balancing strategies as they relate to BMS

[John Frum]

Wouldn’t that be 2’ to the battery and 2’ back?

The battery is 4 feet wide.
The terminals on the charge source are ~0 feet wide.
that is 8 feet round trip minimum.

 

[MisterSandals]

The battery is 4 feet wide.
The terminals on the charge source are ~0 feet wide.
that is 8 feet round trip minimum.

Right, but if the charge source is at the midpoint (as stated), it’s 2’ to each end.
2’ wire to +, 2’ wire back from -.

 

[ArthurEld]

I have no problem with buying a 48V power supply or charger.

 

[John Frum]

Right, but if the charge source is at the midpoint (as stated), it’s 2’ to each end.
2’ wire to +, 2’ wire back from -.

4 feet of wire plus 4 feet of busbar.

 

[John Frum]

I have no problem with buying a 48V power supply or charger.

I thought you already had one.
I suggested that we use that already.

 

[John Frum]

To get a configurable 48 volt charger you basically have to get an inverter/charger.
I'll bet that sounds familiar.

 

[ArthurEld]

I have a 12A 48v power supply

 

[MisterSandals]

plus 4 feet of busbar.

Really? I have never heard of the length of the “battery” counted as part of the round trip. I am not saying it shouldn’t, just have not heard that nor considered it.

 

[ArthurEld]

I have a 12A 48v power supply

It is 0V-60V 0A-12A

 

[John Frum]

It is 0V-60V 0A-12A

That could work

 

[John Frum]

Really? I have never heard of the length of the “battery” counted as part of the round trip. I am not saying it shouldn’t, just have not heard that nor considered it.

I'm not sure either.

 

[Craig]

The psu upper limit is 3.8 volts.
The psu upper limit on amperage is 120 amps.

On the first pass the cells will be half full ~3.2 volts.
After the discharge test they will be empty ~2.5 volts.
I suggested we do the heavy lifting with the 48 volt charger but have not got buy in yet.
If you need more detail I can provide it, probably tomorrow.

OK I was not realizing you didn't have 48v charger. Regardless once the cells get fullish you won't be having the full Amp draw, to suck the volts down. So I wouldn't worry about having those massive cables. But they won't hurt anything either. I do think using the BMS to cut of charging of individual cells is a neat hack though.

 

[Craig]

Now that we have a 48v psu why are we not just pinging the whole pack up until the first high cell reaches 3.6 or whatever then manually charging the rest to 3.6 or whatever

 

[ArthurEld]

Now that we have a 48v psu why are we not just pinging the whole pack up until the first high cell reaches 3.6 or whatever then manually charging the rest to 3.6 or whatever

I plan to charge the cells connected parallel most of the way with the 120A power supply.
Then I would like to just finish charging one cell so I won't mess up 16.
SmoothJoey is trying to figure out a way to connect the 16s BMS so that it will monitor the one cell I am charging. He also wants the BMS to shut off the power supply if the cell gets over charged.

 

[John Frum]

I plan to charge the cells connected parallel most of the way with the 120A power supply.
Then I would like to just finish charging one cell so I won't mess up 16.
SmoothJoey is trying to figure out a way to connect the 16s BMS so that it will monitor the one cell I am charging. He also wants the BMS to shut off the power supply if the cell gets over charged.

Actually I would really like the bms to disconnect the charge source so that all the cells get a very consistent charge.
I figure its more important to get them charged consistenly then the actual voltage or SOC.

 

[Craig]

I guess I am missing something seems to me you are making it more complicated than necessary. Why not put them all in parallel and set PSU to 3.65 and walk away for 2 days. Then break them apart let all cells settle for a day or more and see where you are at.

 

[John Frum]

I guess I am missing something seems to me you are making it more complicated than necessary. Why not put them all in parallel and set PSU to 3.65 and walk away for 2 days. Then break them apart let all cells settle for a day or more and see where you are at.

That is the approximate plan.
I probably am over thinking the wire guage.

 

[Gazoo]

I guess I am missing something seems to me you are making it more complicated than necessary. Why not put them all in parallel and set PSU to 3.65 and walk away for 2 days. Then break them apart let all cells settle for a day or more and see where you are at.

I recall having this discussion in another thread. It's because we were thinking charging the cells individually would be safer. I like your idea too but I think there might be some advantage to doing it in steps. I plan on hooking my cells in parallel then let them sit for a day or two. Then charge to 3.4 volts or so. Let them sit for a day. Then 3.5, let them sit for a day. Then finally 3.55 or 3.60.. I am not sure there is any advantage to doing it this way other than possibly more equalization between the cells.

Arthur and I both have the Riden RD6012 power supplies and that's the 60 volt 12 amp power supply he is referencing.. They also have a battery charger function but I don't know how well that works. So what I would do is use the 120 amp power supply to get the cells mostly charged in parallel. Then use the Riden to complete the charge. Just wanted to throw some thoughts in here and not saying any way is the right way because there are several ways to parallel top balance.

 

[toms]

If you want to use a BMS while parallel charging, just hook all the cell sensing wires together. The BMS isn’t smart enough to know if it’s hooked up to the same cell, and will disconnect at the high voltage setpoint.

 

[Gazoo]

If you want to use a BMS while parallel charging, just hook all the cell sensing wires together. The BMS isn’t smart enough to know if it’s hooked up to the same cell, and will disconnect at the high voltage setpoint.

Yeah but that's too easy...lol.