24vdc & 83vdc coming in a single line to an MPPT (Ecoflow Delta Max)???

[farmhand]

So my 83vdc array feed runs into my Ecoflow Delta Max 2000. I want to put a 24v battery bank in the outhouse 200ah LifePO4 for overnight charging. I only have a single 2 conductor feed running into the Eco in the cabin....

So with blocking diodes could they just share the same line at the same time? What would the MPPT do with two different voltages?

I was thinking about a photocell to switch the line from the 83v array to the 24v batteries.... but then often our array is still pumping 70v when the clouds close the photocells on the barn lights..... so I would be wasting solar with a photocell controlled transfer switch in the outhouse......

Hmmmmmmmmm

Thoughts anyone?

 

[sunshine_eggo]

So my 83vdc array feed runs into my Ecoflow Delta Max 2000. I want to put a 24v battery bank in the outhouse 200ah LifePO4 for overnight charging. I only have a single 2 conductor feed running into the Eco in the cabin....

So with blocking diodes could they just share the same line at the same time?

Blocking diodes on the batteries would also prevent charging.

What would the MPPT do with two different voltages?

Nothing or completely shit itself.

I don't entirely understand what you're getting at. You talk about cabin and outhouse, and only having a single pair into the cabin.

 

[farmhand]

Blocking diodes on the batteries would also prevent charging.



Nothing or completely shit itself.

I don't entirely understand what you're getting at. You talk about cabin and outhouse, and only having a single pair into the cabin.

So from the 2400w array on the Coop, go to the outhouse on 2 sets of #12 THHN to the outhouse (where I plan to store cheap LifePO4's), then this continues on a single pair of #12 to the cabin where the Ecoflow is.

I plan to split the array, so 1200w comes into the charge controller in the outhouse, and the other 1200w continues on to the Ecoflow.

SOooooo.... How can I have these batteries in the outhouse charge the Ecoflow when the sky's dark? I can add an ATS in the outhouse, to switch the feed to the Ecoflow from the array to the batteries... but it'd be a lot easier if the 83v array feed & the battery 24v feed can both share the feed line to the Ecoflow at the same time.

 

[sunshine_eggo]

So from the 2400w array on the Coop, go to the outhouse on 2 sets of #12 THHN to the outhouse (where I plan to store cheap LifePO4's), then this continues on a single pair of #12 to the cabin where the Ecoflow is.

I plan to split the array, so 1200w comes into the charge controller in the outhouse, and the other 1200w continues on to the Ecoflow.

Okay. A little clearer now.

So there's an MPPT in the outhouse too?

2 pairs PV to outhouse, 1200W on each.
#1 pair connected to MPPT in outhouse charging 24V battery in outhouse.
#2 pair running to cabin, 1200W to Ecoflow's MPPT

What is the purpose of the battery in the outhouse?

SOooooo.... How can I have these batteries in the outhouse charge the Ecoflow when the sky's dark? I can add an ATS in the outhouse, to switch the feed to the Ecoflow from the array to the batteries... but it'd be a lot easier if the 83v array feed & the battery 24v feed can both share the feed line to the Ecoflow at the same time.

Okay, I think I get it. You want to switch the input of the ECO from the PV to the battery. It really made it sound like you were trying to connect two different voltage batteries together.

Assuming current only needs to flow from the outhouse to the cabin.

I think blocking diodes would work, but there could be some weirdness at dawn and dusk where the PV can produce voltage, but not current. The diodes need to be upstream of wherever you join the outputs. What's in my head:



I'd fuse between the diode and the source as well. Probably another fuse on the (+) to the Eco.

Another concern would be how the ECO handles input. An MPPT is a draw on a battery. They try to pull as much as the array can deliver. It may try to pull max current from the battery, which would exceed the wire rating.

 

[farmhand]

Okay. A little clearer now.

So there's an MPPT in the outhouse too?

2 pairs PV to outhouse, 1200W on each.
#1 pair connected to MPPT in outhouse charging 24V battery in outhouse.
#2 pair running to cabin, 1200W to Ecoflow's MPPT

What is the purpose of the battery in the outhouse?



Okay, I think I get it. You want to switch the input of the ECO from the PV to the battery. It really made it sound like you were trying to connect two different voltage batteries together.

Assuming current only needs to flow from the outhouse to the cabin.

I think blocking diodes would work, but there could be some weirdness at dawn and dusk where the PV can produce voltage, but not current. The diodes need to be upstream of wherever you join the outputs. What's in my head:

View attachment 145187

I'd fuse between the diode and the source as well. Probably another fuse on the (+) to the Eco.

Another concern would be how the ECO handles input. An MPPT is a draw on a battery. They try to pull as much as the array can deliver. It may try to pull max current from the battery, which would exceed the wire rating.

The batteries are for cost. 4000wh (two ECOFLOW Expansion batteries with run me $2500!!! But we love this Eco & it's been doing great. So the batteries in the outhouse are simply price, I can get 4000wh of cheapo LifePO4 off amazon for $650. I love this solar deal, but not wanting cheap batteries in the cabin, if the outhouse burnt down... meh....

Yes, you diagram & understanding is correct. We have a massive charge 2600w charge controller for the outhouse already, as we were going to run an inverter from there & not get an Ecoflow..... but then I wanted something the wife could grasp & understand (which she has very well).


here is a dumb video I made & put on here, the 2nd half shows the system. Of course to add these batteries & controller I would have to add a 2nd fused disconnect and revamp the combiner box... I don't know.... We need 6000wh to be running the way I figure it, and a top the cost the the 2 expansion batteries they are also ION (800 cycles). Something I didn't know enough about when I bought it.

 

[farmhand]

OK, think I have the final solution:
I am going to put the whole array power into the outhouse, using our bag-arse controller we have. This will be for a 24v battery bank. Then I will use a 1500w DC-DC converter to step up the 24v bank to 48v to get a full 800w charge input to the Eco's MPPT.

Then DC isn't sharing the same line, and no relays or switching needed. Plus I can add as many AH in the outhouse as I wish. The LifePO4's have low voltage cutoff.... so it should be that dang simple :D
https://www.ato.com/dc-dc-boost-converter-24v-to-48v

 

[farmhand]

UPDATE: So I ended up buying two of the 240ah cheapo 24v LifePO4's off amazon: Batteries off amazon
I will put them in the outhouse with this massive charge controller connected to the full 2400w array: OOYCYOO 100A controller

This bank, via output of the controller load will give a constant 192w to the Ecoflow Max's 24v car charger input. This constant charge should keep the Ecoflow alive, as our idle wattage is about 130w, even less when we sleep.
If it is not enough wattage to keep up, I can then get a booster to 48v and give the Ecoflow a constant 624w on it's solar input. Pictures to follow but the batteries take a week to get here.

 

[farmhand]

Note on the above update: This all puts me closer to putting a real inverter in the outhouse and powering 120v/240v directly to the cabin. Then dump the Ecoflow onto another project, like taking over the deep freezer in the pole building

 

[BradCagle]

Note on the above update: This all puts me closer to putting a real inverter in the outhouse and powering 120v/240v directly to the cabin. Then dump the Ecoflow onto another project, like taking over the deep freezer in the pole building

This ^^^ sounds way more logical