Series / Parallel don't matter (dual-batt) in regulated devices (kinda)

[andrew1030]

Just purchased a dual-serial battery device. (150w Vapmod). Before anything, I usually vape within 20-50W, though roughly once a month or so, I do experiment with much thicker gauges or high wattage builds, like twisted, claptons, zippers, etc. That's where the 100W calls for...

I've been having some trouble understanding the significance of a series or parallel type battery connection in regulated devices. I though I had it, but multiple sources from a quick google search got me confused. The statement of 'In series the amps stay the same, that's why its dangerous for high wattages + low subohms', does it apply here for regulated? I don't think so, but I need confirmation... Basically...

Dual parallel (both 20A/4.2V max batts):
4.2V @ 20A + 20A
=4.2V (merged) @ 40A available

Dual serial (both 20A /4.2V max batts):
4.2V + 4.2V @ 20A
=8.4V @ 20A available (merged)

The dual parallel has 40A to negate 'load', by 'increased drain available' (but lower voltage available).
The dual serial has 8.4V to negate 'load' by 'decreased drain needed' (as higher voltage available).
Since it is directly related, we can observe (on dual 20A 4.2v charged):

168W (parallel)
(40A x 4.2V= 168W)
- will pull 20A+20A at 4.2V
- remember it has 40A total so,
- 40A pull /40A avail '100% load'

168W (serial)
(20A x 8.4V =168W)
- will pull 20A at 4.2V+4.2V
- remember it has 20A total so,
- 20A pull /20A avail '100% load'

In both cases, irregardless of atty resistance, the amp & volt draw is directly proportionate & exactly the same (100% of drain capability), after being considered it's entire status in a parallel or serial circumstance.

Hence,
- In parallel APVs, amps available is doubled, along with amps required for a set watt; as voltage is 'halved'.
- In serial APVs, amps available is halved, along with amps required for a set watt; as voltage is 'doubled'.

Due to that relationship, the drain is similar to each other. Drain quantity and usage time on both dual setups will be the same as:

Parallel: 5000mAh @ 3.7v nominal = 18.5W/hr
Serial: 2500mah @ 7.4v nominal = 18.5W/hr
The increase in mAh for parallel is followed suit by an increase of nominal voltage in the serial, hence there is no difference. There is no difference in 'real' (user observed) capacity between both, both have similar 'real' capacity, wattage set being the same... There is only a difference with single cell.
Single cell: 2500mah @ 3.7v nominal = 9.25Wh

Now, it is the set wattage that determines how much to be pulled. It is then the 'independent' side that boosts/bucks to achieve set wattage based on resistance.

Remember that the whole point of the regulation is to remove the atty's resistance from the battery circuit. It is the chip now that is the 'new battery'. This ''new battery'', it's volts and amps are as high/low as it is engineered to be. Wattage is set and locked & it's the manipulation of Volts and Amps to provide that wattage, as RESISTANCE is now involved. Everything here is independent of all the above, except Wattage. Wattage remains the same, but it's a whole different circuit and you can perform NO direct relations or calculations with anything above this part). Basically, everything before this part is merely 'For 168W'. Everything in this isolated part is 'For 168W based on (x)ohms'

(if the chip is capable of doing so):
Eg. 168W @ 0.5ohm = 9.2V / 18A
Eg. 168W @ 0.1ohm = 4.1V / 40A.

That being said, so the real practical advantage to BOTH dual parallel / serial regulated is :
- twice the drain available (one due to increased A; other due to increased V)
- twice the real capacity than a single cell.

The only practical advantage to a parallel: A safer and a more 'balanced' drain?
(not including losses of the circuit)

The only practical advantage to a serial: Ever-ever-ever so slightly better batt endurance?
(some say, buck-only circuits like in serial setups are more efficient, but only by a few % at most

Please discuss or correct me if I am wrong... It's been years from my physics lessons...

*Also, all these assumes that the related circuit will be designed according to the setup (3.7v or 7.4v nominal). Of course you are not gonna chuck 8.4V to a board or chip that can only take 4.5V max.

 

[petrotech]

too deep for me...I normally use single battery mechs and don't sub-ohm very often...but here's a bump, cause I want to learn too!

 

[Mooch]

Basically, you're right.
The primary function of regulation is to compensate for a varying input voltage source, the battery. In VV mode the output voltage is constant and the wattage can change as the coil resistance changes. In VW and TC modes this varying battery voltage compensation still happens but the regulator also performs additional functions. It adjusts the voltage and/or average current to compensate for the coil changes to maintain a certain power level or temperature, along with compensating for dropping battery voltage.

But there are some other advantages between series and parallel...
- Safety, the odds of battery being used improperly are much higher in series if the user doesn't know what they are doing. Full featured regulators (with protection, onboard balancing, etc.) can take some of this risk away but more voltage = greater possible short circuit current at certain points in the circuit.
- Series can be better at getting to certain power levels with higher resistance coils...more voltage to "push".
- Parallel drains the cells identically, leaving them balanced, as long as you don't drain them to the point where their (slightly) different capacities causes one voltage to drop too low. This assumes that the two cells have similar internal resistances, otherwise they will unbalance during discharge and then rebalance immediately after the discharge stops.
- The losses in a buck-boost circuit can add up, versus a buck-only regulator. At 168W a typical well designed buck regulator has roughly a 95% efficiency. This is about 8W lost to heat. A boost regulator can have efficiencies below 90% but let's assume that number. That's almost 17W of heat. The parallel circuit will run hotter and that can affect the leakage rate of any nearby battery and the reliability of the regulator if not properly cooled.

 

[andrew1030]

too deep for me...I normally use single battery mechs and don't sub-ohm very often...but here's a bump, cause I want to learn too!

Basically, you're right.
The primary function of regulation is to compensate for a varying input voltage source, the battery. In VV mode the output voltage is constant and the wattage can change as the coil resistance changes. In VW and TC modes this varying battery voltage compensation still happens but the regulator also performs additional functions. It adjusts the voltage and/or average current to compensate for the coil changes to maintain a certain power level or temperature, along with compensating for dropping battery voltage.

But there are some other advantages between series and parallel...
- Safety, the odds of battery being used improperly are much higher in series if the user doesn't know what they are doing. Full featured regulators (with protection, onboard balancing, etc.) can take some of this risk away but more voltage = greater possible short circuit current at certain points in the circuit.
- Series can be better at getting to certain power levels with higher resistance coils...more voltage to "push".
- Parallel drains the cells identically, leaving them balanced, as long as you don't drain them to the point where their (slightly) different capacities causes one voltage to drop too low. This assumes that the two cells have similar internal resistances, otherwise they will unbalance during discharge and then rebalance immediately after the discharge stops.
- The losses in a buck-boost circuit can add up, versus a buck-only regulator. At 168W a typical well designed buck regulator has roughly a 95% efficiency. This is about 8W lost to heat. A boost regulator can have efficiencies below 90% but let's assume that number. That's almost 17W of heat. The parallel circuit will run hotter and that can affect the leakage rate of any nearby battery and the reliability of the regulator if not properly cooled.

Oh my god re-reading what I typed out earlier, it was extremely redundant at some places. Sorry, it was around 4am here when that post was made? Sorry again.

I seeee... so parallel would be the obvious safer bet, but series has a somewhat negligible gain on efficacy, in regards of hitting that atty up with power. Really interesting! Thanks for the additional info. Exactly what I was looking for

 

[mauricem00]

one point that seems to be ignored here is that batteries have different internal resistance so when used in parallel one battery will but out more current than the other.two 20 amp batteries in parallel can not provide 40 amps safely because of this imbalance. when operated in series this imbalance does not exist so they can provide 20 amps at double the voltage. with series batteries you would have to increase your resistance by a factor of 4 to get full power safely.two 20 amp batteries in series could safely drive a 0.42 ohm coil to 168 watts but the same batteries in parallel could not safely drive a 0.105 ohm coil to the same power level. one battery would provide more than 20 amps while the second battery would provide less than 20 amps due to a higher internal resistance.driving batteries to maximum output with out a good understanding of batteries and basic electronics is almost as safe as giving a loaded pistol to a 4 year old.please take time to educate yourself before attempting this kind of extreme vaping and only use new high quality batteries as internal resistance goes up with age and output capacity goes down. this concludes today's safety sermon hehehhehe

 

[petrotech]

one point that seems to be ignored here is that batteries have different internal resistance so when used in parallel one battery will but out more current than the other.two 20 amp batteries in parallel can not provide 40 amps safely because of this imbalance. when operated in series this imbalance does not exist so they can provide 20 amps at double the voltage. with series batteries you would have to increase your resistance by a factor of 4 to get full power safely.two 20 amp batteries in series could safely drive a 0.42 ohm coil to 168 watts but the same batteries in parallel could not safely drive a 0.105 ohm coil to the same power level. one battery would provide more than 20 amps while the second battery would provide less than 20 amps due to a higher internal resistance.driving batteries to maximum output with out a good understanding of batteries and basic electronics is almost as safe as giving a loaded pistol to a 4 year old.please take time to educate yourself before attempting this kind of extreme vaping and only use new high quality batteries as internal resistance goes up with age and output capacity goes down. this concludes today's safety sermon hehehhehe

and that's why I only use single battery mechs...much easier to understand. lol

 

[Dampmaskin]

- Parallel drains the cells identically, leaving them balanced

For me, this is reason enough to choose parallel batteries as the default configuration for regulated mods.

 

[mauricem00]

For me, this is reason enough to choose parallel batteries as the default configuration for regulated mods.

voltage remains balanced but current does not. the model airplane community has several years of experience operating lithium batteries at very high discharge rates and I have seen battery fires resulting from misuse. my training is in the area of electrical engineering.series batteries and higher resistance coils would be a safer more efficient way of getting maximum power to your coils.electronics can short and the mods currently available have minimum cooling for the power structure which increases the chance of shorting out. this risk increases at higher currents.

 

[Mooch]

one point that seems to be ignored here is that batteries have different internal resistance so when used in parallel one battery will but out more current than the other.two 20 amp batteries in parallel can not provide 40 amps safely because of this imbalance. when operated in series this imbalance does not exist so they can provide 20 amps at double the voltage. with series batteries you would have to increase your resistance by a factor of 4 to get full power safely.two 20 amp batteries in series could safely drive a 0.42 ohm coil to 168 watts but the same batteries in parallel could not safely drive a 0.105 ohm coil to the same power level. one battery would provide more than 20 amps while the second battery would provide less than 20 amps due to a higher internal resistance.driving batteries to maximum output with out a good understanding of batteries and basic electronics is almost as safe as giving a loaded pistol to a 4 year old.please take time to educate yourself before attempting this kind of extreme vaping and only use new high quality batteries as internal resistance goes up with age and output capacity goes down. this concludes today's safety sermon hehehhehe

I mentioned internal resistance in my previous point but for my example I assumed that the resistances were the same. You bring up some very good points! Safety, safety, safety!

 

[Mooch]

voltage remains balanced but current does not. the model airplane community has several years of experience operating lithium batteries at very high discharge rates and I have seen battery fires resulting from misuse. my training is in the area of electrical engineering.series batteries and higher resistance coils would be a safer more efficient way of getting maximum power to your coils.electronics can short and the mods currently available have minimum cooling for the power structure which increases the chance of shorting out. this risk increases at higher currents.

One of the big concerns though is that a series setup in a mod will not have balancing or low voltage cutoff for the cells, possibly leading to polarity reversal or an overvoltage situation in a cell (during charging) over time. Some more...umm..."adventurous" users will set up a series config but with low resistance coils, significantly exceeding the CDR for the cells. Using a parallel setup can help reduce some of the problems that could possibly occur when there's misuse/abuse.

You're right though, series is more efficient and I would love to see it used more. The potential for abuse is higher and that makes it tough to recommend.

 

[andrew1030]

one point that seems to be ignored here is that batteries have different internal resistance so when used in parallel one battery will but out more current than the other.two 20 amp batteries in parallel can not provide 40 amps safely because of this imbalance. when operated in series this imbalance does not exist so they can provide 20 amps at double the voltage. with series batteries you would have to increase your resistance by a factor of 4 to get full power safely.two 20 amp batteries in series could safely drive a 0.42 ohm coil to 168 watts but the same batteries in parallel could not safely drive a 0.105 ohm coil to the same power level. one battery would provide more than 20 amps while the second battery would provide less than 20 amps due to a higher internal resistance.driving batteries to maximum output with out a good understanding of batteries and basic electronics is almost as safe as giving a loaded pistol to a 4 year old.please take time to educate yourself before attempting this kind of extreme vaping and only use new high quality batteries as internal resistance goes up with age and output capacity goes down. this concludes today's safety sermon hehehhehe

voltage remains balanced but current does not. the model airplane community has several years of experience operating lithium batteries at very high discharge rates and I have seen battery fires resulting from misuse. my training is in the area of electrical engineering.series batteries and higher resistance coils would be a safer more efficient way of getting maximum power to your coils.electronics can short and the mods currently available have minimum cooling for the power structure which increases the chance of shorting out. this risk increases at higher currents.

So, a dual 20A constant discharge battery-fully charged-on a regulated, in theory would be at 100% drain at 168W. Which i think is why most dual batts top out at 150W (hahaha right at the edge aint it?). But since regulation kinda removes the coil resistance from the battery to the chip, does resistance still play a role?

Serial:
150W = 7.4v (dual nominal) x 20.3A (this is the actual drain on the batt, correct? or is it the 22.4A below?)
150W @ 0.3ohms = 6.7v x 22.4A (ohms law; i'm pretty sure every 150w chip out there can do this, but is 20.3A or 22.4A the real drain on the batt)

Parallel:
150W = 3.7v (dual nominal) x 40.5A
150W @ 0.3ohms = 6.7v x 22.4A ... similarly, which is the actual theoretical drain on the batt? 40A or 22A?

Thanks for the info too, so is it correct that:
In parallel - Current imbalance during loading ; voltage balanced during load? But-Overall drain balanced after loading?
In series - No current imbalance during loading ; voltage imbalance during load? Overall drain imbalance after loading?
Is the above correct?

Cause the word out there (Reddit/other forums) is, series - 'cell in front' drains more. Parallel - 'identical drain'. I have no idea what that means.

I'm not trying to do a crazy build here but i'm extremely curious about how the battery performs in different setups in a regulated. Just to make sure that no one is cutting corners unreasonably when it comes to safety on relatively new tech (at least not on the stuff i have in hand), also to make sure I have a good buffer if i ever attempt something rather mad.

One of the big concerns though is that a series setup in a mod will not have balancing or low voltage cutoff for the cells, possibly leading to polarity reversal or an overvoltage situation in a cell (during charging) over time. Some more...umm..."adventurous" users will set up a series config but with low resistance coils, significantly exceeding the CDR for the cells. Using a parallel setup can help reduce some of the problems that could possibly occur when there's misuse/abuse.

You're right though, series is more efficient and I would love to see it used more. The potential for abuse is higher and that makes it tough to recommend.

In that case for a regulated mod in series, unless the charging system is spectacular, it's always safer to charge the battery on an external? As unless the cells are monitored individually, a theoretical drained situation of 2.0v+3.0v may occour (5v cutoff)? Also, a 4.1v + 4.3v (8.4v fully charged) may occour?
----
Please do correct me if i'm wrong anywhere

 

[opticruby]

I'm reading and learning

 

[Mooch]

Cause the word out there (Reddit/other forums) is, series - 'cell in front' drains more. Parallel - 'identical drain'. I have no idea what that means.

"Cell in front drains more"...this is utterly and completely impossible. Cells in series, by definition, supply the exact same current. They could be referring to the fact that one cell will always have a lower starting capacity and/or higher internal resistance, but even that has no relationship to the cell's location in a string.

If one cell always gets heated more than the other by a warm atty, or some other external heat source (MOSFET?), then there is the potential that the cell leakage could increase and cause that cell's voltage to drop over a long period. But I can't see that having a noticeable effect.

There is a vague report of someone always seeing their "top" cell being at a higher voltage when removed for charging but there are so many unknowns here that we really can't draw any conclusions.

 

[NOVA jon]

I'm reading and learning

Yup.......
(Pulls up a chair next to opti.....)

 

[mauricem00]

One of the big concerns though is that a series setup in a mod will not have balancing or low voltage cutoff for the cells, possibly leading to polarity reversal or an overvoltage situation in a cell (during charging) over time. Some more...umm..."adventurous" users will set up a series config but with low resistance coils, significantly exceeding the CDR for the cells. Using a parallel setup can help reduce some of the problems that could possibly occur when there's misuse/abuse.

You're right though, series is more efficient and I would love to see it used more. The potential for abuse is higher and that makes it tough to recommend.

I do not sub ohm. I use a single cell mechanical mod with coils between 1.5 and 2 ohms but I find that vapor output drops so much at lower cell voltages that one would change batteries long before reaching the deep discharge level that would cause cell reversal. I change batteries when they get down to 3,6 volts because vapor production gets too low.this is pretty common practice and for safety any battery operated circuit should have a low voltage cut off. I did take a battery down to 2.5 volts once with a dummy load and when recharged it did accept the rated capacity but in vaping performance drops too much if taken down below 40% charge.as I said before anyone interested in deep sub-ohming needs to educate themselves first or at least make sure their live insurance policy is payed up and covers vaping related accidents LMAO. we can't stop some people from competing for the Darwin award but we need to try to keep this as safe as possible. balance chargers are available inexpensively for model airplane batteries and they work great for vaping batteries as well and give an extra margin of safety. I use one myself and found some of the cheap chargers sold for vaping do tend to charge to too high a voltage and provide no monitoring of charge voltage and current. bottom line if you don't know what you are doing then don't do it.

 

[mauricem00]

So, a dual 20A constant discharge battery-fully charged-on a regulated, in theory would be at 100% drain at 168W. Which i think is why most dual batts top out at 150W (hahaha right at the edge aint it?). But since regulation kinda removes the coil resistance from the battery to the chip, does resistance still play a role?

Serial:
150W = 7.4v (dual nominal) x 20.3A (this is the actual drain on the batt, correct? or is it the 22.4A below?)
150W @ 0.3ohms = 6.7v x 22.4A (ohms law; i'm pretty sure every 150w chip out there can do this, but is 20.3A or 22.4A the real drain on the batt)

Parallel:
150W = 3.7v (dual nominal) x 40.5A
150W @ 0.3ohms = 6.7v x 22.4A ... similarly, which is the actual theoretical drain on the batt? 40A or 22A?

Thanks for the info too, so is it correct that:
In parallel - Current imbalance during loading ; voltage balanced during load? But-Overall drain balanced after loading?
In series - No current imbalance during loading ; voltage imbalance during load? Overall drain imbalance after loading?
Is the above correct?

Cause the word out there (Reddit/other forums) is, series - 'cell in front' drains more. Parallel - 'identical drain'. I have no idea what that means.

I'm not trying to do a crazy build here but i'm extremely curious about how the battery performs in different setups in a regulated. Just to make sure that no one is cutting corners unreasonably when it comes to safety on relatively new tech (at least not on the stuff i have in hand), also to make sure I have a good buffer if i ever attempt something rather mad.



In that case for a regulated mod in series, unless the charging system is spectacular, it's always safer to charge the battery on an external? As unless the cells are monitored individually, a theoretical drained situation of 2.0v+3.0v may occour (5v cutoff)? Also, a 4.1v + 4.3v (8.4v fully charged) may occour?
----
Please do correct me if i'm wrong anywhere

regulation does not remove the coil resistance from the battery it adds a variable resistance in series with the coil to keep coil voltage constant.most regulated mods are PWM with or without an output filter so the peak current from the battery would be much higher but the average current can be determined by P=R times I squared where P= power R= coil resistance and I = current. it is always safest to charge batteries individually and not in parallel like some chargers do.do not put your safety in the hands of MOD makers. there is a lot of junk being sold to the vaping community. you alone are responsible for your safety and the safety of others around you when you vape.you could build a battery box for charging multiple cells with a balanced charger but this is probably beyond the skills of most vapors.best stick with good quality single cell chargers and charge batteries one at a time