MegaSack DRAW - This year's winner is user - rgwb
We will be in touch
Is there a formula or reference table or any info on how much energy is required to recharge a Li-ion battery? We are required to include this info in a purchase document showing the environmental impact, the instrument runs on Li-ion batteries (believed to be 7v, 3.3A), any one know how much power would be required to recharge them?
the pack will likely be 7.4V. the capacity [i]may[/i] be 3.3Ah. check this out cos you'll need to know.
normally you charge at 0.2C to 0.7C.
'c' being capacity of the pack in Ah or mAh.
likely you will be able to work the nominal numbers out from the power ( W ) of the charger, the time taken to charge the battery from flat will give you the charge rate ( average ), and you know the voltage of the pack too....
I take it you've asked the manufacturer?
likely you will be able to work the nominal numbers out from the power ( W ) of the charger, the time taken to charge the battery from flat will give you the charge rate ( average ), and you know the voltage of the pack too
Apart from that charging LiIon batteries is a non linear process, so knowing the total charge time isn't terribly helpful - you need the charge rate against time profile.
7.4V. the capacity may be 3.3Ah
would be 7.4 x 3.3 x 3600 = 87912 Joules, however, you'd have to add 30..50% extra for the various inefficiencies involved.
The product datasheet will tell you all this. There is a formula for it, have to tried googling it?
Apart from that charging LiIon batteries is a non linear process, so knowing the total charge time isn't terribly helpful - you need the charge rate against time profile.
yeah - i'm aware of that. that's why i put 'average'. doubt we're looking for an answer to the last decimal place here.
your answer on the other hand was really helpful. 😉
Oh, and don't forget that charging batteries isn't 100% efficient, normally around ~80% efficient IIRC.
yeah - i'm aware of that. that's why i put 'average'. doubt we're looking for an answer to the last decimal place here.
OK, so how do you calculate the average from known parameters, given that if you double the initial charging rate for a liion you won't halve the charging time, and the average is significantly different to either the initial charging rate or the mean of the initial and final rates? Your method is no more accurate than using Simon's approximation of calculating energy stored then adding a nominal 30%.
Pointing out the failings in your method makes my post more useful than yours, since if they follow your advice they'll get the wrong answer (to rather more than one decimal place).
good grief.
i was just trying to get the guy an approximate answer, even if i'd just asked enough questions to encourage him to rtfm.
i already know enough people happy to testify that i'm a cock. there's no need for you to attempt to prove it from a distance...
have a nice weekend eh?
please don't fill your handbags with rechargeable batteries...