transmitter battery still holds v after revival
01-05-2022, 12:42 PM
#1
transmitter battery still holds v after revival
My futaba 72Mhz radio has the 3 cell lipo transmitter battery I installed , well I left it on accidently for over night and it was dead so I recharged it on a balance charger at a very low input and it came up to its natural state 12.4 volts and I have been using the radio for a month now . its holding 1.3 volts now is this OK
01-05-2022, 02:22 PM
#2
My futaba 72Mhz radio has the 3 cell lipo transmitter battery I installed , well I left it on accidently for over night and it was dead so I recharged it on a balance charger at a very low input and it came up to its natural state 12.4 volts and I have been using the radio for a month now . its holding 1.3 volts now is this OK
It's possible your Futaba transmitter isn't setup to use LiPo packs; otherwise, it would have a low voltage alarm / cutoff when the 3S LiPo pack reached about 9.5v (3.2v per cell). But it simply keeps going until the LiPo pack is dead. And, that may be because it is an older transmitter that is supposed to use a 8 cell NiCad / NiMH, not a 3S LiPo. That would mean that the TX is designed for a maximum voltage input of 10v, not a 3S LiPo voltage of 12.6v. If that's the case, the TX has been on borrowed time and it should have smoked when you first plugged in the 3S LiPo.
Assuming the TX is setup to use a 3S LiPo, it's clear that there is no low voltage alarm / cutoff.
I guess if you used the transmitter for 10 or 11 hours over a 30 day period, the 3S LiPo was doing okay. But, if you killed it twice already, I wouldn't trust it again.
Just so you know, the minimum voltage for a LiPo cell is 3.2v. That is the lowest it should go before irreversible damage occurs to the cell. In a 3S pack, that would be 9.5v. If there is no protection built into the TX, you need to stay on top of the battery's state of charge; otherwise, you are going to have this happen again.
Last edited by ticedoff8; 01-05-2022 at 02:28 PM.
01-06-2022, 02:36 AM
#3
minimum voltage drop to charge battery
If the 3S pack's output is 1.3v or each cell in the pack has a voltage of 1.3v (the pack's output is 3.9v), either are bad signs for the 3S LiPo pack.
It's possible your Futaba transmitter isn't setup to use LiPo packs; otherwise, it would have a low voltage alarm / cutoff when the 3S LiPo pack reached about 9.5v (3.2v per cell). But it simply keeps going until the LiPo pack is dead. And, that may be because it is an older transmitter that is supposed to use a 8 cell NiCad / NiMH, not a 3S LiPo. That would mean that the TX is designed for a maximum voltage input of 10v, not a 3S LiPo voltage of 12.6v. If that's the case, the TX has been on borrowed time and it should have smoked when you first plugged in the 3S LiPo.
Assuming the TX is setup to use a 3S LiPo, it's clear that there is no low voltage alarm / cutoff.
I guess if you used the transmitter for 10 or 11 hours over a 30 day period, the 3S LiPo was doing okay. But, if you killed it twice already, I wouldn't trust it again.
Just so you know, the minimum voltage for a LiPo cell is 3.2v. That is the lowest it should go before irreversible damage occurs to the cell. In a 3S pack, that would be 9.5v. If there is no protection built into the TX, you need to stay on top of the battery's state of charge; otherwise, you are going to have this happen again.
It's possible your Futaba transmitter isn't setup to use LiPo packs; otherwise, it would have a low voltage alarm / cutoff when the 3S LiPo pack reached about 9.5v (3.2v per cell). But it simply keeps going until the LiPo pack is dead. And, that may be because it is an older transmitter that is supposed to use a 8 cell NiCad / NiMH, not a 3S LiPo. That would mean that the TX is designed for a maximum voltage input of 10v, not a 3S LiPo voltage of 12.6v. If that's the case, the TX has been on borrowed time and it should have smoked when you first plugged in the 3S LiPo.
Assuming the TX is setup to use a 3S LiPo, it's clear that there is no low voltage alarm / cutoff.
I guess if you used the transmitter for 10 or 11 hours over a 30 day period, the 3S LiPo was doing okay. But, if you killed it twice already, I wouldn't trust it again.
Just so you know, the minimum voltage for a LiPo cell is 3.2v. That is the lowest it should go before irreversible damage occurs to the cell. In a 3S pack, that would be 9.5v. If there is no protection built into the TX, you need to stay on top of the battery's state of charge; otherwise, you are going to have this happen again.
Typhoon acrobatic can hover good
01-06-2022, 09:32 AM
#5
Are you really using LiPO batteries, or are they really LiFE? 3s LiPo's can be as high as 14.4 volts right off the charger, and run around 11.1 v for most of their output. LiFE's stay very consistently at around 9.9 volts.
Being as you noted it was a 72mHz transmitter, it almost surely was designed originally to take 9.6 v nicads. While it will have a range of tolerance for higher voltages, going excessively over by using LiPO's can greatly reduce its life. Best to a) verify that it is actually built to accept 3s LiPO's (unlikely) or b) switch to a 3s LiFE pack. Not doing so will result in early failure. If going to LiFE, make sure your charger has a specific profile for them. It can be very bad to just use the LiPO charge function on them.
Being as you noted it was a 72mHz transmitter, it almost surely was designed originally to take 9.6 v nicads. While it will have a range of tolerance for higher voltages, going excessively over by using LiPO's can greatly reduce its life. Best to a) verify that it is actually built to accept 3s LiPO's (unlikely) or b) switch to a 3s LiFE pack. Not doing so will result in early failure. If going to LiFE, make sure your charger has a specific profile for them. It can be very bad to just use the LiPO charge function on them.
01-06-2022, 09:33 AM
#6
A LiPo cell is 100% charged at 4.2v.
So a 3-cell pack (3S) would be 12.6v at 100%, not 13v.
I've never had a 3S LiPo that charged to over 12.6 volts "right off the charger".
All "smart chargers" use 4.2v per cell as their default maximum. To charge the cells to something higher than 4.2v would require going through the menus in the charger, and changing the maximum voltage from 4.2 to 4.33 (for 13v) or 4.8v (for 14.4).
If a charger charged the cells to 4.33v (13v), it may not explode, but it would be warm to the touch and possibly starting to puff. And, doing this routinely would shorten its life considerably.
But, charging a 3S LiPo to 14.4 (4.8v per cell) would be scary. No one does that.
When LiPo batteries started being used regularly in RC, we quickly learned not to over-charge LiPo or the would catch fire.
So a 3-cell pack (3S) would be 12.6v at 100%, not 13v.
3s LiPo's can be as high as 14.4 volts right off the charger, and run around 11.1 v for most of their output
I've never had a 3S LiPo that charged to over 12.6 volts "right off the charger".
All "smart chargers" use 4.2v per cell as their default maximum. To charge the cells to something higher than 4.2v would require going through the menus in the charger, and changing the maximum voltage from 4.2 to 4.33 (for 13v) or 4.8v (for 14.4).
If a charger charged the cells to 4.33v (13v), it may not explode, but it would be warm to the touch and possibly starting to puff. And, doing this routinely would shorten its life considerably.
But, charging a 3S LiPo to 14.4 (4.8v per cell) would be scary. No one does that.
When LiPo batteries started being used regularly in RC, we quickly learned not to over-charge LiPo or the would catch fire.
Last edited by ticedoff8; 01-06-2022 at 09:41 AM.
01-06-2022, 01:44 PM
#7
A LiPo cell is 100% charged at 4.2v.
So a 3-cell pack (3S) would be 12.6v at 100%, not 13v.
I've never had a 3S LiPo that charged to over 12.6 volts "right off the charger".
All "smart chargers" use 4.2v per cell as their default maximum. To charge the cells to something higher than 4.2v would require going through the menus in the charger, and changing the maximum voltage from 4.2 to 4.33 (for 13v) or 4.8v (for 14.4).
If a charger charged the cells to 4.33v (13v), it may not explode, but it would be warm to the touch and possibly starting to puff. And, doing this routinely would shorten its life considerably.
But, charging a 3S LiPo to 14.4 (4.8v per cell) would be scary. No one does that.
When LiPo batteries started being used regularly in RC, we quickly learned not to over-charge LiPo or the would catch fire.
So a 3-cell pack (3S) would be 12.6v at 100%, not 13v.
I've never had a 3S LiPo that charged to over 12.6 volts "right off the charger".
All "smart chargers" use 4.2v per cell as their default maximum. To charge the cells to something higher than 4.2v would require going through the menus in the charger, and changing the maximum voltage from 4.2 to 4.33 (for 13v) or 4.8v (for 14.4).
If a charger charged the cells to 4.33v (13v), it may not explode, but it would be warm to the touch and possibly starting to puff. And, doing this routinely would shorten its life considerably.
But, charging a 3S LiPo to 14.4 (4.8v per cell) would be scary. No one does that.
When LiPo batteries started being used regularly in RC, we quickly learned not to over-charge LiPo or the would catch fire.
01-07-2022, 11:24 AM
#8
Like I said in my 1st reply:
And, that may be because it is an older transmitter that is supposed to use a 8 cell NiCad / NiMH, not a 3S LiPo. That would mean that the TX is designed for a maximum voltage input of 10v, not a 3S LiPo voltage of 12.6v. If that's the case, the TX has been on borrowed time and it should have smoked when you first plugged in the 3S LiPo.
01-10-2022, 08:29 AM
#9
Just my personal opinion, but using a battery you "wonder if it's good" in your transmitter is just asking for a crash. What are you going to do when it quits while you're 200 feet up and lose contact with your plane?
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init4fun (01-10-2022)
