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diy solar

REC Pre-charge unit?

Yes, i use it in conjunction with a REC BMS. It works as it should.
 
Resurrecting old thread:
Yes, i use it in conjunction with a REC BMS. It works as it should.
Do you have a manual disconnect switch in your system? If so, how does that interact with the pre-charge unit?
 
Resurrecting old thread:

Do you have a manual disconnect switch in your system? If so, how does that interact with the pre-charge unit?

My LVD contactor is between the battery and the manual disconnect.
 
I use the REC precharger for my Sunny Islands.. it does NOT work quite as advertised, but its good enough.

The unit I have is supposed to have an adjustment for the amount of time before it engages the relay.. The choices are 2 seconds, 4, 8, or 11 seconds.
I have two of them and both are stuck at 4 seconds. REC tried troubleshooting but to no avail. Fortunately, the 4 seconds is enough, although I would have preferred a full 11 seconds, its not really a big deal.

You don't actually need the REC precharger.. just get on ebay and purchase a large 5 or 10 watt power resistor somewhere between 50 and 100 ohms with a heat sink enclosure.. it works just as well.. Heck, you could probably go to Home Depot and buy a water heater element and it would work fine.. most likely would barely get luke warm in your hand for the 5 or 10 seconds you use it.

You can also use a 60 or 100 watt (120v) incandescent light bulb.. the light bulb trick actually works best because, as the voltage equalizes, the light dims to nothing, giving you a measure of feedback that the process has completed and the caps are fully charged.
 
The REC is good for a contactor based BMS where you need the automated connection. It is better to use a manual method with a breaker.
 
^^
my system is pretty much automated so it needs to handle itself.
But to be honnest , if I were to build it again , a manual switch and resistor would work just as well. The auto feature is only used on startup. And I only need one.
The system doesn't do what i wanted it to do. Although it does a great job of controlling the sunny island charge algorithm.
 
I use the REC with my Sunny Island, i guess my system is pretty standard so i didn’t have any issues - it just works for what i need.

On my bore pump system with supercaps i manually precharge because of the massive capacity of the maxwell supercaps. If that system disconnects i have to manually precharge every time.

A well setup system doesn’t really disconnect though.
 
These are expensive for what they do, but it's an easy hands off box that's worth the money for me as it just works (sorta). I used one on my old Powerhouse Auto BMS that used a 500amp contactor. As @MurphyGuy stated, mine also was adjustable from 2-11 seconds but it never worked higher than 4-6 seconds. However that's still plenty, but I too would have preferred the full 11 seconds.

Testing on the bench back in 2019:

nu3I5pL.jpg


and the potentiometer:

GeTboRe.jpg


And install:

cz0YFlF.jpg
 
If your system looks like this: batt (+)->contactor->big switch->balance of system; does the pre-charge unit wait until you close the big switch before doing its thing, and then closing the contactor?
 
No it's the batt + -> On/Off -> contactor -> bus bar.

The BMS is what controls the precharge as it has a 12v allow to charge, 12v allow to discharge and 12v master cut of signal. I used the master cut off signal to control the contactor.
 
No it's the batt + -> On/Off -> contactor -> bus bar.

The BMS is what controls the precharge as it has a 12v allow to charge, 12v allow to discharge and 12v master cut of signal. I used the master cut off signal to control the contactor.
I should have replied to this earlier, sorry.

In your system, if the BMS activates the 12V allow to charge, but the battery switch is open, does the contactor close?
 
My BMS is different. There is allow to charge, allow to discharge and master on/off. The master on/off has set points to open/close the contactor. This is in case the allow to charge or allow to discharge isn't acted upon (something fails or the wiring is disconnected). When the BMS is powered on and the voltages are in range, it will close the contactor.
 
I got the advice to add a pre-charge (from rec bms) for my contactor last line of defense system (image below).

Now I dont use the rec bms (but the jbd-sp040s020), can the rec bms pre-charge work as stand-alone? or potentially work by the relay of the BMV-712?

Venezia wiring.png
 
Sorry guys, I'm still not clear on this.

If the pre-charge is activated (by the BMS closing its relay), but the main disconnect switch is open, then the 4s pre-charge timer expires without anything getting charged. Then, at some point later, you close the disconnect switch and you get the in-rush. I feel like that isn't desired. And since the disconnect switch is there to be used during maintenance, for example when configuring the BMS… maybe I'm chasing a non-issue?

I do like the override button in your setup @ericjanvanputten .

A.
 
The precharge is just to protect the contactor - so other than arc damage on the disconnect, it doesn’t really matter.

I have a startup/shutdown procedure attached to the wall right next to the disconnect so it’s unlikely to be done in the wrong order.

I use a disconnect as shown, as they are bulletproof when it comes to arc damage.
 

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I got the advice to add a pre-charge (from rec bms) for my contactor last line of defense system (image below).

Now I dont use the rec bms (but the jbd-sp040s020), can the rec bms pre-charge work as stand-alone? or potentially work by the relay of the BMV-712?
Be careful with the relay of the 712 as that can only support up to 1 amp of current. While the EV200 holding current is only 130 mA, it can have an inrush current of 3.8 amps. Maybe use a SolidSwitch 104 that can handle up to 4 amps: https://www.victronenergy.com/accessories/solidswitch-104
 
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