Can I pre-charge before a top balance with my hybrid inverter?

[Skypower]

I crimp and solder. After crimping I tag the open end with solder because the adhesive lined heat shrink doesn’t seal that part well. I also fold the wire to help fill the terminal. Some MC4 crimpers have a good small crimp opening that does really well on non insulated. I turn the jaws around so that the opening I’m using is closer to the hinge. I also like these terminals(Amazon)because they’re not copper but actually brass that’s harder and doesn’t mush under the nut,(also harder to crimp. I don’t use the pink shrink that’s on them.

 

[Ampster]

Do people usually solder ring terminals on the end of their BMS wires or simply crimp?

I just crimp. I sometimes fold the wires that are really thin. I also use shrink tubing and it makes a nice spot for a numerical label.

 

[chrisski]

After assembling three BMSs, I feel it doesn’t matter whether you use a good crimp or good soldering, or even both. The current is minuscule.

What I would change, is I would drill and tap the bus bars for these BMS leads. When I put my ring terminals on the studs and tightened, the ring terminals lined to spin.

 

[Devo1982]

Final question (today)... Is it worth me putting all my new cells in parallel overnight to let them "naturally" balance a bit? Or should I go ahead and series charge them tomorrow? TIA

 

[Ampster]

What I would change, is I would drill and tap the bus bars for these BMS leads.........

Yes, I have done that also.

 

[Robbert]

Final question (today)... Is it worth me putting all my new cells in parallel overnight to let them "naturally" balance a bit? Or should I go ahead and series charge them tomorrow? TIA

Parallel over night with a low SOC, doesn't make a difference.
Just put the pack in series, charge and after that a regular top balance in parallel. That is the fastest way.

 

[Devo1982]

Okay, so it's all hooked up and currently charging at about 30a on my hybrid inverter. Stupid question but how will I know when one of the cells hits upper voltage limit and BMS shuts off? Because charging current will drop to zero?

 

[Devo1982]

 

[Devo1982]

After a few hours at 30amps

 

[Skypower]

Okay, so it's all hooked up and currently charging at about 30a on my hybrid inverter. Stupid question but how will I know when one of the cells hits upper voltage limit and BMS shuts off? Because charging current will drop to zero?

Yes the bms should disconnect the charge MOS and leave a message in status information of the Daly. I like to be there and watch the first time, I don’t trust a new bms to do what it should. Did you review the defaults settings? The problem you may incur is when the charge stops (bms or charger) that bms may also stop balancing. Daly only balances on charge AND above balance active/start setting(3.4?) Hopefully you don’t trigger a high cell before you reach balance start and once you do, lower the charge current just enough to keep the balance active so that you can make slow progress to end of charge voltage in your inverter/charger. If you can’t progress, you can try again with a more powerful auxiliary balancer like a Heltec. Only one balancer should be on at time so turn the Daly’s off. This will speed up the fine balance. Once the pack is balanced your charge should never end because it relies on a trigger of a bms safety, but because of your end of charge setting. 27.5 to 28 volts is a good normal day to day end of charge voltage and doesn’t stress the cells. You gain very little going higher.

 

[Robbert]

After a few hours at 30ampsView attachment 145135

Looking good. The bms should disconnect charging if one cell reach high voltage. After that you can disassemble the pack, put it in parallel and do the final top balance. Depending on the difference in SOC, that still can take a day. But than you have a perfectly balanced pack.

 

[Skypower]

What Robbert said?

 

[Devo1982]

Thanks for the comments and kind words. One last question I do have is what are the scenarios where you would bottom balance rather than top balance please?

 

[Devo1982]

So last night my batteries were happily charging at 30amps. Then we had a power cut from 10pm to 4am, so they were actually put into use. Now, this morning they won't charge above 17amps, even though the inverter is set to 40! Any reason why?

None of the batteries are anywhere close to my 3.6v protection limit.

 

[Devo1982]

Cell 2 ran away earlier and triggered high voltage disconnect. But look at the other cells! They're way behind

 

[Devo1982]

Update - I've now got all my batteries configured in parallel doing a top balance using a desktop psu at 3.6v. Let's see how they perform once they are all balanced and back in series with my BMS.

 

[Skypower]

Looks normal for first trip near the top. If possible use some good wire about #8 to speed it up, the test leads the that comes with most power supplies are inadequate. Also connect to the battery from opposite ends. So that no battery has a shorter path.
It still could take a few days depending on the power supply.

 

[Devo1982]

Looks normal for first trip near the top. If possible use some good wire about #8 to speed it up, the test leads the that comes with most power supplies are inadequate. Also connect to the battery from opposite ends. So that no battery has a shorter path.
It still could take a few days depending on the power supply.

I'm having to top balance them in two groups of four cells as I only have eight busbars. Not ideal, I know but I'm hoping the end result will be acceptable.

 

[Devo1982]

They're all back in series and in action. Looking okay?

 

[Robbert]

Looking very good!