires should have a small fuse somewhere near the BMS so you do not need an extra fuse for your device.

If it is easy to disconnect the battery power from those charging leads (disconnecting the BMS or disconnecting the fuse for instance) before soldering then do so just to prevent accidental shorting the wires during soldering process.

 

[Luis Medina]

Short circuit while soldering each wire would not occur because I would solder one, isolate it and them solder the other. I am just not aware if soldering a live wire is acceptable in electronics procedures. Is it ??? Please ?

 

[E-HP]

Short circuit while soldering each wire would not occur because I would solder one, isolate it and them solder the other. I am just not aware if soldering a live wire is acceptable in electronics procedures. Is it ??? Please ?

It’s not recommended, but what you’ve described presents little to no risk. By acceptable do you mean per the IEC, etc.?

 

[neptronix]

I prefer to use a pass through power meter because it's a lot less dangerous to hook up.

Some examples:
Google Search for turnigy power meter

 

[lnanek]

I've been using these super cheap ones:

https://a.aliexpress.com/_mO01bQF

Were terribly inaccurate on arrival, though:


And a big pain to calibrate. If I had to do it again I'd pay slightly more for ones with buttons for calibration and on/off.

 

[sternwake]

I feel totally blind if I do not know what my charging source is delivering. I have a plethora of inline meters to show amps and watts and count Ah and Wh. This little guy works pretty well, at upto 41.5v before it starts reading a little bit high in the voltage department.

Amazon.com

It does handle 8 amps continuous without getting hot.

I have one of the Meters shown in the OP and am not a fan. Clunky interface, weak audible overvoltage/undervoltage alarm, 0.1v resolution, and off by at least that much.

 

[lnanek]

Some of my chargers even need an oscilloscope to figure out what they are doing, I think, personally. I've definitely seen them rapidly varying voltage up and down repeatedly at times. Maybe measurement is more accurate if they stop briefly.

 

[E-HP]

How to transform a soldering question into a metering question in 5 easy steps:

1. Post the soldering question on ES
2. Mention the word “meter”
3. Allow the question to ferment overnight
4. Check responses after 24 hours
5. If the desired results are achieved, respond quickly before the question transforms to other topics (e.g. regen, LVC, flat prevention, etc.).

Step is important to prevent a runaway chain reaction, where the ES reactor goes critical.

Given the the OP is contemplating connecting the meter to either the discharge conductors or BMS, it would appear he may want to just monitor pack voltage, and not specifically charging voltage, so his question may have either fermented too long, or may require additional fermentation, which presents its own risks.

 

[lnanek]

If I was asking, I'd kind of appreciate people mentioning there's no need to solder at all if you use a pass through meter. I paid $15/each for mine and only had to deal with half an hour of shorting pads to get them calibrated. So much easier.

Soldering, well, I could do it, but I'd want a discharge test after and a thermal camera pic of the joint. Does he have the time and equipment for that? Why would you solder that anyway? Wouldn't a crimped butt splice and heat shrink be more reliable under vibration than a stiff solder joint?

 

[E-HP]

If I was asking, I'd kind of appreciate people mentioning there's no need to solder at all if you use a pass through meter. I paid $15/each for mine and only had to deal with half an hour of shorting pads to get them calibrated. So much easier.

Soldering, well, I could do it, but I'd want a discharge test after and a thermal camera pic of the joint. Does he have the time and equipment for that? Why would you solder that anyway? Wouldn't a crimped butt splice and heat shrink be more reliable under vibration than a stiff solder joint?

Clearly the OP should have checked responses last night before the thread started moving off topic.

 

[Luis Medina]

Hi.
Alot of information sprouted here. I am trying to keep it simple .
I asked a tecnitian in a nearby shop and he said
It is fine solder a live wire.

 

[99t4]

Yes, everyone here is trying to help you the best they can. This forum is a great thing isn't it?

 

[E-HP]

Hi.
Alot of information sprouted here. I am trying to keep it simple .
I asked a tecnitian in a nearby shop and he said
It is fine solder a live wire.

Yes, like I said. But he didn’t tell you that it’s not an acceptable practice per any standards organization. I’ve done a lot of house wiring stuff live, but it’s not recommended. You didn’t respond to my question to provide clarification. You forgot to spout that info.

 

[lnanek]

Not that I recommend soldering when crimping is faster, easier, has stronger pull resistance, stronger vibration resistance, and better water and corrosion resistance - but if I were soldering, I'd generally want to disconnect the wire first if possible so that it doesn't lose heat into the system while I'm trying to get it hot enough with the iron to melt the solder.

Heat is bad for the cell's longevity particularly if landing on a cell instead of a BMS board. That said, if there is a connector and it can be easily melted, some people leave them connected, or plug a dummy matching connector in, so the pins don't end up misaligned when the plastic of the connector softens.

Personally, I wouldn't touch the original pack in the first place. I have a bag full of connectors on pigtails and could easily crimp together a pass through plug with a T in the middle of each line via a reducing butt splice for the meter in a couple minutes.

 

[Luis Medina]

Thank you guys. I also switch off the electric when I do maintenance in doméstic electrical installations . But at some point of assembling a pack and installing a bms as an example one has to solder a live wire, like when connecting the final wires of the bms. I came to this conclusion. So it would be ok to solder the wires of the meter to the discharging wires of the battery pack.

If it’s not ok I will find out through experience and let you know!

 

[mrmojorising]

Wow so much over complication in this thread

Think of it this way, do you turn off a circuit when using a multimeter to test voltage? No, and that is basically all battery voltage meters are, with a tiny amount of current for the LED power. There will be negligible heat when soldering the tiny wires used for the meter too

Turning off is primarily for safety, and as you mentioned, as long as you insulate each live end when working, the chances of a short are reduced