What is the best BM out there? No I am not trying to start a fight LOL

[Bob B]

@Dzl is probably correct that we are talking about different chargers ..... I was referring to using an AGM charger for the pack .... not for individual cells or for parallel balancing.

 

[Dzl]

@Dzl is probably correct that we are talking about different chargers ..... I was referring to using an AGM charger for the pack .... not for individual cells or for parallel balancing.

I think the problem is that there are two parallel convo's happening, one on top balancing and one on finding a lifepo4 charger, your comment is relevant to the latter, gazoo's comment is relevant to the former, and I believe Sherilyn and I have toes dipped in both sides of the discussion and there is also a bit of confusion over terms. I also suspect my attempt to clarify did not help clarify and contributed to further confusion

 

[Bob B]

I think the problem is that there are two parallel convo's happening, one on top balancing and one on finding a lifepo4 charger, your comment is relevant to the latter, gazoo's comment is relevant to the former, and I believe Sherilyn and I have toes dipped in both sides of the discussion and also may be misinterpreting a term or two. I also suspect my attempt to clarify did not help clarify and contributed to further confusion

Your comments will result in clarification in case anyone was misunderstanding the purpose of the charger being discussed .... and that is a good thing.

 

[Deleted member 9967]

I think you guys are not talking about the same thing.
Sherilyn, I still think you may not be clear on what people are generally referring to when they talk about 'manual top balancing', 'initial top balancing' or 'parallel balancing'. This involves putting your cells in parallel, charging with a CC/CV power supply until cells hit 3.65 (or 3.6, or 3.55, etc) and current tapers down to a predetermined cutoff point, at which point the pack is balanced.

You almost certainly cannot use your AGM charger for an initial top balance because it is most likely a 12v charger, and your cells in parallel are only charged to at most 3.65V. Adjustable CC/CV benchtop power supplies are commonly used for this process.

I believe you may be planning to skip this part of the process (a manual top balance) which is probably completely fine so long as you understand the caveats Craig and I mentioned earlier (namely you will be operating at reduced capacity for some number of days, weeks, or months until the BMS can bring your cells into balance). As Craig said if your priority is to get things setup ASAP, this is probably the way to go for your situation.

Understood.
Actually it is a 24 volt AGM charger.
I plan to charge them in series until about 3.4 volt per cell [I just check them with a multimeter after a short rest].
Or 27.2 for the battery itself.
Then when they are all about 3.4 per cell, I will put them in parallel for a few days until they are all equal in voltage.

So I am not confused really.
Just trying to reply to everyone commenting here is all.

Thanks for your concern though.

However if you see something wrong with what I just said then please point it out for myself and others reading this.
Thanks

 

[Deleted member 9967]

From everything I have noticed everyone is using bench top power supplies or single cell LifePo4 chargers. We top balance to 3.65 volts....right?

I don't know of anyone using an AGM charger to top balance. I don't know if it's possible. But if it is I would be extremely careful and overly cautious because you have no way to limit the voltage.

I am planning to top balance to 3.55 and may go up to 3.6 volts depending. I am going to connect my cells in parallel and let them sit for a day or two. Then charge in steps. I do not want to end up with a bloated cell due to overcharging and I figure charging in steps will help prevent that. Even though I have a power supply/charger I can't watch them like a hawk all the time but I will be watching them like a hawk when the cell voltage is near the end of charge....lol

I am thinking if I was in your shoes I would not top balance. Instead focus on a decent BMS and charger.

Yes, once near the top you HAVE to cut off the charger as it is imperative that the voltage does not go above 3.65 per cell. The overall voltage means absolutely NOTHING. It is per cell that you have to watch EXTREMELY carefully.
So when using an AGM charger you have to watch it ALL the time. Having OCD is a benefit here.
There is never a chance that the AGM charger will stop at the proper voltage or amperage for a Lifepo battery. So only if you are vigilant about such things should you even consider it.
AND THEN NEVER GO TO FULL CHARGE EVER.
It is simply not worth killing a cell for a fully charged battery.

If you have a proper Lifepo battery charger AND a BMS then go for a full charge right away. However if you are missing either or both, then no, don't even try a full charge. A dead cell is simply not worth it.
If it is a lithium battery and not a Lifepo you also risk thermal runaway. Nothing I say can describe it. So watch a video or two.
While Lifepo can be destroyed by over charging. At least they do not catch fire. The vent just opens up and you have a stinky house and your battery is dead.

Ok long way to say. Yes I will be careful and thanks.

 

[Deleted member 9967]

I think the problem is that there are two parallel convo's happening, one on top balancing and one on finding a lifepo4 charger, your comment is relevant to the latter, gazoo's comment is relevant to the former, and I believe Sherilyn and I have toes dipped in both sides of the discussion and there is also a bit of confusion over terms. I also suspect my attempt to clarify did not help clarify and contributed to further confusion

LOL yes I agree.
About the confusion, not your description I mean. You did well on that. ?

 

[Bob B]

I'm still a little confused .... are you planning to use the AGM charger to charge to 3.65V?

 

[Deleted member 9967]

I'm still a little confused .... are you planning to use the AGM charger to charge to 3.65V?

LOL I hope you are joking right?

 

[Bob B]

LOL I hope you are joking right?

It definitely isn't going to work .... it's just that in post 45 you were talking about using the AGM charger and watching the batteries very closely. Wanted to make sure that wasn't what you were intending .... sorry

What are you planning to use during the initial parallel balancing?

 

[Gazoo]

The vent just opens up and you have a stinky house and your battery is dead.

I have noticed a few bloated cells from overcharging but none of the cells vented. Which is kind of surprising.

I plan to charge them in series until about 3.4 volt per cell [I just check them with a multimeter after a short rest].
Or 27.2 for the battery itself.
Then when they are all about 3.4 per cell, I will put them in parallel for a few days until they are all equal in voltage.

I don't think that's a bad idea as long as you have connected the BMS. There would be no need to connect the batteries in parallel after charging in series to 3.4 volts per cell.

It will be interesting to know the difference of the cells voltages. Even if the cell voltages are equal the capacity of each cell might probably won't be. So I stand by my previous comment if you can't or don't want to parallel top balance. And that is connect the cells in series, let the BMS do the balancing, and call it done. You will still have lots of useable capacity. But do what you feel comfortable with of course while being careful. They are your cells.

If it is a lithium battery and not a Lifepo you also risk thermal runaway.

I have watched many videos concerning lithium thermal runaway. I have also watched videos of LifePo4 cells being tested for safety. The EVE specifications lists the safety standards for their cells as do the other manufacturers. I understand the safety differences between lithium and LifePo4. Personally I will not use lithium. Of course with laptop batteries and cell phone batteries we don't have a choice.

 

[Bob B]

It seems that it was me that has been confused .... I thought you were going to parallel balance your cells while you were waiting for your BMS. I thought you intended to use the AGM charger after you got your BMS .... sorry for whatever confusion I have caused.

 

[Deleted member 9967]

It definitely isn't going to work .... it's just that in post 45 you were talking about using the AGM charger and watching the batteries very closely. Wanted to make sure that wasn't what you were intending .... sorry

What are you planning to use during the initial parallel balancing?

This is a repeat from above that may help.

Actually it is a 24 volt AGM charger.
I plan to charge them in series until about 3.4 volt per cell [I just check them with a multimeter after a short rest].
Or 27.2 for the battery itself.
Then when they are all about 3.4 per cell, I will put them in parallel for a few days until they are all equal in voltage.

Just to add. All I am going to do for parallel balancing is simply wire [bus bars] them from series to parallel and let them sit there on the floor taking up space LOL.

 

[Deleted member 9967]

I have noticed a few bloated cells from overcharging but none of the cells vented. Which is kind of surprising.

I don't think that's a bad idea as long as you have connected the BMS. There would be no need to connect the batteries in parallel after charging in series to 3.4 volts per cell.

It will be interesting to know the difference of the cells voltages. Even if the cell voltages are equal the capacity of each cell might probably won't be. So I stand by my previous comment if you can't or don't want to parallel top balance. And that is connect the cells in series, let the BMS do the balancing, and call it done. You will still have lots of useable capacity. But do what you feel comfortable with of course while being careful. They are your cells.

I have watched many videos concerning lithium thermal runaway. I have also watched videos of LifePo4 cells being tested for safety. The EVE specifications lists the safety standards for their cells as do the other manufacturers. I understand the safety differences between lithium and LifePo4. Personally I will not use lithium. Of course with laptop batteries and cell phone batteries we don't have a choice.

I do not yet have a BSM. OR a charger for Lifepo.
I said I WILL parallel balance them many times now.
I have Eve batteries. ?

 

[Deleted member 9967]

It seems that it was me that has been confused .... I thought you were going to parallel balance your cells while you were waiting for your BMS. I thought you intended to use the AGM charger after you got your BMS .... sorry for whatever confusion I have caused.

No problem. I thought I spelled it out pretty sucinctly a couple of times now. Guess not enough though LOL.

 

[Dzl]

I do not yet have a BSM. OR a charger for Lifepo.
I said I WILL parallel balance them many times now.
I have Eve batteries. ?

Sherilyn, the disconnect here is that what you call parallel balancing and what is generally meant by parallel balancing are not the same thing. What you are suggesting doing is semi unconventional (probably not harmful so long as you are attentive with the initial charge, but also not a true balance). That is the source of much of this confusion.

What you are talking about is charging the cells in series to high SOC, and then letting the cells rest in parallel. This will move in the direction of balancing the cells, but as I understand it, this takes weeks or months to properly balance by letting the cells rest in parallel.

What is generally meant by parallel top balancing, is a method such as this:

1- Wire the cells in parallel
2- Set the power supply to 3.40V and 80% or less of the rated amperage (80% to not burn it out)
3- Turn on power supply and charge cells to 3.40V
4- When current has dropped to 0.0A at 3.40V turn off the power supply & set it to 3.50V
5- Turn on power supply and charge cells to 3.50V
6- When current has dropped to 0.0A at 3.50V turn off the power supply & set to 3.60V
7- Allow current to drop to 0.0A (or very close) at 3.60V
8- Done, pack is balanced.

Some people (Will for instance) condense steps 2-6 into a single step to simplify the process, but the result and method of balancing is essentially the same. The benefit of this method is speed and effectiveness. As has been mentioned, many people feel this can be skipped if you are okay with your pack being out of balance and operating at somewhat reduced capacity for weeks or months until your BMS can bring the pack in balance. How long this takes will depend on how powerful your BMS balancing is, and how closely your pack is matched/balanced to begin with. I suspect you would be okay skipping an initial top balance, or using your modified method which may not balance your pack but wouldn't hurt.

I hope maybe this clears up why there is continual misunderstanding in this thread on the issue of balancing.

But this whole balancing discussion has been a sidetrack from your original questions, have you come closer to making a decision on a BMS or do you have questions / concerns still about your options?

 

[Deleted member 9967]

Sherilyn, the disconnect here is that what you call parallel balancing and what is generally meant by parallel balancing are not the same thing. What you are suggesting doing is semi unconventional (probably not harmful so long as you are attentive with the initial charge, but also not a true balance). That is the source of much of this confusion.

What you are talking about is charging the cells in series to high SOC, and then letting the cells rest in parallel. This will move in the direction of balancing the cells, but as I understand it, this takes weeks or months to properly balance by letting the cells rest in parallel.

What is generally meant by parallel top balancing, is a method such as this:

Some people (Will for instance) condense steps 2-6 into a single step to simplify the process, but the result and method of balancing is essentially the same. The benefit of this method is speed and effectiveness. As has been mentioned, many people feel this can be skipped if you are okay with your pack being out of balance and operating at somewhat reduced capacity for weeks or months until your BMS can bring the pack in balance. How long this takes will depend on how powerful your BMS balancing is, and how closely your pack is matched/balanced to begin with. I suspect you would be okay skipping an initial top balance, or using your modified method which may not balance your pack but wouldn't hurt.

I hope maybe this clears up why there is continual misunderstanding in this thread on the issue of balancing.

But this whole balancing discussion has been a sidetrack from your original questions, have you come closer to making a decision on a BMS or do you have questions / concerns still about your options?

Thank you very much for this explanation. I can see now where the confusion is.
I suppose I should have mentioned this is an emergency situation as I do not have a BMS or a proper charger [it is for AGM now Lifepo].
It is temporary until I can s ave the money again after being screwed by the banks trying to buy the Chargery whole set [shunts and relays etc etc].
Anyhow, yes, I wish I have a proper charger and such. After reading since April I think I figured it out how to use a proper BMS and charger LOL ? And it only took me 3 months to do it too LOL. ?

 

[Bob B]

One thing I would caution about is the behavior of the cell voltage while charging them in series. I had read quite a bit about it before I did the initial charge on my pack but it still surprised me somewhat. I initially charged my cells at a low C rate. (only 10A with a 380 AH pack) The cells stayed at nearly the same voltage for a LONG part of the charge ... and then at the end the voltage came up VERY quickly even though I was charging at a low rate. It is also very difficult to determine with any accuracy what the starting SOC of the cells are.
I charged my 12V pack in series ... but with a Chargery BMS connected and a relay to disconnect in case of a cell high voltage.
With a 24V pack, it would be very easy to miss one cell that suddenly rises ahead of the others.
I have seen a few people post that they have puffed a cell when trying to top balance them.

Just want you to understand that charging with the cells in series without a BMS is VERY risky.
Last night when I recommended to start charging the pack while waiting on the BMS to arrive, I was thinking you were going to charge them in parallel .... Not your fault, but mine. That's what I get for watching a movie while participating in a thread.

Good luck with your project. Please keep us informed what BMS you choose and how things work out for you.

 

[Deleted member 9967]

One thing I would caution about is the behavior of the cell voltage while charging them in series. I had read quite a bit about it before I did the initial charge on my pack but it still surprised me somewhat. I initially charged my cells at a low C rate. (only 10A with a 380 AH pack) The cells stayed at nearly the same voltage for a LONG part of the charge ... and then at the end the voltage came up VERY quickly even though I was charging at a low rate. It is also very difficult to determine with any accuracy what the starting SOC of the cells are.
I charged my 12V pack in series ... but with a Chargery BMS connected and a relay to disconnect in case of a cell high voltage.
With a 24V pack, it would be very easy to miss one cell that suddenly rises ahead of the others.
I have seen a few people post that they have puffed a cell when trying to top balance them.

Just want you to understand that charging with the cells in series without a BMS is VERY risky.
Last night when I recommended to start charging the pack while waiting on the BMS to arrive, I was thinking you were going to charge them in parallel .... Not your fault, but mine. That's what I get for watching a movie while participating in a thread.

Good luck with your project. Please keep us informed what BMS you choose and how things work out for you.

I tried to order a BMS, charger, relays etc from Chargery, but Citibank screwed up the transaction for me.
So it is not like I am not getting one. I just do not have one right now is all.
The charger I have is a simple 24 volt AGM charger. Nothing fancy or adjustable at all on it.
Thanks for the heads up though. Much appreciated.

I do wonder though.
How often did you test the voltages?

Mine is an 8 amp charger if it means anything.

 

[Deleted member 9967]

But this whole balancing discussion has been a sidetrack from your original questions, have you come closer to making a decision on a BMS or do you have questions / concerns still about your options?

I think I have decided to still get the Chargery with all its extras still. I just do not know how I can do so is all. Maybe if someone living in Vancouver could order it for me and I just give them the money for it?
An idea anyhow.
And thanks for asking

 

[Bob B]

I tried to order a BMS, charger, relays etc from Chargery, but Citibank screwed up the transaction for me.
So it is not like I am not getting one. I just do not have one right now is all.
The charger I have is a simple 24 volt AGM charger. Nothing fancy or adjustable at all on it.
Thanks for the heads up though. Much appreciated.

I do wonder though.
How often did you test the voltages?

Mine is an 8 amp charger if it means anything.

I was tracking the AH I was putting into the battery with the Chargery and another stand alone monitor I have. I was assuming the batteries were 30-40% charged when I got them. Once I thought I was close to full charge, I was checking every 15 minutes or so. I would shut off the charge manually when I wasn't able to monitor it. I was probably a little too paranoid, but didn't want to take any chance I was going to ruin my battery while initially testing the BMS and getting the initial full charge on the battery.
Even though I had the BMS, I wasn't fully comfortable with it's functionality yet. I initially set the LVD at 3.4 just to make sure it would disconnect and so I would know I was starting up the knee. At that point, I set the Chargery to start balancing and reduced the charge current even more and kept reducing it further to 1-2 amps and allowed balancing to finish.
I had purchased a 0-30V 10A adjustable power supply. With it, I could parallel balance if I needed to .... but the pack was within 15mv by the time one cell reached 3.65V.
Overall, it took me several days with an abundance of caution to finish the initial charge/balance.