Inverter - Charger - Leave well enough alone?

[obiwancanoli]

Here, yet again, I have more questions... you all must be getting a little tired of me with these inquiries, and I very much appreciate the patience of those who've responded to my previous posts. My focus has been on the electrical side of things lately, and so, as I learn, I keep checking things off the list...

One that remains is whether or not I ought to consider changing out my Inverter to something more... capable.

First, the components:

I currently have flooded battery bank which I'm planning to change to Lithium - two @ 200Ah. These batteries are between 3-4 years old, and likely require replacement soon. Awaiting install of Victron 712 meter, and a Victron Smart Solar 100A MPPT Controller. Considering adding 340 W Solar to existing 480 W on roof, plus 120 W portable panel. Existing Inverter is 2000W Modified Sine. Current controller is PWM 30A.

Since my plans are to spend more time boondocking, I felt it worth the peace of mind to look at upgrading my system so that I might enjoy a longer stretch dry camping, when I choose to do so. Strictly a novice here, hard to wrap my head around electrical theory and practice, so, I've been on a mission to learn, and research, opportunities to upgrade my system where it makes good sense to do so. Question is, I'm not knowledgeable enough to know if it DOES make sense.

First, I'm considering adding another 170W panel to the roof, and adding another portable panel of up to 200W. My objective here is to be able to generate enough solar to avoid tapping into the battery bank. While it may come to pass that I would run the AC, I'm not convinced I need to add enough solar to do so. After all, I do have a generator.

I HAVE been wondering if it would be prudent to change my Inverter to a 3000 W or 5000 W Inverter to address the potential that I might want to run the AC off grid. Prices for this seem pretty reasonable - most between $280 - $500. As I'm of the opinion that it's better to have it and not need it than the other way around, I'm willing to absorb the cost if it will bring me closer to my goal.

At most, my wattage needs appear to pencil out to around 2000 W/day. That comes to about 166 amps. AC not factored into this.

Am I on the right path here? Am I understanding enough to have asked an informed question? What am I missing, or not considering?

[MEXICOWANDERER]

My workup shows 13 8-D lithium units in congregation with saturated charging 5 hours a day. Meaning a lot of wattage. I estimated a 195 amp hotel load. And extreme cycling. Best case. Seventeen 8-D batteries and 3Kw panels would make it easier.

[obiwancanoli]

Matt_Colie wrote:
Mr Canoli,

I am glad to see that your head is on straight. I think the only thing that you missed, is that you did not do your power calculations on a spread sheet. This matters because when you make small mistakes, they are very easy to see and correct.

Your list of components is a very good start. Even with 400AHr of LiFePo, you will still be limited for running A/C. For the list as I read it, 200AHr will get you along for most cases.

In the past, I have done a number of conversions of racing boats to performance cruisers. Racing boats have little for creature comfort (including house electrics) and other accommodations that differentiates them from (anything) cruiser that has these features. The first part of the planning is the plumbing and electrics because the wood work can be fit around that stuff. Many would like to be able to run the main cabin A/C on the house bank. These are tiny units because they are water cooled and it still doesn't happen. I strongly suggest that your eliminate that line from your program. Unless someone gifts you the still viable battery bank from a Tesla.

Matt

Actually, Matt, not only is the AC offne list, it really was never on it.... I wanted enough power to run it, but fully understand and appreciate the energy required to do so. You're right that I didn't work a spreadsheet for power calcs, I'll remedy that soon... thanks!

[Matt_Colie]

Mr Canoli,

I am glad to see that your head is on straight. I think the only thing that you missed, is that you did not do your power calculations on a spread sheet. This matters because when you make small mistakes, they are very easy to see and correct.

Your list of components is a very good start. Even with 400AHr of LiFePo, you will still be limited for running A/C. For the list as I read it, 200AHr will get you along for most cases.

In the past, I have done a number of conversions of racing boats to performance cruisers. Racing boats have little for creature comfort (including house electrics) and other accommodations that differentiates them from (anything) cruiser that has these features. The first part of the planning is the plumbing and electrics because the wood work can be fit around that stuff. Many would like to be able to run the main cabin A/C on the house bank. These are tiny units because they are water cooled and it still doesn't happen. I strongly suggest that your eliminate that line from your program. Unless someone gifts you the still viable battery bank from a Tesla.

Matt

[MrWizard]

I use my inverter
For TV, laptop, MW, Fans at night, heating pad or electric blanket,
MW is the big power hog, but only for minute or two, warm a cup of coffee, heat water, warm up food, without using the generator

[3_tons]

CA Traveler wrote:
Perhaps the "best" equipment you can buy is a battery monitor. Spend some days camping and learn your battery and solar usage. Typically they display V, A, W, SOC, Ah, multiple daily usage and more. You would be well served IMHO as you're doing to learn more before buying equipment.

X 2, Always a Smart Plan!!

3 tons

[obiwancanoli]

DrewE wrote:
I think you may be a bit confused about electrical units here, and what they're measuring. I hope this doesn't come across as overly pedantic; I'm writing it in hopes of helping you understand, nothing more.

You wrote that you figured your electrical use per day was 2000 watts. Watts are a unit of power, similar to horsepower; it's a rate of doing useful stuff. I suspect you probably meant that you require 2000 watt-hours per day, a unit of energy, but I'm not sure on that. 2 kWh seems rather on the high side to me particularly if you don't have a residential fridge, but you know your needs and so forth better than I do.

18 Amps is a measure of current, not directly equivalent to either power or energy. In RVs they do sometimes get used that way with the (often unstated) assumption that the voltage is known, either 12V for DC loads or 120V for AC loads. 18A at 12V is quite a different power level than 18A at 120V: around 200W for the first, and 2000W for the second.

Amp-hours, a unit of electrical charge, may be what you're thinking of for your 18A. 18 Ah at 12V is equivalent to approximately 200 Wh; 180 Ah at 12V is about 2000 Wh. Thus, you'd need maybe 200 Ah of battery capacity to go 24 hours without solar charging or generator use, etc. If your present batteries are 6V batteries, that's about the capacity of your present battery bank.

Note that it's not practical to use solar "only" without tapping into the battery bank, unless you only use power when the sun is shining. What I think you're aiming for, and it's a good plan, is to have sufficient solar capability that you can produce at least as much energy per day, on average, than you consume; if that's true, then you can operate indefinitely without needing a generator or shore power connection.

My initial impression is that you'd be better off investing in more battery storage than in additional solar panels. It sounds like you have enough, or close to enough, solar power to meet your daily electrical needs, but not much storage to buffer it between when it's available and when it's needed, particularly if you have a day or two of cloudy or rainy weather.

For most people, it's not at all practical to run an air conditioner off of solar power. If you wish to do so, it would make a lot of sense to spend some effort in better insulating the RV and probably in replacing the standard RV air conditioner with a more efficient model, perhaps a mini-split unit.

Thanks, Drew, as I said, hard to wrap my head round this stuff.. yes, the plan was to produce at least as much as I consumed. The Li batteries I'm considering amount to 400 Ah, so it appears I'd have sufficient capacity. I'm aware that the AC would consume a lot of power, and thus, isn't practical without a generator or shore power.

It wasn't running the AC, it was having the power to do it, but maybe that's unnecessary.

I MIGHT be able to put two 300Ah Lithiums in the tray, but I don't want to. By the time I'm done, I will have invested much more than I needed to in the wrong things, so capping these enhancements makes sense, and in the bigger picture, probably is more than I really need. A better Inverter-converter-charger would make more sense to me.

[CA_Traveler]

Perhaps the "best" equipment you can buy is a battery monitor. Spend some days camping and learn your battery and solar usage. Typically they display V, A, W, SOC, Ah, multiple daily usage and more. You would be well served IMHO as you're doing to learn more before buying equipment.

I have a plan to add more solar and/or batteries should I choose which would be compatible with the current setup.

[wa8yxm]

2oldman wrote:
Get a pure sine inverter. You and your stuff will be happier in the long run.

I will seriously second this... PSW is the only way to go
First they are not all that much more expensive
Second: Most of them do not interfere with radio or Television reception. MSW may (or not) depending on a host of other things.

One last thing... Some (Myself in the past included) think MSW may be more efficient at making dc into ac.. Turns out it's not. MSW or PSW the best you can hope for is about 90% efficiency.

[theoldwizard1]

First, I hope you have deep pockets !

If you are seriously considering replacing your inverter start looking for combination inverter/charger/automatic transfer switches like these from Samlex. Easy to install. Get rid of your current AC-DC converter.

Some of these unit can automatically start a generator.

You need to do some serious calculations on battery size if you want run an air conditioner. For sure your will need a MicroAir EasyStart

[DrewE]

I think you may be a bit confused about electrical units here, and what they're measuring. I hope this doesn't come across as overly pedantic; I'm writing it in hopes of helping you understand, nothing more.

You wrote that you figured your electrical use per day was 2000 watts. Watts are a unit of power, similar to horsepower; it's a rate of doing useful stuff. I suspect you probably meant that you require 2000 watt-hours per day, a unit of energy, but I'm not sure on that. 2 kWh seems rather on the high side to me particularly if you don't have a residential fridge, but you know your needs and so forth better than I do.

18 Amps is a measure of current, not directly equivalent to either power or energy. In RVs they do sometimes get used that way with the (often unstated) assumption that the voltage is known, either 12V for DC loads or 120V for AC loads. 18A at 12V is quite a different power level than 18A at 120V: around 200W for the first, and 2000W for the second.

Amp-hours, a unit of electrical charge, may be what you're thinking of for your 18A. 18 Ah at 12V is equivalent to approximately 200 Wh; 180 Ah at 12V is about 2000 Wh. Thus, you'd need maybe 200 Ah of battery capacity to go 24 hours without solar charging or generator use, etc. If your present batteries are 6V batteries, that's about the capacity of your present battery bank.

Note that it's not practical to use solar "only" without tapping into the battery bank, unless you only use power when the sun is shining. What I think you're aiming for, and it's a good plan, is to have sufficient solar capability that you can produce at least as much energy per day, on average, than you consume; if that's true, then you can operate indefinitely without needing a generator or shore power connection.

My initial impression is that you'd be better off investing in more battery storage than in additional solar panels. It sounds like you have enough, or close to enough, solar power to meet your daily electrical needs, but not much storage to buffer it between when it's available and when it's needed, particularly if you have a day or two of cloudy or rainy weather.

For most people, it's not at all practical to run an air conditioner off of solar power. If you wish to do so, it would make a lot of sense to spend some effort in better insulating the RV and probably in replacing the standard RV air conditioner with a more efficient model, perhaps a mini-split unit.

[obiwancanoli]

Lwiddis wrote:
“I felt it worth the peace of mind to look at upgrading my system so that I might enjoy a longer stretch dry camping,..”

If this comment is regarding electrical power, you are missing the point. An adequate solar system recharges your batteries fully every clear or mostly clear day. If it doesn’t the system is faulty.

Isn’t 2000 watts at 12 volts about 165 amp hours? Not 18.

yup...

[CA_Traveler]

Let’s assume your small A/C draws 10A, that’s 110A for a 12V battery. 36A from solar leaves 64A from the battery for say 5 hours or 320Ah. Now your 400Ah batteries are discharged w/o day and night house loads and with no battery power the next morning.

Insert your own guesses for power draw and run time but A/Cs take a lot of power.

[3_tons]

Well, it’s mostly a “what’s in the eye of the beholder” sort’a thing (as you’ll begin to see...), thus much depends on what you might consider to be an upgrade...From my perspective, if I were to do an inverter upgrade, I’d be looking at a True Sine Wave model, and likely a pass-thru inverter-charger...

Why??... Because sinewave is easier and better for delicate electronic devices, air cond motors due to better electrical efficiency (less wasteful energy to heat conversion). Either way, you’d want to know what your worst case energy consumption might be, then make plans accordingly...BTW, the ‘wattage’ rating of an inverter is often more to do with marketing gimmickry than electrical reality thus, there’s a few other important specs to first look into (i.e. important surge capacity and surge duration), and be aware that manufacturers often hide these details - in fact, this is often why some seemingly like-kind inverters have a wide breadth of price points - overstated inverter data sells!!

Other things worth consideration are whether the inverter is a hybrid-type (true supplemental shore-genny power load assist) and whether a LF (larger-heavier transformer based = slower) or a HF (more compact transistor-ladder design = faster)...Generally speaking, bulkier LF models are robust and very well suited for higher and longer duration surges, like air conditioners, etc, however (having said that...), note that my HF 2000w ProSine 2.0 has served me quite faithfully in this same kind of service (air cond. @41 LRA + fan ...).

To this end, you should plan for the future - to avoid nagging dc voltage drop bottlenecks (associated with extreme battery demands), I’d also go with 0004 batt cabling and keep the round-trip cable as short as practical...

To summarize, think about what inverter type and overall *system wiring scheme you could best live with, and adjust your sights accordingly...JMHO (been down this dang rabbit hole too many times but survived!! - lol!)

*(single or multiple outlets, ATS switches, a rewire, passive-cascading system with sub-panel, etc)

Just a few starting ideas only...
3 tons

[2oldman]

Get a pure sine inverter. You and your stuff will be happier in the long run.

Paying only a few hundred for a big inverter is not a good idea. That's cheap, and cheap things don't last. I run air with my Outback 3400w, it's big, it's heavy, and it's expensive, and will probably outlive me.

Cry once. It's better than burning one up every few years.