Upgraded solar system, puzzled by the remaining limitation(s)?

[jesfl]

Well he could eliminate the BMS by bypassing them temporarily to test the microwave again.
Don't try to charge until the BMS is re-instated.

Quattrohead: Thanks to you once again for this idea. I understand the concept, but I'm not exactly sure how to wire to bypass the BMS units. And, trying that is slightly frightening to me at my beginner/novice/unskilled technical level.
My very small solar compartment (RV basement storage) space is also extremely limiting for wiring. The furthest away-from-busbar battery (#4) is not reachable without unwiring and removing batteries 1-3 on the slide-out battery tray I built. For now, this is one test I will pass.
Honestly, I do not believe the functioning of the BMS is the problem. The one "suspect" BMS in the encased battery is undoubtedly low quality. I just accept that fact. Because of that suspicion, I have tested numerous times with that battery/BMS completely disconnected from the system. It makes no difference. The inverter still shuts down at the same current draw from the batteries.

 

[jesfl]

I see a wire issue. The wire length from each battery to the common busbar should be the same. In your case battery #1 has the shortest wires and will grab more of the load than battery #4. Even out the wire lengths and the load will be better balanced.

Sure looks like a voltage drop issue to me. I'd run it at a steady heavy load (microwave level 6) and measure the voltage on each battery, at the common busbar and at the inverter terminal. It will help chase down the weak link.

TacomaJoe: Thanks./ I get what you are saying. When I first read your comment here (and others similar), I reacted "that makes sense." Then I tested, and it does not seem to be the issue. I don't understand what voltage drop would be considered a major problem? But 0.01v to 0.08v (under load, microwave level 6) does not seem to me a drop that would cause the inverter to shut down?
I still have a couple of tests to run -- i.e., direct connect of microwave to the back of the inverter -- but I have begun to wonder if it is not the original 120v wiring through the RV's power panel that is the source of the power loss? Won't the direct connection of the mnicrowave to the inverter's AC receptacle prove or disprove that?

 

[Zwy]

3Kw inverter should be on 24V system. I run the roof air on my truck camper off the battery, microwave too. Wife uses a blow dryer and curling iron. System is 24V, never had a problem running anything.

I used a buck converter rated for easily twice the intended 12V draw to power all the 12V stuff. The draw from it when nothing is on is basically 0A.

Basically, the 12V system in the RV is hitting it's max potential and why you are seeing this limitation. The inverter itself probably has a high enough low voltage cutoff combined with voltage drop and this is the result. The voltage drop percentage wise is exponential when it comes comparing 24V to 12V for the same wattage load. At 12V, with 4/0 cable, 320A load, 10 feet of cable, the voltage drop is close to 3% while 160A at 24V is about 0.75%.

 

[jesfl]

Zwy:

Thank you so much. I am not surprised by your suggestion, and it is appreciated.

I wondered about the 24-volt system as I've noticed it mentioned here on the Forum numerous times. However, at my low level of beginner knowledge, I didn't even let my thoughts go there.

I don't even understand a "buck converter?"

If you have a moment sometime, I would very much appreciate a basic summary of what I would need to change to convert my 12-volt system to 24-volts? I will also do a search here on the forum and start reading/learning more.

From my very limited knowledge, I think I understand I would need:
- new battery wiring,
- a 24 volt inverter,
- buck converter (?) whatever that is,
- different breakers and/or fuses?

Is everything else the same?

HOWEVER, please see my next post. I just ran a very revealing test and my inverter microwave ran at full power without shutting down the inverter. Shocking to me (figuratively, not literally).

 

[n2aws]

FWIW I have a Panasonic Inverter microwave, according to a Kill a Watt meter it draws 1500 w on shore power. My power setup is 2ea 100ah 100a BMS lifepo4 in parallel, 2000w Renogy inverter, 1/0 cables 28" long, an ATS. I only "cook" things for a couple of minutes at a time. Works fine

@jesfl Here is someone posting they have less batteries than you, same microwave (or at least same brand and style) and using it successfully with a "smaller" but quality inverter. his 2,000w. vs your 3,000w

This leads me to believe the others here are correct, and the issue is likely the cheap-o inverter.

 

[jesfl]

50ShadesofDirt: Thank you. to your helpful points.
1. The batteries and individual cells certainly read "full" on my AiLi battery monitor and on my multimeter when I test at the individual batteries. Individual cells typically are 3.30-3.35 when the bluetooth app and the AiLi meter read fully charged. Note: the AiLi meter typically reads a collective 14.40v-14.46v when all charging has been stopped by the BMS units.
For a diffferent test, I've now been running on the batteries/inverter for 39 hours with zero solar or other charging. I turned off the solar charging for this little test. My AiLi meter now reads 66.1% capacity remaining (13.04 volts overall). The individual batteries via the bluetooth app range from 13.09v/67% to 13.08v/61%.
Not surprisingly, the battery with the lowest voltage/% charge is the 280Ah battery that has the shortest cables to the inverter. At this moment, that battery is discharging at 7.1amps and the one with the longest cables to the busbar is discharging at 4.7 amps.
The highest power setting I've ever been able to run the inverter microwave on with the inverter is the "Level 7." I tried Level 8 once while also charging with solar (charge controller showed about 23v input at that time). The microwave ran about 45 seconds before the inverter turned off. (I was momentarily ecstatic with hope during the 45 seconds, until my bubble was burst.)
2. There is no possibility of moving the inverter. This is an RV. The "basement"storage area for batteries, inverter, charge controller, etc., is a 40in x 40in x 4 ft cubicle. Very tight space for batteries and equipment.
And, I did not register your other suggestions about a direct microwave connection at first. But, now I have figured out how to connect the micriowave to an AC plug in the back of the inverter. Not easy, but do-able. Per my long post, I am seeking assistance with moving the (built-in) microwave to test the direct connection. I am eager to try the direct connect test. I will let you know.
Al;so, I have a generator. I also have 800 watts of solar, with another 400 watts (4 new panels awaiting my wiring). I ordered more to compensate for the residential refrigerator during the low-solar winter months. Keeping batteries charged, or charging them, is not an issue at all for me.
Thank you, again.

Surprise, SURPRISE! My microwave ran at FULL POWER ! ! !

I got some lifting help and was able to connect the microwave directly to one of the AC outlets on the WindyNation VertaMax 3000 watt inverter.

I started testing at the microwave's "Level 7" power and then one-by-one through the power levels to "Level 10."

The microwave ran without a hiccup. (To be honest, I stopped the full power test just short of one minute because In order to do so I had to connect a heavy-duty 6' extension cord to the inverter and then the microwave to the extension cord. Which, to me, makes it even more surprising that the microwave ran at full power! Because of the extension cord, I didn't want to risk other problems.

My conclusion is that the power loss/inverter shutdown problem is not with the batteries/inverter and wiring.

Rather, the inverter is being limited by the wiring through the (20-year-old RV's) single "kitchen" circuit on my RV's main power panel which has numerous other appliances and AC receptacles. (But not a lot of things running at once.)

The remaining issue, for me, is how to best wire a new connection from one of the inverter's AC receptacles and install a new plug dedicated to (a) the residential refrigerator and (b) the microwave? I had been thinking about that for the refrigerator alone so I could bypass the RV's power panel and other wiring.

Will my idea of a new 8-gauge heavy-duty extension cord run from the inverter and directly wired to a new, dedicated receptacle work?

Is there a better way?

I cannot use the direct connection on the inverter, because it already has a Romex 8-gauge 3/2 wiring running to my 3-way switch and then to the RV's power panel?

Here's the kicker -- although I'm not sure how much it matters. I had been running the system with the solar panels turned off (a test) for over 40 hours. I also was purposely using power heavily with microwave (Levwel 5-6 power, no problem), ice maker, coffee pot and of course refrigerator, lights, computer, TV, charging ports, etc.

The meter on the inverter itself was showing 13.1 volts. My AiLi battery monitor showed 62% of collective battery power remaining and voltage of 13.15, so it was consistent with the meter on the inverter.

And, the microwave still ran at FULL POWER! I could hardly believe it.

I think I will consider a future 24-volt conversion, although I don't really know enough about that. I'll just use my 12-volt system (after the new direct connection for the microwave refrigerator) for a while and see how much I future modifications.

Other thoughts are most welcomed.

To all who helped here, you have my deepest gratitude. The DIY Solar Forum, and those of you who participarte helping low-knowledge beginners like me are simply amazing!

Thank you, thank you, thank you!!!

jesfl

 

[wme]

A lot of older rv's have the 120v system chained through several outlets. Maybe a half a day spent removing and cleaning the wiring connections would prove helpful

 

[Zwy]

Zwy:

Thank you so much. I am not surprised by your suggestion, and it is appreciated.

I wondered about the 24-volt system as I've noticed it mentioned here on the Forum numerous times. However, at my low level of beginner knowledge, I didn't even let my thoughts go there.

Basically a 24V system lets you halve the amperage while reducing the voltage drop. Makes it very efficient, less wasted energy in heating of wires and components.

I don't even understand a "buck converter?"

A buck converter reduces voltage from a higher voltage to a lower voltage. I have one on my golf cart too for running 12V accessories off a 36V bank. 24V to 12V in my truck camper.

If you have a moment sometime, I would very much appreciate a basic summary of what I would need to change to convert my 12-volt system to 24-volts? I will also do a search here on the forum and start reading/learning more.

You can look at my truck camper thread. https://diysolarforum.com/threads/heres-my-truck-camper-setup.29488/

From my very limited knowledge, I think I understand I would need:
- new battery wiring,

That can remain the same as wattage will remain the same but on 24V the amps will be 1/2.

- a 24 volt inverter,

Yes.

- buck converter (?) whatever that is,

Yes, if you retain some 12V loads.

- different breakers and/or fuses?

I just added a 24V fuse panel, then powered the buck converter from that 24V fuse panel. The buck converter powers the original 12V loads. I did change out the 12V fuse panel as everything was on about 2 12V fuses and I wanted to keep some 12V circuits separate from each other.

Is everything else the same?

Not much else to change. I intend to change out the camper 3 way fridge to a 24V compressor fridge. I run all the original lights, backup camera and other 12V loads off the buck converter.

HOWEVER, please see my next post. I just ran a very revealing test and my inverter microwave ran at full power without shutting down the inverter. Shocking to me (figuratively, not literally).

I had read it. It can be tricky running new 120V circuits in a camper. One thing is what is the current wire size? If 14AWG, then I'd run a new dedicated 12AWG wire for the microwave. I'd also pull all outlets on the original 120V circuits and check connections. You might find some have resistance and led to the problem. Or even a bad outlet.

 

[jesfl]

A lot of older rv's have the 120v system chained through several outlets. Maybe a half a day spent removing and cleaning the wiring connections would prove helpful

Thanks. I'm beginning to figure out the cheapest-fastest construction techniques on my 20-year-old fifth wheel and the problems that creates. About 18 months ago, I removed the useless automatic transfer switch and put in a Blue Sea 3-way selection switch. I never used the old transfer switch in 5+ years. So, I also took out and cleaned/tightened everything on the RV's power panel then. I even shortened some ridiculously long original wiring to breakers, etc. that was literally wound up in big spools behind the power panel.

And, yes, your is certainly is a good reminder to check again. Also, when my directly-wired inverter-to-microwave test confirmed the batteries/inverter were not the problem, I realized I need to start checking line loss in the 120v wiring. I bet I will find some voltage drop-offs there. I also am guessing I might have added to the voltage loss problems in the 120v system when I added that selector switch and an extra safety fuse.

Thanks, again.

 

[jesfl]

Basically a 24V system lets you halve the amperage while reducing the voltage drop. Makes it very efficient, less wasted energy in heating of wires and components.



A buck converter reduces voltage from a higher voltage to a lower voltage. I have one on my golf cart too for running 12V accessories off a 36V bank. 24V to 12V in my truck camper.




You can look at my truck camper thread. https://diysolarforum.com/threads/heres-my-truck-camper-setup.29488/




That can remain the same as wattage will remain the same but on 24V the amps will be 1/2.


Yes.


Yes, if you retain some 12V loads.



I just added a 24V fuse panel, then powered the buck converter from that 24V fuse panel. The buck converter powers the original 12V loads. I did change out the 12V fuse panel as everything was on about 2 12V fuses and I wanted to keep some 12V circuits separate from each other.



Not much else to change. I intend to change out the camper 3 way fridge to a 24V compressor fridge. I run all the original lights, backup camera and other 12V loads off the buck converter.

I had read it. It can be tricky running new 120V circuits in a camper. One thing is what is the current wire size? If 14AWG, then I'd run a new dedicated 12AWG wire for the microwave. I'd also pull all outlets on the original 120V circuits and check connections. You might find some have resistance and led to the problem. Or even a bad outlet.

Wow! I've just studied your system photos (via your link, thank you) several times. And, as always with new things electrical, it's a bit scary. If I go over your system slowly maybe 6-dozen times, or more, I may fully understand it. That's if I do other reading/research along the way. Your system is beautifully done! Considering the challenges I had with my limited RV space, I sincerely admire your workmanship.

On minor curiosity. I have a couple of fans like the one in your photo, one connected to my Blue Sea 12v busbar and running 27/7 unless I manually turn it off with the breaker I installed. A thermostat/controller is on my list, but I honestly have not figured out what to look for. May I ask what you show in your photo?

To your point, which I just read and absorbed for the first time: "You might find some have resistance and led to the problem. Or even a bad outlet." Yes, I'm sure I will . . . especially now that I understand there are voltage losses in the RV's original 120v wiring. Honestly, as a raw beginner, I'm first going to have to figure out the "how" of testing the existing 120v wiring, plugs, etc. in the RV.

FYI, the original Romex into the RV from the 30-amp shore power connection is 10/2 Romex (orange casing). When I made my few changes, I used the same. For the new connection from one of the inverter's AC receptacles to my planned new receptacle for the microwave, I ordered a Southwire heavy-duty 10/3 outdoor extension cord to cover the distance from my solar/electrical compartment to the kitchen area. I'm comfortable with Southwire's products.

Again, thank you so much for your comments and assistance . . . and, also importantly, for the starting pathway for me to learn more about a 24-volt system.

jesfl

 

[Zwy]

Wow! I've just studied your system photos (via your link, thank you) several times. And, as always with new things electrical, it's a bit scary. If I go over your system slowly maybe 6-dozen times, or more, I may fully understand it. That's if I do other reading/research along the way. Your system is beautifully done! Considering the challenges I had with my limited RV space, I sincerely admire your workmanship.

Thank you, it took me all winter to complete that project a few years ago.

On minor curiosity. I have a couple of fans like the one in your photo, one connected to my Blue Sea 12v busbar and running 27/7 unless I manually turn it off with the breaker I installed. A thermostat/controller is on my list, but I honestly have not figured out what to look for. May I ask what you show in your photo?

This is the one I used, it's 24V but I'm sure there is a 12V version. https://www.amazon.com/gp/product/B076YD8H19/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Here is a 12V version. https://www.amazon.com/LM-YN-Thermo.../B076Y5BXD9/ref=psdc_5006566011_t5_B076YD8H19

Mounting bracket is just a scrap piece of aluminum. Order some standoffs like these to mount the thermostat. https://www.amazon.com/gp/product/B07PK23VC4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

To your point, which I just read and absorbed for the first time: "You might find some have resistance and led to the problem. Or even a bad outlet." Yes, I'm sure I will . . . especially now that I understand there are voltage losses in the RV's original 120v wiring. Honestly, as a raw beginner, I'm first going to have to figure out the "how" of testing the existing 120v wiring, plugs, etc. in the RV.

Testing done by voltage drop testing across a connection with the circuit under load. It is important to understand the circuit needs to be loaded. Open circuit voltage testing just reads voltage potential, once a load is placed upon a circuit, voltage drop across a connection will indicate points of resistance. Read this post where I linked a video explaining the proper method of voltage drop testing. https://diysolarforum.com/threads/do-i-have-a-ground-fault-situation.62090/post-776775 Practice on simple circuits and add in some resistance so you learn how to do it.

FYI, the original Romex into the RV from the 30-amp shore power connection is 10/2 Romex (orange casing). When I made my few changes, I used the same. For the new connection from one of the inverter's AC receptacles to my planned new receptacle for the microwave, I ordered a Southwire heavy-duty 10/3 outdoor extension cord to cover the distance from my solar/electrical compartment to the kitchen area. I'm comfortable with Southwire's products.

10/2, very nice. I'll wager you find a connection on an outlet is where the resistance is located.

Again, thank you so much for your comments and assistance . . . and, also importantly, for the starting pathway for me to learn more about a 24-volt system.

jesfl

I really like a 24V system in an RV. I don't have to worry about overloading an inverter, dealing with voltage sag or high amp loads that could trip a BMS.

 

[wme]

Thermostatic switch, pick your temp. note switches are rated in C
https://www.ebay.com/itm/1254179326...eqCOpFACwJt9fm4DIPPpY8dqU=|tkp:Bk9SR-aXzMvfYg

 

[jesfl]

Thermostatic switch, pick your temp. note switches are rated in C
https://www.ebay.com/itm/125417932690?hash=item1d337dc792:g:ROUAAOSwMmVgxAmD&amdata=enc:AQAIAAAA0Hl9u/R8K8LEKt7BZ1SPx55Pv/GjsndkovkOLQ9yQoSlUwMIJhZOZR/DpaeBTk5fU7wKDPQPRpHD+4+Fga6YLuqPLcgLNf42YzGZjpDZnQVv4GWI0MzQqJyY439iEl0zQhqwQqDluTAfV7whpdfwy9VG50JiAVwYFfwUEiP6X8e3033sYS2V1femay0uUF5wed9ixUSDUd443gLPPPCu+GsHQPc6zVsFnxFLVU6TW/IeJn82TdClsHs9XuiVK2eqCOpFACwJt9fm4DIPPpY8dqU=|tkp:Bk9SR-aXzMvfYg

I just wanted to say thank you, once again, to everyone who contributed to helping me solve my inverter power limitation problem.
The sharing of your time and knowledge so graciously and helpfully is astounding to me, to say the very least. That's been true every time I've confronted problems and sought solutions via the DIY Solar Forum. It is truly amazing and inspiring. It is impossible for me to adequately express my gratitude.

In the case of my inverter shutdowns and battery power limitations, I now know the source of the problem is my 20+-year-old RV's original 120v wiring. I still face the challenge of testing/tracking down those voltage loss problems. Of course, I'm also very eager install the needed additional direct connection from the inverter with a new dedicated receptacle for the inverter microwave/air fryer.

I've also stopped using the microwave on anything other than middle-range power levels even when on shore power because of my new knowledge that there is a significant problem somewhere in my old, original RV 120v wiring . . . until I find an fix the old system's wiring weakness. Better safe than sorry.

Thank you, thank you, thank you to all.

jesfl

Thank you, it took me all winter to complete that project a few years ago.



This is the one I used, it's 24V but I'm sure there is a 12V version. https://www.amazon.com/gp/product/B076YD8H19/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Here is a 12V version. https://www.amazon.com/LM-YN-Thermo.../B076Y5BXD9/ref=psdc_5006566011_t5_B076YD8H19

Mounting bracket is just a scrap piece of aluminum. Order some standoffs like these to mount the thermostat. https://www.amazon.com/gp/product/B07PK23VC4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1



Testing done by voltage drop testing across a connection with the circuit under load. It is important to understand the circuit needs to be loaded. Open circuit voltage testing just reads voltage potential, once a load is placed upon a circuit, voltage drop across a connection will indicate points of resistance. Read this post where I linked a video explaining the proper method of voltage drop testing. https://diysolarforum.com/threads/do-i-have-a-ground-fault-situation.62090/post-776775 Practice on simple circuits and add in some resistance so you learn how to do it.



10/2, very nice. I'll wager you find a connection on an outlet is where the resistance is located.


I really like a 24V system in an RV. I don't have to worry about overloading an inverter, dealing with voltage sag or high amp loads that could trip a BMS.

FYI, I downloaded your 24-volt system photos, the links, and a couple of videos so I have it available in the future when I get focused on whether or not to convert to 24 volts. Beginning soon, as I boondock, I'll be without internet typically 50% of the time. There will be wonderous time -- in the quiet and without popup ads and other web interruptions -- to learn the 24-volt process.

You have my gratitude. Thank you so much for everything you offered.

 

[AmpD]

Free advice from a newbie.

If your 12v system can meet your needs focus on fixing the old rv wiring problem first. It is likely inexpensive comparatively and will let you do what you want with what you have.

After some research you might find a number of your current components can be used to make the switch to 24v when you are ready.

 

[WindWizard]

First, an apology to to those participating herer. Today, I must stop my attempt to understand this inverter/power problem because of other pressing matters.

To me, this issue is just another electrical “rabbit hole” with no clear, single answer (at least that I can understand). I sincerely appreciate the new things learned from each of you who are attempting to assist.

For my records (and respecting your assistance) . . . I now think I see the problem! But, I have no idea of the cause or how to fix it. That will have to come later.

I tested voltages yesterday and today and the results were similar. Today’s slightly lower voltages were, I assume, because the collective batteries were depleted to 13.11 volts on the AiLi shunt battery meter when I tested.

VOLTAGE READINGS
AiLi Meter 13.11v
Inverter, Low Load * 13.03v
Inverter, Micro Level 6 11.52v
Inverter , Micro Level 7 11.33v
Inverter, Micro Level 8 Shutdown **
* Inverter, lights, fridge, TV depleting batteries overnight
** Inverter shutdown supposedly set for “warning beep” at 11.0v and shutdown at 10.0 v

The only assumption I have the knowledge to make from this is that the internal inverter settings actually have it shutting down at 11v (not 10v), and the microwave startup surge pushes it below that 11v threshold?

Still, why? 700+ Ah of LiFePO4 batteries, 120 amp BMS (4)? It cannot be battery capacity. So, I do not understand.

To your points/questions about my 4/0 battery-to-inverter cable lengths:

Battery Inches To Busbar Total To Inverter *
# 1 8” 17”
# 2 10” 19”
# 3 18” 27”
# 4 29” 38”

Notes:
(a) There is a 250 amp breaker between the busbar and inverter connections, I use it as a master on/off switch and as inverter protection. Why? Somewhere I read I should have it.
(b) I tested several times, while doing the above, and got readings showing a decrease in volts from the busbar through the breaker to the inverter from 0.00 volts to 0.10 volts, surely minimal?

And, yes, I checked an online Voltage Drop Calculator (Rapid Tables), as suggested, and found that for my furthest-away-from-busbar battery (38” total) the voltage drop estimate was 0.0513 volts. For the other batteries with shorter connection lengths, less. But I do not know how to “average” those voltage drops into diagnosing my problem. Or, if only the longest cable length matters?

To conclude, for a while, my current thoughts are:

-- The problem might still be (partly) the inverter?
-- But, the problem is most likely low voltage getting to the inverter from my batteries/system?
-- And, now I’m even beginning to wonder if I have something wired wrong?

Once more, I sincerely appreciate the time of all who have attempted to assist me. I will not be able to follow-up on any additional thoughts/suggestions or questions until next week, most likely. But, as time will allow, I will check on any responses. And, I will renew this conversation as soon as I can.

Thank you, again, to all.

jesfl

This does not appear to be a inverter related issue. It seems that you are dropping the voltage in your wires going to the inverter or your circuit breaker.

You should not be dropping 2 volts between your batteries and the inverter.

It could be a poor wire crimp or simply the wire is not 4/0 or something else. To drop 2 volts then your resistance would be .01 ohms at 200 amps.

It should be easy to determine where you are dropping the 2 volts. Just fire it up and then start measuring.

 

[Zwy]

This does not appear to be a inverter related issue. It seems that you are dropping the voltage in your wires going to the inverter or your circuit breaker.

You should not be dropping 2 volts between your batteries and the inverter.

It could be a poor wire crimp or simply the wire is not 4/0 or something else. To drop 2 volts then your resistance would be .01 ohms at 200 amps.

It should be easy to determine where you are dropping the 2 volts. Just fire it up and then start measuring.

The problem was in the 120V circuits. Usually in a camper the 120V circuits are daisy chained from one outlet, switch or load. Somewhere there is a connection that is causing the resistance.