diy solar

diy solar

Is my system safe?

Austin92

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Joined
Dec 26, 2023
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21
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Indiana
I built this little 12v system to have some usable power during an outage and maybe run my tv/router/etc for free year round. I have not slid it into its permanent home and hooked up the single 250w rich solar panel I have yet, but I have used the 20a plug in charger I got incase my bank is low and I know a storm is rolling in. First question starts there, what voltage should it be charging to? I unplugged it when the shunt said 13.5v. On the other side of that, when should the Bms trip the low voltage disconnect? They are li time 100ah batteries and I stopped the test at 10.8v. Li time shunt and charger, voltage verified with multimeter.

Just recently got this set up complete and during that testing I noticed a few things getting warm. The 300a anl fuse gets the hottest (170f+) and the temp spreads from there. The 250a breaker gets warmer than the inverter cables. Buss bar is from a car audio place, nickel coated copper and rated for 600a, switch is a 350a blue seas, plan to add a back up bank down the road. Everything between the battery bank and bus bars is 2/0 and only the wire close to the fuse gets warm. It is 1/0 between each battery and from the bus bars to inverter, all ofc, no cca wire in my system.

The small blue seas fuse thing runs a little 2-3a battery charger and usb distribution block, will add a couple 12v LED’s eventually.

Should I up any wire sizes or swap for a different kind of fuse? Any other suggestions/feedback on my set up? Plan to add more panels and run a cable out that I can hook up to my truck if you’re wondering why I have that charge controller.
 

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Just recently got this set up complete and during that testing I noticed a few things getting warm. The 300a anl fuse gets the hottest (170f+) and the temp spreads from there.
Concerned about that temp. What current were your drawing? Suspect poor connection around the fuse, rather than the fuse itself, IMHO, but I'm no expert on 12V systems.

Only other comment would be to put insulated cover over the +ve bus bar and fuse, once the temp issues are resolved. Looks too easy to short between +ve and -ve with a wrench or similar on that end panel, which wouldn't be good if it was shorted the wrong side of the ANL fuse.
 
I built this little 12v system to have some usable power during an outage and maybe run my tv/router/etc for free year round. I have not slid it into its permanent home and hooked up the single 250w rich solar panel I have yet, but I have used the 20a plug in charger I got incase my bank is low and I know a storm is rolling in. First question starts there, what voltage should it be charging to? I unplugged it when the shunt said 13.5v. On the other side of that, when should the Bms trip the low voltage disconnect? They are li time 100ah batteries and I stopped the test at 10.8v. Li time shunt and charger, voltage verified with multimeter.

Just recently got this set up complete and during that testing I noticed a few things getting warm. The 300a anl fuse gets the hottest (170f+) and the temp spreads from there. The 250a breaker gets warmer than the inverter cables. Buss bar is from a car audio place, nickel coated copper and rated for 600a, switch is a 350a blue seas, plan to add a back up bank down the road. Everything between the battery bank and bus bars is 2/0 and only the wire close to the fuse gets warm. It is 1/0 between each battery and from the bus bars to inverter, all ofc, no cca wire in my system.

The small blue seas fuse thing runs a little 2-3a battery charger and usb distribution block, will add a couple 12v LED’s eventually.

Should I up any wire sizes or swap for a different kind of fuse? Any other suggestions/feedback on my set up? Plan to add more panels and run a cable out that I can hook up to my truck if you’re wondering why I have that charge controller.
13.5 is a good charging voltage for 12v
Look into your battery spec for low cutoff. I would imagine in the 10.5v range
Fuses get warm, but not usually that warm. Check connection tightness.

What kind of amperage are you running through this whole system? That will tell you what size wire you need. If you're peaking at 300A and holding there, 2/0 might be a smidge too small.

This mostly looks good. A few callouts.

This tiny wire should be fused as a just in case. (I say tiny, white's probably 6ga, red is probably 10-12ga)
You can fuse to a smaller bus bar and put the smaller items in that bus or get a small fuse block.
Do you have something to cover these bolts with to prevent accidental shorting? A Company named Recoil makes covers you can put on the ring terminal themselves that would cover the nuts.
1711121060231.png

Looking closer, this looks like a fuse block? Should connect the smaller wires there.

1711121479149.png
 
Most 12 volt warm issues are caused by to small of wire size for the load or an improper/faulty conections.

How did you crimp the conections?
What size is your inverter?

Do you realize a 200 watt solar panel is woefully under sized for this system?]

I would be concerned about the 171F fuse temperature.
 
Concerned about that temp. What current were your drawing? Suspect poor connection around the fuse, rather than the fuse itself, IMHO, but I'm no expert on 12V systems.

Only other comment would be to put insulated cover over the +ve bus bar and fuse, once the temp issues are resolved. Looks too easy to short between +ve and -ve with a wrench or similar on that end panel, which wouldn't be good if it was shorted the wrong side of the ANL fuse.
Yes I definitely plan to cover them, keeping the switch off for now when I’m not testing. I have double and triple checked for loose connections, that was my first thought.

I was using a variable heat gun and space heater to keep it just under tripping my inverter, not a real world scenario but still wanted to test to the limit. The shunt showed 155a at 1.9kw
 
It is a 2000w pure sine from harbor freight. I should have included that, thank you!
Honestly im more concerned about the 250 breaker than the ANL fuse. Those style breakers seem to have high failure rates.

The fuse is warm because its a choke point for current, but thats how they work, too much current for a period of time, fuse blows ( burns in half essentially). Temperature will be relative to its fuse rating.
 
13.5 is a good charging voltage for 12v
Look into your battery spec for low cutoff. I would imagine in the 10.5v range
Fuses get warm, but not usually that warm. Check connection tightness.

What kind of amperage are you running through this whole system? That will tell you what size wire you need. If you're peaking at 300A and holding there, 2/0 might be a smidge too small.

This mostly looks good. A few callouts.

This tiny wire should be fused as a just in case. (I say tiny, white's probably 6ga, red is probably 10-12ga)
You can fuse to a smaller bus bar and put the smaller items in that bus or get a small fuse block.
Do you have something to cover these bolts with to prevent accidental shorting? A Company named Recoil makes covers you can put on the ring terminal themselves that would cover the nuts.
View attachment 203697

Looking closer, this looks like a fuse block? Should connect the smaller wires there.

View attachment 203700
I would say the most this system would ever see continuous would be around 200a, saw Will’s video that recommended fuse/breaker 1.5 times expected continuous and to go up if there’s nothing directly at your calculation.

The small white/black is 8ga from my charge controller and has a breaker on it, it’s the 60a one. The red/black is 10ga and is the factory size that came with my Li time 20a plug in charger, the grey plug is factory too and in their instructions it says not to cut, splice, or change wire length any way. The little fuse block up top is for distribution of wires for things I add that’s 12v, it is the other set of 8ga coming off the bus bar and has a 100a breaker.

Do you still think I need to fuse a smaller bus?

Thank you for pointing out the recoil terminal covers

Here’s a little better lighting photo
 

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Most 12 volt warm issues are caused by to small of wire size for the load or an improper/faulty conections.

How did you crimp the conections?
What size is your inverter?

Do you realize a 200 watt solar panel is woefully under sized for this system?]

I would be concerned about the 171F fuse temperature.
This is the tool I’m using to crimp, running it down with an impact, not by hand. My inverter is 2000w.

I am aware my one 250w panel isn’t enough, that is why I made sure to show that it’s a 50a charge controller dc-dc with mppt. I’ll have plenty of charger left for 3, maybe 4 panels in the end as money allows me to add them and if there is a storm that knocks out the power for a few days I can run the dc-dc hook up out to my vehicle when the panels aren’t keeping up. Vehicle back up was the main reason for not going 24/48v, don’t have room for many panels with out making mowing or turning around a nightmare.

I too am concerned about the fuse temperature, it was the reason I made this post. I will probably never run the system that hard again but still like to know it’s safe if I have to.
 

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Honestly im more concerned about the 250 breaker than the ANL fuse. Those style breakers seem to have high failure rates.

The fuse is warm because its a choke point for current, but thats how they work, too much current for a period of time, fuse blows ( burns in half essentially). Temperature will be relative to its fuse rating.
Yes, the breaker did get warm also. Is there a cooler safer way to have short circuit protection?
 
2000 watts @ 12vdc gives you +-166 amps.

I would recommend checking out all your connections.

What did you have running when you got the 171F?
How long was it running?
I have gone over my connections many times, that was my first thought too. I was using a space heater and variable heat gun so I could dial right up to the limit of the inverter to test for things like this. They ran for a half hour or so pulling 150-170a
 
Yes, the breaker did get warm also. Is there a cooler safer way to have short circuit protection?
Not without spending $$$. Personally i like ANL fuses for high current low voltage stuff. Although id use Eaton / Bussman brand, hold one in your hand and the difference is clear.
 
Best way to find out if it's the fuse is to remove it and run your test without a fuse in place (temporarily, of course) bolt right to the battery. If nothing gets hot, there's your answer.

I believe torque spec on the mrbf is 110 inch pounds. Not sure about battery
 
Not without spending $$$. Personally i like ANL fuses for high current low voltage stuff. Although id use Eaton / Bussman brand, hold one in your hand and the difference is clear.
That is something else I had thought about doing is ordering a name brand quality anl fuse but I didn’t think that would be the answer to everything. Are there any breakers up to this task? I really like being able to use them as on off switches if current is low.

Someone else mentioned the style I have notoriously go bad…
 
Fuses are better than breakers for lithium short circuit protection. Breakers can weld closed
 
Best way to find out if it's the fuse is to remove it and run your test without a fuse in place (temporarily, of course) bolt right to the battery. If nothing gets hot, there's your answer.

I believe torque spec on the mrbf is 110 inch pounds. Not sure about battery
Will definitely have to try that! What is the mrbf?
 
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