I need help with sizing the solar fuses, wiring, and mppt controller.

[cadillackid]

with all this, how do I truly track how much im using? in essence is there a way i can see what the SOC is in my batteries without having to let them rest 4 hours? I have a bank of 2 group 31 AGM (sold as deep cycle marine batteries).. I use them every day and charge them by either alternator or portable solar panel every day..



is there a device or simple Quick method for getting a reasonable idea of SOC wothout the rest period?



the portable solar panel I have came it its own charge controller that does have you input the battery type (it only charges 12 volt).. but doesnt give me really any SOC info on its display..



is there a monitor device I can attach to the batteries that will give me a devent idea where I am? im not looking to build a permanent solar solution. and the alternator is the primary means of charging siomply because its whats there and the batteries are designed for such being rated as marine / automotive type batteries.. my little solar panel is really juist an experiment and now that we are past the equinox in ohio and heading into the cloudy season it really doesnt give a whole lot of output any more..

[Drew Bru]

Originally Posted by cadillackid

with all this, how do I truly track how much im using? in essence is there a way i can see what the SOC is in my batteries without having to let them rest 4 hours? I have a bank of 2 group 31 AGM (sold as deep cycle marine batteries).. I use them every day and charge them by either alternator or portable solar panel every day..



is there a device or simple Quick method for getting a reasonable idea of SOC wothout the rest period?



the portable solar panel I have came it its own charge controller that does have you input the battery type (it only charges 12 volt).. but doesnt give me really any SOC info on its display..



is there a monitor device I can attach to the batteries that will give me a devent idea where I am? im not looking to build a permanent solar solution. and the alternator is the primary means of charging siomply because its whats there and the batteries are designed for such being rated as marine / automotive type batteries.. my little solar panel is really juist an experiment and now that we are past the equinox in ohio and heading into the cloudy season it really doesnt give a whole lot of output any more..

There's lots of battery monitors on Amazon, from 15 bucks to a few hundred. We've got a Victron, though I've got another brand on the way as the Victron has crapped out twice now. They're easy enough to install and give a pretty good snapshot of the SOC. One thing I'll say for Victron, they've got a pretty slick app (if you get the bluetooth dongle) that lets you track usage over time. I don't find it necessary, but it's perfect for people who nerd-out on data.

[cadillackid]

sweet thanks! the victron looks exactly like I want.. something wit ha shunt that is monitoring usage and charge too.. cool deal!



ivwe never really monitored anything with the batteries just used them and thus far they havent been "dead".. but now that im actively using power for heat and work.. and have my Telematics / remote control in test I need to keep an eye on my house batteries.. they no longer just sit there like they did for 4 years..

[dzl_]

Originally Posted by srponies

Thank you so much for all of the information here.

On the output side of the controller - I used the wire size calculator.. 78amps, 12 volts, and 96" of cable.. Looks like 4/0 cable is just out of the Excellent category. I can't get the charge controller any closer than 4-5 ft from my batteries.

Something is wrong here. I suspect you used inches where you should've used feet and the charge controller misinterpreted it. 4/0 is waaaay more than you need for that current and distance. Based on the numbers you stated above, anything under 6 AWG would be good, my choice would be 2 AWG to keep voltage drop to 1%, but I'm anal and hate inefficiency, anything under 3% is good.

Should I run a longer cable from the roof, to get the output cable as short as possible?

Probably, yes. As general rule, you should try to make your longest wire runs the ones that are the lowest amperage and highest voltage, because this minimizes losses and is more efficient from a wiring standpoint (in dollars and in Volts).

I had planned to cable from the charge controller, through a circuit breaker/fuse, to my buss bar. And the cable from my buss bar to the batteries is 4/0.

This is reasonable, just locate these components close to one another if possible.

[dzl_]

Originally Posted by cadillackid

with all this, how do I truly track how much im using? in essence is there a way i can see what the SOC is in my batteries without having to let them rest 4 hours?

Victron BMV, Victron SmartShunt, and AiLi (shameless Victron Knockoff that costs <1/2 the price) will do the trick. All are shunt based battery monitors that are pretty accurate at calculating SoC. The Victrons also play well within their ecosystem and enable some additional capabilities and functionality when combined with other Victron gear, and the Victron BMV has a configurable relay output that opens up many cool possibilities if you like to get creative (which I know you do).

[cadillackid]

I went ahead and ordered the victron.. I know there are knockoffs.. but they have a lot of neat integrated items so if at some point it goes beyond monitoring the SoC of the bank im ready to explore..


thanks for the tip on the relay.. I didnt see it on there.. and its huge.. as id Liek to have the telematics shut down when the SoC is critical..

[john61ct]

Originally Posted by srponies

I can't get the charge controller any closer than 4-5 ft from my batteries.

Why not?

Buy cable to satisfy the design, **not** design around cable cinsiderations.

> Should I run a longer cable from the roof, to get the output cable as short as possible?

Absolutely, SC right next to battery - just not directly above for FLA, fumes corrode.

> I had planned to cable from the charge controller, through a circuit breaker/fuse, to my buss bar.

No, the SC output (all quality charge sources) must go direct as possible to the battery posts, to get accurate voltage reading.

A BM shunt, and an emergency bank isolation switch or CB are possible exceptions.

[john61ct]

Buy your Victron gear from an authorized dealer that provides good support. Ideally local to you.

Not based on price.

[john61ct]

Merlin SmartGauge (sold by Balmar in NA) is the most accurate BM and much easier to install and operate.

Lead only, SoC% and voltage only, not Ah nor amps.

712-BMV is good for the latter, some use both.

[cadillackid]

Originally Posted by john61ct

Merlin SmartGauge (sold by Balmar in NA) is the most accurate BM and much easier to install and operate.

Lead only, SoC% and voltage only, not Ah nor amps.

712-BMV is good for the latter, some use both.

You are saying the 712 only tracks AH used and not SoC of the bank? I thought from reading that it does.
My battery is real simple, 2 interstate group 31 AGM marine / RV / Auto batteries in parallel.. an inverter for 1200vac, Some 12 volt accessories like heater blowers speakers and webasto, an auto isolator to let the alternator charge the bank.
I have a portable foldie solar panel with its own charge controller that I experiment with throwing in the windshield for fun to keep the telematics going.. but I don’t plan a permanent solar install

[dzl_]

Originally Posted by cadillackid

You are saying the 712 only tracks AH used and not SoC of the bank? I thought from reading that it does.

I'm pretty sure he is saying the opposite. The 'merlin smartgauge' he recommended doesn't track Ah or Wh, but the Victron does. At least that is how I read the comment and what I understand about the Victron units, they are Shunt based.

[Drew Bru]

Originally Posted by dzl_

I'm pretty sure he is saying the opposite. The 'merlin smartgauge' he recommended doesn't track Ah or Wh, but the Victron does. At least that is how I read the comment and what I understand about the Victron units, they are Shunt based.

Correct, the Victron is shunt based and tracks AH and and SOC of the battery bank, current flow, etc. We've got the BNV700 but the 712 has options for 2nd battery monitoring and temperature, midpoint settings, alarms, relays, etc.

[john61ct]

Originally Posted by cadillackid

You are saying the 712 only tracks AH used and not SoC of the bank?

No both estimate SoC, SmartGauge does it without measuring current, no shunt, nothing to display but voltage and SoC%, which it usually gets more accurately.

Most other BMs are shunt based, and can display amps and Ah in/out/net as well as V / SoC, just lots more difficult to keep as accurate as possible.

See Maine Sail's three articles at http://marinehowto.com on the topic, Ctrl-F search for

battery monitor

on the home page.


But do not buy Balmar SG200, still a bit hit or miss, grossly so in many cases.

[srponies]

Originally Posted by dzl_

Something is wrong here. I suspect you used inches where you should've used feet and the charge controller misinterpreted it. 4/0 is waaaay more than you need for that current and distance. Based on the numbers you stated above, anything under 6 AWG would be good, my choice would be 2 AWG to keep voltage drop to 1%, but I'm anal and hate inefficiency, anything under 3% is good.

You're correct - I had been using inches in the calculator, not Feet. That will definitely make it easier to wire from the roof to the controller, and the controller to my buss bars.

Steve

[srponies]

Originally Posted by john61ct

Why not?

My batteries are located in a box under the bus. 4/0 cable is connected to them and routed up into the dinette bench where my shunt, positive and negative buss bars are located. I can easily run wiring from the controller to the buss bars in this area.

Steve

[john61ct]

Do it right even if inconvenient

[srponies]

Originally Posted by john61ct

Do it right even if inconvenient

So - Should I connect the negative from the charge controller to my negative buss bar (coming off of the shunt)?

And connect the positive from the charge controller to the battery positive post (routed through a fuse) ?

Doing this would add 4+ feet to the positive run - using 6 gauge wire vs the 4/0 already in place. It would also bypass the shutoff in the battery box, and the 300AMP fuse on the positive terminal (that the 4/0 is connected to).

Steve

[john61ct]

Actually if you really are using 4/0 (???)

then just verify voltage drop is tiny between the SC terminal and battery posts.

That is the usual rationale for going direct from a charge source to post with minimal distance, you want the feedback to be as accurate as possible.

Some have dedicated sensor wires separate from charge current, for that purpose.

But temperature changing the setpoints can also be important, if no dedicated external temp sensor wire, then it is internal to the SC, another reason the SC is meant to be in the same space as the House bank.

[srponies]

Originally Posted by john61ct

Actually if you really are using 4/0 (???)

Yes. 4/0 from the battery to the neg shunt, chassis ground. And to the positive buss bar. And 4/0 to the inverter. 4 ga from buss bars to 12v fuse panel.

Steve

[srponies]

I am looking at what is needed for a rooftop combiner box for my 3 panels. It looks like the ECO-Worthy box on amazon might work. The fuses are 12Amp. And 40amp circuit breaker.

https://www.amazon.com/ECO-WORTHY-Co...2293432&sr=8-2

What are your thoughts?

Thanks,
Steve