Preparing for Blackouts: Looking for Fast and Cheap Charging Solutions for LFP Batteries

[D-Bond]

Hello everyone,

I'm gearing up for potential winter blackouts and I'm looking for advice on how to quickly charge large LFP (Lithium Iron Phosphate) batteries during limited electricity availability. There's a chance we might only have electricity for 2 hours per day, so I need to maximize charging during that window.

My Setups:

• (P1) 48V LFP (16*EVE280Ah) battery attached to a 5kW solar hybrid inverter (max 80A or 60A AC charge input).
• (P2) Two 24V LFP (8*EVE280Ah, 8*EVE305Ah)
• batteries, each attached to a 2.4kW solar hybrid inverter (max 60A or 40A AC charge input). (these two are going to my friends)

All batteries are equipped with JK inverter BMS and are connected to the inverters via DATA cables. Under normal conditions, the inverters charge the batteries slowly. However, in an emergency, I want to manually switch to a fast-charging mode to fully charge the batteries within 2-3 hours. My residential power limit (the P1 setup) is 9kWt, but I also have Honda EU22i generator that is fully capable to cover my hour power needs plus charge the battery.

Possible Solutions I'm Considering:
Solution 1: High-Voltage DC Power Supply via MPPT Input
Use a high-voltage (HV) isolated DC power supply capable of delivering ~140V+ DC or higher to provide power through the MPPT (Maximum Power Point Tracking) input of the inverter.

• Pros:
  • Utilizes existing inverter infrastructure.
  • Potentially high efficiency due to MPPT optimization.
• Cons:
  • Requires a reliable and safe HV DC power supply.
  • Safety concerns with feeding power into the MPPT input not originally designed for grid charging.

Solution 2: High-Amp Low-Voltage DC Power Supply Direct to Batteries
Use a high-current, low-voltage DC power supply to charge the batteries directly, in parallel with the inverter. The DC power supply voltage would be set to the battery's bulk charge voltage. As the battery approaches 90% SOC, the power supply's output naturally tapers off, and the inverter handles the rest of the charging process.

Solution 3: High-Voltage DC Power Supply with External MPPT Charge Controllers
Use a high-voltage (75V to 110V DC or higher) isolated power supply in conjunction with external MPPT charge controllers (e.g., Victron SmartSolar MPPT 100V Charge Controller) connected directly to the batteries. This setup is separate from the inverter's high-voltage power rails.

My concerns are:

• (q1) Which of these solutions is the most realistic and safe for quickly charging my LFP batteries?
• (q2) Are there better or more efficient methods to achieve fast charging within a limited time frame?
• (q3) What are the potential risks or challenges associated with each solution, and how can they be mitigated?
• (q4) Has anyone implemented a similar setup? I'd appreciate hearing about your experiences and any lessons learned.

I'm open to any advice, suggestions, or recommendations you might have. My main goal is to ensure that the batteries can be safely and efficiently charged during short periods of grid availability.

Thank you in advance for your help!

 

[TM48]

Most here will recommend a EG4 Chargeverter. It can input 120/240 ac and output 48v at up to 100 amps. Adjustable for output voltage and current. Available from Signature Solar or Current Connected. About $465. It can be used with grid or generator power.

 

[Brucey]

Really only downside of the chargeverter is very loud cooling fan, especially if used in conjunction with a quiet generator like a Honda eu2200. But if it's just rare occasions where it's needed may not be an issue.

 

[AntronX]

How many amp hours is your 48v battery? Get second hybrid inverter to use as additional charger and as backup inverter. Must, PowMr and Daxtromn inverters (popular in Ukraine) have a lot of factory defects so having a backup would be smart.

 

[42OhmsPA]

https://www.aliexpress.us/item/3256803568992210.html

I'd go with the 57V version for a 16S pack. You can reprogram them fairly easily.

4

Thread 'DIY 'Chargenectifier''

Mar 6, 2023

Based of the informative info recently posted by @ChrisFullPower in another thread I'm intrigued in DIY'ing a charger from used rectifiers.
A quick search on eBay for '48v rectifier' has made me realize it's definitely doable at costs much lower than off the shelf options...

I'll start with a few examples of what I've found.

I'm assuming one would need to figure out a way to adjust the voltage, unless you can find something pre-programmed.

(I apologize for the terrible links, I'm using the ebay app to share the item and copy the link.)
These look promising because you could...

• 42OhmsPA
• Replies: 875
• Forum: Danger Zone! (Advanced User Experiments Only)

• 
• 

 

[Sonne]

Parallel connect multiple chargers to add charging amps, but be aware of the limits of your battery and BMS and stay within them. Normally 0.5C, but you haven’t told us the capacity of your battery, just that it’s a 48V one.

Multiple lower rated chargers are likely cheaper than one huge highly rated one.

 

[D-Bond]

How many amp hours is your 48v battery? Get second hybrid inverter to use as additional charger and as backup inverter. Must, PowMr and Daxtromn inverters (popular in Ukraine) have a lot of factory defects so having a backup would be smart.

I apologize for not mentioning earlier that the battery capacities are 280Ah for the 48V system and 280Ah & 305Ah for the 24V systems. Basically, to achieve a charging rate of about 0.5C, I need an additional 60-80A for each setup.

I've thought about adding an additional inverter to serve as a charger or replacing some of my current inverters with models like Deye or Victron. Thank you for the information you shared!

 

[wpns]

Hello everyone,

I'm gearing up for potential winter blackouts and I'm looking for advice on how to quickly charge large LFP (Lithium Iron Phosphate) batteries during limited electricity availability. There's a chance we might only have electricity for 2 hours per day, so I need to maximize charging during that window.

My Setups:

• (P1) 48V LFP (16*EVE280Ah) battery attached to a 5kW solar hybrid inverter (max 80A or 60A AC charge input).
• (P2) Two 24V LFP (8*EVE280Ah, 8*EVE305Ah)
• batteries, each attached to a 2.4kW solar hybrid inverter (max 60A or 40A AC charge input). (these two are going to my friends)

All batteries are equipped with JK inverter BMS and are connected to the inverters via DATA cables. Under normal conditions, the inverters charge the batteries slowly. However, in an emergency, I want to manually switch to a fast-charging mode to fully charge the batteries within 2-3 hours. My residential power limit (the P1 setup) is 9kWt, but I also have Honda EU22i generator that is fully capable to cover my hour power needs plus charge the battery.

Unfortunately, the math doesn't add up. To charge the first battery (14 KWHR) in an hour, you'll need (first approximation) 14KW, and your 9KW residential power limit and 1.8KW generator just aren't going to be able to do that, even excluding your normal load. To get the 9KW out of a ChargeVerter you'll need two of them.

The second case is a little better, but you'll need (again, first approximation) 6-7KW, and that's more than one CV as well.

Longer runtimes on your 1.8KW generator will work, but you'll need a power survey to know the details, and running at peak output 24x7 may lead to <ahem> reduced lifespan of the generator.

Honestly your best bet might be to add solar panels, if you can.

 

[D-Bond]

Really only downside of the chargeverter is very loud cooling fan, especially if used in conjunction with a quiet generator like a Honda eu2200. But if it's just rare occasions where it's needed may not be an issue.

Well, I agree that all this equipment is quite loud, especially when the hybrid inverter is charging the battery. But it's better to have electricity and be able to continue working—I don't really care about the noise.

This is the amount of energy I've used from the battery since I built it (about one month ago). The previous setup was based on the Bluetti AC200MAX with a watt meter device in the output socket; the latest number I remember was over 70 kWh.

 

[ULR]

What's your elevation? Chargeverters are only rated for use up to 1500 meters (4921 feet) above sea level. Above that you risk being unable to meet code and also losing your site's fire insurance.

(Edit: Hmmm... I see you're in Kiev. At 149 m or thereabouts the elevation isn't an issue, and I suspect fire insurance and zoning laws aren't either. B-b Leaving the post up for others who might be setting up something similar elsewhere.)

 

[chrisski]

For those recommending Chargeverter, the OP is in Europe, so will this work there?

I only saw 240 volt split phase chargeverter and did not know they made a European version.

 

[wpns]

For those recommending Chargeverter, the OP is in Europe, so will this work there?

I only saw 240 volt split phase chargeverter and did not know they made a European version.

There is no split-phase CV, there's only one with an input range of 90-264VAC.

EG4® Chargeverter GC - EG4 Electronics

EG4 Chargeverter GC: easy battery charging in bad weather, generator compatibility, and adjustable current/voltage.

eg4electronics.com

Note that the CV is 48V output only, so it doesn't help the OP with his 24V batteries. There's probably a solution in the ChargeNectifier thread. though you'd have to source 24V nominal supplies, which aren't as COTS as 48V telecom supplies.

4

Thread 'DIY 'Chargenectifier''

Mar 6, 2023

Based of the informative info recently posted by @ChrisFullPower in another thread I'm intrigued in DIY'ing a charger from used rectifiers.
A quick search on eBay for '48v rectifier' has made me realize it's definitely doable at costs much lower than off the shelf options...

I'll start with a few examples of what I've found.

I'm assuming one would need to figure out a way to adjust the voltage, unless you can find something pre-programmed.

(I apologize for the terrible links, I'm using the ebay app to share the item and copy the link.)
These look promising because you could...

• 42OhmsPA
• Replies: 875
• Forum: Danger Zone! (Advanced User Experiments Only)

• 
• 

 

[ULR]

For those recommending Chargeverter, the OP is in Europe, so will this work there?

I only saw 240 volt split phase chargeverter and did not know they made a European version.

It's all one model for US, Europe, Hot/neutral, Hot/Hot, 120/208/240 V

AC Input: 90-264VAC, 50-60Hz.

Does not require a neutral, just L1, L2 and ground. (L2 is fed from neutral for line/neutral feeds such as 120V half of split phase.)

 

[hsync33]

Most hybrid chinese solar inverters in the 3-7KW range would probably do what you need. They are relativelly well built, only drawback is relativelly load fans and high quiescent current, none of them should be a problem if you plan to use it solely as an 'add on' charger.

There's an example below I've seen on AliExpress that can charge at 120A.
I don't know why your models (at 80A) charge slowly. Do they not draw the full current, or by slowly you mean the 80A is a slow charger and you want to add aditional chargers to speed it up?

 

[BatteryBuff]

I apologize for not mentioning earlier that the battery capacities are 280Ah for the 48V system and 280Ah & 305Ah for the 24V systems. Basically, to achieve a charging rate of about 0.5C, I need an additional 60-80A for each setup.

I've thought about adding an additional inverter to serve as a charger or replacing some of my current inverters with models like Deye or Victron. Thank you for the information you shared!

I think that a C/2 charging system would require over 13kW of charging power. That sounds very large, specialized and expensive.
Maybe you could use the hybrid inverters' charging circuits which are slower but already purchased?