Finally! 9V battery max current tested and compared

For your viewing pleasure and project planning, I got sick and tired of wondering myself, so I bought 6 different 9V batteries and beat the crap out of them so I could determine which one can deliver the most current for high drain applications. Cost-effectiveness, workload sustainability and recovery characteristics are also covered. Hope this helps everyone with their projects!

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Sorry, but 36 minutes is too long to watch a video. Can you post a table here with the results showing the current and voltage for each test?

...R

Sorry about the length. I always try to shorten my videos but find that the content ends up being sacrificed at the expense of brevity. You could skip to 26:20, where the actual results begin or if you just want the ranking and that's it, you could skip to 31:00. There are 3 rankings according to different criteria that may be important to you.

It's very hard to read the video data on my PC screen.

What does "sustained voltage" refer to? - the values seem to be very low.

...R

Videos are for entertainment. They are nearly useless for conveying technical data.

Robin: Apologies again for the limitations of my equipment. I'm hoping to eventually get something less embarrassing to record with.

Sustained current refers to the current that the battery levels off at, after the initial surge drops the voltage down to a level where the chemical reactions can replenish the voltage and maintain an equilibrium for a while. The peak current is the highest current achieved, which isn't as useful for prolonged tasks because it's over in a few seconds usually.

JR: That tends to be the case, yes, but I have been using videos as a vehicle to teach things I've learned. Maybe that was a bad move but history has taught me that people don't like reading my essays either.

Is this preferable to the video?

https://hubpages.com/autos/9V-Battery-Current-Test-How-Many-Amps-Can-a-9V-Supply

To prevent the article from being too dense and messy, I just summarized the key parameters of each battery but it is more legible and avoids searching through the video to get what you need.

The posted material is much more useful than the video, thanks.

It would be nice if you could summarize the data in a concise 2D table. Also, discharge curves for a fixed load would be useful, like these for an alkaline AA cell:

That is 1 way to go and I know manufacturers tend to favor these types of graphs. Still, it is a quantized approach because you have to make a new curve for each current draw. Definitely useful, don't get me wrong, I use this sort of info all the time, but I was trying to fill a void that I really felt needed to be addressed. Focusing strictly on current allowed me to get the maximum resolution on how the battery's internal chemistry and resistance are bottlenecking the product, which is the extreme end of the spectrum (power vs longevity) that I felt was sorely lacking in the information department.

In future I plan to follow this up with further tests, perhaps on AA form factor and different ways of presenting the info, as you suggest.

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Can't see how placing a short circuit on a battery is going to tell you much about its capability. All you may be determining is the internal resistance of the battery, and even that claim will be questionable.
As per jremington, using fixed loads and monitoring performance with respect to time will give truly objective information

Gahhhrrrlic:
Sustained current refers to the current that the battery levels off at, after the initial surge drops the voltage down to a level where the chemical reactions can replenish the voltage and maintain an equilibrium for a while. The peak current is the highest current achieved, which isn't as useful for prolonged tasks because it's over in a few seconds usually.

I think what would be a lot more useful is the max current that can be provided at voltages of (say) 9v, 8,5v and 8.0v. After all, it is a 9v battery and output at 0.6v is likely to be irrelevant for any application that specifies a 9v battery. Also the actual durations over which each voltage can be exceeded with a few current levels that would be typical for applications that specify 9v batteries.

...R

It's a valid criticism that nobody uses a battery at such depressed voltage levels. However 1 quick way to determine how good a battery is, is to see how readily it can replenish lost power. By providing the maximum possible load, you reach an equilibrium point that will never be seen in practice but the better it performs at this load point, the more capable the electrolyte and electrodes are at reacting at a rate that can sustain those levels. It therefore follows that any lesser load would not be a problem for that particular battery. Anyone drawing 1.3A from their battery for example would have surpassed the capabilities of the Panasonic (1.2A) but the Energizer would still be capable.

Some devices like motors care more about current than voltage since it's the current that drives the magnetic field, which saturates the ferromagnetic material, which creates the torque. With such a depressed voltage, the power levels would be miniscule but for start-up this is not of primary concern and once the motor spins up, the back emf relieves much of the load from the battery, which can then produce reasonable power levels at higher voltages.

Having said all that, the point is still well taken that different load curves would be valuable information. I do agree with that wholeheartedly.

Gahhhrrrlic:
to see how readily it can replenish lost power.

That makes no sense. They are not rechargeable cells (apart from the Lithium example).

...R

To my mind what matters is the current you can draw before the voltage drops below 9V by too much. Something like 1V max drop over the full discharge curve is about the worst case you should be considering
with a 9V battery - after all you wanted 9V, not 6V, or you'd use a 6V battery?

And this has to be over the temperature range you're interested in too - battery behaviour (particularly internal
resistance) depends strongly on temperature.

Pulling high currents like that will adversely affect recharge cycles for the rechargable versions, and you get
a fraction of the rated capacity anyway - just not worth it, get the right tool for the job, and for powering motors
a zinc-carbon or alkaline PP3 cell isn't the right tool, people are constantly falling foul of this on these forums.

All good points. The point of my study was not to steer people to do things they shouldn't be doing. I just wanted to give people the data they didn't have so they knew the relative strengths and weaknesses of the batteries under high load, since to my knowledge this isn't available anywhere yet. Users should still use good judgement and plan accordingly. That's why I measured temps and talked about risks and such in my experiment.

Gahhhrrrlic:
I just wanted to give people the data they didn't have so they knew the relative strengths and weaknesses of the batteries under high load,

Sorry to be a PITA but I don't believe your data does that. What you have done is more akin to a destruction test.

For any battery "high load" means the highest current possible while the voltage remains within specification - certainly not below 8v for a nominally 9v battery.

...R

If a battery maintains its voltage under draw, it means that the energy lost was less than or equal to the energy produced by electrolytic action. I have never seen such behaviour fall within the bounds of "high drain". Any high drain application will depress the voltage as the current rises until an equilibrium point is reached where the energy made available for transport equals that being consumed. This inverse correlation is continuous, with open circuit voltage at 1 end and whatever voltage you get when only the battery's internal resistance is the load, on the other end. I have simply defined the other end of that continuum and by doing so, I have established which battery has the lowest internal resistance, which will affect performance at all voltage levels AND by graphing voltage along with it, I have also determined which battery has the most efficient electrolytic design because the battery that dissipates the most power when short circuited, can replenish lost energy more readily than those dissipating less power. It follows that for any load from infinity down to the internal resistance of the battery, the winner (at short-circuit condition) will perform better than the competition.

As an example, the Duracel and Energizer Max had equal inrush and steady state currents. However the short-circuit voltage of the Energizer was slightly higher. Also both batteries had slightly higher current than the Panasonic Alakaline but the Panasonic's voltage was higher than the Duracell. From this, 2 conclusions can be made: Energizer is better than Duracell, period. It will simply perform better at all load points because its voltage is depressed less under load, allowing for greater wattage. The second conclusion is that Panasonic has a better electrolytic design than Duracell because even with its higher internal resistance (lower current), it dissipates more power. Since max power is always achieved somewhere between min-voltage/max current and max-voltage/min-current, the Panasonic would be better when "properly" loaded to get best power but the Duracell is still better if all you want is the highest possible current.

I wasn't necessarily against doing a piece-wise study with different discrete loads and then doing some sort of interpolation to get a curve but that takes so much more time and effort so maybe in a future video I can break it down to that degree.

Gahhhrrrlic:
If a battery maintains its voltage under draw, it means that the energy lost was less than or equal to the energy produced by electrolytic action. I have never seen such behaviour fall within the bounds of "high drain". Any high drain application will depress the voltage as the current rises until an equilibrium point is reached where the energy made available for transport equals that being consumed.

I don't disagree with that. I'm just saying that the low-voltage point should not be less than 8v for a 9v battery.

If the current available at 8v is not what you consider "high" then that just shows the limitations of the battery you are working with.

...R

That's true, and I think the 9V form factor is crippled from the onset because of how the internal cell geometry prevents efficient chemical reactions. However it is rather convenient in terms of size, weight and nominal voltage for Arduino projects, just not running the chip AND a motor. Having said that, we've all seen people use 9v for that purpose before so for now at least we're stuck with 9v until it gets displaced by something else of similar price point, availability, size, etc.

Gahhhrrrlic:
However it is rather convenient in terms of size, weight and nominal voltage for Arduino projects

I routinely advise people NOT to use those small 9v batteries for Arduino projects. A pack of 6 x AA cells would make a lot more sense.

You can also run an Uno or Mega from 3 x AA cells (4.5v) connected to the 5v pin - which avoids the energy waste in the voltage regulator.

...R