rshev wrote: ↑Wed Jul 24, 2019 4:07 pm
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As to the solar panels, yes, it is a tie-in to the grid with an LG battery as backup. My hope is that with judicious economizing, I might be able to get a full night with the LG and then recharge the next day. Sadly, the LG is of somewhat limited capacity and so I may need additional power for my CPAP--thus my question on this forum. ...
Ah ... the plot thickens! You actually have a small off-grid system but having thoughts that it might not be enough and you should have a backup for the backup! The real answer of course is simply make the off grid system big enough - but that is easier said than done.
So the "backup for the backup" is easy. Get a 100 amp-hour AGM (about $180). The 5 or 6 amp BatteryTender should handle it if you can't use the solar. This should cover 7 nights at 8 amp-hours per night with a fair margin. Or get 3 of the U1 (35ah) batteries so you can carry them easier. Or get a 100 and 35 so you have a backup for the backup for the backup. (I'm only being slightly sarcastic - I'm a "belt and braces" guy!)
BTW, on my boat I live off grid - 350 watts of solar and a 480 amp-hour house bank support a small fridge, several computers, phones, lights, fans, microwave, and my cpap. I have a few alternate charge options but haven't had to use them this summer. My theory is to make the house system, which I rely on everyday, overkill - at least enough to run 3 days while inhabited with no sun, 5-7 days uninhabited.