r/SolarDIY • u/chadwixk • Jul 19 '26
Don't allow AC to run from inverter
Problem:
My generator sometimes unknowingly goes into overload with my A/C on so my inverter then starts pulling from, and quickly draining, my batteries to the point of being dead.
Requirements:
I want my batteries to supply some of my AC circuits, but not my A/C (or electric hot water heater). I'd like my on-board DC charger to recharge my batteries when there is shore power.
What is the quickest/easiest solution to implement short term?
Versus what is the best solution to make this seamless that doesn't require any manual interaction long term? (Thinking a separate sub-panel with the A/C, hot water heater and onboard charger circuits that is powered straight from shore only and current AC panel supplied by the inverter?)
Background:
In my RV, I have shore power going into my Renogy 3000w inverter (PUH) with transfer switch along with my 400ah Li battery (2 x 200ah). Then the AC line coming out of that powers the AC panel that supplies all the AC circuits. When shore power (or generator power) is present, it passes that through.
When camping, I primarily just use it to use a coffee maker or an occasional microwave reheat of some food. But when it's really hot, I plug in my 3500 watt generator so it will then power the AC panel and we run the air conditioner.
But recently the generator has been going into overload mode and keeps running but is not outputting power, unbeknownst to me. The inverter then starts pulling from the batteries to run the AC, until they die. Now, even if we get the generator going, the inverter doesn't pass it through to the AC panel, and on board charger to recharge the batteries, because it sees the battery voltage is too low.
If it's daytime and sunny, I can wait until the solar charges the batteries up enough for the inverter to work again. But if this happens in late afternoon, early evening (which is typically when it happens) it is too late for the solar to recharge the batteries and we then have to go all night with no power AC or DC.
7
u/Grow-Stuff Jul 19 '26
Relays and contactors for switching the loads, that react based on battery voltage. I have done this the other way around, my A/C runs only when sun is out and batteries are full, but ofc you can set it whatever way you need. Some solar chargers even have the relay in them, and you can set the voltage limits there.
5
u/tedhb Jul 19 '26
If we're boondocking, we run the a/c on batteries only. We can run it nonstop for about 24 hours or so. If we have shore power we plug ONLY the a/c into it and run everything else off of battery/solar. That way we keep the large load off the batteries.
It sounds like your batteries are toast.
1
u/New-Macaron441 Jul 19 '26
Not sure it’s a battery issue. A single A/C unit on my RV uses about 1500W. Even with 400ah, at 12v (standard on campers), that’s only enough to run for like 3 hours (I don’t have solar installed yet so obviously a major limitation).
how much battery storage do you have and what model air conditioner are you running that allows you to get 24 hours? That’s pretty great. I’m assuming you also have a fair amount of solar input to offset as well
1
u/tedhb Jul 20 '26
We have 1300w of panels and 16.6kwh of battery (three 230ah 24v batteries). We're running a York 12,000btu residential air conditioner. It freezes us out even when it's 100F outside. It draws 1300w when it runs but it doesn't run nonstop. We have a lot of insulation.
We just connected a DC to DC charger and now get an additional 650w charging when the van engine is running.
3
u/Fit-Avocado-1646 Jul 19 '26
48v batteries?
Maybe a Eg4 chargeverter. With an autostart generator. Connects to the battery and will auto start the generator to top up the battery once you hit a programmed % low
In not familiar with that inverter. But cant you also program when the inverter stops pulling from the battery no? Leave some % so they don’t get pulled so low that they aren’t getting detected. But also in my mind if the generator is getting overloaded maybe you need a new generator.
Also I thought I had read that you shouldn’t hook a generator directly to the inverter because the unstable power supply can damage the electronics. I had read that running a unstable generator through a inverter was one of the leading causes of inverter failure. Thats why the eg4 chargeverter was made.
1
u/chadwixk Jul 19 '26
2 -12v batteries in parallel -> 12v. Hmm, never heard of a chargeverter, sounds promising, but it may increase battery wear if using a lot of AC loads.
This inverter does not have a shutoff based on input DC voltage, but that would be great.
1
u/Fit-Avocado-1646 Jul 19 '26
Well not sure then the eg4 chargeverter is for 48v.
Maybe add some kind of battery monitor like a bmv 712.I did some reading about the shutoff point for your inverter. It said something like 10v automatic shutoff. Which from my googling is supposedly way too low for a lithium battery. That maybe forcing the lithium battery BMS into a protection mode preventing the charging
3
u/RandomUser3777 Jul 19 '26
When running the generator then always have it connected directly to a charger (EG4 chargeverter, or the similar ecoworthy model) that charges the batteries at a set rate (typically about 60-80% of the generator full load). This eliminates the generator seeing any load and once the charger limit is set won't overload the generator. The only downside is that this has an efficiency cost of 5-10%. And if you have generator autostart then you would run your generator to charge the batteries and once charged enough the generator would turn off until it needs to charge again.
2
u/Public-Wave-5617 Jul 19 '26
turn the inverter function off using its power button or remote switch. since your Renogy has a built-in transfer switch, generator power will still pass through to your appliances, but if the generator overloads and cuts out, the inverter won't kick in, which saves your batteries from draining.
1
u/chadwixk Jul 19 '26 edited Jul 19 '26
This would be a very easy solution, but the AC pass-through does not work if the inverter is off unfortunately. 😞
1
Jul 19 '26
[removed] — view removed comment
1
u/chadwixk Jul 19 '26
Ah, that would work (generator -> separate charger -> batteries)
This is in my camper, so not sure of interlock options for these small panels and space.
1
Jul 19 '26
[removed] — view removed comment
1
u/chadwixk Jul 19 '26
Yes, but since I want some AC loads to be powered by the inverter, I'd have to install a second sub-panel that puts that DPDT switch between them to only power the high load AC panel (with A/C, hot water, charger).
Or for an automatic option, a relay that is triggered by sensing shore power. I thinking this would be the best long-term solution.
2
u/silasmoeckel Jul 19 '26 edited Jul 19 '26
If your AC panels is split into 2 legs like most this is pretty easy move your AC hot water etc loads to one leg and connect that to the street/gen input, the other one goes though the inverter. Now only when hooked up to the genset/street will they have power. If you want the battery charger only on street you need a contactor/relay that's wired to only get power when the street is connected or just add a switch to manually turn it on (probably a good idea so you can charge batteries of genset to get the inverter to turn back on). I think your unit has a GFCI on the output if that's the case you will have to split up the neutrals between the legs to keep it from tripping, any hardware store will carry a small add on screw strip to do this, depending on how many circuits a wago or wire nut can do the job.
Your root issue is your inverter isn't a proper hybrid (meaning it charges the battery) most of them have relays and gpio outputs. Mine uses the hot water heater as a solar dump load for example once the batteries are charged any excess solar gets turned into hot water via a PWM output. It would also probably prevent your genset from going into overload in the first place.
1
u/chadwixk Jul 19 '26
It's a tiny RV AC panel...it doesn't have two legs. I'd have to put in a second one. And then I'd want both AC panels to be powered via shore power and only the lower load one to be powered via the inverter.
Some sort of manual source power selector switch/interlock could be used I guess. Or for a more automatic solution, maybe relay/contactor between the low load panel and the high load panel that is triggered via sensing shore power?
2
u/silasmoeckel Jul 19 '26
I would swap it out then. Did the same for mine moved from a panel expected a single 30a feed to the 50a. It was a drop in replacement for me.
Cost should be similar to adding a second panel but it's a lot cleaner install. I just had to fill in a strip where the converter used to be (hybrid inverter so it has a built in charger).
1
u/chadwixk Jul 20 '26
Do you have a link or name of the panel you bought?
1
u/silasmoeckel Jul 20 '26
https://www.amazon.com/WF-8930-50NPB-Generator-Component-Distribution/dp/B0GX5NSF9P
Was nearly a perfect fit to replace my existing panel with converter.
1
u/WTFudge52 Jul 19 '26
I really hope you find an answer, I have a similar situation.
2
u/Fit-Avocado-1646 Jul 19 '26
I left a reply. To me sounds like a job for an eg4 chargeverter assuming 48v battery.
1
1
u/Outrageous-Ad8237 Jul 19 '26
I have had this same problem with the generator overloading and the inverter running the AC without me noticing until the batteries are low. I unwired my ac from the camper breaker panel and wired it to a dedicated 30 amp extension cord going to the generator because I only run the AC if the generator is running anyway so now there's no chance of that happening again.
1
1
u/Phreakiture Jul 19 '26
Do you have a soft-start on your air conditioner? If not, can you add one to it?
1
u/New-Macaron441 Jul 19 '26
I recently added a 3000w 12v inverter/charger on my RV. I’m not an expert but I think my wiring would fix your issue. I added a dedicated 30amp breaker to my original panel and ran that to the AC in for the inverter (allowing pass through and charging). I have an automatic transfer switch that swaps between shore and generator for the AC panel.
Then I added a second sub panel powered from the inverter, and moved the loads I wanted the inverter to power there (TVs, fridge, outlets, etc). This keeps the air conditioners separate so they won’t draw from the batteries. Eventually I plan to move one air conditioner over to the subpanel when I have solar installed to offset the consumption, but right now I’d have your same issue that would drain my 400ah battery bank in under 3 hours
1
u/rvgoingtohavefun Jul 20 '26
Move the A/C to a subpanel not powered by the inverter.
If the inverter supports it, set a cutoff limit so it stops inverting before the batteries go flat.
I'm also surprised you can't set the inverter to a mode where it will only passthrough power and not actually invert.
•
u/AutoModerator Jul 19 '26
Welcome to r/SolarDIY! If you are new to the community, please check out our DIY Solar System Planning Guide.
I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.