Keep your home powered during an outage? Try a big battery that lasts 3 days | Hacker News Reader

Keep your home powered during an outage? Try a big battery that lasts 3 days

cbc.ca

12 pointscf100clunk23 comments

In the 90s, I had a couple of army surplus missile silo batteries. 1500lb each. and an 800lb forklift battery. With those charged up and bunch of ebay UPS systems wired to them, we had ~3kw for computers for 2 or three days.

Generac-type natural gas electrical generating units wired into the power panel are increasingly popular in new housing developments of a certain financial range, and retrofitting of homes with those is happening too. Presumably the gas companies are expected to have functional pumps even in electrical outages. If a solar charged battery system like the Sunverge is used there is no dependence on external sources during an outage.

We got a Generac on our gas line installed and it's had about 5 uses so far... it's incredible. A battery system sounds pretty interesting too, but if you have the gas line already and are planning for normal outages (not prepper stuff) then for convenience, power and automation I doubt you can beat a good generator.

You’re probably fine without a battery as long as you don’t live in Texas. During their big winter power outage a few years back, all of the natural gas distribution was offline when the power went out.

The problem with the Generac solution as that there's still a 7-10 second gap between the grid failure and the generator coming online.

Good point, and it means the budget for a Generac-type system should include UPSes as needed to cover anything time sensitive.

What household load would be critical enough that it needs to be backed up by a generator and UPS? I can’t think of anything.

By household load I guess you aren't talking about the usual UPSes for computers & network gear, home entertainment systems, etc. where continual availability might be wanted.

We were out in the woods with no budget; donated surplus, redneck engineering, and a willingness to learn by burning was what got us through.

zap and hafta go peel a snake out of the bus bars in the battery shed

How safe would something like this be? It has a lot of appeal to me but I'm already getting nervous about battery fires as it is.

I posted a link to the spec sheet in these comments and the certifications are shown. If your concern is the Li-Ion battery itself, that's a fair question.

I would definitely build a separate shed out of concrete blocks to keep it if allowed.

Concrete blocks are not tolerant of certain heat ranges (they can crumble) so maybe some extra hard portland cement would do the trick? A cistern filled by rainfall or garden hose could be built of the same material just above the battery compartment with a quick drain to totally douse the battery if needed.

Water can be problematic in lithium fires.

Maybe the upper chamber would need to be a hopper full of suitable material to try to contain a Li-Ion fire.

The concrete shed will be ok during normal operation. It would be there just to protect the battery from the elements and to make sure it wouldn't burn down my house should it enter thermal runaway.

It would be for the same reason I have my generator and its fuel in a dedicated shed today.

For the love of god insulate a shed if you must use one

The temperature swings won’t just hurt performance but risk thermal runaway if severe enough

Good point! But that shouldn't be too hard. Probably easier than soundproofing a generator shed.

If they're LFP batteries, then they should be pretty safe. That chemistry has a much higher bar for runaway fires.

LiFePO4 is extremely underrated in conversations about Li-ion. They are my go-to unless I need high power density high drain

Particularly larger LiFePo4 cylindricals and prismatics are fantastic. They have surprisingly good quality control despite almost entirely coming from largely untraceable Chinese manufacturers

As long as you have voltage and temperature monitoring with either a relay or preferably a power-fet for each and every cell it is safe and reliable

This approach is much easier for prismatic cells but I have seen it successfully done with cylindricals

Here are some facts about the BYD Seal EV:

- A Seal costs around $66k in Australia, before any subsidies.

- A Seal has a 80 kWh battery.

- BYD says the LFP batteries in the Seal should last around 25 years.

- BYD says they will ship a Vehicle to Grid kit (ie, when they do it can become a house battery). They already have a 3 kW "mains" power point in the car.

- I don't know how safe it would be, but in Australia people generally park their cars in a garage that is part of the house.

House consumption varies a lot, but if you remove aircon, pool filters and the like, 20 kWh / day will probably do you. So the Seal's battery should last 4 days.

In comparison, house batteries in Australia cost around $1000/kWh installed. If prices at the same rate a Seal should cost $80k for it's batteries, and you get a car thrown in for free.

Sunverge AC-Coupled Solar Integration System Spec Sheet [pdf]:

https://cdn2.hubspot.net/hubfs/2472485/Website%20Content/Sun...

Reply on news.ycombinator.com