Going all in - 600ah @ 48v of battery + 4,000 watts of solar

[TacomaJoe]

Originally Posted by ependydad

Mind sharing a picture of what you've done? You're the second person I've read about changing the leads out on the bench charger.

I don't have any photos. I just crimped ring terminals on the wire ends that fit the cell stud and power supply posts. On the PS end, if you used spade terminals you wouldn't need to unscrew the post all the way.

[TitanMike]

Originally Posted by TacomaJoe

I don't have any photos. I just crimped ring terminals on the wire ends that fit the cell stud and power supply posts. On the PS end, if you used spade terminals you wouldn't need to unscrew the post all the way.

Based on the model number of Doug's charger it's only rated for 10 amp max. Wire size isn't really a limiting factor. Size of battery bank being charged and limited amount of charging current is.

Without a larger source of power it's just going to take time. If batteries are "dead" (0% SOC), by my calc's it will take about 3 weeks to charge 16 cells in parallel. Less time depends on SOC of cells when charge begins. Again, the posted voltage for each cell indicated an SOC somewhere over 90% so the time to fully charge will be a fraction of what it takes to charge a more deeply discharged battery.

The problem with using an Inverter/Charger is that cells then need to be connected in series (or series/parallel) and connected to their BMS in order to accept the higher voltage produced by the Inverter /Charger.

Charging as pictured in Doug's post will just take time -------- or a larger power supply.

[ependydad]

Originally Posted by TitanMike

BThe problem with using an Inverter/Charger is that cells then need to be connected in series (or series/parallel) and connected to their BMS in order to accept the higher voltage produced by the Inverter /Charger.

Charging as pictured in Doug's post will just take time -------- or a larger power supply.

That's pretty much my plan. Wire 16 up in series and then let the BMS cut-off charging when one hits 3.6v. Disassemble the pack, wire it back into parallel, and then top them up to 3.65v to top balance them all.

Repeat for the other set of 16.

And then just top balance the 2 spares in parallel together.

Am just waiting on some documentation from ContinuousResources.com for some guidance on all the bits and pieces before I place my first order with them. And then there's the matter of figuring out how to wire up the inverter so I can plug it into a household outlet.

[pgm1]

Very interesting project! I'm planning a similar project later this year albeit with only a third of your capacity, 24V / 600AH.

I've chosen to go with an All In One (Growatt SPF 3000TL) which provides solar charging, 120V AC charging (60A), a 3000W inverter and an automatic transfer switch. They make larger models for 48 volts DC input and 240V AC output.

I'll be installing 1820W of solar panels which will provide 75A of charging current under ideal circumstances. The RV's AC input will be wired directly to the AIO with the inverter's output going into the RV's AC panel.

The plan is to always operate off solar+battery and use the AC input to charge the batteries when needed if the solar isn't sufficient. In the event the batteries are completely discharged then the AC input can be switched in via the ATS.

I'm following your project with enthusiasm.

[ependydad]

Took the weekend off because we left from Thursday-Sunday to visit my in-laws. Boy did I miss my camper!

Anyway, the pair of Overkill Solar BMS came in while we were gone. Thank goodness we don't have issues with porch pirates around here (though, to that one bike pirate who stole my big in December, you can suck it).

Today I put 17 of the cells (1/2 of them) back on the charger for lack of a better option. I played around with voltage a bit- starting at 3.65, dropping to 3.6, and then back to 3.65 after some discussions with a friend. While it was at 3.6v, I started seeing the amps work their way lower which means that the pack was getting closer to topping off. I still have a ways to go but they'll get there.... eventually.

Meanwhile, I've been working with Continuous Resources to get a solar system design put together. They supposedly do a great job showing fuses, breakers, and wire sizes. But I've been waiting over a week with only a little communication from them. I'm fixing to go rogue here shortly...

[ependydad]

This past Wednesday, we got our first look at the RV! It was just delivered that day from the factory so there was a lot of little things the dealership needed to tidy up. We've scheduled our walk-through on April 12.

STILL bench charging 17 of the cells to try and top balance them. At this rate, it might be just a hair shy of never that they're done.

In the meantime, I went ahead and ordered the inverter side of things:

• 2 x Quattro 5000 / 48v inverter/chargers
• Victron Lynx Shunt
• Victron Distributor + Power-In
• 2 x Micro-Air EasyStarts
• Misc cables, fuses, and switches

Once these arrive, I'll be able to start bench building it all in my house so that I have it all figured out, configured, and documented before heading out to take it into the RV.

It'll also let me use the inverter to bulk discharge + charge the batteries.

[NJKris]

You need to get that big rod that catches a wire which is electrified with a lightning strike to charge. As seen on Back to the Future. At least buy the sign, only 10 bucks on Amazon!
https://www.amazon.com/dp/B09992DS4P...NrPXRydWU&th=1

[Ballistic]

As well as reaching 88mph!

[NJKris]

Yes, now he has to buy better tires with a 90 mph speed rating!

[ependydad]

(Sorry, I know just about no one is reading this blathering- it helps me to write it out and get it out of my head so I can refer to it later.)

I welcome any and all input. I just finished a draft of my wiring diagram to show me how all of these pieces come together.


Download PDF version - https://drive.google.com/file/d/14VF51P1hqGCt4lR-oD4DeelqB70Hl02q/view?usp=sharing

The gist of it is that the batteries are wired together using a Lynx Power In. This keeps the wiring tidy. This then hooks into the Lynx Shunt. Along side of that, most of the proper wiring and fusing are handled by the Lynx Distributor. The Cerbo is a piece that communicates the status out to the Victron apps and some kind of web portal for managing all of it; honestly, I'm not sure how that latter portion works.

Off of the distributor are a couple of things. First and foremost, the pair of Quattro 5000 watt inverter/chargers. After that, I have a pair of Orion 48v-to-12v step-down converters for feeding the existing 12v system. They're paralleled together for a total of 60amps. I'll need to see what the built-in converter puts out so that I'm supporting that.

Then there are a few other things- I would like to get some kind of battery bank charging while driving down the road, so I'll be adding a Sterling 12-to-48v battery charger. (I'm realizing now that I've likely messed up by having the charging output from it go straight to the Power In, which will likely make it bypass the shunt.) I also need to ensure that this is ignition protected.

I then have a Battery Isolation Manager (BIM) that is supposed to cross-charge the house and chassis batteries. I haven't yet decided if I'm keeping this or ditching it. If I keep it, my fixed output of the Orion 48v to 12v step-down converter should allow it to send a charge to the chassis batteries. I don't need any kind of reverse charging.

And finally, a future Doug problem is how to start the generator. The start up load that it puts on the 12v system is intense and likely will exceed the capacity of the Orion step-down converters. There's a "battery boost" button that essentially jumps the generator off of the chassis batteries. I'm hopeful that this will be enough to let me start the generator as needed. We'll see, though.

[NJKris]

Your wiring diagram is so beautiful and professional. Thought I'd show you mine since you showed me yours!

[ependydad]

Originally Posted by NJKris

Your wiring diagram is so beautiful and professional. Thought I'd show you mine since you showed me yours!

THAT'S IT! THAT'S THE MISSING PIECE! EXCELLENT!

lololol

[TitanMike]

Originally Posted by ependydad

(Sorry, I know just about no one is reading this blathering- it helps me to write it out and get it out of my head so I can refer to it later.)



And finally, a future Doug problem is how to start the generator. The start up load that it puts on the 12v system is intense and likely will exceed the capacity of the Orion step-down converters. There's a "battery boost" button that essentially jumps the generator off of the chassis batteries. I'm hopeful that this will be enough to let me start the generator as needed. We'll see, though.

I'm reading and finding it interesting. Am especially interested in the final tally of $$$$$$$$ when completed

Looking at your two batteries and their individual disconnect switches a question comes to mind. If you have one fully charged battery that is switched off, and one mostly discharged battery you've been using, what do you think will happen when you switch on the fully charged battery?

LiFePo4 batteries have extremely low internal resistance and as I see it, connecting a fully charged battery to a discharged battery will result in a HUGE current flow. Hopefully the BMS on one battery or the other will be able to control it if it exceeds the C rate max. Current could well be high enough that the BMS will switch both batteries offline and until their respective SOC's are equalized you won't be able to parallel. One at a time may be the only mode available and some form of a safety interlock might be desirable. Or just leave them in parallel like one would do with a smaller battery bank.

I can understand the desire to isolate one battery from the other for shorter charge times but unless there is some other protection in the circuit I would worry about some major problems if switching to fully charged while still connected to the discharged one.


As for the generator, a 5500 watt generator will certainly get a good workout unless it has a lot of solar to help it out. Numbers still running around in my head are saying it will take ~6 hours of generator running at full speed/max output with no other loads to charge both batteries from empty to full. Longer if your charger(s) can't deliver 115 amp (5500w/48v)
Charging and running A/C at the same time could really be problematic as the power consumption by the A/C's will lengthen the charge time required by a considerable amount. A/C's will probably consume somewhere around 50% of the power produced by the generator and now increasing the charging time to 12 hours. All this is of course worst case scenario but in a hot climate it could be highly probable.

You may need to find a small Nuclear Power Reactor or maybe a Flux Capacitor to tow around behind you when off grid

[ependydad]

Originally Posted by TitanMike

I'm reading and finding it interesting. Am especially interested in the final tally of $$$$$$$$ when completed

Looking at your two batteries and their individual disconnect switches a question comes to mind. If you have one fully charged battery that is switched off, and one mostly discharged battery you've been using, what do you think will happen when you switch on the fully charged battery?

{snip}

I can understand the desire to isolate one battery from the other for shorter charge times but unless there is some other protection in the circuit I would worry about some major problems if switching to fully charged while still connected to the discharged one.

Honestly, those 2 battery disconnect switches are solely there for isolating the batteries in the event that I need to work on something. I intend to always leave them paralleled together and hope that I never need those switches except for maybe periodic balancing of the packs.

Originally Posted by TitanMike

As for the generator, a 5500 watt generator will certainly get a good workout unless it has a lot of solar to help it out. Numbers still running around in my head are saying it will take ~6 hours of generator running at full speed/max output with no other loads to charge both batteries from empty to full. Longer if your charger(s) can't deliver 115 amp (5500w/48v)
Charging and running A/C at the same time could really be problematic as the power consumption by the A/C's will lengthen the charge time required by a considerable amount. A/C's will probably consume somewhere around 50% of the power produced by the generator and now increasing the charging time to 12 hours. All this is of course worst case scenario but in a hot climate it could be highly probable.

You may need to find a small Nuclear Power Reactor or maybe a Flux Capacitor to tow around behind you when off grid

I hope that with the size of the battery pack that I'll never be in a situation that I need to charge them from empty. The initial design plan is to run the A/C overnight with that discharge. Even running both for 10 hours, that should leave me with over 50% SOC in the morning.

Each Quattro pushes out up to 70amps of charging power. But I haven't equated that back to the number of 120v amps from the generator itself. And you're right, running the A/C will definitely lengthen it.

--

As for solar, that'll come later, but I think my intention right now is that the RV is 12' 10" tall. I have the room to build a rack that goes above them and should essentially allow me to black out the roof with solar, giving me north of 3000W up there.

[TitanMike]

Originally Posted by ependydad

Each Quattro pushes out up to 70amps of charging power. But I haven't equated that back to the number of 120v amps from the generator itself.

It's easier to think in terms of WATTS.

If your Quattro is pushing out 70 amps at 48 Volts then the wattage is 3360 watts. Two Quattro's running at same time will need 6720 watts which will equate to 56 amps being used on the 120 volt supply side.

This assumes perfect conversion but in real world numbers it will be pretty close to 7,000 watts or 1500 watts more than your generator is capable of.

Might only be able to run one Quattro if having only Generator power. Using "charging from empty" as a worst case scenario, one Quattro will mean a 9-10 hour charge time for both batteries.

Once you get all set up and put it all to the test you'll have a good idea of whether or not you'll need a bigger generator. Especially after you get as much solar in place as is practical.

[TitanMike]

Originally Posted by ependydad

I intend to always leave them paralleled together and hope that I never need those switches except for maybe periodic balancing of the packs.

If you leave your "packs" in parallel your BMS (both of them) will keep each pack's cells balanced. No real need for "periodic balancing" once the initial top balancing prior to assembly is really necessary. I assume your Overkill BMS's are 48 volt units. If so, they'll handle the balancing details whenever you are charging the cells.

[ependydad]

Originally Posted by TitanMike

It's easier to think in terms of WATTS.

If your Quattro is pushing out 70 amps at 48 Volts then the wattage is 3360 watts. Two Quattro's running at same time will need 6720 watts which will equate to 56 amps being used on the 120 volt supply side.

This assumes perfect conversion but in real world numbers it will be pretty close to 7,000 watts or 1500 watts more than your generator is capable of.

Might only be able to run one Quattro if having only Generator power. Using "charging from empty" as a worst case scenario, one Quattro will mean a 9-10 hour charge time for both batteries.

Once you get all set up and put it all to the test you'll have a good idea of whether or not you'll need a bigger generator. Especially after you get as much solar in place as is practical.

That really was so much easier to think about. I don't know why I got wound around the axle on that one. Thanks for the math assistance.

I know I have the ability to program the Quattros, so I should be able to manage the recharging.

And while 10 hours of generator runtime isn't ideal (for myself OR my neighbors), I'm honestly not 100% against the idea until I can get my solar up onto the roof.

[ependydad]

Originally Posted by TitanMike

If you leave your "packs" in parallel your BMS (both of them) will keep each pack's cells balanced. No real need for "periodic balancing" once the initial top balancing prior to assembly is really necessary. I assume your Overkill BMS's are 48 volt units. If so, they'll handle the balancing details whenever you are charging the cells.

Yeah, I agree. They are 48v units and should keep the cells balanced and the Quattros should keep the packs balanced. I've just heard there's theoretical float between them with folks who have gone 48v before.

We'll see. That's a future Doug problem, but I have the disconnects in the case that I need them.

[TitanMike]

Originally Posted by ependydad

And while 10 hours of generator runtime isn't ideal (for myself OR my neighbors), I'm honestly not 100% against the idea until I can get my solar up onto the roof.

The only thing I see from up here in the bleachers is that you'll be running the generator during the daytime which is also A/C "prime time". Generator will be having to do two jobs at once.

The unknown is how often the compressor(s) for A/C will actually be running and that will depend on how hot the day is as well as T-Stat settings.

Nothing will be certain until it all gets switched on.

Solar will definitely help a lot and the good news there is that it does it's best work during the daytime which will be a big help with the peak power demand.

[ependydad]

My inverters, distributors, shunt, and variety of fuses/circuit breakers came in! I was ELATED! And then I opened the inverters and BOTH are damaged in some way.

Inverter #1:




Inverter #2: