# Offgrid with LiFePO4 and energy graph



## electrodacus (Feb 26, 2015)

I moved OffGrid two years ago and decided to use LiFePO4.
Here is my sytem and below a 7 day energy graph so you get an idea on how much energy I produce and use. Is quite small with what other may want but maybe is good to have an idea.
I also designed and build the house but that is probably for a difrent thread.


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## gpforet (Dec 24, 2013)

Can you provide some specifics regarding battery bank capacity and cell arrangement? Also, having used LIPO for aerial photography work, I am familiar with their unique charging requirements. How are you managing their charge?


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## electrodacus (Feb 26, 2015)

gpforet said:


> Can you provide some specifics regarding battery bank capacity and cell arrangement? Also, having used LIPO for aerial photography work, I am familiar with their unique charging requirements. How are you managing their charge?


You can see the setup in the first photo. I have 3x 240W solar PV so 720W total then I have a 8 cells LiFePO4 100Ah from GBS so is a 24V system and I use my Solar BMS 4080 I say mine since I designed and build that and that takes care of battery management and charging (also the SBMS4080 was used to produce the energy graph).
I use mostly DC for the house so LED lights, two laptops a small peltier based fridge a DC pump that works all the time in winter 7.5W for some stupid frost protection.
The AC inverter I only use one or two hours a day in sunny days mostly for electric cooking.
I already have two years of full OffGrid living and do not need a generator or vented box for the battery not needed with LiFePO4
Lead Acid will have been dead already used in this conditions or I will have needed a way larger capacity battery to last 5 or 6 years.
But it will have probably not have been working at all. I can not understand how people use Lead Acid for OffGrid in the winter with a vented box he battery will be always at the outside temperature level and here over 4 months is well below freezing.
So for me Lead Acid will not have been working at all.

How do I get email notifications for replay on this post ? I did not get any email notification for your replay. I do not see an option.


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## spacecase0 (Jul 12, 2012)

I use a large set of AGM batteries, they are inside and not vented, they were free batteries pulled from airplanes because they were to old for that service, 
I don't charge them to the point where they would vent, but then again you are not suppose to do that to them, 
I just end up using way less electricity than I could be using so that I don't hurt the batteries 
would really rather be using LiFePO4 
to bad I don't have enough money to get a set of them.


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## MichaelK! (Oct 22, 2010)

spacecase0 said:


> I don't charge them to the point where they would vent, but then again you are not suppose to do that to them,


Could you explain exactly how you actually do that? Is it a voltage setting on your charge controller, or are you monitoring things manually? How do you actually know when they are venting gas? Are there caps you remove to look inside for bubbles?


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## spacecase0 (Jul 12, 2012)

MichaelK! said:


> Could you explain exactly how you actually do that? Is it a voltage setting on your charge controller, or are you monitoring things manually? How do you actually know when they are venting gas? Are there caps you remove to look inside for bubbles?


yea, it is a voltage setting, 
there are no caps or way to look at or add liquid on AGM batteries 
they have a catalyst that recombines the hydrogen and oxygen in each cell, 
so if you are under the limit of the amount of gas, then it works and will not vent, 
and if you stick to the float voltage, then you are fine 
I looked up the instructions for the batteries on the web and they had the voltages listed on a chart VS temperature 
each manufacturer will have slightly different chemistry that gets you slightly different voltage, 
if you can't find detailed specifications on them, then likely a bad idea to buy that one, but sometimes the voltages are printed right on the side of the batteries


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## Alaska (Jun 16, 2012)

We are just way too much of energy hogs for that system.Pool,AC,2 freezers,fridge,microwave,big screen tv,DVR etc....
We will be switching to AGM batteries in the near future. Mostly brcause the deal Im getting is just way to good to pass up and I will have another use for the surrettes I have now.


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## spacecase0 (Jul 12, 2012)

if you use lots of power, and want your batteries to last a long time, go look at the nickel iron batteries. 
they cost lots, but last a very very long time


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## electrodacus (Feb 26, 2015)

spacecase0 said:


> if you use lots of power, and want your batteries to last a long time, go look at the nickel iron batteries.
> they cost lots, but last a very very long time


Those are a way worse choice than Lead Acid.
Extremely inefficient and they will require quite a bit of maintenance (time is also money).
I know I may look biased but I looked at all available storage mediums including Nickel Iron and Lead Acid.


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## Jim-mi (May 15, 2002)

One of the big problems with Edison batteries is the large voltage swings.
When you have gotten them--fully--charged up, the voltage is above the high voltage cutout limit of good inverters.
Conversely they still have plenty of umph when they have gone below the low voltage cutout limit of good inverters.......


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## spacecase0 (Jul 12, 2012)

Jim-mi said:


> One of the big problems with Edison batteries is the large voltage swings.
> When you have gotten them--fully--charged up, the voltage is above the high voltage cutout limit of good inverters.
> Conversely they still have plenty of umph when they have gone below the low voltage cutout limit of good inverters.......


if you set it up for 12V inverters this is true, they have a very narrow tolerance for voltage change.
I would be looking in the 48V range for the setup 
like I sad, pricey, but system run time will be counted in decades


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## Jim-mi (May 15, 2002)

48v inverters have their own upper and lower limits........
No way is that limited to 12v . . . . . . .I wasn't even thinking about a 12v system......


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## spacecase0 (Jul 12, 2012)

Jim-mi said:


> 48v inverters have their own upper and lower limits........
> No way is that limited to 12v . . . . . . .I wasn't even thinking about a 12v system......


let us use this inverter with 27 or 28 cells and it falls well within the limits of charge and discharge, even 29 cells would work, 
http://www.aimscorp.net/5000-Watt-36-Volt-Power-Inverter.html 
higher voltage inverters do have limits, but there are many out there that will work. 
with a window of 3 cells on your batteries, this is not going to stop anyone from building a system


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## Jim-mi (May 15, 2002)

Your just looking for problems down the line by using non standard voltages.......

My references are to the much better inverters........not Aims.


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## spacecase0 (Jul 12, 2012)

the inverter I picked was just because it was the first one to show up with a search where I could find the actual voltage in range
pick whatever brand you like, 
if you think that 30-48V in is non standard, then pick another range, with the 12V range being the only one that will likely not work that well
I was just pointing out that there is no real reason not to use the longer life batteries, 
replacing your lead acid batteries every 5 to 7 years sounds like problems down the line to me
but I guess you have to personally pick what you would like to be your most likely failure point in the future,


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