Genuinely Interested Again

[Robin K4IDC]

I've always had a fascination with renewable energy. In the early 90's I had a small PV array on a Red Rock tracker. I was an avid reader of Home Power Magazine. I used the battery energy to power pumps and the stirrer (trolling motor) in my homemade biodiesel shop. We moved and I lost my shop in the move; no such facilities at the new place. Diesel fuel prices dropped, veg oil became difficult to acquire so I hung up the biodiesel activities.
Now I'm working on a VHF/UHF amateur radio propagation beacon system to be placed atop a nearby mountain. I want to power the beacons via solar energy. I recently acquired a 1.5kw 6 panel array. I"m inclined to use a LiFePh04 battery, so I'm learning about those batteries, BMS & chargers.

 

[Geokilroy]

I've always had a fascination with renewable energy. In the early 90's I had a small PV array on a Red Rock tracker. I was an avid reader of Home Power Magazine. I used the battery energy to power pumps and the stirrer (trolling motor) in my homemade biodiesel shop. We moved and I lost my shop in the move; no such facilities at the new place. Diesel fuel prices dropped, veg oil became difficult to acquire so I hung up the biodiesel activities.
Now I'm working on a VHF/UHF amateur radio propagation beacon system to be placed atop a nearby mountain. I want to power the beacons via solar energy. I recently acquired a 1.5kw 6 panel array. I"m inclined to use a LiFePh04 battery, so I'm learning about those batteries, BMS & chargers.

Building on mountain top remember to account for low temp requirements of battery power. I am in Las Vegas and the mountain tops here get quite cold with storms coming thru even at only 6000 ft. I worked on tv/phone repeaters in this area. Got trapped up there for a few hours because helo could not get to us due to weather. It gets cold fast with wind.

 

[JoeHam]

And the requirement is that you cannot charge LiFePO4 below freezing. Discharge yes, charge no.

You can have a BMS do low temperature charge cutoff automatically or you can warm the battery with a seedling pad or something like that.

Otherwise LiFePO4 is fantastic.

73,

W8JH

 

[Robin K4IDC]

Yes, both of you make valid points; thanks for the response.
Perspective/context is important...I'm in middle Tennessee; "mountain" has a different connotation. The peak I'm planning/hoping to utilize is only 1300' ASL. Regardless, we do have lows in the single digits during the winter and can have several sequential days at or below freezing. I'm relying on the BMS for the low temperature cutoff.
Thanks for the tip on the seedling pad...hadn't thought of that. Another friend suggested a couple of 100W incandescent light bulbs shining on the base of the battery box.
The first major step is for me to actually assemble the beacons on my test bench and measure the load. I can easily manage all the electrical/electronic operation of the beacons, however I'm considering making the package more useful by varying the output power in steps during the beacon sequence to give listeners the option of judging the performance of their receiving equipment. That can be easily accomplished by switching attenuators in/out but will require some automation from something like an Arduino, and that step will come to fruition more quickly if I can enlist some programming help. Presumably once that level of technology is employed, supervising the battery temperature & state of charge to manage the loads becomes fairly simple.
The transmitters will be on 6m, 2m, 1.25m & 70cm to start with. 23cm is in the consideration as well. This is going to be a fun project!

 

[ghostwriter66]

Yes, both of you make valid points; thanks for the response.
Perspective/context is important...I'm in middle Tennessee; "mountain" has a different connotation. The peak I'm planning/hoping to utilize is only 1300' ASL. Regardless, we do have lows in the single digits during the winter and can have several sequential days at or below freezing. I'm relying on the BMS for the low temperature cutoff.
Thanks for the tip on the seedling pad...hadn't thought of that. Another friend suggested a couple of 100W incandescent light bulbs shining on the base of the battery box.
The first major step is for me to actually assemble the beacons on my test bench and measure the load. I can easily manage all the electrical/electronic operation of the beacons, however I'm considering making the package more useful by varying the output power in steps during the beacon sequence to give listeners the option of judging the performance of their receiving equipment. That can be easily accomplished by switching attenuators in/out but will require some automation from something like an Arduino, and that step will come to fruition more quickly if I can enlist some programming help. Presumably once that level of technology is employed, supervising the battery temperature & state of charge to manage the loads becomes fairly simple.
The transmitters will be on 6m, 2m, 1.25m & 70cm to start with. 23cm is in the consideration as well. This is going to be a fun project!

Forget the 100W light stuff .... drop your battery box in a small Coleman plastic cooler -- drill holes and fill the inner walls and cooler top with that sealant foam (very poor man Yeti) that you get from HD for 5.00 a bottle ... .. THAT WILL KEEP THEM ABOVE FREEZING FOR SEVERAL DAYS USUALLY ... WITH THAT SAID - IF YOU ARE ON A MOUNTAIN ODDS ARE YOU ARE GOING TO GET WIND ... WE NORMALLY HAVE OUR BATTERIES BEING HEATED AT NIGHT BY WIND ENERGY ... sorry for the CAPS I just noticed ....

 

[Robin K4IDC]

Forget the 100W light stuff .... drop your battery box in a small Coleman plastic cooler -- drill holes and fill the inner walls and cooler top with that sealant foam (very poor man Yeti) that you get from HD for 5.00 a bottle ... .. THAT WILL KEEP THEM ABOVE FREEZING FOR SEVERAL DAYS USUALLY ... WITH THAT SAID - IF YOU ARE ON A MOUNTAIN ODDS ARE YOU ARE GOING TO GET WIND ... WE NORMALLY HAVE OUR BATTERIES BEING HEATED AT NIGHT BY WIND ENERGY ... sorry for the CAPS I just noticed ....

Yes, that's a good idea and I'll consider it. Adding wind power would be really cool as far as I'm concerned, and the short tower I'm planning to use would support a small wind genny. I think sizing the battery & PV array with significant overhead for the load is the ticket & then add wind power as a supplement would be superb. I bought some components years ago to build a 1kw wind genny but never did move forward with the project.

 

[Robin K4IDC]

Yes, that's a good idea and I'll consider it. Adding wind power would be really cool as far as I'm concerned, and the short tower I'm planning to use would support a small wind genny. I think sizing the battery & PV array with significant overhead for the load is the ticket & then add wind power as a supplement would be superb. I bought some components years ago to build a 1kw wind genny but never did move forward with the project.

Oh, and thanks for the tip on expanding foam...good idea worth considering.

 

[JoeHam]

I was going to suggest using a cooler but I see Ghostie beat me to it. EVEN IF SHE WAS YELLING !

Send me a message with the frequency when you get going on 6m. I can probably hit that in the summer from Ohio.

 

[Geokilroy]

Yes, that's a good idea and I'll consider it. Adding wind power would be really cool as far as I'm concerned, and the short tower I'm planning to use would support a small wind genny. I think sizing the battery & PV array with significant overhead for the load is the ticket & then add wind power as a supplement would be superb. I bought some components years ago to build a 1kw wind genny but never did move forward with the project.

Remember to check that your LiFePo4 battery actually has low temp cut off. Many claim they have it but only have high temp sensor. See Will's videos to see how many false claims are out there.