stress testing the power system

After yesterday’s stress I need some comfort food. So I’m making rice pudding and fried rice using slivers of the strip steak I had the other night.

poor sun exposure

The new spot appears to be mercifully mouse-free but the sun exposure is the opposite of what I want. Before I had full sun until 1-2pm; the bank was topped off before it got hot.

The new spot is shaded until ~noon, then has full sun until ~3pm. So sun only when it’s hot. :-(

starting line

This morning the bank was at 50% SoC and I was only collecting ~55w between the tree leaves.

rice pudding

3.5hrs @ 90w = 315Wh

reheating leftovers from lunch, cooking rice for tonight

I reheated some potatoes and pork loin for lunch. Then cooked rice using the RICE preset (a low-pressure mode).

I forgot to reset the meter between them so I only know it took 160Wh for both.

making progress with charging.

During the rice cook the bank’s SoC hit its lowest point, 39% SoC. The voltage sensor said the battery was sagged to 12.77v. I figured the the lower voltage from weak solar contribution and heavy load would make a good test for the alternator charging setup. I cranked the engine (still no codes!) and observed a +53A at the battery bank. That is higher than my previous highest observation of 44A when charging eh 220Ah FLA bank. 53A into a 150Ah bank is 0.353C.

After the IP shut off the system started charging at ~360w (net into the bank after servicing background loads and the crockpot of rice pudding).

The rice pudding will be done ~1:30p, which will free up ~90w more for the charging effort. Sometimes I can back off to LO (60w) after the contents boil but there are 4c of milk in the little crock so it will likely boil rather late.

Will we make it to ~100%? Solar noon is at 1:05pm here and If the present sunlight continues we’ll see the 45A controller pretty close to maxxed out. Straight math using existing harvest says we hit 100% around 2:30p, just before we lose full sun. So it’s a crapshoot.

• 1122 - 44%
• 1132 - 47%, but some high cirrus clouds have decreased harvest a bit. This pushes the ETA for 100% back to 1140….

Ok, went to a clearing to walk Muffin and get a better look at the sky. The cirrus are creeping slowly and extend windward to the horizon. At the horizon there appears to be heavier clouds. Hopefully they arrive after local solar noon so I get some time at max power…

• 1143 - 50%, making more power so ETA at this rate 1412. Gotta beat those clouds…
• 1159 - 55%, ETA 1415.
• 1224 - 63%, ETA 1410. If the rice pudding would boil I could cut it back and get ~3A more charging…
• 1258 - 75%, ETA 1412. Will make it to local solar noon 1305 without clouds but patch clouds will start hitting shortly thereafter. Crockpot now on LO.
• 1305 - 76%. Looks like ~574w will be the effective max today, ~41.5A @ 13.55Vbatt. Vmp is quite low, 25-26v due to heat and minimal cooling breezes. That’s -16% just because of cell temperature. Today is the hottest (80F) and will drop again tomorrow.
• 1323 - 82%. No clouds have reached me yet but shade is creeping up faster than I thought on the rearward panel. I should see a dropoff shortly. Luckily the rice putdding is nearly done.
• 1325 - 84%. rice pudding done.
• 1415 - 91%, shade encroaching on rear panel. Only one cloud every passed over this position.

finish line

Ok, we hit the wall at 3pm at 95% SoC when shade started getting serious. At that point the system had made 1.96kWh.

The difference between this kind of game with lithium vs lead is it’s a fun guessing game with lithium, and stressful with lead.

update

next dayp; moved the van about 6’ forward and am getting about 1.5hrs more full sun. 10:30am instead of noon. :-)