DIY Solar Plans - Is this a safe setup?

[Solar User]

Hello all,

I am relatively new to solar power projects and I just wanted to see if anyone with a little more experience saw any issues with my diagram. I am wanting to get a Victron 150/45 Tr set up to charge batteries (I have several 12.8V, 100 Ah batteries). I inserted bus bars and used heavier guage wire from the battery so that I could add on a 2000 watt inverter and some other items at a later time. Just wanting to get any opinions before spending money on all of the components to build the setup. Thanks for any input.

 

[Hedges]

Thermal fuse/breaker should be 125% of max continuous current. (Magnetic/hydraulic doesn't need as much margin.) So 45A SCC ought to have 60A minimum OCP. Avoid cheap ones that may overheat and not actually work at their rating.

 

[DIYrich]

Wire the battery in series to up the voltage.

 

[Solar User]

Thanks for the suggestions. I have wired the batteries in series to get 24 Volts in the past but was not sure if the individual components would allow me to go much beyond that. Regarding the 60A minimum - That is also good to know. Would this product work - https://www.amazon.com/gp/product/B07PBGMMNZ/ref=sw_img_1?smid=ALHXFZX1L0DAX&th=1

 

[Hedges]

I think Blue Sea is (much!) more highly regarded than T-Tocas

285-Series - Blue Sea Systems

Thermal circuit breakers provides medium duty circuit protection for 25 to 150 Amp loads when switching and circuit protection are both required.

www.bluesea.com

But that is still a thermal-only breaker, slow trip.
Some are thermal-magnetic, some magnetic-hydraulic.
Look for non-polarized breakers.


Are your batteries lead-acid, or LiFePO4?
I see you have 200A fuse on the terminal.
There should be OCP that has AIC rating as high as short-circuit current of battery, at the operating voltage.

 

[Solar User]

I think Blue Sea is (much!) more highly regarded than T-Tocas

285-Series - Blue Sea Systems

Thermal circuit breakers provides medium duty circuit protection for 25 to 150 Amp loads when switching and circuit protection are both required.

www.bluesea.com

But that is still a thermal-only breaker, slow trip.
Some are thermal-magnetic, some magnetic-hydraulic.
Look for non-polarized breakers.


Are your batteries lead-acid, or LiFePO4?
I see you have 200A fuse on the terminal.
There should be OCP that has AIC rating as high as short-circuit current of battery, at the operating voltage.

Thanks for the suggestion on the breaker. I found this one available on Amazon https://www.amazon.com/gp/product/B004XXOW0E/ref=sw_img_1?smid=ATVPDKIKX0DER&th=1. I have multiple 12.8V 100Ah LiFePO4 batteries if that provides additional food for thought.

 

[Hedges]

"

Interrupt Capacity

3000A @ 48V

"

Not sure what it would be at lower voltage.

285-Series Circuit Breaker - Surface Mount 60A - Blue Sea Systems

Thermal circuit breakers provides medium duty circuit protection for 25 to 150 Amp loads when switching and circuit protection are both required.

www.bluesea.com

Lithium batteries can put out massive current. 3000AIC should be enough for lead-acid but not lithium.
But your fuse should take care of this. Which 200A fuse, what ratings?

 

[Solar User]

I was planning to bolt one of these to the battery https://www.amazon.com/gp/product/B000MMDL9I/ref=ox_sc_act_title_11?smid=ATVPDKIKX0DER&th=1.

 

[Hedges]

"

Interrupt Capacity

2000A @ 32V DC

"

MEGA® / AMG® Fuse - 200 Amp - Blue Sea Systems

Use with MEGA or AMG fuse blocks to create an economical system for 100 to 300 Amp circuit protection

www.bluesea.com

Not high enough for a lithium battery, where short-circuit current might be several times higher. The fuse might just sit there arcing.

Determine what short-circuit current the battery (or battery bank) could deliver and look for a fuse rated at least that high.

I made an estimate based on cell IR spec, don't know if anyone has actually measured.

Here was a momentary short:

Oops - I shorted out a 48V/400Ah Lifepo4 battery

This was back in 2021 - I managed to short out a LifePo4 pack (before my coffee kicked in). This happened in the process of dismantling a LifePo4 48V/400Ah battery in order to replace it with another battery. I didn't think about the fact that the pack was still live while unscrewing the nuts...

diysolarforum.com

 

[Solar User]

Very interesting reading about that short circuit situation. Don't ever want to experience that. It looks like this is the information I found on the battery if it helps

 

[Solar User]

By the way, I really appreciate you sharing your technical expertise on this as I am learning quite a bit on the practical side of things.

 

[Hedges]

They probably claim BMS provides short circuit protection, but I don't think I'd trust silicon to do the job of a fuse.

If a LiFePO4 cell is 3.4V and has 0.17 milli-ohms resistance, I come up with 20,000A fault current.
four or 16 cells in series, some wire resistance reduces current a bit ...
The actual behavior of the cells may be less than that.

I have class T fuses for my 400 Ah AGM bank. other people use them for lithium banks.
When you connect a larger inverter, you need a precharge circuit or the inrush will blow a fast fuse. Which proves the BMS allows massive amps through.

There are also breakers rated for very high AIC.

Nothing is cheap, but we try to be safe.

 

[Hedges]

Hopefully others with experience using those or similar batteries jump in. I'm using AGM, backup purposes not daily cycling.

You can read about fuses & breakers, and maybe your batteries, by searching the forum.

 

[Solar User]

Hopefully others with experience using those or similar batteries jump in. I'm using AGM, backup purposes not daily cycling.

You can read about fuses & breakers, and maybe your batteries, by searching the forum.

Thanks for all of the information. I had done some reading regarding fuses and even posted a question or two to several boards but never received a response so this information was very helpful. I had heard about using a resistor to charge the capacitors in an inverter (and even saw where people had used light bulbs for this purpose). I think they were trying to avoid the sparking when connecting things up but I thought that the on/off disconnect switch would take care of that issue. I tried to find T Class fuses (and was not even sure what they were) and I found this one a while back but thought it might not be as good since I would have to have some length of wire between the battery terminal and the fuse (as opposed to a direct connection). I was thinking that it would also allow me to safely connect four batteries in series to get 48V but then realized that most of the other components I was looking at were not rated for those voltages. https://www.amazon.com/gp/product/B001539B60/ref=ox_sc_saved_title_9?smid=ATVPDKIKX0DER&psc=1

 

[gotbeans]

missing ground

 

[Solar User]

missing ground

Good catch. Where does the ground wire run. Would it be off of the negative busbar to a ground rod connection?

 

[gotbeans]

Good catch. Where does the ground wire run. Would it be off of the negative busbar to a ground rod connection?

is your system off grid? it looks off grid
no don't connect ground to negative, it's an entirely different circuit that should have nothing running on it as long as everything is running correctly.
It's a "safety" circuit..
the ground is the most complex and posted about on this forum
basically you want your array FRAMES themselves connected to a grounding wire that runs back to your victron solar charge controller and ties to the ground there.
You want the charge controller connected to the ground of everything else too...

The idea of ground is mostly if stuff goes wrong that you physically touch, it'll be "hot" and thus blow a breaker or fuse somewhere instead of blowing your arm off

I've read probably 100 threads or so on this subject
You can see how intense of a topic it is. This thread has 7 pages and it's only 1 day old lmao

Multiple grounding rods for solar panel install and electrical devices?

Hello all, My apologies forthcoming if this question has been asked and answered elsewhere I was just wondering if I should use two separate grounding rods for my installation? One for my solar panel array wired in series and the other to the power shed I built to house the battery bank...

diysolarforum.com

on top of that, basically 100 other threads already exist just like it

 

[DIYrich]

Class T fuse should be close to the battery.

Blue Sea switch is rated for max 48v, so can be used for up to nominal 36v system. 24v system would halve the amperage. 2000 watts is 170 amps at 12v, 90 amps at 24v, and 60 amps at 36v (allowing for some conversion losses).

At 12v you will be near the max of the Victron charge controller. At 24v and 36v, you will have room to add more panels.

 

[Solar User]

The setup will be off grid. I have had quite a bit of experience with several different types of manufactured solar stations but I decided I wanted to test the waters of a diy station so I was able to get some batteries. At the least, I would like to be able to solar charge the batteries without having to use the manufactured stations (hence this post) but I would ideally like to add an inverter and possible some 12V USB plugs so that I can power some 12V stuff. Very interesting information on the ground setup - It sounds like I have a lot to learn on that topic alone. Regarding the T Class fuses, would this fuse https://www.amazon.com/Blue-Sea-511...ms+200+amp+T+class+fuse&qid=1703178673&sr=8-2 and this holder https://www.amazon.com/Blue-Sea-Sys..._qYOhgwMV00dyCh0xrQ9kEAQYByABEgKsS_D_BwE&th=1 work for my purposes? Also, if I do eventually get a 2000 watt inverter, would I also need a Class T fuse between the bus bar and the inverter or would I simply be able to use the one that I referenced initially. Thanks again for all of the help as this thread has provided the most helpful information on this forum so far.

 

[gotbeans]

Yea blue sea seems to be one of the highest rated brands
You can connect the fuses directly to the battery terminals / bus bars too
You may see the blue sea one made by "littlefuse" when you read the wrapper on the fuse itself. That is pretty normal so don't worry there.