What are milliamp hours?

[@OrbitalSP2]

we should be using watthours because Wh also accounts for the voltage. So, a 4Ah cell can have much higher energy stored compared to another 4Ah cell, because one might be 4Ah AT 1.2V and the other 4Ah AT 11.5V. By using Wh this problem is eliminated since Wh is Ah multiplied by voltage. I hope I'm right. I researched this a few months ago. Amps times volts is watt . Ah times volts is Wh, right?

[@JulianIlett]

+OrbitalSP2 Spot on :)

[@midwinter78]

+OrbitalSP2 One minor issue - the voltage of a battery isn't completely stable over time, it goes down gradually as it gets discharged, quicker and quicker as it reaches the end of its life. So the battery life in mAh multiplied by the nominal voltage V might not be exactly the same as the the actual number of Watt hours (1 Wh = 3600 J of course) you can get out of it. Furthermore it seems that the actual voltage varies depends on how quickly you discharge the battery, so you get fewer watts per amp hour with a quick discharge than with a slow discharge. Google for "discharge curves" - it seems that the number of mAh you can get out of a battery doesn't depend too much on the discharge rate, whereas the area under the discharge curve does. Hence, I suppose, quoting mAh rather than Wh - it's a more dependable quantity.

[@linksmith1057]

To some degree yes, but electronics are voltage sensitive. A 1Wh battery that spits out 3.7 Volt could nuke electronics while a 1Wh battery that has 1.2 Volts may work perfectly fine. The time Wh is useful is when working with systems that alter voltage. So a system that converts volts from say 12 to 36, just dividing amps no longer will give you a valid run time estimate. Converting to Wh can effectively keep Apples to Apples. But in systems where the voltage is kept the same, one can (assuming C rates are within the batteries capabilities to provide) give a fairly accurate estimate of runtime just by dividing the current draw of the device by the Ah capacity of the battery. A C rate is a given amount of a batteries power it can effectively discharge in 1 hour. So a battery rated at 0.5 C will give its capacity in Ah based on this figure. If discharged faster then 0.5 C, you will get less capacity out of that same battery then it's rated Ah.

[@Matlalcueitl]

+OrbitalSP2 I guess they use mAh instead of mWh because larger values sells better. :>

[@Designandrew]

+OrbitalSP2 dell rates their laptop batteries in watt hours

[@marco_evertus]

If you put them in series the voltage increases not the charge capacity. (right?)

[@EngineeringNibbles]

yes

[@emilen2]

Yes, but the Wh doubles.

[@danieltabrizian]

+Rounak Dutta The charge capacity is never affected, the higher voltage usually uses less current in a circuit which is able to take both voltages and thus capacity remains the same no matter if you put it in series or put it in parellel

[@marco_evertus]

daniel tabrizian yeah I know, even tho I am not an electronics guy (I am a software dev) I do know the basics of electronics

[@linksmith1057]

The charge capacity I think is an inaccurate term. Series or parallel, the amount of "energy" (usually expressed in Watt Hours or Wh) remains the same, but voltage increases. Two 3 volt cells with 1000 mah of capacity in series will provide 6 volts (think of volts as electric pressure, some Chinese manuals actually call it pressure instead of volts) but still remain at 1000 mah. Wired in parallel, the batteries will now only provide 3 volts but have 2000 mah of capacity. In either configuration you still have volts times amps equals watts, so it's still 6 watt hours of power.

[@fredbloggs5822]

Watt hours is a much better way of measuring the capacity - that way it doesnt matter if you put them in series or parallel, the Wh stays the same.

[@TheInfoworks]

Amp hours remains the same, but the volts are the sum of the number of cells, hence the watts increase with each addition cell in series.

[@linksmith1057]

Watts also increases with cells in parallel. Voltage doubles with each new cell in series but mah remain the same. Volts times amps equals watts. Any configuration of the same three batteries will always have the same total Watt Hours, but you can get that same rating by tripling voltage or tripling amperage.

[@jrneulight]

What is the mat that you record on(link)?

[@petesclark]

At the 7:50 mark near the end you show one of your power banks. I remember that one of the cells was put in backwards and it fried the spring contact. I accidently put one of my cells in backwards and fried the spring too. The heat took the spring out of the spring and it wouldn't hold a cell in place. I used a pair of needle nose pliers and stretched the spring back out. Now it works again. Good luck.

[@SteveHodge]

Lots of people saying we should use watthours, and there are good arguments for it. But as Julian said, the reason we use Ah instead of Coulombs is because it allows easy reckoning of (dis)charge times. That advantage doesn't apply to Wh because we'd also have to divide by the voltage (which may not be constant). So if we're going to throw out Ah in favour of Wh then we should just go the whole way and use Joules.

[@MrJason005]

3:14 Who doesn't love physics? Also, at 6:42 how come you didn't tell a bit about integration?

[@JulianIlett]

+MrJason005 I wanted to keep it simple. But I'm planning a video on charging a lithium cell. During the CC phase, area under the current curve is a simple rectangle, but during CV it's more complex and requires integration.

[@kuhrd]

When the cells are in series you see an increase in the total voltage by adding the cells voltages together but the Ah value will be the same as the cell with with the lowest capacity and highest internal resistance. Generally you want to used matched cells in series to ensure all the cells discharge at an equal rate.

[@cultistaautista]

Yes that is correct, but the voltage that each element is rated at and able to output at still exists as a parameter that defines their ability to store energy, that is absolute capacity. So both the cells and arrays of them are still going to have different capacities depending on what voltage they are rated at and are able to output optimally, even if they have the same charge capacity. Because a charge, while existing, still needs the potential to perform work, that being the electromotive force.

[@halfalogue]

I was actually just chargin all my 18650s and thinking to myself the hell is a mAh? Great vid, perfect timing for me!

[@johncherry108]

Julian, it's a rule with SI units that if they're named after a person, the unit is capitalised. Hence 'C' for Charles-Augustin de Coulomb or 'S' for Ernst Werner von Siemens, but 's' for second.

[@JulianIlett]

+John Cherry OK, I'll remember that :)

[@kimt6333]

..And abbreviations are capitalised if they are multiplied and not for divisions ie. Kilo, Giga, milli and pico. Sorry for my English it's not my native language.

[@tobortine]

It will be a capital "C" because it describes a person, Charles-Augustin de Coulomb. It's always a capital when it is named after someone as in Hertz, Amperes and Volts. Where I always get confused is with the multiplied prefixes because usually greater than 1 is capital as in mega (M) and below 1 is lower case as in milli (m) but that fails with kilo. eg mA MW kV

[@ctrlthecontroller]

Is it safe to wire 8 Li-ions in series and what is the safe discharge rate? Is 1C okay?

[@FlyingShotsman]

Yes, ~30 volts is perfectly safe. Just don't short an 8S pack or you'll have a potentially violent release of energy. Safe discharge rate depends on the ratings of the cells used. See the datasheet. Like capacity, discharge rate multiplies with cells in parallel but not in series, so an 8S pack should not be discharged at a rate higher than any single cell's rating. Also, unless you use a balance charger, do not charge eight cells in series.

[@ctrlthecontroller]

+FlyingShotsman Okay thx, I'll charge them independently.

[@90msg90]

I must challenge the use of ampere-hour unit as a term describing 'capacity'. For me "capacity" means that battery holds some specific, measurable property that I can use to power up a device and since it's put into a number it must mean, that two batteries with the same "Ah" value will be capable of powering devices and putting out the same energy. As all the viewers probably know, that is not true, because the voltage here is also very relevant. You can't do the same with 50 Ah powerbank as you would with 50 Ah car battery, because the first one has cells that produce only 3,7 V, and the car battery is usually producing 12V. So for me the actual capacity is described by watt-hours, rather than amp-hours. It is THAT unit that tells the real possibilities of the power source, where the Ah is only useful, when comparing two sources working on the same voltage (USB powerbanks compared to USB powerbanks, cell phone batteries compared to each other etc.). I would be very curious on how to differenciate those two terms in practice - let's stay at Ah describing "capacity", but how do you call the parameter of the battery described in Wh then? By putting the cells in series you increase the voltage, but according the the theorem "amphours describe the capacity of the battery", you didn't actually increase capacity by one bit - 3Ah cells in series is still 3Ah, with different voltage. But you still used 3x more cells to build a power source, so clearly Ah is not the way to describe possibilities of a battery. Let me give you an example of what I am on about. I have a powerbank, that has an information that it has 16 000 mAh of capacity. I also have a notebook, that has 4 000 mAh battery. So (excluding the power loss of PB booster to make things easier to calculate), you would say, that I can charge my laptop 4 times with that powerbank. And most people buying powerbanks think like that, unfortunately. In practice it turns out that the PB can charge the notebook only once and after that is fully empty. The reason behind this is that the PB has 3.7V cell and the battery is rated at 11.4V, which makes 3x difference in the Amphour area, but Watthours are basically the same... Add the powerloss on the 3.7 >> 19V conversion at the powerbank and then from 19V to 11.4V in the laptop and the result is simply sad. But scientific. In my world "capacity" is the amount of energy stored in battery, therefore the actual capacity is described in Wh, not Ah.

[@Tjofrasen]

+90msg90 I could not agree more. Everything would be so much easier if we just used watthours. Technically i think that mAh is the measure of electric charge and Wh is the measure of the energy. So i would call mAh 'current capacity' and Wh 'energy capacity'. But that is still confusing :)

[@90msg90]

+Tjofrasen Yes, I just resent to use "capacity" and Ah together. That is more "current CAPABILITY" and then Wh is "energy capacity", but that's like saying "a waterbottle to hold water", so for me "capacity" would be enough.

[@TheChipmunk2008]

Current capability is measured in Amperes. Not amp hours.

[@taffythegreat1986]

Hi there I have a led flood light. The in put us 220v The transformer burnt out. It was 24v output with 900 ma+5% If I replace this with another transformer of 25v with a 250ma + 5%. Would this still be ok.

[@Amiro1990]

Hey Julian, Iv got a mystery about my Samsung Note 4 battery . I'm trying to understand what are the cause for it. my phone got dried to 6% so I plugged in the charger then it dropped to 3% so what I did is turn off my phone and took my multimeter and measure the voltage and I got read of 3.68v and on the battery says she's 3.85v/ 3225mah and while charging 4.4v does my battery broken or discharging herself all the time? please help me to understand the problem here.. Appricate.

[@iamdarkyoshi]

Well, the answer is watt-hours, a unit containing voltage, current, and time. Because there are three cells in series, the voltage is tripled, tripling the watt-hour rating.

[@kofix]

Maybe someone already mentioned this, but the apparent capacity depends on the discharge current - the internal resistance which changes with temperature and charge etc .. Most battery sellers actually post discharge curves in their datasheets. I was once surprised that my 12AH lead acid battery wasn't able to supply 12A for an hour but for less than 2/3 only.I think it could be a good idea for a next vid :)

[@rudytorres6559]

FINALLY!!!!! The best explanation I've ever heard. Now I get it. Thank you Julian

[@gamerpaddy]

short: 1 Ah = 1000mAh 1A = 1000mA 1 W = 1000mW V = (Cells in series x Cell Voltage) Ah = (Cells in paralell x Cell Capacity in Ah) Wh = V x Ah W = V x A 1Ah can deliver 1A for 1 hour 1Wh can deliver 1W for 1 hour example. 2s2p (3.8V 2.6Ah each cell) = 2 series 2 paralell = 7.6V 5.2Ah = 39.52Wh = can deliver 13.17W for 3 hours.

[@twirlywhirly555]

Series the capacity stays the same , voltage rating goes up and the Watts/h goes up aswell ( though in parallel the Watts/h goes up too )

[@JulianIlett]

+TwirlyWhirly555 Correct, but be careful not to write Watt hours (Wh) as Watts per hour (W/h)

[@MitzpatrickFitzsimmons]

Great video! Question... you suggested that some cells are not legit... how does one discern real from fake when buying from ebay? I bought 16 Ultrafire 18650 cells from ebay at what I thought was a reasonable price... they say they are 9800 mAh @ 3.7v... which if true would equate to 36.26 watt hours I believe. I have wired 2 of these cells in series to power 3 10 watt LEDs which are not at full brightness (in fact I am not even using a heat sink), but have been lit for over 1 week 24/7.

[@FlyingShotsman]

Wow, that's the most astonishing capacity claim I've ever seen. It's a load of crap, unfortunately. You'll be lucky if they're 1,000mAh each. Without knowing the current drawn by your LED circuit, run time is meaningless. Generally, genuine Panasonic or Samsung cells (speaking of 18650s here) are very plain in appearance with solid color wrappers and simple dot matrix part numbers and capacities printed on them. Also, they're always protected cells; those manufacturers do not sell unprotected cells to the retail market. If the cell you're looking at has a flashy label with a name that contains "fire," run away. As Julian mentioned, other reputable sellers do repackage Panasonic and Samsung cells. Flashlight vendors Thrunite and SureFire (one exception to the "fire" rule) are two examples, but you'll pay a name brand premium. As Julian also mentioned, the max capacity in 18650s with today's technology is about 3,400mAh. For the best currently available 18650 cells, look for the Panasonic NCR18650B. They're available on eBay; expect to pay $7-10/cell in small quantities.

[@MitzpatrickFitzsimmons]

+FlyingShotsman Thanks for the reply & info. My cells are solid color (yellow)... not sure if that means anything, and I do plan to redo my test on the 3 LEDs with a meter to get some type of idea what current draw they are getting. They were very dim from the get-go... seemed like there was barely just enough power to light them up, but I thought after a day they would have gone dark... it was interesting to me though that they lasted over a week in that condition from just 2 cells.

[@rstevewarmorycom]

So would you like it in Coulombs, Julian, or maybe in electrons!

[@7t3chguy]

Stays the same - amount of charge capacity would remain unchanged, just the potential of that charge would increase.

[@1bigsyd]

Julian can you explain in real world then if you had a drill made for 4.2v with a one 3ah battery over a drill at 18v also with a 3ah battery what would be the benefits

[@vgamesx1]

+1bigsyd Well assuming it's more or less the same drill, if you used a pack all in parallel then it wouldn't work, not enough voltage to turn the motor or at least not very quickly, so you would need a powerful boost converter to raise the voltage up to about 18v but that would be rather inefficient and bulky, for simplicity lets say that drill draws 1A just to run, so no stress on the motor, 18V x 1A = 18W alright then to get 18W you need to take the nominal voltage of the battery as that 4.2V will drop quickly to 3.7V (a bit more under load) x ____A = 18W (so 18/3.7) means the boost converter needs 4.9A in order to provide 1A at 18V but hold on, because dc converters aren't 100% efficient (closer to 70-80%) and some of that will be lost as heat, so actually, you need about 6.7A (about 75% efficiency) not accounting for any stress put on the motor, in which case that could end up drawing well over 10A through boost converter, which also means you're going to have a lot of heat to dissipate, so basically... That would be highly impractical because in order to fit that kind of boost converter in with the batteries you would need a larger battery case and still probably couldn't fit as many batteries inside, the only benefit that would provide in a drill would be a simpler charging circuit. While the 18V pack it can just run directly off the batteries, much simpler and you don't waste any power.

[@michaeltempsch5282]

+1bigsyd Not Julian, but - The 18V battery holds ~4,25 times more total energy, 4.2*3 =12.6Wh vs. 18*3=54Wh . Typically this is used to deliver more power in the tool (for a more powerful/useful tool), in the form of higher rpms and higher torque. But it could in theory be used to deliver the same power as the 4.2V version, but would then last longer since it would draw less current out of the battery for the same power (Power=Voltage*Current). The same extension of operation time could be achieved by adding the extra cells the 18V version has in series, in parallel instead, for the same total energy. Higher voltage for the same power means lower current, so thinner wires and smaller/cheaper power control components can be used.. True to a point, crank up the voltage really high and insulation issues pop up and components again start to get bigger to be able to handle the voltage

[@TheScapeMine]

At the end I missed you talking about watt hours :(, still great video ! It's nice to rethink my knowledge about capacity ! :D

[@newzealandgold4734]

Correct me if I'm wrong but there is no such thing as ampere hours it's correctly pronounced ampere hour, there is no S on the end of hours.

[@Barrybados]

You learn something new every day and i do when i watch your videos nice one .

[@multifrag]

That is why you calculate the capacity in Wh|(watt-hour). Difference in voltage from 1.2V to 18V. Some powerbanks will use the mah reading at 3.7V, but the phones we charge work at 5V. So just by using Wh you can see you've been mugged of 26% capacity.

[@Bob_Burton]

I do not understand the confusion about milliamp hours. To me it has always been quite evident that (in a mythical perfect world) a battery could provide a certain number of milliamps for a certain time and that increasing one caused the other one to reduce. The maths is simple, but introducing other measures such as watt hours just complicates things. Say you need a 12 volt battery to deliver 2 amps for 3 hours it is obvious that you need a 12 volt battery rated at 6 amp hours. Simple.

[@TheChipmunk2008]

+UKHeliBob indeed, incredibly simple, I too have never understood the confusion. The use of milliamp hours messes with my head a little though, you see people saying '2000 mAh', just say 2 Ah :)

[@MrOpenGL]

+TheChipmunk2008 Because saying "Yeah my powerbank has 10000 mAh" is better* than saying "my powerbank has 10 Ah of capacity"

[@MrOpenGL]

+UKHeliBob I agree, but how many times have we seen people saying "It's a 2500 mAh charger" (or even worse, this battery has 2500mA (or even MA which is Mega-ampere!!!))???

[@raykent3211]

I agree, for a person dealing directly with a cell or battery. But a recent issue is with usb power banks. They quote mAh for the "internals", not for the 5V that the user gets. Pretend there's a 1V cell in there rated at 10Ah. Now boost the output to 5V and the user only gets 2 Ah at that voltage.

[@michaelkaliski7651]

Chinese manufacturers seem to reference their battery capacities to 1 volt. So a cell that can supply 800 mAh at 1 volt is considered to be a 3000 mAh battery when putting out 3.7 volts. It seems that a deliberate error in multiplying up units is exploited to confuse the power capacity printed on the sleeve. The only possible solution I have been able to come up with to explain the grossly inaccurate labelling of cells.

[@p1nesap]

Good clarification that mAh ≠ current; 3000 mAh won't blow IC/LED circuits. I think of greater mAh = longer run time.

[@pedromms8908]

+p1nesap 3000mAh won't blow anything. And 3000mA also won't blow anything if you know how to use it. If you use a, for example, 5V 3A power source you can connect LEDs to it and don't blow them. You just need to use the proper current limiting resistor in one of the LED leads. But yes, you're thinking right: "greater mAh = longer run time"

[@TheChipmunk2008]

"how can that be'. Because the voltage is different. You KNOW that

[@DiyintheGhetto]

Awesome video Julian well done man. I learned a lot :)

[@electrodacus]

I wanted for some time to make a video about the difference between power and energy. This is what people confuse the most and it makes no sense since people should understand the definition of this two words. Power and energy has the same meaning in any context. Is strange that most people understand this words in most contexts but when it comes to electricity people get confused even if there is no reason to be confused. Power is measured in W and energy in Wh. One analogy will be a fossil fuel car. Energy in this case is contained in the fuel tank where you have a certain volume of fuel usually gasoline and each liter of gasoline contains about 10kWh of energy. Then you have the engine that has a power rating usually in horse power [HP] (a bit outdated) or Watt [W]. If the engine will be 100% efficient it will convert all that energy in to power so for each liter of gasoline 10kWh you will produce 10kW of power for one hour or 20kW for half an hour or any other combination. Of course a gasoline engine is not 100% efficient in converting energy to motion (maybe 30% at best) the rest of 70% will still be converted but to a less useful heat. People usually understand the difference when you say they have a lot of power or some other person is powerful and a person that has a lot of energy. A physically powerful person may be able to lift a basket with 5 big 10kg melons siting on the ground on to a 1 meter tall table and will use an X amount of energy. While a much weaker person will be able to only lift one melon at a time so 5 times 10kg lifted on the same 1m tall table while using about the same X amount of energy. So the words power and energy will have the same meaning in any context. When you say you have a powerful battery is not the same with saying you have a battery with a lot of energy.

[@ww321]

In China mAh is the same thing that fairies and gnomes are made from.

[@dorfschmidt4833]

+ww321 Remember PMPO ratings ? :D

[@TheChipmunk2008]

+Dorf Schmidt Sadly, yes.

[@ww321]

+Dorf Schmidt Peak Music Power Output?

[@dorfschmidt4833]

ww321 Yep. Scam.

[@TinkerbatTech]

+Dorf Schmidt PMPO. The amount of instantaneous power developed when you hooked the power supply leads of the (120V nominal) amplifier to 480V, and fed 240V into the line input. I remember a component stereo rated at 80W PMPO that had a 12V 1A power transformer (Probably that big to run the 8-track deck) and 2SB77s as push-pull outputs capacitively coupled. One of the early PMPO examples. Chinese lithiums are cut from the same math....

[@grigor_karagozian8219]

Using the ohms law triangle could I calculate it please show me how?!

[@sylvainlazare1114]

The energy released out of the battery increases with its tension. Therefore it is correct that capacity*tension=energy (in Wh). Now concerning Li-Ion batteries due to protection voltages max 4.2 V and min 2.7 V the useful capacity should be less than the rated one. Or not? what do you think?

[@79cocosel]

one small battery have 3amp?

[@Aceman307]

Very well explained. Thanks

[@MarkHeywood2012]

I guess while batteries connected in parallel multiplies the capacity, batteries connected in series multiplies the voltage where the capacity remains the same; in keeping the calculations consistent with Ohms Law.

[@stuartgoggin4267]

It would be interesting to plot Power (Watts) over time that cell given a static constant resistive load. (Because the voltage will vary over that discharge right?) So the meaningful work a cell will perform isn't really 3000maH * 4.2v = 12.6Wh, because the voltage will be non constant... However the wH capacity of the cell is going to vary heavily based on the discharge current, with the cell being least efficient at higher discharge currents. So I guess you would end up with multiple wH capacity curves.

[@michaeltempsch5282]

+Stuart Goggin True. Mostly the manufacturers don't provide constant [resistive] load curves, but typically voltage plotted over time for various constant current levels, often given as multiples/fractions of 'C', where 1C is the capacity in (m)Ah divided by 1h, ie 1C would be 3A for a 3000 mAh cell, 0.1C would be 300mA and 2C would be 6A. A power plot would look similar,(start high, drop a bit fairly quickly 'level off' and drop much more slowly for most of the run. and then drop sharply at the end) but even more 'extreme' compared to the voltage/time for constant current, www.ibt-power.com/Battery_packs/Li_Ion/Li_Ion_DiscGph.JPG, since as the voltage drops, so drops the current, and power is the product of the two. For the real capacity you would need to calculate the integral of the curve.- the 'rectangular approximation' of constant voltage, and constant current for capacity/current time is just that a [quite rough] approximation

[@TechGorilla1987]

So there are a bunch of coolies stuffed in my batteries to do all the work? Wait, never mind. :D That's a terrible joke.

[@zaprodk]

Watthours is the best term in my world

+zaprodk I agree with you. In my opinion that's why capacities of batteries, powerbanks, etc. should be measured with Wh or mWh. :)

[@renxula]

+zaprodk Watt-hours are great since they are a direct measure of energy, so different battery chemistries and voltages can be compared. However, amp-hours are still useful when a circuit doesn't have a switching regulator, because then only current matters. Like when running a microcontroller from a single lithium cell; it can even be more energy-efficient to use a linear regulator than a switching regulator.

[@whitefields5595]

...... and to be complete the voltage across the battery terminals measures the POTENTIAL to do work (that is why it is called a 'potential difference'). In this case the battery is claimed by the manufacturers to potentially (possibly?) release 3000mAh of stored energy. How, and if, it does it depends on the load it is connected to. As you say if it is a low resistance the current will be high and some energy will be released as heat.

[@whitefields5595]

Julian, No explanation of this subject is complete without mentioning ENERGY. In an electrical system the work is done by the current (Amps) which is pushed through the circuit by the difference in potential (Volts) across the load. You are correct in mentioning the area under the Ah curve but this is electrical energy, not electrical charge. This stored energy is a measure of the battery to do work.

[@Unordung]

KVL = sum of voltages in equals sum of voltages out KCL = Sum of current in equals sum of current out. The principle of conservation of electric charge says that the voltage would equal the sum of all voltages Vt=V1+V2+V3, however due to the internal resistance of the battery current will not.

[@pmkwiek]

so it stays at 3000mah but voltage goes up to 11.1v nominal

[@ChrisFredriksson]

You made me.. more confused... Even though some things was confirmed - some things I did know.. Hmm I hope to see a followup video =) Not sure about what, but you probably already have an idea =D Just an example.. I just finished the other day a mod on four garden lights, I basically rewired them from solar powered to a single external battery pack of 4 AA cells in series, giving me 6V and what I believe is 2000mAh. As when you wire them in series you add the voltage, opposed to wire in parallell where you add the mAh rating.. Correct? Anyhow, with my four lamps drawing a total of 60mA, shouldn't they drain the batteries in 2000/60 = ~33 hours? This however, as you made me aware of, are two different units.. mAh / mA ... Which could be very wrong now when I think about it.. So how is it actually? I'm very confused now! =D Also, the four lights has not drained the batteries with around 10-12 hours runtime per day for over 4 days now.. They are still lit very bright and nicely.. So.. I'm confused! =D But happy that they are still on ;) hehe

[@pfeerick]

The general rules are (avoiding for the moment variances in voltage and capacity): When you put batteries in parallel, the voltage stays the same and the capacity increases. When you put them in series, the voltage increases, and the capacity remains the same. The amount of energy that both methods can provide is the same, it's just how the energy can be accessed. If you want to increase the run time of something, you either increase the voltage, or increase the capacity. If it doesn't like a higher voltage you add more batteries in parallel. If you can increase the voltage, you generally do, as it lease to less work being dong, and higher efficiencies.

[@donaldfilbert4832]

I believe that the mAh would triple in the case of 3 cells in a series connection just as they did in a parallel connection. As mAh is a measure of "charge" (coulombs) in the cells - 3 cells will have 3 times the charge regardless of how you hook them up. Of course - the performance of the circuits would be totally different. If you put the series battery pack in the same circuit (same resistance) as a parallel battery pack - it will present 3 times the voltage and so deliver 3 times the current flow of the parallel battery pack. So - it will discharge 3 times faster - with the higher current (charge flow rate). Power (Watts) is a totally different thing. Power is a measure of the rate at which energy is consumed (measured in watts) and equal to VxI = I*I*R (in a simple resistive circuit). As both the Voltage and current triple in the series scenario above - the power delivery would be 9 times greater than the parallel battery scenario - but the battery would only drain 3 times faster. That tends to make me think a series connection is 3 times more efficient in terms of power delivery for the same circuit - tho that seems counter-intuitive !! There is a big difference between a mAh measurement and a Wh (Watt-hour) measurement. Looking at the units involved without worrying about values - it seems the difference is as follows: mAh is a measure of actual charge delivered thru a load (in coulombs) Power is the rate at which the energy is consumed = I*I*R. So to compare - we convert power to terms of coulombs: As Current is a measure of coulomb per second. Then I*I*R ==> (coulomb*coulomb/sec*sec) X R So - a Watt-hour is a measurement of (coulomb*coulomb per unit of time) X resistance. The Watt*hour measurement cancels out one of the time units in the denominator of the I*I*R formula - leaving a single per unit of time in the result's denominator. As the Watt-hour rating is dependent on the value of the load (ergo - the application) - not just the amount of charge - I believe a battery capacity cannot be measured in terms of Watt-hour. Anyone see anything wrong with this analysis or conclusion ??

[@Space_Reptile]

well its simple : parallel = increase in capacity but keeps the voltage the same series = increase in voltage but keeps the capacity the same rule of thumb atleast when all cells are the same , if not theres some math involved

[@KingMikeUK]

+Justagermannerd Not necessarily true, if you are using voltage regulation you can get nearly the same results as running them in parallel or series.

[@garethsighe8872]

We should also consider Peukert's Law although it less significent in lithium and NiMH compare to lead acid

[@RaspberryStraw]

Nice, but in general the charge is linked with current (as a function of time) and time with an integral (Q=Int(I)dt). The multiplication is correct only when the current is constant.

[@SuperShortVibes]

in a post apocaliptic world the item you have on your hands will worth a lot!

[@flagpoleeip]

Well done for eschewing convention and having time as the independent variable.

[@JS7457]

You should make a video on 3A TP4056 and TP5000. (Look on aliexpress)

[@deangreenhough3479]

Good point well presented, I see this video has everyone talking. I agree with others that a more detailed follow up be done. Julian, may I request you get a larger notepad😌 it appears to be a bit, well way too small. Keep up the good work

[@TheUnnamedGent]

I like it when people say milliamps per hour. Actually I hate that.

[@JulianIlett]

+TheUnnamedGent Me too. It would be like getting 'miles per hour' wrong, and calling it 'mile hours' - but nobody does that!

[@serenatyvfr]

Well explained something new to right down to remember thanks Where's post bag gone Julian coming back soon I hope

[@SadamFlu]

Thank you Julian!

[@ctrlthecontroller]

Great and useful vid, thx

[@harryjnr2335]

top job again Julian

[@Tjofrasen]

Batteries should be labeled with Watthours instead of mAh. We don't really care that much about the electric charge (mAh) when using batteries, what we do care about is the energy content (Wh).

[@JulianIlett]

+Tjofrasen Absolutely, the Ryobi 4Ah battery has 15 times more stored energy than the 4Ah NiMH 'C' cell.

[@pfeerick]

+Julian Ilett I'm still debating that one... if you *just* wanted a measure of the batteries energy potential, then Wh would be the way to go. Using (m)Ah usually forces the manufactuer to specify V as well, meaning you can compare apples with apples easily, rather than compare an apple with an apple tree :D With end-user consumer products, it makes sense to use Wh, as the end-user will never care about voltages - just how much power does it have. And it negates the whole 'this drill has a 4Ah battery' ... 'this drill has a 6Ah battery... that's better right?'... 'well no... the first is 18v, the second is 12v ... they're both about the same!!!' style confusion. But for DIYers and maker, (m)Ah and V is more important, as we need to match voltages, and then worry about capacity.

[@DupczacyBawol]

Pity you have not mentioned the voltage and power. P = U*I. So your 18V wireless drill battery is much more powerful (provides 72 watts per hour) than the little TRONIC NiMh cell (1.2*4.0=8.4 watts per hour). Minus of course the heat.

[@beachsandinspector]

interesting video, I will show my students this as it will save me time.. (amateur radio students that is ).

[@RS2Racer91]

Cells in series results in the same Ah, but higher voltage. If you would use different batteries (don't do that, its stupid) it would be the lowest Ah.

[@Chooseyouruniquehandlebyaddin]

+RS2Racer91 Not the lowest, say for example you have a 4000mah 3.7v Li-ion and a 1000mah 3.7v Li-ion in series. The capacity of the pack is not 1000mah. Its number between the two. However, once you pass 1000mah, the voltage of the pack will drop.

[@lmaoroflcopter]

electric charge is measured in another unit. it's in coulomb

[@lmaoroflcopter]

ah. well that shows me for commenting mid video.

[@user-vu1ht7gt3x]

The thing is you're explaining what's written on the battery but there is no video explaining how you can calculate amps hours of a battery by yourself I know how to calculate watts voltage times amps =watt, voltage times amp hour = watt hours can you show us how to calculate amp hours curtain batterys dont have the amp hours written

[@bobbailey8246]

...and if you put a Batteriser on each cell you get a whopping 8 times the capacity ;-)

[@harryjnr2335]

I see you have some sun there again 👍

[@TheChipmunk2008]

My first response was simply 1/1000 of an Ah And no, it wouldn't be better to measure it in another unit. Ampere Hours are much easier to work with, makes the maths simple

[@Mentorcase]

Using Wikipedia as a source of accurate facts is dodgy at best, one clown makes a statement and if nobody disagrees they slap it in there and if a whole mob mob of clowns claim the same thing even though it is total crap it stays until painfully disproven by an expert with checkable qualifications.

[@FlyingShotsman]

That's very true in areas related to persons, politics and sociology, but much less so in hard science subjects (with the possible exception of the violently debated field of climatology). The page Julian used in this video was factually correct.

[@regpollock9403]

Thank you. I have wondered about this questions.

[@alext8828]

Very excellent.

[@theriphraff]

My brain can't get passed hours. HOURS have always meant time. Now they mean how much charge. Anybody know WHY they decided to use hours?

[@guilhemane]

THANK UU Perfect explanation thx

[@iMagic16]

Love the vids :)

[@todkapuz]

sounds like its time for watt-hours

[@mcdura]

Watt hours

[@cremationpete]

300Ah

[@kimt6333]

Would only be 81Ah, as you multiply the rating on each: 3Ah*3Ah*3Ah=81Ah. ;-) ;-)

[@DreStyle]

15x1,2v = 18v Series only increase voltage, not capacity...

[@DreStyle]

And.... I fucked up... Damn you electronics... Comment below me explained the whole thing... However the amperage still is the same right... Only the power output watts will be increased by the voltage

[@erhanalankus]

Buy some real batteries and throw those fake ones away already.

[@michaelkaliski7651]

The more expensive branded lithium ion batteries usually give capacity in mAh and Watt hours on the sleeve. Ultimately it doesn't matter what units are used so long as the same units are used to compare the capacity of different batteries. Any 18650 battery claiming more than 3600 mAh capacity is a fake. Batteries with genuine capacities over 3000 mAh cost upwards of £15 each for the genuine article. Avoid cheap lithium ion batteries claiming high capacities like the plague!

[@cultistaautista]

Powerbank manufacturers are just unbearable to be honest. They specifically produce powerbanks to charge mobile phones or tablets or other USB devices that draw power at a fixed rate anyway, and state only the charge capacity on the label. It can hold something like 10 amp-hours or 20 amp-hours and so what? Its internal components (Li-Ion or Li-Polymer batteries) are most likely rated at 3.7Volts anyway, yet the powerbank itself usually converts it and outputs 5V. Why not just write the actual energy capacity in Watts/hour or joules with the internal components in mind? People sometimes naively trust the manufacturer and calculate the energy capacity by wrongly multiplying the charge by output voltage and not the intetnal batteries' one that defines the energy capacity. This is marketing bs designed to trick people into thinking they're buying something better than it is and hide the truth from them using fine print, concealing full techincal specifications, and/or the warranty sticker on the casing.

[@-Graham]

As a product tester for an ebay shop I'm seeing this more and more from people that should really know better!! Just today I specc'd 2 DAB radios that require 200mAh current. And they are Roberts branded. Wtf?!? Ifeel like a current/capacity Nazi haha!

[@TheAmmoniacal]

Watt are you talking about

[@slap_my_hand]

mAh, kmh, mph,....... those are so easy to calculate.

[@jett-rampartflyer2852]

Potato. After three years I hope yours all Yukon Gold.

[@northpappyflappy]

Soooooooo it's complicated.

[@AlternativeDIYEnergy]

Awesome. I generally charge my cells up. Put them to work and measure the load and time. If the results are good I am happy. If not I bang on some more cells. Easy and simple. just like me. I know nutting really.

[@JulianIlett]

+Alternative DIY Energy LOL :) Raymond, you always claim to know nothing - I know that's not true!

[@AlternativeDIYEnergy]

Stops the idiots having a go though doesn't it? LOL. If you claim to be an idiot. How can they call you an idiot. When I do get one. I immediatly subscribe and tell them what a great channel they have. I don't hear from them again. I discard negativity with PMA. I hope your having an amazing sunshine day like me my friend. My best regards to you and yours.

[@CryB4DieXIIV]

it's all thinking logical....

[@australianstig]

3Ah

[@dalewinchester1701]

you explained nothing

[@kierangreenhalgh6196]

Second!

[@RS2Racer91]

FIRST!

[@CarbsAndTurbos]

3'd!

[@taffythegreat1986]

Hi there I have a led flood light. The in put us 220v The transformer burnt out. It was 24v output with 900 ma+5% If I replace this with another transformer of 25v with a 250ma + 5%. Would this still be ok.