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Lithium LiFePO4 52v system
I should have started out by talking about some of the design philosophy, but I wanted to jump into the details first to entice you, dear readers.  

We like to boondock and moochdock a lot, and we don't like to run our generator all the time, and so the motivation here was to have a sizable energy system that is easy to use in practice and that permits considerable flexibility in how much and how often we have to burn diesel or find a power pole.

In a temperate climate, where air-conditioning is not needed, my estimate is that we should be able to run about four days before we need to recharge.  If we have average solar insolation, we should be able to run more than a week before we get low.

In a hot climate, I am estimating air-conditioning at 4 units * 50% duty cycle * 8 hours, which means we would need to recharge every 36 hours.  (If the climate is worse than that, I don't want to be there very long, to be honest!)

With good solar insolation, we should be able to hold off on that recharge until the next day, or about 48 hours.

With shade and some conservatism, we may be able to go as long as 3.5 days while still running some air-conditioning and all other normal loads.

On any 15A outlet, or better, except in the most extreme cases, we should be able to last a minimum of 7 days.

We can fully charge the pack off the genset in about 2.5 to 3 hours.  Or, under the typical scenarios described above, we could choose to top it off during the lunch hour every day, for example.
2008 Newell #1234
Boulder, CO

One of the major components of our remodel in Miami this winter was converting the midship half bath to an office and pantry area.  We have never needed two bathrooms in our RV, and we have always needed more space.  Moreover, I do sometimes actually do real work, and I use a standing desk at home, so this was a natural conversion choice.

On the forward side is my wall-mounted iMac, a fold-out desk area, and some adjustable storage above and below.  On the aft side is also adjustable shelving, where the toilet was before.


Sorry for the crummy vertical panos that are stretching the image...  I will take better pics and do another thread on our full remodel scope later.  These are to show one feature:  at the bottom, on the floor, directly under the window, you'll see a 5-inch tall box made of ultrawood veneer.

This office is directly atop the battery bay, and that wood covers a set of air exchange ducts that are plumbed straight down to the bay.  One duct has a small fan that exhausts the battery bay back into the office.  The other duct is actually connected all the way to the #3 roof air, and it has a fan as well to "boost" the flow.  This allows the battery bay to be cooled on even the hottest days, which protects the batteries and extends their lifetime.  It has not gotten nearly hot enough to validate that the system works as expected, but I am fairly confident it will do the job.

As a bonus, I have designed the pantry side with a floor access panel that would allow installing up to five additional strings of LFP cells on the floor there.  Should we discover that we want (need?  is that blasphemy?) even more capacity, we can easily move up to 0.93 of a Tesla in the future.  Right now, though, we are using that area to store dog food.   Smile
2008 Newell #1234
Boulder, CO

Our coach came with a half and half, swirly mix of carpet and marble/tile. This is a no-go with a big, fuzzy dog, plus we wanted to lighten up the coach anyway. We had Newell replace the floor with new tile, and in so doing they installed new floor heat mats throughout the coach.

The old Silverleaf system in our coach can only drive one zone of floor heat, and it can only do so via ten pulse-modulated, arbitrary settings ("0" to "9"). Since I want to remove Silverleaf anyway, and because Newell's only alternative was their Intrepid system they use on the new coaches (not an option, either practically, financially, or functionally for me), I had them simply pull all the floor heat power drops to the inverter bay as well.


Then, these floor mats were wired up into three zones: salon, bedroom, (rear) bath. Each zone is connected to a Nuheat Signature thermostat, and those are mounted on the front ceiling of the inverter bay -- because I am literally out of wall space the whole way around, and because in the event we don't have connectivity, someone may need to manually go outside and adjust floor heat settings if he or she doesn't like the defaults.

The beauty of this "solution" is that it didn't require any expensive and tedious runs for new thermostats in each area, and everything is easy to access and set on anyone's mobile device or via a browser:


Total floor heating is about 2500W, so this is another heat source that we can run off the battery, but in real life we probably won't. Diesel is still king for heating, I think.
2008 Newell #1234
Boulder, CO

I highly recommend building a big mobile power system so that you have an excuse to buy a FLIR thermal imager. These things are so fun, and they're useful for tons of stuff, too. You can see how your roof airs vent into the cabin. You can figure out if your slide seal is actually, you know, sealing. You can literally look at the heat patterns on your wheels after a hard drive to see if you are getting even wear.


But, for large lithium packs, the real motivation is to be able to look at a large number of cells or interconnects and very quickly determine if there are any issues. One poor connection could lead to big problems, and an imager is a good part of a defense-in-depth against a mistake. (Especially if you are a novice, like I am.)

Above, you can see the battery bank under a medium-sized load. The hottest point there is where all the energy is bussed up onto the single main pole of the big power contactor -- as it should be. More importantly (and not so obviously from that picture, sorry), each of the string wiring paths is heating up about the same as all of the others.

I'll be repeating this kind of testing over the first few weeks and months, as system gets used more and as the road jostling puts stresses on all the interconnects. I've already identified one bad crimp this way and rebuilt that wire. Needless to say, I am carrying a bunch of hardware and tools to be able to fix stuff during the early going!
2008 Newell #1234
Boulder, CO

I have one major request. Please come to Bella Terra so that Richard and I can climb over, under, and through your coach and properly drool over your system!
Forest & Cindy Olivier
1999 Foretravel 36' U320
former 1998 Newell 45' 2 slide #486 

former 1993 Newell 39' #337 
2011 Chevy Tahoe 

2010 Silverado w/ RZR 570LE
Oh yeah, come to Bella Terra!

Only thing that raised by eyebrows was the use of VHB tape to hold the panels to the roof. Owners of our era coaches will certify that that stuff eventually fails. If that is indeed what you did, then keep a close eye on it.
Richard and Rhonda Entrekin
99 Newell, 512
Subaru Outback Toad
Inverness, FL (when we're home Cool )
(04-14-2018, 04:17 AM)Richard Wrote: Oh yeah, come to Bella Terra!

Only thing that raised by eyebrows was the use of VHB tape to hold the panels to the roof. Owners of our era coaches will certify that that stuff eventually fails. If that is indeed what you did, then keep a close eye on it.

I sure wish we could come!  We are nominally stationary here in Boulder until the school year ends, and then anyway we have summertime commitments that force our hand/schedule.  I prefer being more serendipitous, but it's not going to happen this season.

Thanks for the heads-up on VHB.  Any idea if owners of your era coaches might've not used Dicor around the edges of it in the past?  I ask because (a) the perhaps-leading RV panel installer uses VHB and has never had a panel come up, and (b) I know the material is sensitive to UV/water, so the typical approach involves covering it up after installation.

Either way, we'll definitely be checking them on a decaying interval.  I already found one where the curvature on the roof prevented a good bond.
2008 Newell #1234
Boulder, CO

Thank you, Nebster (I’m sure you have a real name) - this is a great article and is something I would love to do as I am currently watching carefully as my battery bank is dying. Did this bank replace your engine start batteries? Which bay did you end up mounting this in? Should I do solar panels and a decent charge controller/monitor first or batteries first? I’m just starting this research so any help would be great!
Karen & Adrian Abshire 
1998 2 slide 45' Newell towing a 2012 Jeep Wrangler Rubicon Unlimited and a 2006 Mercedes SLK320 for wifey. 
Prior: 1985 Foretravel ORED 35, 1988 38' Foretravel U280, 2000 Foretravel 42' U320, 1990 Bluebird Wanderlodge WB40
(09-12-2018, 04:38 AM)pairodice Wrote: Thank you, Nebster (I’m sure you have a real name) - this is a great article and is something I would love to do as I am currently watching carefully as my battery bank is dying.  Did this bank replace your engine start batteries?  

Hi Adrian,

I decided to keep the engine start batteries.  The main reason for doing that is because it is hard to get 12V out of a 52V pack, and doing so would require me to add another discharge source onto the lithium bank.  I wanted only one discharge source to make it easier to ensure the pack will never be fully discharged.  If the pack ever gets too low, I need only shut down that one Victron inverter, and that removes all loads from the pack.

The other reason to keep the engine batteries around is that removing them doesn't gain me much -- they are in a different place that would be hard to use for something else productive.  Keeping them on board has little downside in terms of storage space, and reclaiming that space wouldn't give me more room for more lithium, really.

The final reason to keep them around is that they provide a degree of redundancy.  Even if the lithium bank has a major problem one day, I know that I can still start the engines, which means I can generate power that way and I can drive somewhere.

Quote:Which bay did you end up mounting this in?  

The batteries are in the regular battery bay.  You can see I reused the original Newell tray if you look closely at that picture.  I did have to modify it a little bit to give me an extra inch of vertical clearance on the bottom tray.  Your batteries will, no doubt, be different, so YMMV.

Quote:Should I do solar panels and a decent charge controller/monitor first or batteries first? 

Batteries are a much bigger leap, both in cost and complexity.  Solar makes a lot of sense if you enjoy boondocking in places where you don't otherwise need much air-conditioning, because with care you can then avoid even running the generator.  You really have to do the power budgeting, though, to figure out what your cost-benefit tradeoff will look like.  One problem with Newells is that we tend to have all the nice things onboard, which means we tend to use a lot more power than other motorhomes.  Your ability to reign that in will likely determine whether solar-only makes sense.

It is obviously a huge luxury to be able to run everything, whenever, even for days at a time, without having to plug in or have the genset spun up.  Also, the ability to use the big battery to do demand shifting lets us camp in places with 30A or 20A circuits while living like we are on a 50A/240V circuit.

Keep me posted as you make your decisions!
2008 Newell #1234
Boulder, CO

You had asked about the output of the genset and the associated cabling.  A 20KW set delivers ~83A and thusly is protected by an 80A overcurrent device. (I know you know all of this but for the benefit of our GURUS)  The shore power feeder is 50A and the XFER sw is rated accordingly (usually 60, 90 or even 100A contactors), the feeder from the XFER is landed on the MAIN LUGs of a main lug only panel (no main breaker).  The 50A breaker in the panel feeds the buddy plug.  Newell has typically installed #6-4 SO cable for power feeders including the feeder from the genset even though the Generator breaker is 80A.  So, when you are on generator the overcurrent protection is 80A (from your generator which exceeds the cable's capacity).  The reasoning here is, if you can use your coach's system under normal operating conditions from a 50A shore power, you are not likely to exceed a 50A pull from the generator.   I don't think I have ever pulled more than 11KW with the AH on and two ACs plus Edith cooking.

 It would certainly be possible to re-pull that cable with 4-4 or even 2-4 (but that might be a bit of as squeeze) to your inverter bay.  And, here again is it worth it?

My disclaimer:  All Newells are different and later models, than my 2000,  may have different sized wiring.

Really enjoyable post and do come to Bella Terra.
Gordon Jones

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