6 Volt NIMH
04-28-2008, 09:48 PM
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6 Volt NIMH
I am using dual receiver batteries with a new charger that I am not that familiar with , my question is at what voltage is a 6 volt NIMH considered fully charged? I am showing 7.11 volts with no load, and they are not warm as per NOBS at least 10 degrees above ambient. Any help would be greatly appreciated. Thanks Joey!!!!!!!!!!!!
04-28-2008, 10:24 PM
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RE: 6 Volt NIMH
How long did you charge them? What mah are you charging them at? Did you do form charge as Nobs rec? I bought their plug in wall charger that charges at .150 mah for 20 hours as suggested for 1950 mah 5 cell. Then discharged as suggested to .8v per cell and I too am getting 7.1 to 7.3 v. Here are some Nobs FAQ'S
A: Most programmable charger/cyclers allow programming the discharge current and the low voltage cutoff level for the discharge. If using a 250-300ma (.3) discharge rate set the cutoff voltage value at 1.0v per cell. If using a 500ma (.5) discharge rate set it at .8v per cell. For formation charge/discharge routines on Rx and Tx packs we don't recommend using a discharge rate higher than 500ma (.5) and DON'T discharge under any circumstances below .8v per cell !! Packs with cell impedance ratings below 10 mOhms CAN de discharged at 1.0 amps AFTER going through the formation process.. BUT NOT BEFORE.
Q: What’s ‘cycling’ and why do I need to do it?
A: Battery ‘cycling’ in it’s simple form is the two step process of charging and then discharging the battery under controlled conditions. Normally the purpose of the procedure is to ‘condition’ or ‘format’ a new pack or to verify the capacity or check the condition of a pack that’s been in service. ‘Routine’ cycling, or discharging before recharging a pack after every use is not necessary for either NiMH or Nicad packs, and discharging to ‘zero’ voltage under load is in fact harmful. A ‘cycler’ or controlled discharger will limit the discharge voltage level to prevent damage to the pack, whereas ‘leaving the switch on’ in your radio system to discharge a pack is very poor practice and may result in damage your radio system components or the battery.
Q: How do I know if my pack is fully charged?
Temeprature is the key.. always, always, always! IF THE PACK AIN'T WARM AT THE END OF THE CHARGE ROUTINE, IT AIN'T CHARGED! Note I said 'warm'. Not HOT! Hot is NEVER GOOD at the end of the charge routine.. but warm is OK. If using a temp probe, set it for 10 degrees above AMBIENT. If it's a peak controlled charger and the charger shuts down before the pack is slightly warm to the touch.. IT AIN'T FULLY CHARGED. If it's a timer controlled charger and at the end of the charge period the pack is not warm.. it's NOT fully charged yet! By far and away the biggest reason for low capacity numbers is undercharging.. if you have a 5 gallon pail with only 3 gallons in it, your only gonna get 3 gallons out of it. Engage your brain.. check temperature at the end of the charge routine!
Q: Temeprature?? I thought voltage was how you could tell the pack was charged??
A: More packs have been fried by guys looking for a 'number' instead of temperature on a charger than any other cause of premature battery failure. The 'finish' voltage of a pack will vary under an astounding number of variables.. but temperature rise ALWAYS signals that the cells are charged in a slow charge routine. Why? Because when the cells can no longer absorb the energy being shoved at them by the charger, they begin to give the unstored energy off as heat.
Taking the Temperature story to the next level.. fast charging. Here we can generate even more heat. Some high-impedance cells like AA NiMH's can get warm when being charged at 'normal' 1C (fast) or even 10% (slow) rates. They can get warm BEFORE they get to full charge. Why? Because high-impedance cells don't absorb energy as efficiently at high current levels.. just like they don't give up energy efficiently at higher discharge rates. So.. before you crank up the current on your charger on your new NiMH Tx pack.. check the pack label on our packs.. and set the charge rate recomended which is often LESS than the 'industry standard' for NiMH cells.
Final word on temperature: Aside from being a key indicator for correct charge time, rate and final charge condition bear in mind that heat is the bitter enemy of NiMH Cells. Drive the pack into thermal overload (hot) on the charger and it's likely you'll ruin it. Pay attention to the temeprature "Per NObs"
I spent 20 bucks a piece for these wall charger of Nobs And so far I have not needed to quick charge. I fly until at or below 6.0 not below 5.8 and put it on the wall charger for 15 hours they get a little warm and done.
A: Most programmable charger/cyclers allow programming the discharge current and the low voltage cutoff level for the discharge. If using a 250-300ma (.3) discharge rate set the cutoff voltage value at 1.0v per cell. If using a 500ma (.5) discharge rate set it at .8v per cell. For formation charge/discharge routines on Rx and Tx packs we don't recommend using a discharge rate higher than 500ma (.5) and DON'T discharge under any circumstances below .8v per cell !! Packs with cell impedance ratings below 10 mOhms CAN de discharged at 1.0 amps AFTER going through the formation process.. BUT NOT BEFORE.
Q: What’s ‘cycling’ and why do I need to do it?
A: Battery ‘cycling’ in it’s simple form is the two step process of charging and then discharging the battery under controlled conditions. Normally the purpose of the procedure is to ‘condition’ or ‘format’ a new pack or to verify the capacity or check the condition of a pack that’s been in service. ‘Routine’ cycling, or discharging before recharging a pack after every use is not necessary for either NiMH or Nicad packs, and discharging to ‘zero’ voltage under load is in fact harmful. A ‘cycler’ or controlled discharger will limit the discharge voltage level to prevent damage to the pack, whereas ‘leaving the switch on’ in your radio system to discharge a pack is very poor practice and may result in damage your radio system components or the battery.
Q: How do I know if my pack is fully charged?
Temeprature is the key.. always, always, always! IF THE PACK AIN'T WARM AT THE END OF THE CHARGE ROUTINE, IT AIN'T CHARGED! Note I said 'warm'. Not HOT! Hot is NEVER GOOD at the end of the charge routine.. but warm is OK. If using a temp probe, set it for 10 degrees above AMBIENT. If it's a peak controlled charger and the charger shuts down before the pack is slightly warm to the touch.. IT AIN'T FULLY CHARGED. If it's a timer controlled charger and at the end of the charge period the pack is not warm.. it's NOT fully charged yet! By far and away the biggest reason for low capacity numbers is undercharging.. if you have a 5 gallon pail with only 3 gallons in it, your only gonna get 3 gallons out of it. Engage your brain.. check temperature at the end of the charge routine!
Q: Temeprature?? I thought voltage was how you could tell the pack was charged??
A: More packs have been fried by guys looking for a 'number' instead of temperature on a charger than any other cause of premature battery failure. The 'finish' voltage of a pack will vary under an astounding number of variables.. but temperature rise ALWAYS signals that the cells are charged in a slow charge routine. Why? Because when the cells can no longer absorb the energy being shoved at them by the charger, they begin to give the unstored energy off as heat.
Taking the Temperature story to the next level.. fast charging. Here we can generate even more heat. Some high-impedance cells like AA NiMH's can get warm when being charged at 'normal' 1C (fast) or even 10% (slow) rates. They can get warm BEFORE they get to full charge. Why? Because high-impedance cells don't absorb energy as efficiently at high current levels.. just like they don't give up energy efficiently at higher discharge rates. So.. before you crank up the current on your charger on your new NiMH Tx pack.. check the pack label on our packs.. and set the charge rate recomended which is often LESS than the 'industry standard' for NiMH cells.
Final word on temperature: Aside from being a key indicator for correct charge time, rate and final charge condition bear in mind that heat is the bitter enemy of NiMH Cells. Drive the pack into thermal overload (hot) on the charger and it's likely you'll ruin it. Pay attention to the temeprature "Per NObs"
I spent 20 bucks a piece for these wall charger of Nobs And so far I have not needed to quick charge. I fly until at or below 6.0 not below 5.8 and put it on the wall charger for 15 hours they get a little warm and done.
04-29-2008, 08:36 AM
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RE: 6 Volt NIMH
Checking temp before its installed is fine, but how do you check after its wrapped & installed? I noticed my Nimh packs get just a little warm after a 20-24 hour 125 mah charge, my readings under 1000mah load is usually 7-7.2V. I noticed that the voltage drop under that load can be almost .5V. My biggest problem with Nimh is the V drop when you are fully charged the night before you go flying. The next AM, the readings are lower, down to 6.4V.(under load) I used to think Nimh were way more safe than Li-po's, but a friend of mine just exploded a transmitter pack by over charging them, it wasnt the smartest thing to do, he quick charges them at 500mah, then after cut off, he hit them again with 1000mah quick charge. I guess he didnt understand what a topping charge is??!!
