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Partially Covered Solar Panel


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#1 Cpt Davenport

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Posted 21 August 2022 - 04:13 PM

I have been doing quite a bit of camping with my new Hawk. Everything has been working great! My only issue is that when I put something on my roof racks it covers 1/2 of my solar panel. this brings my input down to 0-4watts. 

 

My set up is:

 

175w panel on roof

130w aux panel when at camp

Victron MPPT CC

100ah lithium

 

Because of all the information I have gathered here, I disconnected my alternator from the camper battery so solar is my only source for charging. I know the best solution is to upgrade wire from truck to camper and install a DC/DC unit. 

 

My consumption has been very low and I'm not using a lot of battery (maybe 20% at most). Even on cloudy days my solar (when not covered with surfboard) is keeping up fine. 

 

Question:

On trips when I have something on roof racks and panel input is diminished, can I simply hook my alternator back up to camper for the drive? I know by the math, and wire size this is not optimal, but some power coming to battery from alternator is better than none right?

 

I have read a lot of information on this and that "could" happen. Has anyone tried this first hand, and have any concrete results?


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#2 Vic Harder

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Posted 21 August 2022 - 06:06 PM

Sure you can. You can even monitor how effective it is before you commit by peeking at your BMV to see if there is much if any current flowing at idle.
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#3 Cpt Davenport

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Posted 21 August 2022 - 06:22 PM

Thanks Vic. Will any damage be caused to the under sized wiring or the battery?
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#4 ckent323

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Posted 21 August 2022 - 07:16 PM

If the wiring from the truck to the camper house battery is too small it will result in a very slow charge and may get hot enough to damage the wire.  The wires should be protected with a fuse on both ends.  The battery is not at risk, it does not care where or what the charging source is as long as it is providing what it needs in terms of voltage even if the current flow is small.  

Caveat:

 

However, if the truck to camper wiring is too small the resistance of the wire can result in a voltage drop and your house battery bank may not get the voltage it needs to charge properly.  If you have a lithium battery it may even cause the Battery Management System (BMS) to shut down which can lead to other problems and even damage (to other devices not the battery).

From your earlier posts I recall that you have 10 ga factory wiring and an running from the truck to the camper.  You have an ACR and as I recall a 150 A variable control alternator.

I think you had an AGM house battery but were planning to put in Lithium.  I don't recall if you said you put in a lithium house battery bank or if it is (still) AGM.

If AGM in both truck and camper it is my opinion you are OK without a DC-DC charger.   The wires to the camper should be fused at the truck end close to the battery and at the camper end close to the battery.

From my reading at a number of sites on having AGM starting batteries and Lithium house batteries it is my understanding that If the house battery is Lithium and you do not have a DC - DC charger then you may put your truck (or RV or boat) electronics at risk if/when the Lithium BMS senses low or high voltage or something and shuts off causing a load dump. If the alternator suddenly gets disconnected from the battery, the alternator has no route to deliver it’s current. If the alternator has no other way to deliver it’s current, the load dump may burn out the alternator diodes and damage the alternator. 

 
 
If the loads are still connected, there is also a risk of these loads getting the load dump with extremely high voltage levels damaging all the loads from a high voltage spike from the alternator.
 

 

I hope this is helpful,

 

Craig
 

 

This video (for a boat but almost identical to a camper install) may help


Edited by ckent323, 21 August 2022 - 07:25 PM.

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#5 Cpt Davenport

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Posted 21 August 2022 - 08:00 PM

Thanks Craig, your info is always helpful but this info is freaking me out on damaging something. Yikes!


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