Looking for constructive input - Upgrading system in my Class A

ldswofford

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Sep 3, 2021
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Newbie to this group. I have a 20 year old Class A RV that I am upgrading the battery/charging system(s) after migrating from a dual fuel refrigerator to a residential refrigerator. Eventually, I will be adding solar charging to the system, but I have to start slowly.
The existing system is 120V (shore/generator) and 12VDV (old converter/(2) 6V lead acid batteries).
I could just try adding in a pure sine inverter, but I have decided to go a step (or two) beyond... to adding in a new inverter charger to where it will take input from the shore/generator auto transfer switch and will then have the 120V output be input to the 30amp main breaker panel (30 amp RV, not 50amp... it is old).
I have a Victron Multiplus 12V 3000W inverter/charger that I will be using and am presently looking for "reasonable" battery recommendations. The plan(for now) is to look for either (1) 12V/200AH LiFePO4 or (2) 12V/100Ah LiFePO4 in parallel. Thinking the 1 larger battery reduces wiring connections, as no battery to battery jumpers are needed. I believe I have a space inside the RV bedroom that is in close proximity to the main 120V/DC panel/transfer switch area where I can mount the battery/batteries below in one cabinet and the Victron above in another, which should keep the wiring runs to less than 4-5 foot max.
I am attaching an overview diagram to this posting and am looking for feedback on good/bad/stupid/dangerous as to what I think I need to do. I also would like to know if I have oversized/undersized any of the fuses/shunt/etc.

While I have read a ton, I am no expert here, so please be gentle....and constructive. Also Any recommendations on 'reasonably priced' fuses/shunts/disconnect switches/etc. are appreciated.

Thanks, in advance,
Larry
 

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ldswofford

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True....I guess with all things a certain level of risk is involved, right? however, if I only have one battery and it dies, I lose ALL DC power to the coach...and if I have 2 in parallel, then I could remove it (temporarily) and still have functionality in the coach to be able to have lights/etc until the disabled one is reset/replaced/etc....
 

eXodus

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(1) 12V/200AH LiFePO4 or (2) 12V/100Ah LiFePO4 in parallel.
Depending on the battery you are using - those things can only provide 200A - so that's on the edge for feeding the 3000 Multiplus (low power)

In what shape are your 6V batteries? if money is an issue - you can hook your new LFP (200AH) parallel to your existing lead batteries - change the charging profile to LFP. That gives you another year or two to buy a second large LFP 200AH.

The lead batteries do fine in combination for LFP. They actually like it.

Also Any recommendations on 'reasonably priced' fuses/shunts/disconnect switches/etc. are appreciated.
you don't need a shunt. - That's a nice to have feature.

You only need one master disconnect - right after the battery positive - second one not required.

Read the victron manual what fuses they are recommending for size for this Inverter. 400A seems large. I would have guessed 250A or 300A
 

ldswofford

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eXodus, Thanks for the comment. I know that the 200A is on the low end for the Victron (but I got a REALLY great deal on it) and it is just the starting point, primarily to handle the refrigerator while we are going down the road or overnight boondock while travelling. My plan has been to grow incrementally over time (and as money flow allows). Concerning keeping the 6V(s), I guess I misread/misunderstood something, as I didn't think you could mix LA and LFP, even by changing the profile. I thought the batteries would/could never come up to full charge and since the LA batteries would effective drain off and damage themselves if they went below 50% that they would then impact the LFP batteries....
My LA batteries are 4+ years old, so I guess it might not hurt to look into it.

The other thing that you actually had me thinking about is how quickly I would need to increase, at least to the add one more battery. I actually changed my mind on the location of where I wanted to put the Victron and the batteries, as I had originally planned for them to go into a storage compartment mid-coach under the passenger side of the RV, close to where the LA batteries are located under the entry steps. I ran into an issue when I tried to see if I could use an existing mfg.'s wire chase to get the 120V to/from wiring under the floor to the transfer switch/main panel which is at the rear on the driver's side. This would mean that I would need to do the run externally, underneath the RV. That is when I thought about using the space where the laundry hamper is located in the bedroom just below the main panel itself. I may need to re-think this again, as the storage compartment is large and could accommodate many more batteries (in the future). It will just be a much longer wire run to the main panel and will have to handle exterior conditions....hmmmm

and finally, yes, need to go read the manual again... I had seen another RV-tech guy's setup and he used 400A fuses... but he probably had a large battery array...
 

eXodus

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Concerning keeping the 6V(s), I guess I misread/misunderstood something, as I didn't think you could mix LA and LFP, even by changing the profile. I thought the batteries would/could never come up to full charge and since the LA batteries would effective drain off and damage themselves if they went below 50% that they would then impact the LFP batteries....
6V golf cart batteries are incredible robust creatures. You can run them with slightly off voltages for a long time. (check the water) Usually the used market for those is non existent - before they go to the recycling place- get a few more cycles out of them.

LFP don't like lead charging profile (bulk + float) Lead couldn't care less - as long they get full charge once in a while.
The LFP profile only charges with 14.4V instead of 14.8V - so the lead takes 9 hours instead of 3-4h. But when you are plugged in once in while - shouldn't matter

IF you are concerned about draining the lead to deep - just adjust the low voltage protection on the Multiplus to 12V. That should keep them above 50% SOC

I mean in total you got so a lot more capacity - LFP + LEAD - so you are not as worried as leaving some AH unusable.
 
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eXodus

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and finally, yes, need to go read the manual again... I had seen another RV-tech guy's setup and he used 400A fuses... but he probably had a large battery array...
battery doesn't determine fuse size - the weakest link in the circuit does. The fuse should protect the weakest link (if that might be a wire or the appliance)
 

jberger

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Jun 1, 2021
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You will love love love that residential fridge, it's one of the best upgrades you can make in a coach. We are actually using less power to keep the resi fridge running than it took with 12v and propane before.

Which Victron are using?
Is it this one: https://www.victronenergy.com/inverters-chargers/multiplus-ii-2x-120v
This is new to the line up and lets you remove the old transfer switch plus gives a power boost on L1 in case you have multiple large loads at the same time. Say you are running the AC and need to use the microwave for a few minutes. If you want a simple setup, this is practically an all in one unit.

How are you incorporating the engine alternator in this setup?
You mention wanting to use the inverter while on the road and overnight boondocking, so you should let the alternator keep the bank charged while it's running. Depending on the output, you might not need to use the genny at all for those loads, that's what we are doing.

I would not put all this stuff inside a cabinet if you have a reasonable option in the lower bays. Go check out last week's post on the guy who had an arc fire in his skoolie with the batteries under the chassis. Imagine having that happen in your wooden closet while you are asleep.

I'd go with the 200ah battery and just plan on adding another one ASAP. It's simpler, it's going to live longer given the DoD impacts of 2x the capacity etc.
 

ldswofford

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Sep 3, 2021
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jberger,
thanks for the comment and the reference to the Skoolie fire.
As for the Victron.... I have a Multiplus.... not Multiplus II... Our class A is a 20 year old 30amp coach, and I didn't see any immediate need to go for the Multiplus II, especially with the initial use plan...oh.... and the fact that I bought a brand new unit for under 3/4 of what a new (old-stock) Multiplus normally sells for (the person bought 2 12/3000/120 units, then decided to go 24V on his install. He may still have the other one for sale if someone needs one). Still get all the warranty and support, but saved a little money for the project.

I do plan on getting a second 200AH (again, either (2) 100AH or (1) 200AH) to match whatever I initially get (assuming I don't find a great deal on 400AH of batteries to start with). While I have a nice inverter, I probably won't try to go 'top of the line' on the batteries when I purchase them, as again, this is a 20 year old RV that we use for recreation, not living in daily, so I am not overlanding/boondocking constantly, needing to pull every ounce of energy every day. I was honestly considering the used medical units that Matt Prowse did a video on sometime back, but once that info was out there, the scavenger started buying them up and reselling them for twice what they bought them for....

Now, back to thinking about putting all this in a storage bay... I guess I have to go think about the path I have to route the wiring to determine how much I have to go buy....and whether to use solid 10ga UF-B or if they make some UF-B like 10ga stranded THHN... or whether some sort of flexible conduit would be needed, assuming it could even be used in this manner...

I guess I am just a frugal old guy looking to do this upgrade and save himself some money.....and not screw up badly....
Larry
 

ldswofford

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jberger.
I also forgot... if you have input on how to tie in the alternator into what I am doing, I would appreciate it.
My plan just has me removing the old converter, removing the old LA batteries, installing the Victron to the transfer switch and out to the 120V main panel input, installing the new batteries and cabling them to the Victron, then wiring them to the 12VDC main panel input.

I know that there is a solenoid in the Chassis system that has a connection to where when on shore/generator, if the coach batteries are 'full', then the converter output (old converter) for charging closes said solenoid and allows charging of the chassis battery.... but as for the alternator, I don't know the there is a reverse system to go to the coach batteries, if the chassis battery is full... I also think said solenoid is used via a switch to 'slave' the coach batteries to the chassis, just in case you need an extra boost to get the RV engine started.
 

Rocketman

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Sep 27, 2020
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484
Since you went with a Victron Multiplus inverter/charger, I would highly recommend setting the rest of the system up with Victron too.
You will need a way too control the inverter:
I went with the CCGX, but now I would go with the Cerbo. (There is a small panel you can buy, but I figured the money was better spent going toward the CCGX).

Get the Victron shunt - costs more but having all the data together is awesome!
 

jwelter99

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Dec 6, 2020
Messages
552
Newbie to this group. I have a 20 year old Class A RV that I am upgrading the battery/charging system(s) after migrating from a dual fuel refrigerator to a residential refrigerator. Eventually, I will be adding solar charging to the system, but I have to start slowly.
The existing system is 120V (shore/generator) and 12VDV (old converter/(2) 6V lead acid batteries).
I could just try adding in a pure sine inverter, but I have decided to go a step (or two) beyond... to adding in a new inverter charger to where it will take input from the shore/generator auto transfer switch and will then have the 120V output be input to the 30amp main breaker panel (30 amp RV, not 50amp... it is old).
I have a Victron Multiplus 12V 3000W inverter/charger that I will be using and am presently looking for "reasonable" battery recommendations. The plan(for now) is to look for either (1) 12V/200AH LiFePO4 or (2) 12V/100Ah LiFePO4 in parallel. Thinking the 1 larger battery reduces wiring connections, as no battery to battery jumpers are needed. I believe I have a space inside the RV bedroom that is in close proximity to the main 120V/DC panel/transfer switch area where I can mount the battery/batteries below in one cabinet and the Victron above in another, which should keep the wiring runs to less than 4-5 foot max.
I am attaching an overview diagram to this posting and am looking for feedback on good/bad/stupid/dangerous as to what I think I need to do. I also would like to know if I have oversized/undersized any of the fuses/shunt/etc.

While I have read a ton, I am no expert here, so please be gentle....and constructive. Also Any recommendations on 'reasonably priced' fuses/shunts/disconnect switches/etc. are appreciated.

Thanks, in advance,
Larry

I like to put the EMS after the ATS so that it also warns/protects from any generator issues; which can and do happen.
 

ldswofford

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jwelter99 and rocketman.
Thanks for the comment.
I see your point.... I was just leaving what already existed in place on the RV...which is where the EMS is located... on the 120V side just in front of the transfer switch.

On the all Victron, all the time... I may, but I thought the dongle also allowed configuration/control using blue tooth and the app. I know the Victron shunt monitors batteries via blue tooth and the app.
 

Rocketman

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484
Yes Bluetooth is awesome! I also find I use the CCGX screen more than the Bluetooth. The main reason is it brings everything together on one screen.

As far as batteries- building your own with the 272 to 280 ah cells is nice(and what I did and the cheapest way). If you don’t want to build your own look at the Lion energy ones - I saw a post that Costco has them back in stock for 1300 for two.
 

jwelter99

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jwelter99 and rocketman.
Thanks for the comment.
I see your point.... I was just leaving what already existed in place on the RV...which is where the EMS is located... on the 120V side just in front of the transfer switch.

On the all Victron, all the time... I may, but I thought the dongle also allowed configuration/control using blue tooth and the app. I know the Victron shunt monitors batteries via blue tooth and the app.

CCGX is end of life.

Go Cerebo and the new Touch 70 7 inch screen, opposed to the Touch 50 5 inch. Or if you are into linux and such you can roll your own using the Venus OS and a rPI.
 

jberger

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I don't know what your current alternator setup is, but I'd recommend you look at something like the Victron BMS
https://www.victronenergy.com/battery-management-systems/battery-management-system-bms-12-200 12/200
or you could look at their DC/DC chargers. Either way you need something to take care of the Alternator.

I am not running Victron myself, so you might have some of this in your model of multiplus, but the one above appears to have current limiting, smart battery controls, etc. This way you don't burn out your Alternator when you are charging. Your LiPo cells will need a different charge profile from your old house bank, and they will put a heavy strain on the Alternator when charging so my limiting the current you can keep from damaging the voltage regulator or the entire alternator itself.

You will still need a Battery Isolator and solenoid to connect and charge the chassis batteries or you can use a Victron isolator to handle that function as well. Moving to the Victron gives you full visibility and control of everything in the system so you can diagnose faults before they leave you stranded.
If your current battery isolator is 20 years old, go ahead and change it at the same time, save yourself the rework later.

We have a 300a Alternator that is actively fluid cooled, so in our case we can run at least 1 of the AC's from the Alternator output over the road while also charging the batteries but I do need to keep an eye on the gauges and manually switch loads to keep everything in check.

When watching my chassis batteries, they are rarely connected and charging for more than a few minutes after a start, but you still want to make sure you have them isolated so they don't cause your LiPo bank to overcharged.
Right now we have a intellitec BIRD with the Big Boy solenoid performing that function so I just have to watch the gauges to know it's working. When I overall the system, I want it all in a centrally managed system instead so I'm trying to learn the ins and outs of Victron myself.
 
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