Check my design, please - another DC\DC Aux battery

[SirDrinksalot]

Good afternoon,

I hope you can cast your eyes over this and advise. The only things i have bought are a Thunder 20A DCDC charger: https://batteryalltypes.com.au/Thunder-20A-DC-DC-Charger-p307426640

Well it was a gift. I have some 4B&S. (2x10m red and black).

My intention was to go straight from the starter battery with both positive and negative rather than earthing for the DC/DC and Aux Battery, I might earth the solar panel to the chassis, unless there is a recommended way to join and split 4B&S.

Unit says minimum 30A breakers, should I stick to minimum, i suggested 50 here and 30 between the charger and the AUX as its a 20A charger, I would be happy to go all 30As. Is the one needed on the Earth cable, the schematic says not but i think i read somewhere its not a bod idea.

Look forward to your feeback, thank you.

 

[CTL]

Just follow the wiring suggestion from the DCDC. Put the DCDC as close as possible to the auxiliary battery and a fuse near each battery. No need to fuse the solar positive. 4B&S is overkill for the solar cable. No need for a fuse on the negative cable.

 

[boobook]

The first diagram called Wiring setup is incorrect. It shows a circuit breaker on the negative of the main battery and positive has a circuit breaker but goes nowhere.

 

[Petunia]

recommended way to join and split 4B&S.

Terminate [as in use terminals] to a 'thingy doohicky' which is two bolts insulated from metal and joined by a bar that will allow a therd terminal to be attached.

Unit says minimum 30A breakers, should I stick to minimum

YES, you should, 20amp being generated drawn or magically made by alchemy ...... so if you use 50 amp breakers the currant can rise to just past 50 amps before it breaks the circuit, 50 into a 20 unit does not compute well

Is the one needed on the Earth cable

No !

No need to fuse the solar positive.

I disagree.
I fuse ALL my panels at the panel, when the sun shines, they make power
an analogy -: the cable is rubbed through after several years on corrugated roads it earths out one night, next day you have a power source pumping gas down that cable to short on the earth ... of course nothing will happen, like

4B&S

you got 4 use 4 ... why not you got it use it if you so desire

positive has a circuit breaker but goes nowhere.

One reads between the lines, it will go somewhere eventually, its just a ''simple'' diagram not a engineers drawing!

 

[SirDrinksalot]

Just follow the wiring suggestion from the DCDC. Put the DCDC as close as possible to the auxiliary battery and a fuse near each battery. No need to fuse the solar positive. 4B&S is overkill for the solar cable. No need for a fuse on the negative cable.

Thank you, I was only going to use the 4B&S between the battery and the DCDC as it will run from the Hilux bonnet to the back of the ute tray. I hadnt even thought about the solar wire, will get something smaller as it will run down the back of the cab into the tray so probably would look agricultural and not fit through any existing grommets anyway.

The first diagram called Wiring setup is incorrect. It shows a circuit breaker on the negative of the main battery and positive has a circuit breaker but goes nowhere.

Yes my bad, it will go from the breaker to the DCDC.

Terminate [as in use terminals] to a 'thingy doohicky' which is two bolts insulated from metal and joined by a bar that will allow a therd terminal to be attached.


YES, you should, 20amp being generated drawn or magically made by alchemy ...... so if you use 50 amp breakers the currant can rise to just past 50 amps before it breaks the circuit, 50 into a 20 unit does not compute well


No !


I disagree.
I fuse ALL my panels at the panel, when the sun shines, they make power
an analogy -: the cable is rubbed through after several years on corrugated roads it earths out one night, next day you have a power source pumping gas down that cable to short on the earth ... of course nothing will happen, like


you got 4 use 4 ... why not you got it use it if you so desire


One reads between the lines, it will go somewhere eventually, its just a ''simple'' diagram not a engineers drawing!

Thank you, I can see your thingy doohicky, like a bussbar thing?

Not against fusing the panels, someone said it would keep blowing IIFC, its a Kings 160w panel, not the best but its what I could afford: https://www.4wdsupacentre.com.au/pr...os/new-product-160w-fixed-solar-panel-v3.html

Says this on the website:

The individual solar cells are grade A monocrystalline for high power output. Capable of up to 10.01A of charge, connect to a DC-DC Charger or MPPT regulator (available separately) to get up to 12.8A of charge out of the 160W Fixed Solar Panel and make the most of free power from the sun!

So should I fuse it at 12.8A (if there is such a fuse)?

I bought 1 x 30A breaker for between the starter battery and the DCDC and a 20A one between the DCDC and the AUX.

Thanks for the advice.

 

[Petunia]

like a bussbar thing?

Yeah, bus bar .... i was saying bus bar to myself then didn't type it

So should I fuse it at 12.8A (if there is such a fuse)?

panel will put out up to 12.8 ....... so you give it a bit more, go to 15A [there is no 12.8 they come in 5, 7.5, 10, 15, 20, 25, 30] if it consistently blows 15's you may wish to go to 20? provided you check that its not a short blowing the fuse and infact the panel is producing more than 15A? [but i doubt that]

if your 20A breaker trips [between dc/dc an aux 20 amp dcdc 20 amp breaker may or may not trip? I would have gone a 25A breaker

for future reference add 5a to what any instructions say a ''thingy'' is or round it up to the nearest next one

You are Welcome

 

[SirDrinksalot]

Yeah, bus bar .... i was saying bus bar to myself then didn't type it


panel will put out up to 12.8 ....... so you give it a bit more, go to 15A [there is no 12.8 they come in 5, 7.5, 10, 15, 20, 25, 30] if it consistently blows 15's you may wish to go to 20? provided you check that its not a short blowing the fuse and infact the panel is producing more than 15A? [but i doubt that]

if your 20A breaker trips [between dc/dc an aux 20 amp dcdc 20 amp breaker may or may not trip? I would have gone a 25A breaker

for future reference add 5a to what any instructions say a ''thingy'' is or round it up to the nearest next one

You are Welcome

I might be lucky, just checked my Amazon purchase history and only the bus bar is in there, maybe my breakers didnt work!

Thanks again for your advice, much appreciated.

 

[Method]

I would go with whatever the manuals recommend in terms of fuses. From memory I think I have a 30A or 40A fuse on my DC charger which is 30A and a 50A near the main battery on the positive lines. No need for fuses on the negatives. Also in terms of joining the cable, you could use a busbar (I used one to join some negatives in my setup as I just attached them directly to my box). For the positives, I joined my cables using a bolt and contact/compression and spring washers. I used junction boxes to insulate and fix the lines in place.

 

[SirDrinksalot]

The wires out of the DCDC are much smaller diameter of my 4BS so I want to connect them via the busbar and the breaker. ie, 4BS in and straight into the DCDC wires it comes with.

Having a larger wire diameter for the run from the bonnet (under the hood y'all) and then connecting to a smaller diameter thats coming out of the DCDC, is that an issue?

If I cant fit the busbar and breaker and output breaker direct to the DCDC output wires I am going to have to extend them with another wire, probably not 4BS as its pretty stiff, I will try and match the wires there, is that an issue?

 

[Method]

No issue at all. I have 000 and 00 reducing down everywhere, I think I even used 0000 for my main run. Welding cable is your go to as it's highly flexible. I've attached an image to give you an idea of how different sizes are no issue if connected well.