Energy storage solution for unstable grid | Ukraine

[dobegor]

Hi diysolarforum members!

I'm currently searching for a solution for my grandparents' house in Ukraine. Due to the recent damage to civilian infrastructure, the grid energy supply became wildly unstable. At best, the house in question gets 8 hours of grid energy per day.

The main problem is heating. The house is equipped with gas heating, but the heater and pump don't work without electricity.
I currently have an AmpereTime 100Ah LiFePO4 battery on hand that I intend to send them.

I'm looking for a cost-effective, simplest solution possible to safely operate a system that would charge from grid power when available and then use a pure sine inverter to power the heating equipment.

An off-the-shelf UPS designed for a regular lead-acid battery is unfortunately not an option, as, from what I've read here, a regular UPS doesn't know about LiFePO4-specific charging curve and it would result in a shorter battery life.

I thought about using this simple scheme involving a LiFePO4 charger (as I was told that it's not advised to use a regular 12V charger at all) and a pure sine inverter with its output wired to a transfer switch in parallel with a grid (see the picture).

I'd love some feedback as I'm pretty new to off-grid tech and electricity in general. My goal here is to build something cost-effective, using something that I already have (ampere time battery) and as fool-proof as possible - grandparents are not quite as tech-savvy.

 

[chrisski]

The plan is decent. Getting a decent design will require a power load to include peak wattage (if able), kWh total, and max sustained wattage. A 12 volt inverter will be limiting, but could power a little bit for a while.

 

[dobegor]

@chrisski

> a decent design will require a power load to include peak wattage (if able), kWh total, and max sustained wattage

Peak wattage is not expected to be higher than 800ish watts, kWh total capacity of the system is expected to be around 1.2 kWh (the nominal value of Amperetime battery that I currently have). Sustained wattage would be much, much lower, ranging from 60-80 watts (heating only) to 250 (heating, some lighting, emergency fridge).

> 12 volt inverter will be limiting
Yes but it looks like it'd be sufficient for quite some time given the current circumstances. The main concern is heating, and there's a gas heater for that. If gas infrastructure also gets damaged, the only reasonable outcome for them is to evacuate completely since it'd be impossible to do anything about that on your own.

My main concerns in the scheme I've drafted are:
1) Can I really have both the charger AND inverter on all the time? I mean, the BMS will stop charging the battery, so I'm not concerned about overcharging, but how would the charger->inverter chain behave in this case? I.e. is it ok, given that wattage constraints are met, feed the inverter through the charger? (I'm a noob, but that is what's gonna happen if the grid is there and nobody flicks the transfer switch).
2) Is a "regular" 12v charger really a no-go for a LiFePO4 battery in this case?

 

[1.21 Gigawatts]

something like this maybe?

https://www.aliexpress.com/item/1005004754486787.html?spm=a2g0o.detail.1000023.1.21593d79klEFAc

So this thing will try keep you running off battery, and switch to grid when battery low, but i think if you put gird as the inverter input, and your 12v inverter AC output to "public power" it will function the otherway, and run off grid, and if grid goes down, run off battery. and you keep your battery topped up with a grid connected charge controller.





older model bellow

 

[1.21 Gigawatts]

If you havent already brought all the other components (inverter, charger etc), Something like this hybrid inverter could be a neater all in one solution. Limited to 1500w thought because only 12v (24v model can do 3000w). Bonus they could also add some pannels in the future.

https://www.aliexpress.com/item/1005004059572107.html

 

[timselectric]

For simplicity for your parents.
An AIO is probably the easiest to set up.

 

[MurphyGuy]

Hi diysolarforum members!

I'm currently searching for a solution for my grandparents' house in Ukraine. Due to the recent damage to civilian infrastructure, the grid energy supply became wildly unstable. At best, the house in question gets 8 hours of grid energy per day.

The main problem is heating. The house is equipped with gas heating, but the heater and pump don't work without electricity.
I currently have an AmpereTime 100Ah LiFePO4 battery on hand that I intend to send them.

I'm looking for a cost-effective, simplest solution possible to safely operate a system that would charge from grid power when available and then use a pure sine inverter to power the heating equipment.

An off-the-shelf UPS designed for a regular lead-acid battery is unfortunately not an option, as, from what I've read here, a regular UPS doesn't know about LiFePO4-specific charging curve and it would result in a shorter battery life.

I thought about using this simple scheme involving a LiFePO4 charger (as I was told that it's not advised to use a regular 12V charger at all) and a pure sine inverter with its output wired to a transfer switch in parallel with a grid (see the picture).

I'd love some feedback as I'm pretty new to off-grid tech and electricity in general. My goal here is to build something cost-effective, using something that I already have (ampere time battery) and as fool-proof as possible - grandparents are not quite as tech-savvy.

My mother-in-law lives in Kiev and my wife has stopped sending her anything except money because it will likely not reach her before someone else steals it.

Sorry to say, but sending her anything of value you're not willing to lose is probably a very bad idea at the moment.

 

[dobegor]

My mother-in-law lives in Kiev and my wife has stopped sending her anything except money because it will likely not reach her before someone else steals it.

Sorry to say, but sending her anything of value you're not willing to lose is probably a very bad idea at the moment.

I've got a few reliable folks who do transport and they already did a run for me to send some Bluetti EB3As successfully. It's a risk of course, but there are always bad people and good people.

 

[dobegor]

If you havent already brought all the other components (inverter, charger etc), Something like this hybrid inverter could be a neater all in one solution. Limited to 1500w thought because only 12v (24v model can do 3000w). Bonus they could also add some pannels in the future.

https://www.aliexpress.com/item/1005004059572107.html

View attachment 124118

AIO solution sounds really easy to set up. Are there any reputable reviews of the device in question?

Also, the issue is I'm in Germany, so I'd prefer to order something inside the EU because of warranty and import fees concerns.

Also cost-wise, my drafted scheme sums up to:
1) 600W Pure sine inverter ~80EUR
2) 20A LiFePO4 charger ~80EUR
3) Transfer switch 20-50EUR

Which sums up to 220 EUR with no import fees and local warranties. AIO solution sounds easy to use but presents a single point of failure and no warranty since I cannot find a local distributor in Germany for this unit.

And from easy to use point of view my scheme seems to work just as simply, provided that leaving both the charger and inverter on 24/7 is safe. Though this is where I simply don't have enough knowledge to understand if it's OK to do this.

 

[timselectric]

And from easy to use point of view my scheme seems to work just as simply, provided that leaving both the charger and inverter on 24/7 is safe. Though this is where I simply don't have enough knowledge to understand if it's OK to do this.

As long as nothing gets over heated and the charger won't overcharge the battery, it's fine.

 

[dobegor]

the charger won't overcharge the battery

The BMS is there so it shouldn't happen.

But aren't LiFePO4 chargers very specific in terms of Voltage-Current graph? I.e. they sense how much current goes in and adjust the voltage to match that of a "good" charging profile specific for battery chemistry? That's just my (completely clueless) assumption that the inverter being the "sink" for a LiFePO4 charger would confuse the charger.

That is my main concern about this cheap DIY scheme of mine. Otherwise, I can just assemble the whole thing (just disconnect the battery) and ship it.

Also, I thought about just plugging in an MPPT controller. Since they are relatively cheap, readily available, and seem to "know" about the intricacies of LiFePO4 chemistry. Can I charge a battery through MPPT from grid->12v chain?

 

[timselectric]

If it's a LiFePo4 charger, it will do what it should.
Adding an MPPT charger will allow the ability to charge from solar. But, you can't connect it to the grid. (If that's what you are talking about)

 

[chrisski]

The one thing I don’t like about an all in one is the high idle draw matched with one or two lithium batteries. This could drain the batteries in as soon as a day or two with no loads depending on the item. Also, depending on the circumstance, could rack up an electric bill.

Could be served better with different components, like an MPPT, charger, and inverter. The inverter is the power hog for idle draw, and could be shut off when not needed when the grid id up and also can be shut down when not needed when the grid is not.

A regular charger is a no go. The charging voltage on a lithium battery is a max of 14.6
(should be less). Above that, damage to the cells happen, like swelling. (I don’t think this was answered).

 

[OzSolar]

If you're not doing solar and already have the battery then I would suggest an inverter/charger that has a transfer switch.

Something like this from Aims.

 

[timselectric]

Agree with Oz.
And you can easily add solar later, if desired.

 

[OzSolar]

My heart really goes out the people of Ukraine. There was another thread on this recently. Here it is. Maybe there's something there that can help.

 

[dobegor]

@chrisski @timselectric @OzSolar
Thank you for your kind words and advice.

The cheapeast locally obtainable All-in-One solution is Ecive CSI 5S: https://www.ective.de/ECTIVE-CSI-5-Sinus-Charger-Inverter-12V
Which combines the inverter and battery charger and claims to be able to do a quick switch automatically.

> The one thing I don’t like about an all in one is the high idle draw matched with one or two lithium batteries. This could drain the batteries in as soon as a day or two with no loads depending on the item.

However, this is a big concern for me. I think for this reason alone I'd settle with charger + inverter + manual transfer switch like this one: https://www.amazon.de/-/en/Heschen-SZW26-20-Universal-Positions-Terminals/dp/B097T3DXV8

Thank you all for your input!

 

[OzSolar]

The cheapest locally obtainable All-in-One solution is Ecive CSI 5S: https://www.ective.de/ECTIVE-CSI-5-Sinus-Charger-Inverter-12V
Which combines the inverter and battery charger and claims to be able to do a quick switch automatically.

While that inverter may be perfectly fine I'll offer that one needs to be careful small "off brand" inverters, particularly in regards to thier wattage ratings.

However one specific issue with that inverter is it's 10 amp charger. To be safe, I'd not count on it putting out much more 7 or 8 amps for hours at a time. The result of that is it may not be able to get the battery charged back up in time for the next power outage at your Grandparent's house.

 

[dobegor]

While that inverter may be perfectly fine I'll offer that one needs to be careful small "off brand" inverters, particularly in regards to thier wattage ratings.

However one specific issue with that inverter is it's 10 amp charger. To be safe, I'd not count on it putting out much more 7 or 8 amps for hours at a time. The result of that is it may not be able to get the battery charged back up in time for the next power outage at your Grandparent's house.

Thank you.
I've decided to "play it safe" and ordered a Renogy 1kw inverter with an automatic transfer switch:

https://www.amazon.de/gp/product/B09WN1R34F/

And a Victron Blue Smart 12V 17A charger:

Blue Smart IP67 Charger Waterproof - Victron Energy

The Blue Smart IP67 Waterproof Charger is the new professional battery charger with built-in bluetooth. Find a Victron Energy dealer near you.

www.victronenergy.com

I intend to leave the charger and inverter "always on" after configuring it.