Jump to content
Baldyslapnut

Max Amps from a Battery

Recommended Posts

Baldyslapnut

We have had a reduction in the minimum weight of the flight pack for F5B this year.

So I want to ask how do you work out what is the maximum number of Amps a pack will produce.

So currently we use circa 10s or 9s 1,800mah packs. These give pack weights of about 450g.

We can now go down to 400g. There are a number of good 1,350 packs out there. However, are they powerful enough.

Any suggestions on how to calculate max amps released would be gratefully received.

Regards

 

Greg

 

 

 

Share this post


Link to post
Share on other sites
paulj

Wouldn't this be the C rating of the pack? For example, a 1300 mAh pack with a 40C rating should be able to deliver 40 * 1.3 A = 52 Amps? Looks like you need to consider the nominal discharge rate and the burst discharge rate:

http://multicopter.forestblue.nl/lipo_need_calculator.html

  • Like 1

Share this post


Link to post
Share on other sites
wookman

"The maximum recommended continuous discharge current of a Lithium Polymer battery is the Battery Capacity (mAhr) x the 'C' Rating, i.e. a 1000mAhr pack with a 25C rating would have a maximum continuous discharge rating of 1000 x 25 = 25,000ma (25Amps). The 'C' rating is a reflection of the internal resistance of the battery and its ability to satisfy high current demands. Unfortunately not all batteries live up to the 'C' rating on the label."

This is lifted from Stan Yeo's Phoenix Model Products website, full article here. https://www.phoenixmp.com/articles/cratingandtimetocharge.htm

  • Like 1

Share this post


Link to post
Share on other sites
mikef

I would be inclined to take any battery label claims with a pinch of salt.  I think you need to test examples to see what they give in practice, remembering that the more you abuse the pack, the more often you'll be buying a new one.  Don't forget that the voltage will drop when you pull a high current, this may cause other problems.

  • Like 1

Share this post


Link to post
Share on other sites
wookman

Absolutely Mike, lots of the C rate claims are quite optimistic and there is definitely a trade off in longevity of the cells if you operate up towards the limit.

Share this post


Link to post
Share on other sites
Baldyslapnut

Thank you for the advice.

I have some new packs to try. So it will be interesting to see if the 70c 1,800 pack we are using currently is better than the smaller 100c 1,350 pack I will be testing.

Regards

 

Greg

 

 

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.