Can we talk about charging rates?

[chilly81]

they balance the same way one battery balances... all the batteries balance leads connect to the board in parallel so the charger balances them simultaneously. the charger doesn't know you are charging batteries in parallel and the other batteries don't know they are connected together.

Also, the balance current limit is split across the parallel batteries. So you might have 25 A worth of bulk, charging power, it’s unlikely you have more than 1.5 A of balance in current per channel. So the balance phase will take longer than it would for an individual battery. For me typically charging two big packs like 6S 5000mah the balanced phase still only takes a couple minutes at most for healthy batteries though. But that time it is twice as long as it would be for just one of those two batteries.

 

[dure16]

they balance the same way one battery balances... all the batteries balance leads connect to the board in parallel so the charger balances them simultaneously. the charger doesn't know you are charging batteries in parallel and the other batteries don't know they are connected together.

Would this process only work if all connected batteries are exactly the same?

 

[ChemEng]

Also, the balance current limit is split across the parallel batteries. So you might have 25 A worth of bulk, charging power, it’s unlikely you have more than 1.5 A of balance in current per channel. So the balance phase will take longer than it would for an individual battery. For me typically charging two big packs like 6S 5000mah the balanced phase still only takes a couple minutes at most for healthy batteries though. But that time it is twice as long as it would be for just one of those two batteries.

depends on the charger, but the current flows through the big connector for the bulk of the charge. It will utilize the balance leads only for fine balancing at the end of the charge. It shouldn't take much longer for 6 batteries than it does for 1 as long as your batteries are healthy. If you have one cell with high internal resistance then it will significantly slow it down, but that would be apparent when you check cell voltage at the end of a run and that battery should be retired anyway.

 

[chilly81]

depends on the charger, but the current flows through the big connector for the bulk of the charge. It will utilize the balance leads only for fine balancing at the end of the charge. It shouldn't take much longer for 6 batteries than it does for 1 as long as your batteries are healthy. If you have one cell with high internal resistance then it will significantly slow it down, but that would be apparent when you check cell voltage at the end of a run and that battery should be retired anyway.

Well, if you have enough power, you can bulk charge six batteries in 1/6 of the time when you charge them in parallel. If at the end of the bulk charge phase, you are 0.1 V low across one cell on all six batteries, that having them on a parallel board will do you no good than simply balancing them one at a time. That is not true for the balance phase though, only the bulk charge phase.
All the chargers have a published balance current limit. It’s not specific to any particular modern charger, they all pretty much work, the same way, you cannot balance charge through the mains without tapping excess power out through the balance connectors on the high cells. And that is your current limit.

 

[RedOctobyr]

I highly recommend a protected parallel charging board. This one protects the XT60 and the balance lead from overcurrent... just need xt60 adapters for whatever you have on your batteries.

This will protect you if you plug in a fully charged battery with a fully discharged battery.

https://pyrodrone.com/products/strix-ultimate-joshua-bardwell-parallel-charging-board-2-6s

That looks nice! I have safe (fully-fused) parallel boards from ProgressiveRC. Like these (this one has XT90, they have XT60, EC5, etc);

https://www.progressiverc.com/colle.../products/safe-parallel-board-for-jst-xh-xt90

I've never tried to test it by connecting charged & discharged. But the main leads are fused, as are each main connector, and it has self-resetting fuses on each balance wire (for each pack). But no voltage display, though.

 

[chilly81]

I highly recommend a protected parallel charging board. This one protects the XT60 and the balance lead from overcurrent... just need xt60 adapters for whatever you have on your batteries.

This will protect you if you plug in a fully charged battery with a fully discharged battery.

https://pyrodrone.com/products/strix-ultimate-joshua-bardwell-parallel-charging-board-2-6s

Hey I have an older model 4S-only one of those from JB from my drone days. He's the best resource around - both info and products - to understand how all this stuff works. I've cheaped out on my other boards though. I have smoked a board just from an accidental bump of the wrong pin somewhere and poof. Board smoked way before the battery wires even warmed up, so that's good at least... so maybe a tiny bit self protecting, even if destructive.

I just started using a full power gauge Y connector because I typically am only doing 2 big 4S or 6S batteries in parallel per channel at a time and it's easier to manage (charging in a batt safe), but now you make me realize that's really playing with fire and I think I'm going to stop doing that.

 

[RC-Dude]

I use this one:

ISDT Parallel board

Batteries need to be the same and have a similar voltage and same cell number. It has 32 SMD fuses and all balancer connections are secured against each other. Max is 40 AMPs. I stay at max 1C when I use it so the balancing among all the lipos is no problem.

 

[ChemEng]

Would this process only work if all connected batteries are exactly the same?

They all need to be the same number of cells and they need to be discharged to about the same voltage… +/- 0.1V per cell or so.

But you can balance charge a 5,000 mah 6s pack with a 10,000 mah 6s pack no problem.

Well, if you have enough power, you can bulk charge six batteries in 1/6 of the time when you charge them in parallel. If at the end of the bulk charge phase, you are 0.1 V low across one cell on all six batteries, that having them on a parallel board will do you no good than simply balancing them one at a time. That is not true for the balance phase though, only the bulk charge phase.
All the chargers have a published balance current limit. It’s not specific to any particular modern charger, they all pretty much work, the same way, you cannot balance charge through the mains without tapping excess power out through the balance connectors on the high cells. And that is your current limit.

Not sure I follow, maybe we are saying the same thing? but parallel charging 6 batteries will take you as long as it would take you to charge the “worst” of the 6 batteries alone.

 

[chilly81]

Not sure I follow, maybe we are saying the same thing? but parallel charging 6 batteries will take you as long as it would take you to charge the “worst” of the 6 batteries alone.

If you have 2 batteries that both happen to have the same single cell low by 0.1V at the completion of the bulk charge phase (when first cell hits 4.2), if you are parallel charging, the balance phase will take 2x as long as if you had the two batteries on separate channels. Just the balance phase. Parallel helps the bulk phase because the charger is artificially limiting the current (you setting it to charge at 1C). In the balance phase, the charger is limited by it's circuitry to a very small (relative to bulk charge) current on the balance plug circuits. Because each battery wants the whole 1.5 amps for itself during the balance phase, but there's not enough, so they have to share that, unlike the bulk phase.

 

[ChemEng]

If you have 2 batteries that both happen to have the same single cell low by 0.1V at the completion of the bulk charge phase (when first cell hits 4.2), if you are parallel charging, the balance phase will take 2x as long as if you had the two batteries on separate channels. Just the balance phase. Parallel helps the bulk phase because the charger is artificially limiting the current (you setting it to charge at 1C). In the balance phase, the charger is limited by it's circuitry to a very small (relative to bulk charge) current on the balance plug circuits. Because each battery wants the whole 1.5 amps for itself during the balance phase, but there's not enough, so they have to share that, unlike the bulk phase.

Yes, but this kind of situation where you have a significant imbalance shouldn’t happen.

In an ideal world our batteries shouldn’t become imbalanced… you aren’t balance discharging after all. At the end of a run all your cells should be damn close to the same voltage. That’s how @chilly81 has been able to get away with just using a Y instead of a balance board, but he will only get away with it for so long.

In reality, even in new, quality batteries there are small differences in internal resistance that cause each cell to charge or discharge at a slightly different rate. Over many charge/discharge cycles the voltage in each individual cell can creep out of range of each other. That’s why you balance charge every time, to prevent that creep and inevitable overcharge of a cell.

If the balance phase is taking a long time to complete (for one battery or several in parallel) then there is a problem and you need to figure out why.

Check voltage in all of your cells after each run. If one of your cells is constantly out of range with the others then it might be time to retire it or repurpose it for a lower amp draw application. OR Maybe you are pulling voltage off cells 1-3 for some high power cooling fans or BEC that only can take 12V in which case you just need to live with the extra balance charge time or run an appropriate step down converter.

 

[chilly81]

In an ideal world our batteries shouldn’t become imbalanced… you aren’t balance discharging after all. At the end of a run all your cells should be damn close to the same voltage. That’s how @chilly81 has been able to get away with just using a Y instead of a balance board, but he will only get away with it for so long.

Oh, I should clarify that I also have a balance cable splitter. So I’m only avoiding having the actual physical board in my batt safe but it’s working exactly the same as a balance board. But what you said is true if I was just using a splitter. The only real difference is that if I screw up, that Y adapter will carry 200 A and potentially cause big problems whereas a balance board would probably just smoke itself with 10 or 20 A if I had to guess.

But yes, what you’re generally saying is true. I was just discussing in detail how the balance circuits work, which is almost universally misunderstood.

Yes, it is true. In normal use your cells will not drift much if you continue to balance charge them. Except when one cell starts to fail, then it definitely will, and that really is the point - knowing when it’s a reasonable short period of balancing versus, it’s a battery going bad, that’s taking too long to balance. I’m simply pointing out That second case, when the batteries going bad, will be highlighted more in parallel charging
Because of the limited current, the charger can provide in the balance phase. But everything else you said is true so it’s not really an important detail.

 

[ChemEng]

Here is an example of a battery that was bad out of the box it was a ZOP from bangood (they actually sent me a new one based on this pic, which was surprising). Cell 3 is an order of magnitude different ir from the other 2. It came with 3.0 V on that cell and 3.8 on the other 2.

Here i am charging 40k mah worth of 4S batteries at my charger's max rate of 20 A (so 0.5C). Still faster than charging individually:

I actually use 3 chargers and balance boards so i can balance charge 3S, 4S and 6S batteries simultaneously. One of the chargers is dual channel so i can charge specialty batteries too (like the Lion for my monster promodeler servo in the Xmaxx.)

So if you really want to charge fast, just buy more chargers

 

[dure16]

Here is an example of a battery that was bad out of the box it was a ZOP from bangood (they actually sent me a new one based on this pic, which was surprising). Cell 3 is an order of magnitude different ir from the other 2. It came with 3.0 V on that cell and 3.8 on the other 2.

View attachment 284334

Here i am charging 40k mah worth of 4S batteries at my charger's max rate of 20 A (so 0.5C). Still faster than charging individually:

View attachment 284337

I actually use 3 chargers and balance boards so i can balance charge 3S, 4S and 6S batteries simultaneously. One of the chargers is dual channel so i can charge specialty batteries too (like the Lion for my monster promodeler servo in the Xmaxx.)

So if you really want to charge fast, just buy more chargers

That charging case is fancy! I have the same discharger and it works really well.

 

[chilly81]

So if you really want to charge fast, just buy more chargers

That is always the right answer! I like the box you have around the I SDT charger. Did you make that? It’s just a power supply and all the connectors built into a nice case right? That’s pretty cool.
You can see my y-a splitter in the box on the bottom charging 2 6s. And my Bardwell 4s fused balance board in the middle box. Then just a cheaper one in the top box doing some 3s batteries. Off a hota d6+ and a p6. Plus a isdt p10 off to the side not in use in that picture - but provides more flexibility than balance boards do.

 

[ChemEng]

That is always the right answer! I like the box you have around the I SDT charger. Did you make that? It’s just a power supply and all the connectors built into a nice case right? That’s pretty cool.

View attachment 284339
View attachment 284341

i love the batt safe stuff, but i would need so many of them... instead i just sit there and do maintenance on my cars while i wait for the charger to beep at me. I keep a welding glove next to me so i can grab whatever starts to puf/sizzle and throw it out of the garage if needed.

I actually keep all my batteries in my garage refrigerator when not in use. At ~40 degrees F and at storage charge, it is extremely unlikely they would start a fire even if punctured.

That charging case is fancy! I have the same discharger and it works really well.

that discharger is NECESSARY... nothing like breaking your car on the first of 6 big batteries only to have to come home and discharge 40k mah at 1 A on the normal charger.... no thanks (oh, and i balance discharge too).

That box is from Turtle Labs... i don't think they make them anymore, but looks like many others do.... in fact, they just made the metal plate, and i had to buy the rest of the stuff to get it to work. The challenge was fitting a power supply in there that could drive the 20A at 24 V to get the max out of that charger.

I use it for field charging Lipos for FPV Quads

 

[chilly81]

i love the batt safe stuff, but i would need so many of them... instead i just sit there and do maintenance on my cars while i wait for the charger to beep at me. I keep a welding glove next to me so i can grab whatever starts to puf/sizzle and throw it out of the garage if needed.

I actually keep all my batteries in my garage refrigerator when not in use. At ~40 degrees F and at storage charge, it is extremely unlikely they would start a fire even if punctured.

View attachment 284342

Yes, that is a problem… I want to get another pair of big 4s batteries, but they would need a whole new box just for themselves. I’m shifting to be able to charge in the field more.

So at home in the morning I can charge the loadout shown in that picture in one batch at 1C… Four or 5 3s-5k, 2 big 4s-7k, and 2 6s-5k. Then instead of just having more batteries, I have a little old Honda generator. I’ll put in my truck. I may get big LIFE battery to play that role in the future.
But yeah, you’re right that storage charge batteries just sitting there are not much risk. I mainly want the boxes for semi unattended, charging in my garage. And then I go out and just look at things every 10 minutes. Make sure nothing is getting hot or has weird charging numbers going on.

 

[ChemEng]

Yes, that is a problem… I want to get another pair of big 4s batteries, but they would need a whole new box just for themselves. I’m shifting to be able to charge in the field more.

So at home in the morning I can charge the loadout shown in that picture in one batch at 1C… Four or 5 3s-5k, 2 big 4s-7k, and 2 6s-5k. Then instead of just having more batteries, I have a little old Honda generator. I’ll put in my truck. I may get big LIFE battery to play that role in the future.
But yeah, you’re right that storage charge batteries just sitting there are not much risk. I mainly want the boxes for semi unattended, charging in my garage. And then I go out and just look at things every 10 minutes. Make sure nothing is getting hot or has weird charging numbers going on.

i also added a fire alarm in my garage (not sure why this isn't required) that is networked to the other alarms, so if something does happen at least i'll be alerted, and if i have to charge unattended, i do it in the middle of the driveway.

 

[RedOctobyr]

40Ah of batteries?? Dang! Nice setups everyone. And one benefit of parallel is just the hands-off aspect. Even if (being power-limited, etc) parallel charging 6 packs took as long as 6 individual charges (doubtful), it's still just a single operation. Not needing to listen for 6 individual charges to finish, and wasted time before you go over to swap packs. Start it, and let it go.

I was pushing my iCharger 308Duo harder with helicopter use, different sizes of 6S packs, charging quickly at the field. But for ground use, it's been easier so far (lower currents), and the longer run times don't require quick charges so far. For charging at the field, it's worth considering an inexpensive inverter generator. I got a used Honda EU2000i for half of new, and it can max out my 1300W charger (it's rated for 1600W continuous). It sips gas (4-10 hours per gallon, based on the load), and is really quiet, you can have a conversation next to it. I'd bring it to a park, etc, and have it running maybe 50 feet away or whatever, you'd barely even hear it.

More versatile than a big battery, too, like using it for extended power outages, camping, whatever.

 

[chilly81]

40Ah of batteries?? Dang! Nice setups everyone. And one benefit of parallel is just the hands-off aspect. Even if (being power-limited, etc) parallel charging 6 packs took as long as 6 individual charges (doubtful), it's still just a single operation. Not needing to listen for 6 individual charges to finish, and wasted time before you go over to swap packs. Start it, and let it up.

I was pushing my iCharger 308Duo harder with helicopter use, different sizes of 6S packs, charging quickly at the field. But for ground use, it's been easier so far (lower currents), and the longer run times don't require quick charges so far. For charging at the field, it's worth considering an inexpensive inverter generator. I got a used Honda EU2000i for half of new, and it can max out my 1300W charger (it's rated for 1600W continuous). It sips gas (4-10 hours per gallon, based on the load), and is really quiet, you can have a conversation next to it. I'd bring it to a park, etc, and have it running maybe 50 feet away or whatever, you'd barely even hear it.

More versatile than a big battery, too, like using it for extended power outages, camping, whatever.

I just have the 1000W version of the Honda. I think it is sustained 800W? I can overload/shut it down with my 1000W DC PS if I put all my chargers on full blast, but it doesn't hurt anything - just shuts down. Around here (dense populated New England) you are still going to get glares if you start up a generator - even a quiet one - in a lot of places. But you can always just take a break and drive a 1/4 mile away and recharge everything and come back if it's one of those spots.

One good feature about the LiFe batteries is they aren't dangerous like LiPo's and don't suffer if you leave them at full charge indefinitely. So you could just leave it fully charged in your truck until you ever actually need it, instead of loading up the genny every time... or trying to decide if today's a 'big day' to bother with the genny or are you just going to run a few packs. That's where the battery would be convenient. But a generator is super handy in a lot of other situations too... a great tool to have overall. Tradeoffs!

 

[ChemEng]

40Ah of batteries?? Dang!

lol that’s just my 4S car batteries.

Doesn’t include my 3s or 6s or any of my flight batteries.

Here is my largest and smallest I use for RC: