Critique my solar charger/battery monitor setup?

Buddha.

Lurker
The mppt route will work fine with correct components.

400w and 200AH will run a fridge all summer without trouble. In the winter there are capacity loss issues and low sun angle.
What about this fed into my Victron mppt 100/30 posted above? I need diodes at both the panel's input to the mppt and the booster's input into the mppt?
booster.jpg
 
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Bayou Boy

Adventurer
The mppt route will work fine with correct components.

400w and 200AH will run a fridge all summer without trouble. In the winter there are capacity loss issues and low sun angle.
He's not running a fridge. He's running a 12v heater in a 30ft long camper. Heater fans absolutely suck power. Amazingly so.

@Buddha. ? What make is your camper? Insulation quality and single vs double paned windows are going to make a huge difference in how much that furnace will run. I was shocked at how much more my heater ran in my Jayco Eagle compared to my previous Outdoors RV as well as the cold spots all over.
 

Bayou Boy

Adventurer
What about this fed into my Victron mppt 100/30 posted above? I need diodes at both the panel's input to the mppt and the booster's input into the mppt?
View attachment 565366
My assumption is that this is that box.


I would not trust a $30 box from China as a reliable charge source for long term travel, but that's just me.

The description claims 93% efficiency. I bet it isn't close to that and it'll waste power and heat up like crazy, losing more power and eventually failing due to the heat.
 

Buddha.

Lurker
He's not running a fridge. He's running a 12v heater in a 30ft long camper. Heater fans absolutely suck power. Amazingly so.

@Buddha. ? What make is your camper? Insulation quality and single vs double paned windows are going to make a huge difference in how much that furnace will run. I was shocked at how much more my heater ran in my Jayco Eagle compared to my previous Outdoors RV as well as the cold spots all over.
It's a 2005 Pilgrim M-282 RBSS, I'd never heard of them either. I don't think it's insulated the best but two 1500w heaters on low keep it warm enough at 30f.
 

Bayou Boy

Adventurer
Before going to bed, this is my personal opinion on this.

Your 400 watt solar setup will be sufficient since you are moving around a decent amount. I'd want 4 batteries instead of 2 in case you get some cloudy days. I'd also run a simple 8 or 6 gauge charging line with an Anderson connector instead of that converter into the solar charge controller. Simple is better here. The solar amps plus the charge line will get you to 100% quicker than you'd think.

In summary, keep it simple.
 

Bayou Boy

Adventurer
sure it works. Some people even use inverters to send high voltage AC back to the camper for charging.
Inefficient ?
I dunno... With a bigazz alternator driven by a thirsty bigazz motor, a Legitimate ExPo Guy wont worry about it.
The box is only rated at 15 amps. Add some inefficiency and a chinese fudge factor and it's probably really 10. That's not even enough to run the wiring for.
 

Alloy

Well-known member
Let the solar panels charge the batteries while driving. If you need to charge the batteries more then use a generator or a set of jumper cables from the tow vehicle after you've parked.

I agree with others 2x6V isn't enough. For one of our trailers I carried a 2nd set of 6V in the truck along with +/- jumper wires for the first summer. In the fall I slid the propane tanks forward so a larger battery box would go in.

Brakes needs to be on their own circuit. Connected directly to the batteries is best. Never through a battery disconnect. Some people like to fuse the brake circuit others don't. Either way brakes should be tested on a regular basis with 2 methods. One using the brake controller and doing a tug test. The 2nd is to pull the breakaway switch and doing a tug test. Surprising how many people find out they've been hooking up a breakaway switch that doesn't work.

This is the breakaway switch I use. Also carry a spare pin.


You may have a 60A converter but all you get out of it s is 30A due to the mini breaker. Under heavy use the mini breaker will be cooked. If the wire is 6ga wire it may be possible to upgrade the breaker but don't use another mini breaker. I've seen many that have failed.

If the converter is a WAFCO it is a pcs of junk. It's a power supply not a battery charger. When on shore power it is best to disconnect the batteries or the WAFCO will ruin the batteries

The wire from the main breaker/disconnect to the batteries needs to be size for combined input of the converter and the solar controller.
 

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john61ct

Adventurer
Efficiency matters **not a whit** on mains or alt while driving anyway as power sources.

With mains power at the end of the trip, forget about an elegant DC setup, cheapest solutions with safety and reliability are all that's needed.

8 hours of driving getting 2-3 pair GCs to 100% Full.

If you want to stop more than 24hrs, get a mains powered location and recharge from that.

Done, don't even bother with solar until you need it.
 

Bayou Boy

Adventurer
8 hours of driving getting 2-3 pair GCs to 100% Full.

If you want to stop more than 24hrs, get a mains powered location and recharge from that.

Done, don't even bother with solar until you need it.
8 hours of driving will not get more than 25 or 30 amp hours back into the batteries from a normal 7 way. On some setups it’ll only be 15 or 20 amp hours. I’ve watched it on actual shunt based monitors on multiple campers.

I wouldn’t call adding 5-10% of capacity, full or anything more than negligible.


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luthj

Engineer In Residence
That 12-36V unit should work fine with proper sized wiring/fusing. You will want diodes to block reverse current to the panels. Or DPDT switch to toggle between the panels and 36V supply when the unit is energized.

What is the rating of your solar charger? If its rated for ~30A output, then you should be fine with the 36V supply at 540W. I would feel comfortable pulling ~350W from that unit. I typically assume 80% of the MFG rating in these cases. If it doesn't work, or overheats, reduce your controllers output, or upgrade to a bigger supply. Nothing lost to test it out at least.

Do you have a generator? If so, a 30A shore power charger could be a good backup. For just a few weeks of traveling, you should be fine. I would suggest doing a bit of testing to see how much power the heater uses to keep the unit warm.
 

luthj

Engineer In Residence
Why do “overlanders” always want to complicate simple things?
12v-36v-12v just to charge some batteries? Ok.


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Because it works well. This method, when implemented properly, basically makes a DC-DC charger at a fraction of the cost. You get a 3 stage profile at the right voltage. In this case we are looking at ~20-30A charge rates. Because the charger can output the absorb voltage (14.5V or so), then this charge rate can be maintained until about 85% SOC, which allows for much faster charging when driving. It takes advantage of the already existing solar charger, thus removing unnecessary secondary equipment in some cases.

This type of DC-DC method (or the 12-120-12V method), is the only way to get decent charge rates from a ~14V alternator to a trailer or distant house battery. Many vehicles have lower voltage alternators for efficiency reasons, and can't charge a lead acid battery even on the best of days (~13.6V in some cases).
 

Bayou Boy

Adventurer
He will already have solar to top it off. A simple 12v charge line will blow through bulk stage quickly without a cheap converter box in the way to fail.

It just isn’t necessary with the solar setup installed and adds another thing to break.

And a $30 no name Alibabba converter WILL break.


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luthj

Engineer In Residence
The solar will do a good job if there is sun. But there isn't always sun, especially in the shoulder seasons, or in the far north. Sometimes you need a bit of a boost, and 20A from a short idle can be a big deal.

You would be hard pressed to get even 10A through a 8 or 6AWG run over that distance. Especially with connectors etc.

Hopefully he will test the converter well. Assuming he doesn't run the unit at the max output, it could live a long life. I have used many products in that price range with good results. Just take the ratings as the max, not the continuous. If it does fail, he can source a better unit. Or just revert to the previous wiring scheme.
 
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