Internal resistance in lipos

[RobW]

I have three packs of Nvision 7200 100c 1 cell lipos I use in my gt12, all about 6 months old and used in rotation so similar usage

When charging them on an Orion advantage touch pro I get IR figures of 2.1, 3.8 and 5.2 for the three packs - m and symbol I cannot get on my keyboard.

I appreciate the actual figure is probably fairly meaningless unless the charger has been accurately calibarated but does anyone have any idea if these differences are big enough to actually make a noticeable difference? I feel like the one with the highest IR is the worst performing but not sure if it is all in my head...

Rob

[Northy]

It acts as a little resistor as it suggests.

If you pull current through a resistance, you get a voltage drop. The higher the resistance the more voltage drop you get.

For say 20A discharge current on your 3 packs:

V drop = 20 x 0.0021 = 0.042V

V drop = 20 x 0.0038 = 0.076V

V drop = 20 x 0.0052 = 0.104V

So it makes a difference, but if you will notice it is debatable to be honest.

G

[RobW]

Thanks for the simple explanation, Graham, even I understand that:)

Given how close it can get in gt12 and limited power, think it is probably enough of a difference to bother to use the highest ir in practice and lowest in last round of qualifying.

Rob

[mattr]

Just jot the IR down on a sticky label on the battery. See if you can notice a difference next time you drive. Or use the lowest IR pack as "best".

It's not likely to make a noticeable difference.

But. Marginal gains and all that.......