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Use a Victron smart battery protect BP-65 to disconnect solar panel controller from solar panel ?

RandyP

Solar Enthusiast
Joined
Sep 21, 2019
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I would like to use the Victron smart BP-65 to disconnect the solar panels from the solar controller at the battery high voltage set point as sensed by a BMV 721 smart battery management device.
I hope to use the BMV 712 high voltage relay as the remote relay for the BP 65, with the BP 65 in the [ , Lithium Ion Mode.
The BP 65 would see the solar cell voltage (Voc 24.06, V mppt 19.67),
the BMV 712 would see the battery voltage.
LiFePO4 Battery.
Should this work or is it problematic.
 
You can not use the BP65,100,or 220 as a remote disconnection switch between PV and a solar controller unless you are looking for a fire, They are not rated for voltage that high. They can only be used between the controller and battery.
Use a mechanical contactor that is rated for the max voltage the PV puts out in max sun and -20 deg f.
 
You can not use the BP65,100,or 220 as a remote disconnection switch between PV and a solar controller unless you are looking for a fire, They are not rated for voltage that high. They can only be used between the controller and battery.
Use a mechanical contactor that is rated for the max voltage the PV puts out in max sun and -20 deg f.
Normally I'd agree with you, @Geriakt, but as long as his voltage stays within the stated 24.06VOC (or thereabouts), @RandyP would actually be fine using the device in this manner. With the panels in parallel connection (no series), and being triggered on/off by the BMV while in Li-ion mode, the Smart BP65 would work fine for this application. It would be very important to note that for this application, the battery would be connected to the "out" pole and the panels would be connected to the "in" post.
 
Normally I'd agree with you, @Geriakt, but as long as his voltage stays within the stated 24.06VOC (or thereabouts), @RandyP would actually be fine using the device in this manner. With the panels in parallel connection (no series), and being triggered on/off by the BMV while in Li-ion mode, the Smart BP65 would work fine for this application. It would be very important to note that for this application, the battery would be connected to the "out" pole and the panels would be connected to the "in" post.
I was intending to connect the
Solar Panels (+) to the IN post and the
Solar Controller input (+) to the OUT post.
Solar panels wired in Parallel,
12v system panels,
rated Voc 24.06, V mppt 19.67
 
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I was intending to connect the
Solar Panels (+) to the IN post and the
Solar Controller input (+) to the OUT post.
Solar panels wired in Parallel,
12v system panels,
rated Voc 24.06, V mppt 19.67
Ah, yes, sorry, brain fart, I had switched to thinking between controller and battery when writing the second bit of that...
 
Just out of interest, why do you want to disconnect between the panel and the CC, rather than between the CC and the battery?
 
Just out of interest, why do you want to disconnect between the panel and the CC, rather than between the CC and the battery?
This bit actually makes sense to me... I always recommend being able to fully isolate the controller from both battery and PV sides, and given the (tiny, but still documented) risk to a controller posed by disconnecting the battery while the PV is still running hot, this is a viable method of disconnection on that side. Normally I'd recommend a Bussman 185 breaker or a MidNite Solar MNEPV breaker for it, but at the stated voltages there's no reason a Smart BP wouldn't do the job.
 
I have ask the same question ar community.victronenergy.com no answer yes but 10 people following the question.
 
.....
given the (tiny, but still documented) risk to a controller posed by disconnecting the battery while the PV is still running hot, this is a viable method of disconnection on that side.
.........
That's why i would like to disconnect the solar panel side, first.
 
That's why i would like to disconnect the solar panel side, first.
Ahhh I see your questions on this thread https://community.victronenergy.com/questions/21875/battery-connect-to-cut-mppt-charging.html, but I can't find a question specifically regarding your proposed installation... Sorry I haven't addressed them; I try to stay up on the community but it's been a busy week.
The whole "to disconnect a battery while the controller is charging" question gets a bit circular, really... Victron says don't do it, but then again that's exactly what a BMS will do if it sees over-voltage (shut down the allow-to-charge contactor), and that's a Victron-supported function.
I asked Victron level 3 support about the issue and their response was, in summary, that cutting out the battery while the controller is charging full-bore could conceivably damage the controller, which is why their manuals always say to disconnect PV first, but then again they couldn't say that it's ever actually happened.
I've personally done extensive testing on my bench, trying to force an MPPT into fault by repeatedly cutting the battery connections in and out while the controller was charging full-bore, and failed to cause any faults after several hours of various methods of removing the battery connection... up to and including literally yanking the wires out of the "battery" terminals on the MPPT, trying to replicate a FUBAR fault condition. In no case was I able to cause a fault in the MPPT, so my bottom-line conclusion is that although it's recommended to cut out PV first, the likelihood of causing damage by turning off the battery connection first seems so slim as to be negligible.
 
The question posted on the community questions is "
Use a Victron smart battery protect BP-65 to disconnect solar panel controller from solar panel ?
"
 
I will be using a Renogy RBC50D1S controller/dc-dc charger. May not be same form fit function as the Victron controllers.
 
I will be using a Renogy RBC50D1S controller/dc-dc charger. May not be same form fit function as the Victron controllers.
I got to your question on community, though of course my answer was pretty much the same as it was here :p
We don't distribute/support Renogy products, so I can't speak as to the connection/etc from the SBP to it, but honestly that really shouldn't matter - the SBP doesn't know what is connected to its "out" post and, so long as it's not getting reverse current into it, doesn't care.
 
I understand why you want to place the BP65 between the PV and the Mppt. This makes more sense to me than using it between the Mppt and battery. Every time i have asked about doing the same Victron has always said no. Now i read your post on Victron Support and you got a yes. Go figure.
I use a bp65 on my Epever Mppt (wish i never bought) and have breakers on the PV and battery out, if my BMS should shut the bp65 down, i just turn off the PV breakers. This procedure is followed when i shut the main battery switch off for storage in my RV.
Another and ppossible option is if you are using a Victron MPPT you can just connect the Victron non inverting cable to the VE bus connection on the Mppt and this will act as a remote switch and the cable is cheaper.
This cable will work for Victron 100/30 and 100/50. Victron Smart Mppt 150/45 and up have built in remote switchs and neither the remote cable or bp65 are needed.
 
I understand why you want to place the BP65 between the PV and the Mppt. This makes more sense to me than using it between the Mppt and battery. Every time i have asked about doing the same Victron has always said no. Now i read your post on Victron Support and you got a yes. Go figure.
Victron will usually say no to such a configuration because the PV voltage can so easily exceed the SBP's capabilities; many single PV panels have a VOC already over the max voltage of an SBP. In this case, however, with a VOC of 20-21, it's perfectly acceptable so long as the panels are never connected in series.
 
I don’t have one in mind but surely there are relays that meet the specs.
 
Ahhh I see your questions on this thread https://community.victronenergy.com/questions/21875/battery-connect-to-cut-mppt-charging.html, but I can't find a question specifically regarding your proposed installation... Sorry I haven't addressed them; I try to stay up on the community but it's been a busy week.
The whole "to disconnect a battery while the controller is charging" question gets a bit circular, really... Victron says don't do it, but then again that's exactly what a BMS will do if it sees over-voltage (shut down the allow-to-charge contactor), and that's a Victron-supported function.
I asked Victron level 3 support about the issue and their response was, in summary, that cutting out the battery while the controller is charging full-bore could conceivably damage the controller, which is why their manuals always say to disconnect PV first, but then again they couldn't say that it's ever actually happened.
I've personally done extensive testing on my bench, trying to force an MPPT into fault by repeatedly cutting the battery connections in and out while the controller was charging full-bore, and failed to cause any faults after several hours of various methods of removing the battery connection... up to and including literally yanking the wires out of the "battery" terminals on the MPPT, trying to replicate a FUBAR fault condition. In no case was I able to cause a fault in the MPPT, so my bottom-line conclusion is that although it's recommended to cut out PV first, the likelihood of causing damage by turning off the battery connection first seems so slim as to be negligible.
This is a “problem” I’ve recently been made aware of in this thread LiFePO4 heating pad for cold temperatures. To me it seems crazy that Victron would sell a system that could possibly damage the SCC if the BMS cuts off the battery, for any reason. It shouldn’t matter if it’s a built in BMS in a drop in replacement LFO or a self built package. I’ve read the manual for a normal 75/15 smart solar and the only explanation to WHY you should connect the battery first I could find was because of the battery voltage sensing 12V/24V.
If there is an actual risk and problem here, more or less every solar system using any type of BMS always MUST have a relay breaking the connection between the PV and the SCC. How would you solve that with say a BattleBorn that has the BMS built in?!
 
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If there is an actual risk and problem here, more or less every solar system using any type of BMS always MUST have a relay breaking the connection between the PV and the SCC. How would you solve that with say a BattleBorn that has the BMS built in?!
If you have a battery monitor system, there may be a feature in the BM that changes state of a contact in that device.
I use a BMV-712 Smart, Battery Monitor Smart, bluetooth inside, made by Victron. Using the bluetooth feature you can program under voltage relay set point to act as a relay for battery under voltage, set point is selectable. By using this setpoint to drive the BP-65 (Battery Protect) you can cause the BP to open at a low voltage point just greater than the voltage that would cause the drop in battery replacement BMS low voltage point to isolate the battery from the load. So the BP-65 smart could open the solar power supply to the SCC before the batteries BMS isolates the battery from the system.
 
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