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The frame is an excellent way to conduct current as it has lower resistance than cable. My RV battery is connected directly to ground. Solar charge controller ground, converter ground, etc. are connected to chassis frame. Cable routings are minimized while getting better performance.

You're suggesting Vmp = 370V. With a gain of 1.5, you're up there to around 400V. But with a charge current of only 7A? The OP was thinking about 500V, 30A solar. That would be around 500/400 * 30A = 37 A battery charging current. What am I missing? How do you arrive at 52 ohm boost load?

I don't believe a boost regulator will work. It's usually used for low power outputs. The voltage gain (Vo/Vin) is limited by the resistance ratio of the inductor and the load (R_L / R_LOAD). What does the OP have in mind for solar voltage (Vmp)? Boost converter limits For a max gain of 9...

Is it wise to use a boost converter? No concerns for ground isolation? I would use a push-pull pwm converter.

Don't understand why the diode would cause much lower efficiencies. Diode drop might be 0.7V. 0.7V/80V = 0.9 % In the grand picture, that's not much of a loss.

Yes, more wires, but orders of magnitude simpler than 12V and high current. All you need is a couple of extension cords. Plug them together at the hitch.

Is it too late for another option? Run a 120V AC line to the trailer. Install an inverter in the vehicle and charge battery with a converter.

I would try a different charging source. Could try vehicle alternator charging. Connect with jumper cables. Ideal if you have a clamp current meter. Connecting a volt meter is also good to verify charge.

I looked at the schematic here. It may have been a misconception, but there is no feedforward control loop (as defined in my first post). Inverter output voltage has input voltage regulation over a 2:1 voltage span. Other than line regulation, the inverter operates open loop.

Any closed loop circuit can be either over damped or under damped. It could occur in either a feedback or feedforward loop. It's up to the designer to get it straight. After some thought, you are correct that an inverter design requires a stable dc voltage. Using one or more transformers...

Not sure I agree. You're making corrections every half cycle, at the zero crossing. That is not immediate. In a voltage sense feedback circuit the output peak voltage is measured. The correction can also be made at the zero crossing. There is no difference in delays. Feedforward does not...

Thanks for the explanation. As long as components are stable (temperature and aging), then feedforward will work well. I would feel better though if there's also feedback. Otherwise output voltage is guaranteed only under specific conditions. Feedback can also be adjusted at zero crossing...

I like to get a better understanding of your feedforward design. Are you using input current and input voltage parameters to regulate output voltage? Feedforward

0.0002 V / 50A = 4 micro ohms That's 125 times smaller than what I measured! I'll revisit my measurements in a couple of weeks. BTW, I use 847 Carbon Conductive Assembly Paste.

Increase load from perhaps 10A to 100A. Measure voltage (at busbars on both sides of a cell or the entire battery) before and directly after load change. The best way to measure voltage is with a storage scope, but eyeballing meter voltage also works. total resistance = delta V / delta I...

I'm curious how much contact resistance are folks getting. I get about 0.5 mOhm resistance.

There aren't many options if you connect to the cig port. It probably has a 10A fuse. Therefore you're limited to about 6 or 7A charging (after efficiency losses). A better option is to connect a cable with fuse to battery and charge with an adjustable dc/dc. This one is good for 20A. You...

You have a 100 Ah battery and a 5A charger. One hour of driving will charge battery be 5 Ah. That's not much.

You need a very large heatsink when one of the two back-to-back fets is turned off. Current now flows through the body diode. Using your example, 200A, divided into 10 parallel fet pairs, 20A flows through each of the 10 body diodes. According to the CRST045N10N data sheet, at 25C, 0.8V...

The primary reason for a higher battery pack voltage is to reduce current. The lower the current, the smaller the cables and less load on switching fets. The advantage goes to a 24V system over 12V. How much power does the AC and other high-power appliances require? Have you done an analysis...

That's a lot of work going to a 48V system- just because you're concerned with large currents in a 12V setup? What about getting shocked from 50V? Any reason using a 1000W inverter to convert alternator 12V to 120Vac and then to 48V? What kind of efficiency do you expect? You can get a dc/dc...

Temperature has a large impact on battery capacity. After 240 days of storage, capacity dropped by 5.7% when stored at 45 deg.C and 100% SOC. Not much difference when dropping SOC to 65% (4.9% drop) https://hal.science/hal-00876555/document "Fig. 2(a) shows that, after 240 days (8 months) of...

In general, inverter's best efficiency is at 1/3 of rated power. If your load is 2000W then a 6000W inverter will operate more efficient and have less fan noise. In addition the size of heat sinks and the number of fet switches is directly proportional to inverter rated power. In other words...

I considered putting him on ignore, but now and then I need a chuckle. Not worth arguing with someone who *thinks* he knows it all.

Don't agree with much you stated. But I do want to ask you if you played hooky the day current vs. voltage sources was taught? A battery is NOT a current source. It's a voltage source.

That's just not true. The goal of the folks in the rant is to accurately determine battery capacity. Battery capacity is measured in Ah. Why would anyone measure battery energy and then try to convert it accurately to capacity? Don't understand your second line. What does "clock up" mean...

The silver strip around the diode points towards the edge of the board. The symbol on the board shows a triangle with a line at its point. That line indicates the direction of the diode's silver stripe.

Shunt accuracy is affected by self heating and ambient temperature. It's been a long time since looking at shunt specifications, but I believe current should be derated by 50%. That means a 100A shunt should conduct 50 A max.

I don't see why you can't keep the original thermostat and just swap out the relay. The AC relay doesn't have the current rating when using dc. This relay may work. 24V 50A relay

If your fridge is on continuous then it consumes 380 Wh. That is worst case. Not sure how you get 207 kWh.

Been using a Turnigy power meter for 16 years to measure solar current in my RV. Never gave accuracy a second thought. That is, until I started measuring solar current with Cal's DIY BMS. Even though the two measuring devices displayed equal currents the Turnigy Ah measurement is constantly...

Nothing wrong with coulomb counting. It is extremely accurate. I don't get it. If the cell is rated in Ah, why on earth would you measure Wh and then try to convert it to Ah? (n) A Wh measurement is far less accurate. Not only do you have to measure amps over time, but also voltage over time...

First solar data from the BMS datalogger of my 16-year old 130W, 12V Kyocera panel. Solar current (blue plot) has y-axis to the left while solar Ah (red plot) has y-axis to the right. x-axis is time in minutes. Shown are 4 days of operation. A couple days of rain and a couple days of...

I don't like the INA219. I would rather use INA226. I ran out of INA226 and had some INA219 at hand. Therefore, by default I used the INA219. The main reason not liking the 219 is that it requires a high-side shunt location. I like to keep shunts on the ground side of the circuit. That...

I got the CAN Bus completed and installed. To the right is the ESP32 processor board. Mounted on the board is the CAN Bus transceiver SN65HVD230, an opto isolator and a power mosfet that disables fridge power in case of a thermal runaway. Signal/communication wires connected to the board...