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  1. #1
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    parallel or series charging

    Ok been researching parallel and series charging. Which is actually better for charging lipo??
    If I understand this right series. you just add voltage together and charge it 2-2s would = 4s.
    The charge rate would stay the same.
    Parallel you just add the capacities together so you could charge 2-5000 mah packs like it was one 10000mah or at 10 amps.
    The wattage need for both ways is the same.
    16.8v x 5amps = 84 watts 8.4v x10amps = 84 watts.
    If I understand this correct you can take (batteries mah/micro charge amps) x 60 = approximate charge time in minutes Micro charge amps is say 5amps x 1000 = 5000 mca

    Assuming a 50watt 5 amp charger and 1c charge rate

    So a parallel 2-2s 5000 8.4v x 10amps = 84 watts needed only 50 watts available can only charge at 50watts/8.4v = 5.95amps so 5amps 10000mah / 5000mca x 60 = 120 min.

    so a series 2-2s 5000 mah 16.8v x 5 amps = 84 watts needed only 50 available so can only charge at 2.98 amps 50watts / 16.8v = 2.98 5000mha / 2900mca x 60 = 103 min.

    90 watt charger 20 amps and 1c charge rate hyperion 720i

    parallel 2-2s 5000 mah 8.4v x 10amps = 84 watts needed 10000mah / 10000mca x 60 = 60 minutes
    series 2-2s 5000 mah 16.8v x 5amps = 84watts needed 5000mah / 5000mca x 60 = 60minutes

    1 2s by itself 5000 mah / 5000 mca x 60 = 60 minutes
    so on a 50 watt charger you could save about 17 minutes in charge time.

    also if you take the numbers run them in the traxxas charger which is 80 watts but only 6amps you 100 minutes for parallel an 63 minutes for series.

    I guess I am asking if I understand this correctly?? What are the pros and cons of both ways??
    Is it really beneficial to charge in series if your charger is under powered??
    How does the balance work when doing parallel?? I understand how it does it in series.
    Last edited by mes882; 07-29-2012 at 04:14 PM.

  2. #2
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    You may want to pm an admin and have this thread moved to the traxxas alley. You will get a lot more responses from there. That way all the Erevo and Emax guys can help you since they run dual lipos! I am also interested in this topic.
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  3. #3
    RC Turnbuckle Jr. BaldyDaniels's Avatar
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    Wow thats a lot of info to absorb all at once! lol.

    First off, any questions you have regardiong a specific brand of charger or battery other than Traxxas will need to be directed to that specific manufacturer as we cannot answer those questions here.

    I can tell you that you have your chemistries mixed up a little. An 8.4v pack would be an nimh pack, not a 2s lipo which is 7.4v.

    Charging parallel is ok for nimh packs, but will take twice as long at the same amperage used for charging one pack.

    Balancing lipos in parallel doesnt work well and is not a risk i would be willing to take or to recommend.

    I do however balance charge lipos in series on a regular basis, and i can tell you that no matter what the expected charging times may be when you calculate it, it takes a lot longer. The charge time will be dependant on the condition of the cells, the quality of the cells and of course the quality of charger being used. My charger is dual 20 amp output, so i can charge quite a few lipos at one time, regardless of their mah capacity or cell count as long as i dont exceed the cell count per port. I build my own adapters for charging in series while connected to a balance board, but i cannot in good conscience post instructions here on how to do so because of the dangers involved if done incorrectly.

    The best way to charge multiple lipos at once is to get a charger that is capable of doing so, along with an appropriate balance board. Or buy more than one charger.

    The other way to go is to buy multiple packs, charge em all up then keep cycling them onto the charger as you use them. this way youll always have a charged pack or two when you need it.

    When deciding on a charger, dont cheap out. A Cheap charger will cost you more in the end if it destroys your lipos. There are plenty of good online resources for building your own series adapters, just google it. There are also many online retailers that sell adapters for series charging multiple lipos.

    Just be safe when charging, and if youre not sure it will work, DONT TRY IT!
    Last edited by BaldyDaniels; 07-29-2012 at 05:26 PM.
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  4. #4
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    I'll take issue with the 7.4V vs. 8.4V distinction. A LiPo cell is 3.7V nominal but 4.2V maximum. Now while some prefer to use one or the other as an identifier, either is correct. Especially when discussing chargers and charge rates, the 4.2V figure is more relevant. IMO.
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  5. #5
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    Your right baldly to much info at once. Mind overload!! lol

    I know you are right a 2s lipo is considered 7.4v. But I would think you would want to use 4.2v/cell. When doing the math. Thats why I used 8.4v. Is that not right??

    This peaked my interest when I seen the traxxas dual charging adapter 2917 for 2s and 2918 for 3s at my local hobby shop yesterday. Thought it would work well with the charger I just ordered. Hyperion 720i ac/dc 20 amps 90watts on ac 150 on dc. No question on the charger.

    Just wondering what would be better parallel or the traxxas adapter in series. If the math above is right. It would give me an idea if it would be worth buying a second one for the 50 watt 5 amp charger I have. I would think series would be the way to go. You need more volts, more watts but less amps. Also Isn't charging at lower amps better on the battery?? Plus you can see what each cell is doing on the charger when balancing

    I know there are real world factors in this that will affect actual times. But is that the proper way to figure how long it would take??

  6. #6
    Marshal ksb51rl's Avatar
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    Quote Originally Posted by mes882 View Post
    Your right baldly to much info at once. Mind overload!! lol

    I know you are right a 2s lipo is considered 7.4v. But I would think you would want to use 4.2v/cell. When doing the math. Thats why I used 8.4v. Is that not right??

    This peaked my interest when I seen the traxxas dual charging adapter 2917 for 2s and 2918 for 3s at my local hobby shop yesterday. Thought it would work well with the charger I just ordered. Hyperion 720i ac/dc 20 amps 90watts on ac 150 on dc. No question on the charger.

    Just wondering what would be better parallel or the traxxas adapter in series. If the math above is right. It would give me an idea if it would be worth buying a second one for the 50 watt 5 amp charger I have. I would think series would be the way to go. You need more volts, more watts but less amps. Also Isn't charging at lower amps better on the battery?? Plus you can see what each cell is doing on the charger when balancing

    I know there are real world factors in this that will affect actual times. But is that the proper way to figure how long it would take??
    Your figuring is correct. Traxxas only recommends their adapter for their charger since it may not be able to handle the extra amperage some chargers push. Take my charger: instead of the 6A of the Traxxas EP+, mine will do 40A. Unless the adapter is specifically rated for how I'll be using it, I'm not using it.

    Regarding charge times, if a charger has an option to change the termination charge (C/5, C/10, C/20) times can be significantly reduced - at the cost of a few mAH.
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  7. #7
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    Yeah I did see they recommend it for the traxxas charger only. I would like to believe it is made to handle 15 amps or so. Any idea what size of wire is used on the adapter?? To me it looks like the main power leads are 14 gauge and the balance leads are 16 gauge. 14 gauge should be good for 20 amps. Dont these chargers charge through the main power leads?? Then discharge though the balance leads to balance. The questionable thing would be the board traxxas used to connect the wires in series.

    Could you please explain the c/5, c10, c20. I don't know what that is. Thanks

  8. #8
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    To clear up what I feel is false information that has been posted above...

    Charging NiMh in parallel or series is not recommended. It will give false peaks. I always suggest charging NiMh one pack at a time.

    Balancing LiPo cells in parallel DOES work. As soon as you hook the any two batteries in parallel the cell voltage is equalized. This is why it is suggested to always hook the main leads up first AND to have both packs be similar in voltage. You will be instantly charging the low pack and discharging the high pack.
    The information that parallel charging does not balance cells is false.

    I disagree that the best way to charge multiple LiPo's is to get a multi-charger... that is unless you want to charge different chemistries at once. Most multi-chargers are underpowered.... at least by my standards. lol

    The reason you read/hear more about series charging is simply because it is more complicated than parallel charging. If you think about it, why would you post up comments or questions about something that is easy to understand and you are not having any issues with?? This is why parallel charging is not discussed as much as series charging.


    All that being said, I parallel charge...
    I can bring two 7600mAh LiPo's from storage to full in about 20 minutes, charging at 1.3C.
    I can bring six 2200mAh LiPo's from storage to full in about 20 minutes, charging at 1.5C.
    If I want to run both my 16th Revo and 10th Summit...
    I can bring two 7600's and four 2200's from storage to full in about 30 minutes at .83C.

    I have an iCharger 206B... 20 amps of charging power.

    I definitely agree that cheaping out on a charge system is a mistake... your charge system is the backbone of your electric RC hobby -treat it as such! RC's will come and go... your charge system will remain!
    Whatever it is I just said... I could be wrong.

  9. #9
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    So where at 2 for series and 1 for parallel. I am just interested in doing this with lipo's

    I could see the packs balancing each other out when connected in parallel.

    With the math I can also see that if your charger Does not have high amp rating but has wattage series would be the way to go. More volts less amps. You could charge it faster using higher voltage. The traxxas charger 6 amps but 80 watts. So series would be the way to go.
    If your charger had high amp rating and low voltage then parallel would be the way to go.
    If your charger has high amps and a higher wattage. The hyperion I bought is 20amps and 90watts ac or 150 watts on dc or like jimmie icharger 206b
    It is kinda a wash because you have enough amps and watts available. Or say personal preference.
    Would this seem like a fair assessment

  10. #10
    RC Turnbuckle Jr. DiggerPede's Avatar
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    I charge my Lipo's Parallel only, using an FMA Powerlab-6 charger and 600W PSU. I'm not going to explain the high technes like above. But I read up and Parallel is the easiest route to figure and charge multiple Lipo packs. I use an FMA MPA balance board and can charge 6 - 2S packs in around 30 minutes that includes balancing them out everytime. This setup doesn't sweat at all. I have to agree with Jimme up there he explains is very well. I can say one thing KSB helped me get my setup going.

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  11. #11
    RC Turnbuckle Jr. Petertje60's Avatar
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    When you have two Lipos who are not discharged equally, the first thing that happens when you connect them in parallel, is that the less empty one will be charging the most empty one. That doesnt happen when you charge two batteries in series.

    For my 1/16 cars I always charge pair by pair in series. I just use a serial harnass and a 4S/2S or 6S/3S splitter.
    Works like a charm and I will always notice when there is one cell not in a good condition anymore.

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  12. #12
    RC Turnbuckle Jr. DiggerPede's Avatar
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    Yo Peter that is some good info. Cudos to Baldy to. I think this is a good topic to bring up for sure. I'm always willing to learn something new. I think there are pro's and con's to both. When I parallel charge my packs they have balanced out really well. All are 4.200 or 4.195. Like stated above the quality of charger totally makes a difference.
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  13. #13
    RC Turnbuckle Jr. BaldyDaniels's Avatar
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    Quote Originally Posted by Jimmie Neutron View Post
    Balancing LiPo cells in parallel DOES work. As soon as you hook the any two batteries in parallel the cell voltage is equalized. This is why it is suggested to always hook the main leads up first AND to have both packs be similar in voltage. You will be instantly charging the low pack and discharging the high pack.
    The information that parallel charging does not balance cells is false.
    This is some good info, I don't mind getting an education, as I am no pro when it comes to this stuff. Thanks for the corrections. The info I had researched previously about balancing lipos in parallel was for mixed cell counts. When you say that hooking up any two batteries in parallel the cells equalise, you mean any two packs of the same cell count, right? I charge packs of different cell counts, that's why I charge in series. I use more than enough power to charge lipos, and since my charger does up to 8 cells per port, i like to be able to charge as many packs as possible per port, 2s and 3s.

    As Peter stated above,What about parallel charging lipo packs of the same Cell count, but with a large difference in discharge levels? If i understand correctly, this would never be an issue if running an rc that used dual lipo packs that discharge to nearly the same level, but all 12 Of my 3s packs would be at different discharge levels from running them on my P2de for different amounts Of run time. Wouldnt the packs always having to equalise make this an inefficient way to charge the packs, therefore taking longer?

    Quote Originally Posted by Jimmie Neutron View Post
    I disagree that the best way to charge multiple LiPo's is to get a multi-charger... that is unless you want to charge different chemistries at once. Most multi-chargers are underpowered.... at least by my standards. lol

    I have an iCharger 206B... 20 amps of charging power.
    The best way "could be" using a multi charger, but that only depends on how much a person is willing to spend on a charger setup. I agree, most cheaper multi chargers are very underpowered. Heck, some of them would be weak as a single output charger. 😜

    I use a Thunder Power RC TP820CD, Dual port @ 20 amps per port. Powered by a protek r/c super pro 1000w five output 40amp power supply. No shortage of power and very quick charging in series, i guess this is why i had not become fluent in parallel charging.



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  14. #14
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    Thank you for taking my corrections without offense... some people are not as mature as you are.

    Parallel charging is ONLY for packs of the same cell count. I did forget to mention that...
    Series charged does allow for different cell counts, but I believe they all have to be the same capacity?? It has been so long since I have even looked at my series charging notes. lol

    Parallel charging two packs of different charge levels will cause a really fast charge on the low pack and a really fast discharge on the high pack... possibly damaging both packs in the process; remember as soon as you hook any packs in parallel the packs will equalize nearly instantly... and probably exceed the discharge and charge C rate of the packs.
    For this reason I usually always run to LVC... a common voltage AND double check each cells' voltage before hooking them to my ParaBoard.

    There is no perfect (fast) way to charge multiple packs*... some will choose series, some will choose parallel.
    For which ever is chosen, be sure to fully understand what is exactly happening to your packs and your cells... misunderstanding your charge method is where accidents happen. LiPo's go bad for a reason... not "just because".

    *unless you have the money for multiple high-amp chargers and power supplies. lol


    That sounds like a killer charge set-up!
    I am running only one 20amp 300watt port fed by a 75amp 24volt 1800watt supply.
    Eventually, I might... might get a 40amp system. Just for kicks. lol
    Whatever it is I just said... I could be wrong.

  15. #15
    RC Turnbuckle Jr. BaldyDaniels's Avatar
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    Quote Originally Posted by Jimmie Neutron View Post
    Thank you for taking my corrections without offense... some people are not as mature as you are.

    Parallel charging is ONLY for packs of the same cell count. I did forget to mention that...
    Series charged does allow for different cell counts, but I believe they all have to be the same capacity?? It has been so long since I have even looked at my series charging notes. lol
    You are correct, charging lipos in series requires all the packs to be of the same mah capacity. They can have varied discharge levels, but with a low power charger, the further apart they are in voltage, the longer it will take to balance out all of the cells. With my current charging setup, the extra charge time to balance packs with different discharged states is only a few mins.

    Quote Originally Posted by Jimmie Neutron View Post
    Parallel charging two packs of different charge levels will cause a really fast charge on the low pack and a really fast discharge on the high pack... possibly damaging both packs in the process; remember as soon as you hook any packs in parallel the packs will equalize nearly instantly... and probably exceed the discharge and charge C rate of the packs.
    For this reason I usually always run to LVC... a common voltage AND double check each cells' voltage before hooking them to my ParaBoard.
    ^^^^^ THIS IS NEED TO KNOW INFO!^^^^^^ Without knowing this, you could cook lipos and not even know what went wrong.

    Jimmie, do you think the short bursts from close (but not exactly the same) pack voltages that exceed the discharge or c rating, shorten the overall Life of the packs as compared to packs that are always charged one at a time?

    Quote Originally Posted by Jimmie Neutron View Post
    *unless you have the money for multiple high-amp chargers and power supplies. lol

    That sounds like a killer charge set-up!
    I am running only one 20amp 300watt port fed by a 75amp 24volt 1800watt supply.
    Eventually, I might... might get a 40amp system. Just for kicks. lol

    Yeah the 40amp dual port charger is nice for sure, but the quick charging capability was not the main reason for buying it. My favorite part about the TP820cd is that the ports are independant, so i can charge a different chemistry on each port at the same time.

    The power supply you are using sounds like quite the powerhouse. Does it dim the neighbors lights when you power it on? Lol. Youve got more than enough supply there to run a 40amp dual port, so thats 65% of the cost already taken care of. I was quite thrown back when i had purchased my charger first for around 300, only to find out that the supply with the options i wanted was 400! Then i see 100amp dell server supplies selling for 5 or 10 bucks in ebay a week afterwards. 😱 I have no regrets though, its a solid setup, hopefully its the last one i will need.



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  16. #16
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    The short burst may shorten the life span of the pack... but I make sure that the voltage is no more than 0.01 volt off.
    I have yet to see an issue with this phenomena and I have hundreds of cycles through my tiny 2200mAh packs... the packs that this would effect most.

    The PS does dim lights... actually. lol But only when it is first turned on. I have yet to cycle this PS anywhere near its full capacity. Shoot... when it is 100F+ outside, the PS is a cool 80-90F inside an enclosed box with no ventilation running my charger.
    I ran into them on eBay... $15 shipped for both. It was a hard sell to my wife that I needed them as I just got done buying and starting a different PS build the week before. lol But, the other PS's I have are much larger physically yet have only 30 available amps. I knew that I would eventually be getting a bigger charger... so I went for the 75 amp monsters.

    I wouldn't mind having a dual port charger... but for me to consider it I would like it to have 40 amps per port.


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  17. #17
    RC Turnbuckle Jr. DiggerPede's Avatar
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    Good stuff here Jimmie & Baldy. Since I run packs of different capacities, Parallel is more useful & convenient for me. Seems to be doing a very good job so far. I do keep all the packs within the same voltage of each other. This is some information that I found for parallel charging.

    Requirements and recommendations for parallel charging

    •A parallel wiring adapter for the main leads. This can be for as few as 2 packs or as many as 6 or more, your choice.

    •A parallel wiring adapter for the balance leads is optional but highly recommended. Ideally it should have the same number of connections as the main leads adapter.

    •All the packs you charge in parallel must be the same type and cell count. There is no need to match the capacity, C-rating, age or brand for parallel charging. For example you can charge a 3s 2200mAh 15C lipo, a 3s 3200mAh 25C lipo and a 3s 850mAh 35C lipo together, but you can not charge any 3s lipo in parallel with a 4s lipo.

    •Ideally the packs to be charged should all be at a similar voltage. If I had to put a number on it I would say that all cells should be within .2V for each other. This is not required but is a good practice.

    Potential benefits

    •Huge time savings. Not only do you get multiple packs done at once but you also only have to hook everything up once.

    •More efficient way to charge multiple packs than serial charging. Keeping the voltage lower means less work for the charger.
    •Allows for simultaneous charging of 12s flight packs made up of pairs of 6s packs on chargers that can not otherwise charge 12s packs. Same with 10s or 8s made up of paired 5s or 4s packs.
    •Safer than serial charging. Because you can connect the packs in any order, there is no chance of creating direct shorts if you mix up the connections. This is assuming you have proper adapters.

    Potential drawbacks and warnings

    •If something were to go wrong during the charge cycle it could effect multiple packs. For example if the charger was setup incorrectly, it would effect all connected packs instead of just one.
    •When parallel charging you loose the ability to monitor each pack independently. Only averages are displayed by the charger.

    •If packs are at vastly different voltages when you connect them together in parallel, it is possible that a large amount of current can flow between the packs as they equalize themselves. In most cases this will not damage the batteries but it can damage the wiring.

    •Parallel charging large packs on lesser capable chargers will give little to no benefit, aside from only having to set up charger one time, due to small output capability. Parallel charging is really done best on larger chargers.

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  18. #18
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    Peter with that set-up how do you know that battery 1 is on balance port 1 and 2. battery 2 is on balance port 3 and 4 The traxxas one is lable batt. 1 and batt. 2 Then balance port is 1 and 2. Or does that not really matter.

    Has anyone tried charging in a combination circuit??? I do electrical work for a living. And when I hook up battery back up systems. They will use several batteries in series to get the voltage they want. Then parallel some to get the amp hour they want. They get charged and discharge that way. Was wondering if any one has tried it with lipos?? You could potentially charge 4-5000mahs pack at 1c using 10 amps. Only needing a charger rated for 168 watts. I dont want to telling anyone how to do it due to the possible risks.
    Last edited by mes882; 08-01-2012 at 06:01 PM.

  19. #19
    RC Turnbuckle Jr. BaldyDaniels's Avatar
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    Quote Originally Posted by mes882 View Post
    Has anyone tried charging in a combination circuit??? I do electrical work for a living. And when I hook up battery back up systems. They will use several batteries in series to get the voltage they want. Then parallel some to get the amp hour they want. They get charged and discharge that way. Was wondering if any one has tried it with lipos?? You could potentially charge 4-5000mahs pack at 1c using 10 amps. Only needing a charger rated for 168 watts. I dont want to telling anyone how to do it due to the possible risks.
    I imagine that the back up system is made using lead acid batteries which are kept topped up by a regulated taper charger. These taper chargers don't let the voltage climb higher than the trickle charge voltage, so they can also be used to maintain a battery. They won't damage the battery if left on charge too long (even when left on the battery permanently), and they don't change their charging characteristics if the line voltage should change. This is how these systems are able to get away with charging combination circuits Without damaging the batteries.

    If you used a combination circuit for multiple lipo packs, wouldnt you lose the ability to balance the individual cells?




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    Yeah They are lead acid but the principal should be the same. The people here say there packs balance just fine when they parallel charge them. Then when in series you have all your balance ports plugged in.

    Really all you would be doing is connect 2 sets of 2 batteries in parallel. Which would act like a bigger battery. Then series Those 2 sets and you would have a greater voltage.

    So say you have 4 - 2s 5000 mahs packs. 2 in parallel would act like one 2s 10000 mah pack. Then You have 2 more in parallel so another 7.4v 10000mah pack. Then you connect them is series so now it should act like a 4s pack at 10000mah
    So you should be able to charge them at 16.8v at 10 amps = 168 watts

    I think it would work just fine as long as all the packs are the same. But I personally like seeing what each cell is doing on the charger. Also with lipos getting charge rates of 2c or higher. There is no need to do it. I was just wondering if any one has tried it.

  21. #21
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    i know this is late in the thread but I always thought charging in series would be better, But why would the manufacturers make parallel configs if it was bad.
    Take the high end traxxas 12800mah that is a 2s4p config. I know it needs to be a 4p because of the capacity, but if it was risky, would they not of limited to a 2s1p config and stayed at that even though it would be a low capacity. Because basically the pack is a 4 x 3200mah 2s's in parallel. So while this would be ok to charge as a unit i can't see any reason why using multiple sperate packs any different.
    Theres been a lot of good info ^there and only looked through it quickly.So i made of made a useless comment.
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  22. #22
    RC Turnbuckle Jr. Petertje60's Avatar
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    Parallel charging isnt bad, when the cells you are charging were discharged to the same level (which always happens with my sets for the 1/16 scale cars). That is something which always happens when they are combined in a Lipo pack.

    As stated earlier, unevenly discharged packs will even out when they are connected parallel. When charged in series that wont happen and the situation will be interpreted as unbalanced cells and the balancer will take care of getting them to the same level in a safe way.

    I notice I missed a question in this thread. When you look at the balancer cables, the cell that is connected to the positive side of the balancer cable, has the highest number. So on the picture in post #11, the left 3S balancer lead will have cells 6,5 and 4 (from left to right) and the right side cells 3, 2 and 1.
    Not sure if that is different on different chargers, but to be clear, I am using a Fusion Emperor L702B Pro.
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