Stand alone system for power in class A motorhome

[justinm001]

First off renogy is junk and their support is horrible so don't listen to them.

Yes the shunt is right but everything to the left of the lithium is wrong.

Like supervstech said if you're trying to hookup the lead acid it needs to have a neg from house to before the shunt and use 4/0 wire everywhere or how you drew the last photo which is more complicated.

A DC to DC charger going from lead acid to lithium would allow you to use the alternator to charge the lithium and house. It'll limit how much charging they can take so you don't overheat the alternator.

A DC to DC charger going from lithium to lead acid will allow you to use lithium for your 12v house loads and charge the lead acid from the lithium.

You can have either or both. If setting up like your photo with some manual switch you'll need to move the house + to the buss bar and the Neg to the shunt or buss bar depending on how you want to use the shunt. Ideally 2 shunts 1 for each. The biggest issue is if you flip that switch then the renogy and solar charging profiles need to be changed each time from lead acid to lithium.

 

[justinm001]

Isn't that the way all 12v loads work? If it did not there would be a hundred wires going to the negative cable?

Yes and no. You want large loads going through neg wires and the small ones doesn't need to be. Usually there are hundreds of wires going to negative they're just using buss bars just like the positive.

 

[ampmike]

Yes and no. You want large loads going through neg wires and the small ones doesn't need to be. Usually there are hundreds of wires going to negative they're just using buss bars just like the positive.

Headlights for instance have their ground going to the chassis, starter goes to chassis, so I don't understand.

 

[justinm001]

Headlights for instance have their ground going to the chassis, starter goes to chassis, so I don't understand.

Engine is has a huge ground cable and Headlights don't use much power 10amps no big deal but 200 is.

 

[ampmike]

First off renogy is junk and their support is horrible so don't listen to them.

Yes the shunt is right but everything to the left of the lithium is wrong.

Like supervstech said if you're trying to hookup the lead acid it needs to have a neg from house to before the shunt and use 4/0 wire everywhere or how you drew the last photo which is more complicated.

A DC to DC charger going from lead acid to lithium would allow you to use the alternator to charge the lithium and house. It'll limit how much charging they can take so you don't overheat the alternator.

A DC to DC charger going from lithium to lead acid will allow you to use lithium for your 12v house loads and charge the lead acid from the lithium.

You can have either or both. If setting up like your photo with some manual switch you'll need to move the house + to the buss bar and the Neg to the shunt or buss bar depending on how you want to use the shunt. Ideally 2 shunts 1 for each. The biggest issue is if you flip that switch then the renogy and solar charging profiles need to be changed each time from lead acid to lithium.

When I first wanted to do this project the tech at M&M Electronics mentioned that I would need a DC-DC charger from the LA to lifepo batteries but said that trying to charge 400ah of lithium batteries would probably kill my alternator often and I would have to disable my emergency start system as my older battery control center was not compatible with lithium. So I'd like to not alter the way my factory BCC, house battery, emergency start and generator are wired as it works perfect. I just want the ability while dry camping to be able to use my 110 for things like microwave, portable vacuum cleaner. coffee maker etc. after generator hours. I also would like to run my TV, heater fan, CPAP without fear of running down the house batteries.

 

[justinm001]

If you just replace lead acid with lithium then yes the alternator will burn up trying to charge it.

You're missing the point, you can't mix both battery types and if you use a switch you need to change the profiles on all devices.

 

[ampmike]

When I first wanted to do this project the tech at M&M Electronics mentioned that I would need a DC-DC charger from the LA to lifepo batteries but said that trying to charge 400ah of lithium batteries would probably kill my alternator often and I would have to disable my emergency start system as my older battery control center was not compatible with lithium. So I'd like to not alter the way my factory BCC, house battery, emergency start and generator are wired as it works perfect. I just want the ability while dry camping to be able to use my 110 for things like microwave, portable vacuum cleaner. coffee maker etc. after generator hours. I also would like to run my TV, heater fan, CPAP without fear of running down the house batteries.

Ok so is this part of the system right? What is a 3000 watt inverter is good that I can afford like the Renogy?

 

[justinm001]

Yes all correct except not sure what the Victron charger is for as the renogy inverter should be a charger.

Not sure of a cheap inverter but nothing compares to Victron

 

[ampmike]

Yes all correct except not sure what the Victron charger is for as the renogy inverter should be a charger.

Not sure of a cheap inverter but nothing compares to Victron

So I can charge the batteries at home or at an RV park if the solar does not keep up with demand. The Renogy is just an inverter not
inverter/ charger.

 

[Dzl]

So I can charge the batteries at home or at an RV park if the solar does not keep up with demand. The Renogy is just an inverter not
inverter/ charger.

How much do the victron charger and renogy inverter cost in total? You probably are not too far off from the cost of a decent inverter/charger. Victron Multiplus-ii or the original Multiplus would be a good option, but they are pricey.

 

[ampmike]

How much do the victron charger and renogy inverter cost in total? You probably are not too far off from the cost of a decent inverter/charger. Victron Multiplus-ii or the original Multiplus would be a good option, but they are pricey.

About $570

 

[justinm001]

About $570

I know its like double the price but dude just buy this and get it done once and for good. an MP1 would be cheaper and work just as well I just didn't see it on CC's site in12v. You get what you pay for

Victron 12V MultiPlus-II 3kVA 2x120V Inverter/Charger | Current Connected

Power, adaptability, and efficiency combined - the MultiPlus-II 2x120V Inverter delivers unparalleled performance for your energy system needs.

www.currentconnected.com

 

[Tomthumb62]

Renogy recommended those wire sizes

You can ignore that. They don’t know what they’re talking about, lol. Seriously.

A 3000W 12v inverter will need a path from inverter to bus bar to battery of 4/0AWG. If you can size up the cable from battery to bus bar, even better. Get yourself QUALITY cable from someplace like Windy Nation or battery cables USA dot com:

0000 Gauge (4/0 AWG) Battery Cable with Ends OFC Copper Flexible Stranded UL MTW/THW/SGT

www.batterycablesusa.com

 

[Tomthumb62]

First off renogy is junk and their support is horrible so don't listen to them.

It’s not complete junk, but it’s overpriced for the poor quality you get. If I were living full time or spending lots of time boondocking, I’d skip Renogy for anything other than panels.

Their support is better than it used to be. But frustrating as heck. They’re very nice and quick to reply but slow to resolve the issue. Groan… I’m dealing with them now.

 

[Rocketman]

One item that REALLY helps RV’s is dedicated solar panels on the roof.
Yep - they are flat…
Yep - sometimes you park under trees…

But they always are trying to keep the battery charged.

If you decide to have your two battery banks - consider having two permanent solar arrays - one to each battery bank.

The first 300-400w of solar is the best bang for the buck.

We full-time boondock and 1400w of solar is right for us - but I wouldn’t mind more?.

Good Luck!

 

[ampmike]

One item that REALLY helps RV’s is dedicated solar panels on the roof.
Yep - they are flat…
Yep - sometimes you park under trees…

But they always are trying to keep the battery charged.

If you decide to have your two battery banks - consider having two permanent solar arrays - one to each battery bank.

The first 300-400w of solar is the best bang for the buck.

We full-time boondock and 1400w of solar is right for us - but I wouldn’t mind more?.

Good Luck!

Being on a budget I am going to use the Dokio 300 watt for the time being.

 

[ampmike]

I am kind of back to the drawing board. So, I have two questions.
On the first attachment, in the case of a battery going south would I be better with #1 or #2?
on the second attachment the location of where I need to put the inverter and space available.
Any suggestions on a 3000-watt inverter that would fit and have ample cooling space around it?

 

[HRTKD]

Another reason for not using the DC to DC charger is when the motorhome is running the alternator will try to charge the Lithium batteries too and if they are way down it over work the alternator.

There have been a couple of responses already to this, but I wanted to add to them. For folks with an RV that want to charge the batteries from either the tow vehicle (in a trailer) or the engine (motorhome), one of the main points of using a LiFePO4-aware DC-DC charger is that it WON'T overtax the alternator if the DC-DC charger is sized appropriately. If you purchase a 20 amp DC-DC charger, it won't pull more than about 30 amps out of the alternator.

justinm001's point about getting an inverter/charger may be more expensive up front, but it's a heck of a lot easier down the road. No plugging/unplugging the shore power from the inverter and no flipping switches. A Victron Multiplus 12/3000 can charge the battery bank at up to 120 amps! That's really important if you're using a generator to get the most charging in the least amount of time.

With regard to your latest battery wiring question, illustration 1 is the best option. You'll have nicely balanced batteries that way.

For the mounting location of the inverter, how close will that be to the battery bank? RV's are short on space but sometimes you can find dead space behind panels or under closets. I ended up mounting my Multiplus inside a closet and the batteries are in what was previously dead space below the closet.

 

[Supervstech]

I am kind of back to the drawing board. So, I have two questions.
On the first attachment, in the case of a battery going south would I be better with #1 or #2?
on the second attachment the location of where I need to put the inverter and space available.
Any suggestions on a 3000-watt inverter that would fit and have ample cooling space around it?

#1
Because #2 is completely wrong.

 

[ampmike]

There have been a couple of responses already to this, but I wanted to add to them. For folks with an RV that want to charge the batteries from either the tow vehicle (in a trailer) or the engine (motorhome), one of the main points of using a LiFePO4-aware DC-DC charger is that it WON'T overtax the alternator if the DC-DC charger is sized appropriately. If you purchase a 20 amp DC-DC charger, it won't pull more than about 30 amps out of the alternator.

justinm001's point about getting an inverter/charger may be more expensive up front, but it's a heck of a lot easier down the road. No plugging/unplugging the shore power from the inverter and no flipping switches. A Victron Multiplus 12/3000 can charge the battery bank at up to 120 amps! That's really important if you're using a generator to get the most charging in the least amount of time.

With regard to your latest battery wiring question, illustration 1 is the best option. You'll have nicely balanced batteries that way.

For the mounting location of the inverter, how close will that be to the battery bank? RV's are short on space but sometimes you can find dead space behind panels or under closets. I ended up mounting my Multiplus inside a closet and the batteries are in what was previously dead space below the closet.

I am wanting to put the battery bank under the bed where the converter is. That will be directly above the inverter.
What is the purpose of the DC-DC charger?
I plan on not using the generator to charge the battery bank. I am hoping that my solar will charge enough between rv parks
I still want this to be a stand alone system that does not interfere or be connected to the factory setup.
My closet is on a slideout