LiPo Battery Management

LiPo Battery Management

One of the greatest inventions in the history of RC hobbies is without a doubt the Lithium-Ion Polymer battery. The sheer power storage and output capabilities in combination with a brushless electric motor are something to behold. They revolutionized the sport.

Caring for and maintaining your LiPos however can be tricky. And dangerous. With great power comes great responsibility.

In the early days, pioneers like myself would buy the sickest LiPos and connect them to the craziest brushless windings I could find. I wanted to create rocket ships in foam form. 3D foamies that could hover, and accelerate vertically for days. And I did. But at the expense of my LiPos, and my pocket book.

In more recent years, hobbyists learned by experience that greater care need be taken with these batteries. If you want them to last, if you want to get your money's worth out of them that is. I ruined many of them in the past, but I have ruined far fewer in more recent years because of LiPo Battery Management.

Lets get to the tips I suppose:

Number your batteries

Unless you have psychic powers, you are going to need to number your batteries. Try to follow a sequential ID pattern. The ultimate method would be to start at ID#1 and increment by one for each new battery you buy. In the past I have numbered batteries by type/voltage. Starting at 1 for the 2 cells, then starting at 1 again for the 3 cell batteries. But in retrospect, stick with numbering all your batteries in sequence, regardless of type, voltage brand, whatever. It is easier to manage them.

I will provide a why by example:

You have a micro quadcopter, and a dozen 1 cell 230mah batteries to power it. Half of those batteries are a year old, the other half are new. The only way to monitor battery health is to know which battery is which. You cant decide after one flight if a battery is bad. LiPos are finicky, temperamental on a good day. Numbering them is the way to go.

Have a log book handy

In order to track battery health and weed out the weaklings, you need to keep a running log. Not so much flight by flight, but a record of battery flights that you deem to be sub standard.

If you notice power dropouts or shortened flight times, make a note of the battery number in your log. Drop in a brief description of the problem. Trends will emerge quickly following this method. You can identify faltering batteries and retire them in far less time than just winging it. If you are a racer, the last thing you need is a dropout in a race because of a weak battery.

Having weaker batteries does not mean you can't still fly them. You obviously need to dispose of a battery that has expended its usefulness, or is damaged, but it's just fine to fly them when they are a little old and tired. That's the magic of numbering them and logging. Since all of your batteries have a serial number, it's easy to remember that ol #22 and #12 are getting old and I shouldn't race on them. QED

Store your batteries at 3.8v-3.85v per cell

Huh? Yeah. It's a thing. Something I never did in the early days. I charged up my lipos to full voltage, put them away. I was ready to fly at a moment's notice. But this turns out to be bad practice. NiCAD, NiMh, Pb, you are good to go. Not LiPo batteries. Some report that even leaving a LiPo overnight at full voltage can damage it permanently. So what does that mean to me? It means battery management.

Most new chargers have a "Storage" mode. They automatically charge or discharge your batteries to be around 3.8 volts per cell. I read some really detailed data on the subject. My personal determination is that 3.85 volts is the optimum storage voltage for a lithium polymer battery.

I have always trusted HiTec, this is the best charger I have ever owned: The X2 plus by HiTec.

Don't discharge your batteries too far

The current data suggests that making sure your batteries are not discharged below around 3.5 volts per cell will extend the life of the battery drastically. I have experienced this. I learned very quickly that running them to their limits was proportional to their longevity. So how do you handle this one. Once again, battery management.

  • Set a timer - Using a timer will allow you to better manage the ending voltage of your batteries
  • Log times - Log each battery type's flight time so you know how long to fly your 500mah battery, for instance
  • Use an OSD - Run Betaflight or an OSD, having battery voltage at a glance will help manage batteries

If I have an OSD, do I need to time my runs?

The answer is yes. Despite the plus or minus nature of timing runs due to the differences is power usage. It is very helpful. Having a timer as a backup for your OSD is great. When you are flying like a crazed maniac, you may not be paying attention to the battery warnings or meters. Having a voice/audio timer will work as a great backup. I personally respond better to audio alerts, compared to OSD alerts.

Don't abuse your batteries

This is a no brainer. But remember those "Oldies but Goodies", yeah, abuse them if you want. The gentler you break in and run the new ones, the longer they will last, and the longer you will get usable power out of them.

Never Charge Damaged LiPos

I, once again, learned this one the hard way. If you have ever blown up a lipo. Don't. I fly a lot of 3D aerobatics, at ground level. I have smashed lots of batteries into the pavement. They are pretty tough batteries, but you need to make a hard judgement call based on denting.

Depending on the severity of small dents you may be able to continue using a damaged LiPo without incident. But as I said it's a judgement call. Were talking tiny dents. Once they get beat up good. Dispose of them. Once they start charging, and puffing up, it's over. Always charge in a safe place. The ammo box cans work well, but the LiPo charging bags scare me a bit. I personally opt to charge on concrete out in an open area away from flammables.

Putting it all together

In order to best manage your batteries, you need to better manage your flights. If you could keep the LiPos charged all the time, there would be no need to manage your flight events or times. Call it planned hobbying. I know I have a race on Tuesday at 7pm, so that means I need to charge up my set at about 5:30, so that I have enough time to drive to the race. Easy. More planning than managing I suppose.

Matching energy in to energy out: This is fun, and pretty handy. If you are logging, and paying attention to how many volts/amps/power you expend on all your RC equipment you can use the following technique to save you time, and extend the life of your batteries. Another example perhaps?

After work I like to fly 6-12 1s batteries on my micro FPV. So when I get home I charge up my 2s goggle battery to be 4.0v per cell, and fully charge all 12 1s batteries. I then fly 12 runs timed to end at 2 minutes.

After the session, I let the batteries cool, and them put them on the chargers. BAM. The big 2s lipo is running 3.85v a cell, and the 12 1s batteries range between 3.77 and 3.82 volts. Walla. I just flew down to storage voltage and I'm pretty much ready to put my gear away for the night.

Granted, I could have flown longer, down to 3.5v per cell, but I have 12 batteries, limiting myself to 2 minutes instead of three saves me time charging up to storage voltage. And extends the life of all of my batteries.

The big 2s, since only charged to be 4.0v per cell, had exactly enough power to fly my 12 batteries. That's battery management. By comparison, if you charged up a huge 3s to run you goggles, you would need to put in in storage and discharge a bunch of power out of it to store it.

Doesn't that seem like a waste? Not only a waste of electricity, but a waste of LiPo power that could better be used in flight, after flight, after flight.






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