Compensating For Charging Magnet Resistance?

[adamlau]

If I went with MAGCRAFT 0.25" x 0.063" rare-earth charging magnets, how would I compensate for the increased resistance (resulting in a charge below 4.2V)? Set the ending voltage by adding the measured voltage difference between charging with magnets and charging without to 4.2V? Is there a standard procedure for accomodating this increased resistance (set ending charge to 4.3V, for example)?

 

[SilverFox]

Hello Adamlau,

Most Li-Ion chargers don't let you adjust the ending voltage. They charge to 4.2 volts for the Li-Po setting, 4.1 volts for the Li-Ion setting, or 3.6 volts for the Li-Fe setting.

However, if you are using a power supply as a charger, then you have control over the voltage.

I would recommend never setting the voltage above 4.2 volts. You can make up for the extra resistance by making your charging leads as short as possible, using low resistance connections, and charging at lower rates.

Tom

 

[adamlau]

I suppose I can strip some unused AudioQuest cables of their OFC core and build short leads. But at how low of a rate? 0.5C versus 1C? What are some recommended leads (if I chose not to build my own) which qualify as low resistance?

 

[SilverFox]

Hello Adamlau,

The larger gage the wire, the lower its resistance.

By low charging rates I was thinking of 0.25C instead of pushing to the recommended maximum of 1C.

Tom

 

[adamlau]

If charging at 0.25C (0.25 * 2200 mAh = 550 mAh), then what would be the advantage in using a hobby charger over a Pila IBC at 600 mAh to charge Li-Ion batteries exclusively (other than being able to charge more than two batteries at a time)?

 

[VidPro]

Hello Adamlau,

I would recommend never setting the voltage above 4.2 volts. You can make up for the extra resistance by making your charging leads as short as possible, using low resistance connections, and charging at lower rates.

Tom

yup the voltage shouldnt change, because that is still the peak voltage.
a poor connection would just reduce the total current flow, depending on HOW poor the connection was, each time its connected.
or make the computer screw up completly because the resistance and/or current flow changed.

i have (finnaly) added magnets to my connection collection, (i avoided it before) and they suck. The connection isnt ALWAYS perfect, had to do a few tricks to insure connection, and even then i had readings that i could visually SEE, to know if it was fully connected. so i could move things around till i knew i was getting a great connection, not a poor one.

I ended up figuring that copper covered magnets :wave: might make a full connection all the time. or something like putting a connection point (wire) under the actual magnet, so its not the magnet, making the connection, the magnet is just doing the pulling of the items together, the connection is under it, making a great connection.

i am not saying that magnets cant make the connection, they can, it just was iffy many times, untill i adjusted it.

 

[Mr Happy]

I ended up figuring that copper covered magnets :wave: might make a full connection all the time.

Copper oxidizes, but how about gold plated magnets? Gold is the best conductor of all and it never tarnishes.

or something like putting a connection point (wire) under the actual magnet, so its not the magnet, making the connection, the magnet is just doing the pulling of the items together, the connection is under it, making a great connection.

Absolutely, I have thought much the same thing. The modern ultra-powerful magnets are surely strong enough to work on the outside of the connection and pull it against the cell? I must get some magnets to play with.

 

[Fallingwater]

Most Li-Ion chargers don't let you adjust the ending voltage. They charge to 4.2 volts for the Li-Po setting, 4.1 volts for the Li-Ion setting, or 3.6 volts for the Li-Fe setting.

In my experience, LiIon and LiPo max voltage is 4.2 in both cases.

 

[SilverFox]

Hello Adamlau,

The advantage of using a hobby charger is that when you utilize a "proper" connection, you can charge at 1C and reduce the amount of time you have to attend to your Li-Ion charging.

Tom

 

[SilverFox]

Hello Fallingwater,

That is usually the case, but there are some exceptions. Saft, for one, has some Li-Ion cells that have a recommended 4.1 volt maximum.

When charging Li-Ion cells it is always a good idea to refer to the manufacturers data sheet for the recommended maximum charging voltage.

Tom

 

[wptski]

Older Li-Ion cells used a different component for either the +/- end which is why v4.1V was requiired but now "most" all use the newer component which requires 4.2V.

 

[Anders]

Hello.

Is the only diiference with RC charger mode this cell limit, 4,1 VS 4,2, the same charging algorithm for both Li-Po and Li-Ion?

Is it ok to charge Li-Ion with Li-Poly settings if I know for certain that the Li-Ion cells I charge is the "new" ones with a nominal effect of 3,7 Volt= ending voltage of 4,200.
I just bought a RC charger and I want to be sure if I understand it.
adamlau: do you have a charging clamp?, if not it is a good thing to build one.
http://www.candlepowerforums.com/vb/showthread.php?t=138652&highlight=charging+clamp
http://www.candlepowerforums.com/vb/showthread.php?t=89363&highlight=charging+clamp


Anders

 

[SilverFox]

Hello Anders,

Cells that have a maximum charge voltage of 4.2 volts can be charged to 4.1 volts without any problems.

Yes, the charging algorithm is the same, only the ending voltage is different.

Tom

 

[Anders]

Hello Anders,

Cells that have a maximum charge voltage of 4.2 volts can be charged to 4.1 volts without any problems.

Yes, the charging algorithm is the same, only the ending voltage is different.

Tom

Thankyou Tom.:wave:

I know that it is not a problem with charging 3,7 volts Li-Ion at 3,6 Volts settings, I just wanted to know if it was ok to use the Li-poly settings with Li-Ion cells

Sometimes 87% isn't enough= 4,1 Volt, and I will see now if the charger ends the charge at 4,20 Volts for Li-Ion cells.

One good benefit with BC 6 is that you can use "storage" control= the cell charge or disharge to 3,75 V for 3,6 V cells and 3,85 for 3,7 Volt cells.


Anders

 

[MorePower]

Copper oxidizes, but how about gold plated magnets? Gold is the best conductor of all and it never tarnishes.

Actually, silver is the best conductor among pure metals, followed closely by copper. Gold would be 3rd on the list. You are correct in that gold reacts with typical atmospheric molecules very slowly and would maintain conductivity better that copper.

 

[cy]

best way to compensate for magnet resistance is .... get rid of em!

charging clamps are cheap and easy to make. link to instruction in my sig.