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Old 07-08-2019, 03:19 PM   #1
Lordfamilybikevan
 
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Default Solar Design Question

I should have my own section of this forum where I just ask question after question. I will say, I am trying to find the answers using search before posting questions. Maybe someday they will be helpful to others.

For our solar system design I have the solar charger simply connected into our pos and neg buss bars. My question is, Should I have any concerns when I am not connected to the battery? For instance, I have placed an on/off switch between my whole aux system and our batteries so that I can access the batteries or work on the system with nothing live. If I am locked out from the battery bank should I be concerned about the solar charger feeding power to the system? I do have it on a blue sea breaker which can easily be tripped (on purpose). I also want to be able to just shut off the system when our van is parked, stored or not in use, limiting the small amp draws that will ultimately kill the batteries if left too long. Cheers for your thoughts!
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Old 07-08-2019, 04:07 PM   #2
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Default Re: Solar Design Question

Quote:
Originally Posted by Lordfamilybikevan View Post
I should have my own section of this forum where I just ask question after question. I will say, I am trying to find the answers using search before posting questions. Maybe someday they will be helpful to others.

For our solar system design I have the solar charger simply connected into our pos and neg buss bars. My question is, Should I have any concerns when I am not connected to the battery? For instance, I have placed an on/off switch between my whole aux system and our batteries so that I can access the batteries or work on the system with nothing live. If I am locked out from the battery bank should I be concerned about the solar charger feeding power to the system? I do have it on a blue sea breaker which can easily be tripped (on purpose). I also want to be able to just shut off the system when our van is parked, stored or not in use, limiting the small amp draws that will ultimately kill the batteries if left too long. Cheers for your thoughts!
It depends on where the loads are connected, if you disconnect the battery from the solar charger, you will likely see what is called a load dump. With the sudden loss of a load (the battery), the charger output voltage will rise rapidly for a short time at least, until it can bring the voltage down. Any load (inverter, lights, etc.) that is still connected to the charger side will see this high voltage. Depending on the solar charger, the voltage may be up to 20V or even more, and even though it probably is only for a fraction of a second, it may damage something. You should put the switch to disconnect the load from the battery, but leave the solar charger connected to the battery.

A breaker won't help you, it may take seconds to trip, way too late.

Note that some batteries with a BMS will do the same thing, open up when fully charged. I make sure to have a load on the system, even a small one, when solar charging so the charger will deliver something and avoid a load dump.

Regards,

Mark
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Old 07-08-2019, 04:23 PM   #3
Lordfamilybikevan
 
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Default Re: Solar Design Question

Thanks Mark. One of the reasons I'm connecting to the Buss is that the Buss is in the van and the batteries are in the engine compartment and an added bunch of work to run the wiring directly. (also feeling like the victron monitor noted not wanting any other "loads" on the battery for monitoring) Thinking in the case of the solar charger load dump I could add an on/off on the positive side of the solar charger and turn off before using main disconnect. My mention of the breaker was not for protection but also to use as an on/off. It is one of the blue sea ones where you can press the red button to break the circuit. Cheers.
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Old 07-08-2019, 04:44 PM   #4
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Default Re: Solar Design Question

When disabling solar, always open path between panels and charge controller first.
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Old 07-08-2019, 04:50 PM   #5
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Default Re: Solar Design Question

calbiker, thx. So I'm guessing if I just disable the panel to the charger that should deal with any load dump from charge controller? Any recommendations on an inline switch for something like this? Ideally I would like to put it in the panel right next to my charge controller. Switch off solar power, turn off main to batteries, all good.
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Old 07-08-2019, 05:14 PM   #6
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Default Re: Solar Design Question

Any normal 15 A toggle switch will work fine.
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Old 07-08-2019, 05:25 PM   #7
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Default Re: Solar Design Question

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Originally Posted by Midwestdrifter View Post
Any normal 15 A toggle switch will work fine.
Not on my setup! I have a 30 A charger and 400+W of panels. You need a switch rated for the max current of the panels. I don't know what the original poster has, maybe it was posted before that I didn't see.

Regards,

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Old 07-08-2019, 05:29 PM   #8
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Default Re: Solar Design Question

Quote:
Originally Posted by marklg View Post
Not on my setup! I have a 30 A charger and 400+W of panels. You need a switch rated for the max current of the panels. I don't know what the original poster has, maybe it was posted before that I didn't see.

Regards,

Mark
I have 600 watts of PV and use a single 7.5A switch/breaker.....

Last edited by OrioN; 07-08-2019 at 05:32 PM.
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Old 07-08-2019, 05:57 PM   #9
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Default Re: Solar Design Question

I currently only have one 100w panel. Hoping to add another this year. Currently have a 15A inline fuse between panels and solar charger.
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Old 07-08-2019, 06:05 PM   #10
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Default Re: Solar Design Question

I use a fuse block as my disconnects surrounding the solar controller.

When i'm going to work on the system, i simply pull the fuses in the controller's documented order: loads, panels, battery.
Reconnecting is the reverse: battery, panels, loads.

If i feel like being really careful (or it's a bright sunny day), i'll throw a blanket over the panels first.

--dick
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