Inverter problems

[Vrad]

Question:

Does anyone else have a problem of their inverter running their batteries to empty at night? We just finished building and have been living in the bus for a few weeks. Our solar can charge the batteries up to 100% during the day.

We have:
4 400wh solar panels = 1600wh total
4 300ah batteries = 1200ah, 14,400wh
And our inverter is an expert power 3000w inverter that does 3000 w continuous and 9000 surge

The batteries are all the same type were bought at the same time and charged to 100 before being hooked up.

At night our inverter runs only our fridge (297kwh/year) and potentially (it hasn’t yet because we’ve been having issues) charging our phones and running a window fan. We’ve only had it running the fridge everything else is off/unplugged.

We don’t know much about wiring and electric work, but we did have an electrician look at it after we got everything wired. And he said it looked great.

Could it be that it is getting to hot? Would that cause an issue?

[HamSkoolie]

Originally Posted by Vrad

Question:

Does anyone else have a problem of their inverter running their batteries to empty at night? We just finished building and have been living in the bus for a few weeks. Our solar can charge the batteries up to 100% during the day.
We have:
4 400wh solar panels = 1600wh total
4 300ah batteries = 1200ah, 14,400wh
And our inverter is an expert power 3000w inverter that does 3000 w continuous and 9000 surge
The batteries are all the same type were bought at the same time and charged to 100 before being hooked up.
At night our inverter runs only our fridge (297kwh/year) and potentially (it hasn’t yet because we’ve been having issues) charging our phones and running a window fan. We’ve only had it running the fridge everything else is off/unplugged.
We don’t know much about wiring and electric work, but we did have an electrician look at it after we got everything wired. And he said it looked great.
Could it be that it is getting to hot? Would that cause an issue?

Insufficient information.


What voltage is your battery bank? We can assume 12 volts because you also list 14.4kWh and it probably is but it is a needed variable.
What technology are your batteries? Lithium, AGM, SLA, FLA? it matters.


You either have a massive draw that you aren't aware of, it's not wired properly for the particular unit and design, or you have a defective unit. You could also have blown diodes in your solar panels which would allow the reverse flow of energy in non lit hours.
With your self recognized lack of electrical knowledge I would suggest have an electrician check it out while operating and do the trouble shooting. It will cost some money but most likely save you time and money in the long run.... not to mention being safer for you.

[kazetsukai]

HAM asks all the right questions. ^



My thoughts:

If its 4x 12V 300Ah batteries, regardless of what the bank voltage is you've got 14,400Wh. If that's lead acid / AGM, only 50%, or 7200Wh is usable. For you to deplete that overnight you'd need on average a constant draw of something like 600W-900W.


How are you measuring battery depletion? What behavior are you seeing? Do you have a battery monitor capable of showing draw (like: https://www.amazon.com/gp/product/B07RP5B5P7 )? If so, what does it show at night?

[HamSkoolie]

Originally Posted by kazetsukai

HAM asks all the right questions. ^



My thoughts:

If its 4x 12V 300Ah batteries, regardless of what the bank voltage is you've got 14,400Wh. If that's lead acid / AGM, only 50%, or 7200Wh is usable. For you to deplete that overnight you'd need on average a constant draw of something like 600W-900W.


How are you measuring battery depletion? What behavior are you seeing? Do you have a battery monitor capable of showing draw (like: https://www.amazon.com/gp/product/B07RP5B5P7 )? If so, what does it show at night?

Thanks,
Amp hours (ah) aren't a variable that means anything by itself (I'm sure you know this). It's amp hours and voltage that will give you WATTS and WATTS are the only way to truly look at electrical usage because they are are constant units of "work done" regardless of voltage, amperage, or resistance.
I teach electrical for HAM radio operators and we go through Ohm's law in depth with the V over i * e and P over i * e equations. So often I hear people talking about their battery banks in amp hours without mentioning battery chemistry or voltage and without that there is simply no way of knowing how much power is truly available.
For instance, I have two, 200ah batteries. Okay I have 400ah....but how much is REALLY there and useable?
Well they are 24 volt batteries so 200ah equals 5.12kWh
Because they're Lithium I can use every bit of that power though if I only go to 80% depth of discharge I have 4.1kWh EACH and they are guaranteed 10 years and 7000 cycles to that 80% (and still have 80% of original capacity). 7000 cycles at one cycle per day is 19.5 years.
With two batteries I can use 8.2kWh of battery every day for 19.5 years. Since the large solar array will charge them during the day as well as provide our electrical needs, we should be just fine but the system is being built with a space to simply tag in a third battery for 12.3kWh if real life conditions warrant.

[kazetsukai]

Originally Posted by HamSkoolie

Thanks,
Amp hours (ah) aren't a variable that means anything by itself (I'm sure you know this).

...

Yeah ^.



The OP did give a Wh rating, so I'm going with that. You'd agree though they'd need significant constant draw to deplete that overnight I assume. Solar diodes, that's one I didn't think of, and a really good possibility. I can't think of anything given the OP's description that would pull 600W + constant.


Need more info. I wonder if they have any shunts / hall sensors / meters that would show system or battery draw- observabiliy is what makes these systems manageable, operating without them is like flying blind.

[HamSkoolie]

Originally Posted by kazetsukai

Yeah ^.



The OP did give a Wh rating, so I'm going with that. You'd agree though they'd need significant constant draw to deplete that overnight I assume. Solar diodes, that's one I didn't think of, and a really good possibility. I can't think of anything given the OP's description that would pull 600W + constant.


Need more info. I wonder if they have any shunts / hall sensors / meters that would show system or battery draw- observabiliy is what makes these systems manageable, operating without them is like flying blind.

Yes on the Wh rating but still need to know the chemistry. Though going dead is going dead regardless of chemistry.
Yes, it would have to be a big draw for the entire night but a big solar array could do that. But what are the odds that the diodes for that many panels are bad? If they were purchased used and the fault was from day one I could imagine the panels were sold because they were compromised and the seller was a POS. I guess 600W of solar with bad diodes could drain close to 600W when there is no sun and some portion of that as soon as the light is insufficient to produce more power than the level of the batteries.

[Albatross]

Originally Posted by Vrad

Question:

Does anyone else have a problem of their inverter running their batteries to empty at night? We just finished building and have been living in the bus for a few weeks. Our solar can charge the batteries up to 100% during the day.

We have:
4 400wh solar panels = 1600wh total
4 300ah batteries = 1200ah, 14,400wh
And our inverter is an expert power 3000w inverter that does 3000 w continuous and 9000 surge

The batteries are all the same type were bought at the same time and charged to 100 before being hooked up.

At night our inverter runs only our fridge (297kwh/year) and potentially (it hasn’t yet because we’ve been having issues) charging our phones and running a window fan. We’ve only had it running the fridge everything else is off/unplugged.

We don’t know much about wiring and electric work, but we did have an electrician look at it after we got everything wired. And he said it looked great.

Could it be that it is getting to hot? Would that cause an issue?

Heat wouldn't cause that kind of an issue.

There's a number of things that could be the culprit; you have a load (drawing power) you don't know about because of a short or something somewhere, it could be caused by a problem with your battery connections, as well (if your batteries aren't all connecting, and you're essentially only working off 'one' battery instead of the whole bank), or your batteries are just getting old and have developed a 'memory' (happens in certain chemistries, from repeated over-discharge cycles, check the water levels in your batteries, and get a specific gravity tester and check that).

Other than that, there isn't really enough info to go on, and I would also second HAM's advice. He's 100% a solid source for electrical info on this forum, hands-down not likely to ever be beat.

[TheHubbardBus]

You speak of your inverter & AC appliances (the fridge). But do you have DC loads as well?

[HamSkoolie]

Originally Posted by Albatross

Other than that, there isn't really enough info to go on, and I would also second HAM's advice. He's 100% a solid source for electrical info on this forum, hands-down not likely to ever be beat.

I appreciate it but when it comes to the AC circuitry in RV's I'm limited to some home improvements, the basics, and theory.
DC and the wierd AC circuits of military weapons systems (which don't have much if anything in common with home systems other than that they USUALLY are moved via wires) are where my experience lays.


Now, here's a tidbit to put away for some day that it comes in handy.....
The Amp Hour rating of a battery can be manipulated for marketing purposes and often is. 12 volt batteries ARE NOT. They are 13.8 volts. The traditional lead acid battery, be it Flooded Lead Acid (FLA), Absorbed Glass Mat (AGM), or Sealed Lead Acid (SLA) is only ONE HALF charged at 12 volts. Anything below 10.5 or 11 volts will cause immediate damage and anything between that and 12 will shorten the life of the battery. Deep cycle batteries can be abused a bit more but not much.
So, for marketing purposes the traditional deep cycle battery is rated in volts and amp hours. We'll stick with 12 volts to keep it simple. Here's the money saving tidbit..... the industry standard for calculating amp hours of a battery so that consumer can compare apples to apples is a 20 hour test. In other words, how many amps can I get out of the battery for 20 hours? Thus a 100ah battery could supply 5 amps for 20 hours. Now the higher the amp hour rating the more juice is in the battery right? NOT NECESSARILY.

WalMart sells a 101ah deep cycle (about $95 last time I looked) but when you read the little print on the little label..... it's 101ah at 1 amp/hour or 101 hours (1 amp/hour supplied).
The WalMart battery uses the 1 amp/hour in order to market an inferior battery to unsuspecting consumers who are looking at price per ah and not at the rate of discharge.