Recent content by agt

You can also restrict charging to only solar by setting config item 6 to “OSO” (“only solar”). Then if you see charging you can be sure it’s PV.

This turns out to be an issue also when the AIO’s inverter is operating - discovered when I forgot to turn on the input breaker after adjusting that wiring. I’ve started putting together a microcontroller to handle startup and shutdown sequencing: an esp32c3 running Micropython measures...

Ignoring the infrequent bursts, it sounds like you’re looking for (200A x .5 x 1h + 50A x .5 x 1h + 25A x 22h) = 675Ah/day or about 33Kwh/day. So maybe 36Kwh with a bit of reserve? That’s EV territory- at 140-150Wh/kg you’d get from lightest off the shelf LFP you’re talking 275kg or more for...

Further testing confirms that charging during m250 bootup will consistently trigger the DC Resistance error. I bet a fully isolated charger would be fine, but my AIO and it sounds like most chargers don’t isolate DC from AC— so I’ll just ensure the two activities don’t overlap. In other news...

I think @kundip's got me beat in terms of success & scale! Agreed. I predict we'll see plenty of used m215/m250's on the market as people update systems, but a $25 micro that's complicated and unreliable isn't such a bargain. Safe travels!

You've got it. I split the measurement into two parts - from the + mc4 connector to batt+ bus in between the batteries and main fuse; and from - mc4 to the negative battery bus. Sum of those values was 89.1mV at 9.47A, == 9.4mOhm. The remaining 50mOhm is my estimate of the batteries' internal...

I'm running from batteries (3 prebuilt in parallel) attached to an existing off-grid hybrid inverter charger. The 60mOhm figure (+/- ~40mOhm) did factor in estimated BMS and cell internal resistance alongside measured cabling, breaker, main fuse, etc. Measurements were via V drop at known...

It turns out I’d tested earlier at 200+60=260mOhm not 150+60=210mOhm. No MPPT lock at 210. At 235, I could see the inverter hunting for for a long while (~60sec) before eventually locking on; normally it’s instantaneous.

This afternoon I had some time to test operation without a "run" resistor (only the 60mOhm in my batteries/cables/etc): Envoy On? Boot R Run R Boot mOhm Run mOhm Boots MPPT Amps (DC Meter) I^2R inline Pwr Loss Watts (DC Meter) AC Amps Watts (AC VA) m250 DC/AC Efficiency Overall DC/AC Eff. N...

The SmartESS cloud monitoring (uses a dongle like this to connect rs485 to wifi) is adequate. You can monitor production, consumption, etc. and also control a few parameters remotely. I’ve heard good things about Solar Assistant which has a far richer set of data capture and control features.

I spent time this weekend testing various values for the two resistors I'm connecting between the batteries and the m250: Rboot, connected only during m250 startup and initially 4 Ohm; and Rrun, connected at all times. The following diagram depicts the path from battery to m250: I'm tracked...

From the system side of the main battery shutoff (behind which are only the batteries and main fuse), 110mOhm. That's with main battery switch open, main breaker closed, MC4 shorted, and a wire bridging the SSR. Batteries are connected in parallel: 2xprebuilt 24V (AmpereTime/LiTime) and one...

I decided to go through this itemization exercise myself to understand the role of the extra resistors I’m adding. Most values from data sheets except for the bolted connections which is a WAG. And as noted in my earlier message, there are other 24V devices operating in parallel with this...

Last night I discovered something odd w.r.t my AIO connected to the same battery bank: when AC and DC breakers are both off, DC positive (either side of breaker) and negative both show 1MOhm+ to ground. But ~20 seconds after either AC or DC is enabled and after initial AIO bootup, my meter...

Common heat sink for the 3 power resistors, then just natural convection I hope. Cutoff is relevant should the SSR die or the switch/controller fail to enable it- either way the 4W resistor might be on at 25W for an extended period. (After 3 hours @ 9.5A, the two 100mOhm resistors hit...