Solar panel controller

Brian wrote on 12/30/2020 7:42 AM:
On Tuesday, December 29, 2020 at 8:42:19 AM UTC-7, krasw wrote:
Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.

I put a 10 Watt a panel on my HP16. It averaged 200-250ma charging a 12AH Lead Acid batteries. The real advantage was when I was flying contests or safaris where I left the plane tied down. I could fly about 3 days in a row without needing to charge the battery. If we had a rest day it would pretty much top off the battery. I didn’t use a charge controller, I just used a volt meter. Since I only left it tied down when I was flying almost daily I didn’t figure 200-250 was enough to hurt the battery. But if I didn’t fly for more than a day I would disconnect it.

I loved having the solar panel, most of the time I didn’t need to charge the battery when flying daily. I wish I could come up with a reasonable panel to install on my LS6.

IMO Unless you are leaving the plane outside for extended periods without flying almost daily, my opinion is you don’t need a charge controller for a 20 watt or less solar panel. An appropriately sized and heat sinked Zenor diode would prevent it from overcharging if you did inadvertently leave it connected. If it is connected only when flying then no controller is required.

Brian's solution is a good one for gliders with a low enough current drain. Like Moshe, I
struggled to find a good place to put a useful amount of solar panel on my glider, given the
1.5 amp draw while flying. I eventually gave up trying, and installed a 20 AH Life battery,
which is enough capacity for two long flights. Normally, I recharge it after each flight from a
30 AH "donor" battery which is charged during the day by a 40W solar panel on the trailer,
using a DC-DC charger for electric model hobbyists. That's easy enough, and reliable.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

On Wednesday, December 30, 2020 at 8:41:08 AM UTC-8, Eric Greenwell wrote:
Brian wrote on 12/30/2020 7:42 AM:
On Tuesday, December 29, 2020 at 8:42:19 AM UTC-7, krasw wrote:
Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.

I put a 10 Watt a panel on my HP16. It averaged 200-250ma charging a 12AH Lead Acid batteries. The real advantage was when I was flying contests or safaris where I left the plane tied down. I could fly about 3 days in a row without needing to charge the battery. If we had a rest day it would pretty much top off the battery. I didn’t use a charge controller, I just used a volt meter. Since I only left it tied down when I was flying almost daily I didn’t figure 200-250 was enough to hurt the battery. But if I didn’t fly for more than a day I would disconnect it.

I loved having the solar panel, most of the time I didn’t need to charge the battery when flying daily. I wish I could come up with a reasonable panel to install on my LS6.

IMO Unless you are leaving the plane outside for extended periods without flying almost daily, my opinion is you don’t need a charge controller for a 20 watt or less solar panel. An appropriately sized and heat sinked Zenor diode would prevent it from overcharging if you did inadvertently leave it connected. If it is connected only when flying then no controller is required.

Brian's solution is a good one for gliders with a low enough current drain. Like Moshe, I
struggled to find a good place to put a useful amount of solar panel on my glider, given the
1.5 amp draw while flying. I eventually gave up trying, and installed a 20 AH Life battery,
which is enough capacity for two long flights. Normally, I recharge it after each flight from a
30 AH "donor" battery which is charged during the day by a 40W solar panel on the trailer,
using a DC-DC charger for electric model hobbyists. That's easy enough, and reliable.
--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

The problem with using the glider's solar panel to recharge the battery is that there is, simply, not enough sun hours available to do the job if you fly consecutive days. To recharge a 20AHr LFP with a 200mA panel will take 100 hr - and there is only about 7 sun hours available per day. Even a partial charge would take multiple days. I do exactly what Eric does except my battery charger is AC/DC so I can choose which power source I want to use. My preference is to use AC, but that may be inconvenient at some fields. My donor batteries total 40AHr, so I can go multiple days w/o recharging them.. My only glitch to date is one solar charge controller I bought from Bioenno literally melted when left out on the ramp (they replaced it under warranty).

Tom

On Tuesday, December 29, 2020 at 7:42:19 AM UTC-8, krasw wrote:
Any ideas for Strobl controller replacement? The voltage is not enough for LFP battery. Victron SmartSolar MPPT 75/10 looks good, but according to specs Strobl solar cell voltage is not enough to start the unit (!). Genasun has appalling efficiency.

Just take out the controller altogether. The only LFP batteries I would consider have an internal BMS (battery management system) that protects against over-charging (which won't happen airborne, anyhow). I passed on solar panels altogether for my new ASH31Mi because their output was so paltry compared to the draw of my full glass panel (2A) that it was just not worth the cost ($2,500). I put in an LFP avionics battery instead (20AHr) and supplemented that with a 12AHr battery. That works fine if I remember to turn off my master.

Tom