Charging question

[Major Bladebreaker]

Hi Folks,

I have several FP 2070's (25C) which I charge using a cheap "smart" charger which is connected to a Hyperion LBA6 balancer which in turn is connected to the battery tap when I charge it. The charger only charges at 500Mah which is well below the recommended charge rate of 1C. Someone recently suggested to me that too low a charge rate could be a problem as it may throw off the cut-off mechanism in the charger and possibly the balancer thereby causing the battery to be overcharged unwittingly. Has anyone ever heard of this? Thanks!!

Mark

[charlieh]

What charger you are using? some charger, especially that come with your plane, just give a very small output of 0.5A and, it such case, you should get a better charger. To slow charge you battery at 0.5A do not have any adverse effect on your battery and auto cut-off (if your charger have it and did give a 0.5A charge current) except it take forever to charge.

Also try to inspect your charger, if this is not a 0.5A charger, you may have the wrong setting.

[Major Bladebreaker]

Charlieh,

Sorry to take so long to reply and thanks for your input! I bought a new charger that will charge at 1C. In the meantime, how bad is it if my batteries balance but need re-balancing 5 minutes later? They seem to work fine despite this but have I damaged them? Is it possible that they won't stay balanced if they are well undercharged? Last question (I promise!...): how do you use a basic voltmeter to check for individual cell voltage? Thanks!!

Mark

[charlieh]

Not at all, Mark.

Each and every lipo cell has it's own internal resistance(IR), when current pass through the cell during charge, a virtual current is created by the input current V=A*IR, the higher the IR, the bigger the virtual current. The charge pick up both actual current and virtual current and stop when these add together reached 4.2V. After a while, the virtual current disappear and the actual cell voltage varied.

The CCCV algorithm charge the battery using CC mode, that is a steady current is supply to the cell, when it reached 4.2V per cell, it switched to CV mode, where the charge current will stop for a short while then a reduced is use and repeat the same process until the current reached as low as 100mV and stop.

That's explain why you experience cells not balance after a while. However, for a good manufacturers, their cells are always matched before assembly (more expensive to make) and the difference shouldn't exceed 10mV. That also answer your other question - you haven't damage the cell, it may be under charger (less CV mode process time) but shouldn't be far off. If this case continue, your battery may not be a good pack.

A voltmeter is a little gadget with some pins (like a blinky) and when you plug that into the balance lead, it will shows the voltage of individual cells.

PS I have found the following lead on FP2070 http://runryder.com/helicopter/t404217p1/, your FP maigh have problem, will try to find out the answer for you.