How many of you set your battery max discharge under 20% ?

[Tulex]

I only go to 50%. For no other reason than half the reason I went into solar was to have backup.

 

[OffGridInTheCity]

Nice breakdown!

Thank you.

At 60 years old the new LFP I installed this year will probably out last my life cycles.

Yes sir - I'm 69 so....

 

[Skypower]

How many of us will run out of cycles and calendar aging before our batteries do, raise your hands?

 

[Skypower]

My back to grid is 15% and only hit it a few times early in the start of the project. With more batteries and better management I don’t even get close.

 

[Lt.Dan]

Sorry for the ignorant question (I'm quite new to this) but what is it about charging fully that ensures the battery is properly balanced? Is that something the BMS can only do at full charge, or what?

No problem, everybody has to learn somewhere.

Since LFP has such a flat voltage curve, the BMS is (usually and absolutely should be) programmed to balance once a cell is above 3.4v/cell. 3.4v/cell is 99-100% SOC, so yes, a LiFePO4 battery can only be (top) balanced at full charge.

There are other instances to bottom balance, but for Solar installs, top balance is almost always the way to go.

 

[fafrd]

No problem, everybody has to learn somewhere.

Since LFP has such a flat voltage curve, the BMS is (usually and absolutely should be) programmed to balance once a cell is above 3.4v/cell. 3.4v/cell is 99-100% SOC, so yes, a LiFePO4 battery can only be (top) balanced at full charge.

There are other instances to bottom balance, but for Solar installs, top balance is almost always the way to go.

Uhhh, I’m a solar install and I beg to differ.

I’m thinking you probably meant ‘solar backup-power installs’ where the battery is charged full daily and rarely if ever discharged.

For that solar use-case, I fully agree.

I don’t care about backup power for my use case, which it offset of consumption.

I capture all my DC-coupled solar power in my battery during the day and use that stored energy to offset consumption for as long as that battery charge will last into the night.

So my battery never, ever gets fully-charged and is fully discharged nightly.

For that solar use-case, a bottom-balanced LiFePO4 battery works much more effectively than a top-balanced LiFePO4 battery…

[P.S. just noticed that you did preface with ‘almost always’ so assuming I am the outlier you seem to presume, no argument - I really don’t know what % of members here are primarily motivated by consumption offset rather than backup power - perhaps I’m the only one ].

 

[SilverbackMP]

I see after you were put on ignore you have decided to troll my comments.

LiFePO4 BatteriesThis means that you can safely discharge these batteries to their full capacity. However, most manufacturers recommend still using a 80% DoD for these batteries to prolong their lifespan. Even if you occasionally use 100% of the battery capacity, the battery will not get harmed. https://ecotreelithium.co.uk/news/lifepo4-battery-depth-of-discharge/#:~:text=LiFePO4 Batteries,-LiFePO4 battery cells&text=This means that you can,battery will not get harmed.

Is it bad to completely drain a LiFePO4 battery?

LiFePO4 batteries can be continually discharged to 100% DOD and there is no long-term effect. However, we recommend you only discharge down to 80% to maintain battery life. https://www.relionbattery.com/blog/tech-tuesday-depth-of-discharge#:~:text=LiFePO4 batteries can be continually,80% to maintain battery life.

ADDED: It appears from Will's comment above he also agrees with what I posted.

Add me to your ignore list please.

 

[Solarcabin Channel]

Add me to your ignore list please.

As you wish and just ask you do the same!

 

[addision]

Late to the game on this but I still want to comment.

If we look at the battery developments over the past 10 years and what the cost of the the batteries were 10 year ago we have a vastly superior product for a "good" price right now. Technology will only improve in the next 10 years for a better cost.

10 years is way shorter than the expected cycle life even discharging your batteries to 10%.

I fully expect to be changing out my batteries between 10-15 years. I may not have to, but I'm planning for it and I would love to be wrong. The battery technology and the technology of solar may change drastically by then, we could have 1000w panels and a single small battery could have a 50kwh capacity for a cheap price.

It is like having equipment from the early 2000's and for sure you will want to change to new equipment now. Even if you got top of the line back then.