Tag Archives: solar tips

Lithium vs Lead acid: a charge profile primer

How lead acid and lithium batteries charge

Recently I was asked if lithium batteries( lfp) accept more voltage from solar panels than lead acid batteries (fla). The short answer is No. But, they do accept more amps! You see as your batteries charge the peak voltage limit is hit and then amperage begins to taper.

The formula you need to remember is voltage X amperage = watts. In battery charging amperage is key.
The formula you need to remember is voltage X amperage = watts. In battery charging amperage is key.
Amperage is the key

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Batteries and bus bars

Wiring batteries and bus bars
Simple improvements in bus bar and battery wiring can improve efficiency and longevity of your solar battery pack.
Simple improvements in bus bar and battery wiring can improve efficiency and longevity of your solar battery pack.
Improving efficiency and lifespan

Batteries are currently (ha ha) the weak link in the off grid solar equation. If you’ve gone through my site you know I’m a HUGE fan of lithium iron phosphate batteries. Basically flooded lead acid batteries are the equivalent of a 70s automobile. Ya. Looks like a car. But …

Still, if you’re doing a small off grid solar electric install lead acid aren’t horrible and they are cheap. So here are creeky’s top tips for improving efficiency and lifespan when hooking up lead acid.

Creeky’s 6 Top Tips

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Cool cats on a hot tin roof

Passive solar cooling using a metal roof
The basic concept.
The basic concept.

There was some research done around 2008. First by a fellow in Africa looking for a way to cool the metal roofed homes that poor families lived in. Under the hot sun they became ovens. And he worked out a method of using two layers of metal roofing to draw cool air from the ground up between the metal layers of the roof to expel hot air at the roof peak. This cooled the tin. Keeping the homes usable for longer periods of the day.

Another researcher in Texas found he could use roof ridge vents, metal roofing and foil covered polyiso sheathing to move air out of the test home attic, cooling the attic from 130F to 80. Pretty significant.

My experience

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Electric fridge for off grid — YES

What? An electric fridge off grid

To heck with hauling propane. Introducing the Magic Chef 10 cu. ft. fridge.
To heck with hauling propane. This is my Magic Chef 10 cu. ft. fridge.
Yes. And why? Money $$$

Like most folks I started off grid with a propane fridge. Now propane fridges are great if you’re traveling because an absorption fridge works even while it’s being shaken (if not stirred).

But when you live off grid, chances are your fridge isn’t moving. So now it comes down to saving $$$.

How cool are the savings?

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Solar tips: Why 1 watt to 1 amp

1 watt of solar to 1 amp of battery storage

I developed this basic rule of thumb about 5 years ago. When I did my initial solar research I noticed that off grid, either full time or RV boondocking, the folks who were happy with their systems typically had 1 watt of solar panel per 1 amp of battery capacity (measured at 12v/lead acid battery packs).

Lead acid. Yuck. But I've still got mine. 4 years and still chugging along.
Lead acid. Yuck. But I’ve still got mine. 4 years and still chugging along.

Those with less panel grumbled about “genny time” and worse. The consequence of lead acid battery packs: over discharge & under charge = dead batteries.

So let’s look at a small system

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