Thread: Query on Sanyo batteries and Uniross charger

charging current is written as 70mA, so it might take about 30 hours to charge the battery
also the red led light is an indicator of charging. it might turn green after charging is complete.

Originally Posted by 6pack

charging current is written as 70mA, so it might take about 30 hours to charge the battery
also the red led light is an indicator of charging. it might turn green after charging is complete.

Thanks
2100 uniross had charging time as 16 hours written on it, this one will take 30 hrs
so does it depend on charger to charger, how do i exactly calculate how long it will take for charging a particular type of battery

No, it doesn't turn on green or something, it stays only red i think, its also not mentioned on its features abt LED changing when fully charged

charging time depends upon charging current. lesser the current more time it takes.
the 16 hour time will be wrt to 150-200mA charging rate.

i calculated by just dividing the cell rating (2500) upon charging rate (70) which will give rough estimate. it can differ by an hour or two. also rating on cell is approx. i've seen some batteries charge to much less than given on the battery.

also found a site to calculate the charging times Rechargeable battery charging time and mA current calculator | Convert to units measures.
basics of calculating charging time is given on this site.

how did you get the batteries shipped?

Now I am not sure what it is like with today's cells but I have done a lot of study on charging Lead acid and NiCd a decade or two ago. Using that experience, I would say for 2500 mAH cells you would need around 3500 mAH for full charge because you need a 40% overcharge due to the inefficiency of the 2 way conversion (electrical to chemical and vice versa).
Therefore the charge time with 4 AA cells would be about 50 hours. I think this charger must be for 800 mAh cells which it should be able to charge in 16 hours. (800*1.4/70)
For your batteries, the only Uniross charger I would consider is the Xpress 700 which is a really good charger.

Thanks 6pack and Emil

If i divide 2500 / 70 ~ 35
Will it be the same for 2 batteries and 4 batteries together

or 4 batteries charged together - would need 2* 35 = 70 hours to get them fully charged

Originally Posted by 6pack

charging time depends upon charging current. lesser the current more time it takes.
the 16 hour time will be wrt to 150-200mA charging rate.

i calculated by just dividing the cell rating (2500) upon charging rate (70) which will give rough estimate. it can differ by an hour or two. also rating on cell is approx. i've seen some batteries charge to much less than given on the battery.

also found a site to calculate the charging times Rechargeable battery charging time and mA current calculator | Convert to units measures.
basics of calculating charging time is given on this site.

it will be the same for 2 or 4 cells. the charging current to the batteries is same on all the slots.

i have a energizer and camelion chager that charges at 250ma x4.if u wan't it to charge at 3hrs it gives close to 1a.
also have a sony charger it takes 7hrs to 8hrs charge a 2500mah batteries at 400mah x2

Originally Posted by Spectre

Thanks 6pack and Emil

If i divide 2500 / 70 ~ 35
Will it be the same for 2 batteries and 4 batteries together

or 4 batteries charged together - would need 2* 35 = 70 hours to get them fully charged

From the specification given in the link, it is clear that each pair of cells is placed in series for charging. It is also clear that each pair gets 70 mA when charging 4 cells simultaneously.
However, what happens when just one pair is charged is not specified in this link. It is most likely that the charging current will remain 70 mA from the way the spec is written.
Having said that I must also state that for most battery chargers, the charging current while charging 2 cells is higher than while charging 4. There is no way to know for sure from the sketchy specs provided. Maybe the Uniross site may have a more detailed spec.
One word of caution. When a pair of cells is charged by placing them in series, it is essential that both cells should be in nearly equal state of initial charge. If this is not the case, you'll end up either having one cell not charged enough or the other one screwed by overcharge or both events.

Thanks once again guys, really appreciate all the help

one more query, when a battery gets ful charged, will it stop charging or is there something like overcharging which can happen and damage the batteries

I am yet to see any cutoff light on it, so i am circumspect when to turn off the charge
Now I have the calculation in place, i can use that, but want to know on overcharging

The thread is going technical!!!!

I don't understand the details,,,,,

Originally Posted by Spectre

Thanks once again guys, really appreciate all the help

one more query, when a battery gets ful charged, will it stop charging or is there something like overcharging which can happen and damage the batteries

I am yet to see any cutoff light on it, so i am circumspect when to turn off the charge
Now I have the calculation in place, i can use that, but want to know on overcharging

well the chargers i have, change to trickle charging when the batteries get fully charged. chargers which dont have this check will continue charging and will most probably overcharge leading to low life of batteries. also the batteries will feel too hot to touch when overcharged.

I bought the Sony Green Cycle Energy 2500mAh 4XAA battery / charger kit a couple of days back and according to the specs on the manual, it takes approx 7 hrs to charge the 4 AA batteries with the provided charger.

Originally Posted by Spectre

Thanks once again guys, really appreciate all the help

one more query, when a battery gets ful charged, will it stop charging or is there something like overcharging which can happen and damage the batteries

I am yet to see any cutoff light on it, so i am circumspect when to turn off the charge
Now I have the calculation in place, i can use that, but want to know on overcharging

I can't speak specifically for the charger you have but this is applicable in general. Most chargers, even the cheap ones from a company will not normally overcharge a battery even if you leave it plugged in after full charge.
There are different methods to detect end-of-charge, some highly sophisticated, others very simple but reasonably effective. It is highly unlikely that your charger has the capacity to damage a battery since the normal charging current itself is just 70 mA. My guess is that your charger will barely warm up the cells during charge.
As I mentioned earlier, one possible way to damage a cell by overcharge in your case is if you try charging a pair of cells of which one is nearly empty and the other almost fully charged.
The other off course is to put a or both cell in reverse.
One more possibility is charging at high ambient temperature.