Blueprints for backup battery power at home

richardw

New Member
Joined
Feb 21, 2021
Messages
37
I haven't even received the PowMr yet, but I've received a lot of positive input on that unit. I was going to go with a Growatt, but the PowMr version is $250 cheaper. I will pm you the website, because I'm not sure the link will be welcome here not being an endorsed product. I have heard mostly good reviews and better yet the customer service is responsive.
Sounds good! Thank you! Any idea what the "no load" power draw is from that unit?
 
Last edited:
Joined
Nov 30, 2019
Messages
12,211
Now that I have decided to pull the trigger on the new 16 cells, I am seeing less options for 24v inverters. I want to be able to use 4,000 to 5,000 watts from my battery bank. It will be capable of up to 4,800 watts of output, at least. What do you all recommend for 24v? I want good quality, but lowest price I can get. I probably won't splurge for a Victron at this point. Renogy doesn't have any 24v options.
If your 16 cells are big blue 280 amp hour prismatics...
Make 8s2p which is to 8s batteries in parallel each with a 150 amp bms or better.
jbd makes a 200 amp version that should work nicely.
You can comforably pull 280 amps aggregate or 140 amps per battery comfortably in that configuration.
 
Joined
Nov 30, 2019
Messages
12,211
Last edited:

richardw

New Member
Joined
Feb 21, 2021
Messages
37
If your 16 cells are big blue 280 amp hour prismatics...
Make 8s2p which is to 8s batteries in parallel each with a 150 amp bms or better.
jbd makes a 200 amp version that should work nicely.
You can comforably pull 280 amps aggregate or 140 amps per battery comfortably in that configuration.
16 new EVE 304AH cells from Docan

Would two 24v batteries in parallel as I was thinking be better than 48v with four 12v batteries in series?

How does JBD compare to the Overkill Solar BMS devices? I have been happy overall with the 12v BMSs I currently have.
 

richardw

New Member
Joined
Feb 21, 2021
Messages
37
16 new EVE 304AH cells from Docan

Would two 24v batteries in parallel as I was thinking be better than 48v with four 12v batteries in series?

How does JBD compare to the Overkill Solar BMS devices? I have been happy overall with the 12v BMSs I currently have.
Any thoughts @smoothJoey?
 

HARG Hunter

Thirsty for Off-Grid Knowledge
Joined
Jul 10, 2020
Messages
206
Location
Iola, Wisconsin
Are you asking which system voltage to go with between 24 and 48 volts?
I think he's asking if (2) 24v in series for 48v would be better than (4) 12v in series for 48v.
I would think (2) 24v in series for 48v would be better, even though I'm going the other route strictly for financial reasons.
I just couldn't turn down (4) 12v 100ah lithiums for $300 each.
 
Joined
Nov 30, 2019
Messages
12,211
I think he's asking if (2) 24v in series for 48v would be better than (4) 12v in series for 48v.
I would think (2) 24v in series for 48v would be better, even though I'm going the other route strictly for financial reasons.
I just couldn't turn down (4) 12v 100ah lithiums for $300 each.
If he has 16 cells for 48 volt system he should use a single 16s bms to make 1 battery.
with a bms rated for 100 amps he could use an inverter up to 4080 ac watts continuous.
Or with the right inverter and a smart battery protect he could go up to ~6000 watts continuous.
A single battery with a single BMS makes for a simpler system that is easier to implement and manage.
The trade-off is a bit of redundancy.
In this case I think the simpler the better.
 

richardw

New Member
Joined
Feb 21, 2021
Messages
37
Sorry, I didn't realize there had been any responses yet. I am interested in what would be better for my situation - 12v vs 24v vs 48v. I am seeing that there are not as many options for 24v equipment as there are for 12v and 48v equipment, it seems. One of my requirements is going to be redundancy in the batteries, as well as other components. My reason for building the backup battery system is for emergency preparedness. One 48v battery would not meet this requirement so I would have to spend another $2,200 to have sufficient cells to have two 48v batteries. So in this case, I think I need to stick with 12v or 24v at this time. There are lots of 12v options for inverters and chargers and all-in-one systems, etc.

With the cells coming in, I could make another four 12v batteries, which I could arrange to make a 24v system. If I go 24v, I will purchase at least four more cells to have on hand in case a cell (or more) were to go bad in the 24v system. If needed, I could modify the system back to 12v. Unless I go to a scenario where I am trying to run my whole home off of solar, I believe I will be best served at this time and have plenty of battery capacity sticking with 12v or 24v. The downside of 12v would just be the higher amp requirements on the battery side.

I am interested in adding some solar in the future (probably near future) to be able to charge the batteries without depending on gasoline.

What are your thoughts?
 

12VoltInstalls

…myself everything do I…
Joined
Jan 18, 2021
Messages
4,048
Location
Vermont
believe I will be best served at this time and have plenty of battery capacity sticking with 12v or 24v. The downside of 12v would just be the higher amp requirements on the battery side.
What are your thoughts
I’d do some solar now and eliminate the generator other than backup.

You’d be surprised how effective even 1000W is especially if you’re mindful of usage.

How many watt hours are you needing? And the highest load and for how long?

12V systems do have weird little bonuses like the plethora of high quality lighting options from the RV and off grid world, and so many battery things have car chargers available. And though it ain’t best nor a good regular practice you can easily boost your system off your car with jumper cables in a bad circumstance.

If you need anything above 1500- or 2000W 12V starts not being as attractive imho
 

MisterSandals

Participation Medalist
Joined
Nov 5, 2019
Messages
6,260
Location
Silicon Valley
I’d do some solar now and eliminate the generator other than backup.
I am thinking that this is a better direction too. So, instead of buying ($$) and maintaining a second battery bank that is a backup to a backup, use the generator as the 2nd backup.
This allows you to use your 16 cells for a 48V system (doing it right the first time IMHO) and get solar to keep it at the ready and recharge when in use.
 

richardw

New Member
Joined
Feb 21, 2021
Messages
37
I’d do some solar now and eliminate the generator other than backup.

You’d be surprised how effective even 1000W is especially if you’re mindful of usage.

I have been thinking this too! Thank you.

How many watt hours are you needing? And the highest load and for how long?

12V systems do have weird little bonuses like the plethora of high quality lighting options from the RV and off grid world, and so many battery things have car chargers available. And though it ain’t best nor a good regular practice you can easily boost your system off your car with jumper cables in a bad circumstance.

If you need anything above 1500- or 2000W 12V starts not being as attractive imho

I started off on this journey several years ago when I bought two 6v deep cycle lead acid batteries. They gave me the ability to have many hours of light and to charge devices or use my PC or other devices, if needed. However, the lead acid batteries were not great from a maintenance perspective, DoD, and weight.

In planning for emergency preparedness, my initial goal was to be able to power our two refrigerators and freezer for at least 12 - 24 hours so that I would not have to guard a generator through the night. They use approx. 450 watts when they are running. I bought 8 280AH LiFePO4 battery cells from AliExpress based on info found on Will Prowse's YouTube channel and websites. I have been fortunate in that those cells seem to be working quite well. I built the first 12v battery and tested it. I was able to run my refrigerators and freezer for 12 - 16 hours or so and use only about 40% of the battery capacity. I ran it for a number of days by keeping the refrigerators and freezer plugged into the inverter and then charging for about 3 - 4 hours with the AIMS 75 amp charger each day.

Now, I have built the second 12v battery and incorporated it and am testing the battery pack capacity now since I got the cells balanced.

For emergency preparedness and the occasional power outage that occur very infrequently, I want to be able to run electrical devices for food preparation and cooking, in addition to the refrigerators/freezer, lights, and network, etc. These would be used for short periods, but have temporarily high consumption. Of most importance is the microwave, which is drawing about 2,100 watts or so - maybe a little higher. I would like to be able to use the Instant Pot (it says up to 1,700 watts but it is not continuous while in use) or high-power blender (maybe ~1,500 watts on high). The intention would be to use high-power devices individually and temporarily, as needed, for cooking or running tools for repairs, etc.

There is no issue running the refrigerators and freezer, along with the home network, some lights, some computer equipment, etc. When adding in the temporary power draw of the food prep/cooking devices, the number of watts/amps increases significantly for a short period. This is where I could see an advantage with going 24v to reduce the amp requirements during these times. However, since the goal is emergency preparedness, we would also want to be cognizant of our power usage to be frugal with the power consumption.

I want the ability to utilize high watts (up to 6,000 watts would be nice), but for short periods while keeping the overall power draw low for the essential items. Some solar power would be very beneficial, especially during the day to charge batteries and limit utilization of the batteries to preserve them for evening through morning hours. With sufficient solar in an emergency situation, the batteries may not need to be utilized very much.

We live in an earthquake area. In March of 2020, we had a 5.7 magnitude earthquake in the area where I live. It shook our house quite a bit. I believe we will have a very large earthquake at some point in the future. Our home could become uninhabitable. We also have a sewage pump in the basement that would need to be kept operational since our kitchen and downstairs bathrooms are dependent on it. Additionally, if there were a water line break, that pump would be needed to keep the basement from flooding.

Anyway, I don't think I am to the point where I would want to try to run the house off of solar and battery power completely, but I do want the capabilities to have emergency power for the essentials during a power outage or extended crisis situation. With some 12v (and maybe 24v) equipment, we could also take some of these capabilities with us if we had to leave our home for some reason, or for camping, etc.
 
Last edited:

12VoltInstalls

…myself everything do I…
Joined
Jan 18, 2021
Messages
4,048
Location
Vermont
In planning for emergency preparedness, my initial goal was to be able to power our two refrigerators and freezer for at least 12 - 24 hours so that I would not have to guard a generator through the night. They use approx. 450 watts when they are running
Ok. So you do need a big inverter beyond those needs. Maybe an AIO hybrid would be in your best interest- maybe buy a couple extra panels to compensate for inefficiency.

However a hybrid AIO isn’t that portable…

If more temporary power is acceptable perhaps a small inverter for day-to-day and a big one to turn when the big stuff is needed? Just brainstorming.

A decent hybrid AIO with grid assist and then a ?1200W? giandel or something for portability.
 
Top