2s initial charge Mah

[burakol 462]

Just wanted to know if I should expect a full 4000mah charge capacity for an initial lipo balance charging? 

I bought a few 2s lipo and I charged one up today but it stopped when it reached 2000mah, which is well short of the rated charge capacity... 

When it came, it had the correct storage value of 7.6v (3.8/cell)... 

[Wooders28 4723]

7 hours ago, burakol said:

Just wanted to know if I should expect a full 4000mah charge capacity for an initial lipo balance charging? 

I bought a few 2s lipo and I charged one up today but it stopped when it reached 2000mah, which is well short of the rated charge capacity... 

When it came, it had the correct storage value of 7.6v (3.8/cell)... 

How do you know it's only charged to 2000mah? 

Do you look at the charge amps, drop from 4a to 2a? 

I've only individual cell volt readout on my charger, 4.2v is charged.

[Silver-Can 402]

Not sure if I understand correctly but on my charger it only displays the mah that has been put back in, rather than the cumulative total. Eg if I've have a good bash with my 4000mah lipo and the low voltage cut off has activated on my ESC, once fully charged it might show something like 3000 mah having 'gone back' into the battery once fully charged, rather than 4000mah total capacity.

In the case of your battery it sounds like it was already 'half full' ie had 2000mah in it, and charging it fully added to the other 2000mah to make the battery 100% 'full', which is what your charger was telling you.

I think a more reliable way of knowing how charged your batteries are is looking at the voltage per cell. Once both cells are at 4.2V I know they're fully charged.

And remember to always balance charge your lipo too 👍

[burakol 462]

Both cells read 4.2 so I know it was charged to the proper voltage... I just thought that it should still put back 4000mah or close to it... but it does make sense... you only put back what was lost... so if the battery came in storage mode, then it only needed to be "topped off"

[burakol 462]

6 hours ago, Wooders28 said:

How do you know it's only charged to 2000mah? 

Do you look at the charge amps, drop from 4a to 2a? 

I've only individual cell volt readout on my charger, 4.2v is charged.

My charger showed how much capacity/mah was put in... yeah, I watched the amperage drop as suggested as it came near to the end of the charge cycle. 

[Matty36 267]

I've only ever used fast chargers for racing and I've never had a charger that gives a battery capacity reading. Mine have only given the capacity that ive taken out, which is useful to determine if the car can take a faster motor or upgrade gearing.

[Mahjik 197]

What charger do you have and is a programmable where you can set the charge rate/time?  

 

[burakol 462]

I have the imaxb6... possibly a clone one... 

You can set the charge rate (in amperage), but not time... 

I think I've figured it out. 

[Mokei Kagaku 2706]

I'm not at all an expert in this field and don't pretend to either, but I used to work for the french battery manufacturer Saft before moving to Germany, and by pure coincidence, I'm now working in BEV battery systems development and QA for the automotive supplier Dräxlmaier (which "nobody" has heard of, but Google will find it for you! ) with some BEV applications for several OEMs. So, in all honest humbleness and being aware of my major shortcomings, I would like to add my 2 Cents.

The measured Ah from the charger is not the same as the resulting Ah in any battery. It differs from technology to technology, but no battery technology available is capable of 100% efficiency in "converting" Ah from the charger into the identical Ah stored in the battery. It's even a lot worse when considering charged Wh vs. stored Wh.

For Ni-Cd and Ni-MH, roughly 30% is lost. Or put in other words, you need to charge 40% more Ah than the resulting Ah stored in the battery. Li-technology is quite a bit more efficient, but recent studies document that 15-35% more Ah have to be charged than the resulting stored Ah in the battery.

Of course, some charger manufacturers (especially for 1:1 electric vehicles) take this loss into account, so the instrument reading show a calculated Ah suitably below charged Ah to represent the stored Ah. This makes for "nicer" figures, but is actually fraud and gives the impression of BEVs being more environmentally friendly than they actually are.  The stored Ah have to be calculated as there doesn't exist any technology to actually measure it.

Some of you will probably protest when reading the previous sentence with battery dischargers in mind, and your protests would be justified. Well, kind of...  I'll try to explain what I mean:

No battery have a fixed and constant capacity. Actual capacity varies with the discharge current/load profile, number of cycles, age, charging methods, storage conditions and temperature and other factors. The capacity stated for any battery, is the nominal capacity (if the manufacturer is serious), which is based on fixed factors that are more or less valid for actual use. In actual applications, the actual capacity will mostly be a little to a lot lower than the nominal capacity and in rare cases, a bit higher.  This also means that the capacity measured by a discharger, will not be the same capacity as you get from the battery when using it in the model. That is, unless you can simulate the real and varying discharge current/load profile and varying temperature in the model with your discharger.

So, as a rough conclusion, not even the best charger can tell you the  actual Ah stored in the battery, but just the charged Ah and/or approximate calculated stored Ah. Similary, not even the best discharger can measure the actual Ah you will get from a battery in your actual application, unless the discharger can be fed with the exact parameters of your application. This can be done fairly accurately for applications in a temperature controlled environment and a constant current or current that varies in a very predictable manner (e.g. simple load profile), but is really impossible with the complex and random load profile of an RC model. This again means that the actual Ah you get from a battery varies from discharge to discharge . 

So don't rely on a charger/discharger's measured (and calculated) Ah readings as a true and correct indication for the actual Ah available in your model or any other application.

[howaboutme 247]

1 hour ago, burakol said:

I have the imaxb6... possibly a clone one... 

You can set the charge rate (in amperage), but not time... 

I think I've figured it out. 

Most chargers have the capability to set a maximum charge time. This is often used as a second safety or maintenance check as taking a long time to charge may indicate your battery is having trouble balancing (since that takes the longest usually) or something else worse.

mah doesn't matter to me. Voltage is the only thing that counts for lipo. 3 #'s that you should care about, what your LV cut off is (# changes depending on your comfortability), storage charge (again, that # is fluid too) and max (full) charge.

[burakol 462]

31 minutes ago, Mokei Kagaku said:

I'm not at all an expert in this field and don't pretend to either, but I used to work for the french battery manufacturer Saft before moving to Germany, and by pure coincidence, I'm now working in BEV battery systems development and QA for the automotive supplier Dräxlmaier (which "nobody" has heard of, but Google will find it for you! ) with some BEV applications for several OEMs. So, in all honest humbleness and being aware of my major shortcomings, I would like to add my 2 Cents.

The measured Ah from the charger is not the same as the resulting Ah in any battery. It differs from technology to technology, but no battery technology available is capable of 100% efficiency in "converting" Ah from the charger into the identical Ah stored in the battery. It's even a lot worse when considering charged Wh vs. stored Wh.

For Ni-Cd and Ni-MH, roughly 30% is lost. Or put in other words, you need to charge 40% more Ah than the resulting Ah stored in the battery. Li-technology is quite a bit more efficient, but recent studies document that 15-35% more Ah have to be charged than the resulting stored Ah in the battery.

Of course, some charger manufacturers (especially for 1:1 electric vehicles) take this loss into account, so the instrument reading show a calculated Ah suitably below charged Ah to represent the stored Ah. This makes for "nicer" figures, but is actually fraud and gives the impression of BEVs being more environmentally friendly than they actually are.  The stored Ah have to be calculated as there doesn't exist any technology to actually measure it.

Some of you will probably protest when reading the previous sentence with battery dischargers in mind, and your protests would be justified. Well, kind of...  I'll try to explain what I mean:

No battery have a fixed and constant capacity. Actual capacity varies with the discharge current/load profile, number of cycles, age, charging methods, storage conditions and temperature and other factors. The capacity stated for any battery, is the nominal capacity (if the manufacturer is serious), which is based on fixed factors that are more or less valid for actual use. In actual applications, the actual capacity will mostly be a little to a lot lower than the nominal capacity and in rare cases, a bit higher.  This also means that the capacity measured by a discharger, will not be the same capacity as you get from the battery when using it in the model. That is, unless you can simulate the real and varying discharge current/load profile and varying temperature in the model with your discharger.

So, as a rough conclusion, not even the best charger can tell you the  actual Ah stored in the battery, but just the charged Ah and/or approximate calculated stored Ah. Similary, not even the best discharger can measure the actual Ah you will get from a battery in your actual application, unless the discharger can be fed with the exact parameters of your application. This can be done fairly accurately for applications in a temperature controlled environment and a constant current or current that varies in a very predictable manner (e.g. simple load profile), but is really impossible with the complex and random load profile of an RC model. This again means that the actual Ah you get from a battery varies from discharge to discharge . 

So don't rely on a charger/discharger's measured (and calculated) Ah readings as a true and correct indication for the actual Ah available in your model or any other application.

Thank you for the thorough explanation. At this point, as long as I follow safe and best practices, I think I am in a good place in my shift to LiPo. I just need to be aware of the obvious signs of when the end of service life for the battery to not cause any possible hazards. 

25 minutes ago, howaboutme said:

Most chargers have the capability to set a maximum charge time. This is often used as a second safety or maintenance check as taking a long time to charge may indicate your battery is having trouble balancing (since that takes the longest usually) or something else worse.

mah doesn't matter to me. Voltage is the only thing that counts for lipo. 3 #'s that you should care about, what your LV cut off is (# changes depending on your comfortability), storage charge (again, that # is fluid too) and max (full) charge.

You are correct, my charger does have a timer as a safety measure, but not as a means to set a charge mode. 

As far as the numbers go, I have set it to the following:

LVC alarm = 7.0v or 3.5v/cell

Storage = 7.6 or 3.8v/cell

Full charge = 8.4v or 4.2v/cell

And then for my ESC that has built it LVC, it is whatever the default value is... I think the HW1060 is at 3.25v/cell or 6.5v total. 

[Mahjik 197]

I assume you have figured it out, but just in case.  For Lipo charging, the amps are the important part.  If you have a 4000mah battery, you want to charge at mah / 1000 = charge amps for 1C.  So 4000 / 1000 = 4 amps for charging at 1C.   

[burakol 462]

Yes, thanks a lot!

[Wooders28 4723]

4 hours ago, burakol said:

I have the imaxb6... 

The B6 was my first charger!

How do you get the mah thing? 

If I remember right, you press the left button while balance charging, and it gives each cell voltage?

[burakol 462]

The number on the lower right side when charging shows you the total mah that was put in. 

6 minutes ago, Wooders28 said:

The B6 was my first charger!

How do you get the mah thing? 

If I remember right, you press the left button while balance charging, and it gives each cell voltage?

 

[Wooders28 4723]

13 minutes ago, burakol said:

The number on the lower right side when charging shows you the total mah that was put in. 

 

I'm going to have to dig it back out, and have a look! 😂