3pm safe receiver voltage
08-15-2008, 05:10 PM
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3pm safe receiver voltage
Hi,
I have a 3pm radio which I use in my gas boat. At what point should I charge up the receiver pack? I use a 5 cell 1500mh nicad pack. Using the Hobbico expanded meter my pack now reads 6.3v which is under the green and should be charged. I think that 6.3 is a good charge for a 6v pack but per the meter it should be carged. Do you agree with this or can I drop voltage low and still be safe. I use 1 1/4scale and one std servo.
Thanks
Brian
I have a 3pm radio which I use in my gas boat. At what point should I charge up the receiver pack? I use a 5 cell 1500mh nicad pack. Using the Hobbico expanded meter my pack now reads 6.3v which is under the green and should be charged. I think that 6.3 is a good charge for a 6v pack but per the meter it should be carged. Do you agree with this or can I drop voltage low and still be safe. I use 1 1/4scale and one std servo.
Thanks
Brian
08-15-2008, 06:26 PM
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RE: 3pm safe receiver voltage
Depends on the load used when measuring the voltage. And remember, all voltage tells you is that the pack is delivering voltage at that moment in time. It tells you nothing about what is "left" in the pack.
Having said that, I run my 5-cell NiMH packs down to 6.0 volts with a 1 amp load. For boats this has proven to be totally workable. Doing this I am usually at the 70% or so of capacity used for the pack.
And yes, I have a 3PM 2.4 FASST radio in gas boats running two digital servos. I use a Futaba 3152 on throttle and a Futaba 9156 on rudder.
I installed the Sanyo Enerloop NiMH cells in the TX. These cells hold their charge on the shelf much better than regular NiMH cells. Charge them up and after 6 months they still have 90% of their charge. The 2,000 mAh cells run my 3PM TX for about 14 hours. per charge. They are consumer type button top cells just like an alkaline cell.
Having said that, I run my 5-cell NiMH packs down to 6.0 volts with a 1 amp load. For boats this has proven to be totally workable. Doing this I am usually at the 70% or so of capacity used for the pack.
And yes, I have a 3PM 2.4 FASST radio in gas boats running two digital servos. I use a Futaba 3152 on throttle and a Futaba 9156 on rudder.
I installed the Sanyo Enerloop NiMH cells in the TX. These cells hold their charge on the shelf much better than regular NiMH cells. Charge them up and after 6 months they still have 90% of their charge. The 2,000 mAh cells run my 3PM TX for about 14 hours. per charge. They are consumer type button top cells just like an alkaline cell.
08-15-2008, 06:55 PM
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RE: 3pm safe receiver voltage
ORIGINAL: Silent-AV8R
Depends on the load used when measuring the voltage. And remember, all voltage tells you is that the pack is delivering voltage at that moment in time. It tells you nothing about what is "left" in the pack.
Having said that, I run my 5-cell NiMH packs down to 6.0 volts with a 1 amp load. For boats this has proven to be totally workable. Doing this I am usually at the 70% or so of capacity used for the pack.
And yes, I have a 3PM 2.4 FASST radio in gas boats running two digital servos. I use a Futaba 3152 on throttle and a Futaba 9156 on rudder.
I installed the Sanyo Enerloop NiMH cells in the TX. These cells hold their charge on the shelf much better than regular NiMH cells. Charge them up and after 6 months they still have 90% of their charge. The 2,000 mAh cells run my 3PM TX for about 14 hours. per charge. They are consumer type button top cells just like an alkaline cell.
Depends on the load used when measuring the voltage. And remember, all voltage tells you is that the pack is delivering voltage at that moment in time. It tells you nothing about what is "left" in the pack.
Having said that, I run my 5-cell NiMH packs down to 6.0 volts with a 1 amp load. For boats this has proven to be totally workable. Doing this I am usually at the 70% or so of capacity used for the pack.
And yes, I have a 3PM 2.4 FASST radio in gas boats running two digital servos. I use a Futaba 3152 on throttle and a Futaba 9156 on rudder.
I installed the Sanyo Enerloop NiMH cells in the TX. These cells hold their charge on the shelf much better than regular NiMH cells. Charge them up and after 6 months they still have 90% of their charge. The 2,000 mAh cells run my 3PM TX for about 14 hours. per charge. They are consumer type button top cells just like an alkaline cell.
Thanks for the reply. I don't know who makes the cells in my pack. I was just concerned at what the expaned volt meter considers good. The green section ends at 6.4 volts.
08-15-2008, 07:37 PM
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RE: 3pm safe receiver voltage
6.4 is pretty high if that is under load. I use a loaded voltmeter. I can measure with no load, 500 mA, 1,000 mA, and 1,500 mA loads An unloaded voltage is next to worthless.
FWIW, NiMH or NiCad cells are considered fully discharged at 0.9 volts per cell, or 4.5 volts for a 5 cell pack. But you never want to get near that voltage. I actually stop when the voltage first drops from 6 volts. 6 or higher I "GO". 5.99 or less is a "NO GO" .voltage for me.
Your meter looks like it uses a very low load (225 to 275 mA) to measure the packs.But for a 2 servo boat it is probably OK. In any case I would feel fine down to 6 volts.
FWIW, NiMH or NiCad cells are considered fully discharged at 0.9 volts per cell, or 4.5 volts for a 5 cell pack. But you never want to get near that voltage. I actually stop when the voltage first drops from 6 volts. 6 or higher I "GO". 5.99 or less is a "NO GO" .voltage for me.
Your meter looks like it uses a very low load (225 to 275 mA) to measure the packs.But for a 2 servo boat it is probably OK. In any case I would feel fine down to 6 volts.
08-16-2008, 12:45 AM
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RE: 3pm safe receiver voltage
for the added safety have you thought of using 2 x rx battery packs combined with 2 x switches ? this way if 1 x pack goes under or a switch should fail you still have others.
08-16-2008, 12:59 PM
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RE: 3pm safe receiver voltage
I have not thought about 2 packs. In a standard radiobox your lucky that you get in one pack. I think I keep voltage no less then about 5.8-6v and should be fine.
Thanks
Brian
Thanks
Brian
