SOC

For me, lately, this stands for State Of Confusion.

Here's the deal this time. A few sunny crazy hot days seem like a great opportunity to stress test refrigerator and solar system. Besides, I'm really trying to understand this stuff.

First: The refrigerator is doing great! Both shore power electric and propane have maintained freezer temps below 10 and fridge has not risen above 39. And that's with measuring inside and outside pod temps above 90, albeit in the shade. Freezer is about 1/3 packed with freezer packs and 1 gallon water in fridge. I am pleased. I recently replaced OEM fan with quieter fan, added small thermostat controlled exhaust fans in upper vent and had previously replaced OEM fan thermostat with a slightly lower temperature switch. All seems to be working well.

Second: I'm having a hard time understanding electron flows!  

So, for the last few days (while waiting for another panel) I've been carefully monitoring solar panel output and battery voltage (see Renogy thread). I started with what I believe were fully charged 220Ah GC's only a year old. They have been continuously charged via Pod converter - one year old Progressive Dynamics PD4655V. PD had been maintaining batteries between "Normal" charge of 13.6v and "Storage" charge of 13.2v. When I began the solar tests, battery voltage reported 12.7v after 24 hour rest (turned off converter). I have carefully maintained battery fluid level.

Over the last few days the panels have flowed about 30Ah per day to the batteries. The panels are in full sun for about 1/2 day and report 14.7v absorption charge when cranking. That's reported by the PWM controller and confirmed by a meter between controller and batteries. Every morning, before the panels start charging, battery voltage reports 12.9v. Only thing running in Pod is fridge. I do have inverter, but it is switched. The pod did sit for a week or so not long ago without any charger and the batteries never went below 12.5v

MY SOC (State of Confusion) is: Where are all those amps going? Do the batteries just ignore them? Nothing feels particularly hot and no boiling. Why isn't the PWM dropping back to float charge? Seems like it it should with fully charged batteries.

I thought I understood that the PWM controller was monitoring battery condition and would pump in amps as the batteries needed them - like the PD4655V seems to act. I thought I could estimate how many Ah the batteries would take based on my consumption. I seem to have thought wrong. Do I really have to spend more money on that Trimetric Battery Monitor....Arghhhh.

What am I missing?

fred

Now I do remember seeing that unit somewhere. Probably would be a worthwhile investment. Still, I just can't figure out where my amps are going...

fred

But...the mystery here is that if there is that much of a phantom draw ~30Ah/day, why would my batteries hold a charge (showing > 12.4v) with no charge over a week? Remember, I said the Pod sat for a week with no charge before I started these tests. It then sat for another week with converter on. And...just overnight with now charge, I would think the bank would draw down to less than the 12.9v it's been showing.

Unless I killed the batteries the last few days, I don't understand the PWM readings I'm seeing.