Battery REQUIRED to be connected to SCC???

[TheGriz]

Hello folks,

In reading all the documentation on the various SCCs, the documentation is consistently saying to have battery connected to SCC before attaching solar panel(s). However if my memory serves me correctly, I have seen videos and posts that conflicts with that documentation, essentially stating there has been no evidence that solar panels hooks to SCC WITHOUT attached battery has damaged the SCC.

Is there a final verdict? Will attaching Solar Panel to SCC without attached Battery damage the SCC, or not?

Reason I ask is, my EPever Tracer 30 amp SCC is scheduled for delivery tomorrow. I am using the Chargery BMS8T with the two 400 amp DC Contactors. If the voltage hits the overcharge cutoff, it disconnects the battery from the SCC and the Solar Panel is still attached to the SCC. Hence, I am concerned that the new SCC will be damaged. Or am I misunderstanding something?

Insight appreciated!
Mike

P.S. - Damn those DC Contactors get hot!

 

[snoobler]

The vast majority of manufacturers require connecting battery before panels. Many have attempted to destroy them deliberately by performing the reverse to test this. It appeared to be a true danger at one point. In the vast majority of cases, there is no concern; however, a recent thread included a YouTube video where a user destroyed two via the panel-first method. However, this was a SCC with an on-board Lithium BMS, and it blew the BMS chip only.

 

[MisterSandals]

Is there a final verdict? Will attaching Solar Panel to SCC without attached Battery damage the SCC, or not?

One thing (among many i think) you should watch for is the voltage that the SCC "assumes" when connected to the panel(s). My experience is that an SCC will assume the working voltage closest to the panel voltage.

Some SCC's, particularly the Victrons, will power on from any voltage battery. At this point, its recommended that you specifically set the working voltage in the parameters. This is mighty useful if you momentarily lose contact with your battery, it will use the set voltage rather than the voltage it "assumes" (right or wrong).

And, I REALLY don't think you should mess with an SCC without a battery attached, first.

 

[TheGriz]

One thing (among many i think) you should watch for is the voltage that the SCC "assumes" when connected to the panel(s). My experience is that an SCC will assume the working voltage closest to the panel voltage.

Some SCC's, particularly the Victrons, will power on from any voltage battery. At this point, its recommended that you specifically set the working voltage in the parameters. This is mighty useful if you momentarily lose contact with your battery, it will use the set voltage rather than the voltage it "assumes" (right or wrong).

And, I REALLY don't think you should mess with an SCC without a battery attached, first.

So if I understand you correctly, you are stating to set the high voltage disconnect of the SCC in my case at the high end of my LFP pack...say somewhere north of 14V (which I certainly agree). What happens then if the BMS shuts of the charging when ONE CELL hits the high voltage disconnect before the SCC hits the TOTAL voltage disconnect parameter? We are again in a situation of panels attached to SCC with no battery connected.

I don't think my set up is at all unique. What is everyone else doing?

 

[cass3825]

Griz, I placed the charge relay on the PV side of the SCC, so charging is interrupted without disconnecting the SCC from the batt bank.

 

[gnubie]

Personally I've not seen a controller fail due to being connected to PV without a battery attached, despite testing quite a few. Some do go off the rails and it does depend on the sequence of events. There are a few controllers that will start from PV alone, allowing them to lift a dead flat battery. Victron, certain Renogy (SRNE OEM ones) and others.

Victron controllers remember the battery voltage they first see out of the box (or from factory reset), or if they are started from PV the first time out of the box assume 12V battery. From then on even without a battery preset they will regulate reasonably well at the voltages appropriate for that battery, float 13.8, absorb 14.4 or what ever is set in the battery profile. Disconnecting under high current, at least in my testing of 100/20 model, does not see the voltage spike way up, so good job Victron.

Renogy Rovers (the SRNE ones) require the battery voltage is manually set for the lift from flat to work. Disconnecting under high current did see the voltage fly up but the controller survived. There may be a clamp diode in there, but I didn't check with a 'scope to find out.

MakeSkyBlue controllers can not start from PV alone, so saving grace there but should battery go away once the controller has started the output starts to oscillate at a great rate of knots and is all over the place in terms of voltage. The controller does survive it though.

There's more than just the controller to consider. What happens to any loads that might remain connected to the system when the battery goes away? Victron, likely everything fine since voltages are contained. Renogy, might let the smoke out from the spike at disconnection. MakeSkyBlue, have your cheque book open and pen in hand ready to order replacement equipment.

 

[Primal1]

My first year or so off grid I had two different types of batteries a marine 64 ah battery and an 18ah sla. I had alligator clips on the battery side connection of my Renogy wanderer. I very carefully swapped the leads daily to get both batteries charged for over a year. Still have the old Renogy CC and it still works fine. I upgraded to a mppt about a month ago and the wanderer is now a back up.

I have a 215ah bank and I no longer need to do the swap, but it was an everyday, multiple times a day thing. I was using my starter battery and a secondary for my cpap at night. I'm in my cabin now instead of my vehicle but panels were put on the car daily and taken down when I went to town the same way.

 

[MisterSandals]

So if I understand you correctly, you are stating to set the high voltage disconnect of the SCC in my case

I was referring to the working voltage of the system, as in the battery voltage: 12v, 24v, 48v...

I've had an accidental but momentary battery disconnect once and the SCC switched from 12v charging (voltage of my battery) to 24v charging (closer to the 30v of my panels). I was fortunate to have been watching.

 

[MisterSandals]

Victron controllers remember the battery voltage they first see out of the box (or from factory reset), or if they are started from PV the first time out of the box assume 12V battery.

This is not how my Victron 100/30 (as seen thru the app anyway) worked out of the box. The battery voltage (sorry, cannot recall exact wording) remained blank until I actually set the value. If it "remembered" the battery voltage I had no indication of that from the app user interface.

 

[gnubie]

Interesting. The firmware on any Victron for some time now automatically remembers the battery voltage first seen, ie out of box (or factory reset), connect to battery, stored. This is certainly how my 2nd hand 100/50 behaved with 1.4x (sorry cant remember version, it's now on 1.5) and is defintely how a 100/20 on 1.47 (also now on 1.5) I recently took out of the box new behaved.

*edit for further info*

I am aware that earlier firmware (prior to 1.4 I think) did have a different behaviour where the units would not store the battery voltage, ie would re-detect at each connect to battery until the user manually set it.

victronconnect:mppt-solarchargers [Victron Energy]

www.victronenergy.com

 

[tictag]

Generally speaking the only time you really need the battery connected is when you first hook-up the SCC as many (most, probably all these days) automatically select the battery system voltage at this point. After that, there's very little evidence supporting damage to a SCC due to battery disconnect and whole lot of evidence supporting the contrary.

In your case (i.e. concerned about your BMS disconnecting) ... there's nothing to worry about. Rest easy.


Famous last words...

 

[TheGriz]

Generally speaking the only time you really need the battery connected is when you first hook-up the SCC as many (most, probably all these days) automatically select the battery system voltage at this point. After that, there's very little evidence supporting damage to a SCC due to battery disconnect and whole lot of evidence supporting the contrary.

In your case (i.e. concerned about your BMS disconnecting) ... there's nothing to worry about. Rest easy.


Famous last words...

LOLOL...thanks! Any way of confirming if the EPever Tracer 30amp SCC is one of the "many...most"? And is there anything else besides the post initial install mismatch that is problematic?

 

[MisterSandals]

Any way of confirming if the EPever Tracer 30amp SCC is one of the "many...most"?

If your SCC is multi-voltage, it pretty much has to be able to handle and detect any of the supported voltages. I'd use a battery with a voltage that makes it clear what the voltage should be until you get a chance to "set" the voltage.

 

[diyernh]

My Outback FlexMax 60 MPPT SCC needs a battery to turn itself on. I try to leave the batteries on and the solar attempting to get some charge during the winter. My reason is a dehumidification system that needs to work during the sunny spring days, and using the solar to heat the LiFePO4 batteries until they warm, then charging happens.

Last winter, I found the SCC failed to work for months. The deep cycle flooded lead acid batteries had dropped low enough that the SCC would not boot up. It never did until I came to camp and used the charger and a generator to charge the batteries. This is not what I wanted. There were months of sunny days and the SCC did nothing.

I added more solar this year, upsized the solar wires, added a Victron Multiplus, smartshunt, and 400Ah of Lithium. I left the Outback FlexMax as I already had it, and it has a solar dump feature (for battery heaters).

I played with the settings in the fall and noticed the Outback needs 10VDC for 30 seconds before it will boot. I set the Victron Battery protect to 10.5V to cut off. This was in August/September.

I'm at camp now. When I arrived, there was no battery power. The BMS's had shut off, low voltage. I'm pretty sure the Smart Shunt, Battery Protect, and the Outback SCC standby currents spent down the batteries until they shut down. Again, I had to charge with a generator to get any power. (of course, I had fuel problems with water/ice that made this unnecessarily frustrating).

So my issue is the Outback FlexMax 60 MPPT SCC. How do I get the power to boot this up? Is there a modification to the SCC? Maybe swap to Victron (without a solar dump feature)? Maybe run a Victron SCC just enough to boot the Outback (set Victron to charge to 10.5V)?

I will probably not have any other source of power besides solar. Winter has many days without any. I drove here in a snowstorm, and the snow stuck to the panels for 3 days. On the 4th day, it was warm enough to slide the snow off, but there won't be any sun for another 2-3 days. I expect there will be 2 months easily with no solar. I would like the system to boot up on any warm day in February/March as the sun arrives and the snow melts. This is when I need the dehumidification to start working.