Help me understand how this works Traxxas battery to balance connector to cell meter

[64Corvette]

Trying to understand how this works. I have an adapter that connects the Traxxas (in this case 3P) battery to a balance connector and then to a cell meter. I can cycle through the 3 cells and read the voltage for each cell, but don't understand how only two leads (in addition to the heavy guage power leads) from the Traxxas (smart?) connector can provide separate cell voltage information.

I get (or at least think I get) that the Traxxas battery has a processor that balances the charging voltage to each of the 3 cells going "in" but don't understand how a physical split into the 4 wires going to the cell meter can work going "out" seems like you would need wiring directly from the cells bypassing the processor to that connector.

Thanks

 

[WickedFog]

Trying to understand how this works. I have an adapter that connects the Traxxas (in this case 3P) battery to a balance connector and then to a cell meter. I can cycle through the 3 cells and read the voltage for each cell, but don't understand how only two leads (in addition to the heavy guage power leads) from the Traxxas (smart?) connector can provide separate cell voltage information.

I get (or at least think I get) that the Traxxas battery has a processor that balances the charging voltage to each of the 3 cells going "in" but don't understand how a physical split into the 4 wires going to the cell meter can work going "out" seems like you would need wiring directly from the cells bypassing the processor to that connector.

Thanks

The smart batteries use a digital signal to transmit data through a pcb that converts the analog data to digital. So it's like just a series of 1's and 0's coming out of the battery that is translated by another processor outside the battery. Standard LiPo batteries use individual wires going to each cell. What adaptor are you using?

 

[jojobeans]

The smart batteries use a digital signal to transmit data through a pcb that converts the analog data to digital. So it's like just a series of 1's and 0's coming out of the battery that is translated by another processor outside the battery. Standard LiPo batteries use individual wires going to each cell. What adaptor are you using?

Traxxas "smart" batteries don't have a circuit board like spectrum batteries. There's nothing actually smart about these batteries. They're just normal LiPo's. The balance plug is just built into the ID plug and wired as such. Which is why those adapters for other non-traxxas chargers are able to work.

While this isn't something id recommend the average hobbyist do, it does explain pretty well how the ID connector works.

 

[WickedFog]

Traxxas "smart" batteries don't have a circuit board like spectrum batteries. There's nothing actually smart about these batteries. They're just normal LiPo's. The balance plug is just built into the ID plug and wired as such. Which is why those adapters for other non-traxxas chargers are able to work.

While this isn't something id recommend the average hobbyist do, it does explain pretty well how the ID connector works.

That video is showing a pcb in there

The Traxxas ID plug is just the two discharge leads and a single lead for the ID stuff right? I don't have any Traxxas batteries, so just going off memory of pics of the connectors.

 

[jojobeans]

That video is showing pcb's in there
View attachment 253842

The Traxxas ID plug is just the two discharge leads and a single lead for the ID stuff right? I don't have any Traxxas batteries, so just going off memory of pics of the connectors.

that’s weird… it’s not present in this video and the ones I’ve opened up out of curiosity didn’t have that. Then again I’ve only ever owned 2s and 3s Traxxas packs. I wonder if they’re using a PCB as a more solid solder tab to make repairs and/or manufacturing easier for larger packs?

Regardless, doesn’t change what I said. The balancing is handled just like any other LiPo and doesn’t rely on a controller built into the battery like Spektrum batteries do. Balancing leads are just baked into the connector.

2s packs have one balancing lead, 3s packs have 2 and so on. It just shares one of the balancing leads with the discharge lead. If that makes sense? It’s difficult to explain in words without having one directly in front of me with the solder tabs exposed

 

[WickedFog]

that’s weird… it’s not present in this video and the ones I’ve opened up out of curiosity didn’t have that. Then again I’ve only ever owned 2s and 3s Traxxas packs. I wonder if they’re using a PCB as a more solid solder tab to make repairs and/or manufacturing easier for larger packs?

Regardless, doesn’t change what I said. The balancing is handled just like any other LiPo and doesn’t rely on a controller built into the battery like Spektrum batteries do. Balancing leads are just baked into the connector.

2s packs have one balancing lead, 3s packs have 2 and so on. It just shares one of the balancing leads with the discharge lead. If that makes sense? It’s difficult to explain in words without having one directly in front of me with the solder tabs exposed

Yeah, the balance leads all share a common ground anyway. So that makes sense. I didn't realize the traxxas plugs had multiple balance leads built into them. I thought all the different sized packs still used the single connector in the middle like Gens does. Interesting.

 

[jojobeans]

Yeah, the balance leads all share a common ground anyway. So that makes sense. I didn't realize the traxxas plugs had multiple balance leads built into them. I thought all the different sized packs still used the single connector in the middle like Gens does. Interesting.

It’s an interesting way to do it for sure. Not the black magic it seems like… what is back magic, is how the ID charger knows the capacity. Unless it’s just looking at resistance and doing a calculation and comparing it to the closest rated capacity stored in its memory? Maybe that’s what the PCB was for on that 4s pack?

 

[WickedFog]

It’s an interesting way to do it for sure. Not the black magic it seems like… what is back magic, is how the ID charger knows the capacity. Unless it’s just looking at resistance and doing a calculation and comparing it to the closest rated capacity stored in its memory? Maybe that’s what the PCB was for on that 4s pack?

If that's how Traxxas does it, that's kinda scary. I'd have to tear into one to see.

If that pcb in the battery in the first vid isn't part of the smart crap, then it's likely to protect the user from over charging/discharging the pack. There are a lot of battery packs that have that built in.

 

[jojobeans]

If that's how Traxxas does it, that's kinda scary. I'd have to tear into one to see.

If that pcb in the battery in the first vid isn't part of the smart crap, then it's likely to protect the user from over charging/discharging the pack. There are a lot of battery packs that have that built in.

I just did a quick google search. Looks like they have an RFID chip embedded in the connector itself, which communicates to the charger information like capacity and whether it's a LiPo or a NiMh. Makes sense now why they don't sell the battery connectors, but will sell the speed controller side of the connector.

 

[64Corvette]

After seeing that video with the broken balance wires, I injected some potting/encapsulating epoxy using a fine tip mixing nozzle. Took about 6-7 ml per battery before it started to overflow so I am thinking that will do a good job of supporting the leads at their attachment points and where they exit the pack. Pretty much rules out any solder repair in the future but I would not attempt that anyway.

https://mgchemicals.com/downloads/tds/tds-832hd-2parts.pdf