Need the solar/power pros to weigh in

[TantoTrailers]

Iirc, you have a thermometer in your electrical bay. Have a look at that as soon as you're home, and feel around the gear to see if anything feels particularly hot, including the battery. I doubt one hour in cool temperatures will push anything very hard, but you'd probably rather find a problem now than in June.

Good tip, did exactly that when I parked and everything including the DC converter were cold to the touch. It looks like I gained 12Ah back into the battery during the drive (plus a bit of sitting at camp testing and helping my buddy pack).

 

[dreadlocks]

nice, thats a clever solution you came up with tanto.. glad it worked out for you.

next time your testing it and you get it fully loaded up, I'd be curious to know what the input voltage is vs the output voltage.. slap the multimeter on its inputs when its loaded and see how much the difference is between the in and out.

 

[TantoTrailers]

So next steps I think are to do a capacity test once this thing sits on the shore charger for about 24hours right? Should I run it down to 10.5 or cut it off at 11v? When normally using, should I avoid using more than a certain amount of the overall capacity before 10.5v?

next time your testing it and you get it fully loaded up, I'd be curious to know what the input voltage is vs the output voltage.. slap the multimeter on its inputs when its loaded and see how much the difference is between the in and out.

to clarify, you are curious to know what the input v and output v is at the DC converter when the battery is 100% full and I’m hooked up to the truck ready to roll? I can try that out this week just for kicks if so.

 

[luthj]

Its a new battery, I don't think you necessarily need a capacity test unless you are just curious. I would set the capacity as labeled in the BMV. Then just plan on staying above 50% SOC for daily usage, and above 20% SOC for the occasional deep discharge.

 

[dreadlocks]

With a battery that came with a strong voltage I dont see need for a capacity test either, that would be more for one that came at like 12.4v or less and its age/health is rather unknown..

to clarify, you are curious to know what the input v and output v is at the DC converter when the battery is 100% full and I’m hooked up to the truck ready to roll? I can try that out this week just for kicks if so.

not when battery is full, with it like 70% or more depleted I'm curious the differential between the input and output voltage, how much its boosting it when loaded.. it could be dragging the trailer plug down to 11v, which would normally not be a charging rate.. Trying to figure out how many more watts its giving.. It looks like your getting ~3-4A more current and now are capable of providing a complete absorb, despite the long, thin OEM wiring.. you said it was like 18awg or something? 7A charge with that is rather impressive and it was likely limited by the battery at 90% SOC.. you may get a few more amps if you run it down further.

When battery is full this power supply is going to be at little to no load, the voltage differential then would be the basic unloaded boost you get.. ie, how much better of an absorb charge you can provide to get it to 100%, it would be good info to checkout too but would be a rather minimal baseline.

 

[TantoTrailers]

Got it! I will do the 70% test next time I get out, hopping 2 weeks or so. That is correct the wiring is 18# from the wiring harness near the engine to the DC/DC converter. I’m happy with the results but this solution is a product of all of the help I received here so I can’t take full credit I just executed as best I understood the recommendations. Thank you all for the help! @luthj thanks for the Mean Well recommendation

This battery was rated at 105Ah@20H so should I set it to that in the BMV or leave it at 100 where it’s at now for safe measure? I read somewhere or maybe it was a video that the guy stated he usually programs the battery monitor for a few Ah under the manufactured rating.
^ found where I saw it. This link Shade dropped from me a long while back https://marinehowto.com/installing-a-battery-monitor/

 

[dreadlocks]

yeah thats fine, derating it slightly is a safe practice.. its over-rating it thats a problem.. in a couple years do a full capacity test on it and then derate your BMV again a few percent from the results.. like before a big, long adventure so you roll out confident your battery is not on its last legs.

Do all the testing you can in the driveway, its easier and less inconvenient than waiting for a trip to find out that your charger needs tweaking

 

[TantoTrailers]

Regarding the DC converter, I’m going to adjust it so it’s closer to 14.4v but is it safe to run at that voltage for a longer road trip? I sometimes am on the road for 12 hours with a few stops for food gas and bathroom. This may be right after the trailer has been on shore power so battery could be full from the start.

 

[dreadlocks]

yeah thats fine, even if it was fully charged when you left 12h of 14.4v wouldn't be detrimental IMO.. thats how your starter battery gets charged, very few vehicles implement full multistage charging.. If you leave at a partial charge, say depleted at 50% SOC it'd take at LEAST 8h to get up to 100%.. probably more with less than 0.1C (10A) charge rate.

float is required if your leaving it plugged in unattended for the long haul.. you can leave batteries on float indefinitely for the most part..

Getting the battery fully absorbed at 14.4v after a long day on the road would be of greater benefit to its longevity than it not going into a float stage IMO.. my previous boondocking trailer battery setup was AGM and it died quickly because it never got back to 100% SOC until I got back home and plugged it into shore power.. I rarely drove long enough, and even when I did put a whole day on the road it still never got it back to full just using alternator output directly, I didnt have enough solar either.. so that battery lived fast and died hard being chronically undercharged for weeks on end only getting bulked up.. AGM is particularly susceptible to this abuse, whereas GC2's dont mind it nearly as much.

 

[TantoTrailers]

Excellent news! Thanks again. Now, going back full circle to the solar, I have yet to see my 2 120W panels produce much more than 100W according to the MPPT. Saturday it was full sun and high 30s so pretty much perfect conditions to get some solar. I gained back all 11Ah I consumed during the day but it never really saw a large number on either the MPPT nor the BMV. This has been the case since I got this controller and started playing with the dual panel setup. I tested it a bunch in the yard on bluebird days several times and never saw close to 200W, let alone 240W. This past weekend was the first time I had this new battery on solar and when I tested in the yard I was charging a small 12Ah sonar battery. Is it possible that I just have not put the controller/solar through enough of a power draw test to have them produce that much power or am I missing something along the way? The panels are wired in series to the MPPT with maybe 10' (probably less) 12# wire between the panels and MPPT. Voltage at the panels appears to be the same as what the MPPT is seeing. Not looking for an excuse to swap out my MPPT but......

 

[dreadlocks]

you need to discharge that battery more I think.. both cranking out full power would be ~15A, at 90% SOC your battery wont take 15A.. but it would at 70% SOC or less.. at least for a little bit.

If solar charging is limited by your battery input, you can start running other appliances.. like fans, fridges, radios and stuff and you'll see the solar wattage start going up, without your charge current going down.. basically running those for free off unused solar w/no charging penalty.. its a good time to crank the temp down on your fridge by a few degrees if your hypermiling that thing.

200W per 100Ah being sweet spot is largely because it can bulk it at a decent rate, and then provide enough excess solar to power all the daytime loads and not interfere w/battery's charging.. all while taking seasonal losses too.. getting full output in June/July is pretty easy, in Oct-March not so much.. so taking to account all those loses and stuff too.. if you put more solar on you wont see really much if any benefit at all until you go for LFP Chemistry.

 

[TantoTrailers]

So I have my Victron SBP and it came with a curveball "Program" cable. Do I need this if I am going to access it via Bluetooth? Is it as simple as installing between the battery + and the fuse box + with an inline fuse on the battery side? And which programming option should I pick? 10.5/21v?

 

[dreadlocks]

thats not program cable, thats probably the SBP Ground and external IO for Relay mode..

Put it between battery and fuse box, pay attention to the in/out on it and dont wire it up backwards.. dont push current through it backwards, make sure all charge supplies are on the IN side.

10.5v is completely dead and far too late at that point, I'd personally set it no lower than ~12v.. 12.2-12.3v ideally..

You can wire the external IO directly up to the relay on the back of the BMV-712, then you can set a Low SOC disconnect aswell.

 

[TantoTrailers]

Here is what I'm working with. Can I wire my charge sources to the battery directly instead of the BP?



Is that cable for #3 in the instructions?

 

[dreadlocks]

the "IN" side includes everything up to the battery. so directly to the battery, a special sub panel for charging, whatever you want.. as long as its on the IN side of the circuit and not the OUT, I didnt mean on the terminals directly, sorry for the confusion.. so yeah, the battery is fine if your fusing it inline correctly.

Yeah that black cable w/ring terminal is the ground for the BP, that loop thats plugged in is the remote IO.. its gotta be connected to turn on, open to turn off.. its just looped to be always on, you can yank it out and it'll shut off if you want manual control.. the other unused screw terminals are for manual programming and I think LED/Buzzer output.

If you take that loop out, run a small pair of wire from that terminal post to the COM and NC (Normally Closed) ports on the back of your BMV.. you then can configure relay alarm output in BMV to open that circuit and shutoff loads with the varying configuration options the Victron BT app gives you.. such as low state of charge, high/low voltage, high/low temps (if you got temp monitoring)