Charge batteries only to 80% = 4x more cycles?

[LyonNightroad]

Subjectively, from using 100s of batteries for RC planes, bringing the batteries down to 90-100% DoD is far more damaging and cycle reducing than charging the battery to 100% SoC.

I would say that only discharging the battery to 20% SoC (80% DoD) will give you 4x more cycles, not the other way round.

 

[Offroader]

Subjectively, from using 100s of batteries for RC planes, bringing the batteries down to 90-100% DoD is far more damaging and cycle reducing than charging the battery to 100% SoC.

I would say that only discharging the battery to 20% SoC (80% DoD) will give you 4x more cycles, not the other way round.

I kind of agree with this. I accidentally overcharged one of my 18650 cells and found that it easily has a lot more capacity above 4.2 volts. This means at 4.2 volts the cell isn't near full. I charged to 4.26 volts and I had 500 MAH more capacity in a 3400 MAH cell.


This is why they are coming out with lipo that takes 4.35 volts.

But at a low DOD, say 3.00 volts the cell has almost no life remaining.

What I think people have to understand is that it may be better to charge less and discharge less, but the benefits are so negligible that it isn't worth making a big deal over. I know someone who built a ridiculously big pack just so he can stop charging at 4.00 volts.

I found on my lipo charging from 3.7 to 4.1 volts that I only lost about 2% a year, my pack also sat in my hot garage during the summer which saw hot temps of 90-95F. I'm sure if I pushed my cells to 3.6 to 4.2, I would have maybe saw a 3% capacity loss. You see 1% a year is so negligible it isn't worth bothering about it. After three or four years I will wind up replacing the pack anyway, usually due to a new frame that requires a different size pack to fit.

Who cares about 4% capacity over 4 years. I would rather have had the extra 10-15% capacity during my rides, then have 4% extra capacity at four years.

 

[Hillhater]

Im pretty sure many users are mislead by looking at discharge curves and seeing how little time the pack spends above 4.0v, and they interpret that as suggesting there is little capacity available between 4.0 and 4.2 volts .
As a result of That, and reading scary comments like this thread title, They dont bother fully charging the cells to 4.2v and subsequently never take advantage of the full cell capacity.

 

[hydro-one]

took my 24s hk lipo hardpacks to 125v last night for a short time. my bike wouldnt run and i had to use a worklight to discharge below 119 so i could burn it off in the cromotor. i can personally attest --- there is alot of capacity between 4.2 and 4.5 volts!!!!!!!

 

[Hillhater]

..24S at 125 volts is 5.2 volts /cell ,!
I bet they were a little warm !
What are you charging with that has no voltage cut off ?

 

[Wheazel]

took my 24s hk lipo hardpacks to 125v last night for a short time. my bike wouldnt run and i had to use a worklight to discharge below 119 so i could burn it off in the cromotor. i can personally attest --- there is alot of capacity between 4.2 and 4.5 volts!!!!!!!

Trying to make a bonfire?

 

[flippy]

i had overcharged my S13P30 89ah pack due to a faulty BMS to 4.5v per cell (one cell was not holding charge) and i quickly made a string of 5 1 ohm 100w resistors and dumped them in a bucket filled with 10 litres of demineralised water and got it nearly boiling (86c) before the pack got below 4.2v.

the amount of power beyond 4.2v is quite big. but i know for sure my cells did not like it.....

 

[Ykick]

More than a few of us have likely pushed a little overcharge into RC Lipo from time to time. Not my proudest moment but I’ve purposely and carefully balance charged to 4.35V/cell and immediately rode the bike in order to maximize trip range.

After years daily use RC Lipo, I genuinely believe avoiding storage at higher voltages is the most significant “mojo/juju” for maximizing cycle/calendar life.

If I don’t need ‘em in the next couple hours ‘always let ‘em sit 3.5-3.9V/cell range.

 

[Uilleam Gilvoni]

Not fully charging or discharging a lithium cell will definitely extend its life.

Read this entire page at the "Battery University"

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

There are tables on this page to quantify the typical improvement you can expect.

To summarize the way to treat your lithium ion battery well........

1) Never ever allow them to get overheated - period. Heat is the enemy of lithium ion batteries!
2) Never 'hold' the battery at full charge (usually 4.2v) If you want to use the full charge capacity just top up the battery just before you want to use it.
3) Any reduction on the DOD (depth of discharge) will extend the battery life.
4) Avoid ultra fast chargers.

As for not charging a pack up to 100% and therefore not allowing the BMS to balance the individual cells to 4.2Vmax. I would only be concerned if my pack was made from 2nd hand cells of different makes/age. A pack made from the same cells do not tend to drift in my experience. Perhaps a full charge every 10 cycles will allay certain peoples fears?

I'm not aware of any downsides (damage) to cells that are charged to a level below 100% - if I'm missing something perhaps a link to a source of the information can be given?

#2. If I full charge my 48v 11.6ab dolphin battery and then leave it charged during the night and then use it in the next morning is ok or not?

 

[joss]

Yes - its fine. Batteries are made to be charged to 100%.....just as a 'rule of thumb' its good not to leave the battery long term/permanently at its terminal voltage. I use a timer plug to start charging during the night ready for the morning (makes use of cheaper electricity). However, some people would advise not charging 'unattended' batteries. Mine is in the garage, has a BMS and I don't have the bike up against anything flammable. Maybe I should fit a smoke detector in there.....might be a good investment!

 

[Offroader]

Yes - its fine. Batteries are made to be charged to 100%.....just as a 'rule of thumb' its good not to leave the battery long term/permanently at its terminal voltage. I use a timer plug to start charging during the night ready for the morning (makes use of cheaper electricity). However, some people would advise not charging 'unattended' batteries. Mine is in the garage, has a BMS and I don't have the bike up against anything flammable. Maybe I should fit a smoke detector in there.....might be a good investment!

What I want to start doing is if I know I am going to use my bike tomorrow at 1PM, I would start charging the day before at a very slow rate that would make it fully charged at that time. Like a 12 hour charge.

I wonder if this would actually be harmful somehow as the cells would be under a constant charge for so long.

 

[flippy]

No, a slower charge is better. High charge rates is the main killer in high capacity cells. Just look at an average iphone of about a year old, the battery will be shot after a year of fast charging and slow discharging.

 

[Offroader]

No, a slower charge is better. High charge rates is the main killer in high capacity cells. Just look at an average iphone of about a year old, the battery will be shot after a year of fast charging and slow discharging.

Agree, I thought I read where the battery will be under constant chemical change with a slow charge or something like that. So something not so slow and not too fast would be best.