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Storage charging method question

#1
Hey guys, 1st post here. I just started this amazing hobby due to the quarantaines/lockdowns (more free time).

I fly my batteries till they reach 3.5v, with a voltage buzzer, so as soon as it starts beeping I land and swap the battery. When they cooldown they usually end up between 3.60-3.70v.
My charger has storage mode and it leaves the batteries at 3.8v per cell as it supposed to be, but, and here is my question, even if I charge them from 3.60 or 3.70v it takes almost the same time as charging them all the way. I have been following the voltage and the charger usually puts them over 3.86-3.87 (never more than 3.9v) and then discharges them to 3.8v.

Is this normal?
 

BATTLEAXE

Well-known member
#2
Welcome to the hobby and the forums. Its awesome to see you are already up and flying, most beginners come in absolutely green, like myself at one time.

The batts are good to drop to 3.5-3.4, however if you have a situation where you need to get out of trouble for another go around, you may be pushing it depending on the circumstances. I like to fly mine to 3.8, that way there is some reserve. And if the reserve isn't needed, then the batt is already at storage charge.

Your charger though you said it wont charge past 3.9? That is odd, it should go to 4.2. If thats the case then i do have to ask what your flight times are like? A couple mins?
Most chargers usually have a way to set the charge voltage if you need to change it. It might be set low, 4.2 is what you want for a full charge.

You should get around 5 mins or more easily if the power system is reasonable for the plane. What plane are you flying? What is the power system you have?
 

Hai-Lee

Old and Bold RC PILOT
#3
The old battery argument AGAIN!

I still have batteries in service that I purchased over 2 years ago and they are still within 90% of their original capacity.
As a battery only has a set number of cycles in it and each charge and discharge cycle generates some heat and reduces the battery life I treat my batteries very differently, (and nor so do my students).
We chill our batteries before charging and we NEVER use storage charging UNLESS we are not the use the battery for a year or more.
After charging we keep our batteries in the refrigerator at around 4 degrees Celsius.
We always chill our batteries before charging and only ever balance charge and we also never charge a warm battery or run our batteries to where they are actually hot.

Nett result is that we only buy battery replacements every 2 or more years unless we damage them in a crash or the like.

I got my students to have 2 sets of batteries and one was treated as I teach and the other was following the standard practices. The batteries that were subject to standard practices needed to be replaced after 12 months whereas the chilled ETC batteries were still going strong at 2 years. My students all now chill their batteries religiously.

Please note; I live in Australia with a sub-tropical environment and so battery heat is a definite battery killer, (even at storage charge).

Just what works for me!

have fun!
 

PsyBorg

Wake up! Time to fly!
#4
It all depends on your battery choices. The lower c rated packs fixed wing pilots fly are more susceptible to damage from excessive heat, mismatched chemistry, brand.. etc.

Sounds like you are doing pretty good at managing their use. Things to think about.. if your packs are always coming down feeling more then slightly warm to the touch they are being degraded with each flight and will shorten the life span little by little. Again this is where brands and types of packs comes into play. Some handle this better then others. As they need replacing over time like all batteries will consider buying a higher c rated pack and you will find heat management less of a problem.

As for the storage voltage thing it is normal the "intelligent" chargers charge to 3.9 to 4.0 V and then drop them back to 3.8. This is to balance the pack better for longer term dormancy. "Balance" charging is not so picky as that is the usual method to cycle packs to fly again so the tolerance between cells may not be so tight to conserve time on charge. The time it takes to do any type of charge being the same is that it defaults to 1c charge rate and they dont discharge as hard as when under actual load. All done with that thing called maths and if you are like me we dont do maths on the weekends. :LOL:

Bottom line sounds like you are in a good practice with your packs the only other thing I suggest is for long term storage or transportation in general is to keep them in a protective case. I use plastic canisters from sunflower seeds. These are PERFECT to hold 5 of my 3s 450 mah packs for my gremlin, 2 4s 850mah packs for my 3 inch quad, or any of my 4s or 5s larger packs for my 5 inch quads. They sit nice and protected on a shelf, into my back pack, and stay safe from accidents at the field or at home.
 

Bricks

Well-known member
#5
I find on my charger that if the charger has to lower the voltage to storage charge it will be a bit lower then if the battery is below storage charge the voltage will be a tad higher when done going into storage voltage.
 
#6
Welcome to the hobby and the forums. Its awesome to see you are already up and flying, most beginners come in absolutely green, like myself at one time.

Your charger though you said it wont charge past 3.9? That is odd, it should go to 4.2. If thats the case then i do have to ask what your flight times are like? A couple mins?
Thanks! It took me a good amount to tries and repairs to finally enjoy and fly hehe. But I'm pretty thorough and everytime I get into something I spend hours and hours learning and reading.
I might not explained correctly. I can charge my bateries and balance them perfectly to 4.2, is just that if I select storage mode, it charges them above 3.8 first, and then discharges them to 3.8. Another fellow just answered below that this is the normal behaviour of these "smart" chages, so that's what I needed to know :).

I'm flying a custom plane I found in youtube and mixed with some flitetest parts (the rudder and stabilizer for example). It's about 450g with a 800mah 3S + 1806 2280kv motor + 6.4 prop. It took me a while to find out the best combo hehe.

The old battery argument AGAIN!

I still have batteries in service that I purchased over 2 years ago and they are still within 90% of their original capacity.
As a battery only has a set number of cycles in it and each charge and discharge cycle generates some heat and reduces the battery life I treat my batteries very differently, (and nor so do my students).
We chill our batteries before charging and we NEVER use storage charging UNLESS we are not the use the battery for a year or more.
After charging we keep our batteries in the refrigerator at around 4 degrees Celsius.
We always chill our batteries before charging and only ever balance charge and we also never charge a warm battery or run our batteries to where they are actually hot.

Nett result is that we only buy battery replacements every 2 or more years unless we damage them in a crash or the like.

I got my students to have 2 sets of batteries and one was treated as I teach and the other was following the standard practices. The batteries that were subject to standard practices needed to be replaced after 12 months whereas the chilled ETC batteries were still going strong at 2 years. My students all now chill their batteries religiously.

Please note; I live in Australia with a sub-tropical environment and so battery heat is a definite battery killer, (even at storage charge).

Just what works for me!

have fun!
Thanks for the tips!!
Right now my usual ritual is, charge the batteries to 4.2 the day before flying. I have my buzzers setup at 3.5, so as long as it beeps I put the plane down (I haven't had any issues if I have to do a couple more circles if I can't land right away) so they usually end up between 3.6 and 3.7.
Go back home, and either charge them back to 4.2 if I plan to fly next day or charge them to storage voltage if the weather forecast is bad. No issues up here with the warm weather (sadly) hehehe (Canada).

It all depends on your battery choices. The lower c rated packs fixed wing pilots fly are more susceptible to damage from excessive heat, mismatched chemistry, brand.. etc.

Sounds like you are doing pretty good at managing their use. Things to think about.. if your packs are always coming down feeling more then slightly warm to the touch they are being degraded with each flight and will shorten the life span little by little. Again this is where brands and types of packs comes into play. Some handle this better then others. As they need replacing over time like all batteries will consider buying a higher c rated pack and you will find heat management less of a problem.

As for the storage voltage thing it is normal the "intelligent" chargers charge to 3.9 to 4.0 V and then drop them back to 3.8. This is to balance the pack better for longer term dormancy. "Balance" charging is not so picky as that is the usual method to cycle packs to fly again so the tolerance between cells may not be so tight to conserve time on charge. The time it takes to do any type of charge being the same is that it defaults to 1c charge rate and they dont discharge as hard as when under actual load. All done with that thing called maths and if you are like me we dont do maths on the weekends. :LOL:
And thank you too. That was what I was looking for. At this moment when I land the batteries are slightly warm, not hot at all. I have one big lipo bag where I store my 6 batteries but I just ordered a few small bags more to separate them between each other. I have read a lot about how delicate these batteries are and I don't mind expending a few hundreds bucks to prevent any accident.
 

Hai-Lee

Old and Bold RC PILOT
#7
After a days flying WE chill our batteries before charging and ALWAYS balance charge.

One of my students told me lest week that one of his batteries he had not used for almost a year, (left fully charged in the refrigerator all of that time), still had about 90% charge when he pulled it out to use finally. After a quick balance charge he used the battery and it was the same as new!

I recommend that you find out what works in your area. By the way, NEVER freeze you battery as it will cause damage.

A benefit of the chilling is that we do not have any "Puffed" batteries, even after 2 years!

Have fun!
 

PsyBorg

Wake up! Time to fly!
#8
I treat my packs like a redheaded step child most times. I regularly pull over 115 amps from them. Sometimes spikes as high as 150 amps. Have yet to puff a pack since I started flying proper c rated packs for what I use them for. I do however make a conscious effort to not exceed getting below 3.2 to 3.3 volts per cell although it does happen on occasion.

I believe its how you break in a pack is what determines its longevity due to gradual activation of the chemical process. The only puffed packs I ever had were ones I did not spend the effort to do so. I cant say for sure as they were also lower c rated packs so that change could also contribute to why I dont puff packs.

I tried that refrigeration thing and never found proof of any significant effects for doing it either good nor bad. I dont fly in weather below 40 degrees F as I have seen that degrade packs quickly. I have had packs heat up enough to get my attention when touching them but with regular monitoring of internal resistances I have not seen too much variation beyond normal changes.

I have packs easily over 2 years old maybe a few with over 500 cycles on them by now. It boils down to how often you over drain them and I think that is where the chemistry changes happen most which effects the internal resistances.
 

Merv

Well-known member
#9
I have been told buy a battery manufacture rep, that it is a good practice to let a battery rest a minimum of 15 minutes, from flight to charge & from charge to flight. This rest period, lets the internal chemistry equalize. A longer rest period is better.

I also get shorter flight times in cold weather, what would normally be a 10 minute flight is 6-7 in cold weather.

I don't think there is anything magic about the 3.8v/cell for storage. I believe it is important not to store a battery fully charged or allow one to fully discharge. 3.8v is just half way in-between.
 
#10
I abuse the snot out of my batteries. Chances are they are going to meet their demise via impact rather than me not storing them correctly. LOL... (like killing a really nice, high C battery on maden by impacting it full speed on to asphalt)

I have had batteries that I took the best of care that died rapidly. (Sir Puffs Alot comes to mind) I have had batteries that I abused which are still good even though they should not be. (One that has been over-discharged while running full C+ till it just wouldn't fly any more.)

I still try to use the best practices people have listed above.