4 panels, 490 rated watts on front shell. (a 2619)

[rickst29]

I am awaiting a few MC-4 connectors, which will allow me to shorten some over-long connecting wires which you see in the photo.

One panel is slightly larger and more powerful, with about the same amperage as small ones - but slightly higher voltage. The small ones are all "cheap 120W, 21 Volt" flex panels which I discussed in another Thread. They are all wired in series - constant current of the worst-performing panel, but with all the voltages added together. I suspect that the rated specifications are fake, and the panels are really about 100 watts each. They are configured as 9x4 cells, which is typical for 100 watt panels.

My MPPT charge controller can handle 150V of panel voltage. 23.0 Volts * 3 panels, plus 24.2 Volts * 1 panel = 93.2 Volts during "PWM Mode" disconnects. I would not !!! try this configuration with a charge controller of only 100V Solar Array Maximum Voltage, and it would instantly blow up some very small controllers (with Maximum Array Voltage of only 40-60 Volts). Those controllers would need panels wired in Parallel, so that Voltage would be constant (the lowest-voltage panel), and current would be added together from each panel.

The reason for "needing" 430 watts is not to actually get 430 Watts on a cloudless day in late June. Rather, it is camping in late Season (September, or even October), when the sun is at a much lower angle. And even in June, mounting panels flat on the roof does not match the angle of sunlight inclination.

On a perfect day in June, your Solar Controller also needs a good capacity to reject power which it does not want to "accept" for charging batteries and running instantaneous 12V loads. My somewhat small Controller (30A) is rated to handle attachment of 720 watts of maximum Solar power, even though it cannot use more than about 460 Watts maximum. (30A * 14.5V into the batteries, with 5% input power lost in the conversion. My batteries accept high charging voltages through the entire charging process).
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From the front shell roof, 10 AWG Solar Wire runs down the rear street-side lift arm for that shell, and then follows the frame towards the front of the TM, and inside the front-most frame crossbar (within the TM "box", not the towing A-frame). My Solar controller is mounted on the inside front wall, directly under the table (which I can no longer fold closed). From there, battery connections run sideways along the front and into my battery storage area - under the curb-side bench.

My batteries are LiFePO4, too valuable to leave out on the tongue. And they don't "like" cold weather, so I have put them into the interior storage box. (As far from the heater as possible.) When I had lead acid batteries, the battery wires simply went back out the front lower wall and into a tongue-mounted battery box. After drilling holes and pulling 3 wires (12V+ , Grounding Neutral, and Battery Temp Sensor), I filled the gaps and sealed the wires in place with 3M 4200 Boat Sealant.
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In theory, if I abandoned the larger panel, I could place a total of 5 smaller panels on the front shell. (4 across, plus the rear side.) But I'm not inclined to do that yet, because the current layout has been sufficient to meet my needs.

[tentcamper]

Now that's what you call putting up a solar system.

[FlyboyTR]

Rick,
I do enjoy reading about your solar info. Always insightful. Thanks!

Travis

[simonen]

Originally Posted by rickst29

My batteries are LiFePO4, too valuable to leave out on the tongue. And they don't "like" cold weather, so I have put them into the interior storage box. (As far from the heater as possible.)

*A bit off topic.*

I am in the process of building my own LiFePO4 batteries from 200Ah prismatic cells and BMS. I have a fair amount of experience building ebike batteries from 18650 cells, so this is much easier to do.

Anyways, after looking at your signature, I noticed you upgraded your converter and installed an inverter. Could you tell me why you opted for that as opposed to an inverter/charger/transfer switch combo unit?

Currently, I am in the design phase, but I am leaning towards a combo unit and ripping out the stock converter. Ideally, I would like to use the existing battery box area to house the inverter charger, MPPT controller and DC-DC charger from TV (batteries in storage by heater). Downside is wire length to the battery, and I need to build a vented box. Other option is to put everything in the storage compartment by the heater (not so sure it would all fit anyways); downside there is I lose storage and need an active venting/cooling system.

I am sure there are other things I have not thought of yet.

[Peterbug]

I was under the impression that LiFePo batteries do not require ventilation. Any reference material that specifically mentions this?

[simonen]

No, the batteries don't...in my case, the electronic do to prevent overheating.

[rickst29]

Originally Posted by Peterbug

I was under the impression that LiFePo4 batteries do not require ventilation. Any reference material that specifically mentions this?

No venting for the batteries. But I also provided venting, for the big Inverter which is in the same under-seat storage compartment as the batteries.

[rickst29]

Originally Posted by simonen

*A bit off topic.*

I am in the process of building my own LiFePO4 batteries from 200Ah prismatic cells and BMS. I have a fair amount of experience building ebike batteries from 18650 cells, so this is much easier to do.

Anyways, after looking at your signature, I noticed you upgraded your converter and installed an inverter. Could you tell me why you opted for that as opposed to an inverter/charger/transfer switch combo unit? (....)

Yes, I had a couple of reasons to avoid an otherwise-really-great Victron All-in-One. First: I have only the 2619, with no rear storage for batteries and large electrical equipment. (Inverter or MPPT Controller). Second: I already had my MPPT Solar mount, and Solar wires, running up and into my 'front of the lower box' MPPT installation. (From many, many years ago, I had a "big iron" MMPT, with humongous inductors and far less electronics than modern designs, in that same place.)

By leaving the AC Converter and MPPT separate, I was able to put the 4600 "WFCO upgrade" converter section into the existing space, underneath the bathtub ledge, and without active cooling. My fancy MPPT "charge from the TV" tricks also remain as they were and independent of the Converter.

[lederhos]

Originally Posted by rickst29

Yes, I had a couple of reasons to avoid an otherwise-really-great Victron All-in-One.

I too like the Victron All-in-one option and may decide to go that route when it comes time to move to LiFePO4. Automating power source regulation while deliver 120 to all outlets is enticing.