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Old Jan 23, 2011, 08:35 PM
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Which cells in 6 x 6S Parallel Charging

When I charge multiple packs in parallel, how do I see the cells in different packs? I assume the cells displayed in both the PL8 itself, and the computer software is from the first pack in the chain (or last)??? How do I see-- or better yet, can I see-- other packs?
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Old Jan 23, 2011, 09:01 PM
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You don't.

Cells in series = same capacity, higher voltage.
Cells in parallel = higher capacity, same voltage.

The same holds true for batteries of cells - our packs. The entire parallel array of packs looks like one large pack of the same voltage but with the sum of the capacity of all. Add up the capacity of each pack = total capacity.

You'll of course only charge packs with the same configuration meaning the same number of cells, i.e. all are 3S1P or all are 2S1P, etc. Capacities of each pack can differ however.
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Old Jan 24, 2011, 09:57 AM
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Yes, old hat rehash, but thank you. The reason for my question is that with individual parallel balance boards I was hoping that these were individually addressable and I could probe each board to learn about the batteries that are attached to that board. Thanks for your post though.
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Old Jan 24, 2011, 12:13 PM
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Ah, I get where you are coming from and must admit I wondered if the SPA had some interesting capabilities along those lines myself when I first ran across them. That'd be cool functionality indeed but would require smarts on each parallel board and some sort of communications protocol between them and the charger. I've not purchased any of the "safe parallel adapters" as their functional description doesn't include any of that funky goodness.

As I understand it the SPA gives you a polyfuse which acts as an automatic current brake to aid in the case of significant pack voltage differences, 'resetting' itself as the imbalance corrects. And that's it.

The alternative to the SPA is to use a parallel wiring harness (one for the discharge leads, another for the balance connectors for whatever pack configuration you are working with). It would be best to check pack state before hooking them all up to avoid the case of a significant pack to pack voltage potential difference.
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Old Jan 25, 2011, 07:40 AM
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Hi,

As posted in another forum...

The Safe Parallel Adapters add additional safety when parallel charging as follows:

1) Yes, each cell of the pack delivers current through a self-resetting polyfuse. In the event that current should ever exceed 1A to an individual cell in the battery pack, the polyfuse goes to a state of high resitance. This generates heat, and a lot of it.

2) Each polyfuse also has a special adhesive sticker attached to them. The material used contains a special "thermochromic ink". The normal color of the label is red. If the temperature exceeds a certain high temperature, as when the polyfuse is protecting the wiring and the PL8, the color of the label turns black.

3) If you ever see the thermochromic label turn black, disconnect the packs IMMEDIATELY. If you do not, there is a likelihood the batteries will be damaged irreversibly. There is also the potential of fire in this case where the customer ignores the temp indicator label color change.

4) So the combination of the polyfuses, and the high temp indicators are what create the extra level of safety not found in other parallel adapters.

5) Some events that can cause the polyfuses to go to a state of high resistance:

a) customer connects two different cell count batteries together in parallel
b) customer has a pack with a shorted or near-shorted cell or shorted wiring.
c) customer finds a way to connect cells together in a manner that is incorrect, reverse polarity for example.

6) In addition to the Safe Parallel Adapters, the other safety feature utilized, and not found on other brand accessories are the fuses on the main charge leads. Currently, REVOLECTRIX offers the new 40A cables that come equipped with two 40A fuses; one in the red lead and one in the black lead. These protect the batteries, the PL8 itself, and all wiring from the mistake whereby the customer connects the balance leads to the adapter, and then connects the main charge leads from the batteries in reverse polarity. In our opinion, any attempts to charge at high current without the added "last resort" protection of fuses in the main charge leads is frought with peril. Note, always connect the balance leads to the Safe Parallel Adapters first, and then connect the main charge leads together. The PL8 also contains internal surge protection circuitry that discharges the output capacitors in the unit via the balance connectors. This proper sequence of connecting will prevent sparking on the main charge leads when connected.

To answer your question, the polyfuses are self-resetting. This occurs automatically when the connection or battery problem has been removed. The polyfuses will cool quickly. The temp labels may require a bit more time to return to normal "red" color. Also, cell imbalance between two packs connected in parallel via the Safe Parallel Adapters is not likely to trip the polyfuses; at least we have not witnessed this in our testing, even when a fully charged pack is connected to a dead pack. But for the record, we do not advise customers connect fully charged packs with completely dead packs during parallel charging. Although this will likely not create a safey hazard, it might not be good for the life expectancy of the packs. In this regard, even when using Safe Parallel Adapters, best practices still apply.

In summary, the Safe Parallel Adapters will prevent damage to all wiring and the PL8. When used correctly (meaning disconnecting the packs immediately in the event of a black temp label indication), they will prevent fire when used in combination with fused main charge leads. But they will not necessarily prevent damage to the batteries themselves in the event that customer connects different cell count batteries together in parallel, or has packs with shorted or near-shorted cells.
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Old Jan 25, 2011, 08:19 AM
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This is why I am awaiting an FMA answer. Since they created the system, they would be capable of explaining what could/could not be done with the SPA’s.

FMA????
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Old Jan 25, 2011, 08:33 AM
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I appreciate the discussion on the features of the SPA. I am awaiting an answer from FMA about the ability to “see” individual cells of a specific parallel board. When I parallel charge "x" 6S batteries, I can see 6 cells in different states. Are these 6 cells the first pack, the last pack, or an amalgamation of the "X" packs??? There are many ways to perform the board identification (check out Futaba’s S.BUS) and only the software on the other end would need to have smarts to correlate the information for display.
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Old Jan 25, 2011, 09:27 AM
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Howard is from FMA.

You have your answer.
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Old Jan 25, 2011, 10:07 AM
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Hi,

Also, as posted in another forum: I guess I am having trouble getting this across. When two packs are connected in parallel using balance adapters (preferably REVOLECTRIX Safe Parallel Adapters), all of the individual cells are connected together. The PL8 does not see the individual cells any more. But it does not matter. Imagine one cell at 3.8v and another cell at 3.5v. After you connect them together, there is only one voltage, say 3.6v. Current flows between the individual cells to equalize the voltage per ohm's law. The cell with a lower voltage prior to connecting the cells together will receive current from the higher voltage cell (charging the lower cell). Self-equalizing MEANS the cells are self-balancing. Now the PL8 only has to look at each of the the paralleled cell voltages of the pack. By end of charge, the exact same thing is accomplished as what would happen if the packs were charged and balanced separately. There is no dis-advantage to parallel charging from a balancing standpoint.
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Old Jan 25, 2011, 09:29 PM
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Perfect. So the answer to my question is that the cells displayed on the PL8, and the software, is an average of all of the cells across the “N” packs.

While the individual cells do not matter to the PL8, they do matter to me. As a case in point I have several 3S packs, some older, some heavily used and some which should be retired. I had one pack in particular that just did not seem charge well and was always out of balance. I used the PL8 to charge this pack and saw that cell one was… well dead (although it would charge to full voltage, so it appeared to be good to other chargers). I could have charged this in a group of six packs and never known that there was a single sell in this particular pack which had high impedance, and discharged in about one minute compared to the other two cells which had great impedance and discharged at a normal rate.

Now if I could have looked at this particular pack during the parallel charge, I could have seen the impedance issue and the discharge issue… more importantly (and what I am looking for), I could have had a piece of software which would have seen the issues and alerted me that pack “X” of “N” has issues and that I should perform a more exhaustive review of that pack.

I know parallel charging has its place in the world of charging however when I fly, I fly 10-6S, 15-3S, 10-2C batteries in a day ( rarely charge at the field). I purchased the PL8 and a 1500W 24v power supply specifically to parallel charge my packs. Oh, I also purchased 10 safe parallel boards as I was truly purchasing everything for parallel charging.

My batteries run the range of 1C through 6C so the 40A capability of the PL8 coupled with the 60A power supply guaranteed that I could either charge a few at max “C” or a bunch at something greater than 1C.

The moral of this thread is that I (more importantly the PL8 & parallel boards) cannot do what I would like to do… so I will wait for a new parallel charger which can do what I want. LiPos are coming into their own and the chargers which charge them are evolving at the same time.

Thank you for your time and energy with regards to this thread. I know it seems like I didn’t get what you were trying to say, it was just that I was looking for a very specific answer to a very specific question for a very specific reason. Have a great week and an even better weekend.
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Old Jan 25, 2011, 09:48 PM
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Originally Posted by UnixMover View Post
I had one pack in particular that just did not seem charge well and was always out of balance.
This is one of the reasons for the operator to manually check individual cell voltages of each pack before connecting the pack to the parallel harness. A pack discovered to be way out of balance should not be parallel charged. Another reason is if the node wire had broken inside the pack (a common problem), you can only detect that if you check the pack before connecting it to the parallel harness. The charger would not be able detect this condition and there could be an unpleasant result.
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Old Jan 26, 2011, 05:47 AM
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Originally Posted by Gregor99 View Post
This is one of the reasons for the operator to manually check individual cell voltages of each pack before connecting the pack to the parallel harness. A pack discovered to be way out of balance should not be parallel charged. Another reason is if the node wire had broken inside the pack (a common problem), you can only detect that if you check the pack before connecting it to the parallel harness. The charger would not be able detect this condition and there could be an unpleasant result.
Hi:

To be specific, in the case whereby a single balance wire was broken, when charged in parallel with other good batteries, this pack would have 2 cells that would be charged "unbalanced". Not the best situation, but not the end of the world, and not particularly dangerous. My instinct tells me this situation probably happens often in the world of parallel charging.

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Old Jan 26, 2011, 05:55 AM
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Originally Posted by UnixMover View Post
Perfect. So the answer to my question is that the cells displayed on the PL8, and the software, is an average of all of the cells across the “N” packs.

While the individual cells do not matter to the PL8, they do matter to me. As a case in point I have several 3S packs, some older, some heavily used and some which should be retired. I had one pack in particular that just did not seem charge well and was always out of balance. I used the PL8 to charge this pack and saw that cell one was… well dead (although it would charge to full voltage, so it appeared to be good to other chargers). I could have charged this in a group of six packs and never known that there was a single sell in this particular pack which had high impedance, and discharged in about one minute compared to the other two cells which had great impedance and discharged at a normal rate.

Now if I could have looked at this particular pack during the parallel charge, I could have seen the impedance issue and the discharge issue… more importantly (and what I am looking for), I could have had a piece of software which would have seen the issues and alerted me that pack “X” of “N” has issues and that I should perform a more exhaustive review of that pack.

I know parallel charging has its place in the world of charging however when I fly, I fly 10-6S, 15-3S, 10-2C batteries in a day ( rarely charge at the field). I purchased the PL8 and a 1500W 24v power supply specifically to parallel charge my packs. Oh, I also purchased 10 safe parallel boards as I was truly purchasing everything for parallel charging.

My batteries run the range of 1C through 6C so the 40A capability of the PL8 coupled with the 60A power supply guaranteed that I could either charge a few at max “C” or a bunch at something greater than 1C.

The moral of this thread is that I (more importantly the PL8 & parallel boards) cannot do what I would like to do… so I will wait for a new parallel charger which can do what I want. LiPos are coming into their own and the chargers which charge them are evolving at the same time.

Thank you for your time and energy with regards to this thread. I know it seems like I didn’t get what you were trying to say, it was just that I was looking for a very specific answer to a very specific question for a very specific reason. Have a great week and an even better weekend.
Hi:

Of course anything is possible, but by the time you add all the electronics required to do what you want to do, the price of the charger would be too high for this industry, in my opinion. In the long run, you'd be better off adandoning parallel charging altogether and utilize multiple chargers or have multiple individual outputs in one charger. Our original concept for a parallel adapter was quite different from what we ended up manufacturing ultimately. If you go back in time in the PL8 beta thread, you can read about the Smart Parallel Adapter. This was getting closer to the concept you describe. But we abanadoned it. By the time we had something ready to build, we realized it was vastly over-complicated, far too expensive, and would have made for a less reliable overall system, not more reliable. But then, all the original Smart Parallel Adapter was intended to do was check the individual cells before they are connected in parallel.

But here's another issue. Once the packs are paralleled you can not "see" the individual cells. You can't have it both ways. You can't parallel two circuits; while at the same time also see the two circuits individually. Only way is to have 2 separate circuits (2 chargers), or disconnect the cells at intervals to take measurements. To do this you'd need a lot of pretty high powered FETs which then introduces more points of failure, etc, etc.

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Old Jan 26, 2011, 07:31 AM
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An interesting statement, adding this technology would cost too much, then in the next sentence “buy more chargers”. I have 6 good chargers; isl8, isl6, 2 - TP601's, iMAX Quattro, PL8 and then a bunch of really junk ones. How many should I purchase? Where should I set them all up at?

WRT cost, I paid over $800 for the isl8 alone (if I remember correctly). For a charger that would perform the simple tasks I was searching for, the benefit would be worth the cost. As an aside, I paid around $800 for the current PL8 setup I have today—and am damn glad I did. I will suffer with the negatives until someone thinks out of the box and creates a system which IMHO is a small incremental step past yours.

Please do not take any part of this thread from me as a negative comment on your charger. I absolutely love your charger!! I was originally searching for an answer to what is on the display. I only then took the thread to what I was actually searching for, visibility into each cell of each pack.

I appreciate all of the information I have been provided and understand the PL8 much more than I did when I purchased it 12/31/10. I stand by for FMA’s next great innovation.
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Old Jan 26, 2011, 08:45 AM
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Broken Wire

Quote:
Originally Posted by Gregor99 View Post
This is one of the reasons for the operator to manually check individual cell voltages of each pack before connecting the pack to the parallel harness. A pack discovered to be way out of balance should not be parallel charged. Another reason is if the node wire had broken inside the pack (a common problem), you can only detect that if you check the pack before connecting it to the parallel harness. The charger would not be able detect this condition and there could be an unpleasant result.
No broken wire here, high impedance for a single cell. My goal is automation. I would like to spend my time flying, not checking every battery. Time for a change in our charge-fly balance.
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