Home battery

[CountAllVotes]

Hello out there!!!

Does anyone have any experience with a "home battery"?

Apparently one of these can keep your home powered for three days in the event of a power failure.

You have to run it every day whether you need to use it or not in order to keep in charged.

They cost around $15,000.00 and are installed by a person that is specially trained to do it.
By the time you are done with it, the cost is $28,000+ because of the installation costs.

A home battery is said to last for 10 years and it needs to be replaced after that.

Any help at all is appreciated.

Thanks very much.


On edit: More about it here: https://electrek.co/2020/03/20/tesla-powerwall-extremely-demand-california-incentive/

This is an old article from 8 mos. ago but it sounds like the same thing. Thanks again!!


CountAllVotes

[SheltieLover]

1. I use a power inverter connected to car battery

Quick, cheap & easy to keep charged.

This keeps fridge, internet & computers, & lights on during outages.

Sorry, no knowledge of a home battery.

[better]

2. While I'm not an expert, I do know a fair bit about this. Feel free to pm me!

It can be done for MUCH less than $28k.

I've even gone so far as laying up a few drawings for a modular battery system of my own design.



I've been designing my system to be housed in 2u rack chassis, similar to a computer server or audio amplifier. This one, in particular, is designed to function as 4 strings, each providing 210AH of storage capacity at 3.2v, which if wired in series would work out to a 12v 210AH pack in each 2u chassis. Wire 4 such chassis together in series, and you'd have a 51.2v (48v nominal) 210AH pack, in 8 rack spaces. Total cost of materials works out to probably something like $500 per 2u chassis. Give or take a bit, as I haven't priced in some smaller costs like bus bars, connectors, etc. yet.

We can go into much greater detail privately, if you're interested, but this same chassis could be configured several different ways, by grouping the cells differently, for example as 6 parallel strings of 20 cells, 12 strings of 10 cells, etc.

[Timewas]

3. Would be cheaper and easier

To just install a backup generator that comes on automatically when power fails...

https://www.toolnut.com/generac-7172-guardian-10kw-home-backup-generator-with-16-circuit-transfer-switch-wifi-enabled.html?utm_source=google&utm_medium=shopping&gclid=Cj0KCQiAkuP9BRCkARIsAKGLE8UMAfPAi7UphZyJdEVh2WGgVg78K-x0SvOhIf8LvE3cr5Hxwm6XdTUaAgJOEALw_wcB

[better]

5. Definitely some merit to this for purely backup purposes, however...

There are some potentially considerable advantages to having a battery system, especially if your utility charges different rates during peak and off-peak hours. You can run your home from battery during peak hours, and recharge during off-peak hours. Further, if your battery system provides more capacity than you use, and your utility offers net-metering, you can actually feed power back onto the grid, and be paid for it.

[Timewas]

6. Yes but

Last edited Sat Nov 21, 2020, 12:55 PM - Edit history (1)

The cost differential is pretty high, you would have to save quite lot to make that up..I can install my own generator so that cost is minimal compared to the battery system..And as is noted in another post a normal car battery or deep cycle for RV's can do the same job much cheaper.. I personally use a generator but not an automatic system I just start it when needed and flip one switch...and my entire investment is well below most of the others at about $450..

Admittedly the system is not as good overall as the one you are talking about but it balances for me...I would have to be in dire need of power, for instance living in a cold area and be in danger if the power went out for any length of time, to invest that much.. I also heat with wood.


It comes down to how important the need for instant as compared to a short time period to turn things on.. About the only thing that is jeopardized quickly is computer use and data and that can be covered with USP which are fairly low cost anymore. Or in the case of needing power for health related necessities

[better]

9. Oh, I agree, and I'm not at all knocking your solution. Just covering the options and their uses. :)

Naturally, cost-benefit ratio does depend heavily upon the requirements and usage scenario. Obviously, it's also very different if you're talking about powering just a few critical loads versus supplying/augmenting power to the entire property.

My scenario is in a rather cold climate, and also for a building a good ways from my house, where the grid connects, that does not have adequate power for my needs even when the grid is up, so I'm looking at a hybrid solar solution, capable of off-grid operation as well as grid assist (but not net-metering).

The one thing I would add to your observation is that it can very easily be worthwhile to use LiFePo4 cells over a standard car or deep cycle battery, for any type of system, for several reasons. They're safer, last longer, have greater discharge capacity, and lend themselves well to incremental replacement, since the cells don't tend to all fail at once, so rebuilding them can be far cheaper than replacing a single deep cycle battery of equivalent storage capacity.

The version in my rendering uses a total of 120 cells, so assuming several years into their use, I needed to replace say 10% of the cells to restore the capacity, I'd be looking at a cost of around $40, since the individual cells are only about $3 each. Compare that to $400 for a comparable deep cycle that's either good or bad as an unserviceable unit, and that's where they really start to look appealing.

You could of course achieve the same capacity with only 4 3.2v 200AH cells at around $110 each with a good deal less complexity, but I designed this model to be highly scalable, for systems ranging from 12.8v (4 cells per string) all the way up to 512v (160 cells per string), so it makes a lot more sense to use the smaller 3.2v 7AH cells in this design, since expanding capacity $480 at a time is a lot more manageable than doing it $17.6k at a time!

[Disaffected]

14. Was wondering,

where you source your cells, especially for $3 each. Thanks.

[Locrian]

7. maybe ....

but at close to 10x the price of the fairly proven natural gas backup generator?
I'd also seriously question whether 3days is "good enough". The generator will work as long as nat gas is available.

[better]

10. No argument there.

For simple backup during temporary outages, a natural gas generator is pretty much undoubtedly the more economical solution, for sure.

But for anyone who does want battery backup for functionality like load-shifting to off-peak rates or net metering, there are options with much lower startup cost than the system OP mentions, which is what prompted me to chime in.

And of course, they offer the potential of completely standalone operation, long-term, with no per-hour operating cost, when combined with wind or solar for battery charging. And once they reach a certain scale, they can eliminate the need to pay for electricity entirely. They do have their place, though they're of course not the right solution for everyone's needs.

[better]

4. A couple afterthoughts...

One thing to consider is that especially if you build your own battery pack, you will probably not need to replace ALL the cells in the pack at once. What happens is that individual cells within the pack will degrade differently, due to minute differences. Most notably, you want to keep the cells balanced, which works in two ways.

In the rendering above, all the cells in each of the 4 strings represented by the alternating red and green plates are wired in parallel. The trick here is keeping all of the individual cells in that parallel string balanced with each other. Simply connecting all the cells together in parallel will cause them to balance among themselves, to the extent they are of matched capacity.

The individual parallel strings, then, need to be balanced to each other in series. This is generally done using a BMS (Battery Management System), which come in varieties supporting 4/8/16 strings (12v/24v/48v) very commonly, though there are considerably more expensive versions that can handle hundreds of strings, which would be necessary for high voltage battery packs.

Bottom line, though, it's highly likely that when it comes time to start replacing batteries, you might only actually need to replace a small percentage of the individual cells that make up the battery. It can be a bit time-consuming, but you can pretty easily design a battery pack in such a way that one set of strings in an array can be removed from service at a time, leaving your battery still functioning, just with a temporarily reduced run-time.

[3Hotdogs]

8. Thought on battery vs natural gas generator.

Hurricane Sandy (2012). Electricity was out for 11 days. We had hot water and gas heat to cook during the 11 days.

[Timewas]

11. For me

No natural gas available at my place so would have to go with either propane or diesel. Probably would go to diesel just for the fact that in "world" wide breakdown there is the possibility of creating your own biodiesel. That is probably not going to happen in my lifetime but is a faint future possibility

[mac2766]

12. I have a 10 kW LG Chemlite battery....

When I had solar panels installed, I had the battery installed with it. It's nowhere near enough to run the whole house, so I segmented 8 circuits in the house to switch to battery when the power goes out. It's been a little over 3 years, and the power has only gone out a few times. The last time was after Hurricane Sally. The battery worked as it should have. I had television, Internet, telephone service, lights, refrigerators, etc... All good, but no AC.

Having said that, If I had to do it over, I'd get a whole home generator installed for much less than the battery. The Chemlite battery cost me 9,500 dollars. Just for the battery - not including the cost for installation. A whole home generator would power the AC system as well as my water pump. In order to do that with batteries, I'd need to add quite a bit of capacity. I'm not sure even then that the batteries would be able to handle the loads of either my AC system or even the water pump. The demand of those 2 systems might damage the batteries.

I'm sure in years to come, battery technology will improve to the point that a whole home backup system will make sense, but right now, coming from a person with a bit of experience, I'd advise anyone to look at a generator rather than a battery system.

Also, I installed a solar system - a single 100w panel, a charge controller, inverter and a 100 wH deep cycle batter in my shed for power out there. I power a couple of lights in the shed, one outside motion sensor light, and have 2 receptacles installed. I'm sold on solar and on batteries, but not for a whole home situation.

It was kind of nice having the battery though. I believe the power was out for 4 days or so after Sally. The neighbors brought me their phones and gadgets for re-charging. In return, they filled my 5 gallon buckets with water. They're on city water. For some reason, the city didn't run the line down the road to a few houses down here so we're on well water. Free water is nice, but when the power goes out, the well pump goes out. Not good.

[CountAllVotes]

13. Update on this situation

I decided to forget it.

The individual pushing this claimed COVID was the flu and that masks were not necessary.

I thought about this a lot and I decided that I wanted nothing to do with people of this ilk.

I may have screwed myself, I don't know but by continuing to support people and businesses like this, we (yes WE) are only allowing this type of behavior and disgusting information to spread.

So I canceled out this deal as my conscience simply would not allow me to proceed and they are out the $28,000 that they figured they had in their greedy pockets already.

Anyway, it is what it is eh?