Solar charging the starter battery

[john61ct]

Or in my case, get a bigger truck.

 

[vomhorizon]

on fixed installs I still put anderson pigtail on the solar charger with locking retainer pins, just so I can unplug the panels and work on the solar charger or any wiring downstream without some hot wires dangling about, nobody likes to jam raw copper into something and have a spark either.. but thats just me, I gotta tiny lil compartment to work on electrical in, dont wanna be balls deep in there and have a blanket blow off the roof.

So would it be ok to simply disconnect the anderson plug connecting the PV to the MPPT? My victron MPPT has an ability to disconnect charging from the app, I guess doing that first would be logical? Or is it ok to just pop off the anderson plug connecting a 100 Watt pannel to the MPPT w/o the fear of it arcing out?

 

[dreadlocks]

yeah, that's perfectly fine.. the safest way to disconnect solar is panel first then the controller, if you drop all the loads off the controller first you could get a bad voltage spike.

 

[vomhorizon]

yeah, that's perfectly fine.. the safest way to disconnect solar is panel first then the controller, if you drop all the loads off the controller first you could get a bad voltage spike.

When you mean panel first do you mean disconnect the PV from the MPPT or the panel side connectors? So here's my situation, My MPPT lives inside the LiFePO4 battery box that I'm building, and the PV will connect to it via an Anderson connector. I don't want the PV to be connected to my portable battery all the time. When the box is sitting in the rig, I can simply disengage solar charging from the Victron app and keep them plugged in. When I'm using the portable box outside the rig, would I just connect and disconnect the 100 watt panel as needed? Will sitting disconnected on my vehicles roof for long periods of time (like possibly the entire winter) be a problem for the PV? In case it isn't wise to just leave it disconnected for long periods, I may just ditch a mounted panel and go with something portable but my preference would be to mount something to the roof and not have to worry about space in the rig.

 

[dreadlocks]

not really.. toss one of those rubber dust boots on the Anderson and perhaps some dielectric grease to keep those hot wires from corroding.

 

[vomhorizon]

not really.. toss one of those rubber dust boots on the Anderson and perhaps some dielectric grease to keep those hot wires from corroding.

Perfect! From an electrical perspective, do these PV continue to generate power even when not wired up? As in will the wires be constantly hot even when I'm not connected to the MPPT? I'm just wondering whether that is safe and something that folks do routinely.

 

[dreadlocks]

yep, its like a battery.. treat it always hot, but you can throw a big blanket over it when you go to crimp the terminals so any output if any would be negligible.

it always being hot is what will cause accelerated corrosion on the andersons.

 

[Gooseberry]

I just have a pwm with the same connectors that I have on one of my panels and I plug it to the tender plug when needed.


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[vomhorizon]

Thanks guys! I might just buy an affordable charge controller and use it to charge my starter battery when the aux battery box is not in the rig. At least I'm using the PV at that point to trickle charge my starter AGM.

 

[john61ct]

SCs with a built-in off switch do not need to be physically disconnected from panels before the bank.

 

[vomhorizon]

SCs with a built-in off switch do not need to be physically disconnected from panels before the bank.

Right, and I guess that applies to those that can have charging turned off via the app as well. My intention here though would be to remove the aux battery box from the vehicle and leave the panels permanently mounted.

 

[john61ct]

Yes, applies to do doing any maintenance requiring disconnecting the SC from the bank

 

[vomhorizon]

Yes that is a good example. However in my case the disconnect could last weeks to months so I wasn't sure whether I'd have issues with a hot adaptor wire being present in my vehicle and any issues with it arcing given that the solar panels will be permanently mounted there. I'm considering a cheap PWM that I can use to just charge my starter battery in case the aux box is not in the vehicle (or in the winter when the Lithium battery will not be in the rig). At least that way the panels are being used to top of fthe AGM starter battery.

 

[john61ct]

You could end up overcharging your Starter, especially if Sealed type, dry out the electrolyte.

Why not just use an SC with an off switch?

Or just isolate the panel wires to insulated terminations

Apparently there is even no harm in shorting panels.

 

[vomhorizon]

Why not just use an SC with an off switch?

Th charge controller will live inside the portable unit (so that I can solar charge it with a foldable portable panel when I'm using it away from the vehicle) so even if I physically turn off charging via the MPPT (using the app) I would still have to disconnect the PV connection into the MPPT so the issue with leaving a hhot cable (terminating in an anderson connector) without a connection.

Or just isolate the panel wires to insulated terminations

Yeah that's an option since I could just cover the anderson connector with a rubber cover/boot that I already have and leave it tucked away in the vehicle.