The Great Big Lithium Lie

So, I finally jumped onto the Lithium band wagon after finding Will on Utube. As he stares many times unlike Lead acid batteries that can only use 50% of their capacity... Lithium Batteries can use 100% of their capacity.
In reality Lithium batteries cannot go below 20% or they will be damaged and should not be charged above 90%. My Overkill BMS default settings actually cut off charge at 87%. So that leaves usable capacity of Lithium batteries at 67%. Hell of allot closer to 50% than to 100%.
Secondly, a big selling point is slow discharge rate. I could never monitor what my 2 105ah AGM batteries were losing but my BMS shows I lose over 10% capacity overnight with LIFePO4 with no draw except a unmeasurable milliamp volt display attached.

Dont get me wrong. The ability to monitor my system on the iPad is way cool. But if someone was to tell me; you can spend $700 on a 200ah Lithium Battery, Overkill BMS, etc... and end up with about the same capacity as my existing setup.
Or you could use that money to buy 2 more 100watt panels and 2 more 105ah Batteries and double my capacity. I may have thought twice.

in the end I would most likely have did it again as my AGM batteries were 10 years old. (Still showing 96% and 76% respectively ).
but just let’s not give people unrealistic expectations.

My LiFePo4 batteries claim they will maintain about 80% of their capacity after 2000 cycles at 100% discharge. Do you have a link to a lead acid battery that can do 2000 cycles?

LiFePo4 can go from 0-100%, and last 2000 cycles. The only reason everybody suggest 80% is to extend the life cycle to 3000 or 5000 cycles. I personally will be cycling mine to 95% and using it everyday. Even at 2000 cycles, it is still plenty of life for me.

You can take your AGM to 100%, but you will severely decrease its life span, so people recommend 50-70%.

Sundog33 said:

My Overkill BMS default settings actually cut off charge at 87%. So that leaves usable capacity of Lithium batteries at 67%. Hell of allot closer to 50% than to 100%.

Click to expand...

Default is 100% unless your battery is something special.

Well. I’m just going on suggested usage. If indeed I can cycle them fully and get what I got out of my AMGs then I am ahead of the game. I couldn’t believe when I disconnected them and one AMG was still showing 96% capacity from my car CCA tester after 10 years. I was amazed.

Also, I got a chip on my shoulder about Solar Panel output. I never had a way to check my input wattage from my 2 100w panels. Turns out of a perfect spring day with cool conditions and full sun I am only getting 60watts!
my run is only 6 feet from my panels outside my garage to the MPPT so no lost.
I guess if i threw some money into a solar tracker I may get more but 25% is kinda a joke.
it is what it is but these panels should be better advertised in reality.

A CCA tester is not the correct way to test a deep cycle battery, you have to do a capacity test on it to truly know how much amps are stored, not how many amps can be supplied (which is what a CCA tester does)

It sounds like your BMS settings are too conservative...

What brand are the panels?

Panels in series or parallel? I would be checking the connections. Need to measure the individual panel production. Seems like one is not producing.

And post the controller model you are using.

Sundog33 said:

Also, I got a chip on my shoulder about Solar Panel output. I never had a way to check my input wattage from my 2 100w panels. Turns out of a perfect spring day with cool conditions and full sun I am only getting 60watts!
my run is only 6 feet from my panels outside my garage to the MPPT so no lost.
I guess if i threw some money into a solar tracker I may get more but 25% is kinda a joke.
it is what it is but these panels should be better advertised in reality.

Click to expand...

What is the angle of the sun to the face of the solar panels? If you don't adjust the angle day-by-day, you will get less than 100% of rated output. Hold a stick perpendicular to the surface of the panel and see if the shadow is a point or a line. If it's a line, then the sun is not hitting the panel directly and some of the light is being reflected away.

May I suggest that some of the results you are experiencing are not correct
Take the example of loosing 10% of capacity on an unloaded lithium pack. Either there is a load that is not apparent, or more likely the softwere in the bms. If you have an Overkill bms this false reporting of capacity sometimes happens.

The Overkill bms with default settings will allowed a charge to 100%, it's possible your charger is at fault.

I do not believe an AGM battery will have 96% amp hours capacity after 10 years, it's impossible. Cranking amps are not the same as capacity in amp hours

Getting only 60 watts from a 100 watt panel sounds poor but without knowing the model of MPPT, it's settings and the battery state and load, its, not possible to comment. My guess is that the solar controller is a PWM type.

It seems you are having a bad day, just take things easy and establish with more tests and measurements that what you are seeing is actually the case.

Mike

Surferdudemi said:

What is the angle of the sun to the face of the solar panels? If you don't adjust the angle day-by-day, you will get less than 100% of rated output. Hold a stick perpendicular to the surface of the panel and see if the shadow is a point or a line. If it's a line, then the sun is not hitting the panel directly and some of the light is being reflected away.

Click to expand...

It is hard to do with a stick. Easy to set a can on it, and adjust panel angle until the shadow disappears.

mikefitz said:

May I suggest that some of the results you are experiencing are not correct
Take the example of loosing 10% of capacity on an unloaded lithium pack. Either there is a load that is not apparent, or more likely the softwere in the bms. If you have an Overkill bms this false reporting of capacity sometimes happens.

Click to expand...

Agreed!
I had to go in and tell the BMS my AH of the pack. My 160Ah pack has sat for weeks with zero measurable drop...
Yesterday I ran a water transfer pump for 2 hours, filling buckets of water, and still didn’t dent the 3,2 Volts... that cliff holds a LOT of watt hours!

I’m not sure the brand of panel or mttp. I wired up this system with little online help 10 years ago when solar was new. I wanted to have some backup power for the end of the world in 2012. But that never happened. Lol
so I have just be using it to run my 55 fish tank.

Ok. So I just got this hooked up. I am using the default Solarkill interface that says 100ah. Not the 200ah that I have.
I bought the config software but I don’t know all the input voltages I should put in. I was hoping I could just change it from 100 to 200. But it is asking for everything

My setup

Sundog33 said:

Also, I got a chip on my shoulder about Solar Panel output. I never had a way to check my input wattage from my 2 100w panels. Turns out of a perfect spring day with cool conditions and full sun I am only getting 60watts!
my run is only 6 feet from my panels outside my garage to the MPPT so no lost.
I guess if i threw some money into a solar tracker I may get more but 25% is kinda a joke.
it is what it is but these panels should be better advertised in reality.

Click to expand...

I have 6 - 100 watt panels that regularly hit 550 watts before the heat of the day. My SCC won't let them get much higher as it is only 20 amps and clips them.

Edit to add, 60 watts out of 200 watts of panels should be investigated.

The side batteries are just portable server batteries I got from work

The panels are series right? so double the watts and same voltage
if it was the other way I would be getting 36volts out

Series means double volts and amps are the same. In effect, you get double watts.