I just want to double check that this means that when the motor is under a 'normal' load, then the current draw is roughly 0.20A and when the motor is torqued to the point of stalling then during the stall 0.27A are being drawn, correct? Running at 1.5v instead of 3v should not affect the current rating, correct?
My 1.5v Li-ion battery claims to be 1500mah, so at 0.20A (normal load on motor) I should expect the motor to run consistently at 1.5 volts for roughly 7 hours (since 1.5/.2 = 7.5), correct? And running two of these batteries in parallel will double to 3000mah and provide between 14 and 15 hours of consistent use, yes?
Your calculation method is fine but if the motor current specified is at 3V the at 1.5V the current and so the motor power will be lower. So if the battery performs as stated in that advert then you should get at least 12 hours from a single battery. Try it and see.
moses1592:
I am using these, they have built in step down:
Ah, never seen those before.
So what's the advantage, other than USB charging? Those AA size seem to have 1500mAh capacity. Most of the low-self-discharge NiMH AA that I have are 2000mAh. Li-Ion are supposed to be double the energy density of conventional cells, so I would hope for USB charging and at least a similar capacity, preferably a little more.
So what's the advantage, other than USB charging? Those AA size seem to have 1500mAh capacity. Most of the low-self-discharge NiMH AA that I have are 2000mAh. Li-Ion are supposed to be double the energy density of conventional cells, so I would hope for USB charging and at least a similar capacity, preferably a little more.
Just from personal experience I have had bad luck with NiMMH's over the long run holding charge consistently. I know this is probably my fault from letting the cells sit too long without charging them or not doing full cycle charges or something similar. Plus I like how the Li-Ion's are quick charge, don't need a charger, and maintain a consistent 1.5 volt with no voltage drop until the internal protection circuit cuts power entirely to prevent over-discharge. Plus each can be charged individually where all the AA equivalent NiMH's I've seen need to be slow charged in pairs. Maybe this has changed or isn't the case now but if it is then I am unaware of it. I've only ever used the basic NiMH chargers that come with rechargeable batteries that can be purchased at any random department store.
moses1592:
Plus each can be charged individually where all the AA equivalent NiMH's I've seen need to be slow charged in pairs. Maybe this has changed or isn't the case now but if it is then I am unaware of it.
I have had a charger that does individual NiMh cells for longer that I can reliably remember, 20+ years maybe.
But then I would not expect to buy such a charger at the local supermarket.
Yes, I also have an "intelligent" charger which automatically detects and charges NiMH or Li-Ion and will charge single or odd numbers of batteries. It also tests batteries to measure their voltage and capacity. It's pretty useful. My only criticism is that is does not reliably charge 10440 size (=AAA) Li-Ion batteries.
So what's the advantage, other than USB charging? Those AA size seem to have 1500mAh capacity. Most of the low-self-discharge NiMH AA that I have are 2000mAh. Li-Ion are supposed to be double the energy density of conventional cells, so I would hope for USB charging and at least a similar capacity, preferably a little more.
They're probably lower capacity than one might otherwise expect because of the volume taken up by the electronics. It would be interesting to see one taken apart to see how much of the device is actually battery.
NiMH batteries have a nominal voltage of 1.2 Volts and some equipment designed for disposable alkaline cells aren't happy with the lower voltage. I have a digital camera that has never worked right with NiMH rechargables.
As per post #8 NiMH batteries typically have high self-discharge rates so they're not great for applications where they're expected to go months between charges. That said, these regulated Li-Ion cells might not do well in micro current applications due to inefficiencies in the voltage converter electronics.
slipstick:
Your calculation method is fine but if the motor current specified is at 3V the at 1.5V the current and so the motor power will be lower. So if the battery performs as stated in that advert then you should get at least 12 hours from a single battery. Try it and see.
Steve
You were right. Over ten hours of consistent operation.