Critique my solar charger/battery monitor setup?

[DaveInDenver]

Apparently the Telecom likes pos ground.

Telecom is generally -48V and done to prevent electro-migration of copper from wires back to the Earth. Solar panels are positively grounded to prevent what SunPower terms surface polarization. Not sure how widespread of an "issue" it is for portable products but it's worth mentioning as something to know about when shopping for panels and controllers. It's not unusual for permanent installations to find positive grounding relative to Earth, though.

 

[luthj]

Talk about a tangent. Positive ground grid tie controllers.... Not like the OP has one!

 

[john61ct]

So long as telecom gear is well isolated, just reverse the output leads to get +48V and use negative for both Return and Reference Common, and no problem tying those wrt DC systems to whatever form of "ground" you like in multiple locations.

 

[Buddha.]

You need to size based on your converter. Whatever its charge output is, plus 50% for power factor and efficiency losses. The inverter could be located wherever appropriate. Most are not going to work under the hood, so you would need to put in a dry space.

My converter's output is 60 amp x 1.5 = 90 amp. 90amp *13v = 1215. I would need an inverter that's at least 1200w then? I have dual batteries and a 160amp alternator. Would that keep up with an extra 90amp draw? That would be max draw and probably less than 30-60 min so probably?

 

[luthj]

Yep, that's a good estimate. You should be fine alternator wise.

 

[Buddha.]

Yep, that's a good estimate. You should be fine alternator wise.

I can't figure out what size cable/ breaker to use.

If I mount the inverter inside the front of my topper that should be about 15' from the battery. The inverter would be 1500w. That's about 120 amps DC. I tried to use the online calculators/charts and I can't figure out if there taking into account both the positive and negative run. I don't know how much voltage drop is acceptable. Some results are 2-0 awg , some are off the charts huge. I watched a youtube vid where a guy used 2 awg for a 3000w inverter and read an article where a guy used 1/0 for 1800w. I'm lost.

What size cable/breaker if the 1500w inverter is 15 feet from the battery?

 

[luthj]

Okay,

30ft run (including return trip)
120A continuous current
Max drop of 6%

3AWG will work, you could bump that to 2AWG as 3 is not a common stock size.

Inverter wire sizing guides are going to take into account inverter surge current (like starting an AC unit). Since your not doing that, you don't need to use mega cable.

 

[Justin Cook]

*blink* Max drop of 6%? Only for lighting and nonessential loads, and even then I wouldn't do that... inverters and other heavy loads need to stay below 3% so your wires don't heat up from the v drop and they don't shut down from low voltage even when your battery is in decent shape.

2/0 will net you a total v drop of ~2.39% over a 30' round-trip run at 120A. + a 150A MRBF or ANL fuse & you're good.

^^That's based on USCG, ABYC, and UL standards, which of course you don't have to follow because you're not a boat or a house... but if you want to do it right and have your components functioning properly and with the greatest efficiency possible, this is how you do it.

 

[luthj]

With an alternator at 14v, low voltage with 6% drop isn't a concern. Plus that's max current, it won't be seen for more than 20 minutes after a deep discharge.

 

[Bayou Boy]

I can't figure out what size cable/ breaker to use.

If I mount the inverter inside the front of my topper that should be about 15' from the battery. The inverter would be 1500w. That's about 120 amps DC. I tried to use the online calculators/charts and I can't figure out if there taking into account both the positive and negative run. I don't know how much voltage drop is acceptable. Some results are 2-0 awg , some are off the charts huge. I watched a youtube vid where a guy used 2 awg for a 3000w inverter and read an article where a guy used 1/0 for 1800w. I'm lost.

What size cable/breaker if the 1500w inverter is 15 feet from the battery?

So we went from not wanting to run anything larger than 10awg to installing a 1500watt inverter and running 2awg?

Wow. Just buy these two things and call it a day.

If you end up wanting to add a dc charger later you’re already set up for it.

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[luthj]

Lots of ways to charge a battery. Getting full absorb voltage has serious benefits.

 

[john61ct]

If using lead, need to get to 100% Full as per mfg spec for longevity, ideally ASAP, for most of the time and at least every other cycle.

LFP it's the opposite, best longevity from keeping at low SoC.

 

[Bayou Boy]

If using lead, need to get to 100% Full as per mfg spec for longevity, ideally ASAP, for most of the time and at least every other cycle.

LFP it's the opposite, best longevity from keeping at low SoC.

The guy is installing solar. Bulk charge while driving with the truck. Finish off with solar. The combo works exceptionally well. He will be at 100% the majority of the time.


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[john61ct]

It usually doesn't just happen by default.

There often needs to be an explicit intention, monitoring and adjustments made to ensure the endAmps point is reached at the right voltage.

And with AGM you need to also ensure AHT doesn't go too long or lifespan will also be shortened, unlike FLA.

 

[Bayou Boy]

It usually doesn't just happen by default.

There often needs to be an explicit intention, monitoring and adjustments made to ensure the endAmps point is reached at the right voltage.

And with AGM you need to also ensure AHT doesn't go too long or lifespan will also be shortened, unlike FLA.

Have you had that combo on a camper before and consistently failed to see it go to 100%?

Because I have had that setup on multiple campers and consistently seen 100%. The solar will charge regardless of whether the truck is hooked up or not and will get the batteries to 100% if there is sun every single day if sized correctly.


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