RCME - Parallel Universe in January 2017

[john stones 1 - Moderator]

And folk keep saying electric is much simpler,less hassle n less to carry and easier for a newbie

[Mike T]

Posted by MattyB on 27/12/2016 18:30:45:

So can I ask one question - when you are charging your 2x 3S 2200s and they were taking over 2-2.5 hrs to reach a full charge state, what max current were you selecting on the charger?

Edited By MattyB on 27/12/2016 18:32:39

4.4A - parallel

2.2A (6S) - series

[MattyB]

Ok - if you have set to 1C and you are effectively getting around 1/3C there is something wrong with your charger or paraboard, pure and simple. I have seen a faulty paraboard that have similar results so borrowing a friends to see if that fixes it is probably the best troubleshooting step; if that doesn't fix it it must be a charger or battery issue.

[Mike T]

Hi Bryan. Like all reformed Scrooges, I enjoyed Christmas very well, thank you!

It's not easy to cut/paste/quote on this forum without losing anything previously typed, so my responses have to be composed from memory! In the first posts in this thread, you yourself state that serial charging is a bad idea and the immediate respondent at refers to "rubbishing" it and moving on or words to that effect.

Your warnings were appropriate, but could equally well apply to a //el charging 'lash-up'. The need for such lash-ups is reduced by the wide availability of paraboards and this is now the case with series charging leads. Exercising the same level of care when using either type will mitigate any risks to the same degree.

I don't think I'm being blase, as my more recent posts here will attest.

As for qualification, well that's a lose/lose on any forum, isn't it? If you qualify your comments, e.g. to admit that different circumstances may produce different effects/results, then you may be accused of undermining your own argument. If you don't qualify your comments, may be accused of being dogmatic, e.g. asserting that serial charging is a bad idea...

[Mike T]

Posted by MattyB on 28/12/2016 15:46:18:

Ok - if you have set to 1C and you are effectively getting around 1/3C there is something wrong with your charger or paraboard, pure and simple. I have seen a faulty paraboard that have similar results so borrowing a friends to see if that fixes it is probably the best troubleshooting step; if that doesn't fix it it must be a charger or battery issue.

Possibly, Matty, but they do seem to charge OK when only a single pack is charged (i.e. that suggests the paraboard).

The Overlander is a fussy charger. On a balance charge it'll faff around for 15mins with all cells on 4.2v before ending. On a 'fast' (but still balancing) charge, it will end in about 70 mins.

I won't be buying a charger like yours any time soon, but taking others views in to account, perhaps a modest upgrade is due.

[MattyB]

Posted by Mike T on 28/12/2016 16:11:02:

The Overlander is a fussy charger. On a balance charge it'll faff around for 15mins with all cells on 4.2v before ending. On a 'fast' (but still balancing) charge, it will end in about 70 mins.

I won't be buying a charger like yours any time soon, but taking others views in to account, perhaps a modest upgrade is due.

Yup, 70 mins is the std "1C" charge time I am inclined to agree a change of charger is required, unless you can flash your current one with new firmware that will speed up the balancing process. There is no way if you at discharging to 3.7V/cell that a 1C charge should take more than an hour; mine take around 50-45 mins on either of my iChargers, though I generally charge at 2C these days.

I do really like both my iChargers (my first a 106b is still going strong after 5 years, though I don't use it much since I got the 406), but with the fall in the pound they are now a lot more expensive. A year ago my 406 was a not insignificant £215 odd inc p&p, yet now they are over £270! The A good affordable alternative are the Turnigy (Hobbyking) Reaktor range - they are based on the iChargers and run the same firmware. Very popular so not often in stock, but if you can find one they are a bit of a bargain and far better than the competition at their price point with accurate speedy balancing and the ability to measure cell IR.

Turnigy Reaktors

Edited By MattyB on 29/12/2016 02:22:47

[Mike T]

The Overlander is my latest charger and I still have/use the others that preceded it. I'm inclined to think that multiple chargers is the way to go ( I could buy at least 5 for the money you laid out!), as long as I don't go over the 47A rating of my power supply (and I have more than one of those!)

[Robert Hynes]

Just wanted to say thanks to Mike Freeman for this article on parallel charging. As a result of reading it I went straight out and bought two paraboards and will be buying more.

I particularly enjoyed the detail in the article and the technical account of the risks.

I currently have three electric aircraft with four LiPos each. The fact that I can now charge all twelve packs in less than an hour will change my life.

I do agree that safety is paramount and will be writing a reference article in Aerobase in the near future crediting your article as the source Mike. When that is finished I will post a link to a new thread on the ModelFlyingForum here for input.

Again thanks, I really enjoyed the article.

Bob Hynes.

[MattyB]

Posted by Mike T on 01/01/2017 15:23:25:

The Overlander is my latest charger and I still have/use the others that preceded it. I'm inclined to think that multiple chargers is the way to go ( I could buy at least 5 for the money you laid out!), as long as I don't go over the 47A rating of my power supply (and I have more than one of those!)

Yes, multiple chargers is an option that can work well, but (as you've found) the balancing programmes and max balancing current on the cheaper ones can at limit charge rates. There are plenty of places in RC where you can cut costs now with no real negatives, but for me charging is not one of those - given the capacity for fire if an overcharge occurs I'd rather have a known high quality product than lots of cheaper chargers that are often cloned and of uncertain lineage. YMMV.

[Robert Hynes]

I believe you have a very valid point Matty and it is one that I will cover in detail in AeroBase in February.

To preempt that slightly, 1. Safety is paramount and 2. Parallel charging is definitely not for everybody.

[Mike Freeman]

Posted by Robert Hynes on 16/01/2017 12:43:46:

Just wanted to say thanks to Mike Freeman for this article on parallel charging. As a result of reading it I went straight out and bought two paraboards and will be buying more.

I particularly enjoyed the detail in the article and the technical account of the risks.

I currently have three electric aircraft with four LiPos each. The fact that I can now charge all twelve packs in less than an hour will change my life.

I do agree that safety is paramount and will be writing a reference article in Aerobase in the near future crediting your article as the source Mike. When that is finished I will post a link to a new thread on the ModelFlyingForum here for input.

Again thanks, I really enjoyed the article.

Bob Hynes.

Thanks Bob,

I'm glad you found the article useful and thanks for your kind comments. It's great to hear you've had a go at parallel charging and are enjoying the time saving it offers. I'll swear my packs are also better balanced since I've been parallel charging!

My exploits are very much at the club flyer level but, from some of the posts on here, it looks like there is some serious parallel charging going on out there! Some very interesting reading. The principles are the same, its just the size of the equipment that changes!

Cheers,

Mike

[Devcon1]

Here's my setup, although the batteries are on the worktop I never leave them unattended during use as there's always something else to be done in shedland 😂

[Robert Hynes]

Hi Mike,

I thought you would like to know that the AeroBase article on parallel charging LiPos is complete and you can read it in PRE RELEASE state at this link http://rcaerobase.ipjdev.co.uk/index.php/in-flight/106-method-and-risks-of-parallel-charging-lipo-battery-packs

It's important to add that none of your text or photographs or tables are copied as that would infringe copyright. The Aerobase article, although inspired by your RCM&E article, stands on it's own and has several distinct differences and any comments you might have on it would be greatly appreciated.

By the way it might be worth adding that AeroBase registered users get updates via email when new articles are pre released. This allows registered users to get their comments in early, all leading to improved records before full release.

Finally I would like to say a special thank you for this idea. I now parallel charge my LiPos exclusively and am considering buying a large dc power supply to power all my chargers at once. My goal is to be able to parallel charge all my LiPos in under one hour. Brilliant.

With kind regards,

Bob.

[Bryan Anderson 1]

Posted by Robert Hynes on 13/04/2017 11:41:44:

Hi Mike,

I thought you would like to know that the AeroBase article on parallel charging LiPos is complete and you can read it in PRE RELEASE state at this link http://rcaerobase.ipjdev.co.uk/index.php/in-flight/106-method-and-risks-of-parallel-charging-lipo-battery-packs

It's important to add that none of your text or photographs or tables are copied as that would infringe copyright. The Aerobase article, although inspired by your RCM&E article, stands on it's own and has several distinct differences and any comments you might have on it would be greatly appreciated.

By the way it might be worth adding that AeroBase registered users get updates via email when new articles are pre released. This allows registered users to get their comments in early, all leading to improved records before full release.

Finally I would like to say a special thank you for this idea. I now parallel charge my LiPos exclusively and am considering buying a large dc power supply to power all my chargers at once. My goal is to be able to parallel charge all my LiPos in under one hour. Brilliant.

With kind regards,

Bob.

I wish you luck but it is not a good idea to connect balance plugs in parallel. If you have a bad cell or one more discharged that one in parallel with it then the current that flows to try to instantaneously balance them can burn out the tracks on the circuit board and/or the balance wires.

I would not do this. Parallel charge without using the balance connectors and do separate balance charges every so often instead.

[Nigel R]

"Parallel charge without using the balance connectors and do separate balance charges every so often instead."

But then you risk having one low cell in a pack cause the rest of that pack to be overcharged.

Maybe avoided if you assess the state of the pack before connecting everything together?

[MattyB]

Posted by Bryan Anderson 1 on 13/04/2017 14:51:52:

I wish you luck but it is not a good idea to connect balance plugs in parallel. If you have a bad cell or one more discharged that one in parallel with it then the current that flows to try to instantaneously balance them can burn out the tracks on the circuit board and/or the balance wires.

I would not do this. Parallel charge without using the balance connectors and do separate balance charges every so often instead.

Sorry, but I totally disagree. Crucial safety features within modern chargers rely on being able to see the voltages through the balance plug, and you are far more likely to end up with a pack or packs with unbalanced cells, one or more of which could be over 4.2V/cell.

There is far more to lose by not connecting the balance lead than there is to gain. All that is required is to check the cell voltages of all the packs you intend to parallel charge first to validate they are all at roughly the same SOC (within ~0.1V/cell of each other); it takes a few seconds. If they are equal you are good to go. I and many others have done thosands of chages this way without issue. If it is so dangerous, why do the parallel boards come with balance plugs ports at all?

Edited By MattyB on 13/04/2017 17:39:21

[Bryan Anderson 1]

Posted by MattyB on 13/04/2017 17:37:49:

Posted by Bryan Anderson 1 on 13/04/2017 14:51:52:

I wish you luck but it is not a good idea to connect balance plugs in parallel. If you have a bad cell or one more discharged that one in parallel with it then the current that flows to try to instantaneously balance them can burn out the tracks on the circuit board and/or the balance wires.

I would not do this. Parallel charge without using the balance connectors and do separate balance charges every so often instead.

Sorry, but I totally disagree. Crucial safety features within modern chargers rely on being able to see the voltages through the balance plug, and you are far more likely to end up with a pack or packs with unbalanced cells, one or more of which could be over 4.2V/cell.

There is far more to lose by not connecting the balance lead than there is to gain. All that is required is to check the cell voltages of all the packs you intend to parallel charge first to validate they are all at roughly the same SOC (within ~0.1V/cell of each other); it takes a few seconds. If they are equal you are good to go. I and many others have done thosands of chages this way without issue. If it is so dangerous, why do the parallel boards come with balance plugs ports at all?

Edited By MattyB on 13/04/2017 17:39:21

I would not say you totally disagree. I stated the condition when it would be unsafe. You have stated the conditions when it would be safe. Plot them on a Venn Diagram. Not much overlap.

I know that we are always extremely careful but I note that you did not outline what you should do if the batteries fail your conditions and I forgot to add that you could just balance charge the batteries individually.

You must have a rigid flying regime and exceedingly well matched batteries to have them matched to 0.1V after every flight. Even at 0.1V, currents in excess of 10A could flow through the balance leads and distribution board.

[Robert Hynes]

Hi Bryan and Matty,

many thanks for this quick response. Your points are very interesting and will be fully addressed in the article shortly. I will wait a while and first see the full response in case there is more and then address things directly in the AeroBase article crediting you both for your input. Many thanks for taking the time to write. This is delightful for me to read, for it is exactly how AeroBase is supposed to work.

Bob.

[MattyB]

All my larger planes have voltage telemetry, I use multiple timers and I have a fairly consistent flying style with each plane, so yes my batteries do almost always come down between 3.75-3.85V/cell on all but the coldest days. Even if they don't I always stick them on a storage and balance programme on my discharge rig when arriving home anyway. That means they are always going to be starting from a very consistent starting point for parallel charging, though I still always double check cell voltages before initiating the charge. If any are too low for paralleling they get a few mins on the charger individually to even them up ready to go parallel.

Many would consider this overly fastidious, but if you have a high powered dual output charger and a decent discharge rig it is no hassle at all. I can charge everything I need for an afternoons flying in less than an hour and have everything back at storage 30 mins after arriving home even with my biggest 6S batteries; as a result my packs seem to last far longer than people I know who a less rigorous routine. YMMV.

Edited By MattyB on 13/04/2017 20:14:17

[Robert Hynes]

Hi Bryan and Matty,

What is clear from your responses to the AeroBase article is there are differing viewpoints in terms of the risk of damaging balance leads and associated circuitry when running the parallel charge process.

The AeroBase article handles this important point by stressing the absolute need to have the battery packs in an equal state of charge before the charging process begins and explains the point in detail in Step 1 of the Process Table.

Step	What	How	Detail	Why
1.	Equalise the charge level of the LiPo packs to be charged on the paraboard.	Connect the power leads of the LiPos to the paraboard only, leaving the balance connectors disconnected.	This parallel connection of power leads allows equalisation currents to flow between the packs as the battery packs with higher levels of charge transfer that charge to the packs which have lower levels of charge. This process is automatic and self regulating and benign as the currents, (amperes), which flow are well within the packs current limits. While the initial currents which flow in this part of the process can be somewhat high depending on the difference in charge level, they quickly reduce in magnitude as equalisation proceeds.	This ensures that charge transfer does not pass through the LiPo pack balance leads which are designed for low currents only and initial charge equalisation currents could exceed their ratings.

While it is true that parallel charging without using the balance leads does work, (provided your charger allows it), bypassing modern digital charger’s safety algorithms by so doing, is not ideal I feel.

Further what is clear in video 3 in the Aerobase article is that parallel charging with balance leads connected does work really well, is safe and at 1C generates no heat whatever. This is not new of course, i.e. the video merely confirms this is the case.

All that said the anxiety expressed over the balance leads and their circuitry could be discussed in further detail in the article to ease such fears. I will do that soon.

Meanwhile thanks for the input. I will credit you both for highlighting the point in the Revision History of the article after I make the additions.

[Bryan Anderson 1]

Bob Hynes

It is better but I still have reservations about getting used to just connecting things up and charging. It would be OK most of the time but might cause problems if a battery cell went bad. It happens.

Step 0: before connecting anything, check that the cells within a battery are very nearly in the same state of charge. Otherwise, connecting batteries might cause the more fully-charged cells of a poor battery to get driven over voltage when connected to a better one. Not very likely, I admit, unless the good one is nearly fully charged. People should be keeping close eyes on the health of their batteries.

I would also want the batteries to be at similar terminal voltages otherwise the transfer of charge between batteries is not well limited. Even 3S 2200maH batteries that have open-circuit terminal voltages that differs by 300mV can sustain currents in excess of 30A for possibly up to a minute when connected in parallel. That is about a 14C charging rate.

What is the current rating of the copper trace connecting the power connectors on the paraboard? It may have been specified (a joke?) for the charging role only and considerations such as the above neglected. It might be prudent to solder some stout copper wire along the traces to minimise the risk of them being damaged. Ask me how I know that circuit-board traces can burn out.

Finally, you cannot know how the charging current gets distributed between the batteries. It depends on their internal, equivalent serial resistances. The battery with the lowest internal resistance will tend to hog the charging current at least initially especially since these resistances seem to have a negative temperature coefficient, that is, the resistance drops as the temperature rises. Your nominal 1C charging rate per battery will only be a very rough estimate.

Can you tell that I don't get out much? Too risky. I will shut up now.

[Robert Hynes]

Hi Bryan and Matty,

your inputs have been valuable in writing this AeroBase article. The interesting thing for me is your different viewpoints.

Your concern Bryan with all things safety mirrors my own but Matty's viewpoint although different is also valid. This left me with a problem of how to adjust the article while addressing both viewpoints. I've tried to accomplish this by adding section 6, What can go wrong and how to avoid it. This seeks to address your concerns Bryan.

In addition to this, for every point in the list I have added a risk assessment so that the reader can have some idea of the likelyhood of the problem occurring. This seeks to address your differing viewpoint Matty.

I believe the article now covers your points but please remember all AeroBase articles are dynamic, and they can be changed at any time by comments from registered users or via resources like The Model Flying Forum, as in this case.

Many thanks for your help with these inputs.

Bob Hynes.

[MattyB]

Bob, after reviewing the article itself and your comments above regarding my "viewpoint" on safety I have decided I would like my name removed from the credits. Nothing personal, I just want to avoid a situation where a reader follows (or attempts to follow) this advice, has an accident and tries to hold the authors/contributors responsible. Please confirm with a post here that you have removed my name - many thanks.

I strongly suggest you add a disclaimer to the top and bottom of this article stating that whilst every effort has been made to check it for errors, responsibility for the safe setup and use of their charging equipment remains with the reader.

Edited By MattyB on 20/04/2017 13:41:39

[Robert Hynes]

Hi Matty,

thanks for this. As requested I have removed your name from the credits but thank you for your input none the less.

While we have a strong safety warning in the article itself and a very strong generic safety disclaimer on the home page of the website, we feel on reflection this can be further enhanced after reading your suggestion above, so many thanks for taking the time to write it.

[MattyB]

Many thanks