Balancing Severely Out of Balance A123 Pack

The following is a recent exchange discussing some charging logic that is impacted often by time-out settings in chargers. Not a bad thing all in all. The same logic can be applied to Lipo packs as well.

Hi, Dave:
Here’s my situation: All of my A123 batteries came from you and I’ve got several. All of them (except 1) work perfectly and I enjoy being able to take advantage of all that A123 batteries have to offer. My one that doesn’t work properly is a 2300mah, 2S receiver battery that I can’t get to balance. I charge it on a Turnigy Accucell-6 with the cutoff voltage set at 7.2 volts. My charger timed out at 120 minutes with one cell at 3.6 volts and the other at 3.25 volts. When I first started using these batteries, I was negligent about balance charging and would as often as not, just quick charge them and go fly. So, this is not a warranty question at all, but one as much for my knowledge as anything. First of all, is this battery safe to use (as a receiver battery), and second, is there anyway to get the second cell back up to voltage? I’ve cycled and balance charged it probably 3 times trying to get it to respond, but nothing I know to do has worked. I guess I could used it on an electronic ignition where sudden failure wouldn’t likely be as catastrophic as losing receiver power. What is your recommendation?
Thanks,
Steve

When balance charging, the first cell getting up to 3.6V causes the charger to start stepping down the charge rate. Ultimately, the charger cannot go over the maximum dissipation rate of your balancer. In other words, if it can only dissipate 100 mah, then the charger will drop back to 100 mah. It’s charging the pack at 100 mah but at the same time discharging the full cell at 100 mah to keep it from going over 3.6v. If the low cell is 1000 mah behind, in the two hours of the time out, it will only be able to bring the lagging cell up about 200 mah. It will still be lagging by 800 mah and some measurable voltage difference will be the evidence. Because the charger times out and stops working, your still out of balance.

Procedure options:

A. You could just keep repeating a 100 mah charge rate and let it time out 4 or 5 times.

B. You could also go into the setup and disable the time out.

C. There are some safety concerns with both “A” and “B” above. The best and quickest method that we use at our shop is to connect the charger through the balance port to only the low cell. You can do this through the standard XH balance connector by taking a JR or Futaba RX charge cord, crack off the outer shroud exposing the two pins. These two pins will be .100″ apart, just like those in the balance harness. Plug the bullet end of the cord into a volt meter, plug the business end into the balance harness, probing the different combinations. In the case of a 2 cell RX pack, you’ll only find 2 combinations. Offset to the black wire and offset to the red wire. One of these will read about 3.6v (the full cell) the other will read 3.25v (in your example, it’s the low cell). When you find the low voltage position, carefully pull the banana plugs out of your volt meter and plug into your charger. Set the charger to charge 1 LIFE cell. Set the rate (for a 2300 A123) to something between 1 and 2 amps (we don’t want to overheat the delicate balance connector) and let it charge that individual cell through the balance harness until it’s full.

When it’s done, both cells should be at similar voltage.

If you want to get really fine, there could be a slight calibration difference between your charger charging a single and a two cell pack. To really refine it, reconnect the pack to the charger as a 2 cell pack in the conventional way. Put the charger in discharge mode set at 2 amps. Let it take our 100 mah or so out of the pack. Then, switch back to Balance Charge mode and charge at 2 amps. Now the charger will put the 100 mah or so back in and at the same time balance both cells to each other. Since the pack is almost full, it won’t actually charge at 2 amps, it will read something lower. When complete, if the cells are good and the charger is working properly both cells should be very close.

It is possible the cell is bad. If this is the case, the above procedures and logic won’t result in a balanced pack. (presuming the charger is working correctly) It’s OK to repeat the procedure if you want to try again however, it’s likely your results will be the same.

If you are able to balance it successfully, do a discharge on the pack at capacity/2 or near. This is the standard for testing lithium type cells. So, a discharge rate of about 1.1 amps would be correct. Realistically the A123 2300’s should test within 50 mah of 2200 if they are in perfect condition. If the pack tests below 80% of 2200 (below 1760 mah) it should be replaced.

As to safety, I hesitate to ever say any battery is “safe”. I would say that if I could not get the pack behaving properly, I’d replace it. The cost of any pack is always a tiny fraction of the value of a model. It never makes you feel like a winner to put one in the dirt over saving a few bucks on a simple part, especially if you were suspect of it before you flew. Get it right, get confident or replace it.

Another safety warning here is you should be extra diligent when working with any battery where it’s condition is suspect. Do it outside and/or supervise closely. Never charge unattended inside a structure or vehicle. Always use a fireproof container for charging, especially when dealing with anything suspect.

If you follow through those procedures and that logic, you should be able to rule the pack in or out and have good confidence in your decision. Hope this helps you sleuth out the pack. Dave

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Is Daily Low Self Discharge Rate and Important Factor in RC?

A customer asking about an unusual cell size of ours asks: “Are they are low self discharge?”

They are not Eneloops which would be the only NiMH I would classify as Low self discharge. This is almost a silly thing to consider because we come off the charger and go to the field in this hobby. We do not charge a battery, then start a 1 week hike at the end of which we fly the model. That specification makes sense for a flashlight or an emergency radio, not an RC aircraft. Others may have a different view. I don’t fly unless I’m coming off a fresh charge at the beginning of the day. Other systems are to the choice of the users but reckless in my view. Yet I offer the Eneloops for those seeking this value. There are no Eneloops this small. Also, I don’t like the Eneloop under fast charge “ever” conditions.

For RC, lets go over how silly this is;

Standard self discharge x 2 would be only 2% per day.

After charging, if we let a 500mah pack set for 2 days before flying, it would lose (500x.01) 10mah the first day, (490 x .01) 9.8mah the second day. Value at end of 2 days 500-10-9.8=480.2mah. 19.8ma lost over 48 hours or about .416mah per hour dissipated.

If we come off the charger and go to the field, a trip that takes 2 hours, the same rate of loss would mean our pack would be about 499mah since we loose about .416mah per hour.

So, perhaps, a low discharge pack is good for about a .2% advantage when you get to the field. And, to come up with that .2% I had to exaggerate the loss by double and suggest a very long trip to the flying field.

This is why this specification is essentially moot when it comes to normal day in and day out use of receiver packs in RC aircraft. Is it better? We’ll yes in some microscopic way, but to get it, what are you going to have to do? Accept an Eneloop you can never fast charge? Use a non-Sanyo cell? I see a lot of effort hunting something that has no real measurable benefit in our application.

It’s more arguable in a TX battery because we often use that battery over a number of weeks between charges.

Dave

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Capitolist Buys a Plug In Hybrid? Ford C-Max Energi Part 3

You might wonder why a couple of proud capitalists would purchase a plug in hybrid car? The vast majority of media outlets never pass a chance to describe lovers of liberty and free markets as people who want dirty air and water. We reject their racist analysis. Racist? Ok, I’m taking lingual liberty. They certainly are drawing a circle around a huge group of people and saying “They are all bad like thus and thus….”. And, the statement is completely untrue. Perhaps racist isn’t the right word, however is it “news” if it’s delivered with a slant? No, it’s propaganda or opinion, not news. 😉

Anyway, we are to one degree or another technology nerds. Also, I’ve always had an interest in electric transportation. I’ve built some hot rod electric scooters that I use at shows. At the moment, I have some projects underway to electrify a classic mini bike. So, as a family, we have operational 3 forms of electric transportation.

A few reasons. I don’t like giving money to people that hate us. As an American, I consider it a matter of patriotic pride to limit my consumption of products imported from the Middle East. I like electric powered transportation and have always dreamed of building electric bikes, scooters, motorcycles and cars. My wife and I are technology nerds. It’s a cool car and technology is just fun to play with.

Not a reason: Man Caused Global Warming Hoax. This is a huge scam religion perpetrated by those wishing to weaken America (anti-capitalists), those wishing to take American pride down a few notches (can you name a few American Apologist Politicians?) and those in academia (scientists) who survive on money for government studies that seems to pour into any public panic. If you hate me for stating these things, don’t look up any data on rise of CO2 following global temperature rise, it will disappoint you in the so called scientists that signed the original report and Al Gore. CO2 does not drive global temps, it follows it. What warms the earth is (do you remember grade school?) is that gigantic ball of intense fire we call the sun.

I don’t need to make up lies or silly make-believe theory’s to justify being clean, thrifty or patriotic (my personal expression of one aspect of patriotism). Others may need a Santa Claus, I’ll stick to facts and logic. Hokey religions and Three-card Monte are no match for a good logic at your side, kid.*

*Hans Solo adaptation.

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Ford C-Max Energi Part 2

A full week on the ticker. Remember the very important point presented in part 1. That point was Ford says to wait at least 1000miles before making any mileage calculations. This implies there may be some break in mixture settings that prevent it from reaching it’s potential for a while. That being said, here are my shots of the data thus far.

Life Time Summary 01/06/13
Life Time Summary 01/06/13

Over 20 miles of driving on engergy generated from braking. 200 miles exactly in pure electric driving. The brakes are interesting. When you lightly press on the peddle, you get a braking action, however it’s really the generator robbing your inertia for energy to charge the battery. As you move down on the peddle you can feel there are about 3 steps in this level of braking (or level of power generation) which each step increasing in rate of power generation and braking force. If you don’t move your foot at all, you’ll come to a complete stop. Obviously, when you are barely moving (moment before you stop) there can be no electronic braking (or little) yet it feels just like the brake pads are stopping you. Some super-brain programming must be managing this and it works perfectly!

Ford C-Max Energi MPG & Miles 01/06/13
Ford C-Max Energi MPG & Miles 01/06/13

Shown here are total miles, state of battery charge and what remains of our first tank of fuel given to us by the dealer. Not bad, close to 500 miles and we have about a 1/4 tank left. Notice, I have changed the mileage calculation. It was at first combined with with electric power. I wasn’t interested in that figure. I wanted to know what we were getting per gallon of gasoline. So, that is now represented. It’s continued to climb all week and as you can see, it’s over 40mpg at this time.

Overall my impression of this car is a “fine ride”. Really enjoying the gizmo factor of playing around with an electric car. It’s as fine a ride as any luxury automobile I’ve ever driven. Comfortable, handles nice, great on the highway. Can’t wait for an excuse to take a long trip in it.

I did run into a couple of irritations this past week. When it comes to any kind of product manual or help file, it seems not to include “my” answer. While switching it from MPGe to MPG I encountered a wrench icon. A retangular yellow light with a wrench in it. Going to the bible like (thin pages and thick!) manual to look over the two pages full of warning icons, I could not find a wrench. Going to the glossary and looking up words like “icon”, “wrench” and “symbol” produced a big fat zero. I’ve come to expect that when I look into any kind of help file or manual. Is a black cloud following me? Probably not. Once I got the setting to what I wanted, the wrench never appeared again. Not sure what it was trying to communicate to me.

The second item is the foot actuated lift gate. It seemed to work iratically, opening partially then stopping at times. I discovered we were using it wrong, wiggling your foot back and forth under the bumper can start it opening and also toggle it to stop. Just sticking your foot under the bumper and pulling it out gets a reliable full open every time.

More to learn: You’ll notice in one photo, a full battery stating it has 12 miles range. We had read this car has about 20-22 miles on battery alone. I’ve still to figure out if this is part of a break in or what the reality is on final full electric range.

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Ford C-Max Energi Purchased Part 1

2012 C-Max Energi Plug In Hybrid
2012 C-Max Energi
C-Max Energi[/caption]It was time to purchase a new car. My wife and I are fans of Top Gear, a european auto show. On that show they don’t like many cars, however, they all love the Fiat 500 Abarth. We also liked the Ford C-Max. These cars do not have too much in common, however it was the two we were picking from. We finally decided on the C-Max Energi. (my Abarth dreams are still alive) Her previous car is a 2004 Honda Civic Hybrid. The Civic is 9 years old with a little over 100k on it. I currently drive a 2006 Dodge Mega Cab Cummins Diesel pickup. We have decided to keep the Honda as I have been averaging about $254 a month in fuel expense commuting to work each day. However, I need the truck to travel to trade shows and fly-ins so we’ll be keeping that. I just don’t need to be driving it so much. I am planning that by driving the Civic will save us about $127 a month in deisel fuel.

The C-Max comes in several varieties, we choose the “Energi” version. The Energi is a plug in Hybrid It has an EPA rating of 100 miles per gallon. The car contains a lithium ion battery and can go 10-20 miles on battery alone.

I plan to write in this forum about the C-Max and out experience with it.

When we picked up the car, the avergage fuel economy guage was reading 13.5mpg and it had 59 miles on it. (YIKES!)

One of the things that concerned us was the lack of people reporting fuel economy for the C-Max, both Hybrid and the Energi Plug In. The few that did report all reported less than EPA sticker mileage. Typical for the C-Max Hybrid (sticker 47mpg city, 47mpg highway and 47mph combined) was from 32 to 36mpg. That is alarming. However, these reports all seem to come from reviewers who have cars on loan for a day to film and make reports. Also, for photogenic reasons the driving almost always was in the hills and canyons of California or similar. Test speeds always seem to be 70mph plus. We don’t drive like that. Also, what does any reviewer or test driver do? They stand on that throttle to feel the power, they film passing, they film jack-rabbit starts, the test the handling. All things your likely to get tired of doing after owning a car for a 1000miles or so. What am I saying? You can’t trust the media here (like you can’t trust them anywhere). In this case, they don’t have an axe to grind, they have a report to finish. There is no axe to grind, just human nature. So, I’m anxious to see if I am correct or in error. Will the car do much better than previously reported?

Also, not reported by any report is the Ford’s manual which warns not to measure fuel economy during the first 1000 miles. The most accurate time will be between 2000-3000 miles. Having mechanical and racing experience (and a dose of healthy logic), I can assure you with todays computer controlled ignition and fuel delivery systems could easily be programmed to run a little richer for a better break in. The manual does not state it in that way and no research indicates they’ve done that. However, there is no research that indicates they did not either. So, we’ll follow the directions and give it the miles before we get too critical.

I wonder if any of the online reviewers of the C-Max Hybrid bothered to read the manual? Remember, these are humans.

Engergi Lifetime Summary 01/01/13
Engergi Lifetime Summary 01/01/13
We have the Energi version which is perported to get 108mpg in the city and 92 highway. Of course with an electric range limit of about 20 miles, I would presume most of your trips need to be very short with charging before each trip to acheive this mileage. My wife’s commute is 60 miles a day and most of that is Highway. I’ll be quite happy if she averages 60mpg. We are starting with the car in the winter which creates heating loads.

Mileage Data Shot 01-01-13
Here is our first set of guage photos. I’ll try to add these from time to time so you can see how the Energi is doing.

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High Cell Count Packs

Sonny P. Writes:

What is the proper way to charge a 14 cell A123 battery?

Sonny,
I take from your question that your concerned about the large cell count and not the rules of charging this particular chemistry of pack.

Since you need to balance it from time to time, it should be charged as multiple lower cell count packs from time to time. All rules must be observed regardless of cell count or type of lithium chemistry. So, were I building a 14 cell aircraft pack for myself, I’d build it probably as two 5 cell and one 4 cell packs. In this way I could hook up to my balance charger and balance it. If you have a charger capable of balancing 8 cells, you could do two sevens. I am un-aware of any chargers capable of balancing more than 8 cells even though there probably are chargers that could manage a non-balance charge of 14 cells. Even if you owned one, you’d still want to be able to break the pack down (electronically) and charge it in shorter segments from time to time to maintain balance.

In the case of two 5 cell and one 4 cell packs for example, The pack could be literally 3 packs that are put in series in the model. You might use Anderson Power poles to do this to minimize the number of connectors needed. Each pack would of course have it’s own balance harness for plugging into the node port (balance port) of you charger.

It would also be possible to build the pack as one 14 cell block with one set of output wires for the ESC. However, you could put tap wires in that are heavy enough for charging at the union between the 5th/6th cells and 10th/11th cells. You would build in balance harness respecting this same cell spacing. So that “electronically” (if not physically) you have 3 battery packs, two 5’s and one 4. NOTE! This type of pack bould, the central tap wires would be positive or negative depending on which segment you were charging.

With a 14 cell charger you might be charging through the main output leads while your at the flying field. Yet, when your prepping the model for a trip to the field, you would be able to charge the pack in 3 steps (one step for each pack division 5 cell, 5 cell, 4 cell) with balance harnesses connected to your charger. In this way you’d be getting regular balance charges to keep all cells equalized.

Happy Flying!
Dave

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Do A123 LIFE Packs Free Us From Cycling?

Dave
One more quick question. I ordered some 1100 2s A123 packs from you today.
Do these need to be cycled? I have a FMA 4S CellPro charger that is A123 compatible. It will charge and balance, but not cycle.
Thanks again.
IRL

 

Irl,

If you want to check them before flying, Yes.
If you want to find out when they go bad on the workbench rather than at the field, yes.

There is no skipping regular battery testing and maintenance regardless of battery chemistry. All battery types will fail eventually and discharge testing is the only chance to discover packs needing replacement before having an accident.

My answer might seem a bit strange, however, every time there is a new battery chemistry many modelers think the new “miracle chemistry” means the end of regular battery maintenance and testing. I got the question many times at the beginning of the NiMH revolution, the Lipo revolution and at the introduction of A123 Systems LIFE cells. There could be nothing further from the truth. There is never a time when battery maintenance and testing is not prudent.

No jab against the CellPro chargers is intended here. They are very good quality and I recommend them. I don’t know the specifications of all the models they sell but am aware some of them will discharge test packs. It is possible to discharge these in NiCad or NiMH mode on modern digital chargers as long as the mode has NO CHARGE at the end of discharge. In other words, as long as it’s not a “cycler”. A cycle is a full discharge then charge or full charge then discharge. To do this, we want to us a charger that simply does 1/2 the cycle, in other words we want it to discharge and that is all. Just set the (NiMH or NiCad) cell count to 4 for a 2 cell A123. Some let you set the cut off voltage directly and in that case, set it to 2v per cell or 4V for a 2cell A123 pack. The correct discharge rate for any kind of lithium is Capacity/2. They are rated over 2 hours. Since many chargers/dischargers only allow discharge rates at even .1 amp (100mah) increments, set discharge to 500 or 600mah (.5 or .6 amps) to do a reasonably accurate job on an 1100mah rated cell.

I’ve noticed over the years the 2300mah cell (26650 can size) generally cycles to 2100-2200 range. They seem slightly over rated. Don’t be alarmed if your 1100mah (18650 can size) pack tests to 1000 or 1050mah. It’s probably just about right.

Happy Flying
Dave,

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Battery Storage In Reverse

For many of us there is a winter storage season. How do we bring our fuel powered models out of storage confident our RX battery packs are up to snuff? Were they nearing the end of life at the end of last seasons flying? Did they survive being in the trailer or garage ceiling for a number of months? Here are important steps to greatly reduce your risk of shouting “I Ain’t Got It!” when you hit the field this spring. These recommendations are intended for NiMH and NiCad packs although the similar principals apply to any mission critical TX or RX pack regardless of chemistry.

1. You should have cycled your packs and noted the value on them when you put the model in storage. Did you do this? A simple round of cycling in the fall will help weed the weakest packs from the herd.

2. Check the purchase date on your pack prior to model reactivation. Did you date your packs? Noting the purchase date in permanent marker should be a routine with new packs. Has this pack made it 3 seasons already? If it has made it 3 seasons, it’s time to replace it with a fresh one even if it’s still cycling well. It never seems like a good deal to “squeeze one more season” out of a pack if a model is lost doing so. There are no battery experts in the industry, nor any magazine writers that are willing to dare recommending using packs beyond 3 years. Most recommend only 2 years. The incident of surprise failures increases with each season. It’s much cheaper “not” to find out how long it will take to have a failure. Think about it.

3. Similar to a new pack, a pack having been in storage for some time is in need of a slow “forming charge.” A forming charge is a simple full-to-overflowing charge on a non-peak detecting charger like your factory wall wart. While in storage the cells slowly discharge. Not every cell will discharge at the same speed. After a few months, you could have one cell at 80%, one at 60% and two at 50%. When form charging, It’s important the charge rate does not exceed 10% of the packs mili-amp-hour (mah) value when doing this procedure. This type of charge allows all the cells to fill fully and the first cells to fill won’t be overheated by the ongoing charge. The danger of peak charging a pack that has been in storage is the best cell (the 80% full one) can be ruined as it’s overcharged while the other 3 are still filling up. Also, your pack may false peak meaning that although the charger reports it is full, it really might not be. Re-equalize the cells with a good long slow wall charger charge prior to any peak charging to avoid most problems.

4. Test for Capacity. Discharge the pack on your favorite charger (with discharge function). For the purposes of this kind of test, the correct rate to test against factory rating is 20% or 1/5 of the rated capacity. It’s ok if you can’t get that setting exactly, just get it close. Example: A 1000mah pack would be tested at 200mah discharge. Most chargers will display this as .2A. Your pack should test at least 80% of it’s rated capacity. If it does not, then a few more charge / discharge cycles are in order. If you can’t get the pack to test above 80%, it’s time to replace it. Although it might seem like a money saver to succumb to temptation and overlook marginal packs, one crashed model will pay for a great many replacement battery packs. And that’s to say nothing of the risk to others when a model goes out of control. Good pack or no go!

5. When you recharge the pack after your final discharge test, check the charger input mah. Did it put in about the right amount? A pack that’s been in storage, particularly if you’ve skipped the step of re-forming it is very prone to a false peak. A great pack that tests perfect but only takes 50% of the expected recharge amount could cause some unwelcome excitement.

6. Test your Switch. First, use a loaded tester to check your fully charged pack directly. Note the value then test it through the switch harness. If it tests good directly but marginal through the switch, it might be a sign the switch is getting dirty internally, worn or perhaps some connectors are going south. Like battery packs, finding out how long a switch will last is costly knowledge to acquire. It’s a good idea to replace the switch with every other new battery just to avoid trouble. Load testing your pack with and without the switch harness looking for any substantial difference is a good way to detect a problem before starting the season. Did you notice what I omitted? After checking the battery through your switches charge lead or charge jack, unplug it from the RX, turn the switch to the “ON” position and check it again. Is it load testing similar to the charge jack/charge pigtail? The most important place for your pack to deliver it’s energy is to the RX. Make sure it’s solid to this point, not just the charge harness.

Integrate these practices into your seasonal routines and many common pitfalls are avoided. Don’t forget to scrutinize your TX battery in similar fashion. Ongoing TX function is every bit as important as RX functionality.

Dave Thacker, Owner: RadicalRC.com
Blogsite: Radical RC Workbench

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Doc Brown Power Supplies Checked For Possible HAM Usage

I’ve had several inquirys wondering if these power supplies can be used for Ham purposes. A local Ham checked one out and writes:

Dave …
I’ve used this with a Yaesu FT-817 (5 watt, around 2 amp), scanned across the bands, and found several places where there are “birdies” or RF that can interfere. It seems to be on the power line, since I had no antenna attached at the time.
1.805 MHz, 1.784, 1.685, etc. These likely come from the switching mode, since the signal disappears when the power supply is unplugged. I would suggest that HF ( from 1.8 MHz to around 30 MHz) may be usable on some bands, but not all. At VHF and UHF frequencies it is well filtered enough to use, that is at 140 MHz and 430 MHz. With its current level it could run a 100 watt repeater at VHF nicely.
Of course, this isn’t at the same level evaluation as someone at the ARRL or FCC labs, since I have not measured the actual level of signal involved. I can not see anything on the Tektronics oscilloscope, but it only goes to 2 mV/cm. A signal at that level would be rather loud.

John Hepner KA8ZSB

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RadicalCast #006

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We discusss: Bad weather strikes, flying field weather tips. Fun with Hover Craft! More On Form & Peak Charging. Using thread locker properly.

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