Battery backup system without solar

[PSPS]

Has anyone built a home battery back up system with out solar to charge the batteries? I'm in CA where the electric company PG&E turns off the power for wildfire safety. I was looking to build something that could power a full size refrigerator, a few lights and modem overnight, then I could charge the battery during the day with my Honda 2000. I know I can buy a Goal Zero, Patriot, or Inergy solar generator but they all seem to be priced much higher than you can build one. Any thoughts?

Thank you!

 

[Rider]

Sure, no reason why you can't. From personal experience, you need about 200Ah of battery (assuming lead acid AGM, lithium can nearly double your available run time) to make it thru the night with a full size fridge, but I'd build in a little more capacity than that. A 1500-2000w full sine wave inverter will power it nicely. Might take a while to recharge using the genny, but it will work.

If you were to add a few solar panels and a solar charger, you could improve your charge times and lessen your genny and fuel usage. Never know when those blackouts will turn off the local gas stations....

 

[johnzilla]

I am in the process of building a home backup battery bank myself (as a total rookie). Just curious, why would you charge your battery pack with a generator? AFAIK that's the most expensive and least efficient way to do it. Why not just charge from the grid? That's the same thing a Tesla Powerwall does and even at CA PG&E rates, the cost of the grid power should be much cheaper than the cost of gasoline for the same power. Then you wouldn't have worries about noise, exhaust, heat, etc.

Will has a Youtube video on comparing the Goal Zero and Inergy with lithium, lead-acid and others which might be helpful with respect to cost comparisons.

Either way, as a newbie I think how your bank is charged comes down to the inverter/charger and sizing it correctly with the right inputs and outputs. I'm sure one of the experts here in the forum could provide pointers to recommended components.

On second thought, I guess having the ability to charge three ways (solar, grid, generator) would be pretty handy. Maybe some sort of automatic transfer switch? Will has a video about that, too:

 

[PSPS]

Thanks for the response and question

My thought was in a 3 day grid shut down I would run out of battery because I do not have solar. I do have a small generator which I think could charge the system in a few hours (4-5). If it all works (my math) I would only run the generator once a day or maybe even every other day to keep the batteries charged. This is also a once or twice a year event so I did not want to over invest.

If I'm missing something please let me know as I'm new to this as well.

Thanks

 

[svetz]

Has anyone built a home battery back up system with out solar to charge the batteries

The Peak Jump Start, you might also be interested in Solar Generator and Micro Systems

 

[johnzilla]

Thanks for the response and question

My thought was in a 3 day grid shut down I would run out of battery because I do not have solar. I do have a small generator which I think could charge the system in a few hours (4-5). If it all works (my math) I would only run the generator once a day or maybe even every other day to keep the batteries charged. This is also a once or twice a year event so I did not want to over invest.

If I'm missing something please let me know as I'm new to this as well.

Thanks

Right, but when do you know about a grid shut down? Sure, PG&E might send you a notification, but what if it was sudden? Storm, wildfire, etc. Wouldn't having your battery pack charged up just-in-case be the way to go in that situation? That would mean charging your pack every day with the generator, just-in-case. Or at least making sure it was charged up and ready.

For example, our power went out this morning for about 4 minutes. If we had a battery pack charged up and ready to go, with an automatic transfer switch, then we wouldn't have even noticed. IT guys like me call that "uninterruptible power supply". Our datacenters have both a generator and a battery bank, with the battery bank charging off the grid when all things are OK. The generator is only used if the outage goes longer than the battery bank can support. Then the generator does both...it charges the battery bank as well as running necessary systems.

I'm picturing a battery bank that is charged off the grid at grid costs, with the ability to charge off the generator should it be needed. Depending on how you size your battery bank, you might go an entire outage in your area without ever needing to fire up the generator at all.

 

[morth]

I'm running a test right now that matches your scenario. Just battery/Inverter to run a 17 Cubic foot top freezer fridge, a laptop, and charge phones/tablets/18650 cells for flashlights. I have 200 watts of solar, a generator, or grid that can be used to charge the battery. I figure having multiple charging options is a good thing in a Stand-by/emergency type of setup. Been running 16 hours so far and used about 73 AH with no charging. Using a 2000 watt inverter, the inverter fans never come on. Plus, I can run the microwave if I need to. The battery (old Valence U27-12XP, 132Ah LiFePO4) is getting close to 12 volts at this point but I know I can certainly get through the night. Then I have a choice of charging methods based on conditions. The solar panels can put out about 60 AH total on a good day, so I can just about fully recharge in 1 day. If I had the panels charging during the day, I think I could keep things running indefinitely especially with a healthier battery. On cloudy days, I would use the RV 60 amp charger with grid or generator for an hour or 2 and get the battery charged back up. I really don't like having 10-20 gallons of gas sitting around in cans, especially if there was a fire threat, but if that's all you have, you use it. Unfortunately, to make it through the night and to the next generator run period, you have to buy more of the most expensive components, batteries or run the generator more. There's a trade off, you can buy a lot of gas for the cost of a battery pack that can go 18 - 20 hours, but it's sure nice not to have all the noise and worry about someone stealing the generator.

Based on our longer outages in the past, the fridge will keep stuff cold for 2 - 3 days if you are careful (yes, you eat the ice cream first). Being able to run the fridge even for a few hours a day would help extend that and leave plenty of battery power for lights and modem. You could consider running the fridge hooked up to the generator while charging the battery, then you end up with a fully charged battery and a fridge that's been running for a couple hours. There's all sorts of combinations available.

 

[gnubie]

There are good all-in-one inverter chargers out there. Add battery and you have a UPS of what ever rating you want.

These don't show up all that much in terms of youtube videos but they seem to be the Real Deal and can run at their full rating. They don't have a lot of bells and whistles and are only for use as a single unit. The AC input could be supplied by the generator if there is a need to charge the battery. Very few negative comments about them. Various models and configurations are available for use across the world.

If I had the money to burn I'd get one just to take apart and see how they look on the inside, and maybe to use too

They aren't the only ones, Victron make a line of similar items too but are fairly expensive but include a lot of features such as running in parallel, and being able to produce 3 phase power with two additional slaves etc. There are quite a few good manufacturers of this type of thing, but a hell of a lot of crap ones.

 

[WoodsieLord]

I agree with Johnzilla.

To add something to the discussion, before jumping to the UPS solution, you should measure your power consumption pretty well.
Then, if said power requirement is somewhere below 2000w you may start hunting ebay/amazon for a good used UPS with dead batteries.

A few things to take into consideration:
- There are basically two types of UPS. Interactive and Online. Interactives have a relay somewhere inside, that when mains power goes out, it switches to an inverter drawing power from the battery bank relatively fast so you (computers) won't notice.
Online UPSs are *almost* what you can expect from an off grid solar system: A power supply (big enough to charge batteries AND the load) that goes both to the battery charger and the pure synewave inverter. The inverter works 24/7. The only thing that changes when the mains goes down is that the charger stops providing DC current and the batteries start to drain.
- To maximize efficiency of the inverters (online models mostly) the DC voltage trends to scale up with the unit capacity. This means that the smaller UPS usually use 12V, and they start to grow up (24V, 48V, 96V ... 240V) as the system capacity grows.
- I really like the Liebert Emerson (now they're "vertiv") GXT series. I have a 2kva model that works with 48V. This means that my battery bank consists of 4 12v batteries in series. The 3kva model works at 96V and the 6kva model that we have at work uses 20 batteries in series!. Inverter has a ~98% efficiency, but replacing batteries would be a nightmare for home usage!
- Last but not least, regarding your generator: When the MAINS goes online after an outage, the DC power supply is providing power to the load AND some extra juice to recharge the batteries. Usually, this recharge capacity is up to a 25% of the output rating. But I would recommend to make it a 50%. So if you get a 2kva UPS (assuming this fits your needs), your generator should be able to supply 3kva.

My calculations are very vague and I would definitely wait for a second opinion if I were in your circumstances!
The reason I mentioned all this is because I work in IT and as far as I'm aware, great brands of used UPS with dead batteries can go for really cheap, taking into consideration that the inverters are very good quality (AFAIK).

I hope this helps!!

 

[johnzilla]

- I really like the Liebert Emerson (now they're "vertiv") GXT series. I have a 2kva model that works with 48V. This means that my battery bank consists of 4 12v batteries in series. The 3kva model works at 96V and the 6kva model that we have at work uses 20 batteries in series!. Inverter has a ~98% efficiency, but replacing batteries would be a nightmare for home usage!

Lieberts are exactly what I was thinking of...ours were the size of commercial refrigerators. Our generators only ran if the power outage was longer than the Lieberts could support on their own. The other aspect of the UPS is line conditioning, though I guess that is what the BMS and inverters do in the DIY context?

I'm glad I joined the forum, I had not even thought of buying a "dead" UPS just for the circuits and boards. I was thinking I had to figure out how to build all of that. Cool tip!

 

[Supervstech]

Right, but when do you know about a grid shut down? Sure, PG&E might send you a notification, but what if it was sudden? Storm, wildfire, etc. Wouldn't having your battery pack charged up just-in-case be the way to go in that situation? That would mean charging your pack every day with the generator, just-in-case. Or at least making sure it was charged up and ready.

For example, our power went out this morning for about 4 minutes. If we had a battery pack charged up and ready to go, with an automatic transfer switch, then we wouldn't have even noticed. IT guys like me call that "uninterruptible power supply". Our datacenters have both a generator and a battery bank, with the battery bank charging off the grid when all things are OK. The generator is only used if the outage goes longer than the battery bank can support. Then the generator does both...it charges the battery bank as well as running necessary systems.

I'm picturing a battery bank that is charged off the grid at grid costs, with the ability to charge off the generator should it be needed. Depending on how you size your battery bank, you might go an entire outage in your area without ever needing to fire up the generator at all.

I think he would grid tie the charger to keep his bank charged, but would need to generator charge it when the grid goes down extended times.
Having the charger tied to the grid allows load sharing to cut down high demand energy prices also.

 

[offgriddle]

Cool idea, get a decent quality charger with parameters that you can set specific to the type of batteries you are using to assure proper charging and maintenance, (float), charging.

 

[PSPS]

Great discussion points, thank you.

I would want to keep the batteries charged up from the grid so when power goes out I have back up power ready. I only plan on using around 3500 watts per day with a max draw of the refrigerator cycling on at something like 900 watts for a few minutes then down to 105 watts, other wise I have it calculated at approximately 500 watts per hour (average). So my big questions are 12 or 24 volt system, and how big of a battery bank so I do not have to keep charging from the generator. I'm hoping to get around 20 hours of use before I need to charge. Of course I can scale back my consumption if it comes down to it.

Possible parts:
Victron inverter/charger (MultiPlus C)?
Batteries (Battle Borne 100 ah) X ?? or Tesla Model S single battery?
Transfer switch to connect to house

Thanks

 

[EclecticBadger]

Will's video on an automatic transfer switch ... many thanks johnzilla for the post because I must have missed this video and a product which can grid charge dependent on battery voltage status to top-off the solar, is just the thing I've been looking for.

 

[welnat]

power a full size refrigerator, a few lights and modem overnight
Thanks

I think it would be less complicated to run these loads on a few extension cords. I am currently looking at building a LiPo4 grid charged battery back up for my basement sump pump.

 

[welnat]

These don't show up all that much in terms of youtube videos but they seem to be the Real Deal and can run at their full rating.

These look fantastic, I wish they had a 240v ac 48v model.

However it was not clear on charging type for battery, I pulled the following from new egg listing ($700 free shipping to usa)

Battery Charge: 3-step intelligent battery charging, float and constant charge mode, 7 battery type selector, battery charger built in, 8 Battery types: Gel U.S.A, AGM1, AGM2, Sealed lead acid, Gel Euro, Open Lead Acid, Calcium, De-Sulphatio. Battery is not included.

 

[gnubie]

So long as it doesn't go into equalisation territory they should charge a suitably spec'd lithium battery. The one I linked actually is a 240v 48v model. Do you mean a split phase USA style dual 110v output?

When I first came across them looking for my first inverter their white box on wheels reminded me of Liebert's smaller units the company I worked for used to sell to hold up equipment racks. Smaller being relative. The things weighed 150kg. They were our first step into PWM driven transformers, transitioning away from chunky Exide linear designs.

 

[PSPS]

After doing some more research, and watching a few more videos from Will..

Can this be built were it is charged from AC power to maintain the battery using one of these?

I know I can buy a Goal Zero or Kodiak etc. off the shelf unit, but a DIY seams better both in performance and cost.
Any input is appreciated.

Thanks

 

[PSPS]

All,

Any input would be great, this is what I'm planning on building.

24 volt 5.3kWh emergency battery backup
Battery - Used Model S
Inverter - MPP Solar inverter/charger - PIP-LV2424MSD 2400W -14kW 24V 120VAC Charge 80A MPPT Solar, 60A Utility
Solar - none at this time
Generator - Honda 2000 (already own)

 

[welnat]

Do you mean a split phase USA style dual 110v output?

Yes exactly and run the whole building on it. The only thing better would be a true online version!