The Build - 48 volt 280Ah - RV Integration

[RvNaut]

Good Day Arm Chair Electricians
I live in a 2004 Safari Trek 31SBD. It currently has no solar, a 12 battery bank made up of 4 6-volt golf cart batts ( buh bye none too soon) and Freedom 451 Inverter charge controller( also soon to go buh bye). My power needs are vaaaahst :D I run a full size desktop computer and home stereo, recording gear etc etc... and then I intend to add a mini-split... ditching the existing AC and Heat systems. maybe run fridge a hot water on solar... I suck and intend to suck a lot of electrons.

The battery is a 16s 280Ah 48-volt setup using an Overkill 16s 100 amp BMS Cells were US stock from Docan, total $2,469.60. The BMS was approx $170, including longer leads and monitor wires.

The case ... I have been looking at all manner of container solutions for the battery. I have not liked much of what I saw. Plastic boxes were never the right size and all seemed too fragile for the weight I would be putting in them. I then came across a Job Site Tool Box, that was a good fit, and then saw one on Scratch and Dent sale and scooped it up.

Here are the box and battery in a dry fit. I will have to build the battery "in place" when the time comes as the complete unit is 220#s ++ I have lined the bottom and sides with 1/2" closed cell neoprene foam. I will also line the inside of the lid with 1/16" foam where the BMS is not glued to the inside of the lid. I will also place a barrier sheet over the entire battery once built.








Would you consider.... Assemble as is with wax paper in between each cell, or Captan tape them in groups of 2 or 4 and let the tape be the wear points. These are very snug as is, but I can see vibration overtime causing an issue where cells touch. Because of the case build, things get to heavy to maneuver .. 4 groups of 4 taped with 1/8" foam between groups and middle?

I am looking at mounting the box on these....

https://www.amazon.com/PGFUN-Isolator-Stainless-Anti-Vibration-Absorber/dp/B09W6895VW/?_encoding=UTF8&pd_rd_w=HJDmU&content-id=amzn1.sym.8cf3b8ef-6a74-45dc-9f0d-6409eb523603&pf_rd_p=8cf3b8ef-6a74-45dc-9f0d-6409eb523603&pf_rd_r=QCSW0YV4SX1HZ5613CE8&pd_rd_wg=9jq6O&pd_rd_r=bb8b43d5-e574-4110-8256-b13260c3c333&ref_=pd_gw_ci_mcx_mi&th=1

For an All-In-One I am going with a Sigineer M3048NC

3000W Off Grid Stackable PV Inverter 80A MPPT Solar Charger DC 48V to 110V 120V with 40A Utility Charger 50HZ 60HZ

3000W Off Grid High Frequency Stackable Inverter 80A MPPT Solar Charger DC 48V to 110V 120V with 40A Utility Charger 50HZ 60HZ. M3000H-48LV

www.sigineer.com

....and for the interesting bit.. .Here is the schematic for the 120v system in the RV as it sits.


I will be working with a friend who is an electrical engineer in Oct to install all of the above and integrate it with the above existing systems. The 12v is easy, and that feed no longer will be supplying the 120, so I have a Victron 48->12 converter... with 120v load removed from the 12v side, the heaviest draw on the 12v side are the slide motors, so buh-bye massive 12v cables too. For feeding the 120v side, the simplest thing may be to hook up the 120 feed from the Sigineer to the exising feed at the Transfer switch. I do not intend to ever shut the system down as I live in the RV. I am removing the 4kw Onan built in generator, so that feed won't be needed anyway. I also have and plan to keep a small 2.8kw Inverter Generator that had a 30 amp plug that I use currently hooked up to the RV via the external shore power line. The challenge in the above schematic in the EMS system currently in place that sheds loads if they exceed supply.... finding and disabling this system could be a real wild goose chase, let alone iffy in terms of potentially getting that wrong.... so the thought to allow that to think it is still doing its job and leaving it alone...

Why 48volt? Cost and efficiency. If I exceed around 2kw of solar, that is at the top end of the 24v all-in-one units. A 48v all-in-one can go up to 4500+ PV input. I hope to initially get at least 2kw on the roof, but part of that includes deletion of the AC unti and install of the mini-split. (we'll burn that bridge when we get to it. 48 volt also means less $ in copper to move it about ( some of the marine 12v systems of this capacity use gargantuan wires)

Why all-in-one? You add up what a Victron system would cost to manage this setup? The Sigineer unit is $900, and it handles everything.. and yes it is a single point of failure, yet all systems face similar situations of any one component taking down the system. .. risks... versus money... I do.not.have.a.lot.of.money therefore this system is being built as cost effective as I can manage... look at the cost savings on the battery alone, let alone the the comparison between indv components and the all-in-one,,, my choice was and is, built it inexpensive or not at all... and I am taking my time because I am retired and on SS, and I have to... so .. yeah... that said.. I do encourage feedback... I will have fuses and breakers in line and a shunt on the 48v and 12v sides of things.... I have watched hours of Will's videos.. the only downsides to this system are the sheer weight of the battery and the slight risk of 48+ volt shocks... I have prolly neglected to mention something about the build, so do poke away...

 

[jberger]

You are going to need something more substantial than wax paper between the cells. I would not worry about the vibration springs, just bolt the case down solid and make sure you have something holding the cells in a place from the top so the don't rise upward on a big bounce.
Go check out the videos on the MASON DIY kits to get a good idea of what works. (fiberboard, foam and tie-down bars)

As for the rest of your plan, I'll just say that there is a reason Victron costs more and is used in numerous RV/Boat and Off Grid applications. It's the combination of features, flexibility and robust construction that is important.

Not sure why you want to pull out the Onan, those are very hardy generators. I'd keep it for the times you need it. Especially if you are going to keep using the external generator via the shoreline.

The Energy Management System is just a collection of relays that trigger in order of priority set by the EMS box. Those relays should be inside, or adjacent to your electrical panel. I'd imagine you are looking for something with a progressive dynamics label on it. I'd keep it so you have some automated load shedding that you can match to your situation.

Careful with the converter for the slideouts and levelers, the inrush current and sustained loads will burn out the cheap converters and might burn up your motors when it happens.

I'd also suggest spending some time on the hot water energy needs, I think you will be shocked to see how much battery it takes to run that electric element. Sticking with propane for heat will take a huge load off of your batteries.

 

[HRTKD]

As stated above, I would skip the isolation springs. I have two 4s batteries bolted to the floor of my bumper pull toy hauler that sees many rough BLM, Forest Service and county roads. I have no issues. The screws in my battery terminals are still tight after two years.

I would use something solid on the ends. Foam isn't solid enough in my opinion. I setup my compression fixture so there is no movement of the cells.

Flexible cutting board material is what a lot of forum members are using for between the cells. It's cheap, thin and easy to cut. But it's only for electrical isolation, not thermal isolation. If you're worried about your cells moving then you need a better system.

I considered ditching my Onan 5500 watt on-board generator. In the end, I kept it. It doesn't get used much, but when I do, it's for hours at a time. I camp in subzero weather (not intentionally) and the generator comes in handy on those days when I get 12" of snow dumped on me.

What are you going to do to exhaust the heat generated by the batteries from the box?

 

[MrThisIsME]

Add me to the third on ditching the Onan. Why pull something that is pulling of the main tank? Now you will have to store / haul out a generator, gas can and trips to fuel station. Not to mention, devalue the coach.

 

[OffGridInTheCity]

Agree with 'spring' comment above. I used RV heat pads + 1/2 'Marine Roll' (https://www.amazon.com/gp/product/B07G3J6294/ref=ppx_yo_dt_b_asin_title_o00_s00 ) under my batteries for a little shock absorbance in my 7 x 14 cargo trailer -> camper. The packs are twist-tie'ed to the top of the cabinets to hold snug against the foam. They're 18650 but the idea is the same and I've not had any trouble.

 

[RvNaut]

Hi All,
Thanks for the feedback. Here is one giant reply that tries to cover all the issues.

My 48/12 converter is a Victron.... One hopes that it is as good as it needs to be... There is no money to be saved going cheap on this part.

The same applies to the Overkill BMS and the Batteries.... good stuff...

The Onan is at least 18 years old and is sitting at 1200 hours. The rings are gone, gas gets in the oil and large volumes of smoke at start after a rest. I replaced the carb once... It weighs a lot and I plan on putting the external half of a mini split in that space. I have an Inverter Generator to put into use when needed due to lack of sun. The Mini split plan also means potential removal of both the Heat and AC units and be more efficient to boot. I currently use the gas line that feeds the generator to tap fuel for the external genset. Also.. the Onan is Loud and Vibrates, I have a 30' 50Amp cord built into the RV and can locate the already quiet genny a bit away. With the setup I have properly charged , I won't need the generator much... hopefully will run it once a month to exercize it... ..An onan Carb is $400, Chinese Carb $35.. Onan needs a rebuild. I will either rebuild it and sell, or just sell as is. It runs, but it needs help.

Devaluing the coach - it is already 18 years old. It will be my home until I die. I will be making other mods that wil also "devalue".. I don't care about resale value.

It is true that Victron makes good stuff, but I cannot afford it. I am bootstrapping this off a Social security retirement budget. This is my home, not a hobby. As above, I have put good money in where I had the cash to do so.

I am taping cells in two and then into groups of four and have sourced some 1/16" uhmw as dividers between these fours groups.


I have worked out a hold down system that slides in, rotates to wedge between the box edges and the batteries and will be also pushed down from the top by the lid. These two hold downs will then be screwed in on the lips, and possibly into the top as well( meaning having to unscrew these prior to opening) I do not hink that once I have the cells in place, that they will be moving anywhere.

The existing EMS... yes, simple relays.... buried in various place that are not documented. Yes there they are on the blueprints, but they are form the year before and there were major changes to the layout for my model and there were damn few even made, so finding them is apt to be a real treasure hunt. If I feed the 120V from the new Inverter/controller/converter into the genset feed in to the existing Transfer Switch, nothing changes as far as the EMS is concerned... and/or Bob's yer uncle. *If* when I dig into it in Oct with my Electrical Engineer friend, we can delete it, we will.

Heat dissipation should not be a huge issue on two levels, depending on placement, either in one of the basements, or in a closet. Thermostatic fans in the compartment and lots of venting holes in the lid of the enclosure.

Thanks for making me think

 

[MrThisIsME]

My 48/12 converter is a Victron.... One hopes that it is as good as it needs to be... There is no money to be saved going cheap on this part.

I agree. Only wish they made a larger unit. I current run two of them to get 60 amps in an RV. Some would think redundancy, but the hydraulic jacks (most important 12v item) would not last on 30 amps.

 

[HRTKD]

The Onan is at least 18 years old and is sitting at 1200 hours. The rings are gone, gas gets in the oil and large volumes of smoke at start after a rest. I replaced the carb once... It weighs a lot and I plan on putting the external half of a mini split in that space. I have an Inverter Generator to put into use when needed due to lack of sun. The Mini split plan also means potential removal of both the Heat and AC units and be more efficient to boot. I currently use the gas line that feeds the generator to tap fuel for the external genset. Also.. the Onan is Loud and Vibrates, I have a 30' 50Amp cord built into the RV and can locate the already quiet genny a bit away. With the setup I have properly charged , I won't need the generator much... hopefully will run it once a month to exercize it... ..An onan Carb is $400, Chinese Carb $35.. Onan needs a rebuild. I will either rebuild it and sell, or just sell as is. It runs, but it needs help.

LOL! When you put it that way, I probably would ditch the Onan too. Mine has 750 hours on it and I would guess that 50 of those have been me firing it up once a month to exercise it over the past five years.

 

[RvNaut]

Update time.... things move slow as I am on a SSI budget...

I have aquired and bench tested the entire solar system, but have not integrated it into the RV yet. I have refined the entire system several times over as a result of consulting with other RV owners and an electrical engineer.

Here is my schematic

Notes:

The chassis alt wants to send 14.2 back to the house batteries, so I am leaving the 12v house battery in place to catch that and act a s a buffer between the 48->12 converter and heavy demands on the 12v side.. slide motors and the hyd jack motor...

All 120v to wall plugs and micro now come from the existing inverter, that passes thru gen or shore power. I will add three breakers to feed 120v to the two mentioned circuits and a third for eventual connection back to the transfer switch.

 

[HRTKD]

The 120vac side looks like a loop to me. I would have the output from the transfer switch going to the input on the inverter. If you're completely ditching the generator then you no longer need a transfer switch at all. Shore power would then go directly to the input of the inverter. 120vac output of the inverter would go to (D) your existing breaker box.

 

[OffGridInTheCity]

Agree with @HRTKD that transfer switch not really needed. I added an ATS (see pic below) thinking my built-in generator might conflict with plugged in shore power at a camp site and with an ATS I could just fire up the generator and not worry about shore power. But it turns out that it's way too noisy to run a 'built-in' generator and it's not that hard to unplug shore power and plug in a generator at the side of the trailer since it's outside anyway.

Here's a couple of things I did for my trailer as ideas for you. I marked up you're drawing above to try to illustrate where these ideas come into play....


2 ideas....
1) A bypass switch down stream of the grid or generator input that can bypass the battery/inverter and go right to the 120vac power distribution center. This gives an option to continue to operate without the battery/inverter if the inverter/battery failed (or needs work) for some reason or for long term storage and you want to maintain power inside. Here's the wiring diagram based on this rotary switch https://www.amazon.com/gp/product/B07N119RY9/ref=ppx_yo_dt_b_search_asin_title (plus they offer a box to mount/house it).


2) Next, I did a 120vac -> 12vdc converter instead of 48vdc -> 12vdc. Here's a 30a example - https://www.amazon.com/Universal-Regulated-Switching-Converter-Transformer/dp/B08LDC41B6/ref=sr_1_20. I used an 80a but it was overkill. This makes the entire system 120vac based and the 12vdc operates from the incoming grid/generator. In conjunction with the bypass switch above, you're 12v subsystem will work even if the battery is off.
Some might say - "I don't want to run my inverter all the time" and it's true, the inverter has biggest losses, but in my case I do run it all the time for the refrigerator, mini-split, tv, etc. I can always go into bypass (above) if I need to. Next some might say - 120vac -> 12vdc has losses but they are negligible and you still have losses from 48vdc -> 12vdc.

Not pushing any of this, just sharing what works for me.
Good luck on you're build - look forward to future updates

 

[RvNaut]

The 120vac side looks like a loop to me.

It is not.. note the dotted line... when the Onan gen is removed, the line the gen uses to feed the transfer switch, will be used by the Inverter...
The transfer switch will be reversed to make the shore power line primary, cutting off power from the Inverter, when/if I plug in the external 2.8kw quiet/Sinwave genny, when it rains for three straight days...

 

[HRTKD]

It is not.. note the dotted line... when the Onan gen is removed, the line the gen uses to feed the transfer switch, will be used by the Inverter...
The transfer switch will be reversed to make the shore power line primary, cutting off power from the Inverter, when/if I plug in the external 2.8kw quiet/Sinwave genny, when it rains for three straight days...

So your external generator won't simply use the shore power plug?

 

[RvNaut]

So your external generator won't simply use the shore power plug?

It will. it will hit the transfer switch, which will automatically cut off the 120v out that passes through the gen connection and through the transfer switch. I may elect to throw the breaker on the out side of that line before plugging in, just to be safe...

 

[RvNaut]

Not pushing any of this, just sharing what works for me.
Good luck on you're build - look forward to future updates

Mine will be running 24/7 and that is the point. I live in it... I can turn off my inverter and still have 12v, without having to have the inverter up and running... but I imagine I won't ever turn it off....

 

[RvNaut]

Agree with @HRTKD that transfer switch not really needed.

The transfer switch is already in place on the RV. I have to have some way to make sure that 120 out from the inverter is not allowed to out when I am on gen or shore power. It seems to me that it is simplest to leave the RV as it is and adapt to it. I could very easily just flip the third new breaker to do this, but there needs to be some manner of auto-protection in place, and seeing that the transfer switch is already there, I will use that.

Does that clear this up?

 

[RvNaut]

So... it all comes closer... the latest challenge is deciphering the existing battery bay. I will be eliminating the heavy gauge wire to the existing inverter, and leaving a 12v deep cycle battery in the bay to act as a buffer between the 48-12 converter and to allow the chassis to charge this battery and allow the Boost function to connect it temporarily to the chassis batt, to jump start the engine if needed.

Below what I have figured out so far and some ??s as to what goes where.

 

[RvNaut]

RE going to 12v off of the 120v... by going direct form the 48v to the converter to 12v, I bypass the entire Inverter and the 120 system, so the inverter/controller can be off and I will still have 12v to the house.

 

[OffGridInTheCity]

RE going to 12v off of the 120v... by going direct form the 48v to the converter to 12v, I bypass the entire Inverter and the 120 system, so the inverter/controller can be off and I will still have 12v to the house.

Yes, but the battery must be active in this scenario. In my system, the incoming grid can bypass the inverter + battery and go to the distribution panel -> 12v.

I like to leave my battery (and inverter) off for the months of storage but still have 12v available. Also, a weird case for sure, if we're at a campground with power and something happens to the inverter and/or battery or battery is too low to use and can't be charged - we have 120v + 12v (all systems working) as long as we have external grid. The critical 12v item for me is the powered tonque jack.

It's not right or wrong, just choices