Question about battery charging and solar panels.

[tchendrix]

Ok I've got a few questions as I dip my toe into DIY solar.

a) Is it feasible to charge the batteries and run what i need during the day off of solar and then draw from the batteries only at night

b) batteries say 2000-3000 cycles ... does this men down a cycle is a draw down to the DoD and full recharge?

c) how does item a) play into battery cycle limits?


Thanks in advance

 

[GLC]

Ok I've got a few questions as I dip my toe into DIY solar.

a) Is it feasible to charge the batteries and run what i need during the day off of solar and then draw from the batteries only at night

b) batteries say 2000-3000 cycles ... does this men down a cycle is a draw down to the DoD and full recharge?

c) how does item a) play into battery cycle limits?


Thanks in advance

A. If you are making more pv solar than you are consuming during the day then yes, you will have battery storage reserves at night for power requirements.
B. Cycles will depend on type of batteries, like lpo4. One cycle is 100 percent to zero although i would not push it that far.
C. B determines cycle limits not A.

 

[rmaddy]

a) Is it feasible to charge the batteries and run what i need during the day off of solar and then draw from the batteries only at night

Feasible, yes. I've been doing just that daily for the last 11 months. But it does depend on a lot of factors.

You need enough battery capacity that can handle your overnight loads, morning loads (before there's much solar to start recharging much), and late afternoon/evening loads when the solar can no longer keep up with the loads and the battery starts kicking in. On top of that you need enough battery capacity to get you through poor solar days.

You need enough solar that can power the loads during the day plus have enough to fully recharge the battery at the same time. You need to account for cloudy days and winter when there's far less solar available each day due to low sun angle, short hours, and typically cloudier conditions.

 

[tchendrix]

A. If you are making more pv solar than you are consuming during the day then yes, you will have battery storage reserves at night for power requirements.
B. Cycles will depend on type of batteries, like lpo4. One cycle is 100 percent to zero although i would not push it that far.
C. B determines cycle limits not A.

looking at your system in your profile are you completely off grid?

 

[GLC]

looking at your system in your profile are you completely off grid?

No sir, still on grid. I do have 2 manual transfer boxes , 10 circuits each, where most of my 110 power is pulled off of solar. Still powering dryer, range, hvac off of grid. I am powering 2 minisplits off of solar though. 2400 sq ft home.

 

[tchendrix]

my house is just about the same size... what was your total cost for the solar equipment. I don't think i'll be able to afford to do this...

 

[BradCagle]

Ok I've got a few questions as I dip my toe into DIY solar.

a) Is it feasible to charge the batteries and run what i need during the day off of solar and then draw from the batteries only at night

Absolutely, that's usually the ideal situation.

Typically the MPPT will charge your battery, when it's full the MPPT will sense the other loads consumption, and provide just that amount causing your battery to not discharge during the day provided there is good sun. You might see the battery discharge while clouds pass by, etc..


Now here's the thing not all MPPTs behave the same, and sometimes you have to fiddle with them to get this working properly. Some will charge the battery, and just stop until the next day. Some will charge the battery, and wait till the battery discharges to a certain voltage level then they kick back in. Fortunately almost every MPPT I've played with, I've been able to change the settings to get it to work how I want.

 

[GLC]

my house is just about the same size... what was your total cost for the solar equipment. I don't think i'll be able to afford to do this...

I have about 17,000 in it. Although 11,000 is batteries. Price and availability has come down since i did mine. You could probably do what i have for around 12,000 now. You do your own install.

 

[tchendrix]

so if my math is right you have about 29 KwH of battery storage and and about 6.1 Kwh of pv capability? Does that mean your batteries will charge completely in about 5 hours?

 

[GLC]

Bear in mind that i have my batteries go into float every afternoon. I do this so i can run fridges and mini splits at night time while i am fully charged. During the day, i always produce more pv than what is needed. As long as i am producing more pv than what i am using, i will intentionally run a minisplit helping the hvac unit during the day.