Questions regarding "So, you want to setup a good electrical system in your camper?"

[Wallowa]

Yes...4 gauge wire is in the build....not certain which DC/DC is in the mix....whichever, KP has it "wired"... ...sorry could not help myself.

Vic and Jack thanks yet again...still fuzzy on the need for 40 volts [series] in my case if the Victron controller only 'needs' 5 V over battery 12V [Victron manual]...that the Victron controller modulates both the voltage and amperage to deliver the optimal watts into the battery is reassuring..

Also, from what I read the speed of charge is important on Li batteries longevity; I am assuming the Victron not only regulates for optimal watt input but speed of that input into the Li batteries...correct?

Phil

 

[Wallowa]

Wallowa, my appt is April 19.

Would appreciate a full report with details of the installation...thanks....

Phil

 

[rando]

The short answer: if your panels are the same type/brand (or same wattage and very similar Vmax), connect in series up to what your MPPT controller can handle. I have four 100W 19Vmax panels - 76V - on my 100/30 Vic, which can handle up to 100V input. Some controllers are limited to 30V or 50V.

Your panel voltage will vary by about 2V to 4V depending on how much sun and how much current you are asking the panel to supply.

The higher voltage from two panels in series does not pull more current out of the panels - but the higher voltage (38V instead of 19V - it varies by a few volts) means that the voltage is always more than 5V above your battery voltage and the MPPT controller will always be adjusting the voltage (up and down) to get the most watts (current X voltage). The MPPT controller actually sets the output voltage of the panels to get the maximum watts.

You can see this with your AGM batteries. Charged and with almost no load, they should be about 12.6V. Now add load by turning on the overhead fan and the furnace (about 7A) and watch the battery voltage drop. The amount of current drawn out of the batteries changes the battery voltage. The MPPT, by controlling the current drawn out of the panels changes the panel voltage. What's different about solar panels is that the change is non linear. Lets say, for the same amount of sun, your two panels in series are producing 40V at 5A. That's 200W charging your battery at 14V X 14.29A. (The MPPT takes in whatever voltage and current the panels supply and outputs what is needed for the battery.) But if the MPPT finds (generally by trial and error with small changes) that if it lets 5.4A flow from your panel, the panel voltage will drop to 39V. 39V X 5.4A is 210.6W. Your MPPT just got you an additional 10.6W so your battery will now charge a bit faster at 14V and 15.04A. As the amount of energy from the sun coming into your panels changes, this sweet spot changes. Your MPPT is always hunting for it when the panel voltage is 5V more than what is needed to charge the battery or meet your load.

This is a good explanation, but it would be good to clarify on battery voltage + 5V point. The requirement that the panel voltage be 5V above the battery voltage is somewhat artificially implemented by Victron and only applies at sunrise - once the MPPT is active it may track panel voltages below Vbattery + 5V. The reason it is done this way is that there is almost no power available from a solar panel when the open circuit voltage is below 17V. If the controller tries to load the panel down the voltage will immediately drop below the battery voltage and the MPP search will fail, wasting power. Solar panels are current sources, not voltages sources (which is a hard thing to wrap your head around), and as a result the Voc will rise with very little illumination, and is almost constant, it is the current that increases with increasing sunlight:

As a result, there is actually very little power to be gained by putting the panels in series from the Vbat + 5V limit. There are two other advantages to series panels, you can use smaller wires to the panels as the current is lower, and you can safely 'over panel' your controller - that is you can put more watts of solar panel than your controller is rated for based on the assumption that the panels will almost never put out their rated power in real world situations (unless you live at high altitude near the equator). The disadvantage is that it makes it much harder to add a portable panel to your system, and it is harder to mix different sized panels in series.

 

[Wallowa]

Rando,

Thanks! That explanation of voltage vs amp flow with illumination really helped me bring all this into focus. I suspected that voltage was more or less a constant and that amps increased with solar input.

I thought the Vbat +5V was not a voltage limiter but an optimal or minimal voltage target...

All things considered, with my system, 170/160W Zamps and changing to a Victron MPPT from the Zamp controller with BB 100AH....will the net watts into my batteries increase, stay the same or decrease by switching from parallel to series? Do not want to chase my tail, but do want to grasp the parameters in play.

Thanks...Phil

 

[rando]

Under most situations the net watt-hours will be essentially the same (to within a few %) between series and parallel.

If you plan on running a portable panel in addition to your roof mount panel and don't want to use a separate controller - then you need to wire in parallel.

If your roof panels have different wattages then you should wire in parallel.

If your panel wattage is higher than what your charge controller is rated for, then you should wire in series.

If none of these apply then you can wire either way, but I would probably go with parallel - it is easier to understand and troubleshoot.

 

[Wallowa]

Rando,

#1 Differing size [W] panels: Mine are 170 & 160W = 10W difference... a significant factor?

#2 Portable 80W Zamp that plugs into back of Hawk....only used once and with little success..no big deal to not have available.

#3 Installing Victron 100/30 which I assume is good for 3K Watts...my panels [series] 40V x 20A = 800W...good to go.

#4 But if as you say: "Under most situations the net watt-hours will be essentially the same (to within a few %) between series and parallel."; why go MPPT and in series if you really do not gain watts? Or will the MPPT gain me watts independent of whether the panels are in series or parallel.

What am I missing?

Phil

 

[rando]

#1 - not a big deal either way (5%). It depends if the Imp or Vmp are closer to each other to figure out which way would work better.
#2 - if you go series you will not be able to use this without adding its own charge controller.
#3 - not it is not good for 3000W, it is good for up to 30A at battery voltage, so around 400W (30A * 13V).
#4 - MPPT gets you more power than PWM regardless of series/parallel panels. This has been explained many times. There are reasons to go series as explained previously. You have to decide which option works better for you.

 

[Wallowa]

#1 - not a big deal either way (5%). It depends if the Imp or Vmp are closer to each other to figure out which way would work better.
#2 - if you go series you will not be able to use this without adding its own charge controller.
#3 - not it is not good for 3000W, it is good for up to 30A at battery voltage, so around 400W (30A * 13V).
#4 - MPPT gets you more power than PWM regardless of series/parallel panels. This has been explained many times. There are reasons to go series as explained previously. You have to decide which option works better for you.

Thanks....appreciate the education.

Phil

 

[Wallowa]

Follow up...KP @ SixGun12volts is not going to change the parallel connection between my 160/170W panels to series. I guess since I am going to MPPT and the wattage difference . The panels will remain in parallel.

 

[Jon R]

How are you guys getting #4 wire into an Orion-Tr Smart 12/12-30 Dc/Dc charger ?
Try as I might, a number of strands are not making it into the opening.
#6 fits fine, but..

I am going to run #4 from the truck battery to the Anderson Connector, but what gauge from the Connector to the charger and what gauge from the charger to the battery ?
Charger will be close to the BB LiFePO4, but wire garage is important, so do I worry about a few strands of #4, or use #6 ?

Thanks,
Fred
A.Smith

The specs for the Orion 12/12-30 say the maximum wire size that the terminals can take is 6AWG.

 

[Jon R]

A few centimeters of #6 AWG wire is no issue at all, your wire is already oversized for the job, and you don't care about voltage drop anyway as you have a DC-DC charger.

This is not at all a problem in your system as your wire is all more than sufficient, but in general it is more important that the wires between the DC-DC charger and the battery are fat (and short), as opposed to the wires between the truck and the DC-DC charger. The charger will compensate for voltage drop on the wires to the truck, but not between the charger and battery.

I've ordered a Victron Orion-Tr 12/12-30 isolated DC to DC charger. The wire run from the engine compartment to the charger in the battery compartment will be about 26 feet. The truck is a 2021, so I assume it has a smart alternator. The truck hasn't arrived yet so I can't measure the alternator output. I was planning to use Ancor Type 3 marine tinned copper 6AWG wire for that 26 foot run. While that wire size is certainly adequate for the current the Orion will draw, I'm hoping that size wire will limit the voltage drop sufficiently to allow the engine running detection logic of the Orion to work properly without using a dedicated wire to provide an engine running signal. Can anyone tell me from experience whether 6AWG will be sufficient for that? Thanks

 

[Vic Harder]

Using this DC voltage drop calculator - Voltage Drop Calculator (rapidtables.com) I suspect you will see about a 0.7V drop feeding 35A into that Victron using 6AWG wire, or around 5%. Without the DC2DC, you would want to aim at 3% or less. With it, it really doesn't matter if the wire can handle the current, which it can.

 

[rando]

I've ordered a Victron Orion-Tr 12/12-30 isolated DC to DC charger. The wire run from the engine compartment to the charger in the battery compartment will be about 26 feet. The truck is a 2021, so I assume it has a smart alternator. The truck hasn't arrived yet so I can't measure the alternator output. I was planning to use Ancor Type 3 marine tinned copper 6AWG wire for that 26 foot run. While that wire size is certainly adequate for the current the Orion will draw, I'm hoping that size wire will limit the voltage drop sufficiently to allow the engine running detection logic of the Orion to work properly without using a dedicated wire to provide an engine running signal. Can anyone tell me from experience whether 6AWG will be sufficient for that? Thanks

Full disclosure, I don't have an Orion-Tr. However, looking at demo on the Victron connect app, you can adjust the engine running detect parameters to work with the voltage drop in your cables, unless your alternator output is REALLY low.

 

[Ruck_and_Roll]

I have the 6awg and the last time I checked I was getting about 25amps. Was good enough for me.

 

[CatButt]

Slightly confused on adding a portable to a series wired roof configuration. If all the panels are running via the controller why is a portable a no go here? Isn't just additional current into the controller?

 

[Jon R]

Full disclosure, I don't have an Orion-Tr. However, looking at demo on the Victron connect app, you can adjust the engine running detect parameters to work with the voltage drop in your cables, unless your alternator output is REALLY low.

Agreed, the engine running detection parameter can be adjusted, but you can't set the engine running detection voltage to be lower than the voltage at the Orion from the truck battery when the truck is shut down and the Orion is drawing no current. Otherwise the Orion will cycle on and off while the truck is off. So you need the voltage at the Orion with engine running and the Orion drawing 35 amps to be high enough above the voltage at the Orion with the truck shut down so that the engine running detection voltage can be set between the shutdown no-current voltage at the Orion and the voltage at the Orion when drawing 35 amps with the engine running. Otherwise you need a dedicated engine running detection wire to the Orion.

The cable resistance data can be used to estimate the voltage drop (as Vic did), but the connections probably add some resistance as well. Based on Vic's figures and similar calculations using the data provided for that specific wire I'm probably good with the 6AWG for the entire run. However, I was hoping for someone to be able to tell me they have a similar setup and confirm it works without the engine running detection wire. Thanks for the helpful responses.

 

[rando]

Slightly confused on adding a portable to a series wired roof configuration. If all the panels are running via the controller why is a portable a no go here? Isn't just additional current into the controller?

If your existing panels are in series, that would mean that a portable would need to be put in series with the roof panels. To do that, you need to disconnect the wiring to the roof panels and connect the portable into the circuit, and the reverse to disconnect the portable panel. Furthermore, all the current from all your panels would be running through the wiring to your portable panel.

So yes it *could* be done, but practically it would be much easier to either run everything in parallel or run a separate charge controller for your portable.

 

[rando]

Agreed, the engine running detection parameter can be adjusted, but you can't set the engine running detection voltage to be lower than the voltage at the Orion from the truck battery when the truck is shut down and the Orion is drawing no current. Otherwise the Orion will cycle on and off while the truck is off. So you need the voltage at the Orion with engine running and the Orion drawing 35 amps to be high enough above the voltage at the Orion with the truck shut down so that the engine running detection voltage can be set between the shutdown no-current voltage at the Orion and the voltage at the Orion when drawing 35 amps with the engine running. Otherwise you need a dedicated engine running detection wire to the Orion.

The cable resistance data can be used to estimate the voltage drop (as Vic did), but the connections probably add some resistance as well. Based on Vic's figures and similar calculations using the data provided for that specific wire I'm probably good with the 6AWG for the entire run. However, I was hoping for someone to be able to tell me they have a similar setup and confirm it works without the engine running detection wire. Thanks for the helpful responses.

My understanding is that Victron thought of this situation and have this engine running detection algorithm where they periodically briefly pause the charging (which removes the voltage drop) and see if the resting voltage is above the turn on threshold.

 

[Jack]

I've ordered a Victron Orion-Tr 12/12-30 isolated DC to DC charger. The wire run from the engine compartment to the charger in the battery compartment will be about 26 feet. The truck is a 2021, so I assume it has a smart alternator. The truck hasn't arrived yet so I can't measure the alternator output. I was planning to use Ancor Type 3 marine tinned copper 6AWG wire for that 26 foot run. While that wire size is certainly adequate for the current the Orion will draw, I'm hoping that size wire will limit the voltage drop sufficiently to allow the engine running detection logic of the Orion to work properly without using a dedicated wire to provide an engine running signal. Can anyone tell me from experience whether 6AWG will be sufficient for that? Thanks

I had cycling problems with the stock 10 AWG and the Vic DC-DC. Replaced it with 25' of 8 AWG braided speaker wire direct from truck to the DC-DC (with two 50A thermal breakers and an Anderson connector inline) and it works just fine. 6 AWG should give you plenty of margin.

 

[Tom S]

Help!!!
I just put the camper on and ran the heater all night. It worked great, 25 ah consumed in 14 hours. So 80% remaining. I started the truck and went for a drive. Sure enough it said 78% remaining. Huh? Looking at the monitor with the truck running I am showing negative amps at 14.8 volts. I checked the polarity and it is correct. There is continuity from the the breaker in the engine compartment to the input terminal on the dc2dc charger. Input voltage at the charger is 13.6 compared to 13.7 at the truck battery so that seems correct. Output from the dc2dc charger is 14.8 volts. I checked the shunt and it is wired correctly and I show a positive charge with both solar and shore power. The alternator light comes on on the charger as it should. I just can’t figure out why I get a negative reading on alternator. The battery voltage on the truck doesn’t change so it’s not seeing the 14.8 volts from the charger so the isolation seems to be working.
I have not connected the ignition sensor as I didn’t think this was necessary as I didn’t think my 2015 Tacoma alternator was “smart”. I’m thinking that could be it?
But it also could be that the dc2dc is defective. And also it could be that I’m just not getting the reading correctly on my monitor but I think the odds of this are slim as it is reading correctly in all other modes.
So any ideas? I’m going to read up on the ignition sensor and try a quick and dirty jumper to see if it comes on line. Cheers and thanks in advance.