Need help with solar / house power system

[AlleyCat67]

Maybe I'll give this one a go.... a few bucks more but it's a name I know.

Briggs and Stratton 2000 Watt Generator

[WhiteWhale]

Originally Posted by Iceni John

A 60A MPPT charge controller can provide a maximum of 60A into the batteries, regardless of battery system voltage. If you have a 12V battery system it can provide about 888W (60A x 14.8V); if you have a 24V battery system it can provide twice that wattage at the same 60A maximum current.

A 600W PV system will not usually produce 600W of electrical power - it will typically produce a maximum of about 3/4 of that under most conditions, i.e. you will see about 450W from the panels most days. 450W divided by 14.8V battery charging Absorb voltage (needed for Trojan T-105 batteries in a 12V system) is about 30A, less the CC's own inefficiencies that will drop its output to just under 30A. In other words, your 60A CC is able to be powered from a lot more than 600W of panels. I have two Morningstar TS-MPPT-60 CCs that are each fed by 1020W of panels, and each CC charges four golfcart batteries in series/parallel at about the maximum recommended charge rate 0f 13%. FLA deep-cycle batteries should ideally be charged at between 5 to 13% of their 20-hour Ah rating.

Don't forget to keep all your DC cables short and fat to minimize voltage loss under load. If you need further good advice, it's worth your while to read the Northern Arizona Wind & Sun forum - there's enough expertise and experience there to answer any questions you may ever have.

John

I have a second phase of the same question. The 2000 watt AIMS inverter/charger I purchased ( 2000 Watt Pure Sine Inverter Charger ) says is puts out a charge rate of 70 amps. The VMAX 155AH batteries I purchased ( https://www.vmaxtanks.com/SLR155-AGM...ery-_p_66.html ) say they have charging current of 10-35 amps. Is this a problem? Does the number of batteries effect this at all? I currently have 3 of them.

Thanks!

[Blkjacksabbath]

Check out a post I saw on Reddit. Not directly solar related, but any power reducing hacks may help with a solar-battery setup.


"First one that has actually helped in several ways: If you have an add-on TV that you need an inverter for, check the plug. A lot of the generic TVs actually just take the 120V in the power brick and convert it back into 12V power. By wiring directly into a 12V plug I bought from radio shack, I was able to power my TV directly from DC, saving an ugly inverter's noise and overhead. I also believe (though I didn't measure it) that the TV even uses less power than it did before, though it could just be that I had a really inefficient inverter."

https://www.reddit.com/r/GoRVing/com...best_rv_hacks/

[WhiteWhale]

How do I regulate between solar charger and Inverter/Charger? Do I need to put in a switch to isolate so that both arent charging batteries at the same time? I guess it would be easy enough to shut off solar when using inverter charger but I wouldnt really ever want to shut off the inverter charger side considering it also is providing the 12v power source to the inverter to go to AC....

[AlleyCat67]

The way you'll want to set it up is have the AC from shore or generator feeding thru a breaker in your main load center to the AC IN connection on the inverter/charger, with the AC OUT wired to a transfer switch with the other side of the switch connected to another breaker in the main load center, and the output of the transfer switch feeding a subpanel which will power your inverter loads. The transfer switch will feed the subpanel with shore or generator when available, and only pull from inverter when necessary.

All shutting the charger side of it down does is stop the charge function. As long as the inverter is switched on it will produce 120VAC power as needed, up to the power limit of whatever model you're using. When you're connected to shore power the charge side will keep the batteries topped off so there wouldn't be any need to charge from the panels, though of course there's nothing that says you can't keep the charger side turned off and continue charging from solar.

[WhiteWhale]

Originally Posted by AlleyCat67

The way you'll want to set it up is have the AC from shore or generator feeding thru a breaker in your main load center to the AC IN connection on the inverter/charger, with the AC OUT wired to a transfer switch with the other side of the switch connected to another breaker in the main load center, and the output of the transfer switch feeding a subpanel which will power your inverter loads. The transfer switch will feed the subpanel with shore or generator when available, and only pull from inverter when necessary.

All shutting the charger side of it down does is stop the charge function. As long as the inverter is switched on it will produce 120VAC power as needed, up to the power limit of whatever model you're using. When you're connected to shore power the charge side will keep the batteries topped off so there wouldn't be any need to charge from the panels, though of course there's nothing that says you can't keep the charger side turned off and continue charging from solar.

What you are saying makes sense, but I am still not sure how I would/should protect my solar/charge controller from the charge output coming from the inverter when using the inverter to charge the batteries.?

[AlleyCat67]

You have a couple of options..... the simplest is to find a transfer switch rated for the voltage and amperage of the higher charge current (solar or inverter).... wire the solar charge controller to the NC contacts and the inverter to the NO contacts. This way the solar charge controller is connected to the batteries until the inverter charger is activated, then the transfer switch cuts over to that, electrically isolating the solar controller from the battery bank.

You could also find a charge controller that will handle multiple inputs and connect both solar panels and inverter charger output to it, and let it regulate charge current, or use multiple charge controllers that will talk to one another (they are available but costly).

Another choice, though somewhat less desirable, is to connect some large diodes between the solar controller and the batteries. In case you don't know, a diode is like a one-way valve for DC current. The diods will allow the current FROM the solar controller to get to the batteries but current coming from the inverter will not be able to pass.

[jazty]

Originally Posted by WhiteWhale

What you are saying makes sense, but I am still not sure how I would/should protect my solar/charge controller from the charge output coming from the inverter when using the inverter to charge the batteries.?

There shouldn't be any reason to disconnect one while the other is working. Both the solar charge controllers sense voltage for operation and have internal diodes. While one is working the other will sense the voltage and turn off or down.

In essence, connect both to charge controllers directly to the batteries and you'll be fine

[WhiteWhale]

Originally Posted by jazty

There shouldn't be any reason to disconnect one while the other is working. Both the solar charge controllers sense voltage for operation and have internal diodes. While one is working the other will sense the voltage and turn off or down.

In essence, connect both to charge controllers directly to the batteries and you'll be fine

Ok. That seems like what most systems looked like to me but I wasn't sure if I was missing something and the last thing I want to do is fry an expensive piece of equipment. And a transfer switch I don't think would really work because Id have to choose between solar charging and using my inverter, but not both at the same time.

My next question is how to fuse the inverter/charger and solar charger circuits individually. The 60 amp solar charge controller came with a 60 amp inline fuse, but the inverter/charger is 70 amp and uses different size wire and fuse. Will the higher charging output from the 70 amp inverter/charger be an issue for the connected 60amp solar circuit?

[jazty]

Originally Posted by WhiteWhale

My next question is how to fuse the inverter/charger and solar charger circuits individually. The 60 amp solar charge controller came with a 60 amp inline fuse, but the inverter/charger is 70 amp and uses different size wire and fuse. Will the higher charging output from the 70 amp inverter/charger be an issue for the connected 60amp solar circuit?

If the solar charge controller requires a 60 amp fuse, then put that fuse between the batteries and solar charge controller. If the inverter/charger requires a 70 amp fuse, then put that fuse between the batteries and inverter/charger. That's all there is to it. One doesn't affect the other.

[WhiteWhale]

If I use a 4 lug Bus Bar does this make sense?

-Connect solar charger to one lug, with 60 amp fuse close to bus bar.
-Connect Inverter/Charger to another lug, with 70 amp fuse close to bus bar.
-Connect DC load center to another lug with fuse close to bus bar.
-Connect Batteries to bus bar (Do I put one large catastrophe fuse here?)

[family wagon]

A fuse (or circuit breaker) protects only its downstream from over-current conditions. I'd put protection fuses as near to the sources of power as is practical -- rather than putting fuses at a busbar, put them near the two chargers and the battery bank. For example, if the fuse for the battery bank were at the busbar (which I'm assuming is not very near to the batteries) then there's a long section of unprotected wire between the batteries and fuse. If that were to be damaged anywhere along its length by a sudden cut, gradual abrasion, etc there would be no automatic cutoff of its power and the resulting arcing could start a fire. Fire safety is the main thing driving electrical protection.

You may not need a fuse at the input to the DC load center: if it is chosen such that its max current rating is greater than what the fused sources can provide, then it is adequately protected by those source fuses.

[WhiteWhale]

Originally Posted by family wagon

A fuse (or circuit breaker) protects only its downstream from over-current conditions. I'd put protection fuses as near to the sources of power as is practical -- rather than putting fuses at a busbar, put them near the two chargers and the battery bank. For example, if the fuse for the battery bank were at the busbar (which I'm assuming is not very near to the batteries) then there's a long section of unprotected wire between the batteries and fuse. If that were to be damaged anywhere along its length by a sudden cut, gradual abrasion, etc there would be no automatic cutoff of its power and the resulting arcing could start a fire. Fire safety is the main thing driving electrical protection.

You may not need a fuse at the input to the DC load center: if it is chosen such that its max current rating is greater than what the fused sources can provide, then it is adequately protected by those source fuses.

Ok great thanks. I wasn't thinking correctly about the direction of power flow from chargers to bus bar. I will put the fuses close to chargers. Any thoughts on how to size the main battery fuse?

[family wagon]

In sizing the main battery fuse I'd first consider the "absolute max" charge and discharge rate for the battery bank. That should be available in technical data from the manufacturer. It will likely be higher than their "recommended" max rates, which are geared toward optimizing AH capacity and/or battery useful life. Don't choose a fuse that exceeds that absolute max.

Next I'd consider the actual (expected) charge and discharge rates for the extreme cases: charging at max rate with no house loads, and zero charging with all possible/reasonable house loads running. These might be different to the recommended max if, for example, loads are modest but the bank is being sized to run for days between charges. This is the current actually "needed" and is a good guide for fuse and wire sizing. Round up to the next higher standard fuse, or even one more level beyond that. Finally, balance the trade-offs: the fuse and wiring can be up-sized for future-proofing, reduced wire resistance, etc, in exchange for higher material cost and installation effort.

[superdave]

the inverter/charger will require a fuse between it and the batteries. a 2000 watt inverter will use a 300 amp fuse, a 4000 watt will use a 500 amp fuse. when a inverter/charger gets pluged in to shore power the loads are transfered to shore power. then the inverter shuts down and checks the incoming power, it then becomes a converter and starts charging the batteries. my xantrex will put 100 amps into the batteries.

[roach711]

Originally Posted by family wagon

In sizing the main battery fuse I'd first consider the "absolute max" charge and discharge rate for the battery bank. That should be available in technical data from the manufacturer. It will likely be higher than their "recommended" max rates, which are geared toward optimizing AH capacity and/or battery useful life. Don't choose a fuse that exceeds that absolute max.

I was told to size my fuses to the ampacity of the connecting cable. The fuse is there to keep the cable from melting/burning from a dead short. For instance, the 2/0 cable connecting my house and starting banks has a 200 amp fuse on both ends even though both banks have well over 200 amps capacity.