Stark Batteries finally in my Travato

[booster]

Originally Posted by gregmchugh

If you still have AGM batteries the big advantage solar provides is significantly reducing the time needed for generator charging when you are in place and not driving. In order to fully charge the AGM batteries run whatever generator you are using early in the day to handle the majority of the high charge amp bulk phase and then let the solar handle the rest of the rest of the bulk and absorption phases. A good understanding of your amp hour usage profile will let you know how long to run the generator and get the full charge completed by rather solar. Running a generator to handle the lower current long time period absorption phase is not the way to go unless you do it while driving using an engine generator.

This is good advice, and what a lot of us do, even without a generator. If you need a run to the store or dump station, you do it early in the day to get the bigger than solar charging from the alternator (even stock setups will do 80 amps in most cases) so the lower output solar has moretime to work. You will take about the same amount of time to from 85% full to 98% full as it does to go from 40% to 85%, but the current will drop quickly. We have an ammeter on the engine charging and shut it off once we get above 85% (unless it is very cloudy) and let the solar, which is better controlled, top the batteries off. You would do basically the same thing with a generator of any kind and style.

We don't know if the Agile has a gas or compressor frig, but with a gas frig the daily usage would probably be around 50 amp hours for many folks, may 85 amp hours with the compressor frig. 320 watts of solar should cover that with good sun, but will be much less in bad sun, so reserve capacity in the batteries are needed then.

As Greg said, a use profile would be very helpful, as would how much the solar can do maximum in a good day.

[gregmchugh]

Solar is so dependent on all the factors of the panels, shading, tilting, the time of year, the weather, the solar controller, wiring, etc., it is hard to make a general statement on what to expect. The only rough guideline that I have found to be reasonably accurate is to expect a daily power output of 25-35 amp hours for every 100 watts of solar. Again this is rough, you could do easily do worse with a poorly engineered system and you may get better but only on a really good setup.

[Davydd]

My 800ah lithium ion battery pack is covered by about a 1/2" thick corrugated plastic box finished with fiberglass. That really is not much insulation if at all. The pack is heated with two 10w electric heating pads each about 6" x 14". That's all it takes to maintain 41 deg. F. when it is well below 0. I would think you would want those batteries in battery boxes. Leaving them exposed just seems strange to me just off the pavement where they will be constantly exposed to dust, debris, rocks and water.

[gregmchugh]

The Advanced RV and Roadtrek heating pads are placed in between the lithium cells so they would be more efficient at getting heat to the cells than placing heating pads under the Stark battery modules. Roadtrek uses a little higher wattage heating pads per amp hour but with each 200 amp hours in its own module that may be reasonable, as I recall there are two 4 watt pads in each Ecotrek module, so 32 watts for 800 amp hours vs Advanced RVs 20 watts.

Are you willing to give up some ground clearance for the battery enclosure? Are the batteries already the low point?

[wincrasher]

The batteries are pretty high. Above the axle anyways. Certainly higher than the generator.

I was thinking of using 1/2" foam board covered with some kind of polystyrene sheeting. I'm not really concerned with loosing a 1/2 inch of clearance.

I'm not quite sure at this point that any heating is really even necessary - I'm not trying to design it to sit out in 5 degree weather. In such a small space, a 5 to 10 watt seat heater might do very well.

[gregmchugh]

As Davydd has said many times, if you have the batteries operating powering loads there will be internal heating that may not need much supplemental heat to keep things above freezing. Of course, when your thermostat turns on the heating pads the batteries will heat up themselves somewhat from powering the pads. I think both the Advanced RV and Roadtrek systems keep the cell temperatures above 40 deg by using the heating pads when needed. You don't have a reading of actual cell temperature but for your setup I would not expect that to be a major issue.

[Reed]

Curious about the low mounted Stark batteries. They definitely do not take up internal space but are there problems on rough roads. We go to Yucatan and the topes (speed bumps) might remove them quickly. The installed Onan is fairly low as well and will have to be aware of its limitations on such roads.

We will be mounting two Manzanita Micro 180 amp-hr (12 V nominal) batteries next to tire under the bed of our just purchased 2002 Roadtrek 190. This puts them within two feet of the installed electronics box.

Certainly a lot more limitations on where to mount new electronics on a Class B than on a 34' 5th wheel!

Reed and Elaine

[Reed]

Am interested in what is the nomenclature for the heating pads and where they can be purchased. We have 4 x 180 amp-hr (12 V nominal set up as 180 amp-hr as 48 V battery suite) LFP in fifth wheel and will have 2 x 180 amp-hr (12 V nominal) in 2002 Roadtrek.
Reed and Elaine

[wincrasher]

I did get my lithium specific zamp solar controller installed. I did have a little difficulty with it as it didn't function exactly as described in the manual.

Wincrasher's Travels: Zamp Lithium Solar Controller

[Reed]

Davydd

What does your 800 amp-hrs of LFP weigh? I would think about 300 pounds. And where do you keep it. We shall be installing 360 Amp-hrs (12 V nominal) of LFP under bed. This will weigh about 130#. Preferred this location since it should be above freezing in winter and not that hot in summer ,
Reed and Elaine

[gregmchugh]

I am sure Davydd will tell you about the battery pack location. If he doesn't happen to know the weight, the 800 amp hours of battery cells would typically weigh about 220 lb.

[Davydd]

This has been covered in my Advancing Alvar thread. They are under the floor behind the rear axle in a sealed insulated box protected by plate steel and further protected by an 1/8 thick aluminum skid plate. Total associated weight is over 400 pounds.

Outside under the van is a better location than inside because the batteries will stay cooler in an unattended situation because the inside of an RV can become an oven if not kept temperature conditioned. Also my experience with li-ion batteries is their operating temperature is about 10-20 degrees higher than air temperature. Would you want that kind of "radiator" inside your living space?

On the opposite end of the temperature scale I learned from Advanced RV this week that if you leave li-ion batteries in cold storage in a disconnected condition they will freeze and permanently damage colder than minus 4 degrees F. So you do have to heat your batteries in cold storage at all times if you live in a climate that gets that cold. So it is not just a temperature problem to keep them above freezing for charging. In the winter I stay plugged in and maintain my batteries above 41F (5C) and on the road the same in boondocking situations as the batteries furnish power to the 12v heating pads and the alternator charges the batteries. That is why Roadtrek's two AGM backup batteries under the hood puzzles me.

Advanced RV has once again redesigned their li-ion battery packs probably based on what they have learned from mine. I had their first assembled pack based on the Elite Power Solutions GBS batteries. I'm 39,000 miles in just over a year giving them a workout from 0F to 96F on the road. BTW, I said batteries stay about 10-20 degrees warmer. The also have a time lag in temperature change so on that 96 degree desert temperature it dropped to about 55 overnight and when the air temperature hit 96 the batteries topped out at 88. I can constantly monitor each individual battery cell temperature.

[gregmchugh]

Davydd,

What redesign has ARV done on the battery system since your build?

I won't rehash the Roadtrek AGM issue but just so everyone knows, the aux AGM they typically use in an Ecotrek van is a single 12v AGM with maybe 100 amp hours capacity but on the Sprinter they may use larger ones with the space available under the hood in some cases.

[booster]

I think that what davydd has said about the storing disconnected at -4* is the first time we have ever heard that. If accurate, that would eliminate the possibility to put up the van for the winter on a storage lot in many places. Very interesting.

[gregmchugh]

Victron shows storage down to -40 deg C, very interesting...

https://www.victronenergy.com/upload...tteries-EN.pdf

[avanti]

Originally Posted by booster

I think that what davydd has said about the storing disconnected at -4* is the first time we have ever heard that. If accurate, that would eliminate the possibility to put up the van for the winter on a storage lot in many places. Very interesting.

I was thinking exactly the same thing. That would be a HUGE disadvantage of Li. I would be very interested in a published source of this claim.

[gregmchugh]

Originally Posted by avanti

I was thinking exactly the same thing. That would be a HUGE disadvantage of Li. I would be very interested in a published source of this claim.

Stark shows operating range down to -30 deg C, the specs are all over the place...

[wincrasher]

Well, I've had regular lead-acids and AGM batteries destroyed in a Pennsylvannia winter where it gets down in the -10 to -20 range over nite a few nights a year.

I don't see why all the fuss over freezing Li's. You spend alot of money on a rig with a huge battery pack. It will require a certain amount of care and a proper storage environment. In my view, if you can afford a $180k-230K Class B, then you can afford a proper place to winter store it with either heat or an electrical outlet to keep the battery pack above freezing.

If you are using the van, all these problems fall away with the on-board heating and monitoring systems. Keeping the packs warm is not very many amps.

[avanti]

Originally Posted by wincrasher

Well, I've had regular lead-acids and AGM batteries destroyed in a Pennsylvannia winter where it gets down in the -10 to -20 range over nite a few nights a year.

As I understand it, this will only happen at those temperatures if the battery is not fully-charged. Modest solar can ensure this, even in the winter.

I do not agree that the market will find the requirement for constant heat or power in a shut-down RV to be reasonable. We'll see...

[Reed]

LFP can supposedly discharge at -25 F or lower. They should not charge (at least at not high C rate) below 32 F.

I estimated 300# for 800 amp-hrs (12 V nominal) since our 720 amp-hr (12 V nominal) Manzanitas weigh about 254#. This is four x 180 amp-hrs battery boxes (It should be noted that the Manzanitas came in aluminum and polycarbonate cases.

Still prefer interior to exterior location for LFP due to possibility of road damage and removal by topes (speed bumps) in Mexico. The topes in Tulum are like WW II tank traps. The bigger ones were very banged up from the undercarriages of low slung vehicles making contact. Counted 25 topes in the small town of Bacalar. We do plan to put a 12 V fan under the bed for heat transfer.

Chris Dunphy in Technomadia wrote candidly about the mistakes he made with LFP. One mistake is that the battery suite and inverter were in the same enclosed compartment. They were parked on tarmac at an RV repair facility in Phoenix in summer. The temperatures in that compartment could have gotten extremely hot.

Reed and Elaine