Charging Fogstar 460 for the first time

[Pausim]

This is what what my LiFePO4 battery manufacturer said about cell matching.

“Cell Matching Process:
When assembling multiple cells together either in series or in parallel we match and group cells together based on 10 consistencies;
1.Consistency of self discharge
2.Consistency of voltage
3.Consistency of inner impedance
4.Consistency of capacity
5. Consistency of cycle life
6. Consistency of platform
7.Consistency of constant current rate
8.Consistency of cell power control
9.Consistency of parallel module control
10. Consistency of finished battery control”

This is what they said about cell balancing.

“Balancing:
During charging the PCB board will provide up to 2A current through the lengthway circuit board which is lower voltage than the other lengthway boards.
Tests show that the cells are so precisely matched, batched together with high conformity and passive assembly design that the balancing function will remain inactive for most of the battery life.”

With 40 cylindrical cells in the battery I am very glad the manufacturer took care of all this for me so that I don’t have to worry about monitoring 40 voltages. The only thing I had to do was connect 2 wires to the 2 battery terminals. I know if I had access to detailed information I would be constantly monitoring it so it is a very good thing I don’t.

 

[Ditcha]

Would be interested to know if anyone has purchased a Roamer battery and had to cycle theirs to balance them or did they come supplied as they should have been?

 

[jezport]

I mentioned to you before, you can only balance at near full, at the top. The cell starts to saturate from 3.45v and above, that’s why balancing is done after reaches this level of charge. You can’t balance something with different quantities when they only partially full. You have to bring them up then the bms will bleed off the full ones so the empty ones charge and catch up. When all full they all balanced.

The balancing is only running off during the last 10mins of charge so only gets so.e balancing for a short period every charge. So I have to wonder if it would actually happen.

 

[Raul]

The balancing is only running off during the last 10mins of charge so only gets so.e balancing for a short period every charge. So I have to wonder if it would actually happen.

Correct, if you charging with very low amps close to full, then the balancing will last longer. If you hit the battery with 5-10 amps, the full cell will reach 3.65v very quick and disconnect. That’s why I said to you set absorb at 14.2v for 2hrs, and repeat.

 

[Ditcha]

The balancing is only running off during the last 10mins of charge so only gets so.e balancing for a short period every charge. So I have to wonder if it would actually happen.

That's the problem with the fogstar app, most other apps show you when and what cells are being balanced when balancing takes place. Unless that feature is available in the app and I haven't seen it.

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[jezport]

Correct, if you charging with very low amps close to full, then the balancing will last longer. If you hit the battery with 5-10 amps, the full cell will reach 3.65v very quick and disconnect. That’s why I said to you set absorb at 14.2v for 2hrs, and repeat.

I'm starting to understand now. I will wait until my Electroblok drops from 14.4 v to 13.6v and make sure my battery is discharged enough and turn charging on the battery back on it should valance for longer. Shouldn't the BMS and active balancer do this without my input?

 

[MichaelT]

My KS Energy seems to be just about balanced.

 

[jezport]

My KS Energy seems to be just about balanced.

View attachment 802295

What's it like on completion of charge?

 

[MichaelT]

What's it like on completion of charge?

That's complete for today got up to 95% now discharging.

 

[dpsuk999]

My 2 x 460ah Fogstar’s are always matched or within 0.001v:

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[Raul]

My 2 x 460ah Fogstar’s are always matched or within 0.001v:
View attachment 802306View attachment 802307

Nice, but when it reaches 14v and above, please give us a snip then.

 

[Raul]

My KS Energy seems to be just about balanced.

View attachment 802295

Give us a snip when battery is at 14v and above

 

[MichaelT]

Give us a snip when battery is at 14v and above

Will try and remember, we are moving on today so should get a charge.

 

[jezport]

A quick question.
As it seems the balance only goes out in the last few minutes of charge what's wrong with stopping charge at 99% when the cells are still balanced? We are told to store at between 30 and 80% charge anyway.

 

[BobJayne]

It's

There's no charge coming in. Doesn't look like it's finished charging

The charge coming in (or discharge going out) will only show if it's 1A or more, so it could actually be 0.9A but won't show in the app.

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[Raul]

A quick question.
As it seems the balance only goes out in the last few minutes of charge what's wrong with stopping charge at 99% when the cells are still balanced? We are told to store at between 30 and 80% charge anyway.

Thats when you observe them, at the top. The imbalance is due to slightly different state of charge, so you can have cells with almost identical voltage, but different charge level. When it goes up, to about 3.4 ish, this imbalance in SOC will show in voltage. The more charged cells will raise quicker, and the less charged cells will still absorb current.

The only downside of imbalance, it will restrict you to access its entire capacity. The pack capacity will be limited by the less charged cell.
When a top balance has been archived, the pack should stay in balance for a long time, if cells are matched, and the bms will correct minor imbalance.

Again the bottle analogy, you got 4 bottles, with identical size tops. Being the same will have the ability to take liquid in (charging) and out (discharging), at the same rate. This applies to balanced matched pack.
If one has a smaller intake ( higher resistance), they no longer matched. The smaller size will not fill up or empty at the same rate, and will be different in quantity ( SOC) to the others. Now you need to stop the flow as you fill, as the full ones are over spilling, while the small intake bottle still has space. This is when the balancing is triggered. You take some away from the very full one, while the empty fill up. You cant distribute the flow, its equal to all four, and all you can do is REDUCE the flow (charge), so you don't overwhelm the dull one, as you can only correct with a very small amount the over spill. Some chargers do have the ability to comunicate with the bms, and the bms will tell the charger to throttle down. If you don't, you have to do it manually, or other form of external control. This analogy applies to mismatched and unbalanced pack.
Also you could start a pack with four partially filled bottles, and on first fill up, it will show the difference in quantity ( imbalance), and as we continue charging, at the top the voltage will differ. This is the case i believe we have here.

 

[Langtoftlad]

Can I ask a numpty question - what real world difference does this make?

...or is it the equivalent of photographers "pixel peeping" ?

 

[olley]

Without the app we would all be carrying on without worrying, and likely would have years of trouble free use from the batteries.
I am going to fit and stop worrying about a few microvolts.

 

[Billy192]

Without the app we would all be carrying on without worrying, and likely would have years of trouble free use from the batteries.
I am going to fit and stop worrying about a few microvolts.

As I said the App is not the best. I will uninstall and get a smart shunt. I am sure it will last years with out issues.

 

[Billy192]

Just logged into the app



Lol mine is a 460 and my neighbour doesn’t have a van lol

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[Raul]

Can I ask a numpty question - what real world difference does this make?

...or is it the equivalent of photographers "pixel peeping" ?

I have explained it few times, imbalance = reduced capacity available, thats it.

 

[Al n Val]

Just logged into the app

View attachment 802586 View attachment 802587

Lol mine is a 460 and my neighbour doesn’t have a van lol

Your battery is eff’d

I’ll collect and dispose of it for you foc, just pm me with your address and leave the rest to me

yours obligingly

Al

 

[Billy192]

Your battery is eff’d

I’ll collect and dispose of it for you foc, just pm me with your address and leave the rest to me

yours obligingly

Al

Lol all good I re installed the app

 

[jezport]

On the fogstar UI it used to have a warning come up next to the clock for COV. This has been changed to Fully Charged. Charging is stopped by the BMS when 1 cell hits 3.65v.
It will also add to the COV list in the protection page on the app. According to Fogstar this is as it should be and is normal end to charge characteristics.

 

[Ditcha]

Can I ask a numpty question - what real world difference does this make?

...or is it the equivalent of photographers "pixel peeping" ?

I think it's mainly a case of mine is better than yours

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[Billy192]

I think it's mainly a case of mine is better than yours

I think you’ll find mine is

 

[Langtoftlad]

I have explained it few times, imbalance = reduced capacity available, thats it.

Thank you, I must have missed that.
Can you quantify how much capacity a Fogstar 460, as is being discussed, might be lost due to these unbalances... edited or even imbalances
1amp, 10amps or more...

 

[Raul]

Thank you, I must have missed that.
Can you quantify how much capacity a Fogstar 460, as is being discussed, might be lost due to these unbalances...
1amp, 10amps or more...

Depends from case to case, but if one cell hits 3.65v and the others are close or under 3.4v, it cluld be as much as 5-10% capacity. With a 100mv deviation probably well under 5%.
The true way of finding out is to measure the energy going in, from the poit that the balancing starts, to full balance.

 

[jezport]

Ive received a replacement from Fogstar which is charged 50% and they have pre-balanced it for me.
Im away for a week not with the van so will put it in on my return.

 

[jezport]

Depends from case to case, but if one cell hits 3.65v and the others are close or under 3.4v, it cluld be as much as 5-10% capacity. With a 100mv deviation probably well under 5%.
The true way of finding out is to measure the energy going in, from the poit that the balancing starts, to full balance.

Isn't that like having 4 different lead acid batteries connected together, under load they will balance somewhere between the 4?
Or does it not work like that with lifepo4 ?

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