HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Sep 06, 2014, 07:39 PM
Registered User
FredYates's Avatar
United States, OR, Lebanon
Joined Jul 2012
90 Posts
Discussion
Parallel Charging Facts - Part 2, Charge Applied, then Batts Plugged In

If you haven't read the first thread Parallel Charging Facts - Part 1 Batts Inserted in Harness, then Charge Applied I recommend you browse it first for some needed background information.

There are probably 64 different ways to parallel charging batteries, this is one more take on the Part 1 test I preformed using the same batteries, same initial conditions. The table below shows these results. Again from the table you can see that everything looks OK, except Batt 2 accumulated less charge than the other 3 batteries. The actual accumulation is down 4.6% from Part 1 testing. More on that later.



The first graph displays the discharge of all four batteries. Although the table shows the data, the graph makes it stand out. Compared to Part 1 data, there is a greater disparity between the discharge rates of Batt 2 and the other 3 batteries.



For the second round of tests I initialized the charging current first and then started plugging in batteries one by one.

The graphs look much different than Part 1 since there is no self charging and discharging occurring as the batteries are plugged in . The only downside is that the first battery plugged in is hit with the full charging current for a short period of time. If you aren't sure as to whether your battery can handle it, just set the current lower until you have all the batteries plugged in and then set it to the proper charge rate.



Use the labels and the colors to keep everything straight.
At Time 0 the charger is looking for batteries to charge the voltage is hovering between 4.08 V and 4.17V.
At Time 0.1 I plugged in Batt 1 and the voltage dropped to ~3.85V and crept back up to 3.9V.
At Time 0.4 I plugged in Batt 2 and the voltage dropped to ~3.84V and notice the current divided but not equally. Remember Batt 2 is on the weak side and has a higher IR.
At Time 0.5 I plugged in Batt 3 and the voltage dropped to ~3.81V and the currents split differently with Batt 3 hogging the current
At Time 0.8 I plugged in Batt 4 and and the voltage dropped to ~3.79V with the currents divided up by the different IR of each battery and its ability to accept a charge.

This next graph displays the charging current for all 4 batteries simultaneously over the entire charge cycle. Notice the charging current for Batt 2 is being hogged by the other three batteries, especially Batt 3 and Batt 4.



This graph displays the accumulated charging Joules for all 4 batteries simultaneously over the entire charge cycle. Notice that Batt 2 is considerably lower than the other three batteries. Comparing Part 1 charging Joules to Part 2 charging Joules you find it accumulated 4.6% less charge than during the previous charge cycle.



Conclusion:
The good news is using this method eliminates the batteries self charging/discharging problem as in the first scenario. Although the 100mA (Part 1) currents are not much concern, nothing is better than something. Remember these are older, 1S 550mAh batteries and have an IR in the high 10s of mohms (80+) compared to larger batteries which run in the low mohms.

The bad news is something is going astray with Batt 2. For some reason it is not accumulating charge like the other 3 batteries. In Part 3 I'll offer some data and insights while attempting to unravel the mystery of Batt 2.

Stay tuned for the next chapter.
FredYates is offline Find More Posts by FredYates
Reply With Quote
Sign up now
to remove ads between posts
Old Sep 13, 2014, 07:55 PM
Registered User
United States, NY, New York
Joined Sep 2013
158 Posts
Let me make a wild guess here:
Since battery 2 is "weaker" than the others, it likely has a higher internal resistance. When you apply a voltage to it while it is connected in parallel to other, "stronger" batteries with a lower internal resistance, the current through battery 2 is lower than through the other batteries. And since it's seeing that lower current for the same duration as the other batteries see their higher charging current, it receives less charge.
Or am I missing something, and there is indeed more to it?
getsuyoubi is online now Find More Posts by getsuyoubi
Last edited by getsuyoubi; Sep 13, 2014 at 07:56 PM. Reason: spelling...
Reply With Quote
Old Sep 13, 2014, 08:05 PM
Registered User
United States, NY, New York
Joined Sep 2013
158 Posts
I also don't see why this charging method is supposed to be better than the one in Part 1. Allowable discharge rates are way higher (typically >20C) than allowable charge rates (~1-3C, depending who you ask), so the discharge while connecting batteries in parallel before starting the charge process cannot be of any concern. The measured "self"-charge rates during the connection process in Part 1 are all below 100mA, which is less than half the intended charge rate (per battery) in Part 2. So, if the charge rate in Part 2 is safe for the batteries (which it is), those unintended charging currents of <100mA in Part 1 must be. I'm puzzled...
getsuyoubi is online now Find More Posts by getsuyoubi
Reply With Quote
Old Sep 14, 2014, 12:30 AM
Registered User
FredYates's Avatar
United States, OR, Lebanon
Joined Jul 2012
90 Posts
Quote:
Originally Posted by getsuyoubi View Post
Let me make a wild guess here:
Since battery 2 is "weaker" than the others, it likely has a higher internal resistance. When you apply a voltage to it while it is connected in parallel to other, "stronger" batteries with a lower internal resistance, the current through battery 2 is lower than through the other batteries. And since it's seeing that lower current for the same duration as the other batteries see their higher charging current, it receives less charge.
Or am I missing something, and there is indeed more to it?
One of the popular theories is "they will all equalize out if you leave then on long enough". The data shows that is not true. Whenever the dominant battery reaches the cutoff voltage the charger will stop regardless of the "needs" of the other three batteries. In this case Batt 2 is not being recharged to its full capacity during parallel charging.

If you open up the graph that runs for 120 minutes you can see in the CV mode Batt 2 is actually drawing the most current (admittedly very little more) during that phase and because it has a higher IR might actually be shutting down the charge cycle. If that is true, it is self defeating and will never reach full recharge. I am still grappling with what is happening and why Batt 2 is exhibiting this behavior.
FredYates is offline Find More Posts by FredYates
Reply With Quote
Old Sep 14, 2014, 12:36 AM
Registered User
So. Cal.
Joined Oct 2004
8,034 Posts
Quote:
Originally Posted by FredYates View Post
I am still grappling with what is happening and why Batt 2 is exhibiting this behavior.
Quite simply, one of a few things - It either has substantially higher internal resistance, a poor connection (single cells are notorious for poor quality connectors), voltage reading error due to separate Vmon circuitry, or it has a high impedance internal short that is bleeding current.

If the cell is challenging to reach full charge when charging in parallel, it will exhibit identical behavior when charging by itself at the same charge rate. As such, your artifact is not a result of parallel charging but rather due to bad cell or connection.
mrforsyth is online now Find More Posts by mrforsyth
RCG Plus Member
Reply With Quote
Old Sep 14, 2014, 08:49 AM
Registered User
United States, NY, New York
Joined Sep 2013
158 Posts
I agree with mrforsyth. I consider a bad connector as part of the internal resistance, since I would treat the battery with all its bells and whistles as a "black box".
However, there is probably more to it. I usually charge six MCPX batteries (1s, 300mAh) in parallel. From time to time, as these batteries are getting older, I notice that one of them doesn't seem to have as much charge as before, and the LVC of the heli kicks in at, say 3 minutes, while all other batteries last for the full 5 minutes of the flight. Charging this one bad battery individually for a few cycles seems to revive it, at least for a while. I have to admit that this does not seem to make sense, since this bad battery should cause the charger to terminate early (in terms of charge) due to its supposedly higher internal resistance, and therefore I don't even know why I ever tried to improve the situation by charging it individually - but it worked!
Parallel charging with this one bad battery in the mix did seem to terminate the charge early as well, as evidenced by the total charge displayed on the charger. This also surprised me, because as resistances add as 1/R_i when connected in parallel one high resistance battery out of six doesn't really change the overall resistance of the whole pack.
getsuyoubi is online now Find More Posts by getsuyoubi
Reply With Quote
Old Sep 14, 2014, 09:03 AM
Registered User
United States, FL, Orlando
Joined Oct 2013
186 Posts
What I gather from this is that batteries with different IR require different amounts of time to charge to the same level (when using the same current). Charging them all together does not change this behavior.

So the result of parallel charging is that batteries with lower IR compared to the group average will charge slightly more than those with higher IR.

The low IR batteries may only require 5 minutes of CV charging to reach the predetermined cutoff point while the high IR batteries may take 8 minutes, for example. When parallel charging, the CV stage may be averaged out to 6 minutes causing the charge discrepancy.

I am not sure that this is going to have a meaningful net effect on regular everyday parallel charging as I imagine you would need to have a pretty significant IR discrepancy to see any differences in charge state (and then the effects of high IR during discharge would probably be far more noticeable than the decreased amount of charge).

Also, if I am reading this right, the first chart is a capacity measurement, right?
It looks like Batt 2 just has a lower capacity than the others, unless I am missing something.
CerealKiller159 is online now Find More Posts by CerealKiller159
Reply With Quote
Old Sep 14, 2014, 12:44 PM
Registered User
FredYates's Avatar
United States, OR, Lebanon
Joined Jul 2012
90 Posts
Quote:
Originally Posted by getsuyoubi View Post
I also don't see why this charging method is supposed to be better than the one in Part 1. Allowable discharge rates are way higher (typically >20C) than allowable charge rates (~1-3C, depending who you ask), so the discharge while connecting batteries in parallel before starting the charge process cannot be of any concern. The measured "self"-charge rates during the connection process in Part 1 are all below 100mA, which is less than half the intended charge rate (per battery) in Part 2. So, if the charge rate in Part 2 is safe for the batteries (which it is), those unintended charging currents of <100mA in Part 1 must be. I'm puzzled...
I think what you have overlooked is that this is a very special case in that these four, old, 1S, low current batteries were discharged to within 0.002V of one another and they still managed to swap 100ma of currents back and forth.

I totally agree that 100ma is nothing to worry about for all the reasons you correctly stated. But in further testing, which I will share later, I have seen these same old batteries swap 1A back and forth until they are driven by the charger current. Again not dangerous, no big deal, but why do it?

To me, it makes very little sense to discharge something I am going to charge in the next minute. But then, I am an old geezer.

In my opinion, no current swapping is better than some current swapping and all you have to do is change the sequence in connecting the batteries and charger.
FredYates is offline Find More Posts by FredYates
Reply With Quote
Old Sep 14, 2014, 02:53 PM
Registered User
FredYates's Avatar
United States, OR, Lebanon
Joined Jul 2012
90 Posts
Quote:
Originally Posted by mrforsyth View Post
Quite simply, one of a few things - It either has substantially higher internal resistance, a poor connection (single cells are notorious for poor quality connectors), voltage reading error due to separate Vmon circuitry, or it has a high impedance internal short that is bleeding current.

If the cell is challenging to reach full charge when charging in parallel, it will exhibit identical behavior when charging by itself at the same charge rate. As such, your artifact is not a result of parallel charging but rather due to bad cell or connection.
I am afraid you are treating it too simply.

I do not have an ESR meter so I can not quantify the ESR of the batteries with any great certainty. But I do make measurements at 1 second intervals and can "speak" to the relative ESRs of the cells and their test setup. The problem is there is an uncertainty in the measurement cycle which can not be taken out. But it is good for looking at trends. Looking at the table below you can see a trend, which sort of rules out your first two thoughts.



As to voltage reading errors, why just this one? Wouldn't you expect it to be random? Wouldn't you expect aberrations in other cell measurements? They all share the same point on the PCB where the voltage is read from.

As to your last point, it does not exhibit that behavior at all. Below is a graph from all four batteries while being individually charged, a sneak preview of Part 3. Notice the tight grouping of the other three batteries which the relative ESR measurements concur with. Also note that Batt 2 terminated the CC phase early and had an extended CV phase. Trying to charge those four batteries in parallel would never work out I am convinced.



As to a bad cell, I would agree ever so slightly. It started out on the low side, but seems to have been exacerbated by the testing. It was preforming fine in the 120SR, although it didn't fly as long as the other three i.e. the flight time wasn't that short.
FredYates is offline Find More Posts by FredYates
Reply With Quote
Old Sep 14, 2014, 03:06 PM
Registered User
FredYates's Avatar
United States, OR, Lebanon
Joined Jul 2012
90 Posts
Quote:
Originally Posted by getsuyoubi View Post
Charging this one bad battery individually for a few cycles seems to revive it, at least for a while. I have to admit that this does not seem to make sense, since this bad battery should cause the charger to terminate early (in terms of charge) due to its supposedly higher internal resistance, and therefore I don't even know why I ever tried to improve the situation by charging it individually - but it worked!
Parallel charging with this one bad battery in the mix did seem to terminate the charge early as well, as evidenced by the total charge displayed on the charger. This also surprised me, because as resistances add as 1/R_i when connected in parallel one high resistance battery out of six doesn't really change the overall resistance of the whole pack.
You are arguing against your point. Taking the bad "seed" out of the mix makes it better, therefor maybe parallel charging it not quite as good as thought, but not necessarily bad as long as all the cells are "equal".

The question then becomes does it hasten the demise of a battery starting to go weak?

As to your statements on parallel resistance you are correct. But what you are not taking into account is ESR and IR are tools we use to model a battery, they don't really exist internally to the battery. So you can not do a parallel calculation on the imaginary ESR of a set of batteries and proclaim that is their collective ESR. All batteries are a black box, we stand outside attempting to peer "inside" and cogitate on how they work.
FredYates is offline Find More Posts by FredYates
Reply With Quote
Old Sep 14, 2014, 03:35 PM
Registered User
So. Cal.
Joined Oct 2004
8,034 Posts
Quote:
Originally Posted by FredYates View Post
I do not have an ESR meter so I can not quantify the ESR of the batteries with any great certainty. But I do make measurements at 1 second intervals and can "speak" to the relative ESRs of the cells and their test setup. The problem is there is an uncertainty in the measurement cycle which can not be taken out. But it is good for looking at trends. Looking at the table below you can see a trend, which sort of rules out your first two thoughts.

It actually confirms substantially higher resistance of cell #2.

Quote:
Originally Posted by FredYates View Post
As to voltage reading errors, why just this one? Wouldn't you expect it to be random? Wouldn't you expect aberrations in other cell measurements? They all share the same point on the PCB where the voltage is read from.
I apologize that I misread your last graph in post #1. I mistakenly believed that this graph was showing voltage rather than energy, thus my previous comments.

I suspect that voltage of all packs was nearly the same upon termination? If so, then cell #2 either has lower usable capacity or it had much higher starting voltage and this would explain the lower amount of energy required to charge this cell.

Quote:
Originally Posted by FredYates View Post
Also note that Batt 2 terminated the CC phase early and had an extended CV phase. Trying to charge those four batteries in parallel would never work out I am convinced.
Have you tried to charge them in parallel? I'm equally convinced that it would work just fine. The only potential very slight downside is that the poorest cells with higher internal resistance would have slightly lower resting voltage at charge termination. But then this is also true when charging singly so the net result is identical.

The lesson here is that one should observe the safe charge rate for the least capable pack when charging multiple packs in parallel and all will be just fine. There is a mountain of user data that demonstrates this truth.
mrforsyth is online now Find More Posts by mrforsyth
RCG Plus Member
Reply With Quote
Old Sep 14, 2014, 03:38 PM
Registered User
FredYates's Avatar
United States, OR, Lebanon
Joined Jul 2012
90 Posts
Quote:
Originally Posted by CerealKiller159 View Post
Also, if I am reading this right, the first chart is a capacity measurement, right?
It looks like Batt 2 just has a lower capacity than the others, unless I am missing something.
You are reading and understanding it correctly. Joules are a much more meaningful term than mAh when it comes to discussing battery characteristics because it best defines the total system.

The relationship to battery mAh is ... the label voltage X the label mAh X 3600. Which in this case is a misnomer, I think, since battery voltage is only constant for a finite instant in time. 1 Joule = 1Amp X 1Volt X 1S and that is what we are dealing with in supplying energy to the motor and electronics.

Motors are complex moving object comprised of inductance, resistance, capacitance and a little back EMF thrown in to complicate matters. Now toss in a dynamic load that is constantly changing being driven by voltage source that is constantly changing and you have a mess that mAh can not describe.

Again, in my opinion, it better describes the whole charge, discharge cycle than current plots or mAh X some static voltage, because that is not what is happening.

I think your other points were covered in previous posts. If not let me know and I will attempt to explain myself more fully.
FredYates is offline Find More Posts by FredYates
Reply With Quote
Old Sep 15, 2014, 04:49 PM
Registered User
FredYates's Avatar
United States, OR, Lebanon
Joined Jul 2012
90 Posts
Quote:
Originally Posted by mrforsyth View Post
It actually confirms substantially higher resistance of cell #2.
Yes it does, but only after it had been parallel charged two times. Note that after two years of being individually charged (the first line) it was 0.127ohms vs 0.252ohms (third line) after just two parallel charge cycles.


Quote:
Originally Posted by mrforsyth View Post
I suspect that voltage of all packs was nearly the same upon termination? If so, then cell #2 either has lower usable capacity or it had much higher starting voltage and this would explain the lower amount of energy required to charge this cell.
Going back to the first table in this post they were discharged to within 0.002V of each other. I am not sure how we conclude if the problem is less capacity or higher ESR, but yes it did as I point out in Part 1 and also in Part 2. I am not concerned that it has less capacity, I am concerned that that the ESR doubled after only two parallel charges and am grappling with why. Plus I do not think it took less energy to charge the cell, I think it acquired less energy and is therefore deficient in charge and again I am grappling with why.

Quote:
Originally Posted by mrforsyth View Post
Have you tried to charge them in parallel? I'm equally convinced that it would work just fine.
Mark, I think you have missed something in the dialog. These batteries had never been parallel charged and I grabbed them because they were all bought at the same time, were the same MFG and same capacity which made them good candidates for originating from the same lot at the factory. Additionally they were only used on my 120SR. Therefore the first discharge cycle showing Batt 2 slightly low was after those two years of individual charging. The third discharge cycle was after only two parallel charge cycles.

Quote:
Originally Posted by mrforsyth View Post
The only potential very slight downside is that the poorest cells with higher internal resistance would have slightly lower resting voltage at charge termination. But then this is also true when charging singly so the net result is identical.
Sorry but I can not agree with all this. All cells charged singly will have the same at rest voltage within a few millivolts, if you measure them with a high impedance DVM. I would think they have to, since the charger stops at the same terminal voltage for each battery and ESR at the final charge rate would only contribute 0.100ohms X 60mA = 0.006V error with my charger.

Quote:
Originally Posted by mrforsyth View Post
The lesson here is that one should observe the safe charge rate for the least capable pack when charging multiple packs in parallel and all will be just fine.
The max charge rate was 1100mA and only Batt 1 ever "saw" that rate; all others were always less.

Quote:
Originally Posted by mrforsyth View Post
There is a mountain of user data that demonstrates this truth.
Would you please point me to that "mountain of user data" and I will happily stop wasting my time and everyone else's with my carefully instrumented observations.
FredYates is offline Find More Posts by FredYates
Reply With Quote
Old Sep 15, 2014, 05:56 PM
Registered User
So. Cal.
Joined Oct 2004
8,034 Posts
Quote:
Originally Posted by FredYates View Post
Yes it does, but only after it had been parallel charged two times. Note that after two years of being individually charged (the first line) it was 0.127ohms vs 0.252ohms (third line) after just two parallel charge cycles.
Is this suggesting that the two parallel charges were causal rather than coincidental to the observed increase in internal resistance?

Quote:
Originally Posted by FredYates View Post
Going back to the first table in this post they were discharged to within 0.002V of each other. I am not sure how we conclude if the problem is less capacity or higher ESR, but yes it did as I point out in Part 1 and also in Part 2.
Are the voltage values in this chart loaded or no-load values? I was under the suspicion that these were cutoff values when under load. If so, this would explain the lower delivered energy and lower accumulated energy during charge for cell #2, given its higher cumulative resistance. If this is unloaded voltage, there is then a clear capacity delta.


Quote:
Originally Posted by FredYates View Post
Sorry but I can not agree with all this. All cells charged singly will have the same at rest voltage within a few millivolts, if you measure them with a high impedance DVM. I would think they have to, since the charger stops at the same terminal voltage for each battery and ESR at the final charge rate would only contribute 0.100ohms X 60mA = 0.006V error with my charger.
I agree, and the same holds true when charging in parallel. I have charged packs with wildly disparate FOM (capacity normalized internal resistance) and all cells have always terminated within a few mV of one another. I also frequently monitor internal resistance and have never seen any degradation due to charging packs of dissimilar IR in parallel with one another. Note also that most of my packs have always been parallel charged, save for initial characterization cycles and periodic spot checks to monitor usable capacity.

Quote:
Originally Posted by FredYates View Post
Would you please point me to that "mountain of user data" and I will happily stop wasting my time and everyone else's with my carefully instrumented observations.
Julian's thread is a great repository of information and real world user data regarding parallel charging of Lithium and Pb-based secondary batteries: http://www.rcgroups.com/forums/showthread.php?t=932319

I sincerely hope that my queries are not misinterpreted as being contrarian as I do greatly appreciate all of the work that you've expended in collecting and presenting your data. My chief aim is to understand how you're interpreting the data and offer my experience as it relates to parallel charging and operation of lithium chemistry batteries.

Regards,
Mark
mrforsyth is online now Find More Posts by mrforsyth
RCG Plus Member
Reply With Quote
Old Sep 15, 2014, 08:19 PM
Registered User
FredYates's Avatar
United States, OR, Lebanon
Joined Jul 2012
90 Posts
Quote:
Originally Posted by mrforsyth View Post
Is this suggesting that the two parallel charges were causal rather than coincidental to the observed increase in internal resistance?
It is not making either suggestion, it is simply making an observation and asking questions is so doing. Why after two years of use did this battery out of the four do this? Is it causal or coincidental ? Is there something inherent in the method or setup that could cause this?

Quote:
Originally Posted by mrforsyth View Post
Are the voltage values in this chart loaded or no-load values? I was under the suspicion that these were cutoff values when under load. If so, this would explain the lower delivered energy and lower accumulated energy during charge for cell #2, given its higher cumulative resistance. If this is unloaded voltage, there is then a clear capacity delta.
They are loaded voltages and as such include all artifacts possible, battery ESR, connector resistance, trace resistance, battery wire resistance, etc. Without a great deal of trouble I do not know of a way to discharge to an unloaded voltage. I agree the higher ESR of the cell it explains why Batt 2 delivers less energy, but not why it accepts less energy for as I have shown the ESR only contributes ~0.006V in terms of error. Could that 0.006V be significant? I do not think so.

Quote:
Originally Posted by mrforsyth View Post
I agree, and the same holds true when charging in parallel. I have charged packs with wildly disparate FOM (capacity normalized internal resistance) and all cells have always terminated within a few mV of one another. I also frequently monitor internal resistance and have never seen any degradation due to charging packs of dissimilar IR in parallel with one another. Note also that most of my packs have always been parallel charged, save for initial characterization cycles and periodic spot checks to monitor usable capacity.
Perhaps I should add in yet another parameter in my table, unloaded voltage at start of charge. But I am not sure what value that number has. Yes there is a relationship between capacity and voltage, but I am not sure if it is a well defined relationship or just a great rule of thumb.

Quote:
Originally Posted by mrforsyth View Post
Julian's thread is a great repository of information and real world user data regarding parallel charging of Lithium and Pb-based secondary batteries: http://www.rcgroups.com/forums/showthread.php?t=932319
I looked at part of his thread (first dozen or so pages) and only found "how to do it", "how others did it" "lots of pictures of setups" and "people asking how they should do it under different circumstances". I did not see any hard, real world, data, but as I said I did not explore the entire thread. Can you recommend a specific page I should start with to view data and skip the fluff?

Quote:
Originally Posted by mrforsyth View Post
I sincerely hope that my queries are not misinterpreted as being contrarian as I do greatly appreciate all of the work that you've expended in collecting and presenting your data. My chief aim is to understand how you're interpreting the data and offer my experience as it relates to parallel charging and operation of lithium chemistry batteries. Regards, Mark
Therein lies the rub, I am not interpreting the data at all as of yet. I am trying to understand why, what is happening and what are the drivers in the scenario.

For example, why does Batt 2 the one with the highest ESR and the least ability to accept charge seem to be dominating the CV phase of the parallel charge cycle and maybe terminating the charge cycle? Is it because of the high ESR and the cell voltages all being almost equal it causes the charger to terminate? If it is, doesn't that imply that the other three batteries are not being fully charged or mal-charged? If so is that causing two of the other batteries ESRs to inch up ever so slowly? But then why is the third one going down ever so slowly? Since I know my ESR measurement is slightly flawed should I even be using it as a trending indicator? But then since I am only treating it as a trend and not an absolute isn't it valid to be using it as a sanity check? Unfortunately this is not a simple case of trying to use a 4-40 nut on a 6-32 screw. A smack on the head will not help.

Cheers, Fred
FredYates is offline Find More Posts by FredYates
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Parallel Charging Facts - Part 1 Batts Inserted in Harness, then Charge Applied FredYates Batteries and Chargers 23 Sep 13, 2014 07:31 PM
Sold T-plug parallel charging board 420flyboy Aircraft - Electric - Batteries & Chargers (FS/W) 2 Aug 11, 2014 09:10 PM
Discussion Batts in series & parallel Chuck Steak Batteries and Chargers 10 Mar 28, 2014 03:38 AM
Discussion charge rate for 3s 1000mah lipo batteries in parallel htuong95 Batteries and Chargers 5 Feb 27, 2014 10:16 PM
Sold SOLD - 2 1/2 Blade mCXs, RTF,4 batt.,blades, 2 charges, glo blades, xtra parts Old Blade Man Aircraft - Electric - Helis (FS/W) 3 Jan 13, 2012 07:30 AM