wiring solar to batteries

[Colo_Native]

I had a brain fart. I have 2 12 v batteries do I wire the controller to each battery or pos to one neg to other or or to the on that is farthest away for the FW connection ?

[Almot]

pianotuna wrote:
Hi Almot,

The Tristar units do not let out the magic blue smoke when they over load. They simply clip off the excess. (within reason, of course)

TS MPPT, yes, they will clip the output current with no ill consequences, like any other MPPT.

TS PWM will probably let out the magic blue smoke - like any other PWM when exceeding input current limit.

But I was talking here about the 65A "ampacity" rating of #6 wire mentioned by the OP. Wire specs, not controller specs. MPPT will clip (whatever OP would connect to it), so hypothetical max current (hypothetical max because array size wasn't stated) would be limited by MPPT rating = 45A. Wire #6 can safely handle up to 65A.

[pianotuna]

Hi Naio,

Yes you are correct. And it makes a huge difference to lifespan. Besides with two 12 volt jars it doesn't cost a dime more to balance them.

Naio wrote:
I was thinking that the problem is that they don't get charged correctly if they are not balanced at load time. One gets too much or the other gets too little.Is that wrong?

[westend]

N-Trouble wrote:

pianotuna wrote:
Ah but it does matter. The wiring needs to be done so the jars are balanced. See the link posted above and read it.

N-Trouble wrote:
12V are wired in parallel so it doesnt really matter which battery you connect +/- to.

In the case of two 12V batteries under realistic loads (not 100A...) the resistance is going to be negligable in real world use to the point you would never perceive a difference in battery performance.

I don't know how you can ignore the calculations made here. The basic physics and math are true for 100 amps or 10 amps and the balanced method is as easy as any other.

[Naio]

N-Trouble wrote:


In the case of two 12V batteries under realistic loads (not 100A...) the resistance is going to be negligable in real world use to the point you would never perceive a difference in battery performance.

I was thinking that the problem is that they don't get charged correctly if they are not balanced at load time. One gets too much or the other gets too little.Is that wrong?

[N-Trouble]

pianotuna wrote:
Ah but it does matter. The wiring needs to be done so the jars are balanced. See the link posted above and read it.

N-Trouble wrote:
12V are wired in parallel so it doesnt really matter which battery you connect +/- to.

In the case of two 12V batteries under realistic loads (not 100A...) the resistance is going to be negligable in real world use to the point you would never perceive a difference in battery performance.

[pianotuna]

Hi Almot,

The Tristar units do not let out the magic blue smoke when they over load. They simply clip off the excess. (within reason, of course)

[Almot]

Colo Native wrote:
it is 45A Mppt and the run is under 3'. it said wire is rated 65 amps

65A is the wire ampacity, i.e. the current when cable starts "deteriorating", whatever it means. I assume this is when insulation is getting soft and/or melting away.

45A MPPT doesn't mean much without knowing the array size. This is why I asked about "max post-controller current" - meaning in YOUR particular situation.

Anyway... even if you install 600W array and manage to max your controller up, 45A current in #6 cable @3ft length will result in 0.9% voltage drop, this is within the norm. 45A is within the norm of cable ampacity as well.

I would be (a little) worried about 45A being that close to 65A "point of destruction", but let professional electricians comment from practical experience, I'm not the one.

[pianotuna]

Ah but it does matter. The wiring needs to be done so the jars are balanced. See the link posted above and read it.

N-Trouble wrote:
12V are wired in parallel so it doesnt really matter which battery you connect +/- to.

[red31]

thanks PT for load of info @ smart gauge, unbalanced 2 parallel still persists.

A simple lead change of 2 7ah gate opening batteries and now they last a long time. Balanced is nice.

[N-Trouble]

12V are wired in parallel so it doesnt really matter which battery you connect +/- to.

[pianotuna]

Naio,

That link should be required reading. There are a whole bunch of other topics there that are useful. And there is even a Peukert Calculator to download.

[Naio]

scrubjaysnest wrote:
X 3 reference here: battery wiring applies to solar as well as batteries

Nice link!

[Colo_Native]

Almot wrote:

Colo Native wrote:
One more question do you think 6awg is enough to go from controller to battery, I have a lot left.

What is post-controller max current and what is one-way cable length?

it is 45A Mppt and the run is under 3'. it said wire is rated 65 amps

[Almot]

Colo Native wrote:
One more question do you think 6awg is enough to go from controller to battery, I have a lot left.

What is post-controller max current and what is one-way cable length?