Charging rates?
03-23-2012, 02:07 PM
#1
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Charging rates?
ok guys, I'm new to the battery stuff so talk SLOW! I currently have a simple plug and play Traxxas charger for my nihm batteries. I just bought a Hitec X4 and it's on the way. I've been reading online about it and it seems there's a lot I need to know just to charge a battery. Right now I have a 7.2v 3800 mah, 7.2v 3000mah, 8.4v 3000 mah, and a 8.4v 3300 mah. Reading about this charger it seems like I need a quick education about discharge rates, a "c" rate, not sure what that is. How long to charge, what amperage to charge? ???? I know nitro but this battery thing sounded simple until I bought this charger. Also I know lipo's are better but right now the electric's are my kids and I'm trying to keep the speed down. Any keep it simple info would be greatly appreciated. Thanks
03-23-2012, 02:16 PM
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RE: Charging rates?
You probably don't need to know any of that except what rate to charge the packs. That rate is totally up to you and could be any rate that is within that chargers range. The higher the number the faster it charges.
03-24-2012, 01:10 AM
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RE: Charging rates?
If a pack is 2000mah (2amp hour) with a C rating of 2 (2C) then the max charge rate would be 2C x 2amps= 4amps. A 3000mah 3c pack could handle a charge rate of.....9amps. By definition the C rating is how long it will take to charge (assuming 100% efficiency). So 1C takes an hour, 2c half an hour, 4c 15minutes etc.
I think the hitec has 50watts per output. Watts = volts x amps. So the highest amps it can put out on for a 7.2v battery would be (50watts/7.2volt) about 7amps. You should be fine but be aware you wond be able to charge a 7000mah 7.2 volt battery faster than 1c even if it is rated higher.
Regards nimh 1c is fine but if not in a hurry use .7c as kinder on battery. Nicd can be higher than 1c check particular manufacturer but I would stick to 1c and only fast charge ?2c if in a hurry ( nice day, kids crying etc!!!)
All the best
03-24-2012, 05:58 AM
#4
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RE: Charging rates?
ORIGINAL: Goldenduff
If a pack is 2000mah (2amp hour) with a C rating of 2 (2C) then the max charge rate would be 2C x 2amps= 4amps. A 3000mah 3c pack could handle a charge rate of.....9amps. By definition the C rating is how long it will take to charge (assuming 100% efficiency). So 1C takes an hour, 2c half an hour, 4c 15minutes etc.
If a pack is 2000mah (2amp hour) with a C rating of 2 (2C) then the max charge rate would be 2C x 2amps= 4amps. A 3000mah 3c pack could handle a charge rate of.....9amps. By definition the C rating is how long it will take to charge (assuming 100% efficiency). So 1C takes an hour, 2c half an hour, 4c 15minutes etc.
I think the hitec has 50watts per output. Watts = volts x amps. So the highest amps it can put out on for a 7.2v battery would be (50watts/7.2volt) about 7amps. You should be fine but be aware you wond be able to charge a 7000mah 7.2 volt battery faster than 1c even if it is rated higher.
Regards nimh 1c is fine but if not in a hurry use .7c as kinder on battery. Nicd can be higher than 1c check particular manufacturer but I would stick to 1c and only fast charge ?2c if in a hurry ( nice day, kids crying etc!!!)
All the best
03-24-2012, 08:09 AM
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RE: Charging rates?
No worries, it's not too difficult. But you're right a lot of info.
For now charge nimh at .8c that is multiply the capacity (say 2200mah) by .8. Then divide by 1000 to change mah to amps. Set charge amps at that number.
Charge Nicd at 1c. Maybe even 2. So a 2200mah could be charged at 2.2-4.4amps.
Lipos tend to be about 5c and are way lighter.
Good luck
03-25-2012, 06:11 AM
#6
Thread Starter
RE: Charging rates?
ORIGINAL: Goldenduff
No worries, it's not too difficult. But you're right a lot of info.
No worries, it's not too difficult. But you're right a lot of info.
For now charge nimh at .8c that is multiply the capacity (say 2200mah) by .8. Then divide by 1000 to change mah to amps. Set charge amps at that number.
Charge Nicd at 1c. Maybe even 2. So a 2200mah could be charged at 2.2-4.4amps.
Lipos tend to be about 5c and are way lighter.
Good luck
03-26-2012, 09:41 AM
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RE: Charging rates?
ORIGINAL: Goldenduff
There is a danger of charging too slow. 0.8 is safe for all batteries.
There is a danger of charging too slow. 0.8 is safe for all batteries.
Wow really no wonder he is confused.
The best is overnite at C/10 exp. 3800mAH /10 charge at 400 mA this is form charge puts all batteries equal
disavantage 12 hr charge an can not do peak detection cut off.
that is where the 0.8C comes from, most peak detection chargers need .8 to 1.5C charge rate to work comes in at about 8mV to 12mV per cell. See the problem is any charge rate over about 0.5C if forgotten about "left on "will over charge a ruin batteries so they use peak detection to stop charger then as a stafty some will monitor the temperature etc etc.. it story goes on an on. This is why you don't get a a straight answer. [
]I like 0.8 C myself an set at 8mV on NiMH use 10mV on NiCAD , favorite is zero peak @ 0.5C an then trickle at /10C until i get to it.
Rich
03-26-2012, 10:12 AM
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RE: Charging rates?
ORIGINAL: Goldenduff
Now you've got me confused! You say .1C to start but then finish with .8c?!....
Now you've got me confused! You say .1C to start but then finish with .8c?!....
Rich
03-27-2012, 05:39 PM
#12
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RE: Charging rates?
Ok, you two have my head spinning now. I've charged two different ways so far. The first time I programmed it with Goldenduffs example. I set up a 3000 mah 8.4v pack at 2.2 amps as the charging rate. It seems on the Hitec there are a few different ways to charge. I set it up as an auto nihm charge at 2.2 amps with peak detection. The battery took about 100 minutes to charge, that is where you could see the volts begin to drop off and trigger the peak detection which ended the cycle and displayed full. All the time I had been checking the pack for heat. As the pack reached 10.15v it was still only warm. As the last 10-15 minutes finished the charge, I walked away. When I came back, the display read full at approx.10.18v and the pack was hot. Definately hot and not just warm. So the next time I charged a 8.4v 3300 mah pack at 2.4 amps set for 3300 capacity shutoff. The pack charged, reached approx 10.12v and was only warm, but the display never read full since I had the capacity cutoff set at 3300 mah. Any opinions on my settings? Still figuring out the many different settings of this charger. Thanks.
03-27-2012, 06:57 PM
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RE: Charging rates?
The second time didn't quite reach full because of your capacity setting. The capacity setting is just a failsafe and should be set at slightly higher than the highest capacity that a certain pack will ever get to. The charge rate is up to you and depends on how fast you desire to charge. "auto" on most chargers allows the charger to adjust the rate automatically. Any volt readings are irrelevant.
03-28-2012, 02:53 AM
#14
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RE: Charging rates?
ORIGINAL: guver
The second time didn't quite reach full because of your capacity setting. The capacity setting is just a failsafe and should be set at slightly higher than the highest capacity that a certain pack will ever get to. The charge rate is up to you and depends on how fast you desire to charge. "auto" on most chargers allows the charger to adjust the rate automatically. Any volt readings are irrelevant.
The second time didn't quite reach full because of your capacity setting. The capacity setting is just a failsafe and should be set at slightly higher than the highest capacity that a certain pack will ever get to. The charge rate is up to you and depends on how fast you desire to charge. "auto" on most chargers allows the charger to adjust the rate automatically. Any volt readings are irrelevant.
03-28-2012, 08:25 AM
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RE: Charging rates?
Capacity about 130% is what i use so 3300mAH would be 4000mAH from a full discharged battery.
So if the peak detection missed you got a stafety valve trying to help. This peak mV value is just a trial and error most start with a low value an if false peak an under charges we bump up an try again, as battery gets older they false peak more. But if a to high a value then battery gets very warm on charge cycle. Just trial an error until it's just right. Then program that in an save.
So if the peak detection missed you got a stafety valve trying to help. This peak mV value is just a trial and error most start with a low value an if false peak an under charges we bump up an try again, as battery gets older they false peak more. But if a to high a value then battery gets very warm on charge cycle. Just trial an error until it's just right. Then program that in an save.
03-28-2012, 01:03 PM
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RE: Charging rates?
The very last part of the charge before peak detection happens is where the battery will heat up. As the cell gets full, the charge you are putting in is not really charging the battery, but is being wasted as heat (and can be bad for NiMH if they get too hot).
Setting a capacity cap is a good idea in case something is wrong with the peak-detection to prevent severe over-charging, but IMO it shouldn't be hit if other settings are properly set. I would set it at ~110% of the battery capacity as a general rule, so for a 4000mAh pack, I would set the cap at around 4400mAh. If you are putting quite a bit more charge in than the pack's rating, then the battery is either underrated (unusual), it was discharged too low, or the pack is getting hot at the end of the charge (due to the wasted charge being dissipated as heat).
Lowering the charge rate can help, but you might also look at the peak threshold value and lower it a little if you can. This value is how much the voltage will fall after it peaks before the battery is considered "full". Too high and the battery is being charged longer and getting hot for nothing as you've seen. Too low and the charger may false-peak (this is where it thinks it's done, but really isn't).
So, before you lower the charge rate, I would continue charging at ~0.8C (without any capacity cap) but decrease the peak threshold value by one step. If the battery is still hot at the end of the charge, then lower it another step. Eventually, you'll get the sweet spot where the battery is full at the end and it will be just warm.
Setting a capacity cap is a good idea in case something is wrong with the peak-detection to prevent severe over-charging, but IMO it shouldn't be hit if other settings are properly set. I would set it at ~110% of the battery capacity as a general rule, so for a 4000mAh pack, I would set the cap at around 4400mAh. If you are putting quite a bit more charge in than the pack's rating, then the battery is either underrated (unusual), it was discharged too low, or the pack is getting hot at the end of the charge (due to the wasted charge being dissipated as heat).
Lowering the charge rate can help, but you might also look at the peak threshold value and lower it a little if you can. This value is how much the voltage will fall after it peaks before the battery is considered "full". Too high and the battery is being charged longer and getting hot for nothing as you've seen. Too low and the charger may false-peak (this is where it thinks it's done, but really isn't).
So, before you lower the charge rate, I would continue charging at ~0.8C (without any capacity cap) but decrease the peak threshold value by one step. If the battery is still hot at the end of the charge, then lower it another step. Eventually, you'll get the sweet spot where the battery is full at the end and it will be just warm.
03-28-2012, 01:27 PM
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RE: Charging rates?
ORIGINAL: Dads like rc too
So what is a good example of slightly higher? Or is there a percentage I could use?
ORIGINAL: guver
The second time didn't quite reach full because of your capacity setting. The capacity setting is just a failsafe and should be set at slightly higher than the highest capacity that a certain pack will ever get to. The charge rate is up to you and depends on how fast you desire to charge. ''auto'' on most chargers allows the charger to adjust the rate automatically. Any volt readings are irrelevant.
The second time didn't quite reach full because of your capacity setting. The capacity setting is just a failsafe and should be set at slightly higher than the highest capacity that a certain pack will ever get to. The charge rate is up to you and depends on how fast you desire to charge. ''auto'' on most chargers allows the charger to adjust the rate automatically. Any volt readings are irrelevant.
03-28-2012, 07:23 PM
#18
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RE: Charging rates?
ORIGINAL: bgosselin
The very last part of the charge before peak detection happens is where the battery will heat up. As the cell gets full, the charge you are putting in is not really charging the battery, but is being wasted as heat (and can be bad for NiMH if they get too hot).
Setting a capacity cap is a good idea in case something is wrong with the peak-detection to prevent severe over-charging, but IMO it shouldn't be hit if other settings are properly set. I would set it at ~110% of the battery capacity as a general rule, so for a 4000mAh pack, I would set the cap at around 4400mAh. If you are putting quite a bit more charge in than the pack's rating, then the battery is either underrated (unusual), it was discharged too low, or the pack is getting hot at the end of the charge (due to the wasted charge being dissipated as heat).
Lowering the charge rate can help, but you might also look at the peak threshold value and lower it a little if you can. This value is how much the voltage will fall after it peaks before the battery is considered "full". Too high and the battery is being charged longer and getting hot for nothing as you've seen. Too low and the charger may false-peak (this is where it thinks it's done, but really isn't).
So, before you lower the charge rate, I would continue charging at ~0.8C (without any capacity cap) but decrease the peak threshold value by one step. If the battery is still hot at the end of the charge, then lower it another step. Eventually, you'll get the sweet spot where the battery is full at the end and it will be just warm.
The very last part of the charge before peak detection happens is where the battery will heat up. As the cell gets full, the charge you are putting in is not really charging the battery, but is being wasted as heat (and can be bad for NiMH if they get too hot).
Setting a capacity cap is a good idea in case something is wrong with the peak-detection to prevent severe over-charging, but IMO it shouldn't be hit if other settings are properly set. I would set it at ~110% of the battery capacity as a general rule, so for a 4000mAh pack, I would set the cap at around 4400mAh. If you are putting quite a bit more charge in than the pack's rating, then the battery is either underrated (unusual), it was discharged too low, or the pack is getting hot at the end of the charge (due to the wasted charge being dissipated as heat).
Lowering the charge rate can help, but you might also look at the peak threshold value and lower it a little if you can. This value is how much the voltage will fall after it peaks before the battery is considered "full". Too high and the battery is being charged longer and getting hot for nothing as you've seen. Too low and the charger may false-peak (this is where it thinks it's done, but really isn't).
So, before you lower the charge rate, I would continue charging at ~0.8C (without any capacity cap) but decrease the peak threshold value by one step. If the battery is still hot at the end of the charge, then lower it another step. Eventually, you'll get the sweet spot where the battery is full at the end and it will be just warm.
