Talking AA's here, but the throw away one's are 1.5v, I can only find rechargables that are 1.2v, why?
Something I put 4 AA's in will be 6v, but if I use rechargables it will only be 4.8v, or it will be 4x at 1.5v or 4x at 1.2v, quite a difference, so the battery indicator on the device only reads 3/4 full with the recharable, so surely it will run out or shut down quicker than if using throw-aways?
Why, why, why cant they charge to 1.5v ?
😕
Does your device have a 'battery type' selection option in one of its menus?
the voltage is determined by the chemicals used to make the battery, and can only be changed by using different materials...
No, device doesn't have 'battery type' options in the menu, it's ok for use with rechargables, but I just wonder (well, I expect it will) if it'll automatically shut down sooner than using throw aways like energizer, so I'll have to watch the power indicator a bit more.
sfb - so I'm guessing that the chemicals that are used in the rechargable batteries cannot be changed to something different, otherwise I suppose they would not be rechargable but single use chemicals, so will never be able to be 1.5v ?
sfb - so I'm guessing that the chemicals that are used in the rechargable batteries cannot be changed to something different, otherwise I suppose they would not be rechargable but single use chemicals, so will never be able to be 1.5v ?
well, you can make batteries from all sorts of things, but only certain combinations make reliable rechargeable cells, and I've not heard of any that give 1.5V
The voltage is less because the chemicals used are different for rechargables. Just because the voltage is less it doesn't mean that the capacity ( amount of energy stored )of the battery will be less than the equivalent alkaline.
Just because the voltage is less it doesn't mean that the capacity ( amount of energy stored )of the battery will be less than the equivalent alkaline.
but it will be - rechargeables have a lower power density than primary cells
but it will be - rechargeables have a lower power density than primary cells
Not so. It does depend on the actual type and spec, but apart from specialist items like Lithium primary cells, a decent modern NiMH at around 2500 mAH will have a higher capacity than most primaries.
a decent modern NiMH at around 2500 mAH will have a higher capacity than most primaries.
ah, OK, I thought the Duracell type still had a slight edge...
To get back to the OP's query, 1.2 or 1.5 volts will only very rarely matter, I'd guess with a very voltage-sensitive device which also has a very low wattage.
[url= http://www.eznec.com/Amateur/1.5_vs_1.2_Volt_Batteries.pdf ]This explains why quite neatly.[/url]
A 1.2 volt drop on a 6v device is huge. Try running your RC servos at 4.8 instead of 6v and see how much the torque drops, it's even given in servo specs. I could get the brakes to work on my nitro truck with 4.8, but 6v did the job. Same would hold true for light sources? Does your LED torch glow as bright with 4.8 instead of 6?, a filament light sure doesn't.
1.5v alkaline cells drop their voltage continuously so spend a lot of their life much lower than 1.5v; NiCad and NiMH are only 1.2v but stay at 1.2 pretty solidly then drop off rapidly at the end. Most things designed for alkaline cells are pretty happy at lower voltages.
If it is a big deal it is possible to recharge non rechargeable cells with a funky charger. Not tried it myself, but a friend had one and worked.
Odd that that is the case ChopperT, as 'torque' would be more due to the ability to draw on the power, and as rechargables have a lower internal resistance than an average alkaline battery it should be the other way round.
Torque of a servo motor will be determined by internal resistance. The soon-to-be-banned (batteries and accumulators directive) NiCd have a really low Ri compared to Duracell which is why the cordless power tool boys (as well as emergency lighting people, for different reasons) are members of CollectNiCad, a lobby group to find alternatives to a ban.
Alkaline and carbon-zinc cells have different chemistries but approximately the same emf of 1.5 volts; likewise NiCd and NiMH cells have different chemistries, but approximately the same emf of 1.2 volts.[29] On the other hand the high electrochemical potential changes in the reactions of lithium compounds give lithium cells emfs of 3 volts or more.[30]
Which is why rechargables are 1.2v....