Renogy 3000W Inverter Running Hot & Humming?

May 18, 2025 6:23 pm

This is an very long reply, I hope you have the time to read it all.

First, never EVER run an inverter that is not grounded. Your inverter is connected to very powerful batteries and YOU do not ever want to become the source to ground. If you are lucky, becoming ground will just feel weird but you can get burned, have permanent nerve damage, lose body parts (fingers or toes being the most common), or death. You have two 200ah batteries that likely have 200 amp BMS's, if you are lucky the BMS has overcurrent protection that actually works. There are many cheaper batteries (and some not so cheap) that either do not have overcurrent protection (even if they claim it does) or faulty overcurrent protection. The overcurrent protection on a 200 amp BMS should be at about 250 amps, if it is a feature of the BMS and working correctly. EG4 batteries have been independently tested (by multiple groups) and shown that their BMS's overcurrent protection properly works. Your two 200ah batteries in parallel can therefore output at least 250amps each or 500 amps. You do not want to risk 500 amps traveling from your hand to your feet, with the path going through your heart.

The cable size is WAY WAY to small. You need at least 4/0. I use an inverter efficiency of 80% because that is most reasonable at low power usage and very high power usage and should account for inverter self consumption. The efficiency ratings on most electronic devices as the PEAK efficiency. Some offer graphs to show actual expected usage. The 80% might be a bit low, but it's better to be conservative. It is important to remember that NO electronic device is 100% efficient. Another way to state that is that all electronic devices require more power input than output with the difference converted to heat. If you want X watts out, then you need X + Y watts in, with Y being power losses. This concept is very very important to remember when dealing with solar power.

Math:
Inverter / Inverter Efficiency / System Voltage = Maximum Amperage at 25C/77F
3000 watts / 80% / 12v = 312.5 Amps

I then use an online calculator to help determine cable size.
https://www.omnicalculator.com/physics/dc-wire-size

At the very minimum, you want no more than a 3% voltage drop. I try to use a 1% voltage drop cabling. This helps ensure the highest efficiency possible, even when connectors, bus bars and multiple cables are involved.

Using the calculator, even with a 3% voltage drop and 2 foot cables, one way, gives a resulting cable size of 500Kcmil or 19.05mm2. For reference 4/0 cable is only 211.6Kcmil or 11.68mm2. 1/0 cable is only 105.5Kcmil or 8.251mm2.

If we lower the amperage by 50%, it would require at least 2/0 cable. This means using two 2/0 cables would be the very minimum required. For best safety, two 3/0 cables should be used.

3/0 cable is 211.6Kcmil or 10.4mm2 times 2 = 423.2Kcmil or 20.8mm2 total.

If you want to build it to code, then you must also take ampacity into account. The code states that ampacity = maximum amp load / 80%. In your case 312.5 / 80% = 390.6 amps.

Using 390.6 amps to determine the breaker size means that you have to decide to go under 390.6 amps or over. Depending on your location, they may require that you go with the value of the breaker that exceeds that value, which would require that the cable also supports that. Other places may allow you to go to the size lower. The most common size DC breakers in this range are 350 amps and 400 amps.

350 amp breaker will require 500Kcmil cable.

400 amp breaker will require 600Kcmil cable or 20.57mm2

If you chose 400 amps ampacity then two 3/0 cables is just barely large enough. If you are getting your system permitted, I would contact your county and ask if they require two 3/0 cables or two 4/0 cables.

500Kcmil copper cabling is very expensive, which is why it's better to use two cables. With two cables you MUST ENSURE that each cable is the same length. Copper cabling this size is so expensive that in most applications Aluminum cables are used instead. The problem for you is that Aluminum requires much much bigger cables for the same ampacity. 400 amps requires 1000Kcmil or 26.67mm2 which you won't be able to fit onto your inverter.

In my opinion, 3000 watt inverters for 12v systems should be illegal as they are just too dangerous. Very few get installed with proper cabling. One of the few things that I can praise Victron for is that they have very few high capacity inverters and most of the time installers push their 12/3000 product. Victron (I believe for marketing reason, another way of saying greed) rates their products in VA (Volt-Amps), their PF (Power Factor) rating is 80% which means that a 3000VA inverter is actually only a 2400 Watt inverter. Most people buying Victron inverters think they are buying a 3000 watt inverter (and I think that many installers either lie or never read the spec sheet). 2400w / 80% /12v = 250 amps (a 4/0 cable), if cabling by code then 250v / 80% = 312.5 amps. This means that their 12/3000 can be installed using a single 4/0 cable if a 250 amp breaker is also used as long as you realize that the breaker may trip if the inverter is maxed out.

I have a feeling that if you are using your inverter without the ground, you likely are also not using breakers and/or fuses. It is important to realize that without these protection devices, high amperages will cause the insulation of your cable to heat up. Once it gets hot enough the insulation will catch on fire. I assume that you agree that fires are bad. This is why the code has ampacity. It is a way to give a buffer between the rated capacity for the insulation.

The cable will have a certain insulation rating, most commonly for DC it is a temperature of 77C/167F which is the maximum temperature that the insulation can handle before melting. The cable will also have a resistance value, which is per unit of measure (feet or meters). This is why you want to use cable as short as you can safely install. Cable with sharp bends will have localized high resistance at the bends. Once the insulation starts to melt, it increases the chances for arcing to occur between the cable and any metal nearby. Nearby is determined by how much voltage there is. An arc can cause any flammable materials to catch fire.

As the amperage that the cable carries increases, something interesting happens. The cable resistance causes heat. As the conductor's temperature increases, the resistance of the cable increases. The higher resistance than causes more amperage. This is why using too small cabling is so very very dangerous. It is important to understand that the insulation rated temperature is based on an air temperature of 25C/77F. If the air temperature is higher than that, the amount of current required to melt the insulation is lessened.

Breakers and fuses are to ensure that the insulation temperature is never exceeded.

Your next issue is that your 3

400 watts of solar panels is generally considered a trickle charge. Depending on where you are located, time of year, and how the panels are mounted, you may only get 75% of rated power, or 300 watts. You then need to consider location and time of day to find out how many solar hours you will have. Solar hours are how many hours of significant solar production. Just because it's daylight doesn't mean that the sun is providing a good amount of power at your panels. In the morning and evening, they angle of the sun will be very low to the horizon, probably to low for the angle of your panels. Additionally, the sunlight must travel through much more of the atmosphere.

There are many things that can reduce the amount of solar power.
1. Clouds, even very thin clouds will cause shading
2. Particulates in the atmosphere, this could be smoke from wildfires, dust, pollen, etc. Fog, mist, rain and snow.
3. Distance the sun travels through the atmosphere
4. Shading from trees, buildings, or anything else that can shade the panels

5. Dirty solar panels, clean them regularly with mild soap and water, rinsing with as pure water as possible. If your water is "hard" (lots of minerals) then after you rinse the panels, the water will evaporate and leave the minerals on the panels.

6. Temperature, specifically the temperature of the solar panel cells. The solar panel cells can be much higher than air temperature.

The first 5 all are forms of shading, even if it's less obvious than a tree casting a dark shadow on the panel. They all, to some extent block sunlight from hitting your solar panels.

The last one is that you may or may not be able to control. In order for the solar panels to do their job they must be in direct sunlight and to a lesser degree indirect sunlight. Anything in the sun will get warmer. If you look at the specifications for your solar panel, they will list all ratings based on 25C/77F. They should also list the temperature coefficients for voltage and amperage. This is how much the rated value changes per 1C. This is why you must ensure that your string of panels' Voc (open circuit voltage) is adjusted based on the minimum temperature that they will be in. Normally the minimum value use is -10C/14F, which is only applicable for southern states (but not the high country). If the panels are installed in a fixed location, you should look up the record low temperature in the past 100 years to find what value to use. In an RV you should assume that either you or the next owner will end up in a situation with the RV in very low temperatures, at the minimum use -40C/-40F but -50C/-58F or even -55C/-67F may be more appropriate. Alaska, Canada, the Cascade Mountains, the Rocky Mountains, areas such as the Montana, the Dokotas, Minnesota, Wisconsin, Michigan and the far North Eastern states can get very very cold. Many years ago, I lived in Idaho Falls, Idaho. There was a two week period where the high temperature never exceeded -40F (not including wind chill), that was considered a 50 year low temperature (basically those temperatures are expected to happen at least once every 50 years). If I had solar panels back then, I would have needed to calculate Voc based on at least -45C (-49F) if not -50C/-58F.

If you will be in hot areas, then your panels will have lower voltages, but higher amperage (important for cable size calculations and to ensure that the string amperage does not exceed the capabilities of your solar charge controller). Almost always, higher temperatures means less wattage. Installing your solar panels so that they get the best ventilation possible is important. Airflow over and under the panel will help remove heat from the panel's cells.

Now that I've given a basic understanding of why you will likely not receive production wattage that you may be expecting from the panels specified wattage and that you will be producing that wattage for less time than you may be expecting we can discuss how much power you may be able to produce.

In the very best of conditions, in the southern US during summer, you may be able to get 80-90% of rated power (perfectly clear sunny day with the panels mounted at the optimal angles for the time of year and location). I'll be nice and say 90% of your 400 watts, or 360 watts. I will also be nice and say that you produce that 360 watts for 10 hours a day. This means that your total production is 3600Wh per day. You may think that that is perfect, as your batteries only store 5520Wh. You will then assume that if you use 3600Wh overnight, that the panels will recharge back to 100% during the day. The first issue is what happens if you end up using 3800Wh overnight which means that every day you will be missing 200Wh from the batteries? After 27 days your batteries will be drained.

It also means that you can't use any power during the day. The amount that you charge is not how much the solar panels produce, it is how many watts the solar panels produce, minus the losses from the solar charge control, minus your load.

If we assume that the losses from the solar charge controller, while charging is only 50 watts, then it will only output 310 watts to your batteries. This means that you only have 3100Wh per day. What happens if you use an average of 200 watts of load? Now you take 310 watts minus 200 watts, leaving 110 watts or 1100Wh per day of charging. If that 200 watts of load is based on the AC side of your inverter, now you have 250 Watts of load on the DC side. 310 watts minus 250 watts is 60 watts, or 600Wh of charging per day. Remember, that these numbers are the absolute best case.

The farther north you are, the less efficient the solar panels will be and the number of solar hours decreases. In the winter, the value can be very very low. In the northern states, like Washington, winter solar hours can be under 2.5 hours/per day. Winter also tends to bring storms (clouds).

As an example of how bad it is. I live in western Washington. I currently only have two strings of solar panels. String #1 is 1820 watts and String #2 is 1200 watts. They are installed on my 5th Wheel. On Dec 1 I disconnect my solar panels until at least late February, but this year the winter stuck around and I waited until May 5th to reconnect them. By experience, I know that in my location during those times my 3020 watts of solar panels will only produce about 500wh on a sunny day, except where I live is cloudy almost every day from Dec 1 (actually the end of November) until at least the end of February. During that period, I am LUCKY to produce 300wh per day. The solar charges self consumption exceeds those amounts. This means that if I do not disconnect my solar panels, they cause a net drain on the batteries.

This past week (week of May 11 to May 17) another set of storms came through and it's been mostly to fully cloudy all week, with only a few short periods of sunlight.
May 11: 1.7Kwh
May 12: 1.4Kwh
May 13: 1.6Kwh
May 14: 1.3Kwh
May 15: 1.6Kwh
May 16: 1.4Kwh
May 17: 1.2Kwh
Total: 10.2Kwh

That production of 10.2Kwh does not include the solar charge controllers losses.

One year, I had a small solar setup. It had a 12v 240ah (3312Wh) battery, a small solar charge controller and two 100 watt solar panels. Between Dec 1 and the end of February I had to use an AC battery charger to recharge the batteries back to 100% 3 times during that period. The only thing running was the solar charge controller, the inverter, DC lights, and DC fans were turned off. On a sunny day, it would produce about 25Wh of power, on a cloudy day 2-3Wh of power PER DAY. This means that that solar charge controller's self consumption was about 100wh per day.

If you use your inverter with maximum load it will be 3000 watts on the AC side and about 3750 watts on the DC side (remember the input must always exceed the output with the difference becoming heat). If you start with the batteries at 100% SoC, in 88 minutes they will be at 0% with no outside charging. If you run your inverter with best case solar production, you can subtract 310 watts (400 watts solar panel, 90% production and 50 watts of solar charge controller self consumption) from the 3750 watts load. The batteries will supply the other 3410 watts. If your batteries are at 100% when you start, after 97 minutes they will be at 0%.

I realize that you are likely not going to often (if ever) have 3000 watts of AC load on your inverter. I don't know what you plan on powering. I can say that I doubt you bought a 3000 watt inverter to power 200 watts of load. Let's look at how your system may perform, using various common loads.

1. A 1000 watt microwave for 10 minutes. An average 1000 watt microwave draws about 1500 watts. The 1000 watt rating is it's heating power, not it's required power. That 1500 watts will require about 1875 watts from the DC side of the inverter. Running it for 10 minutes is about 187.5Wh.
2. A 1875 watt hair dryer (the most common size. you can find mini hair dryers that use 1500 watts). It will require about 2340 watts on the DC side. If the hair dryer is used for 10 minutes, that is 234Wh
3. An LCD TV might use 100 watts or 125 watts on the DC side. If the TV is on for 8 hours that is 1000Wh. A larger TV can use more than 100 watts.
4. A low power laptop might use 30-45 watts or upto 60 watts on the DC side. Over 4 hours that is 240Wh
5. Old lightbulbs used 40 watts, 60 watts, or 100 watts each. Hopefully you are using LED lightbulbs now. These can use between 5 and 10 watts each. or about 6 to 12 watts on the DC side. It may not sound like much, but it can really add up over a day. You may have a sink vanity with 5 lights, that would be 60 watts. If it gets turned on and is not turned off for 10 hours that is 600Wh for that one light switch.
6. Coffee maker. This is hard because there are so many different coffee makers with wildly different power draws. A small one without fancy features may require 700 watts, or 875 watts on the DC side. I'd guess about 80Wh to brew the coffee, and then maybe 300ish Wh per hour to keep the coffee warm. If you keep coffee warm for 2 hours that could be about 700wh. If you brew a pot in the morning and one in the evening that may be 1400Wh
7. Phone Charger. This is also difficult because how many watts are used for charging depends on the model. If we assume a new higher end model it can superfast charge at 45 watts. If you use the AC plug to charge, that plug might need 60 watts and then the DC side would be about 110 watts. If you have 2 phones charged once a day, that could be 150Wh to 200Wh (I'm assuming less than an hour per day per phone to charge). If you leave your phone on the charger after it is full, the wall plug may continue to use 5-15 watts of power.

In my experience with RV's, when a residential refrigerator is installed, they will typically offer about 400 watts of solar which they claim should be enough to power the refrigerator for up to 10 hours of travel time. The assumption is that you will then plug the RV into shore power at a campsite. These RVs typically come with two 12v 100ah lead acid batteries with an usable capacity of 1280Wh. My guess is that they assume that the solar panels will provide 1600wh during the 10 hours, but they must also account for the fact that travel time may be on cloudy days or even at night. I have no load checked my home refrigerator to see how much it consumes. I am thinking that they are assuming 100 watts or less; probably 60-80 watts. If the total load on the batteries during the 10 hours of travel is 100 watts, that would mean that the batteries are down to about 280wh capacity which isn't enough. If the total load is 60 watts, that would be 600Wh over 10 hours, meaning that the 400 watts of solar should cover all or most of that even on a partially cloudy spring, summer, or fall day.

With how small your system is, you definitely need to consider parasitic draws. Look at every device you connect to power, if it has WIFI capability, and especially a screen, it will draw power even when "off". Many electric devices "off" is actually "standby". This applies to your TV, radio, electronic thermostat, etc etc. These draws may be minor, but because it's 24/7 and can be several devices, it can add up.

If your microwave draws 3-5 watts to power it's circuit board and display, that is 72Wh to 120Wh per day. The DC side will require 90Wh to 150Wh. TV's may use 10-15 watts while in "sleep" mode. On the DC side that can be 300Wh to 450Wh. I suggest that you go into the settings for the TV and disabled what might be called "fast start". Fast start places the TV in sleep mode when you hit the power button. With the setting disabled it instead puts it in standby which may only require 3-5 watts (72h to 120Wh per day). It will require a few seconds for the TV to "boot" when you power it on. If you, for some reason turn the TV off and on many times a day, then use the sleep mode.

Even an LED indicator on a power strip may be 0.5 watts or about 15Wh per day.

Like I said, they are all small loads, but over 24 hours and with multiple devices it can really through off your calculations. Most households will easily exceed 1000Wh per day just in such parasitic loads.

You will also want to power as much as possible directly from the batteries. Install USB outlets that use 12Vdc and install 12Vdc auxiliary plugs for other DC loads. Any device that uses 12Vdc will have almost no losses. The losses for high power USB devices using 12Vdc is much less than using a 120Vac outlet. You may be surprised by how many devices use a 120Vac plug, then convert that to 12Vdc. Internet routers are a good example. You can buy the correct DC plug and run a fused cable to your batteries to save on those losses. Many of the power converters used by these devices at only 50-60% efficient (because they don't care). A device that uses 10 watts, may draw 20 watts of 120Vac. Then your inverter may use 25 watts from the batteries. Using a device that draws 10 watts from the batteries is much better than the same device that requires 25 watts because of two conversions.

One last thing. Many times people will recommend that you use welding cables for your inverter and batteries. They will claim that you can use much smaller cable sizes. These people do NOT understand the concept of "Duty Cycle". Welders commonly have duty cycles of 10-25% (the industrial welders with high duty cycles use appropriately sized cables). A 10% duty cycle may be defined as using the welder 1 minute in a 10 minute period. A 25% duty cycle may be defined as 5 minutes in a 20 minute period. If you go back to my discussion on cable insulation temperature ratings, this will make more sense. An inverter is assumed to be a 100% duty cycle device (in other words, always being used). This is because you don't go around and turn on the devices you want to be powered, and then a couple minutes later turn them off and then wait several minutes to turn them back on. Welders you do often turn on an off. You weld a section, stop to relocate, check your work, or get a new welding rod and then start welding again. What this means is that you can run a much higher current through the cable without melting the cable and then the cable has a period of time to cool off. Better welding cables also have a higher insulation temperature rating. These might have a rating of 194F or 221F. If you use welding cables with these higher insulation temperature specification then you can definitely adjust the cable size requirements. The link to the calculator I provided at the top of my post allows this. Just realize that even a 194F rated cable can not handle the full load of a 12v 3000 watt inverter. When people look up the amperage specifications of the welding cable, they do not realize that they include a much higher voltage drop than you want with an inverter. Welders don't care about voltage, they care about amperage. You can find welding cable that says that it supports up to 350 amps at up to 100 foot using 1/0 cable. Often the voltage drop will be 10% or higher.

I'm not the police, I won't show up at your house and force your to re-cable your system. I just want you to be safe. Saving a few dollars is never worth a persons life or a fire.

I've seen RV's that had an RV company install an upgrade solar system. Many of these companies are not used to the cable size requirements. They are used to using 4 awg cables to the batteries. I saw one person that had 1/0 awg cable going to their 3000 watt inverter, but then only 1 awg cables between their batteries. The couple bought very expensive equipment. They had Victron inverter, solar charge controllers, battery monitors, etc. They bought BattleBorn batteries (way overpriced in my opinion). They had ten 12v BattleBorn 200ah batteries cabled in parallel. They did it, what I call the "old fashioned" way. Where the batteries are wired directly together, with the first battery supplying positive to the inverter and the last battery supplying negative to the battery. This is done to help ensure that each battery properly shares the load. I always recommend that any battery bank over 2 batteries use bus bars to connect in parallel (I personally always use battery bus bars). The bus bar then handles the full load from the inverter, but the cables for the batteries only have to handle that battery's share. If you have a 300 amp draw and 10 batteries, then the battery bus bar will have to handle 300 amps, but the cables to the batteries will see on average 30 amps each. When you cable the batteries the "old fashioned way", the cables are the bus bar. This means that if the inverter is pulling 300 amps, each battery cable must pull 300 amps.

This couple normally only ran their air conditioner for an hour, maybe a bit more a day. Just enough to help make it bearable. They didn't camp in really hot areas. They liked to camp with an air temperature of 80F or lower. This day, they turned on the air conditioner, and went to their neighbor's campsite to talk with them. Their neighbor was a couple that they'd had ended up camping near several times over the years, but never planned. Because they were talking about the places that both couples had been at since the last time they had met up, they lost track of time. A couple hours later they returned to their RV. When they entered, there was no 120Vac power. He went to his battery compartment, and before opening the door smelled the burnt cabling. He was very lucky. One of his 1awg battery cables failed and the cable broke. So although the insulation on several battery cables showed signs of melting, this one cable faired worse, but instead of catching fire or sparking it melting the actual copper. This was very lucky and very rare. It was lucky because as soon as the cable melted, it caused no power available to the inverter. He had 2/0 cable running from the Victron 12/3000 inverter to the batteries. When he replaced his batteries with the BattleBorn he had an RV shop install it and they only used 1awg between the batteries. He had assumed that it was installed correctly by "professionals" and it was a recent upgrade, so he didn't do his "monthly inspection", he is a full time RVer. He hired a mobile solar power technician that specialized in RV's to fix his issue. That tech explained how all of his cabling was undersized. This tech ran 4/0 cable from the inverter to the a set of new battery bus bars and then 2/0 cables from the battery bus bars to each battery.

As he was telling me the story, he showed me his battery compartment. The installer did a beautiful job of installing and routing the cables. I pointed out a big issue that was still missing. I explained that even though he had a good 2 pole DC breaker for the connection between the inverter and battery bus bars, he still needed a 2 pole DC breaker between the bus bars and battery. Unless you want to know why, I'll leave that out as this is already a huge post.

I hope this helps and doesn't overwhelm you. I tried to be as simple as possible while still providing enough details so that you can see the importance of what I'm telling you. I also don't know what your goals are nor your budget. I will say that if you are planning on doing anything more than something very basic you should consider upgrading.

I can not recommend EG4 enough. I have two EG4 6000xp hybrid inverters in parallel and six EG4 LL-S 48v 100ah batteries installed in my 5th wheel. I can safely use my inverters to power 240Vac 50 amps for as long as my batteries hold out. The features and quality are top notch.

And a surprising note, as I finished writing this, I looked over and was surprised to see that my system is currently producing 1000 watts from solar. For the location my 5th wheel is currently in (partial shading) and it's still not fully sunlight because of the stormy week, this is actually pretty good and the best I've seen this year, as I haven't gone camping yet. In fact my solar panels are shaded enough that my string voltages are extremely low. String #1 at 130.4v and String #2 at 158.4v. This implies that string #1 has about 8 fully shaded panels and string #2 has about 4 fully shaded panels causing string #1 to be producing 508 watts out of 1820 and string #2 to be producing 409 watts out of 1200. String #1 is 14 Ecoworth 130 watt flat panels, string #2 is 12 Renogy 100 watt panels.

Question Renogy 3000W Inverter Running Hot & Humming?

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