Seeking Feedback on Solar Idea

[Casey Freswick]

Yes, I am still here. I did not connected the wire from my TV to my battery. I also normally just shut the breaker off for the converter. I charge my battery (batteries) with my vitron 30 amp solar controller. I have 3 100 watt solar panels on the back of the rear shell. If I have access and need shore power I will turn the circuit breaker on. I just added a 200 Amp battery to my 100 amp battery. So I now have 300 amp battery bank. I put the 200 amp battery in the storage compartment under the rear bed. This may be particularly beneficial if I am in a low temp situations where I can warm that battery up. I have shut off switches for both batteries. Here are pictures of my bus bars, one battery, solar controller and inverter.

[Kidkraz]

Casey, looks good, but are you planning to cover the bars? In my past aviation years, any buss bars had protective covers to prevent inadvertent shocks.
Otherwise well done.

[Casey Freswick]

I put the picture of wiring when uncovered, otherwise you would not be able to see the hookups. It is covered. I created a wood box that covered all the positive terminals as well tapeing the positive battery terminal and then putting a plastic cover over that. DID NOT leave any positive connection uncovered. In addition I only put water hoses and electric cords in storage compartment.

[rickst29]

Originally Posted by JohnMD

Rick,

Thanks for the additional information. I wasn't planning to run the solar and WFCO concurrently. I figured I would usually switch off the solar disconnect when on shore power. I was mostly trying to figure out if there would be an issue sending too many amps to the battery with the solar panels and tow vehicle charging at the same time. Also, I wasn't planning to add a dc-dc charger. I figured adding solar for charging while towing would help keep the fridge cool and also allow more charging when not on hookups at the campground.

You wrote: "When Solar "charging" is holdling the battery voltage high, you will NEVER get significant current from the truck." So, even without a dc-dc charger, you think this would be okay?

I want to reiterate how much I appreciate this forum and those of you who continue to post such great advice for everyone!

Thanks!

John

John, Solar is harmless while plugged in, and actual beneficial in most situations. The "battery management" scheme implemented in the WFCO power converters has evolved over time, but is generally very bad: They drop to "float" operation before the batteries are full, and won't recovery to "boost" operation until the battery voltage has been run down too far. (Lead acid batteries should be kept near 100% state-of-charge for as much time as possible, while not overcharging).

While the sun is shining and the panels provide sufficient power, a decent solar controller can be programmed to push the batteries up (and keep them near 100%) far better than the WFCO converter - which cannot be programmed (i.e,. "fixed") to do a good job of maintaing the batteries
- - -
Lithium batteries do not like to be stored at high voltage, but you have two ways to manage that voltage (which is HIGHER than the "12v"voltages used for lead acid battery management). You can modify your solar controller sesttings, if that is convenient, or you can modify the lithium battery "BMS" settings instead.

BMS = "battery management system", a small computer and power controller which protects the battery cells (in several different ways) and keeps their voltage values in balance when they become charged to high high voltage levels (e.g., more than 93% full). A "12v" Lithium battery contains 4 cells,
and must always be built with a BMS.

The best BMS units are programmable from cellphone apps using bluetooth, and the bluetooth signals easly go through the aluminum skin of the TM body panels layers of the and upper shells. The best way is to probably to set your solar controller output voltage at nearly 14 volts maximum and the "float" value nearly that high, while using lower BMS limits (13.300 to 13.600 volts in total, specified as per cell limits of 3.275 volts or 3.375 volts in "storage" to actually prevent unwanted excess power from reaching the cells.
- - -
Your total solar panel size will need to be at least "200 watts" to run the fridge(with 12 volt DC power) normal weather. (While actually driving the DC heater, the fridge uses about 140 watts. A pair of "100 watt" solar panels, mounted flat on the roof and perhaps experience some shade, with never make 200 watts - the angle into the sun is wrong. The sun also becomes weaker in late afternoon, and later moths of the camping season -such as August.)

In hot weather or August, you will need to install at least "300 watts" of panels to keep up with the fridge load.

Adding a DC-->DC charger for up to 15A through the bargeman (from the truck) can also help to run the fridge or charge the batteries, adding another 110-140 watts while cruising dow the road. But you must not exceed 15A maximum current on the bargman cable's "trailer battery charge" wire, because you will create too much risk of burning out the cable.

(The wire is usually very small, and the cable's heavy duty 'flexible outer shell' wrapping prevents generated heat from escaping easily. The connection from the small wire end to the all wire to the 7-pin connector plug is also prone to failure when run at high current for extended periods of time.)Solar

[rickst29]

Originally Posted by Kidkraz

Casey, looks good, but are you planning to cover the bars? In my past aviation years, any buss bars had protective covers to prevent inadvertent shocks.
Otherwise well done.

I strongly agree (with Kidkraz), with the "bus bars" must have protective insulation on all sides. But I see additional "issues" in these pictures:

1. The "bus bars" have insufficient cross-section to support the loads implied by the attached wire sizes (too thin, and they should probably have been coated anyway).
2. Although you may have considerable "trust" in the overall protection provided by the BMS units of these batteries packs, BMS units are TOO SLOW to protect from from sudden short circuit situations. You need to add a class-T "fast response" fuse to provide that protection. You can consider one fuse (maybe in the range 350A - 450A) for both batteries in parallel, or (better!) you can [protect each battery with its own fuse each matching the PEAK.output whi h I attach, for your reference a photo of a decent fuse and fuse holder, in which you might note the size of bus bars needed for a 300A connection: nearly 1" wide, 1/4" tall, pure OFC copper which has been COATED. This fuse holder is about 7" long, 2" wide, 2-1/4" tall. "bigger" one are even larger.
3. Your vast number of smaller wires, many "magically looping" to or from the WFCO fuse board out of sight and unlabeled, is confusing (and therefore dangerous). You should add an additional DC fuse board in this area, connecting all the "smaller" 12v wires on individual fuses, drawing power form the main bus through another (larger) fuse. This cheap Amazon one supports 100A max current, with either 6 or 12 downstream fuses and connectors: https://www.amazon.com/Circuit-Negat.../dp/B08XWQHMZJ

[Casey Freswick]

Casey: NOT well done (IMO), and I have additional issues as well.

Your vast number of smaller wires, many "magically looping" to or from the WFCO fuse board out of sight and unlabeled, is confusing (and therefore dangerous). You should add an additional DC fuse board in this area, connecting all the "smaller" 12v wires on individual fuses, drawing power form the main bus through another (larger) fuse. This cheap Amazon one supports 100A max current, with either 6 or 12 downstream fuses and connectors:

Rick and all,

If you are talking about some 12v wiring you can hardly see in the bottom right hand corner, that is the wiring that came with the TM and is already connected to the 12v fuse box of the TM. In the past I took the 120V 30 AMP shore extension cord out of the "box" that you pushed the cord into in the back compartment of the TM. I then removed the "box" that the original cord was pushed into. So you can see(barely) from the bottom right rear compartment the back of my new lithium converter and original 12 volt fuse box of the the TM. I then wired an outdoor outlet under the TM in the back that you can plug in when the shell is down. I now use this outside plug and a 30 AMP extension cord whenever I use shore power. Since I put in solar I do no longer often use shore power. Because I removed the 30 AMP extension cord from its original place, I used the hole for the original extension cord for my solar wiring. All this to explain the 12v wiring in the bottom right hand corner of my original picture. All the wires that you clearly see are 2/0 wires. Rick recommended 2 2/0 wires for all connections between my lithium batteries and inverter, both positive and negative. Hope this helps explain my 12v "wiring" situation.

Casey

[JohnMD]

Hi all,

The suggestions and feedback here gave me the confidence to do this install. I have two 175 watt panels connected in series to a Victron Smart Solar MPPT 100/50. However, I don't think it is working correctly and cannot figure out why. Attached is an image of what I see on the Victron Connect App.

It indicates voltage, but no current. The battery voltage shows 13.81 in this screenshot, but when measured with my multimeter at the battery terminals, it was reading 12.9. Yesterday, when I tried this, my battery was lower, around 12.5, and Victron app was reading over 13. Does the controller think the batter is fully charged when it is not and thus not sending a current? I've read different things online, but everything seems to be connected correctly.

Any thoughts are appreciated as I am not sure how to proceed.

John

[JohnMD]

Of, course, as my pattern goes...I spend a day trying to figure something out, post to the forum the next day, and then figure it out while waiting for a response!

So, I made MC4 connectors that I put between the charge controller and the battery to use as a quick disconnect, if wanted. For some reason, one or both of these MC4 connectors is the issue. I bypassed these connectors and now everything seems to be working fine.

John

[rickst29]

John, I'm glad to hear that you found (and fixed) that connector issue on the solar side.

However, Victron's measurement of the battery-side 'Voltage' is probably independent of whether the Solar is connected all. (In my cheaper EpEver controllers, that is definitely the case.) So I suspect your "battery voltage" is still showing a wrong value.

If your SCC will apply different current limits for "bulk/boost" versus "float" charging, then you need to re-calibrate that battery-side voltage value.

Just remember that if the batteries are also being discharged while the Victron "watches them", the voltage will be pulled down by the loads. Try to do that callibration with batteries "idle" and unaffected by either charge or discharge current (including charge current from main Converter Board, when plugged in).

[JohnMD]

Rick,

Yes, this all makes sense. The PV connections were fine, but the battery side connections were not. The battery voltage readings on the SCC are now exactly matching my multimeter. I am feeling really good about the setup for now.

Thanks!

John