Super new guy, how’s this look?

[BDubya907]

Hi everyone,
So I’m really interested in beefing up the electrical on my motorhome. I’ve been doing quite a bit of research, but what I’m discovering is that I don’t know what I don’t know. On top of that, I’ve been a residential/commercial/industrial electrician for 20+ years, but almost no experience with DC, so I know just enough to be dangerous. I know where I want to end up, but was hoping you guys could offer some…course corrections.

•I have (8) EVE LF280K cells on the way. I’ll be assembling (2) 4S batteries with them. (We currently have (2) 101AH lead acid house batteries, and no inverter)
•I plan to purchase a Victron Multiplus II 12/3000 for our 50A motorhome
•I’d like to be able to charge from the stock alternator while driving (existing converter is at least 35A)
-> Renogy 20 DC-DC or Victron?
•I believe I’ll be using a 4S200A JBD BMS on each battery
•I believe I’ll be using a Raspberry Pi 4 with a touch screen instead of a Cerbo GX so that I can use the JBDs and still have communication between all my components and have the GUI
• I believe I should go with the Smart Shunt as it’s considerably more accurate than the BMS
• I plan on installing 1200W of Solar on the roof *next year*, so I’ll only be able to recharge with the onboard generator, shore power, and hopefully alternator.

My plan is to follow the widely available diagrams and I’ll be figuring out proper wire sizes. However, I don’t have the expertise to know for sure that all these components will play nicely, but I believe they will.

Can anyone offer any critiques or see where I might be making poor choices? I’m sure I’ve probably left out some pertinent info, so feel free to tell me what you need to know. Oh, I’m in Alaska, but we won’t be using the motorhome outside of spring, summer, and fall when temps are 40f or better. As far as anticipated loads…small coffee pot a few times a day, A/C isn’t necessary, but I want to make at least 1 unit (120v 20A) an option, charging a couple laptops, iPads, phones, we have two LED TVs and a Yamaha AV receiver with surround sound (600W system I believe), all LED interior lights, double fridge (RV size) microwave, and all the other “normal” RV stuff.

Thanks for any help, comments, suggestions, and critiques!

 

[MisterSandals]

I would seriously look at going 24V for your system. It’s a big system for 12V. Start looking at the amps you will be pulling, and the wiring and fusing it will require. This will help you decide whether 12V is even feasible.

 

[Zil]

OEM alternators are a poor choice for charging larger deep cycle Li batteries.

 

[littleharbor2]

I would seriously look at going 24V for your system. It’s a big system for 12V. Start looking at the amps you will be pulling, and the wiring and fusing it will require. This will help you decide whether 12V is even feasible.

There's noting stopping you from having a small 12 volt PV system for the RV's 12 volt loads and a larger 24 volt system strictly dedicated to the inverter loads. I've done this many times for myself and others. I like the redundancy of having separate systems.

 

[BDubya907]

I would seriously look at going 24V for your system. It’s a big system for 12V. Start looking at the amps you will be pulling, and the wiring and fusing it will require. This will help you decide whether 12V is even feasible.

Thanks for that @MisterSandals, I hadn’t thought of 24V, but I can definitely see how it would make the wiring, if nothing else, cheaper. I’ll need to look into the Multiplus 24/3000, but at first glance it doesn’t look like I lose any functionality when going with that rather than the Multiplus II 12/3000/120-50

 

[BDubya907]

OEM alternators are a poor choice for charging larger deep cycle Li batteries.

My understanding was that the DC to DC chargers would make this feasible. If I keep it sized the same as what my existing converter draws from the alternator, what problems would I have to deal with when using the OEM alternator?

 

[Koert]

There's noting stopping you from having a small 12 volt PV system for the RV's 12 volt loads and a larger 24 volt system strictly dedicated to the inverter loads.

Great idea.

When we got our first compressor refrigerator, instead of upgrading our entire electrical system, I added a lithium battery and solar panel that was dedicated to running the refrigerator and an inverter. Compared to revising our factory system, it made installation dead simple. And, in terms of monitoring available power, I liked the idea of protecting the coach batteries from the high power consumption of the refrigerator and inverter.

For BDubya's motorhome, it would be interesting to explore the idea of upgrading the existing coach batteries to two 100Ah lithium batteries to ensure that the basics (lights and fans) always had power. Then, the 560Ah of additional cells and a new inverter could be a separate 24V/120V system that is used only for "luxury" devices like the air conditioner, microwave, and entertainment system.

For example, there's nothing worse than not being able to use the water pump because using the microwave drained the batteries.

In terms of charging the most important batteries first, it would be best to have one big charging system that prioritized the 12V batteries and then overflowed into the 24V batteries. But it would probably be easier to have the 12V batteries be charged from the 24V batteries. Is that possible, or does it make more sense to just keep the two systems completely separated?

 

[littleharbor2]

Great idea.


In terms of charging the most important batteries first, it would be best to have one big charging system that prioritized the 12V batteries and then overflowed into the 24V batteries. But it would probably be easier to have the 12V batteries be charged from the 24V batteries. Is that possible, or does it make more sense to just keep the two systems completely separated?

I prefer keeping the two systems separate. If you're using 12 volt for lighting and are running all LED lights there's not going to be much draw there. Water pumps are typically intermittent so not much draw there either. Basically, in my opinion you can get by with a minimally sized 12 volt system.

 

[BDubya907]

Great idea.

When we got our first compressor refrigerator, instead of upgrading our entire electrical system, I added a lithium battery and solar panel that was dedicated to running the refrigerator and an inverter. Compared to revising our factory system, it made installation dead simple. And, in terms of monitoring available power, I liked the idea of protecting the coach batteries from the high power consumption of the refrigerator and inverter.

For BDubya's motorhome, it would be interesting to explore the idea of upgrading the existing coach batteries to two 100Ah lithium batteries to ensure that the basics (lights and fans) always had power. Then, the 560Ah of additional cells and a new inverter could be a separate 24V/120V system that is used only for "luxury" devices like the air conditioner, microwave, and entertainment system.

For example, there's nothing worse than not being able to use the water pump because using the microwave drained the batteries.

In terms of charging the most important batteries first, it would be best to have one big charging system that prioritized the 12V batteries and then overflowed into the 24V batteries. But it would probably be easier to have the 12V batteries be charged from the 24V batteries. Is that possible, or does it make more sense to just keep the two systems completely separated?

Thanks for that, @Koert. My biggest motivation for doing this, aside from it looking like an incredibly fun and rewarding project, is that we currently don’t have an inverter, so we either have to have hookups at an RV park ($20-50 a night) or run the generator ($3/hr).

Then there’s our potential future use of the motorhome. I work on an oilfield on the northern coast of Alaska, and we work rotationally. So, I go to work for two weeks straight, then I fly home and I’m off for two weeks. This would allow my wife and I to travel all over the country, and then when it’s time to go to work, I’d just go to the nearest airport, fly to Anchorage, and then the company fleet of Q400’s gets me to work from there. With this possibility in mind, there would most definitely be some boondocking, where I’d hate to interrupt the peace and quiet with a generator running. But, we have to have our coffee (Keurig, and a small Mr. Coffee pot) and charge laptops (my wife works from “home”,) and TVs for some Netflix and chill at night.

I do like the idea of 2 separate systems, I’ll have to chew on that for a little bit. I suppose for now, potentially, I could keep the existing house batteries and converter as they are, and put all this new stuff in as a separate system, and then change out the house batteries later.

 

[BDubya907]

I prefer keeping the two systems separate. If you're using 12 volt for lighting and are running all LED lights there's not going to be much draw there. Water pumps are typically intermittent so not much draw there either. Basically, in my opinion you can get by with a minimally sized 12 volt system.

What if I used (1) 12V 280ah battery to replace my existing house batteries, dedicated solely to 12V stuff, and the second 12V 280ah battery with the Victron Multiplus II 12/3000 50A as a new, separate system solely for 120v stuff? Both separate systems would need to charge by shore power, the 12V system also by alternator (using the existing converter?) and then when I do solar next year, could I use one large solar array to charge both systems?

 

[Browneye]

Separating the house loads from the chassis loads makes doing a simple 12V lifepo system easy. A 1000w inverter will cover your loads for coffee maker and charging electronics, TV and tuner, etc. Sized properly will power a residential refer as well. Wiring and fusing, and charging is much simpler as well. This is the route I took with my RV. It hasn't plugged into shorepower since the upgrade.

Running air conditioning is a whole 'nother can of worms. Yes, it can be done, takes a lot more power, heavier wiring and fusing, and a solid way to recharge.

I would recommend figuring out what your actual consumption needs are and then build a system to suit. And planning a way to recharge, so not plugging in or running genset means solar panels. Definitely consider a PV array to replace what you use each day.

I have a gas-absorption fridge that runs on LPG, same for water heater, and furnace. A 230A lifepo pack covers the need, and 600W of solar panels recharges each day. A 600W inverter runs the 110V stuff we want to use. This system cost a couple of thousand to build and works just killer.

I went with a Victron ORion dc to dc charger so we can get some juice when driving at night or on cloudy/rainy days. And a 55A converter/charger for quick charging with genset if we need it, or plugged in. If we need air conditioning we plug in or run the generator.

There is lots of help here if you flesh out your requirements and then do a connecting diagram of your components, to get you on the right track.

 

[BDubya907]

Thanks man! Yes, I will definitely establish what our demand will be, and draw out what I’m thinking, but the more I think the more drawings I’ll have to make?. Thanks for your insight!

 

[Browneye]

Understand that running an RV air conditioner can pull 100A at 12V pretty easily, probably more like 200A. That means even with your 560Ah of battery, it could use it up in a few hours if it's hot out. And then you need to way to put that energy back into the battery bank.

A 2000W inverter is realistically a max size for a 12V system, due to wiring and fusing requirements to carry that load. For high current systems higher voltage is an easier path to make it all work, but makes it a little more complicated. And still won't power an RV air unit.

Check in the Resources section for an energy audit template and start there with your estimates on what you want to run, how much energy it takes, and how long everything gets used. Then you can plan what you need to cover your actual needs.

My planning was easy because we had already been dry camping for most of the 17 years we've had the coach. And we got by with a single pair of golf cart batteries - they're good for about 100Ah usable. So building a DIY 230A lifepo pack gave me over twice the capacity for half the space and a third of the weight. Moved the house system inside which left more room in the old battery tray, so the chassis system was doubled up as well, and has it's own solar panel and controller to keep it topped up.

I removed the old isolator/combiner solenoid for chassis to house, completely separating the two systems, and then the dc to dc charger for the house pack while driving. Solar panels keeps everything charged up all the time.

Our 110V needs are very simple - TV/tuner, charging electronics, a residential box fan, and charge ebike batteries. I have a 600W inverter to cover those needs, but if you want to run a coffee pot you need at least a 1000W inverter. I bought a Delta Mini for those high-watt needs, as they are rarely needed. If you're building a system to cover regular high-watt appliances then it's easier to plan for them from the get-go.

My goal was an inexpensive and simple system. It was still a lot to learn, but I got a ton of help here form the members.

 

[wholybee]

I would seriously look at going 24V for your system. It’s a big system for 12V. Start looking at the amps you will be pulling, and the wiring and fusing it will require. This will help you decide whether 12V is even feasible.

His AC loads are small to moderate. I see no downside to 12V. If he installs a 2 or 3 burner electric cook top, then yes, 24v or 48v.

I have similar to him, and also a 900w induction plate, and have never pulled more that 100A. My 300Ah battery and 1500W inverter is plenty. 700W of solar completely supports it with never needing to plug in or charge from the alternator.

 

[MisterSandals]

His AC loads are small to moderate. I see no downside to 12V. If he installs a 2 or 3 burner electric cook top, then yes, 24v or 48v.

Agreed. I didn't think there was enough info for me to recommend 12V vs 24V so i recommended looking at the loads/amps closer.

 

[BDubya907]

Alright, so while I am still about 700 miles from my motorhome, I had my wife count up lights and send me rating labels from everything she could find, and I googled the rest to come up with our Energy Audit (needs fine tuning and some actual usage data). I did not count the slide outs or jacks, because those are both operated twice, and while the engine is running. The biggest shock to me was how much my wife paid for her "hair straightener" which I discovered when I google it to get the ratings for it. But I digress.... Oh, and I only put 100W in for the fridge because I think I'll just run that on propane, so 100W DC for the "brains".
Couple of things... I'm pretty certain I am going to go with 24V, and I'll order the Multiplus II 24/3000, smart shunt, raspberry Pi, (2) JBD 200A BMS, and I'll have my (8) EVE LF280K cells in a 4S2P configuration, for 24V and 8kWh.

It looks to me like I definitely need to plan on adding solar sooner than later. Anyone see any glaring problems here?

 

[littleharbor2]

5.59 kw a day is more than I burn in my entire Baja home. One thing I see right away is the largest single power draw. 1800 watts for a coffee maker. This can be cut down to 200 watts or so by getting an insulated coffee carafe. As soon as the brewing cycle ends turn off the maker and pour the hot coffee into the carafe.
Definitely see the need for a 24volt system after looking at this chart.

 

[Zil]

My idea of a motorhome life is not those massive highway cruisers. I would never expect to live off grid motorhome as I would use power in a S&B.

 

[BDubya907]

My idea of a motorhome life is not those massive highway cruisers. I would never expect to live off grid motorhome as I would use power in a S&B.

We’re not trying to live off grid, we just love to travel together. In Alaska, if you don’t get out and enjoy all the amazing places the roads can take you, you’re missing out! We’d like to expand our options and not be tied to campgrounds with hookups or have to run our generator all the time, so we’re just looking to upgrade what we’ve got for power and add solar.

 

[littleharbor2]

You don't need to explain your RV situation to anybody. I'm not sure why that comment was made and for damn sure it had nothing to offer as far as help. smh...