Amperage
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You've got it backwards. Parallel increases battery life, series increases voltage. Lower resistance requires higher voltage so you are not drawing max amperage.
Nope not got it backwards.
For low ohms as I stated. You need more current. Parallel batteries virtually doubles your current capacity so no danger of drawing too much current from just one battery.
2 20 amp batteries in parallel gives you nearly 40 amps of current capacity.
yes it will increase battery life in the mod but that was not my point. My point was that the user needed more current to safely vape at that low current.
With that coil and series batteries... Well can you say poof goes the coil? Atty glowing? And perhaps batteries slagging.
For low ohms as I stated. You need more current. Parallel batteries virtually doubles your current capacity so no danger of drawing too much current from just one battery.
2 20 amp batteries in parallel gives you nearly 40 amps of current capacity.
yes it will increase battery life in the mod but that was not my point. My point was that the user needed more current to safely vape at that low current.
With that coil and series batteries... Well can you say poof goes the coil? Atty glowing? And perhaps batteries slagging.
nono. he (Robert) means that batteries, when run in parallel, distribute the Amperage drawn amongst themselves. So you're not pulling on one battery @ 28 Amps (or what have you). Each battery would only be asked to dump ~14 Amps (ish . .. . ballpark . .. give-or-take)
oopie. I'm slow to type.
But I'll add this: one should assume that the two batteries run in parallel aren't being drawn upon exactly the same. It's been suggested to me that one go with ~75% of combined Amperage. So, 2 x 20A batts . .. . . = 30A draw seems like a safe margin.
But I'll add this: one should assume that the two batteries run in parallel aren't being drawn upon exactly the same. It's been suggested to me that one go with ~75% of combined Amperage. So, 2 x 20A batts . .. . . = 30A draw seems like a safe margin.
Agreed and of course batteries must be paired and all connections kept nice. Say you are drawing 30 amps or so and one battery in the parallel box loses connection then suddenly a 20 amp battery could have all of the 30 amp load on it.
another possible issue with parallel box mods is say you put one battery in upside down... BIG SUPRISE REAL FAST!
Batteries in series the voltage is added, so two freshly charged gives a nominal voltage of 8.4 (ish)
Batteries in parallel the current is added, so voltage will be nominally 4.2 and the current available will be the sum of the two matched cells.
It's important any time you use more than one cell that they be a matched pair.
Have fun, and be safe!
Why yes, yes it is.
It is more so important to understand what a matched pair is.
Our friend, Mr. Bee (it's Mr. to us mere mortals) touched on it briefly, knowingly (I'd assume) or not with the mention of the 75% rule and why.
When I get my dublin EHEM... errr... maybe ever...
I will be purchasing an 18650 cradle to wire to my hobby charger and a dozen or so identical cells. This way I can get internal resistance readings on the individual cells and pair them up for life accordingly and correctly.
Pairing them doesn't just mean to buy them in pairs, but to match the performance of a pair so they share the load, decrease the chance of failure and/or early failure of one in a pair and greatly increase the chances of both cells in the pair getting to their rated or expected life cycle count.
Internal resistance matching is key to this success. As is capacity. However, capacities have proven to be more consistent among modern lipo tech cells. Only takes one discharge/charge cycle to test a cell, though...
Tapatyped
yip, yep ↑
the other thing too, tho, about pairing batteries (pairing internal resistance, to be precise) is "balancing". When you pair up batteries (in parallel . .. . is all I know about with this topic), they balance each other out. So, if I were to connect + to + and - to - on a pair of batteries and one was charged to 4.2V and the other to 3.2V, the one would dump charge into the other until they were ~equal. This amounts to uncontrolled charging of one battery and uncontrolled discharging of the other. So, if the batteries aren't giving up current at pretty much equal rates (i.e. internal resistance), and if they aren't charged equally to begin with, then not only will one battery be dumping more Amps when you vape; but it will then proceed to get an uncontrolled [rapid?] charge from the other battery. Or so I figure. One way to monitor what's going on in there (in your mod, while you're vaping in parallel) is: right before you go to pull your batts and charge them, take a good series of toots (draw some current) and then pull them instantly from the mod (separate them). Now check their charge. If they aren't showing the same charge, one battery is being used more heavily than the other while you vape. (this could be due to a physical issue in the mod, or internal resistance of batteries.) I'm given to understand that a couple hundredths of a Volt is not an issue ( ~0.02V-ish).
Now then, also, too, and BUT: I just heard P.Busardo mention in one of his recent videos that he had asked his geeky battery friends about all this, and they told him that battery pairing is not nearly as critical or dangerous an issue with parallel setups as it is with batteries in series. ←that's 3rd hand information. Coming from me, like this, consider it the furthest thing from proven fact. So, I wouldn't hang my hat on it; but it's something I'll be curious to hear more about.
the other thing too, tho, about pairing batteries (pairing internal resistance, to be precise) is "balancing". When you pair up batteries (in parallel . .. . is all I know about with this topic), they balance each other out. So, if I were to connect + to + and - to - on a pair of batteries and one was charged to 4.2V and the other to 3.2V, the one would dump charge into the other until they were ~equal. This amounts to uncontrolled charging of one battery and uncontrolled discharging of the other. So, if the batteries aren't giving up current at pretty much equal rates (i.e. internal resistance), and if they aren't charged equally to begin with, then not only will one battery be dumping more Amps when you vape; but it will then proceed to get an uncontrolled [rapid?] charge from the other battery. Or so I figure. One way to monitor what's going on in there (in your mod, while you're vaping in parallel) is: right before you go to pull your batts and charge them, take a good series of toots (draw some current) and then pull them instantly from the mod (separate them). Now check their charge. If they aren't showing the same charge, one battery is being used more heavily than the other while you vape. (this could be due to a physical issue in the mod, or internal resistance of batteries.) I'm given to understand that a couple hundredths of a Volt is not an issue ( ~0.02V-ish).
Now then, also, too, and BUT: I just heard P.Busardo mention in one of his recent videos that he had asked his geeky battery friends about all this, and they told him that battery pairing is not nearly as critical or dangerous an issue with parallel setups as it is with batteries in series. ←that's 3rd hand information. Coming from me, like this, consider it the furthest thing from proven fact. So, I wouldn't hang my hat on it; but it's something I'll be curious to hear more about.
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Pairing of batteries when using them in parallel isn't nearly as important as when using them in series. In fact, if you charge them externally to the mod, pairing them for serial setups isn't hugely important either. But, parallel first....
Assuming that two cells are being fully charged before being put back in the mod, even a 0.1V difference between them only results in, perhaps, a 5A current flow between them as their voltages equalize. Each cell would have at least a 0.01 ohm internal resistance so the total resistance of the battery-to-battery circuit would be 0.02 ohms plus the resistance of the battery mount. So divide the 0.1V difference by 0.02 ohms and you only get 5A flowing between the cells. The current only flows for a very short time too.
The internal resistance of the cells is probably higher than this though so your current is even less. There could be a 0.2V difference between the cells and the current flowing when you put them in your mod would still be less than 10A. Though, I recommend 0.1V max difference just to be perfectly safe with any cell. Even 18350's.
The internal resistance differences between the cells will cause them to output current at slightly different rates. But any voltage differences that start to occur between them is instantly taken care of since the batteries are in parallel. They will always remain balanced no matter how much of a difference there is in their internal resistances.
But, the slight capacity differences of the cells will cause them to reach "empty" at different times. This is only a problem though if you are draining the cells to a very, very low voltage. If you recharge them when they're still above the recommended absolute minimum voltage, 2.5V, you'll never reach the point where one battery has reached zero volts before the other (which is very bad for the cell that has reached zero volts).
So parallel setups pretty well take care of themselves if you charge the batteries to reasonably close voltages. No reason to pair batteries up beyond having them the same model number (e.g., 25R, VTC4, etc.) and roughly the same age.
Series setups....
The internal resistance of the cells won't matter here because the same amount of current will flow through both cells no matter how much of a voltage difference there is. The slight difference in capacities though can cause one battery to reach a lower voltage during discharge before the other. This can be a big problem if you are recharging them inside your mod without a balancing charger board. The difference in voltage will grow larger each time you charge/discharge the batteries until eventually one of them is being charged at way too high a voltage and it vents.
But if you are removing the batteries from your mod each time you charge them then you are effectively "erasing" this voltage difference every time you charge them. You're bringing both back up to the same charged voltage, plus or minus a small difference, so there's no need to worry. You are essentially acting as the battery balancer every time you charge them. While pairing up the same model number batteries is a good idea, same as for parallel setups, you don't need to worry much if you are charging the cells outside the mod.
If you discharge your batteries down to very, very low voltages, less than one volt each, then there could be a problem if one battery was much older than the other. That older battery could reach zero volts before the other and essentially be discharged to a negative voltage...very bad for the battery! But, I think most people would notice that there was a problem with vapor production way before the batteries dropped to less than one volt.
In fact, you don't need to rotate cells for series or parallel operation either. In parallel, the cells automatically balance themselves, and their position in the holders doesn't matter, and in series the charger balances them for you. This is assuming you are charging series setup batteries outside the mod.
So...bottom line...pair the batteries up reasonably well and you're set! No need to worry about matching voltages tightly or rotating cells unless you're using chargers with very different charging voltages.
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This though (parallel battery setups) is all assuming constant connection between battery to battery. + to + and - to - always in contact.Pairing of batteries when using them in parallel isn't nearly as important as when using them in series. In fact, if you charge them externally to the mod, pairing them for serial setups isn't hugely important either. But, parallel first....
Assuming that two cells are being fully charged before being put back in the mod, even a 0.1V difference between them only results in, perhaps, a 5A current flow between them as their voltages equalize. Each cell would have at least a 0.01 ohm internal resistance so the total resistance of the battery-to-battery circuit would be 0.02 ohms plus the resistance of the battery mount. So divide the 0.1V difference by 0.02 ohms and you only get 5A flowing between the cells. The current only flows for a very short time too.
The internal resistance of the cells is probably higher than this though so your current is even less. There could be a 0.2V difference between the cells and the current flowing when you put them in your mod would still be less than 10A. Though, I recommend 0.1V max difference just to be perfectly safe with any cell. Even 18350's.
The internal resistance differences between the cells will cause them to output current at slightly different rates. But any voltage differences that start to occur between them is instantly taken care of since the batteries are in parallel. They will always remain balanced no matter how much of a difference there is in their internal resistances.
But, the slight capacity differences of the cells will cause them to reach "empty" at different times. This is only a problem though if you are draining the cells to a very, very low voltage. If you recharge them when they're still above the recommended absolute minimum voltage, 2.5V, you'll never reach the point where one battery has reached zero volts before the other (which is very bad for the cell that has reached zero volts).
So parallel setups pretty well take care of themselves if you charge the batteries to reasonably close voltages. No reason to pair batteries up beyond having them the same model number (e.g., 25R, VTC4, etc.) and roughly the same age.
Series setups....
The internal resistance of the cells won't matter here because the same amount of current will flow through both cells no matter how much of a voltage difference there is. The slight difference in capacities though can cause one battery to reach a lower voltage during discharge before the other. This can be a big problem if you are recharging them inside your mod without a balancing charger board. The difference in voltage will grow larger each time you charge/discharge the batteries until eventually one of them is being charged at way too high a voltage and it vents.
But if you are removing the batteries from your mod each time you charge them then you are effectively "erasing" this voltage difference every time you charge them. You're bringing both back up to the same charged voltage, plus or minus a small difference, so there's no need to worry. You are essentially acting as the battery balancer every time you charge them. While pairing up the same model number batteries is a good idea, same as for parallel setups, you don't need to worry much if you are charging the cells outside the mod.
If you discharge your batteries down to very, very low voltages, less than one volt each, then there could be a problem if one battery was much older than the other. That older battery could reach zero volts before the other and essentially be discharged to a negative voltage...very bad for the battery! But, I think most people would notice that there was a problem with vapor production way before the batteries dropped to less than one volt.
In fact, you don't need to rotate cells for series or parallel operation either. In parallel, the cells automatically balance themselves, and their position in the holders doesn't matter, and in series the charger balances them for you. This is assuming you are charging series setup batteries outside the mod.
So...bottom line...pair the batteries up reasonably well and you're set! No need to worry about matching voltages tightly or rotating cells unless you're using chargers with very different charging voltages.
If for some reason the mod is designed in such a way that the parallel batts are only in a closed circuit during firing, the batteries COULD just continue to creep further away in their charge state depending on their internal resistance (which will be higher on the more drained battery and inherently higher from any battery further away in a circuit from the load source (say in the case of a positive connection bar where the button could be located between the batts so as to depress them in such a way to purposely deform (flex) the contact to make contact with both batts).
In this scenario, during resting periods the batts will never equalize and special care must be taken to monitor battery state and the batts should be pulled and recharged more often to ensure one doesn't drop too low in voltage unnoticed.
With all kinds of Harry homeowners capable of taking a brick of metal and adding a 7mm threaded hole to call it a mod, I wouldn't be surprised if parallel mods didn't already exist in such a configuration.
Tapatyped
I wouldn't have thought there was a reason to have such a setup until you described them, interesting!
Yes, I agree, charge the batteries outside the mod (and the problem goes away) or keep a close eye on the voltages if the batteries are being charged in the mod.
But, if I understood you correctly, the different internal resistances wouldn't have an effect when the mod wasn't being fired. Without any current flowing there's no voltage drop. It's the different self-discharge ("leakage") rates that cause the imbalance in cell voltages.
I was thinking that the cells would equalize anyway when the mod was fired but those setups you describe would prevent that due to the different path resistances. Probably close to balancing but maybe not if always high current flow. Thanks for mentioning those!
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