Charging Batteries, their mAh/capacity.. trying to make sense of it all

[vicious_oli]

Hey everyone!

Figured I've got enough backlogged questions about batteries that I might as well throw them all in this post.

1. I have 2 NHX 8000mAh 3s batteries, and a gens-ace-r-spam Basher 8000mAh 3s, and the gens-ace-r-spam imars III charger. I always balance charge, which gets the capacity to 90%. If I want to "top off" the battery I have to change to normal charge, which will then get it to 99%.

Is that normal? Should I only balance charge to 90% and consider that a "full charge"?

2. The imars III lets me input a capacity cut-off when charging. I have it set to 8000mAh, since thats the max capacity of my current batteries, a video said that it would be safe to set it at like 8300mAh, to make sure the battery gets topped off.. but I don't want to risk it.

3. Now I just received an SMC DV Extreme Lipo, 6900mAh, 3s..

What kinda confuses me is the importance/difference between voltage and mAh capacity when charging a 3s battery. Shouldn't mAh not matter when charging, only volts? A small capacity battery, and a larger capacity battery should have the same limit in terms of volts per cell, or in total. Should I change the mAh cut off on my charger everytime I charge the SMC? Its not that I'm lazy and don't want to do it, i'm just afraid I might forget and cause some sort of fire.

Thanks!!

 

[jkflow]

OH boy.
Easiest to remember. Each cell needs to be at 3.85V for a storage level charge, roughly 30% capacity, Not 90%.

Set your charger to that cell level for storage. 90% will cause damage over time.

Do not use capacity limits, it's a pure safety measure. I have that maxed out.

Cell full = 4.2V 100%
Store 3.85V 30%
Empty 3.7 V (10%)
My percentage might be off, the voltage matters.
All you ever get is roughly 80 % of advertised capacity on good lipos.

Multiply by S to get the total lipo voltage.

 

[CrashBoom]

The only thing that really matters is cell voltage. Max cell voltage on a normal lipo is 4.2v regardless of capacity. Crank up the mah limiter or turn it off, that's probably causing the issue. It does little to nothing for safety.

Never charge a lipo with balance turned off.

 

[vicious_oli]

OH boy.
Easiest to remember. Each cell needs to be at 3.85V for a storage level charge, roughly 30% capacity, Not 90%.

Set your charger to that cell level for storage. 90% will cause damage over time.

Do not use capacity limits, it's a pure safety measure. I have that maxed out.

Cell full = 4.2V 100%
Store 3.85V 30%
Empty 3.7 V (10%)
My percentage might be off, the voltage matters.
All you ever get is roughly 80 % of advertised capacity on good lipos.

Multiply by S to get the total lipo voltage.

I don't have any questions regarding storage voltage/levels. My questions regard mostly balance charging and charging.

"Do not use capacity limits, its a pure safety measure"
That sounds so contradictory, like "don't use safety measures" but I think I DO understand what you mean, like its kind of meaningless.

The only thing that really matters is cell voltage. Max cell voltage on a normal lipo is 4.2v regardless of capacity. Crank up the mah limiter or turn it off, that's probably causing the issue. It does little to nothing for safety.

Never charge a lipo with balance turned off.

I almost always only use balance charge, Only a handful of time I've charged without balance, but only after reaching 90% with balanced charge.

 

[jkflow]

No idea on your charger model, always use balance charging and always connect the balance plug. If that gets you to 90% leave it be. I'd get a more modern charger, consider the cost of lipos you are connecting.

Yes, turn that capacity limit to the max. This feature is usually not on modern chargers. Else you would have to adjust it for every lipo.

 

[CrashBoom]

I almost always only use balance charge, Only a handful of time I've charged without balance, but only after reaching 90% with balanced charge.

Well, I'd say never really does mean never in this case. That's probably about the most dangerous operation you can perform on a lipo.

 

[RedOctobyr]

As others have said, please always balance-charge. Please don't do non-balance charging of a LiPo. And always connect the balance lead.

We really need to talk in voltages. I don't know how your charger is figuring out the charge percentages, but very few other chargers express it that way, so this isn't kind of a useful measurement for anyone else. (Edit- sorry, maybe some others use this, but it's still not a "universal" way to express the charge level, and I don't know how the companies are calculating the % charge from the voltage)

Now, if your cells are finishing at 4.10V/cell after a balance charge, that's "useful" info, and we can work on figuring out why they're not closer to 4.20V/cell. But 90% really doesn't tell people much.

I'm sure there is some sort of logic to why someone would use a capacity limit, but honestly, I can't think of what that would be for a LiPo. Perhaps it had more use for NiCad or NiMH, where it's possible the charger would fail to detect the voltage-peak that would indicate the end of a charge (as the voltage starts to drop again). So maybe the capacity limit served as a useful safety-check for those.

But LiPos are only charged to a voltage, 4.20V/cell. So a capacity cutoff, for charging, really doesn't provide anything. But again, always connect the balance lead, and always do a balance charge, for (fire) safety.

If you can post cell voltages after a balance charge, and maybe after an additional charge cycle, we can work on that. It would be helpful to know the charge current you're using and the pack capacity, such as 8A for the 8000mAh packs.

PS- macro data refiner, eh? Is someone a fan of Severance?

 

[305HemiGuy]

I just learned today from another forum member that the charger I use (Ovonic X1) is also manufactured by imars, so I'm somewhat familiar with the balance vs.normal charging options that the OP is referring to. Since I've owned the charger I've used the normal charging only, I haven't messed with the balance charging mode. When I charge my lipos my balance leads are of course plugged I'm. I believe In normal charging mode it will still balance charge the cells. I monitor each cell as they charge and at the end all cells read 4.2v. I've never had any issues with any packs doing it this way. This is just my humble suggestion, but I think you should be good to go with just using the normal charging mode. The charger will still balance as charging.

 

[vicious_oli]

I just learned today from another forum member that the charger I use (Ovonic X1) is also manufactured by imars, so I'm somewhat familiar with the balance vs.normal charging options that the OP is referring to. Since I've owned the charger I've used the normal charging only, I haven't messed with the balance charging mode. When I charge my lipos my balance leads are of course plugged I'm. I believe In normal charging mode it will still balance charge the cells. I monitor each cell as they charge and at the end all cells read 4.2v. I've never had any issues with any packs doing it this way. This is just my humble suggestion, but I think you should be good to go with just using the normal charging mode. The charger will still balance as charging.

As far as I know/remember, from the videos I've seen about my charger, they recommend balance charging every now and then, if you start having too big of a difference in voltage between cells. Still, I always balance charge first, I always plug the balance lead, even when doing the normal charge. That kinda checks out with your experience.

No idea on your charger model, always use balance charging and always connect the balance plug. If that gets you to 90% leave it be. I'd get a more modern charger, consider the cost of lipos you are connecting.

Yes, turn that capacity limit to the max. This feature is usually not on modern chargers. Else you would have to adjust it for every lipo.

From what I gather, my charger is pretty modern, I'd say its a smart charger?. The latest Gens charger is based off the IMARS III, the difference is that it can now charge 2 lipos at the same time.

I see my battery percentages with one of those Lipo battery meters, so I can check voltages while out. The charger does show total/individual cell voltage while charging. After its finished charging it gives you a rundown on how long it took to charge, final voltage, and a few other numbers.

As others have said, please always balance-charge. Please don't do non-balance charging of a LiPo. And always connect the balance lead.

We really need to talk in voltages. I don't know how your charger is figuring out the charge percentages, but very few other chargers express it that way, so this isn't kind of a useful measurement for anyone else. (Edit- sorry, maybe some others use this, but it's still not a "universal" way to express the charge level, and I don't know how the companies are calculating the % charge from the voltage)

Now, if your cells are finishing at 4.10V/cell after a balance charge, that's "useful" info, and we can work on figuring out why they're not closer to 4.20V/cell. But 90% really doesn't tell people much.

I'm sure there is some sort of logic to why someone would use a capacity limit, but honestly, I can't think of what that would be for a LiPo. Perhaps it had more use for NiCad or NiMH, where it's possible the charger would fail to detect the voltage-peak that would indicate the end of a charge (as the voltage starts to drop again). So maybe the capacity limit served as a useful safety-check for those.

But LiPos are only charged to a voltage, 4.20V/cell. So a capacity cutoff, for charging, really doesn't provide anything. But again, always connect the balance lead, and always do a balance charge, for (fire) safety.

If you can post cell voltages after a balance charge, and maybe after an additional charge cycle, we can work on that. It would be helpful to know the charge current you're using and the pack capacity, such as 8A for the 8000mAh packs.

PS- macro data refiner, eh? Is someone a fan of Severance?

I always balance charge, always with the balance lead connected, when I've done a normal charge, I'll still use the balance lead, plus I think the charger wont let me charge a Lipo without connecting the balance lead, it'll give me an error.

Lets step away from percentages then, I use that number to have a broader sense of how much juice any given pack still has, while I'm out bashing. I get the percentage number from those small lipo voltage meters that you plug the balance lead in.

My charger shows me total/individual cell voltage while charging. Charging amps is usually 5A (which is the max that charger will allow), the charging amps will go down when the balance charge is almost done, and I don't have batteries smaller than the 6900mAh SMC one, so AFAIK my charging amps are ok for my packs.

I'll report back tonight when I charge my new SMC when I get home, I'll turn off the mAh cut off, balance charge, see what final voltage it gives me.

PS- BIG fan of Severance I also really like the cinematography, the composition of almost all of the shots/scenes.

 

[Hector_Fisher]

Reviewing the imars III manual, it looks like there are only 4 modes, and "charge" mode is the balance charge mode.

I'm confused about what you mean when you're saying you switch from a "balance charge" to a "normal charge". There should be only one charge mode on your charger, correct?

 

[vicious_oli]

Reviewing the imars III manual, it looks like there are only 4 modes, and "charge" mode is the balance charge mode.

I'm confused about what you mean when you're saying you switch from a "balance charge" to a "normal charge". There should be only one charge mode on your charger, correct?

There is a strictly balance mode, and a charge mode. I suppose the confusion, my confusion.. or our confusion is me saying "balance charge", instead of just balance mode.. maybe I confused balance mode as a balance charge mode because it effectively charges the lipo as it balances.

I was always under the impression that the charge mode is the balance charge mode on the imars III, but since there is a "balance mode" I always went to that for charging, because I'm trying to handle my lipos as best as possible.

 

[Hector_Fisher]

There is a strictly balance mode, and a charge mode. I suppose the confusion, my confusion.. or our confusion is me saying "balance charge", instead of just balance mode.. maybe I confused balance mode as a balance charge mode because it effectively charges the lipo as it balances.

I was always under the impression that the charge mode is the balance charge mode on the imars III, but since there is a "balance mode" I always went to that for charging, because I'm trying to handle my lipos as best as possible.

Looks like the options are "Charge", "CellBAL", "STORAGE", and "DISCHG". CellBAL will just balance the voltage between the cells. Since "Charge" performance a balancing charge (per the manual), you should only need to do this. As far as I can tell, CellBAL will not add more mah to the pack, so no need to use that after a charge, as they should already have been balanced.

As always, to your first question, you charge to voltage levels, not mah. Charge to 4.2v per cell and establish the max allowed amperage (for example, set the charger to 5a) based on what the battery recommends (or 1c if the batt doesn't say). Whatever mah gets put in the pack, gets put in the pack.

 

[vicious_oli]

Looks like the options are "Charge", "CellBAL", "STORAGE", and "DISCHG". CellBAL will just balance the voltage between the cells. Since "Charge" performance a balancing charge (per the manual), you should only need to do this. As far as I can tell, CellBAL will not add more mah to the pack, so no need to use that after a charge, as they should already have been balanced.

As always, to your first question, you charge to voltage levels, not mah. Charge to 4.2v per cell and establish the max allowed amperage (for example, set the charger to 5a) based on what the battery recommends (or 1c if the batt doesn't say). Whatever mah gets put in the pack, gets put in the pack.

Yes, those are the 4 options. CellBAL will charge your battery, since that is what I mostly use, not just balance the cells to an arbitrary voltage, it will balance and charge them up to 90% voltage capacity.

I don't do a CellBAL after doing a Charge.. I would sometimes do a Charge after a CellBAL, to get the voltage to 4.2v per cell.

I was always under the impression, as you said, that the Charge function my charger is in fact a Balance Charge, but thinking better safe than sorry, and seeing as CellBAL gets the battery to 90% per voltage meter.. thats what I always default to.

 

[Hector_Fisher]

Yes, those are the 4 options. CellBAL will charge your battery, since that is what I mostly use, not just balance the cells to an arbitrary voltage, it will balance and charge them up to 90% voltage capacity.

I don't do a CellBAL after doing a Charge.. I would sometimes do a Charge after a CellBAL, to get the voltage to 4.2v per cell.

I was always under the impression, as you said, that the Charge function my charger is in fact a Balance Charge, but thinking better safe than sorry, and seeing as CellBAL gets the battery to 90% per voltage meter.. thats what I always default to.

Ah, so i assume the CellBAL lets you choose a desired voltage to balance the cells to, and you've been setting that to max (90%). Since the "Charge" performs a full balance charge, you can use that all the way up to 100%, no need to swap

 

[305HemiGuy]

Ditto. I think you're good to go with the normal charge function.

 

[jkflow]

Your default should be charge only.
The balance mode is typically used when you have a bad cell or for other weird purposes. Simply don't use it and you will be fine.

Yes, charge mode adjust current based on charge level and will switch to balancing at the end.

 

[vicious_oli]

Ah, so i assume the CellBAL lets you choose a desired voltage to balance the cells to, and you've been setting that to max (90%). Since the "Charge" performs a full balance charge, you can use that all the way up to 100%, no need to swap

CellBAL does not let me choose a desired voltage, as far as i know.

I'll start using more often just the Charge function, see how the voltage between cells looks

 

[RedOctobyr]

If I were to guess, maybe CellBAL looks at the cells, maybe 4.10V, 4.05V, and 4.07V, and makes them all the same. It presumably either tries to bring them all up to the highest (4.10V), or down to the lowest (4.05V). But I would imagine, based solely on the name, and the fact that this is a separate function, that the goal is just to bring the cells to a uniform voltage.

If you haven't already, record the cell voltages after running a pack, then do CellBAL. Maybe the pack won't get charged up to ~4.2V, but will instead go from 3.69V, 3.75V, and 3.73V, to all at 3.75V, or something like that.

My charger has a separate Balance process that I can run. I don't know whether it brings them up, or down, but it tries to make them all uniform. It's been a long time, I don't remember if it asks for a target voltage, or it just picks one based on the starting voltage. But on my iCharger, I don't think this is really a "charging-up" type of function.

It will be interesting to hear what you see, once we're expressing things in voltages. And if we want to look at more detail, it's worth talking about individual cell voltages, to see the before/after differences.

And yeah, Severance is great! I made kind of an anguished sound at the end of the season, especially when my wife said that was the finale Whew, quite a show! I'm not artistic enough to appreciate stuff like the cinematography standing out, but it's an interesting premise, and is very well done!

 

[jkflow]

CellBAL will do exactly that, it will average out the cells with respect to each other.
It will not add any capacity etc. unless the charger manual tells you something different.

You can buy handheld cell balancers as well.

 

[vicious_oli]

And yeah, Severance is great! I made kind of an anguished sound at the end of the season, especially when my wife said that was the finale Whew, quite a show! I'm not artistic enough to appreciate stuff like the cinematography standing out, but it's an interesting premise, and is very well done!

that finale, had me literally standing up from the sofa saying " NO WAY"


Well, here as some photos of the Charging process on the afore mentioned SMC lipo. I had already started balancing it when I got it out of the box, so voltage is already higher than storage.

As you can see, here I had just started charging it. Its charging at 5A, time elapsed is 1:37

Here we're getting close to a full charge, notice how charging amps have now dipped to 2.5, as it tries to balance that middle cell

Charging amps continue to dip as it gets close to charging that middle cell

Charge DONE

Here is the total/indivual voltage, per the battery checker. Here you can see where I get that 99%