not sure if my chargers are up to it
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OldNick
Newly Enlightened
To answer your question:
It's probably worth sorting out the mAH thingies! <G>
There are chargers out there now that are far more fast, sophisticated and programmable than what you have. They don't cost much more than a set of cells (batteries) and usually come _with_ a set anyway.
From the pictures I can't be sure exactly how the thing is set up to take cells, but:
The trouble with timed chargers is that they take no account of the state of charge of the cell(s). They can overcharge. At 190 mA....I would not be happy leaving a half-charged cell in there for the full 15 hours. I doubt it would do anything drastic, but may lower the number of recharges.
Your charger might _juuuuust_ make it with a completely flat cell, if it fact puts out 190 mA in that second picture. It says 170-190, and I do not know what decides that. If it's less than 190 mA, then the charger will definitely not charge your cells.
- 190 mA * 15 hours (timed charge)= 2850 mAH put into the cell.
- 2500 mAH cell capacity * 1.2 (charge deficit: see below)= 3000 maH
So really it will struggle to properly fill the cell(s). It will take a long time to charge more than 2. After you have done a timed charge, I would top the cell(s) up using that even lower current mentioned in the second picture (if you can choose), which should not do any damage if you leave it too long, because it's so low.
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milliAmps (mA) are current. For a given voltage, the more mA the more power is delivered.
milliAmpHours mAH, are just that. The capacity of a cell in mAH is the (CLAIMED) number of hours that it will take to drain the cell at 1mA, from fully-charged to the point where it's not good to drain the cell without recharging. It's a very slippery figure.
Usually this is not useful, because we use more than 1 mA in most uses, and 1 mA is probably less than the cell will lose just sitting there! So if the current is 100 mA, the number of hours would be 2500 / 100 = 25 hours of continuous use. 1 Amp = 1000mA. So if you use 1 Amp you get 2.5 hours use.
In the other direction, you need to charge the cell, and you can get some idea of how long it will take at a given current by exactly the same method. However, it takes maybe 20% more energy to "push the charge back in" than the cell will give you when fully charged. This is what I called the "charge deficit" above. That's just my choice of term.
Nick
It's probably worth sorting out the mAH thingies! <G>
There are chargers out there now that are far more fast, sophisticated and programmable than what you have. They don't cost much more than a set of cells (batteries) and usually come _with_ a set anyway.
From the pictures I can't be sure exactly how the thing is set up to take cells, but:
The trouble with timed chargers is that they take no account of the state of charge of the cell(s). They can overcharge. At 190 mA....I would not be happy leaving a half-charged cell in there for the full 15 hours. I doubt it would do anything drastic, but may lower the number of recharges.
Your charger might _juuuuust_ make it with a completely flat cell, if it fact puts out 190 mA in that second picture. It says 170-190, and I do not know what decides that. If it's less than 190 mA, then the charger will definitely not charge your cells.
- 190 mA * 15 hours (timed charge)= 2850 mAH put into the cell.
- 2500 mAH cell capacity * 1.2 (charge deficit: see below)= 3000 maH
So really it will struggle to properly fill the cell(s). It will take a long time to charge more than 2. After you have done a timed charge, I would top the cell(s) up using that even lower current mentioned in the second picture (if you can choose), which should not do any damage if you leave it too long, because it's so low.
************************************************
milliAmps (mA) are current. For a given voltage, the more mA the more power is delivered.
milliAmpHours mAH, are just that. The capacity of a cell in mAH is the (CLAIMED) number of hours that it will take to drain the cell at 1mA, from fully-charged to the point where it's not good to drain the cell without recharging. It's a very slippery figure.
Usually this is not useful, because we use more than 1 mA in most uses, and 1 mA is probably less than the cell will lose just sitting there! So if the current is 100 mA, the number of hours would be 2500 / 100 = 25 hours of continuous use. 1 Amp = 1000mA. So if you use 1 Amp you get 2.5 hours use.
In the other direction, you need to charge the cell, and you can get some idea of how long it will take at a given current by exactly the same method. However, it takes maybe 20% more energy to "push the charge back in" than the cell will give you when fully charged. This is what I called the "charge deficit" above. That's just my choice of term.
Nick
thanks for replyying and explaining
so does that mean it would takes 10 hours to fully charge my 2500mah batteries with my first picture and it doesn't charge more than that in one time?
the first picture is a 6 hours timed charger and the second is 15hours.
and i don't quite get what you mean by
it takes maybe 20% more energy to "push the charge back in" than the cell will give you when fully charged.
do you mean it would take 20% more to fully charged a cell?
is 15 hour charger better for the batteries?
so does that mean it would takes 10 hours to fully charge my 2500mah batteries with my first picture and it doesn't charge more than that in one time?
the first picture is a 6 hours timed charger and the second is 15hours.
and i don't quite get what you mean by
it takes maybe 20% more energy to "push the charge back in" than the cell will give you when fully charged.
do you mean it would take 20% more to fully charged a cell?
is 15 hour charger better for the batteries?
OldNick
Newly Enlightened
Sorry. I forgot to address the first charger. A bit more explanation may have helped, I have to say, but no biggy.
Yes it will take ten hours (well at least 12) art 250 mA. It may take more, as the current may well drop as the battery gets up to voltage. It depends on the current regulation of the charger. So if the charger is timed at 6 hours it would be worth trying two charges in a row. But that would only be on a really low cell.
I am not quite sure what you mean by "not more than that in one time".
There is an inefficiency in the charge and discharge of the cells. So yes, it will take 20% (or more) mAH to charge a cell than it will give back to get to its pre-charge state of charge. 20% is probably hopeful as well.
Both of those chargers are super-easy on the cells. It's only when you get to charging at one or two hour charges (known as C1 and C2) that you start have to worry very much about how critical your charger is. However anything faster than C10 means you do have to watch the setup. Hence your timer.
However, even the 190 mA one would worry me if left on an _overcharged_ cell, as I said. 70 mA or so is trickle and pretty safe IMO.
The only way I can think of to make these easily workable over a range of cell charges was with a temperature switch that you rigged up to cut the charger when the cells got warm/hot. Guys used to do that with fast chargers, before all the "smart" chargers came along.
I will tell you something. The 170-190 mA setting on the second charger is good for the the first time you charge cells out of the pack. They need a long, slow charge (overnight minimum). But you would have to cycle it twice to get a full 2500 mAH charge. If you really wanted to baby your cells you could run 4-5 runs across them with the 70mA setting <G>.
My honest opinion with these that in today's battery world they struggle to be one thing or the other. They do not quite charge the 2500mAH cells, and you cannot quite simply leave them to top up slowly, without having to change the cell placement/settings/connections (whichever is appropriate).
It depends what your usage will be. You are going to take a long time to charge. You _can_ work with a partly-charged cell that you charge on the 190 for 10 hours. I don't _think_ that would hurt the cells. That gives you a 1600 mAH cell or thereabouts. However, topping them up every now and then (10 charges) really slowly would be a good idea.
Nick
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