Just to complicate matters, what if I used two 26 Ah alkaline 6V lantern batteries in series? It might be more difficult to waterproof package them, of course, and they'd be a bit bulkier. This is not that complicated, and your latest question is whether 26 is bigger than If you gave two more similar numbers, like 17 and 19, you should just try it and time it if it matters much if one does 8 hours and the other does 8.
Jan, Thanks for all the advice. Hey there! I only have one question. That part is easy. Given any two values, you can determine the remaining value. What I still don't understand though, is how can one find the maximum amp draw of a given power source? For example, one AA battery might have a full capacity of 2 amps an hour, or 2 amp hours.
But how many amps per hour can flow through the battery? How do you calculate the limit before resistance and heat become so great that the amp draw cannot go any higher?
Could you literally draw 4, 8, Of course understanding that the cell will fail in under a minute at such a high draw rate. Thank you. I did some more googling and it sounds like you just need the "C" rating.
For example, a 2AH 1C battery can be discharged at 2 amps per hour. And a 2AH 10C battery can be discharged at 20 amps per hour.
Matt, As long as you are talking about "amps per hour", you do not understand it. Units like amps and watts are already rates coulombs per second and joules per second, respectively. As for your main question, I specifically went over it in the post, and you got it right in your follow up post, except for the "per hour" part: a 2Ah, 10C battery can deliver 20 amps. Mark G. The motor failed on my first trip.
Suspecting it had burned out, I touched the housing immediately after stopping, but it was cool. My question is, did the higher aH batteries cause the motor to fail, or is this just a coincidence? Just changing the batteries for higher capacity ones shouldn't cause your motor to die.
However, there might be other factors like the new batteries being heavier, which could put more strain on your motor and lead to the failure. You also wrote "batteries" plural ; if you originally had something like two in parallel and changed it to two in series, you would have gone from 12 V to 24 V, and that could definitely lead to your motor wearing out quickly.
A final thought I have is that the motor is not necessarily what broke; have you verified that independently? The things like higher load and higher voltage that could damage your motor could also damage the control electronics.
You are correct, Sir. It was my presumption the motor had burned up; it turned out to be a pebble in my brakes. I have installed the new batteries and the old girl is now able to go 'round the horn without difficulty. Thanks for the confirmation I was only increasing capacity. Mark, I am happy to hear you figured out your problem. For anyone else reading this, I should point out that the three batteries in series make it a 36 V system, not a 36 watt system that will depend on the current.
Hi, I have one question, I have a device consuming a 3V button cell every two weeks, would it be possible to substitute this button cell for two AA batteries expecting longer replacement time?
Or are button cells providing lower current than standard batteries? Ark A. Since AA batteries are about the amount of mAh in my phone, could I theoretically use some sort of apparatus that plugs into my phone and runs on AA batteries to charge my phone on the go?
I know lithium is more convenient because it is rechargeable, but AA is more convenient if cost-defective because I can buy it on the go and don't need a charger for the car or outlet when I'm really busy.
By the way, credit for still looking at comments and replying after 3 years. Hello Jan! My question is: If I have two batteries, one being a 12v 1. I know it is a bad example but.. If you lick the terminals of a 9v 1. Can two batteries with the same voltage push different amps trough you if they have different capacities Ah ratings? Does this have anything to do with the discharge rate: the "C" rating? And kudos for you, for still answering this questions after two years!
Manuel: Two AA batteries will likely last a lot longer than a button cell battery, which is usually used because of space or weight constraints. So if those are not issues for you, you should be fine. Milani: no, batteries do not "push" current into your circuit. The higher capacity battery will just deliver the current for a longer time. Ranjit Singh. Hi Jan, Big thanks to you for sharing these information on basic understanding of batteries.
Many people can clear their doubts regarding batteries. Also, replying to queries means you really deserve a Hats off plus standing applause. Thanks again to you for your efforts.
With Regards, Ranjit Singh. Hello Jan, Total newby to battery specs. I stubbled across this thread looking for an explanation to batteries on phones and how power is transfered to them by portable battery packs. Sorry this is not about running a robot, but you seem to have your head on straight about this subject of batteries. I have an iphone 5, it has a mAh battery.
I am looking to buy a mAh portable battery pack to recharge it. Or are there other factors involved here? In general, you should go off of the watt-hours specification, not amp-hours, because the voltages might be different. In your case, the batteries are about the same voltage, but going by the Wh specs of You definitely are not going to get perfect energy transfer. I don't know how efficient the power bank is at boosting its 3. Multiply that back by that 9. The technical specs for the fan says the following: Power input 13W; therefore I have calculated the current required the draw?
Making this simple if I round the current required to 0. Apologies if this is answered in some other way in the previous posts but I have read them all several times and I want to make sure that I am understanding this correctly.
Thanks, Jack. So, I would expect more like one hour of run time. By the way, it should be pretty easy to find 12 V batteries, so you can put two of them in series to get to 24 V.
Kiran R. Hi Jan, Its great post about batteries. I'm new robotic stuff, apparently I have to build a line following robot with Obstacle avoidance.
I'm using a Arduino and SeedStudio motor driver to build a robot. I'm using four 1. It is working perfectly when I used it only as line following robot. But I added a ping sensor to avoid the obstacles along with line following, it is not moving at all. Interesting thing is when I connected the USB cable to Arduino along with batteries it is moving forward.
So I could draw some conclusion that current required for circuit with ping sensor is enough when I connected USB and batteries. But I wann know I can increase the current in my circuit. You reply is much appreciated. If let me know if you need more details.
Kiran, I'd like to keep the discussion here focused on batteries and their capacity. I suspect the answer to your question has more to do with the rest of your system than with the batteries, so please ask your question in a more appropriate place such as our forum. You could try NiMH batteries instead of alkalines to get a quick idea of whether it's a battery current limitation. Olen Sluder.
I knew the information, but this makes it very succinct for a beginner. Kire S. Hello, im also new in the forum and not so good with electics. I have a bosch hammer batery driller, im using it for making rock climbing routes, over 1 year period the bateries are almost dead, and they are quite expensive to buy.
I was thinking if i can use an motorcicle batery 12v 6ah for my driller. The original bateries are rated 24v 3ah. Thanks in front Kire S. However, you're probably not going to get much performance with just the 12 V battery when the motor expects 24 V, so you would need to connect two of your motorcycle batteries in series.
You should also make sure the batteries are sealed if you will be using your contraption in all kinds of angles. Thank you Jan, i will try it first with only one battery, if the power is not suficcient i will conect two of them. Thank you and i will write after the work is done. Faisal Ahmed. Hi Jan, Great information here.
Very educational and explained in a very basic manner. Just one correction though about M. Milani's question: "My question is: If I have two batteries, one being a 12v 1. In this case the battery with 9V can only give him a tingle on the tounge, whereas the bigger battery size, rating and voltage wise will have a higher charge stored and also a higher voltage, and so will give him some burn on the toungue too as it will deliver more Amps when shorted.
Please correct me if I am wrong here. Thank you! Faisal, The question was about capacity in Ah, not about voltage. Higher voltage will cause higher current to flow; M.
Milani specifically asked for the same voltage. By the way, talking about a battery "storing charge" is probably not helpful since it's not a capacitor. Also, be careful about mixing various characteristics like voltage and maximum current with attributes like size: physically larger batteries are not necessarily going to have higher voltages than smaller ones.
Good stuff. I've worked with alternating current primarily so this was very helpful. I'm building a tricycle with a front hub motor and a small audio amplifier on it.
I've checked the tech specs and it does watts rms at 14v and draws 22a rms I was looking into using new lifepo4 batteries but idk how big of a battery I need. I use two kinetic hc there 25ah 12v. I want to be able to play the music for about 6hr like I do now. I want to cut weight but keep a big reserve for pedal assist but all these lifepo4 specs and discharging things are confusing me. Daniel, I think you should be able to figure this out if you read the post and other comments carefully or your question is something more complicated that I am not following.
I'm not clear on this audio amplifier vs. If your 22 A spec is not continuous but something like just when you're accelerating or going uphill, you might get a lot longer battery life based on the actual load you put on the motor over the course of the 6 hours. In that case, it seems like you already have these parts so you could just see how long the batteries last in your typical scenario. If your two batteries last 4 hours, you'd need one more to last 6 hours, and so on.
Gerard M. Hi Jan Glad i came across this blog, you really seem to know your stuff! I would like your advice about some power banks I have recently purchased from china as i am currently in dispute over the specification with the supplier. The power banks i purchased state that they are 50Ah capacity. I do have some degree of electronical knowledge as i studied a-level technology and briefly studied electrical engineering several years back.
As you have mentioned in a previous point i was going on the basis that this would provide 1A for 50 hours and inversely would take 50hrs to charge at a rate of 1A. I have included two extracts Sorry about the big post from the supplier below and would hope you can make more sense than me of this as the english is terrible! What I would like to know is if i am misunderstanding the specification and the correct definition is actually 50Ah or is the supplier trying to con me? The really full charge mah battery is more than 5KG weight.
It is very dangerous and inconvenient. So the market is almost no more than mah, let alone mah. Special Note: our solar power bank built-in electric current and voltage protection of mah, if your area voltage instability or excessive current input, our mah play a very large role in the protection, safeguard the security of each buyer, which is also the advantage of our products and new technologies, so this product is defined as solar power bank mah, you understand it?
Simultaneously protected and will not explode this is the EU's safety standards, but it is when the output current. Hi, Gerard.
First, a little nitpick: a battery that can do 1A discharge for 50 hours does not mean it can get charged in 50 hours at 1A. But still, if you're getting a full charge at 1A in 10 hours and not doing anything special voltage-wise, you can be sure the capacity is nowhere near 50 Ah. Your supplier seems to acknowledge that the actual capacity is 12 Ah and gives you the basic math that a battery with 50 Ah would weigh over 10 pounds.
I don't know what your actual thing weighs, but if it's a couple of pounds, then that would be another sanity check that your battery has nowhere near 50 Ah. The last part does start sounding like BS. Maybe he's just trying to say that the electronics is good enough to support a 50 Ah battery if you had one there. Perhaps this is some modular product where the battery part can be upgraded or retrofitted. Hello, New bee here.
I am building an e. What should my battery specs be if I put 48 volts only? My load should be lbs. Please help. Follow up. Reason for under. Voltage is weight and space. BTW , what happens to ah amp hour if I put the batteries in series? Are you building a motorized scooter? You should be supplying your motor with 90 volts like it says, then I assume you have some kind of circuit for modulating it's speed??? I think you missed the point of the topic. The "Ah" of the battery is it's capacity, not how much current it can discharge into a short.
A car battery can discharge a lot more current a lot faster than other types of batteries. For your applications, lead acid should be sufficient. I going to pretend you find 90Volts like the specs demand. If you find a 90 Volt, 12Ah battery, your motor should run great for about 3 hours, then it'll be slowing down. Remember, V AC doesn't seem very scary. But you stick to DC voltage.
Be careful. Oh, and the Ah don't add or anything if the batteries are in series. Just your voltage goes up. If you put different rated batteries in series you shouldn't do that then you can more or less take an average of the Ah rating.
But if you use different types of batteries with different ratings it'll affect the performance and life of your batteries. Hi Jan, This was a great article. I'm a little confused though. Are you saying that a single AAA battery will last longer than a single 9 volt battery?
It's like asking how many days until you need to refuel your car that has a gallon gas tank without saying anything about how much you drive per day. As I said in the 9V alkaline battery example, you're basically going to get about the same amount of energy per weight for any given battery chemistry, so since a 9V weighs about the same as a AA, it's going to have about the same amount of energy, and since energy is measured in Wh, which is Ah times V, a 9V battery will have about six times lower mAh rating than a 1.
If you happen to know your application for the 9V draws the same current as a specific application for AA or AAA, then yeah, it will not last as long, but that kind of situation is rare since there aren't many products that can run from either 9V or 1.
I am not sure if I did this correctly or if this will post twice, but I am looking for battery feedback on replacements for an electric scooter. My first guess is that it's a typo or other mistake; my second one is that it's 12Ah at a five hour discharge rate. If the batteries weigh about the same and have similar dimensions, their capacities will be similar.
Ok, i was reading thourhg the post, but didn't get really andswer of what my question was, so i allow myself to add some new!!!
I am user of an audio device, the H4n recorder, using phantom power mic on. The h4n is using 2 AA batteries but by giving 48v to the mic, the power runs down very fast. And i need to be able to record sound for longer period than one hour!!! But when i check the battery they give more 1,25V than 1,2V, so than would come pretty close to 5V. But i can't understand the link. If i put 4 AA, i am supposed to get way more than 1A Is there a risk of burning the audio device?
Or this 1A just means that is what it request from the battery to operate, and they will gently give it enough Some electrician in a store told me i would have hard time to run the device, as i would hardly get the 1A requested Shall i make to sets of 4 AA in parallele, getting still 5V but more power I stumbled across this article as part of some research into project.
I will be turning the back of my pickup truck into a small camper and will be powering an inverter with a deep cycle battery from a semi. My main concern is with charging. From what i understand about lead acid batteries, they require little to no circuitry for charging. As such I am planning on connecting this secondary battery up directly to the rest of the charging system primary battery included.
The only circuitry I will be adding is a relay to disconnect the secondary battery when the ignition is turned off so I do not accidentally discharge the primary whilst I am camping. My main concern is whether or not I will see any adverse effects. What do you think? Tchopko, I am concerned that with the level of electronics understanding you have presented, you might be risking damaging or destroying some fairly expensive equipment. On to your specific case.
First off, you should realize that with four batteries instead of the built-in two, you will get at most 2x the battery life. You should not put your batteries in parallel, and if you just put all your batteries in parallel, you would only have the 1. You should also go through a regulator, too, to make sure you actually give your device the 5V it is expecting since the fully charged batteries might be 5.
But, if you go down this path, make sure you get a better understanding of what you are doing and that you are ready for the consequences if you make a mistake. Keisler: I don't know enough about your system to know for sure.
There's got to be some limit on your alternator and whatever battery charging circuit is in your car, and while my impression is that lead acid batteries are among the more forgiving regarding charging, you still might limit their life or otherwise damage them if you just do what you are proposing. Hi and thank you for sharing of your experience. Clearly there is a need for information such as this. Here is my inquiry: I plan on running two 50mm fans inside a costume helmet for air circulation.
The fans spec at 5v 0. I wanted to power these two fans using one of those portable lithium-ion cell phone back up batteries mainly due to their compact size. Limited space inside a helmet Most other costumers use 4x AA batteries 6v my question is can I expect similar battery life using a 5v mAh battery pack instead? Other than voltage and capacity no other specs are provided for the battery pack. Thank you in advance. Adam, Why don't you just try it? And I don't mean that in the "go for it" sense.
I'm wondering what motivated you to write here as opposed to trying it and timing it. Thank you Jan, my motivation was hoping to get a rough idea of run time based on mathematical formula before I invested in some equipment.
But you are right I could just try it As a rough approximation within a factor of two , I would expect similar battery life. The main thing I'm skeptical about is that 5V is not a natural voltage for a lithium ion battery.
If there's actually a 3. Thank you Jan for the info. I will be testing the set up shortly. I only need run time of 5 hours at a time. Adam, I'm going to try to answer your question. Jan, Please comment if I got this wrong. Two fans each 5v and. But more than 5 hours.
Stay cool. Anonymous, You start out ok, up through where you got the 20 mA, but then you got sloppy with the units in exactly the way this blog post was supposed to help people avoid. It would be correct to say the battery will deliver 10 mAh in 30 minutes. I've crossed out the incorrect parts in your comment in the hopes that it will help others avoid this kind of mistake. The 65 hour result based on the starting assumptions is right, though. Hi Jan, Thanks for the very helpful information, I've learned quite a bit.
But I am still unsure of how to go about connecting my 5 watt portable amplifier. It is powered by an AC adapter or 6 "C" type batteries. I want to play my acoustic guitar hooked up to the amplifier but since I live in S. America, "C" type batteries are hard to find, and very expensive. I am thinking of buying an inverter smallest I could find was watt capacity and a 12 volt motorcycle battery for portability but I am unsure of how to proceed with the 12 volt battery.
What aH would suit me best? I would only be using the amplifier for minutes at a time. Thank you for your time and expertise! Jon, More Ah will just last longer, and since you don't need much, it seems like the primary consideration should be size or weight.
You can probably get by with just using AA batteries. You could either set up your own battery holder or get some AA to C battery adapters, which are just sleeves or shells that fit around AA batteries to make the final diameter match that of C batteries. It won't really tell you much useful for normal operation- you could look up the voltage across your meter when reading 10A maybe mV and get some kind of an estimate of the internal resistance, but there are electrochemical effects "polarization" that will cause the short-circuit current to drop quickly from the peak.
As the cell discharges the internal resistance goes up, so it's not going to give you a good idea of what happens during the cell life if you're drawing current in short pulses.
If your purpose is to get an idea of the maximum fault current for example for the breaking current of protection circuitry it could be a useful exercise. Method 1. For safely and accurately measuring the near short-circuit current from a battery you need to set up a pulsed load. Such a load can consist of an oscillator with low duty cycle, say 10 ms pulse every second, driving the base of a NPN power transistor such as 2N Use the oscilloscope to measure the voltage pulse across the resistor: a 10V pulse means thre battery is delivering 10A current pulses.
Note that this method measures using a near short circuit; it is difficult to get much closer to a true short circuit. Method 2. This method measures the internal resistance of the battery without drawing current. Connect a uF capacitor electrolytic type, note polarity! Use the oscilloscope to measure the peak-to-peak voltages across the battery and across the 50 ohm. Their ratio gives the battery internal resistance which one can expect to be the only limit on the initial current if the battery should be short circuited.
The test probes will present a significant source of resistance, and you won't get an accurate measurement of the power output unless your final design also uses hand pressure of test probes to the cell contacts. Consider building a test battery holder that has banana plugs you can connect to your multimeter.
Look for a battery holder that has good mechanical contact. This will give you more power from the battery by decreasing the contact resistance - and in high current applications like this it will be a significant source of power loss. But even battery holders at least the common ones aren't meant for more than 1A current.
Groups such as flashlight builders and radio control model enthusiasts run into this issue and of the several suggestions I've seen, it looks like the best is to use copper braid to face the spring contacts, then solder a heavier gauge wire to the copper braid. This presents a high current, low resistance contact to the battery, and allows you to get the most current from the battery that you can.
Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. How to calculate the maximum current a AA battery can deliver for a short period of time? Ask Question. Asked 6 years, 7 months ago. Active 4 years, 9 months ago. Viewed 44k times. My current multimeter has an input rated 10A for max 30 seconds plug negative probe to negative side of battery plug positive probe to positive side of battery for one or two seconds read value on device Usually when you need to measure current for given load, the multimeter is wired in series in the circuit.
Read the data sheet and if the battery doesn't have a data sheet don't bother testing it and get a battery that has a data sheet. Safety needs to be considered but has so far not provd an issue for me. It's what we all have to do in engineering and, if you don't understand this or that then raise a question.
Data sheet understanding is paramount in EE and this is not something I say lightly. It will either give a max sustained current, max pulse current, or a graph showing capacity as a function of current drawn.
For instance if I have 5 amp-hours available, can I run a 5-amp motor for an hour? Or a amp motor for half an hour? Or is there some lower limit of the current draw of the motor, and determined by If someone knows the answer, I'm assuming it's a quite simple, one- sentence answer. A link would be appreciated as well. You will have now 5 amp-hours, and so you can run. Batteries have an inner resitance, which limits the current they can deliver. If you connect in parallel, max current will double.
That clears things up somewhat. However, you did not provide a specific answer to my question: " Track My Order. Frequently Asked Questions. International Shipping Info.
Send Email. Mon-Fri, 9am to 12pm and 1pm to 5pm U. Mountain Time:. When you're powering a remote circuit, the same issues of finding a battery that delivers the proper voltage and current still apply. Battery life, or capacity, is a measure of total charge the battery contains.
The capacity of a battery is usually rated in ampere-hours Ah or milliampere-hours mAh , and it tells you how many amps a fully charged battery can supply over a period of one hour. For example, a mAh battery can supply up to 2A mA for one hour. Battery size, shape, and weight is also something to consider when making your project mobile, especially if it's going to be on something that flies like a small quad-copter.
You can get a rough idea of the variety by visiting this Wikipedia list.
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