Seeking an elegant solution to charge one system from another

[Watts Happening]

I’ve got a 1.6kw array on my contractor trailer that spends most of its time parked, very little consumption. It’s not much but generally produces about 10kWh/day in the summer, I’d rather use it than lose it.

I’ve got a Sol-Ark 15k in the house. What’s the most elegant solution to use excess power from outside, inside? This should apply to the EG4 18Kpv as well as any other modern all in one system I’d expect.

Trailer consists of a 150/35 charge controller and single Multiplus-II 48/3000. Initially I thought I could use the AC output as an input to the Sol-Ark and act like it was AC coupling, the problem is I’m only outputting 120v and these inverters want a 120/240 configuration to accept the power.

My current setup is AC output via extension cord through a Kasa smart switch running on a customizable schedule then plugged into an EG4 Chargeverter. This setup works fine, but the inefficiency annoys me, too many DC-AC-DC-AC conversions.

I also considered some form of A/B switch for the panels and connect them to the input of the Sol-Ark but they don’t produce enough voltage so that’s out (and if I configured them 4s they would create too much voltage for the Victron 150/35).

I *think* I’m doing the best I can given the equipment, but I wonder if anyone has any brilliant ideas.

Also, I really like the Chargeverter but damn it would be nice if it had a way to remotely trigger it via a NONC contact that EG4, Victron and Sol-Ark (and I’m sure others) all have. Then the inverter could call on the chargeverter to turn on and off based on logic like SOC, that’d be icing on the cake.

 

[Rocketman]

On the chargeverter (I don’t know because I don’t own one), on power up will it automatically start charging?

If so use your Victron system to on open/close a relay 48v relay coil

Something like:
JAMCHE JQX-62F-2Z 2NO 2NC 120A / 80A AC 250V DC28V DC12V/24V/36V/48V/110V/220V AC 110V/220V/380V Coil High Power Relay (Color : 80A, Size : DC 48V) https://a.co/d/4VMdSDy

(At least I think I picked the correct one).

Good Luck

 

[Watts Happening]

On the chargeverter (I don’t know because I don’t own one), on power up will it automatically start charging?

If so use your Victron system to on open/close a relay 48v relay coil

Something like:
JAMCHE JQX-62F-2Z 2NO 2NC 120A / 80A AC 250V DC28V DC12V/24V/36V/48V/110V/220V AC 110V/220V/380V Coil High Power Relay (Color : 80A, Size : DC 48V) https://a.co/d/4VMdSDy

(At least I think I picked the correct one).

Good Luck

Yes the chargeverter does power up immediately. Your idea is essentially the same as my “smart plug”, it may give a bit more granular control which could be nice for turning off power export based on trailer SOC and things like that, but I’m still stuck with the many ac/dc conversions. I was hoping to eliminate any possible conversions, but I don’t know that I can.

 

[DIYrich]

Victron Orion-tr 48/48. Design a circuit to turn on the Orion-tr when battery voltage is above 54.4v. The Orion-tr can then send 54v, or whatever, to the sol-ark battery.

Or, maybe you can just connect the batteries together.

 

[Watts Happening]

Victron Orion-tr 48/48. Design a circuit to turn on the Orion-tr when battery voltage is above 54.4v. The Orion-tr can then send 54v, or whatever, to the sol-ark battery.

Or, maybe you can just connect the batteries together.

I like that idea aside from distance, I’d be running a 50 foot battery cable

 

[cs1234]

I like that idea aside from distance, I’d be running a 50 foot battery cable

Get some some good cable and keep those amps low.

I don't think Victron has a 48v/48v dc charger, they only have converters, so it's just a "dumb" converter with a set voltage output that won't account for remote battery state of charge.

Fortunately, the Victron DC/DC converters can boost the output voltage up to help cover the losses. Just set it to boost the voltage up high enough to cover the losses, and to work as a sort of "float" voltage.. then you'll at least get some benefit from your batteries on the trailer. If the float voltage you set is low enough, you won't even drain the batteries on your trailer all the way, they will just kick in to help the main batteries when needed.

 

[jameshowison]

Perhaps some useful ideas here:

Thread 'Minimal system to charge 48v battery from 48v battery?'
https://diysolarforum.com/threads/minimal-system-to-charge-48v-battery-from-48v-battery.65136/

Maybe the idea of a buck boost into an MPPT could give you the voltage needed to kick off the MPPT and then you have a configurable charger. Still 48v on a long run, though, so compare cable losses vs AC/DC conversion losses, I guess.

 

[cs1234]

Still 48v on a long run, though, so compare cable losses vs AC/DC conversion losses, I guess.

I'm sure somebody that likes math could try to figure it out.

 

[Watts Happening]

I'm sure somebody that likes math could try to figure it out.

At that point I’m throwing good money away. I can spend $0 and do exactly what I’m doing.

It’s probably me just being a nerd that allows it to bother me

 

[Mattb4]

You could just bring in the PV from your trailer to a separate SCC in your home. A couple of DC breakers to act for switching. A plug in cord to indoors and the SCC feeds the house battery bank.

 

[Rocketman]

New idea on Multiplus exporting AC power to chargeverter…

Instead of buying a relay timer or your “smart plug”, use your Victron Multiplus to turn on and off the AC2 circuit when the battery is full and lower. It looks easy to use Assistants to do that, then the only cost is for the electrical plug &wire on your trailer that’s connected to AC2.

The Multiplus program stays active all the time (when camping with the trailer you could use the plug too for something else-don’t know what. But when you get home just plug the extension cord that connects to the Chargeverter and your done.

You could setup on and off at any chosen levels…
On at 100% (to give batteries time to balance) - off at 60%. Although the solar will be reduced due to absorption mode.

Or on at 90% off at 25% using your batteries capacity. (But no balancing).

Or short cycles - on at 95% off at 90%.

 

[cs1234]

At that point I’m throwing good money away. I can spend $0 and do exactly what I’m doing.

It’s probably me just being a nerd that allows it to bother me

Yes, just accept the DC/AC/DC/AC or whatever losses you have going on and don't worry about it. Unless you are down to needing every watt for emergency or something, it's not worth worrying about.

 

[DIYrich]

Get some some good cable and keep those amps low.

I don't think Victron has a 48v/48v dc charger, they only have converters, so it's just a "dumb" converter with a set voltage output that won't account for remote battery state of charge.

The Orion-TR Smart is a charger, but they only go up to 24v. Since you are "moving" power, and not trying to really "charge" the battery, a fixed voltage at float voltage should do the trick.

 

[cs1234]

The Orion-TR Smart is a charger, but they only go up to 24v. Since you are "moving" power, and not trying to really "charge" the battery, a fixed voltage at float voltage should do the trick.

Yeah, the smart chargers are nice. Unfortunately, as you said, they don't have a 48/48 smart charger. The smarts can pair up with their smart battery sense so it can automatically handle the voltage drop over whatever your cable run is. They can also be configured to have a cut off voltage so you leave some charge in your source batteries.. etc..

For his purposes, a fixed voltage converter would work, but.. He should just stick with his current ac charger setup though, the efficiency losses can't be that bad compared to the cost of adding more equipment just to save a few watts.

 

[1201]

Yes, just accept the DC/AC/DC/AC or whatever losses you have going on and don't worry about it. Unless you are down to needing every watt for emergency or something, it's not worth worrying about.

i agree but would be curious how bad the losses are

 

[pollenface]

My 12v system tops up my 48v system through the night using a 1200w boost converter. The circuit is activated by the streetlight function of an mppt.

 

[Watts Happening]

New idea on Multiplus exporting AC power to chargeverter…

Instead of buying a relay timer or your “smart plug”, use your Victron Multiplus to turn on and off the AC2 circuit when the battery is full and lower. It looks easy to use Assistants to do that, then the only cost is for the electrical plug &wire on your trailer that’s connected to AC2.

The Multiplus program stays active all the time (when camping with the trailer you could use the plug too for something else-don’t know what. But when you get home just plug the extension cord that connects to the Chargeverter and your done.

You could setup on and off at any chosen levels…
On at 100% (to give batteries time to balance) - off at 60%. Although the solar will be reduced due to absorption mode.

Or on at 90% off at 25% using your batteries capacity. (But no balancing).

Or short cycles - on at 95% off at 90%.

Thus far I think this is certainly the smartest option, I don't think I'll really have any extra cost in doing it (have plenty of stuff laying around to accomplish it).

That at least gives me a way to allow the Multiplus to have some form of control. Currently I just have the smart plug set to turn on at 10am and off at 6pm, then the chargeverter is set to pull ~850 watts during the entire time.

Your plan at least puts the Multiplus in control and if for some reason the batteries are draining due to it being cloudy and reach whatever SOC I set, it can disconnect the output. That idea works well! Thank you!

 

[DIYrich]

Another option is to put an auto transformer at the sol-ark to convert the 120 to 240.

 

[timselectric]

I would just stick with the Chargeverter.
It's the simplest option.
I use one for my only connection to the grid.
If my battery voltage ever gets down to 48v. The dry contacts turn on a relay that powers the Chargeverter from the grid. The Chargeverter is set to keep the battery at 48v, until the sun takes over the next morning. Once the battery voltage reaches 50v , the dry contacts switches it back off.
You can use the relay on the other end. To turn it on when you have a full charge. And excess production.