Cheating the Laws of the Universe – a LOT of Amps

With our recent solar upgrade, we are able to produce much more than our charge controller can take. In fact, on days of perfect sun (full exposure, perfect angle) we need to turn off half of the array or the charge controller, which can only take up to 80A shuts off. This sounds silly, but on cloudy days, having all these panels is invaluable. So right now we’re a bit in a manual mode of turning panels on and off based on the weather.

3 years ago we had a brutal heat wave which sent us away from our house. I vowed then to have some sort of A/C capabilities before the next one. One of the nicest thing we’ve done to ourselves was getting a “regular” fridge. While at the time, it pushed our solar install to the limits, today it’s really not a big deal to keep going, even though it’s by far our biggest consumer of electrons. So we bought an 8000BTU A/C unit, I was expecting it to be maybe “a couple of fridges” worth of power consumption, but let me tell you… This thing is 7 fridges put together! Ouch!

We’ve been testing it now to make sure we won’t have any bad surprises when the heat comes.

We’ll never have the battery bank to store and supply 70A through the night. Also true, when the Sun shines, the solar panels can most definitely keep 70A coming and more. We’ve gotten good with stove heat, at managing not heat itself, but how to buffer it in the house, to buy us time through a cold night. It looks like we’ll have to do exactly that, but with cold. Run the A/C all day while the Sun gives us more energy than we can do anything with, to buffer the house as much as possible against the heat. Nights usually provide respite from heat in the Summer, in the Winter this is also true but it’s the opposite of a respite when you are fighting the cold :).

So our panels are more than enough, our storage is essentially null for the purpose of A/C, and our charge controller is too close to its limit of 80A to funnel all the panel energy to the A/C while doing the few other things we need electricity for.

I think this tells us we need to upgrade the charge controller. This way we can have a more pleasant Summer, and more specifically mitigation of heat waves.

All for free, money wise and carbon wise. Amidst these mundane concerns of solar system design to tackle such a juggernaut device as an A/C, it is easy to forget how beautiful and elegant it is that the hotter the Sun is, the more we can turn it into Cold. How often are problems their own solutions?

Compromises, Getting 70 Amps on Demand

We barely used our Champion generator these past 5 years, but it did come in handy on rare occasions. It sat for 2 years unused at one point and needed some TLC to get back going again, a fact we didn’t want another way. Working from home in the time of Covid, having upgraded our solar setup, and still not making enough power through very cloudy days, we had to compromise our values a bit more and get decent fossil based 🙁 regenerating capabilities.

I’m still gathering information on water and wind turbines to diversify down the road, but today we are not ready to pull that trigger and we need to work.

So we acquired a very nice Honda EU2200i, and a wonderful little device that plugs into it and produces 70A at 12VDC on demand.

The Honda generator is really nice and very quiet.

The AIMS Power CON120AC1224DC is very impressive, is can truly put out 70A on demand, it can be tuned to charge several battery types, and it decouples the load. I don’t need to switch the load to the generator, which means it’s always on the nice clean pure sine inverter.

The Honda generator comes with Bluetooth, a fact I was not happy about as it’s gimmicky, but I have to say it is nice to not have to go back outside to turn off the generator. The AIMS converter is definitely working it hard.


The results on the solar graph are, well, a bit absurd to look at :).

Chasing the Dip

As Murphy’s law would have it, our solar upgrade coincided with a strange phenomenon which affected us for the whole month of November. Our batteries voltage took a sudden drop every night around 9:00PM going to well bellow any usable voltage and leaving us scrambling for power through the nights.

Because of this unfortunate timing, and my lack of understanding of all things battery related. I ended up chasing this dip for weeks, trying everything under the sun isolate it. Long story short, all our AGM batteries are shot.

Years ago I bought AGM batteries because they are more self contained and don’t require maintenance (no off gazing, no re-filling them). A choice that made sense when everything was new and too much to think about. Today, I’m realizing that the flip side of this is that AGM batteries have a shorter lifetime and that there is nothing you can do about it. Sure they were no maintenance for a few years, but today they are between 3 and 5 years old and we have to replace them all (all $1600 worth of them).

I reevaluated our battery situation, and with a much better grasp of all things solar, I decided to go with regular flooded lead acid batteries, they are deep cycle, they have 65Ah, they have a port to maintain the chemicals in them.

It does mean I’ll be poking at them every couple of months to better quantify their state and not let a slow boiling voltage dip sneak up on me. And I’ll be maintaining the chemicals (mostly adding distilled water on occasion).

This conclusion was confirmed by chatting with a couple of old timers who have been off-grid for decades. One gets 6 to 8 years out of his batteries which are allowed to freeze (our situation today), the other gets 10 to 13 in a controlled environment and a water turbine providing constant power 24h a day. This helps the batteries not cycle so much.

It was a real education talking to people who have been doing this for decades. As I build my own experience, I make mistakes and sub-optimal decisions. For today though, I’ve eliminated a blind spot of our solar setup. I can recognize the phenomenon for what it is, the data I collect was really helpful and I have ideas for algorithms to interpret them automatically and get a health measure of the battery array.

So I bought only 3 new batteries, giving us 195Ah to get through night and cloud. It turns out it’s a thousand times better than where we were with our theoretical 775Ah as it had slow boiled down to pretty much nothing :). I’ll get in the habit of maintaining these batteries properly.