Lithium battery charge profiles

[mahendra]

yes i agree but still the price is a very big factor.

[Cniemand]

Kurt, your last posting had me cracking up!

You can toss my name as another lipo4 user that hasn't had any issues with them. I've had the system up 10 months now in a full off-grid usage. I've been here daily. The cells just sit there all balanced amongst themselves.

The Classic is a great controller for Lithium with its ability to custom set the voltages and turn off EQ etc.

As stated many times earlier. It is comes down to using the middle of their charge. Under and Over voltage is the bad area. Through cutting off those points on the Charge curve where it either plummets or shoots off, you save them.

The capacity remaining at those ends is very little anyhow. You end up loosing very little capacity but greatly increase life-times of the bank as well as leaving them in the safe zones.

Another note, it is easy to string the individual cells in series to get your 48v and never need a parallel connection.

[mahendra]

can anyone here state the price range for the lithium batteries they have been praising so much.I definitely know the benefits but the lithium but those i have came across are just too expensive or they are not available where i can purchase them.So please recommend a brand ,place of purchase and price range.

[Cniemand]

I am using CALB cells. 16 - 100aH cells. I purchased mine from the evtv store in Missouri. Each cell was USD$150. Thus the 48v 5kwh bank was USD$2500 with shipping.

Your milage may vary of course.

[mahendra]

so each cell is about 3.1v or so

[Cniemand]

48 volt nominal. The Lifepo4 cells are spec as nominal 3.2v. I charge them to 3.5 each. At 3 volts you should consider them fully discharged to save them from plummeting.

I think the actual spec is between 2.5 and 3.65v.

I have mine programmed to charge to 55v then float at 3.34v per cell which is their resting voltage.

[mahendra]

ok kool, But what i noticed is the there aren't any or there are very few US suppliers of these batteries ,I have source these or similar from Australia.Shipping cost is a killer

[Cniemand]

True. Although, to be honest. Solar is pretty inexpensive for what it is already. My entire system of 2000w and lithium batteries which quality componenets such as 200v MNCC and outback 3600 watt inverter was only USD $7200.

I guess I could have cut some money off through using lead but I didnt want the maintenance and venting issues.

[mahendra]

total cost $ just $7200?

[mahendra]

While we are at this can i be intrusive and ask how much you discharge your batteries when the sun is not shining?

[Cniemand]

At night. Depends how much hot tea im drinking (electric kettle) and how much netflix im watching on the 42in tv or if Im just using the led lights and surfing the internet.

These days, between 6pm and say 11am when it kicks back to float, shows 2.5 to 3kwh. Mostly on the lower end.

80% DOD in the bank is 4.1kwh. So I guess I am using on average at night 50-60%

If it is a spell of cloudy/snowy days I'll throttle back but that is rare up here in Colorado.

I've never had to use a generator, which was my point of having so many panels.

[Cniemand]

My total cost for all the components was $7200 with shipping and taxes applied. No permit costs or electrician.

$2500 of which was the batteries.

So, 8 panels, a midnight solar 200v charge controller, an outback 3600 inverter, a midnight solar lightning arrestor, and a midnight solar two string combiner box.

So, when you factor in the wiring and diy racking used. More $7500.

[mahendra]

Nice i use approximately the same as you but as with my battery bank going below the 80% soc means reducing the battery bank life.I read in an article that lithium can be discharged at about 50% Dod .Guess a guy like you can only verify that

[mahendra]

that's not bad i bought my equipment in pieces and has reached that amount and i am still at 12v ,really want to switch to 48v,but cannot do that until i raise funds for 48v inverter or be forced to buy on when my 12v Xantrex dies.

[Cniemand]

Actually, that is where others talk about the savings of being able to use much smaller battery banks and get the same usable capacity.

The Calbs Lifepo4 battery chemistry has data showing 2-3000 cycles with 80% DOD regular usage.

I think, Kurt, was talking about how you can essentially cut your bank to half the size needed in Pb when switching to LFP4 batteries.