| Author |
Message |
    
Charliebrown
Advanced Member
Username: Charliebrown
Post Number: 848
Registered: 10-2002
| | Posted on Monday, June 12, 2023 - 12:56 pm: | 
|
I AM CONSIDERING GOING INTO OFF GRID OPERATIONS IN THE WILDERNESS WITH MY HAM RADIO EQUIPMENT. WE HAVE THICK FOREST WHERE I LIVE AND I WAS WONDERING HOW LONG 12 VOLt CAR BATTERY WOULD LAST WITHOUT CHARGING OPERATING MY YAESU FT 7900 ON HIGH POWER BEFORE THE VOLTAGE WOULD DROP TO LOW THAT COULD DAMAGE THE RADIO? THE BATTERY IS 12V dc 900 CRANKING AMPS. |
Ke0koy
Member
Username: Ke0koy
Post Number: 62
Registered: 12-2018
| | Posted on Tuesday, June 13, 2023 - 8:26 pm: |
|
A 12v 900CCA battery will have around 90AH usable energy stored in it. Look for the AH rating on the battery, it means amp hours. Its the number of amps you can draw for an hour before the battery dies. If it is 90AH, it will die after pulling 90A for one hour, or 45A for 2 hours, or 10A for 9 hours etc. So if your radio requires 7A during transmit, you would have 90/7 hours of transmitting time.
But thats a dead battery. In reality, any lead-acid battery begins to sulfate when under 35% charge, so its best to not push it that far unless you like buying new batteries all the time. |
Charliebrown
Advanced Member
Username: Charliebrown
Post Number: 849
Registered: 10-2002
| | Posted on Wednesday, June 14, 2023 - 6:58 pm: |
|
Hello Brandon, My radio at high power most likely will draw about 20 to 25 amp. My biggest concern is the voltage drop. Here in the shop it does not take long for the 13.8 volts to drop to 11 volts. With the voltage drop that low my concern is damage to the radio. Solar Pannels is so expensive especially for that much amps to keep up with the radio amps. I thought several years ago that the people that did compention with cb radios had a device that would keep the voltage up. I have looked and I cannot find anything like that. A gasoline generator would be too noisy and cost too much gas to keep it running. Even if I have multiple car batteries it still would have the voltage to eventually drop. I guess my best bet would be to go solar. Thank you for the help Have a blessed Day. |
Ke0koy
Member
Username: Ke0koy
Post Number: 64
Registered: 12-2018
| | Posted on Thursday, June 15, 2023 - 10:38 pm: |
|
The device you speak of sounds like a boost converter. However, if you are asking the battery for more work after it is down to 11V, you are begging for the battery plates to be covered in sulfate and quit working. Sulfation is an issue for a dead battery because lead sulfate is less soluble in water than it is in sulfuric acid, and as the battery discharges, sulfuric acid is being converted to water and lead sulfate. There comes a point where the sulfate starts to precipitate out, and when the crystals grow larger, the ability of the increasingly weaker acid at "full" charge do dissolve them decreases. The crystals grow and reduce the effective surface area of the plates. This reduces the available current. And from the sound of it, that may have already happened to your battery. I suggest doing a test with a voltmeter and see what happens. There is what the numbers on a new battery say, then there is what an abused, sulfated and half dry battery can do. Also, if your FT7900 is pulling 20A, something serious is wrong with it. It should pull a max of 9A. |
Charliebrown
Advanced Member
Username: Charliebrown
Post Number: 850
Registered: 10-2002
| | Posted on Saturday, June 17, 2023 - 9:39 pm: |
|
My radio has a low voltage warning system. So I never let it get below 12v Thanks for the info That is good information for not only me but for everone |
|
