Audit Spreadsheet verification

[Begginer7]

Of course. C rate is dependent on the battery capacity. 100Ah is 100Ah at any voltage, thus requiring 10-20A. If you have to put 50Ah in, you'll need at least 3 hours @ 20A.

If you put the 12V in parallel, now you have 200Ah. Now you charge at 20-40A. If you have to charge 100Ah @ 40A, you'll need at least 3 hours.

Lead-acid requires a fairly long absorption time to get truly full. The 3+ hours I mention will get you nearly fully charged and would be fine for occasional help, but the batteries should regularly be topped to to truly full, and that may require 2-4 hours in absorption phase alone.



LFP can typically charge 0.5C or higher with a very short absorption period - usually less than 30 minutes.

And what happens if I will be using the acid batteries at the time of charging? The fridge alone uses 31.25 Wh per hour so for 3 hours abour 94Wh it might extend the charging time time a 15%, is it ok to do that?

 

[sunshine_eggo]

And what happens if I will be using the acid batteries at the time of charging? The fridge alone uses 31.25 Wh per hour so for 3 hours abour 94Wh it might extend the charging time time a 15%, is it ok to do that?

Yes. It will extend the charge time. If you KNOW you're going to have a constant drain during charging, you can justify "charging" at a higher current, e.g., if you're going to pull 5A while charging, you could "charge" at 25A with 5A going to load and 20A going to battery leaving your charge time unaffected.

 

[Begginer7]

Yes. It will extend the charge time. If you KNOW you're going to have a constant drain during charging, you can justify "charging" at a higher current, e.g., if you're going to pull 5A while charging, you could "charge" at 25A with 5A going to load and 20A going to battery leaving your charge time unaffected.

Ok, but I am thinking to do that I would need a charger that can adjust it, as I am trying to source locally that means almost sure Victron, I will have a look at the options but leaving the generator on for 3 hours often is something I dont want to do, although here we havent seen more than 3 cloudy days consecutively and I have 2 panels that can charge the batteries in one day at a C of 0.33. I think the weakness of the design is the one day of autonomy but budget constrains wont let me increase that.

 

[sunshine_eggo]

Ok, but I am thinking to do that I would need a charger that can adjust it, as I am trying to source locally that means almost sure Victron, I will have a look at the options but leaving the generator on for 3 hours often is something I dont want to do, although here we havent seen more than 3 cloudy days consecutively and I have 2 panels that can charge the batteries in one day at a C of 0.33. I think the weakness of the design is the one day of autonomy but budget constrains wont let me increase that.

Solar charging is often variable. While your peak may be capable of 0.33C, it's often the case that you're well below that in the morning, and by the time the panels really start producing peak power, you're already in absorption or float, and/or you're using loads, so they'll never actually see 0.33C.

You need to avoid charging the batteries at greater than their rating. It can dramatically shorten their life.

 

[Begginer7]

Solar charging is often variable. While your peak may be capable of 0.33C, it's often the case that you're well below that in the morning, and by the time the panels really start producing peak power, you're already in absorption or float, and/or you're using loads, so they'll never actually see 0.33C.

You need to avoid charging the batteries at greater than their rating. It can dramatically shorten their life.

The only Lifepo4 that I can source localy is brand Leoch that has a 0.5 C rate with 100% efficiency of charge, will this battery be ok beign charged at the (nominal) .33?

 

[TorC]

Yes. Lithium is less sensitive to charge characteristics in both directions. Since you won't get your numbers low enough to make do with one battery, switching to two of those batteries totaling 24V,100Ah will also give you about half again as much effective storage.

If you have a matching SCC and inverter, they will often talk to each other and coordinate total amperage into the batteries. This is much safer than just setting a high charge current to account for inverter draw and more effective at grabbing every watt you can. AIO units can be expected to do this, too.

 

[Begginer7]

Yes. Lithium is less sensitive to charge characteristics in both directions. Since you won't get your numbers low enough to make do with one battery, switching to two of those batteries totaling 24V,100Ah will also give you about half again as much effective storage.

If you have a matching SCC and inverter, they will often talk to each other and coordinate total amperage into the batteries. This is much safer than just setting a high charge current to account for inverter draw and more effective at grabbing every watt you can. AIO units can be expected to do this, too.

I dont think I can afford 2 at the moment, I am planning for both Scc and Inverter to be Victron (bluesolar and phoenix) but I dont think they communicate directrly they need an extra device.

 

[Begginer7]

Thanks to your help I am moving forward, I ordered today one Lifepo412V 100Ah SOK battery and a 12V 1000W Giandel inverter, I want to order as well a 40A Epever Scc however I have a doubt, I am ordering the USB comunication cable to be able to setup the battery properly, the question is do I need to order the temperature sensor as well?