I do not try to justify anything, I'm just trying to clarify that your oversimplification ("huge waste of energy") based on the fact that you lose 20x or 40x more over the RESISTIVE LOSES IN THE BATTERY is an exaggeration. Yea, sure if you're using a 1/10C charger for a 2Ah battery you're pissing away only 1mW "resistively", sure. And energy-wise you'll be using 40x more with a 4C charger. But it won't be 40 times the TOTAL losses, it will be 40x those tiny resistive loses. There are more loses in the battery itself (no, you don't get a charging efficiency of 99.5% with NiMh, even at 1/10C), losses in the charger, etc. You need to be looking at the whole package.
Quote from: PowerStreamThe coulometric charging efficiency of nickel metal hydride batteries is typically 66%, meaning that you must put 150 amp hours into the battery for every 100 amp hours you get out. The faster you charge the worse this gets.
Since resistive losses increase with the square of the current, I'm surprised the "4A" with 3 or 4 cells is implemented as a 50% duty cycle of 8A switched between the two banks. If they just did a constant 4A, it would theoretically cut the resistance losses in half.
Yes, but it would cost much more in the inductor of the DC/DC converter to allow for the higher dynamic in voltage
The additional loss per mosfet is in the order of 72mW, which is negligible, especially considering they have fan cooling
Quote from: PowerStreamThe coulometric charging efficiency of nickel metal hydride batteries is typically 66%, meaning that you must put 150 amp hours into the battery for every 100 amp hours you get out. The faster you charge the worse this gets.
It is more like 90% to 95%, except the last part.
Quote from: PowerStreamThe coulometric charging efficiency of nickel metal hydride batteries is typically 66%, meaning that you must put 150 amp hours into the battery for every 100 amp hours you get out. The faster you charge the worse this gets.
It is more like 90% to 95%, except the last part.
No, NiMH is inherently much less efficient. This has to do with the difference between electrode potential and neutral charging voltage, which annoyingly both change throughout charging/discharging.
Instead of writing theories, try measuring it, I did.
Instead of writing theories, try measuring it, I did.
Maybe you should take that up with PowerStream, since you apparently know far more about batteries than they do. It's not like it's their core business or anything.
Instead of writing theories, try measuring it, I did.
Maybe you should take that up with PowerStream, since you apparently know far more about batteries than they do. It's not like it's their core business or anything.
They and you can just read on my website, where this will be published, together with all my other battery stuff. You could also do you own testing and learn something, instead of just believing a random article.
Do you have a link?
Why is there even an argument about the energy efficiency of the charger, no-one is going to buy a 15 min NiMh charger based on the efficiency!
(and my parents were too cheap (or devious) to have enough spares that could be charged in advance)
Instead of writing theories, try measuring it, I did.
Maybe you should take that up with PowerStream, since you apparently know far more about batteries than they do. It's not like it's their core business or anything.
They and you can just read on my website, where this will be published, together with all my other battery stuff. You could also do you own testing and learn something, instead of just believing a random article.
I did not seen any efficiency value of batteries...
What efficiency are you speaking about ?
Faraday or energetic efficiency ?
Energetic efficiency is lower than Faraday one.
How will you measure and calculate energetic efficiency of a AA battery ?
Easiest way would be to charge and discharge the battery at constant power and measure the times of charge and discharge.
You can discharge the battery at constant power with your electronic load, but how are you charging the battery with constant power ?
Your power supply does not have this option.
Ok, that's the Faraday efficiency, that's the reason why your values are so high.
The true efficiency is the energetic efficiency, that's how much energy in and how much energy out.
I suggest you to measure this efficiency and not the Faraday efficiency who does not mean nothing !
Instead of writing theories, try measuring it, I did.
Maybe you should take that up with PowerStream, since you apparently know far more about batteries than they do. It's not like it's their core business or anything.
They and you can just read on my website, where this will be published, together with all my other battery stuff. You could also do you own testing and learn something, instead of just believing a random article.
I suspect your test methodology was incorrect then, though as we can't see it we can't tell.
Coulombic efficiency can be high if you only partly charge the cells, but rapidly drops as you approach full capacity and 66% is a typical figure for a fully charged NiMh cell.
I do have the voltages during charge and discharge and can calculate the energy efficiency, if I can find the time I may do it.
@HKJ:QuoteI do have the voltages during charge and discharge and can calculate the energy efficiency, if I can find the time I may do it.Calculate ? I wonder how you could do this as voltages are varying during charge and discharge in fonction of the time at a non linear rate ?
Could you explain how should you calculate the energetic efficiency ? What are the formulas you intend to use ?
That's an approximation, but it is ok.
Have you already make this calculation for one kind of battery ? (as eneloop for example).
I am curious to see wat you find as energetic efficiency. I have in mind something like 80 to 90% but I did not measure this.
I hope you will share the results of your compiled data, it will be very interesting, you have done a very fine job