Looking for advice on backup configuration for grid, generator and battery without solar at the moment

jbird526

Solar Enthusiast
Have a backup generator that was given to me, a Champion 7000 watt and yes I know its not a great unit but was free and practically new. Perhaps a power conditioner could help on that? I have heard conflicting reviews about if one is necessary or not.

Considering adding a manual 30 amp transfer switch to run a few circuits like refrigerator, natural gas boiler circulation pump, a few lights, etc. I have installed a manual Generac transfer switch before and not a big deal but thinking I would like the option at night to not have to run a generator and instead run off a LiFePO4 battery pack.

I am NOT considering adding solar at the moment but perhaps in the future. What would be a reasonable configuration to run household items off the generator during the day while also charging the batteries and cutover to battery power at nigh?. Nighttime would be lower consumption restricted to "just the essentials" like refrigeration and household heat.

Have built 100ah Prismatic 12 volt packs before so moving up to more efficient 24 or 48 would be in order, but never really dealt with grid, generator and battery all at the same time. Trying to get my head around the best config. Again manual cutover not an issue to cut down costs.
 
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Just John

Photon Sorcerer
Other than it not being pure sinewave, there is no problem that I know of with the Champion. My 3800 watt gas/3420 watt propane Champion handled a couple of weeks running a 10,000 BTU air conditioner, refrigerator, television, TiVo, and some lights. If you have a transfer switch, even better. Hurricanes suck, but propane in 30 lb bottles doesn't go bad, and gives you time to find a gas station with power and gasoline. You can run quite a bit with a generator that large, and have plenty left to charge up batteries.
 

ePowerBank

Solar Enthusiast
@jbird526 You still considering this?
I'm working on exactly what you're talking of.

I'm calling it Active Sump Backup & Passive Home backup.
Plan to have genny's (2 x 4500kw 120/240v parallel inverters) running on NG so I figure there's no worries for a long long time.
I measured my winter time overnight usage like you say - and figure 10kwh let's me shut of genny''s for 10 hrs.
I'll be using I think Magnum MS-PAE 4448 Inverter with 48v 280ah LiFeO4.

Plan on having essential panel for the Active Sump backup, then using transfer switching into a Interlock into main panel.
Only thing I figure I won't run is AC & 240v oven which is fine in a backup scenario.

If you're not sure on your KWH overnight, you can just track with your meter a few times to get an idea.
 

jbird526

Solar Enthusiast
@ePowerBank Thanks for following up on this. Have been thinking about this but no progress so far.

So I have some questions that I have not had answered so far.

Is it possible to have a transfer panel that is only supporting 120v? In searching, seems most or all are 120/240. Can I just make sure that the only circuits I need to power by inverter or generator are off only one leg of the main panel?

At most I only need 4 circuits so far. In looking at my consumption, have charted the following using Emporia VUE and app.

Furnace - 1100 watts per day
Refrigerator - 2400 watts per day
First Floor - 3000 watts per day
Aquariums - 2300 watts per day

The peak watt usage at any given time of all of those appears to be @880 watts. Most of the time will not be using that high a wattage at one time, so figure a 1200w inverter will be fine.

I have no idea if this setup is possible, all depends on if transfer can be 120v only. I'd rather not build up to a split phase inverter yet, maybe in the future.


Screen Shot 2021-05-17 at 3.47.41 PM.png
Maybe this would just be a simpler setup since I need a new inverter anyway.

Screen Shot 2021-05-17 at 5.33.38 PM.png
 
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jbird526

Solar Enthusiast
Actually I just lied in the previous post. I did find a YETI 120 transfer panel. Pretty sure it is just a Reliance TP that they are branding as theirs.

Goal Zero

Similar can be found here for cheaper. Nature’s Generator Power Transfer Kit

Just need some advice on how to best layout breakers in the main so only pulling off of single leg. Breakers would alternate if I remember reading correctly?
 

ePowerBank

Solar Enthusiast
Like always, there's more than one way to solve a problem....
Please don't take me for the expert here - I'm not electrician - just a DIYer trying to set up something for 1st time.
Assuming you're new to this, I'll try to cover some details here, as I understand. Please feel free to anyone where I may be off.

While our idea isn't "totally" unique, I think it's a bit unusual: A backup system using DC/Inverter and not solar. Your Yeti reference is a whole new emerging market segment - and quite interesting.

Correct me if I'm wrong here, but I think this is how our two plans compare to each other:
What we have in common:​
- Use generator during daytime power outage​
- Utilize some type of essentials panel​
- Night time back up power via Inverter / Battery bank​
- Not have solar now, but maybe in future​
What we don't have in common:​
- I'd like 240v at both legs of primary panel​
- You'd like 120v to 1 leg only (I'm not sure why?)​
- I'd like auto transfer to my essentials (the switch in your link is manual type)​
SIZING:
I think what you need is night time usage, not your total 8.8kw/day I think you referenced above. I checked my utility meter outside to confirm my overall overnight usage - easy.

Typical US home consumes roughly 30KWh's / day I believe, and about 1/3 of that at night. I confirmed with my heater running in Michigan in winter that 10Kwh was more than enough for an evening of energy - in my case.

Figuring 9KWh was my night usage, I ordered 16 each 280Ah LiFePO4 cells, yielding ~ (280ah x 48V = 13,440W), or at 60% DOD 8KWh, or 65% DOD for 9KWh.

For my inverter I wanted to consider a worst case over night + not worrying about someone getting up in A.M. and turning a microwave etc, hence my 4kw plan. Also keeping in mind while my evening low usage may be in the sub 1000W range, worst cases are motor start ups, like heater or fridge you mention on your essential list.. Key I think is double and round up. I suggest you consider more than 1,200W inverter.

The other thing to consider along with inverter size is inverter voltage, trying to keep well under 200A if possible, so my case is 4400w/48v=92A.
If I did 24v I'd be in the 200A plus club (not accounting surges). This means wires, switches BMS etc all need to be double duty... gets expensive and scary real fast IMHO.

For generator sizing I think it's 1.5 times Inverter sizing you should consider. I'm "trying" to get two 4.4kw Inverter Generators and connect in Parallel, and run off Natural Gas. At about 80% derating for natural gas I'm figuring 7.2kw peak power, or 1.6 times my 4.4kw inverter. Been on backorder though since Feb - quiet, small, parallel option, 240v so I could hook 1 or 2 - is what's checking my boxes.

You need the extra (1.5x) generator power since you want to be able to run things in power outage "plus" be charging battery bank for your next evening if that's your plan.

BTW, for the 120V you mention, I'm not sure why you're thinking 120v. Is your generator 120v or 240v? I'm guessing you know that 240v is just 2 legs at 120v. See below for more on why I want 240v.

SYSTEM PLAN:
If you're like me, this can be a bit confusing at the start trying to understand how things hook up and the options.
More importantly, if you're not knowledge about electricity, BE CAUTIOUS.

Basically there are a some basic options for alternate power to enter our existing system(s), including:
1 - Interlock system (what I'm planning)​
2 - MTS (Manual Transfer Switch), or switches: Some have alternate power "hard wired" into box like what I plan (https://www.amazon.com/Reliance-Con...ocphy=9016962&hvtargid=pla-275671553035&psc=1).​
Other MTS's, like example you ref'd above, can have alternate power "plugged" into box and switch devices individually: Nature’s Generator Power Transfer Kit. This is pretty tradition way to hook up a generator, but didn't check all my boxes.​
3 - ATS (Automatic Transfer Switch), basically what UPS system does, the moment grid power goes down.​
In my application I'm thinking to use:
#1 option (Interlock) to "lock out" grid power into my panel and turn on alternate power into panel (which also leads to my sub panel with additional 25 breakers)​
#2 option (MTS) to switch power from one of two sources. For my case I have MTS to Main and another MTS to Inverter (this is where it gets tricky). IOW, I can supply my Main "via my interlock" with either Generator or Inverter power for example. Manually.​
#3 option (ATS) Isn't in my plan (more $$ and not as reliable IMO), but is a feature "in part" in most inverters (more on that next).​

My plan will be traditional "in part" when it comes to the inverter feeding a small subpanel, or the essentials (sump pump).
This panel will feed my sump pump all the time, where the Inverter will power it with either grid-AC (what they call pass-through), or DC inverted to AC like a UPS (power outage / automatic back-up even if I'm out of town).

I'm adding the additional MTS to feed the inverter with either grid-AC, or Generator power if grid goes down.
When I switch my interlock, I'd incorporate secondary feature that forces off grid-switch to inverter - otherwise I'd be feeding inverter with it's AC.

The advantage of my plan is that I can distribute the 4.4kw backup power across both my Main Panel (25 breakers) and Subpanel (25 breakers) - why I want 240v or split phase.

A second option (more traditional) way is setting up Subpanel & selecting essentials. I see 2nd option as being a large rip-up for me and spending towards $10k + for something - I MAY NEVER USE? BTW, my subpanel is about 30 feet from main panel, why I say rip up.

Yes, I could exceed that 4.4Kw real fast with 50 breakers, but I'm willing to put the manual part in this process for backup only. I can live without things like 240v oven or Air Conditioner (live in Michigan and basement is always cool) - have ceiling fans everywhere. Tracking my usage with the SENSE system I can see that 4.4kw will go a LONG ways.

Yes, I could put a whole house backup generator in but I hear those can be a $$ pit. And, if I move I take my portable geny's and probably the inverter system.

I hope this helps you more than it confuses you. I've spent quite a while chewing on this and appreciate everyone's application is unique. It was cool to see you start this post as it's the closest I've seen to my case.

Attached is illustration of my plan, thus far... if this is how I go.
1621307583597.png
 

Attachments

  • Inverter Backup Plan 2021 0517.pdf
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jbird526

Solar Enthusiast
What we don't have in common:
- I'd like 240v at both legs of primary panel
- You'd like 120v to 1 leg only (I'm not sure why?)
- I'd like auto transfer to my essentials (the switch in your link is manual type)
The differences that we have are mainly due to cost. My intent is for a small "life support" backup. That is why I have listed: furnace, refrigerator, fish tanks, some first floor circuits. I have a 240v electric range but also 2 propane grills outside.
The reason I am only specifying 120v is that I am not planning on utilizing any 240v circuits during this period. I know I am probably being short sighted but perhaps if I have the realization on smaller system, I can think about scaling up.

Everything that I took readings for were for an entire day, you are correct. For the most part all of those circuit usages are the same regardless of day or night, so figure just divide by 2 for required nighttime wattage needs. As night will usually be a bit colder, figure a bit more usage on the furnace and aquarium heaters so need to take that into account.

Have also thought about a Growatt 24v 3000w as that would already have an mppt for later hookup and at $800 is a reasonable price.

One thing that WE need to think about is the fact that LFP cells should not sit at a high rate of charge for prolonged time and as far as I understand best to sit at 50%. Either keep at 50% or cycle at some interval has been suggested.

BTW, for the 120V you mention, I'm not sure why you're thinking 120v. Is your generator 120v or 240v? I'm guessing you know that 240v is just 2 legs at 120v. See below for more on why I want 240v.

My generator does have 120v and 240v output so I would have the option to upgrade to perhaps string 2 of the Growatts together for 240v. It all comes down to how much I really want to spend for backup power. I need to sit down with my spreadsheets and add all the details and costs.
 

ePowerBank

Solar Enthusiast
My project (problem) started when my sump back system needed a new battery... and now I'm up to over $7k. What just happened.

I do have a fully finished basement (kitchen / office / IT etc) and when sump is pumping full rate it's pushing about 700 gal's/hr.

Recently power outage of 80 homes was almost to my next door neighbors, the night after I was pumping that rate.

So I figure a portable backup system for $7k keeps me comfortable not only in power outage, but if we're out of town - when new basement is probably $75k.
 

ePowerBank

Solar Enthusiast
Have also thought about a Growatt 24v 3000w as that would already have an mppt for later hookup and at $800 is a reasonable price.
I gave up idea of Growatt due as it seemed a bit sketchy for service etc. Yes, feature rich and cheap! Also, old school says low frequency inverters is the battle tested design vs high frequency - I have to guess eventually that won't make a difference, but for now it scares me. Personal preference.
 

ePowerBank

Solar Enthusiast
One thing that WE need to think about is the fact that LFP cells should not sit at a high rate of charge for prolonged time and as far as I understand best to sit at 50%. Either keep at 50% or cycle at some interval has been suggested.
Agreed! I was planning on 70% (60% - 80%) then cycling every other month.
 

ePowerBank

Solar Enthusiast
Poor man's no switch version ?
Only problem it doesn't act as UPS backup to my sump pump, but maybe an option for you?
Common practice for this would be have list of what Main breakers to turn off - if in backup mode.

1621361534745.png
 

jbird526

Solar Enthusiast
My project (problem) started when my sump back system needed a new battery... and now I'm up to over $7k. What just happened.

I do have a fully finished basement (kitchen / office / IT etc) and when sump is pumping full rate it's pushing about 700 gal's/hr.

Recently power outage of 80 homes was almost to my next door neighbors, the night after I was pumping that rate.

So I figure a portable backup system for $7k keeps me comfortable not only in power outage, but if we're out of town - when new basement is probably $75k.

May be cheaper if you purchase a pool filter and start doing the backstroke in that basement. :)
 

ePowerBank

Solar Enthusiast
I'm still on the fence, and want to just jump.
Seems having reliability comes with a price tag - not surprised.

My 48v inverter list goes back and forth, including:
Magnum 4.4KE ~ $3k adding the whistles n bells (battle tested and #1 RV go-to as I understand). Longest standing 20yr design (good/bad), so most mature documentation IMHO​
Outback Skybox 5KW~ $3.3k (not counting price creep?) 20 year newer technology than Magnum, solar ready and very user friendly​
Deye 5KW ~ $2.4k ish basically SolArk - no US support ? Very interesting feature set for the $$, but I need support​
Growatt 5kw ~ $900ish + 120v transformer .... why why why wouldn't i buy this for the $ ? Less cost, less service, less ??​
To make matters worse, the BMS options and choices are even harder. Designs options are all over the map depending on so many things.

One BMS driver seems to be staying under 100A - options/designs/prices change real fast once over 100A.
This causes me to think Magnum gets a big check with 4.4KW (4440w/48v=92A). Good wattage for what I need, and may be able to sneak by with 100A Overkill Solar.

My Magnum score: High price (for the technology)/low technology/Hi reliability/Proven/Hi Service
My LiFeO4 cells aren't due until early July, so I'd like to order Inverter/BMS shortly.

So that's the latest, but not sure the greatest ?
 

wattmatters

Solar Addict
Have a backup generator that was given to me, a Champion 7000 watt and yes I know its not a great unit but was free and practically new. Perhaps a power conditioner could help on that? I have heard conflicting reviews about if one is necessary or not.

Considering adding a manual 30 amp transfer switch to run a few circuits like refrigerator, natural gas boiler circulation pump, a few lights, etc. I have installed a manual Generac transfer switch before and not a big deal but thinking I would like the option at night to not have to run a generator and instead run off a LiFePO4 battery pack.

I am NOT considering adding solar at the moment but perhaps in the future. What would be a reasonable configuration to run household items off the generator during the day while also charging the batteries and cutover to battery power at nigh?. Nighttime would be lower consumption restricted to "just the essentials" like refrigeration and household heat.

Have built 100ah Prismatic 12 volt packs before so moving up to more efficient 24 or 48 would be in order, but never really dealt with grid, generator and battery all at the same time. Trying to get my head around the best config. Again manual cutover not an issue to cut down costs.

Not that my scenario is the same, but I had installed a manual cut over switch and power inlet into which I connected a Yamaha inverter generator to use during grid power outages.

I've now built an alternative battery-based supply using one of those all in one hybrid inverters and a bank of pre-loved sealed lead acid batteries. The generator is now the backup to the backup, should the outage be an extra long one requiring it.

I wrote about my set up in two posts. An introduction here:

and more details on the battery based system here:

Good luck with it.

It's been a fun and learning experience.
 

ePowerBank

Solar Enthusiast
What an interesting case you've shared for me at this time.
While I find some just starting the "backup only" journey, or others so qualified to offer advise, it's so rare to find ones on the other side as you.

My scope is so similar to yours - backup DC/AC power enters panel like a generator - and keep it simple!
I look forward to reading anything more you may have to share on your energy adventure!

I've picked 48v of LiFoP4 batteries - due early July, but yet to pick inverter and BMS.
I'm realizing that if I tip the scale and go over 4KW inverter, the BMS is tougher topic as it goes over 100A.
In summary, under 5KW is a sweet spot IMHO for us beginners !

Thanks again for sharing !!!!

PS, pictures cause envy for more reasons than one - beautiful.
 

wattmatters

Solar Addict
My scope is so similar to yours - backup DC/AC power enters panel like a generator - and keep it simple!
I look forward to reading anything more you may have to share on your energy adventure!

Yes, many systems are complicated for beginners.

That said, each person's scenario is unique and requires a solution suitable for their specific circumstances.

I will be adding a 2.5kW solar PV array to supply the off-grid battery so it can charge/re-charge from that, as well as take the pool pump off-grid while not jeopardising its primary function of being a backup power supply. Indeed the solar PV array should enable the backup duration to be extended during outages.

I have pretty much everything for the solar PV project, although I haven't gone to collect the panels yet. The solar PV part of the project is going to be a more physically demanding project compared with the battery/inverter.

I'm pretty ready to start that project, just need some fine weather. Later next week I think.

What tends to happen with these things is scope creep and cascading issues. Before I even get to putting the mounting rails on the old garage roof, I need to do a little rust removal on the metal roof and prep it. And put a tow bar on the old car so I can use a trailer to go and get the panels because they won't fit inside the car. But that requires ensuring the car is up to it, so then it's a case of having it checked and getting any necessary repairs/upgrades done. And so on it goes...

I'll update that thread as the project develops.
 
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