Constant AC charge possible through LV6548?

[TinyHouseSolar]

I’m trying to configure my LV6548 for a use case that I’m not finding the correct settings for.

I have an MPPsolar Lv6548 that is connected to two BigBattery Hawk 170ah 24v batteries in series. About 1500watts of panels on PV1. AC input is a circuit that has a long run and thus voltage drop is an issue. As such, I have limited the AC charge current to 2A in the 6548 menu.

However, here is the issue: The 6548 powers loads that often exceed the AC input’s current rating. This is not a problem when the batteries are charged but if I end up running a deficit such as in the winter, I need the batteries to stay somewhat charged by the circuit without going into bypass mode when the batteries get below the back to grid threshold. In other words, I need the ac input to slowly trickle charge the batteries at a low current at all times. If the batteries start getting full from solar or ac input, it can back off the ac input but otherwise I’d like it to be maintaining the batteries somewhere between 40-70% all the time.

Right now if I’m running a deficit and the batteries slowly drain down to their back to grid level, it switches to bypass mode and charges the batteries at the aforementioned 2A but also runs the rest of the load from the ac input as well, which can sometimes exceed 20A, totally running beyond the circuit’s capability. The big batteries have the amperage rating far exceeding my max surge load and together with a 2A trickle charge, I can maintain much greater than a 1.0 total input/output kWh ratio, but I don’t see how to set up the 6548 to do this. Here are my settings. I’ve included everything that seemed pertinent.

Output source priority: solar, battery, utility

Ac input range: appliance

Output voltage: 120v

Output frequency: 60hz

Single machine output

Battery type: user

Battery cut off voltage: 46v

Bulk charging voltage: 58v

Float charging voltage: 58v

Max charging current: 60A

Max battery discharge current: disable

Max ac charging current: 2A

Charging source priority: solar + utility

Back to grid voltage: 48v

Back to discharge voltage: 51v

Bypass function: disable



Thanks in advance for any advice.

 

[Bud Martin]

OP: "AC input is a circuit that has a long run and thus voltage drop is an issue. As such, I have limited the AC charge current to 2A in the 6548 menu."
The battery charging of only 2Adc @48vdc is only about 98W of power, that means the AC current draw from the utility is less than 1 A @120VAC.
How long is the AC wire from utility to the SCC? 1A of AC current should not cause much of the Voltage drops on the wires at all if you are using proper wire gauge for the AC.

 

[TinyHouseSolar]

OP: "AC input is a circuit that has a long run and thus voltage drop is an issue. As such, I have limited the AC charge current to 2A in the 6548 menu."
The battery charging of only 2Adc @48vdc is only about 98W of power, that means the AC current draw from the utility is less than 1 A @120VAC.
How long is the AC wire from utility to the SCC? 1A of AC current should not cause much of the Voltage drops on the wires at all if you are using proper wire gauge for the AC.

Gotcha, I thought the AC input current limit was based on 120v. If it is actually at 48v then sure I can set the utility current higher but I’m still curious if there is a way to set up the system as described above.

 

[Bud Martin]

The charging current (AC or Solar) are referring to the battery charging current.
I can only give you the reply about the charging current since I do not fully understand the setup you are trying to do, but seems like you just setup the utility charging at higher rate to keep the batteries charged.

 

[Lt.Dan]

I had the exact same question as you, and a few others. See my thread here:

MPP LV6548 Feature... Requests?

Hey guys, I've had my 2x LV6548's for a while now in my trailer, and I have some issues with it that I believe could be solved with a firmware update. The reason I'm posting here is I dont know if its possible and is limited in hardware capability, or if its just software. Now, I've been to a...

diysolarforum.com

Unfortunately I never go to the bottom of it

 

[TinyHouseSolar]

seems like you just setup the utility charging at higher rate to keep the batteries charged.

The problem with this is that when utility charging, the batteries are no longer the source of power for the inverter. So if you have a very small ac input source like a 15amps @ 120v and your system may occasionally draw 30 amps for a short time, it doesn’t matter what you set your ac current limit to because the total system draw will far exceed the available current, not to mention exceeding the available current after subtracting charging current.

 

[TinyHouseSolar]

I had the exact same question as you, and a few others. See my thread here:

MPP LV6548 Feature... Requests?

Hey guys, I've had my 2x LV6548's for a while now in my trailer, and I have some issues with it that I believe could be solved with a firmware update. The reason I'm posting here is I dont know if its possible and is limited in hardware capability, or if its just software. Now, I've been to a...

diysolarforum.com

Unfortunately I never go to the bottom of it

Did you ever attempt to install a separate 48v charger in parallel with the 6548 as a sort of trickle solution?

 

[Lt.Dan]

Did you ever attempt to install a separate 48v charger in parallel with the 6548 as a sort of trickle solution?

I did, but not a trickle, I bought a 25a charger that I plug in when I go to RV parks or run my generator. I made a post on my build thread. I'll find it...

EDIT: Not in my build thread actually, but Here it is

 

[TinyHouseSolar]

I did, but not a trickle, I bought a 25a charger that I plug in when I go to RV parks or run my generator. I made a post on my build thread. I'll find it...

EDIT: Not in my build thread actually, but Here it is

Awesome. I’m looking at the EC4. Is there anything special you need to keep in mind when connecting a charger in parallel with what is essentially another charger (LV6548)? Can the positive and negative leads from all three components (ec4, 6548, battery) all join at shared bus bars? Does the incoming current from the external charger confuse the 6548’s charge rate profile? Appreciate the help!

 

[Lt.Dan]

Awesome. I’m looking at the EC4. Is there anything special you need to keep in mind when connecting a charger in parallel with what is essentially another charger (LV6548)? Can the positive and negative leads from all three components (ec4, 6548, battery) all join at shared bus bars? Does the incoming current from the external charger confuse the 6548’s charge rate profile? Appreciate the help!

No worries, it all works together with no issues. Neither component knows about the other. They can all be hooked to a common bus bar