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Prevent the damage on the solar charge Controller

V

Vikingen

New Member
Joined
Dec 2, 2019
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3
Hey all

I´m building my first solar setup, but encountered a problem:

If the solar charge controller is connected to the solar panels, but not the battery.
Then the charge controller will take damage!!!

But if the fuse between the battery and the charge controller blows, the battery becomes disconnected and the controller will take damage!!!

How do I fix the problem?
 
  1. If you blow a 150 or 300 amp fuse there may be more pressing concerns than the SSC.
  2. Power a relay from the fused supply that will interrupt the panel circuit on loss of power.
  3. Choose a SCC that handles that type of event.
 
I'm interested this too. In my situation bypassing the battery bms and connecting directly to the battery pack is not an option. I have several different batteries and I swap them out so I'd like to be able to remove a battery without the solar controller getting fried. Is there a type of relay that I can install that would take 48 from the battery to close the solar circuit? That way Whenever the battery get's removed the solar circuit is automatically opened preventing damage?
 
I wouldn't loose any sleep over it. This is a very common occurrence and I have done it many times. It would be a very poor designer who built a system that would do this. There is a little bit of truth in it. If marginal voltage FET are used and the panels are at the high end of input range it can be an issue. Note that many data sheets raise the maximum input voltage as battery voltage increases. Figure maximum safe input panel voltage for 12V battery.
 
I'm wrestling with a similar problem in regards to cutoff and how to handle it properly. At least with my Solar Controller (MidNite Classic-200), I can program it's charging profile so put the bulk charge rate where It has to be float & equalize lower so there is still output but not charging the battery... keeping in mind also that there is an inverter that is drawing power at all times, so the extra will be bled off anyways. The low voltage cutoff to the inverter can be handled by a Relay (I chose to go with a Chargery BMS8T) which is easy enough in general.

I do have a twist, is there is also my backup FLA battery bank so that adds an extra complication. I can leave my Samlex Inverter/Charger programmed to charge the FLA bank using the Genset for the occasional times it would need a top up but then I could not leave that to charge the LFP pack in case, without a re-programming. Luckily I can save settings profiles to load on the Samlex SDHC card. The LFP Pack and FLA Bank won't be connected on a bus, they will be manually switched using a BlueSea e-Series 4 Pos switch as needed.
 
Hey there

I like the relay idear, that will interrupt the panel circuit on loss of power form the fuse between the charge controller and the battery.

Having a hard time to find one the right one!

You guys know of anye?


(sorry if my english is bad)

Best regards
 
David "Daud" Tashnick said:
I'm interested this too. In my situation bypassing the battery bms and connecting directly to the battery pack is not an option. I have several different batteries and I swap them out so I'd like to be able to remove a battery without the solar controller getting fried. Is there a type of relay that I can install that would take 48 from the battery to close the solar circuit? That way Whenever the battery get's removed the solar circuit is automatically opened preventing damage?
Click to expand...
If you are there swapping the battery packs then a simple 2 pole switch on the PV line or even one pole would be a way . Just turn off PV first then remove battery . Thats what I do.
You can have a relay inline to automate that but its just something else that might and will fail at some point.
 
Will has a solution with relays and links for where to buy them here:
www.mobile-solarpower.com

Design Your Own LiFePO4 Solar Power System

This is a complete system solution complete with: BMS Protection Features (over/under voltage/over-current/balancing) Low Temperature Cut-off Programmable Charge/Discharge Bandwidth Settings Matched...
www.mobile-solarpower.com

I have a solution I am trying to get feedback on that uses a relay as described on this thread to cutoff the solar array from the controller if BMS detects low cell voltage, high cell voltage and low temperature (LiFePO4 specific). My solution adds a second relay and a switch to Will's.

www.diysolarforum.com

BMS Array Cutoff and Bypass Switch

I could have added this to quite a few different threads but did not want to hijack anybody's thread. There have been a few conversations about disconnecting batteries from a SCC while the PV array is still hot/connected. There are several scenarios where a battery could be disconnected from a...
www.diysolarforum.com www.diysolarforum.com

I think such a solution without a BMS is possible too. I have heard of solutions with an NO relay. I wonder if one could use a NC relay that is held open while the system has power - on power loss, it closes (and cuts connection between array and controller for example).
 
MisterSandals said:
Will has a solution with relays and links for where to buy them here:
www.mobile-solarpower.com

Design Your Own LiFePO4 Solar Power System

This is a complete system solution complete with: BMS Protection Features (over/under voltage/over-current/balancing) Low Temperature Cut-off Programmable Charge/Discharge Bandwidth Settings Matched...
www.mobile-solarpower.com
Click to expand...
This relay is for the inverter...
This solution doesn't address disconnecting the panels from SSC in case the battery gets disconnected from the SSC to avoid damage to the SSC, What kind of relay should be used to disconnect the Panels from the SCC (an NO?) and how is it hooked up?
 
dpdoug said:
This solution doesn't address disconnecting the panels from SSC in case the battery gets disconnected from the SSC to avoid damage to the SSC, What kind of relay should be used to disconnect the Panels from the SCC (an NO?) and how is it hooked up?
Click to expand...
Funny you should ask EXACTLY that!

www.diysolarforum.com

Relays: NC vs NO or other solution?

I am hoping someone can help me find a solution. I am learning about relays and hoping to incorporate one to cut the power between my array and solar charge controller. 400w array, 45A SCC. My "thought" was to use an NO (normally open) relay but wondering how i would power a "close" in the...
www.diysolarforum.com www.diysolarforum.com
 
So I understand this right... If my solar charge controller is getting power from panels, and the fuse between the battery and the charge controller blows, the charge controller is fried?

Seems the options are to leave that wire unfused, use a relay to shut off Current from panels, or... Hope fuse never blows?

Edit:using renogy Rover 30a.
 
KISS. That fuse should never blow. If it does you've got bigger problems than worrying about the small chance the CC gets harmed.

If you were to hook up a NO relay, where would you connect the trigger wire to the relay to hold it closed? If on the battery side of the fuse, the relay would never open because it still sees battery voltage. If on the CC side of the fuse, the relay would never open because it will be powered by the CC and solar panels. I'm sure there may be a simple solution, but I've had a few beers and don't want to hurt my brain thinking too much...
 
Last edited:
SolarRat said:
KISS. That fuse should never blow. If it does you've got bigger problems than worrying about the small chance the inverter gets harmed.

If you were to hook up a NO relay, where would you connect the trigger wire to the relay to hold it closed? If on the battery side of the fuse, the relay would never open because it still sees battery voltage. If on the CC side of the fuse, the relay would never open because it will be powered by the CC and solar panels. I'm sure there may be a simple solution, but I've had a few beers and don't want to hurt my brain thinking too much...
Click to expand...
He is talking about the solar panels frying his SCC.
 
rayfound said:
So I understand this right... If my solar charge controller is getting power from panels, and the fuse between the battery and the charge controller blows, the charge controller is fried?
Click to expand...
Let's go from @SolarRat's "few beers" answers to my "not enough coffee yet" answer. ;)

In the scenario where:
  • The fuse (or breaker) is sized appropriately to allow the solar charge controller (SCC) to provide max charge current to the battery bank (check the SCC manual)
  • The fuse is also sized correctly to protect the wire from battery to SCC
  • There is nothing else connected to that wire run (the wiring and fuse are dedicated to the SCC<->battery bank)
What are the conditions that would cause the fuse between SCC and battery to blow?
  1. The SCC delivers significantly more current to the battery bank than the SCC is rated to deliver
  2. There is a short circuit at/within the SCC
  3. Anything else? (ignoring sabotage, indoor bird strike, rodents, and other abnormal 3rd-party interference etc.)
To me, those likely mean that your SCC has already experienced a problem. So the fact that the panels are still producing power and connected to it isn't something I'm (currently) worried about as a primary SCC damaging situation.

Thoughts?
 
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