Do you weigh your lipos (I think you should!)

[Stearman65]

I'm gradually putting together all the paraphernalia needed when starting from scratch on an electric powered build. I've already bought 2 x lipos an Overlander 3S 2900MAH & Ripmax Hi Energy 3S 2700MAH. This morning, out of the blue, a third arrived a Zippy 3S 2700MAH, which I had cancelled 2 weeks ago with Hobby King under circumstance related in a previous thread.

Now, the reason for this thread, there is a noticeable difference in weight between the Zippy & the other two, the Zippy was much heavier. So I got the wife's kitchen scales out to check. The Zippy weighed in at 248 g, the Ripmax at 169 g & the Overlander at 182g.

They are all meant for the Topmodel CZ Challenger when it's built, the position of the battery is well forward of the CG, & according to the plan the CG is fairly critical. So it looks like if I balance the model for the Zippy, I will have to add ballast when using the Overlander & R/Max. I'm not sure yet if there is a tolerance to move the batteries forward or back as the model is still in the box waiting for the Stinson to sell. The Zippy is also around 30mm longer than the other two, which are similar sizes. The main technical difference in the Zippy & the others is the C rating which is much higher. Could it be the Zippy is incorrectly labeled?

Any thoughts on the matter welcomed.

[Romeo Whisky]

I always weigh them, always have - and I label them with the weight too.

I have found that batteries of supposedly the same brand, volyage, mAh, C rating and even identical labels, can vary in weight by up to 15g. Maybe not too relevant in bigger models but in flying wings and smaller models it can matter!

Similar capacity batteries from different brands can vary even more.

[Max Z]

I cannot make out the C-value of the Zippy, but usually the higher the C-value (discharge rate), the higher the weight.

The Overlander and the Ripmax both seem to be 30C, hence the weights are comparable.

[Simon Chaddock]

You should also not assume that what is says on the label is always true!

Unless there is a difference in the chemistry (higher C value?) there is a good chance that a lighter battery also has less capacity.

The problem is it is hard to test what a batteries actual capacity is without voiding any warranty and the marketing people know it!

[Piers Bowlan]

Is this your Zippy Compact 2700mAh LiPo. This is the 40c version, they also do a 25C version too that is lighter. The weight is given as 235g, so under the 248g when you weighed yours but not by a lot. The heavier batteries (of the same stated capacity) generally hold their voltage better under load so deliver more power as a consequence. That is my subjective opinion anyway!

As you are building the model I would ensure that the battery tray has sufficient length to facilitate some fore and aft battery position adjustment. Obviously the fuselage former positions may make that difficult if not impossible. Where I have models where there is scope for adjustment, I mark the battery tray to indicate the forward position of batteries of different weights so that the C of G is not affected. Some models are less critical in this respect. In any event I try to avoid adding weight like the plague!

[Frank Skilbeck]

Where they all in the same state of charge

[Stearman65]

Posted by Piers Bowlan on 01/12/2018 12:26:11:

Is this your Zippy Compact 2700mAh LiPo. This is the 40c version, they also do a 25C version too that is lighter. The weight is given as 235g, so under the 248g when you weighed yours but not by a lot. The heavier batteries (of the same stated capacity) generally hold their voltage better under load so deliver more power as a consequence. That is my subjective opinion anyway!

As you are building the model I would ensure that the battery tray has sufficient length to facilitate some fore and aft battery position adjustment. Obviously the fuselage former positions may make that difficult if not impossible. Where I have models where there is scope for adjustment, I mark the battery tray to indicate the forward position of batteries of different weights so that the C of G is not affected. Some models are less critical in this respect. In any event I try to avoid adding weight like the plague!

That was a very useful reply, thank you. The zippy doesn't have the C rating on the wrapping, but it could have been over 40C, just checked the order & it says -

ZIPPY Compact 2700mAh 3s 60c Lipo Pack

9067000033-0

Europe (EU)

£21.06

1 Shipped: 1

£21.06

Edited By Stearman65 on 01/12/2018 12:39:53

[Geoff Gardiner]

I tend to use 5000mah batteries in my models. I do, however, have a single 4000mah battery and i have added a stick on weight (car wheel balance type) so that I can use it without CofG worries. Better that than not using it at all.

[Steve Colman]

You could have made life easier for yourself by buying 3 lipos of the same size, type and manufacturer.

[Bob Cotsford]

60C have twice the current capacity of your others, that's why they are heavier. Even the power leads look to be a heavier guage of wire.

[Alan Gorham_]

Posted by Stearman65 on 01/12/2018 12:39:17:

That was a very useful reply, thank you. The zippy doesn't have the C rating on the wrapping, but it could have been over 40C, just checked the order & it says -

Does the Zippy pack not say "60C Series" in red on the label?

[Stearman65]

Just had a look under a magnifying glass, it looks like 600 series. Then I took a macro shot & blew it up 300% and it could say 60C, but it doesn't exactly pop out at you.

[Alan Gorham_]

As well as stating the C rating on the battery pack I decided to check the listing on the HK website.

Here's what I found:

The selection page clearly shows the C rating:

The detail page foe the pack in question clearly shows the weight of the pack:

So perhaps there's no need to weigh your Lipos if you check what you are buying using the readily provided info?

[PatMc]

Should have gone to Specsavers

[Mark Howard 1]

Although the Zippy is the heaviest pack, it is also 30mm longer so if it fits and you can achieve the desired CoG, you should be able to move the other batteries forwards to hopefully achieve the same CoG as you must have 30mm of spare space to play with.

One would hope that the Zippy, being a 60C pack, should perform better than the others so it might be worth persevering with it if it fits ok.

I've added markings in the battery bays of some of my planes to allow me to position different batteries correctly.