Scott Smith

My Feedback: (4)

I read the following on another form:

The increase in internal resistance is also responsible for the voltage drop when you remove the battery from the charger. As a general rule, if the pack drops below 4.0 volts per cell (resting voltage taken 15 minutes after being removed from the charger), it is below 80% of its initial capacity and is ready to be recycled.

Can anyone confirm this statement with actual experience?

serious power

How is internal resistance actually measured,and what causes it to increase??

Brian

OhD

Did they specify the load? You can't really measure the internal resistance without loading the pack. The effects of high internal resistance are more serious in some applications than others and may or may not affect capacity or apparent capacity. In an electric propulsion system high resistance is a big problem because of the high current and large voltage drop. In a transmitter with a relatively low current it is not critical.

Jim O

Scott Smith

My Feedback: (4)

Here's the link to the [link=http://helifreak.com/showthread.php?t=52305&page=2]post[/link] Post #13

Gulliver

A simple way to measure internal resistance is as follows:

Measure the no load voltage.

Measure the voltage under a known load ( A amps) with a whattmeter for instance.

The internal resistance is the (No-load voltage - the Loaded voltage) divided by the current - or (Vnolad - Vloaded)/A.

If the current can be set at one amp, you don't even need a calculator.

stek79

Interesting question.

From your experience with electric pattern flying, what is the number of flights that can be done with a lipo pack, before considering it degradated - or at least not as performant as new?

serious power

Gulliver,

Thank you.

Regards

Brian

serious power

I have just started to try this method.
Would have meant more if done when batt,,, were new, these results would be a reference.

At what charge state should test be done

I am using 12.5A load.

Perhaps some people would post results here for reference purposes.

When cycling to check capacity what voltage is recomended to bring the pack down to, and what % of cap,, is left in there at that voltage ??.

Regards

Brian