What is parallel charging?

In a nutshell parallel charging allows for multiple same cell count batteries to be connected in parallel to create a single larger logical battery that can then be charged. The following is my experience about 5000mah 2s lipo parallel charging.

With cells in series, and no balance lead, your charger has no idea how much voltage is in an individual cell; it only knows the total voltage. If it reads 7.4V, that might be cell 1 with 4.2V and cell 2 with 3.2V, or it might be cell 1 with 3.7V and cell 2 with 3.7V, or it might be something else. Unless the charger connects to the balance lead, it just doesn’t know. So, let’s imagine it’s the first case. You start charging, with cell 1 at 4.2V and cell 2 at 3.2V, and the charger says, “ok, I need to see 8.4V before I stop, so I’ve got a long ways to go,” when in actuality it is going to overcharge cell 1 and possibly blow it up or catch it on fire, and definitely it is going to ruin or at least damage cell 1 at a bare minimum. That’s where active balancing comes in. Cells in series must be *actively* balance by a smart charger, to get them to be equal.

However, here’s what you’re missing still: cells in parallel do *not* need active balancing by a smart charger. Rather, they naturally, by the laws of physics, will perform passive balancing. Cells in parallel automatically, passively, due to voltage gradients (differences), self-balance until they are equal. If you take 2 individual LiPo cells, and place them in parallel, and wait long enough, no matter what voltages they *were*, they will equalize, automatically, to become *equal* voltages over time. One will discharge into the other, until they are equal.

So, in your case of 7.4V LiPo battery, when you place the whole packs in parallel, and the balance leads in parallel too, cell 1 of pack 1 is placed in parallel with cell 1 of pack 2, so both cell 1’s will automatically, by the laws of physics, passively balance until they are equal. Both cell 2’s will also passively balance until they are equal, since cell 2 of pack 1 is also in parallel with cell 2 of pack 2. However, both cell 1s (as if a large single cell) are still in series with both cell 2s (as if a large single cell), so *active* balancing is still required here, to get the cells in *series* actively balanced, and that’s where the smart charger does its job.

Therefore, when charging in parallel, you are still getting all 4 cells to be balanced, just as if you were not charging in parallel.

What are some specific uses of parallel charging?

450 sized heli:
Many times people start with a 450 sized heli and in the beginning they can not get enough flight time. This is what we call the “Welcome to your new addiction” stage. Parallel charging can be a great aid to the new pilot. For example with a 350W charger a 6x parallel lead set, a new pilot could charge 6 450 packs in 30min.

700 sized heli:
Larger electric helis are becoming very popular and they come with large needs in terms of power. A common battery pack for a 700 is a 4s lipo batteries made up of (2) 6s 5000mAh packs wired in series. Due to the lack of 12s chargers available, a need for charging pairs of large 6s packs has arisen. Of course you could use 2 chargers, or a dual port charger, but there is another solution, a solution that really brings out the best on the new powerful chargers offering 1000W or more of output. By using one of these new 1000W chargers and parallel charging, you can charge a pair of 6s 5000mAh packs in 25min or less.

Remember to be careful about large voltage gradients (differences), however, as the passive balancing can be quite fierce (and potentially damaging or even dangerous), if cell voltage differences are too great before being placed in parallel–refer back to my article for warnings & recommendations on this.

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Gens Ace 2200mAh Battery Pack

To test the 4 cell 5s lipo battery I used my E-flite Extra 300 equipped per E-flite’s recommendations. It has an E-flite Power 32 motor with 13 x 6.5 prop and a 60 Amp ESC. For charging I used the E-station BC-8 balance charger. Per my charger the opening voltage per cell on this four-cell pack had three cells at 3.96V and one at 3.97V. I charged the pack right out of the box at 1C and it took about 41 minutes to get the pack to a full charge by adding 1528 mAh to the pack. With my pack fully charged I flew my Extra 300 for five minutes, and I used 1458 mAhs during that five minute flight. After landing, I felt the pack and it was cool to the touch. Part of that flight can be seen on the video below. I flew with a mixture of throttle. It had plenty of power throughout the flight and I did nothing to break in the battery pack before the flight.

Gens Ace 5000mAh Battery Pack

The lipo 5000mah are designed for use with small scale RC helicopters as a replacement batteries for the originals upplied with the compatible radio controlled model. The Gens ace brand by Genstattu (one of the largest online RC model stores) so far got us with mixed results when testing different batteries, for example LiPos often turn out to be with overrated specs than what they really can provide, but with the Gens Ace Lipo for example we got very good results. So let us see what this Turnigy Nano-tech LiPo battery can provide in our tests.

I have had great success with Gens Ace lipo packs from Genstattu, I found them to consistantly outpreform every pack I ave compared them with, my new 285 setup pulls ~100A in flight and the only packs I have that fly without damage are the 75c 1300mah and 45C 1800mah.

Some tips For testing Lipo battery

1. Charge your LiPo battery pack in the usual way until fully charged. Remove the battery pack from the charger once charged.
2. Look on the label on the LiPo battery pack. You need to find out the output voltage and mAh rating. The voltage figure is always a multiple of 3.7 and the mAh always a multiple of 2,100. For example, a LiPo battery pack using three cells has a voltage of 11.1 and mAh of 6,300. The figures on the label are the figures you can expect to get when you test the battery using the multimeter.
3. Set the multimeter to read voltage. Check the two terminals on the battery pack to determine which is positive and which is negative. They are labeled “+” and “-” respectively.
4. Place the metal sensor attached to the end of the red wire that extends from the multimeter onto the positive LiPo battery terminal. Place the metal sensor attached to the end of the black wire extending from the multimeter onto the negative battery terminal.
5. Read the voltage output on the multimeter display. It reads the same as on the battery pack label. If the voltage is more than five percent less then it’s likely the battery is losing charge quickly as you have only just charged it.
6. Set the multimeter to measure mAh. Place the two sensors on the battery terminals as before. Read the mAh on the multimeter display. It is the same as the label on the LiPo battery. If the mAh is more than five percent below the figure on the label it’s likely you have a problem with your battery pack as it should not lose energy after just getting charged.
7. Leave the LiPo battery overnight. Do not use it as you need to see if it loses charge while not in use. A good battery pack has the same readings the next day.
8. Repeat the voltage and mAh test using the multimeter in the same way as before. The readings are identical, if the LiPo battery pack is in good condition. If either the voltage or the mAh readings have reduced by more than 5 percent then you need to consider getting your LiPo pack refurbished or replaced as you will find it gradually gets worse.

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Lithium Polymer Batteries (LiPo’s) have now been with us for many years and have become an essential part of this hobby. Their low discharge rate is perfect for devices that don’t draw considerable current, and the cell’s compact footprint makes them easy to squeeze into tiny devices. The challenge with LiPo batteries lies in their charge and discharge profile because unlike nickel or lead-based batteries, LiPo cell voltage is not self-limiting. Without a specifically designed charger, the battery voltage would continually increase until it bursts into flames (a generally frowned upon outcome in electrical design). Discharging LiPo batteries without proper protection is only marginally better, and will result in cell damage without restricting the operating voltage to a very specific range. If you want to test the condition of your LiPo battery pack then use a multimeter and you can test the voltage and mAh.

Look on the label on the LiPo battery pack. You need to find out the output voltage and mAh rating. The voltage figure is always a multiple of 3.7 and the mAh always a multiple of 2,100. For example, a LiPo battery pack using three cells has a voltage of 11.1 and mAh of 6,300, it is 5000mah lipo 2s. The figures on the label are the figures you can expect to get when you test the battery using the multimeter.

Measuring Voltage

To start, let’s measure voltage on a AA battery: Plug the black probe into COM and the red probe into mAVΩ. Set the multimeter to “2V” in the DC (direct current) range. Almost all portable electronics use direct current), not alternating current. Connect the black probe to the battery’s ground or ‘-’ and the red probe to power or ‘+’. Squeeze the probes with a little pressure against the positive and negative terminals of the AA battery. If you’ve got a fresh battery, you should see around 1.5V on the display (this battery is brand new, so its voltage is slightly higher than 1.5V).

If you’re measuring DC voltage (such as a battery or a sensor hooked up to an Arduino) you want to set the knob where the V has a straight line. AC voltage (like what comes out of the wall) can be dangerous, so we rarely need to use the AC voltage setting (the V with a wavy line next to it). If you’re messing with AC, we recommend you get a non-contact tester rather than use a digital multimeter.

Set the multimeter to read voltage. Check the two terminals on the battery pack to determine which is positive and which is negative. They are labeled “+” and “-” respectively.

Read the voltage output on the multimeter display. It reads the same as on the battery pack label. If the voltage is more than five percent less then it’s likely the battery is losing charge quickly as you have only just charged it.

Set the multimeter to measure mAh. Place the two sensors on the battery terminals as before. Read the mAh on the multimeter display. It is the same as the label on the LiPo battery. If the mAh is more than five percent below the figure on the label it’s likely you have a problem with your 14.8 lipo battery pack as it should not lose energy after just getting charged.

Leave the LiPo battery overnight. Do not use it as you need to see if it loses charge while not in use. A good battery pack has the same readings the next day.

How to test for aging lipos

As a possible rule of thumb, you might find that if a 3s has an IR more than around 50-60 milliohms, it is probably past its best. Based on my experience with 6s lipos, they seem to show other signs of aging before getting up to around 20 milliohms per cell (like the 3s), so perhaps around the same value 50-60 milliohms for the 6s pack as well.

The overall % of capacity seemingly dropping (ie. the charger will tell you that you pack has, say 20% left when you put it on charge, and yet you only took out 62% based on mAh put back in compared with rated mAh, so it only adds up to 82%)

You can’t measure the battery voltage without taking the battery packs apart because the voltage converter in the battery pack will provide a constant voltage (5.0V for USB, etc.) regardless of the battery voltage. However, you can estimate the battery voltage by determining when the power packs shut off. Lipo and li-ion cells are considered depleted when then fall below 3.3-3.5V, so the circuitry inside the battery pack should shut off then.

If you have direct access to the cells, you can also rely on the voltage info given by your hobby charger. When discharging, the Accucel displays the voltage, and that’s the battery voltage under load.

In this tutorial, I’ll be going over everything you need to know in order to charge multiple lipo batteries. by basically using just one part that you don’t already have called a parallel charging board, you’ll be able to charge up to 6 Lipo batteries all at the same time.

How It Works

Here’s a detailed schematic of a harness used to charge two 3s 11.1v lipo in series. In series, the positive of the bottom battery is connected to the negative of the upper battery. Notice how this connection is made twice, through both the power harness and the balance harness. More on this later.

How To Para Charge

First you will need to build or purchase a parallel charge plug or board that the charge leads from each battery will be plugged into. The positive from each plug is hooked to positive and the negative of each plug is hooked to negative (parallel circuit). To keep things in reason, most will only build a plug or board that will support up to 5 or 6 batts maximum.

Things start to become a little congested as you can see with that amount of wiring and batteries, especially if you still want to use a fire safe charge container or bag.

My general rule is it’s better to charge in parallel. With parallel charging, the batteries must have the same number of cells and a similar state of discharge. The same number of cells rule is easy for me because I keep all of my battery pairs permanently connected. For example in my Revo, my 2s batteries are wired together in series all the time. My ESC only has one plug for the batteries. Same thing goes for a pair of my 4s 14.8 lipo battery. They are permanently wired together in parallel. So regardless of the single pack configuration, all of my battery pairs are 4s before they hit an ESC or a charger. Makes life easier.

Here’s an example of two of my 4s lipos “permanently” wired together. The stay connected to this harness all the time. In these pictures, I have a protective cap installed on the balance plug. This keeps that connector clear while I’m driving.

Requirements and recommendations for serial charging

• Serial wiring adapter for the main leads that matches your charger’s output capabilities. Because serial charging effectively creates a larger cell count pack, the capabilities of the charger will limit the number of packs that can be charged in series. For example a 6s capable charger can charge 2x 3s pack in series. Charging 2x 4s packs in series would require an 8s capable charger.
• A wiring adapter for the balance leads is basically required and needs to have the same number of connections as the main leads adapter.
• All the packs you charge in series must be the same capacity. For example you could charge a 3s 2200mAh lipo, a 2s 2200mAh lipo and a 4s 2200 mAh lipo in series together, but you can not charge a 3s 2200mAh lipo in series with a 3s 3200mAh lipo.
• All the packs to be charged in series together need to be very close to the same voltage per cell. If I had to put a number on it I would say within .05V per cell.
• Serial charging is best suited for someone looking to charge flight packs made up of pairs of packs like 2x 3s 2200mAh packs used in a 500 sized heli.

Things You Should Not Do

1. Because the lipo cells are connected to each other throughout multiple batteries, you should never plug in a fully or half charged battery with a battery that’s dead. Basically, the farther apart the voltages are, the hotter the wires will get. So all of the batteries should be hovering around the same voltage.
2. Another important thing to remember, is that you can’t charge two completely different batteries with each other. You can mix lipo packs from different brand names, but the cell count needs to be the same, and the battery capacity needs to be the same.

if i understand this right a 3s 2000mAh 10c 12.4 battery contains inside it 3x 1 cells 2000mAh 10c ~4.15v packs (safe recommended charging voltage). So with those Lipo batterys that are now showing up i could take apart a larger pack like a Gens 500mAh 2s 7.4v 65c – 130c to get 2x 500mAh 65c – 130c ~4.35v (can be safely charged to 4.35v per cell) for a single cell rc model and say run in a hubsan quadcopter as a example provided it fits. This would be a massive improvment over the stock batterys of most single cell quads right? slightly higher volts with high discharge giving way more power at a cost of weight.

That’s it!

Hopefully this short guide gave you some idea what multiple charging is, and how to do it on your own in a safe fashion.

When talking about balancing Li-Po battery packs, we’re not talking about finding their correct Centre of Gravity! Instead, the balance refers to the voltage of each cell in a pack relative to the other cells.

Balancing is required however on any RC LiPo battery pack that has more than one cell since the charger can’t identify from different cells and know if one might be overcharged even though the total voltage of the pack indicates otherwise. For example let’s look at a 3s 2200mah pack (three LiPo cells hooked in series or 3S). A two cell is equal to 7.4v lipo pack, a three cell is eqaul to 11.1 volt pack – and so on.

How long it takes to balance charge is going to depend on how deeply you discharge it. The GT Power A6 is a 50 watt charger, on 4S the max rate it will charge is roughly 3.3 amps at the beginning with a completely discharged pack, and go down to 3.0 amps as it approaches full. As any of these CC/CV chargers reach the end of the charge the voltage drops to a constant level and the amperage is reduced as it tops off the cells, and usually balances them at this time as well. The following we mainy talk about the 5000mah lipo battery balanced.

Let’s say you had completely discharged 11.1v 2200mah lipo, charging at an average of 3 amps, this is roughly a 6/10C charge. That charge rate would take 1 hour and 40 minutes just to replace the 5000mah, but, will take slightly longer as the charge rate slows at the end, and the cells are balanced. Assuming it’s a good pack, 1 hour and 50-55 minute would be a good estimate. The reality is, you don’t ever want to be putting 5000mah back in, rather 4000mah. That would mean you aren’t discharging more than 80% out of the pack. That would drop your charge time for that pack down to 1 hour and 20 min in theory, but more like 1 hour 30-35 min after the CV phase and balance finishes.

On the other end of the spectrum is if there is one cell in the pack that is not reaching full charge when the pack is charged and then gets discharged below 3.0 volts under load even though the 3 cell battery pack is indicating a voltage of 9 volts or higher.

Balancing ensures all cells are always within about 0.01-0.03 volts per cell so over charging or discharging of one or more cells won’t ruin your battery pack, or worse become a safety issue from overcharging a cell.

You don’t have to balance your RC LiPo battery pack each time you charge it. Most will agree every 10th to 20th time is fine with a healthy battery pack. The problem is knowing if your pack is healthy, cells in older packs may become unstable? As far as I am concerned, if you have a good balancer or balancing charger, use it at every charge, or at least at every 2nd charge. That might be overkill, but if it prevents a damaged battery or fire just once… well, you decide.

Balancing Li-Po battery packs should be done regularly and you should get in to the habit of checking the balance often. A poorly balanced pack will give poor performance, and in the worst case scenario will be damaged beyond repair over time. It’s also important to understand that lithium polymer battery packs vary greatly in quality between brands, and it stands to reason that a better quality pack will probably balance better and stay balanced longer than a cheaper, lower quality one. Mentioned Lipo battery brands, here we can talk about Gens Ace lipo battery, they are the famous brand manufacturer in the world, choose Gens ace for you car, it is the right choice.