Which solar regulator for duel battery system?

[rwhit323]

I've been reading this thread to determine the best way to wire my two 80 watt soalar panels. The previous owner had to small panels and a wind generator wired to the battery bank via the battery selector switch. Additionally he had a on/off toggle switch in between the panels and the controller. My question is ... if I wire to the selector switch will the controller know when the alternator is charging the battey and prevent current form going to the solar panels? I really do not want to have to remember when to turn a switch on or off for charging. Or would it simply be easier to wire directly to the batteries and skip the battery selector switch? Thanks fo any thoughts.

[hellosailor]

r-
What kind of controller do you have? What options for connections does it have?

What is the output of the wind generator, and the battery (one or two?) capacity?

Generally they will integrate best with some human supervision, or a relay control of some kind. They're not smart enough to be left alone in the same sandbox.

[starfish62]

The controller should be "downstream" only; in other words it has a diode preventing the current going back through the controller. The controller probably has a high voltage disconnect (generally around 15.6 amps), where it will "shut down" the panels for 24 hours if the high voltage is exceeded. With two, 80-watt panels I doubt you'd ever see that, but if the alternator has a high "float" setting it may trip the controller (regulator) as the controller monitors your batteries as well as regulates the voltage. You might be able to adjust the high voltage disconnect manually. Google your controller and they'll have the specs, I'm sure.

I had two, 150-watt Kyocera panels (below-deck autopilot, so I needed a lot of juice) wired into the common hot on a 1-2-both switch (through a Morningstar 30 controller) and an 80-amp alternator and they never fought.

[hellosailor]

Starfish, if the Morningstar--or any MPPT controller--sees the voltage from the alternator present at thebattery (which it will if they are simply combined) it will cut back the MPPT output. Similarly, if the alternator regulator sees the voltage from the solar panels, it will cut back and probably go into float mode prematurely. Either way, unless the battery bank is so badly depleted that it is sucking both sources below 13.8V, the two controllers (controller & regulator) MUST be causing problems for each other. You'd probably never see them without putting both ammeter and voltmeter on each--isolated form each other. But the basic nature of the way they sense output and control it, means they cannot work properly when they are simply ganged up. (Excepting, for that really really hungry battery.)

Now, some, prehaps most, alternators with internal regulators, are wired up wrong to start with on boats. They are wired up as "single wire" systems with the charge sense lead tied right back to the output, or tied to it a foot or two away instead of right on the battery. In that setup the alternator probably would be mainly "looking at itself" and less problematic--but that kind of setup is really no good form the start. The sense lead MUST go to the battery being charged, for a proper and efficient charge.

Could be that since the MPPT controller is always "just barely" leading the battery voltage, that it and the alternator are just teasing each other and the net effect is to present an "almost real" battery voltage to each of them. Still, that wouldn't allow both to run at max output--which a real "one controller to rule them all" would allow.

[Therapy]

Originally Posted by hellosailor

a real "one controller to rule them all" would allow.

I am far from expert in the 12v world.

I don't know why that does not exist though because as you said, if one could put an ammeter and volt meter on all items and look at the results and throw various switches to make it work then why cannot a black box be set up to do it?

[hellosailor]

I suspect because a black box would have to be more complicated [read: expensive] than the market would bear. It would need to read three voltages (battery, two inputs) and then regulate each of two sources. Or, read two banks and regulate two or perhaps three sources. And either replace the regulators, or be able to "fool" their sense leads--which sometimes are the charge output leads.

So the black box might need to be an MPPT controller, a dump regulator (for wind) and an external alternator regulator, all working in harmony with one brain behind them. Maybe a $600-800 box, versus under $50 for someone to use a manual relay or switch, and a fairly small market for multiple-source users in the marine market.

Or, maybe there's something out there, and it just hasn't been publicized very much yet.

For that matter, why are some boats set up with a "one wire" alternator, instead of running the sense lead through the battery switch, to both banks? [Hint: knocks $50 off the selling price of the boat.]

[rwhit323]

The controller is a Flexcharge USA PV7D (and 80 watt panels) and the instructions imply that another source (alternator) can be charging the batteries with out isolating the panels. I've asked nuerous boat owners and have received 50/50 answers concerning the need to isolate the panels when the alternator is charging (engine running). I am wiring two systems to two diferrrent battery banks so thought I would experiment and wire one with the toggle switch to isolate the panels, and one without. Then measure and monitor to see if there are any differences.

[hellosailor]

I guess Flexcharge is getting into the "he said, she said" argument. Since I've never met one, I have to go by what their manual does and doesn't say.
http://www.flexcharge.com/flexcharge...v14_manual.pdf

It appears that despite their protests, the ARE using a sort of PWM charging. Even though they say that depletes electrolyte more than they do. Well, sure, it might deplete electrolyte more--because it is charging more often. They are simply using slow pulses and relying on a careful match of the panels not to exceed the absorption rating of the batteries. Given the same criteria, any PWM system should work equally well.

Apparently they are doing "one wire" sensing, i.e. applying voltage in a fixed range, then shutting off as battery voltage comes up. No magic there, Delco did that 40 years ago--but used a dedicated voltage sense wire instead. And their integration of a wind charger just relies on using the solar regulator's output to drive a relay dumping wind power. When the battery is below 14.3 volts, they blindly feed all power to the battery. When the battery voltage is up, they disconnect the solar and dump the wind. Nice--but the mercury wetted relay they use, wouldn't work on boats that heel and bounce.

And they are not using a three-stage or continuous regulator, they are simply dumping 14.3 volts (or full panel output, that's unclear) into the batteries to charge them all the time. Does their admitted "low frequency PWM" scheme work any better? Dunno. But it is not using MPPT conversion, so it is not delivering "full power" even if it delivers full voltage. It seems like a robust and perhaps inexpensive way to build a solid regulator--but a dumb one. And if there's some other power source, like an alternator, feeding the same batteries? From what I see this would simply shut down the solar and wind sources, rather than making use of them to reduce alternator run time.

The simplicity and reliability might impress me, the claims for technical superiority...I dunno know, there's too much sizzle and too little steak to satisfy me. I'd want to see (not do, thank you!<G>) a set of battery cycles with this and with other systems, before I'd believe this one worked any better, especially if the panel size wasn't so precisely matched to the battery bank. I suspect the more expensive systems will do a better faster job, at a higher price.

[starfish62]

[quote=hellosailor;179489]Starfish, if the Morningstar--or any MPPT controller--sees the voltage from the alternator present at thebattery (which it will if they are simply combined) it will cut back the MPPT output. Similarly, if the alternator regulator sees the voltage from the solar panels, it will cut back and probably go into float mode prematurely. Either way, unless the battery bank is so badly depleted that it is sucking both sources below 13.8V, the two controllers (controller & regulator) MUST be causing problems for each other. You'd probably never see them without putting both ammeter and voltmeter on each--isolated form each other. But the basic nature of the way they sense output and control it, means they cannot work properly when they are simply ganged up. (Excepting, for that really really hungry battery.)

The setup I had (xantrex-shunt system) took the sensing wires from the voltage regulator (alternator) to each battery bank. The sensing wire from the morningstar was also the output and went to the common hot on the battery isolator switch. The alterator therefore read the battery downstream of the controller, but we're really talking about a small amount of amperage from the PV,s. There was never a problem with the alternator putting out. I didn't have a way to separately monitor the PVs.

It's possible the morningstar (PV regulator) read the battery charge while the alternator was keeping it falsely high, but I don't think that matters much. The PV's will continue to put out unless the high voltage disconnect voltage is hit. The engine is used so seldomly, and the PV's are constant. Run the engine at night versus at noon and see what the output is at the same RPMs (I'm assuming you have a battery monitor, or at least a voltmeter) if it's a point of concern.

If one wished to isolate the PV's with the 1-2-both switch like I had (with the PV output coming into the common) it would be simple to charge one bank with the alternator with the switch to "1," then charge the second with the switch to "2." It's nice to be able to isolate a battery if one goes bad, but I don't see the benefit of the isolation in charging if all of the batteries are in service.