diy solar

diy solar

Testing my Valence U27-12XP

Cliffman said:
Oh then I would have some kind of auto disconnect FOR SURE!
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Hmmm, there's actually some challenges here... Victron manual states:

"3. The BP is designed to allow current to flow from IN (battery) to OUT (load) terminals only. Reverse currents from OUT to IN terminals are strictly forbidden, and will damage the device. If you wish to use the BP as a disconnection for a charge source, you must orient the unit in the system so that the current is flowing in the intended direction, IN to OUT. "

So i can't place the disconnect between the battery and the DC distribution panel, as when connected to shore power the current would be flowing to battery from the converter. I wonder if I could use a SSR triggered from the SCC's LOAD terminals to interrupt in the case of a low voltage condition? Do they consume significant energy to hold open?
 
rayfound said:
Yeah. I don't have an inverter, just DC loads.
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I ended up buying 2 of the 10 to 'tinker with' and I think they're going to work out just fine in my Airstream, the Victron multiplus will cut off the inverter via settings when it gets LVCO via AC side of things, and I've got an Nvidia Jetson TX2 and an INA2331 that lets me read the voltage and toggle another relay that will disconnect DC loads at a voltage you think is "safe enough".
 
Can anyone suggest a N/O relay that I could use switched via solar Load terminals to act as a makeshift low-voltage disconnect?
 
Any relay that's rated for the amps your pushing should be legit.. you talking something you can turn on/off with like a GPIO pin or something or what?
 
AirStreamJoe said:
Any relay that's rated for the amps your pushing should be legit.. you talking something you can turn on/off with like a GPIO pin or something or what?
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So I was thinking I would use the LOAD terminals from my renogy Rover MPPT controller. One of the modes is a low voltage cutoff. My understanding is that it will disconnect LOAD terminals at 11.0 V which should work just dandy from a "protect the battery" standpoint. I am not really sure what my other options are for a low voltage disconnect, as the Victron indicates it can't be charged through.
 
sounds reasonable, but I don't want to steer you in the wrong.. I get all my victron stuff on thursday and get to start playing around with them
 
rayfound said:
So I was thinking I would use the LOAD terminals from my renogy Rover MPPT controller. One of the modes is a low voltage cutoff. My understanding is that it will disconnect LOAD terminals at 11.0 V which should work just dandy from a "protect the battery" standpoint. I am not really sure what my other options are for a low voltage disconnect, as the Victron indicates it can't be charged through.
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Ray I dont know if you have found a suitable relay yet. I have used these automotive "diesel glow plug" relays and they are good for 200Amps maybe overkill but it will never burn the contacts $17
https://www.amazon.com/XtremeAmazin...eywords=glow+plug+relay&qid=1581948919&sr=8-7
 
That one is only really rated for 80A continuous. Note from the linked page.
Note: Normally Make 80A as Working Current, Need Break 5 sec on, 50 min off -/ If u need a long working one, pls note us.
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A lot of those that say they are rated for 300A continuous aren't really. I have these, TYCO ev2000aaana rated for 500A. They are the ones used in the trucks that the Valence batteries come out of. Here's some on ebay https://www.ebay.com/itm/TE-Connect...584029?hash=item4454914a5d:g:hnAAAOSw4gVeMIm3
You might contact some of those Valence sellers. That's where I got mine.
 
I realize this is an older thread, but thought I'd post this here anyway. This is copied from a post I made in the Valence super thread.

Hi all, I'm trying to work out what the capacity of my 2 u27-12xp batteries is. I was hoping someone might be able to check my method for testing them. I have the 2 modules wired in parallel, and am testing them by running a space heater off of a renogy 2000w inverter/charger. I am measuring the current using a victron BMV 712. I have the space heater set on low which pulls about 775 watts as measured by the shunt. My method for assuming that the SOC is at 100% is basically just waiting for the charger to decide to stop charging. Once the charger has stopped its charging cycle, I check the cell voltage using a thunderstruck vc1. The highest resting voltage I've seen so far is about 3.4v/cell. I begin the test there and end it when I hit 3v/cell. When the test is over (which I must be doing wrong) the BMV reads that 182 amps have been used. Thats 65% of the capacity I should be getting! I realize these are used batteries, and probably won't deliver the full 138ah/module anymore, but that seems super low! Can anyone show me where I've gone wrong/how you should do a proper capacity test? Is my charger not charging them all the way up? The ebay seller says they should have >90% of life span on them still.
 
What is the charger set to? To test any LifePo4 battery you really need to do a full cycle. That means charging them fully to 14.6 volts then discharge to 10 volts to get the full capacity.
 
charger was set to 14.6. I'll try discharging to 10v but would that really make up another ~100 AH? the problem is that they don't seem to hold a charge over 13.4v
 
Nainoa said:
charger was set to 14.6. I'll try discharging to 10v but would that really make up another ~100 AH? the problem is that they don't seem to hold a charge over 13.4v
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The ebay seller, responded with this as well. Does that sound like the right approach?
 

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Not really. But I don't have that battery. I have the smaller Valence RT batteries and they have an internal BMS and don't require an external BMS.

Only thing I can suggest is to test the batteries separately. That would be very telling.
 
Gazoo said:
Not really. But I don't have that battery. I have the smaller Valence RT batteries and they have an internal BMS and don't require an external BMS.

Only thing I can suggest is to test the batteries separately. That would be very telling.
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Thanks, I did amd neither one would hold a charge above 13.3. Ebay seller is actually issuing a refund! Thanks for responding!
 
Nainoa said:
Thanks, I did amd neither one would hold a charge above 13.3. Ebay seller is actually issuing a refund! Thanks for responding!
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Just curious. Did you capacity test each one. The resting voltage is around 13.3 volts.
 
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