Techniques > Radios
Ultramat 17
haydenc:
All seems very quiet on the board so I will seek more advice.
I bought an Ultramat 17 Charger.
While the instructions come in many languages they don't seem to cover what I would call the basics.
What charging current should I use to charge an RX battery pack (4 AA batteries of 2100mAh.
The basic charger I had used up till this, slow charges at 120 mA.
My understanding, and I have been wrong before, is
2100/120 =17hrs 30mins.
Sums
So I would leave it on charge for 17 hrs 30 mins.
Now I have the ability to increase the charging current :lol:
2100/1000 or 1 amp = 2.1Hrs.
2100/2000 = 1 hr
This gadget will charge at up to 5amps :clap: :clap: :clap:
I didnt try that. just did the sums
2100/5000=0.42Hrs or 25mins :?:
What would be a safe charging current.
Or have I got it all wrong.
Many thanks in advance
Cha
DennisZ:
Hi Charlie,
my 2600 NiMH pack gets warm when charging at 600mA.
In general, it is safe to charge at 1C - that is 2amp for 2000mAh pack.
Happy Days:
Okay Cha,
It turns out that although your battery holds a total charge of 2100mA in reality if you took all that charge out of the battery the battery would have zero volts left in it, which wouldn't work you radio. So in real terms you should only discharge the battery down to about 80% of the total charge. (Otherwise the voltage will drop so low it won't work your gear. :cry: )
Therefore you shouldn't take much more than 80% of 2100mA = 1680 mA.
Turning to matters of charging,.................. the manufacturer will tell you that for max. life of the battery you shouldn't charge it at more than 10% of it's total capacity.
So, 10% of 2100mAh = charge current of 210mAh. (You with me?:?: )
If we assume that you've taken 1680 milliamps out of the battery it should take exactly 8 hours to recharge it. :D @210mAh (Don't fall asleep on me Cha, there's more to come.)
However,..................if you were stuck out on the slope with a dead (low) battery it could be charged at a rate of 2100mAh. (Known as 1C) This will slightly shorten the life of the battery but would get you flying again in 1 hour. :clap: Some people even charge at twice that rate to have thier model flying again in 30 mins. But this does tend to "cook" the battery a bit! (Shortening it's life even more)
There,............that didn't hurt did it! :wink:
Keith
haydenc:
:oops: :oops: :oops:
I knew it was too good to be true.
FOR SALE 1 SLIGHTLY COOKED 2100 NIMH RX PACK.
Well charged it at 1200mA till the machine said it was full.
Maybe I should of taken up growing vegetables
Thanks Dennis and Keith for the detailed explination.
Yes it does make sence.
Now that I know the -80% and + #### Oh wait a minute . That is -20% leaving 80%
Yea I think I have it now.
Instructions had said, or I read somewhere else, not to let the voltage on a single AA drop below 1 or 1.1V. Think that is the same thing.
1C :?: :?: :?: thats a new one.
Well I know where that fits now.
Once the CAPACITY.
Its all simple when its explained.
Right I will reset the values for charge and discharge.
WAIT
#-o
Should I discharge at 10% of capacity ????
Thanks again Lads[/b]
Cha[/b]
Happy Days:
Right,.............charge/discharge.........now your talking about 'cycling' the battery.
Hmmmmmmmmm How to explain this???????
Firstly let me tell you that you can discharge at a much higher rate than you charge. So on a 2100mA battery you could safely discharge at 1.5C,...say 3Amps.
Not sure what you do and don't know Cha. So I'll assume that you know nothing, like 'Manuel' in 'Faulty Towers' :lol:
With Nickle-Metal Hydride (Ni-MH) or the older Nickle-Cadmium (Ni - Cd) batteries they have a problem. If they are not fully discharged down to their safe minimum discharge level every so often they tend to "remember" the average discharge level that they've been used to and not hold as many amps as they should :x
Confused? :?:
Think of a bottle of milk :lol: No I'm not joking...think of a bottle of milk that has been emptied, but not rinsed out. The small amount of milk left in the bottle will "turn" after a few days and solidify.
Now supose it's re-filled with milk and then emptied again. (But not rinsed out) The small amount of liquid milk left in the bottle will also solidify.
If this cycle is repeated many times eventually the bottle will no longer hold as much liquid milk as it first did because the inside of the bottle is being filled with solidified milk.
This is an analogy of what happens in Ni-MH and Ni-Cd batteries.
The way to rid the battery of this "memory" (or residual milk) is to discharge the battery down to it's safe discharge state, (rinse the bottle out) and then fully recharge it. This is known as "Cycling" the battery.
So,...........if you just want to charge the battery, that's fine Cha. However it's a good idea every so often to Cycle the battery to get rid of it's memory effect and ensure that it holds all the charge (Amps) that it can.
I cycle my rx batteries about every 20 charges. Okay Cha,........CHA stop snoring!!!
K
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