LIPO Capacities

[Cbd23]

Hi I am somewhat new to the LiPo battery world and I have a question on how the capacity ratings work with LiPo batteries. With a good NiHm battery its easy to see that when I charge a dead battery it charges up to near or just over the rated capacity of that battery. I have several nihm batteries that all charge up near to or just above their rated capacity. However, I now have picked up several lipo batteries and when I charge them up, none of them even come close to their rated capacity. I understand that a lipo battery doesn't discharge all the way empty, so there is always some level of capacity still left on the battery.

This leads me to my question... Is the rated capacity of a lipo battery the amount of usable storage, or is it including that amount that is un-usable or below the 3.2 volts? If it is including that amount, approximately what percentage of the rated capacity of the battery should I expect to see?

For example, I have a 2S 5200 mah lipo battery and I if I discharge it to around 3.2 to 3.6 volts, it only charges up with about 2500 to 3000 mah, which is way short of the rated 5200 mah. I also have a 3S 5200 mah battery that when charged from 3.2 volts only charges up somewhere in the 3000 to 3800 mah range. Is this normal, I would think a 5200 mah battery would have a usable 5200 mah?

[tapped-out]

I look @ the voltage on my lipo packs when I charge them my 3s packs hit 12.60v when fully charged. Far as MAH I have no answer for you. From what you stated sounds like mah is rated on a fully charged battery and we truly never use all the MAH of a battery.

Something else I'd suggest is after you run your lipos batteries and don't plan on using them for a few days use storage charge on your batteries this will set voltage on a 3s to 11.40v and help life of battery.


Found this on the interweb

The capacity of the battery in milliamp-hours (mAh). A fully charged 2200mAh pack is rated to provide a current of 2200 milliamps (2.2 amps) for one hour before it is fully discharged. This capacity value is completely independent of how many cells are in series. In simple terms, the capacity value allows you to estimate how long a battery will provide useful power in a given application. In practical terms for RC use, the capacity rating is typically only helpful for rough comparisons of different batteries. i.e. a 2S-5000 battery will provide about double the run time of a 2S-2500 lipo in the same RC car.


Not sure if this helps you.

Sent from my SM-J737V using Tapatalk

[rkj__]

Good question. There is a lot to learn about LiPo batteries. I'm still learning myself, so I look forward to seeing the answers to your question.

I know with 12V lead-acid batteries, only about 50% of the rated capacity is recommended to be used, but that's hardly relevant to this discussion.

[colbynobo]

So far, after a number of years of being careful I have yet to have any serious LIPO incidents. One key for me has been to use quality chargers and put faith into their ability to manage the charging duties. I've noticed that the mah numbers don't always seem to jive and that voltages seem to be more important. For instance, 2S 5400 mah batteries may show that during the charge cycle 4000 mah was added to get it to 8.4V. Considering the battery wasn't even run to low voltage protection the numbers don't match up since there's no way it started out with only 1200 mah. I've seen this behavior consistently over the years with several different chargers and several different batteries. Since none of them have ever been damaged and the voltages match up to what I expect, I just accept that the chargers are smart enough to do their job and do it well.

[Cbd23]

I understand the voltage ranges and storage requirements for lipo batteries and I do have a smart charger that can handle these tasks. It is a touch screen HTRC T240 charger, which I hope is a good charger. So far it seems to be working well. My batteries have been working as they should as well, I just wasn't sure if I was getting what I paid for or not on the capacity side of things. The 2S 5200 mah lipo doesn't seem to give my any more run time than a good 2000 mah nihm on my crawler. It does give it more power though.

[allanon1965]

In my experience, there is a big difference in total capacity and Usable capacity. Nimh has more usable capacity than a same size lipo does. The relative point is at what level of performance do you call a nimh done, even if its not totally dead?

[Jim85IROC]

How much total current you get out of a Lipo will depend on what voltage you have your cutoff set at. Generally I like to run a 3.6v cutoff, and with that, my newer batteries typically will take just over their rated mah when I charge them. My older batteries will take a little less than their rated mah.

[Cbd23]

Originally Posted by Jim85IROC

How much total current you get out of a Lipo will depend on what voltage you have your cutoff set at. Generally I like to run a 3.6v cutoff, and with that, my newer batteries typically will take just over their rated mah when I charge them. My older batteries will take a little less than their rated mah.

That's exactly the information I was looking for, Thanks! So i've been discharging my batteries to down around 3.3 to 3.6 volts and depending on which battery, 2s or 3s, they are only charging up to between 2500 to 3500 mah. All 3 of the batteries are rated 5200 mah. Am I discharging them too low? From all the research i've done, most say don't go below 3 and to stay slightly above 3. I have the alarm set at 3.3 but usually quit driving around 3.6 or so. Should I be sending the batteries back? They are all new. One is a Zee 5200 mah 3S lipo and the other is a cheap Enegitech 5200 mah 2S battery. I sent an email about this to enegitech and they responded quickly by sending me a new battery, but the new one has the same issue as well as one cell that won't balance charge properly.

[lonleycreeper]

That is the definition of bad batteries.

Are you checking resting voltage?

The problem with lipo's is they bounce back after resting for a moment. Really just a moment.
I have discharged the batteries too low before and it really shortens their life. A good resting discharge should be 3.7 or above per cell. The fact that you are putting so little mah back into your cells tells me they have a very high internal resistance, causing low power and short run times. My 2000mah 2 cells go further than my old 3000 mah nimh's And my 2200 mah 3s go as far as my 4000 mah 2s lipo's. Distance driven on the same trail in similar conditions in the same truck.

[mewalsh100]

This is a great, budget friendly tool to do quick checks on LiPo balances.(roughly $20) I use the chit out of it. If you're out of bounds, just leave it plugged in to a pack to bring your balance back.

[WHITE-TRASH]

I run my lipos down to 3.2 volts per cell and they all charge back up to full labeled capacity or higher. The only time they stop short is when I only use part of the pack.

I use this lipo checker, it gives all the pertinent pack info including % of charge.

https://hobbyking.com/en_us/cellmast...h-checker.html

[Cbd23]

Originally Posted by lonleycreeper

That is the definition of bad batteries.

Are you checking resting voltage?

The problem with lipo's is they bounce back after resting for a moment. Really just a moment.
I have discharged the batteries too low before and it really shortens their life. A good resting discharge should be 3.7 or above per cell. The fact that you are putting so little mah back into your cells tells me they have a very high internal resistance, causing low power and short run times. My 2000mah 2 cells go further than my old 3000 mah nimh's And my 2200 mah 3s go as far as my 4000 mah 2s lipo's. Distance driven on the same trail in similar conditions in the same truck.

Maybe I'm not fully understanding your question about resting voltage. I have two vehicles i've used the batteries in, one is a redcat racing terremoto 10 which is set up brushless and comes with a lipo battery. I'm pretty sure it has a cutoff in it so it stops working once the voltage drops. My other one is a mad torque crawler that i use one of those cheap lipo alarms. On that one I just drive until it beeps, but usually I stop before it ever beeps cause we get tired of driving. At that point its usually slightly above 3.6 volts. I've only used the 3s battery in the terremoto and the 2s in the crawler. The only abnormal thing i've noticed is that the alarm almost always goes off prematurely at just above 3.7 volts. I pull the cover off, unplug the alarm and plug it back in and it resets back to the 3.7 volts but doesn't beep. I ensure the cutoff is still set at 3.3 volts and then keep driving. I've actually never made it drop down to 3.3 on the alarm. I've probably only used the 3s battery about 5 times and the 2s battery maybe 3 times.

[Cbd23]

maybe i've discharged the 2s battery too low based on the resting voltage, but this has only happened 2 times and the initial charge of the battery was still way below the rated 5200 mah. Again, the 3s battery has only been used on the terremoto car with the built in cutoff.

[WHITE-TRASH]

You aren't discharging the packs very far.

If you pour out half of the liquid in a gallon pitcher why are you surprised it only takes 2 quarts to refill it?

[DRTMI]

Originally Posted by Cbd23

Maybe I'm not fully understanding your question about resting voltage. I have two vehicles i've used the batteries in, one is a redcat racing terremoto 10 which is set up brushless and comes with a lipo battery. I'm pretty sure it has a cutoff in it so it stops working once the voltage drops. My other one is a mad torque crawler that i use one of those cheap lipo alarms. On that one I just drive until it beeps, but usually I stop before it ever beeps cause we get tired of driving. At that point its usually slightly above 3.6 volts. I've only used the 3s battery in the terremoto and the 2s in the crawler. The only abnormal thing i've noticed is that the alarm almost always goes off prematurely at just above 3.7 volts. I pull the cover off, unplug the alarm and plug it back in and it resets back to the 3.7 volts but doesn't beep. I ensure the cutoff is still set at 3.3 volts and then keep driving. I've actually never made it drop down to 3.3 on the alarm. I've probably only used the 3s battery about 5 times and the 2s battery maybe 3 times.

That is going to depend on your lipo alarm. The ones I use will go off when ANY cell just touches your alarm voltage. If your motor and ESC put a big enough demand on your battery, it can make the battery voltage and sag to your alarm threshold or lower.

You will greatly increase the useful life of your lipo's by not letting them discharge too far. I use 3.5 volts for my cutoff.

[Cbd23]

Originally Posted by WHITE-TRASH

You aren't discharging the packs very far.

If you pour out half of the liquid in a gallon pitcher why are you surprised it only takes 2 quarts to refill it?

When I plug the battery in to charge it's reporting a voltage around 3.6 volts and lists a capacity of around 7%. This is the case for the 2s lipo. Maybe the cutoff on the terremoto is quite high as well and thus the lower capacity on the 3S as well?

[Browneye]

Originally Posted by WHITE-TRASH

You aren't discharging the packs very far.

If you pour out half of the liquid in a gallon pitcher why are you surprised it only takes 2 quarts to refill it?

^^This.
Your 'smart' charger, if it's a proper lipo balance charger, will put all cells evenly at your peak set voltage. I choose 4.16 for standard, 4.3 for high-volt graphene packs. Resting, or storage voltage should be 3.8 to 3.85 per cell.

For best lipo life, and lots of cycles, total discharge should be greater than 3.2, never below, and higher is better, and peak charge should never be more than 95%, 90% is better. You'll get the most cycles out of your packs and helps to prevent puffing. If they puff up don't use them - dispose of them properly - which is a whole 'nother topic altogether...something about a bucket of saltwater.

Ideally charging and discharging should be measure in energy in or out, as in amp-hours or milliamp-hours, but since that's hard to do with simply hooking up and go, all of the chargers use voltage measure as a level of charge. Which works pretty well for what we need out of these packs. And that's why everything is measured by voltage level.

Ideally you also only use 1C of amperage for charging, or 1ah for each 1000mah of capacity. So a 5000mah pack should be charged at 5amps max. Most lipo packs will survive higher amps, some are even marked for charging 'C' rating, which can be higher. But most of don't have a charger than can even do that. And for best life the 1amp for each 1000mah of capacity is a good rate. Most chargers discharge at about 2amps. Some of those big packs can take quite awhile to discharge.

And new packs should really be charged to 90%, and charger-discharged at an amp or two - whatever your built-in discharge is, back down to 50%, and repeated for four or five times. It's like lightly exercising it, but what it's really doing is conditioning the pack chemistry itself. Most users report longest pack life with these processes.

A high quality lipo charger should pretty much do all of this for you in the way it's programmed. And there's a ton of info out there on the interwebs about lipo care. The airplane guys are WAY more fussy about their packs, and for good reason - if our motor quits we stop. If theirs quits they could lose a multi-thousand dollar aircraft or helicopter out of the air.

[WHITE-TRASH]

Originally Posted by Cbd23

When I plug the battery in to charge it's reporting a voltage around 3.6 volts and lists a capacity of around 7%. This is the case for the 2s lipo. Maybe the cutoff on the terremoto is quite high as well and thus the lower capacity on the 3S as well?

I'm guessing your charger is rather conservative to call 7.2 volts 7% capacity unless you have it set of lihv packs which run 3.8 nominal.

I just charged a basic 2s shorty 4000 pack the other night and my charger read 6.98 volts and the pack took just shy of 3900 mah before I cut it off since I was headed to bed. I only balance charge and I charge most packs at 5 amps since the majority of my packs are graphene that call for up to 10c charge rating. Basically I'm charging at less amperage than allowed and still getting full capacity.

Something is funky somewhere in your setup, be it charger or lipo alarm.

[durok]

Charger: Dynamite Passport Ultra (don't laugh, it was my first LiPo-related purchase a couple years ago, works fine)

Battery: Goldbat 3S 55C 6000mAh LiPo (budget Amazon purchase, third charge from new)

Charged at 1C rate from storage charge of 3.84v per cell

49 minutes later, it shows 4100mAh and 12.54v, 4.18v per cell, 20mΩ resistance.

Next I'm charging a trusty older SMC 3S 40C 4300mAh pack at the same rate from 3.87v.

I'll edit this post with the results.

EDIT:

38 minutes, 1658mAh, 12.54v, 4.18v per cell, 35mΩ resistance.

[Voodoobrew]

You should realise as you increase the voltage to the motor you also increase its ability to pull more amperage.

The amperage rating on lipos is how many amp hours that take you from 4.2 volts to around 3.2 volts per cell.