House battery grounding question

[JayArr]

would a 2500W HF inverter last longer than and 2500W LF inverter?

No, both the same.

Does the LF run hotter than the HF inverter? I assume it does.

No. If they are both the same efficiency then the heat they produce will be the same.

And are you "in the danger zone" with a HF inverter running 80+% of the rated power for long periods of time... due to heat?

80% = no, 90% = i'd say yes. BUT That goes for a HF or a LF, 50%-65% id a better target

what's attractive are those hybrid HF Inverter/Chargers since all the necessary functions (and internal relay power switching) is inside. Or do you thing buying separates are more reliable and easier to diagnose

I like the Inverter/Chargers, they use the same circuitry for both by reversing the way the transistors pass current so you end up with very powerful, very high current chargers that get to take advantage of the on board CPU. The Xantrex Prosine 3.0K has a 120A charging capability.

Putting separates together can be fun if you're doing a DIY project on your trailer on the weekend but for Pros, time is money, so a box that already has a transfer switch and a charger built in simplifies install by an hour or two plus the savings in wire, terminals etc.

since there are so many PSW inverters on the market under $1,000 I'm more likely willing to sacrifice brand vs. Amazon sourced China made PSW inverter models.

There are also a lot of liars on Amazon. Make sure you read everything very carefully. Sine wave. modified sine wave and pure sine wave are different. It's togh to make a PSW with a LF inverter so a lot of the El-Cheapo models my not have a nice clean sine wave when you actually put a heavy load on them. The first day it arrives put a 65% load on it and look at the sine wave with an oscilloscope. Amazon is pretty good at returns so make sure what you buy is from Amazon itself and if it's from a company that just lists on Amazon read the return policy really carefully.

Remember the old adage - If it seems too good to be true it probably isn't.

I would consider a 2500W PSW LF Inverter/Charger for less than $1000 "too good to be true"

Caveat Emptor.

 

[Non-partic]

Thanks for your very quick replies! You have me really thinking there is no reason why a HF inverter will be just a reliable and lower cost vs. a LF inverter.

I am still wondering if the lowest price choice, without sacrificing quality, is possibly buying a $600-$800, 2500W, PSW Magnum or Dimensions LF inverter that seems to be more on the "industrial-end" of spectrum and on the higher price of the retail spectrum too.

All these subjects you answered are helping make the right buy decision, so thank you!

Do you have any opinion on the reasons for building a 24V bank of LiFeP04 batteries as as better choice vs. building a 12V battery storage bank -- if you have to buy new components anyway?

Why do I ask?

I think you know that I am considering a plan to double my battery storage capacity (now ~200ah effectively out of 410aH of FLA batteries; and one option is to just build a separate LiFeP04 power grid to my existing FLA battery grid.

Why?

Well, I seem to think I need my FLA battery bank to run my 22A basement ACs... if I want to also turn on my microwave and run it for 3-5 minutes; and I don't know if yank out my 420ah, 4-6v-GC2-FLA batteries and replace them with 300aH of LiFeP04 that the Lithium batteries or my new PSW, HF-inverter, will work safely? Should I be concerned?

I.e., of course there is no problem running these loads on shore power, or generator power, but running L1 & L2 load on inverter power concerns me. Should it?

I think we are talking about 30A being to the inverter, and I don't know if the lithium bank or if the HF inverter can handle that drain/heat for 5+ minutes or more, and not fail immediately... or over the course of a few seasons... or worse start a fire if there is an overload condition? What do you think?

So the purpose of building a secondary/additional LiFePo4 power grid is part convenience, part cheaper expense, part safety... and the goal is to split off the power for my residential refrigerator and my 8A portable AC, from the FLA power grid.

Why is this important for boondocking?

I figure my refrigerator and 8A portable AC will represents 50% of my power demand. So why not split it off and power it with a separate 200A-300A LiFeP04 to accomplish my goal of increasing my amp-hours of useable power by 250%?

What do you think?

On the cheap end it looks like a $1500 project. And on the high end $3000. And I had spending money unnecessarily. It all feels like I am buying an insurance policy. ...But what I really like to know are the ins-and-outs of how these factors all play together, because that's the fun of learning.

So again, thank you for helping me, and all of us who have these questions... learn.

And my apologies for hijacking this thread. We are a long way from discussing battery grounds an I suppose a new thread should have been started.

 

[Ex-Calif]

I think you know that I am considering a plan to double my battery storage capacity (now ~200ah effectively out of 410aH of FLA batteries; and one option is to just build a separate LiFeP04 power grid to my existing FLA battery grid.

Now the question is how you are gonna charge the batteries? Think of the system voltage like pipe - 12V pipe can only push so many amps. A 24V or 48V pipe has a lot more capacity.

If you are planning solar it is really important to plan in advance. Most solar controllers will be limited at 12V and won't be able to handle all the output from a large array.

 

[Non-partic]

How much current demand will a bank of 300ah LiFeP04 handle? I know what it is rated for, but I don't know what I can expect safely.

For example: If I have an 8A portable AC running, and a 2A residential refrigerator, and 6A of of other loads, and then I run my 10A microwave, can my inverter and 300aH lithium battery bank handle 16A sustained and 26A for 3-5 minutes? ...Or do I need a 400ah lithium battery bank?

As for charging these lithium batteries:

* The alternator with a 10A DC-DC should work. I typically drive for 5+ hours; and if I have 300W of solar also charging the batteries then that will help out too.

* The goal is to get to my boondocking camp spot with a full charge.

* This is also why I would use a separate inverter/charger capable of charging LiFeP04 batteries, and the Automatic Transfer Switch will handle the switching between generator charging and shore power charging.

Note: Once you need to run your generator to power your rooftop or basement AC, you don't need more battery storage! So this whole upgrade becomes mute! So why do it at all just to save on diesel fuel to run the generator which is a sure thing?

And if this project costs $1,500-$3000... you can buy a lot of diesel fuel for that amount of money. So you will not break even for 3+ years I figure.

Still, it's fun to learn about this technology, but going green does not pencil-out if you ask me!

BTW, did you hear that DEF is going to be hard to find soon! And no DEF is a problem that will affect all sorts of supply chain problems!

 

[JayArr]

For example: If I have an 8A portable AC running, and a 2A residential refrigerator, and 6A of of other loads, and then I run my 10A microwave, can my inverter and 300aH lithium battery bank handle 16A sustained and 26A for 3-5 minutes?

Yes it can but remember that you have a 10:1 ratio. 26A of load on the AC side will draw approx 260A on the DC side. At that rate your batteries will begin to deplete really, really, fast.

You'll now be pulling over 3000W so your inverter will need to be about 4000W minimun, 5000W would be better. putting two Prosine 3.0Ks together would work but they're 2K each used if you can even find them.

As a cost/benefit ratio I wouldn't build a system at 5000W just to run the microwave once in a while.
If you just turn off the portable AC when you run the microwave then it's more manageable and you can stay with a 2500W inverter.

Running just your AC and fridge at 120VAC and 10A continuous, your 300Ah batteries will last about 3 hours in theory, I'd guess 2 - 2.5 in practice.

10A x 120VAC = 1200W x 3 hours = 3600Wh /12VDC = 300Ah

If you want to run your AC and fridge all night (12 hours) you're going to need 1200-1500Ah of battery bank.

Not only is that going to be expensive you're probably not going to charge that much battery with your alternator and a few hundred watts of solar on your roof.

So you're going to spend thousands and still need to run your genny.

 

[Non-partic]

Thank for the additional information and perspectives. It's becoming more clear:

* Residential refrigerators and air conditioners kill the effort to go green no matter what the cost.

* And when you say the inverter needs to be 2x your peak power requirements x10 then that means my 26A demand (on occasion) will require a 5000W inverter if I have a single power grid.

==> So maybe having 2 power grids does make more sense?

==> But even with 2 power grids, in my case we are still just talking about running 1 small, 8,000BTU portable AC, which is better than nothing, but I know in the sun an RV need a lot more AC to be comfortable inside. So, why bother?

...And after this much analysis, why do so many people think this nation can survive with out fossil fuel?

This green hype seems impractical and too expensive for me, and I'm really trying to accept the possibilities.

At this point I'm going to shelf this project, because I know where I like to vacation, in 90F+ weather, I will need either my generator or shore power to vacation comfortably.

Thank you for all your help.

 

[JayArr]

You want to vacation in 90+ degree weather but you also want to run your air conditioner all day and night. That's quite the dichotomy!

Maybe I don't understand, do you want to vacation there because it's 90+ or do you want to vacation in a spot for other reasons and you have to put up with 90+?

If you vacationed somewhere where it was only 72 degrees you wouldn't need the AC and you could run the whole rig on the equipment you already own.

 

[Ex-Calif]

...And after this much analysis, why do so many people think this nation can survive with out fossil fuel?

This green hype seems impractical and too expensive for me, and I'm really trying to accept the possibilities.

At this point I'm going to shelf this project, because I know where I like to vacation, in 90F+ weather, I will need either my generator or shore power to vacation comfortably.

Thank you for all your help.

My brother's house is basically off grid. He's hooked up to the utility but he is a net contributor of power.

He's built his grid himself over time.

A lot of these threads start off with - What inverter do I need to run 2 A/Cs, a microwave and a coffee pot?

The first question in any battery based system needs to be, "How much power am I planning to use and how will I replenish it?"

When you realize that you need a lot of solar, you then discover the efficient way to manage it is at 48V and above.

 

[Non-partic]

Right. I sorry to conclude: Going green is not for everyone and certainly not for many RVs who have a residential refrigerator and need AC for whatever reason.

Maybe I should have said sunny weather higher than 75F and relative humidity of 40% or more. Because anytime you have direct sun beating on your RV above 70F it's going to get hot inside. So forget I said 90F. I was just on a roll.

Consequently, I don't see an affordable or cost effective reason to spend big bucks to go solar or LiFeP04 in an RV unless you plan to own it for 5+ years. However, I may relook at this equation if my inverter or FLA battery bank need replacing.

Many thanks to all for sharing you knowledge on inverters and the like.

 

[Grid Point Designs]

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[Contributor]

Maybe I'm wrong but it seems to me that there is no GROUND in 12 VDC systems. To me GROUND is only used in the 110 VAC system of an RV. Grounds are there for safety they do not to carry any current. When not connected to shore power, the RV has no ground reference, nor does the chassis. The 12 VDC battery system is "floating" and can be at any voltage it wants to be. So if the chassis picks up a static charge and is floating at , lt's say 50 volts, and the battery negative post is connected to it, then the negative post is at 50 V and the possitive is at 62.7 VDC. But the RV system is still operating at 12.7 VDC.

When we talk about 12 VDC systems in an RV, the proper term is RETURN. The RV chassis is used as a path for the RETURN of current from dc loads. If the negative side of the converter is connected to the chassis on one end, and the battery negative post is connected on the other, this is to provide a return path for the current flow (signal return).

Since the 110 VAC system is used to power the converter on other AC accessories, it needs to provide a ground path for current in case a short in an accessory occurs. To prevent the 110 VAC system from "floating" a ground rod is buried at the voltage drop and the neutral is bonded to it. This provides a reference so that all AC circuits are at the same potential.

RV manufacturers bond the AC ground wire to the RV chassis and usually bond the converter 12 VDC negative output to the same spot on the chassis. At this point, the chassis is connected to earth ground but no current flows to the earth. The returns work their way back to the converter.

Just a pet peeve of mine when folks use the term ground loosely.