Batteries Lipo Batteries Explained

PLANETGETLOW

PLANETGETLOW

Banned
Man there is ALOT of debate on how long to leave a battery fully charged. Some say a week is okay (Even ThunderPower), some say never; only fully charge the day of flight. I personally charge RIGHT before I go fly but would like to charge the night before. I however do not want to mess the IR (internal resistance) up in any of them by being lazy.

Any thoughts on this?
 
murankar

murankar

Staff member
I have been following the info I get from Progressive RC.

As a rule I will charge the night before or the day of just before I leave. I try not to leave them fully charged for more the 24 hour period.
 
Smoggie

Smoggie

Well-Known Member
I believe the reality is that any time fully charged increased the rate of degradation, so you should limit it as much as practical. But you also have to be realistic, batteries are there to use and the wont last forever no matter how careful you are, so dont become a slave to battery care. I charge on the morning of use which is convenient for me because I have a powerful charger that will do all my batteries in half an hour or so. If have a battery that's charged and my plans change meaning it wont be used for a day or two I usually put it in a sealed container in the fridge. refrigerating a charged battery is almost as good as discharging to storage.

Another thing to consider is that a battery is at it's most dangerous when fully charged.

This is the best resource I've found for info on batteries. It's written by genuine battery experts and the data is based on actual battery science and testing: How to Prolong Lithium-based Batteries - Battery University

PS.. Our LiPos are just a type of Lithium-Ion battery. The chemistry is the same, the only difference is the polymer pouch that our flat cells are packed in rather than the cylindrical metal case.
 
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Smoggie

Smoggie

Well-Known Member
I usually charge at 2C but if i'm in a hurry i'll do 3C.. So that would be twice or three times the battery capacity in Amp-Hours. For example a 6S 5000mAh will take 10A for a 2C charge. I usually charge four or more in parallel so i can max out my charger at 40A.

Discharging down to storage can be a problem if you have big batteries because most chargers have very poor discharge power rating, it takes ages. I made a discharger out of a modified hairdryer that connects to my charger to act as a resistive load. This lets me discharge at 40A / 1000W which gets the job done in no time.
 
Heliman450

Heliman450

Well-Known Member
Hi all, the time has arrived for me to start thinking long and hard on this subject. Really good stuff included (thanks for the link Steve) but it'll take a bit of digesting to consider myself minimally competent on the subject :biggrin1:

Two of my 6-cell 5000maH are beginning to grow a bit. I noticed this only due to pairing up the batteries for use on my T-Rex 700X. It wasn't by design but they happened to be my first bought and most recently purchased (18 months vs 3 months). At first, I thought it was something to do with bad pairing but the oldest one's partner looks about the same. Looking at the website's data, it seems to me that it's probably due to me NOT storing in the fridge as the storage temperature is a marked negative on performance starting at around 25 deg C (77 deg F).

I'm thinking to buy my replacements separately and buy one battery now and wait until early New Year for my next. I want to build up to having 12 as my first target as my next project is to be a Velos Rotors 880, which needs 4. My question to the more experienced.................

What do you think of the strategy?

I'd also conclude from the website to stay away from the batteries offered in sales as there is also evidence that age plays a role, too. I'm sure they don't offer the reductions on the most recently purchased items in stock.
 
Smoggie

Smoggie

Well-Known Member
Phil,

The approach to battery care that's served me well for years is:

  • Balance charge on a quality charger (I charge at 2C rate usually)
  • Minimise time that the batteries spend fully charged, where practical only charge immediately before use.
  • Keep batteries in a cool place, avoid leaving in car in direct sun etc.
  • If I dont use a battery I discharge to storage ASAP or if i plan to use the next day put in fridge
  • I store batteries as they come off the heli providing cell voltage is in 3.7-3.9V range


I think most of this is fairly non-controversial except maybe the fridge part. Some say that you shouldn't cool a fully charged battery below 10C, but my experience is it does no harm. I dont refrigerate the batteries i'm using on a week to week basis, though they are kept outside so they do see 'fridge like' temperatures at this time of the year.
 
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Heliman450

Heliman450

Well-Known Member
Hi Steve,

Thanks for the summary. We've touched on this elsewhere but it always helps to reflect on stuff like this.

I also have the option to use the cellar rather than the fridge. Like most things, it's walk the talk that counts. I promise to perform better in future.

What do you think of 18 months as the expected lifespan?
 
namaspilot

namaspilot

Member
Tony said:
Hello everyone, I made this video a while back, but had to redo it cause of some information that was on it. In this video, you will learn just about all you need to know about a battery. From the C rating, to the S rating to the MAH rating, and how it equates to amp draw that you can take out of it.

If you have any questions, please ask.

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Click to expand...

Hello Tony,

I have some very old lipos that I neglected to keep topping up on storage charge. I don't know if they are still good?? Should I buy new ones???

Lipo Batteries.jpg

Thank you
 
Tony

Tony

Staff member
If they are not puffed and still hold a charge I would say use them. If they are puffed, might want to look into new ones.
 
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