Tag Archives: battery

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

Continue reading Lithium vs Lead acid: a charge profile primer

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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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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LFP is King — and I have proof

Vindication is mine

Dear readers, as you know I’ve been touting the energy storage benefits of lithium iron phosphate batteries (LFP) for off grid families who need reliable solar / wind / hydro energy storage from the moment I discovered a plug and play format earlier this year.

Sharing my realization on sites other than this one, I have been attacked, yes, and slandered, by a variety of what I have come to call “leadites.” Those who cling to this idea that solar power will remain in one fixed position.

Oh the battles I could tell you about. But today, dear reader, I found scientific proof to my hypothesis that LFP is the new best solar/wind off grid storage media.

To wit:

A comparison of lead-acid and lithium-based battery behavior and capacity fade in off-grid renewable charging applications
by Elena M. Krieger, John Cannarella, Craig B. Arnold
Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ USA

Mwha ha hah … take this leadites …

Continue reading LFP is King — and I have proof

LiFeP04 vs Flooded Lead Acid batteries

Post from Simon, Karrak Farms, Australia

Creeky says: I thought this was interesting, so I bring this to the attention of those who are interested in LFP batteries for offgrid power storage.

LFP compared to FLA
LiFePO4  Flooded Lead Acid
Total Operating Voltage Range 14.4 – 11.2 15.5 – 10.5
Normal Operating Voltage Range, No Load 13.8 – 12.8 (90%-20%SOC) 15.5 – 12.0 (100%-50%SOC)
Normal Operating Voltage Range, C/8 Load 13.8 – 12.4 15.5 – 11.0
Normal Operating Voltage Range, C/2 Load 13.8 – 12.0 15.5 – 10.5
Max sustained charge rate 1C C/8
Recommended sustained charge rate N/A C/10
Sustained discharge rate 1C C/8
Peukert Coefficient ~1.02 1.2-1.6
Current efficiency >95% <90%
Lifespan ~10 years ~6 years
Warranty 5 year prorata (balqon) 5 year prorata (trojan)
Cost per kWh ~US$340 ~US$130
Cost per usable kWh ($/kWh/cycledepth) ~US$523 ~US$325
Cost per usable kWh per year ~US$52.30 ~US$54.20

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LFP battery revolution changes off grid electric forever

I am weeping with joy as the Lithium Iron Phosphate battery (LFP or LiFePO4) completely changes off grid energy storage

Recently I stumbled across the Balqon LFP 9kw energy storage battery. It comes complete: battery management system, even a fuse, so it’s plug and play. The benefits look amazing, but how will it fare in comparison to my lead acid battery pack?

LFP battery pack
This Balqon LFP battery pack gives you 13 years of 4.5 kw daily energy use and you can buy it today. I’m in love.

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My off grid solar experiment

 Creeky’s solar system:
Or how I live the life of Riley off grid
Check out the coming Solar posts for more information about how I built my solar system.
Background:

When I started building my solar system in 2010 there were very few resources available in my part of the world. So I took the “build it and hope” approach.

  • First I built a solar shed with a rack that allows the solar panels to be easily adjusted for spring/fall, summer, winter, and big wind storm in the forecast. You can read more about the shed in the shed post.
The first cladding of the solar shed is complete. Let the rains come.
The first cladding of the solar shed is complete. Let the rains come.
  • Then I got some good batteries configured for 12 volts
12vbatterypack
These are Crown 395s. I have 6. 3 sets of two, in serial, in parallel strings. Works for me. And gives me about 1200 amp hours at 12 volts or 15kw of power. Which, with lead acid battery packs means about 3kw of reserve power.
  • I installed 1kw of solar panel power. Panels were in the 4 to 6 dollar a watt range. I was very fortunate to find high quality mono crystalline panels for $2/watt from a solar provider clearing inventory of demo panels.
    • As I’ve grown my needs I’ve upgraded to two mppt controllers so that I can have 2 kw of panels to charge those batteries. Currently (ha ha) I have 1.5 worth of panels
The solar shed
This is me spring of 2012. 1kw of panels working away.

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