Charge Controller Question

Steven Lake · March 2014

Okay, I've been hunting around for an answer to this question and so far haven't found anything satisfactory, or really any kind of answer at all. So I'm deferring to you guys again since you always do such a great job of helping me out, and you guys really know your stuff.

Okay, let's say, for argument's sake, I have a 10amp charge controller similar to the Morningstar SS-10 which has a 30v top end input voltage and is designed to charge a 12v battery bank. If I were to, heaven forbid, somehow go above the input voltage of 30v, what would the unit do? Would it shut down to protect itself, or go up in a gigantic cloud of magic smoke? I guess I'd ask the same question about an overload event on the amperage side as well. But given how often I've seen people saying that you absolutely MUST have an appropriate fuse on the input side my guess is magic smoke if it's over amperage.

So I'm really leaning towards it doing the same if I went over voltage on the input, or over voltage on the output (ie, if you hooked a 24v bank to a 12v CC) as well. Again, I haven't done this yet (thank the Lord), nor do I plan to as doing so costs money which I don't like to part with if at all possible. Even so I'm curious what the end result would be if it did happen. It's really got my curiosity.

I think the question was spawned in my mind while researching residential wind generators and finding out that a few of them, in the right winds, could hump out an impressive 250v at 18a+ before hitting their high wind disconnects. o.0;;

Anyhow, your insights are welcome and appreciated as always.

mike95490 · March 2014

Re: Charge Controller Question

Don't connect a solar controller input to anything but solar PV panels. PV panels are current limited, and the controller works by connecting the source (PV) directly to the load (battery bank). If you connect a 24V bank to a controller and to a 12V battery, you will either blow an internal fuse in the controller, or just instantly and silently (or spectacularly) blow the controller. If you use jumper cables to connect 24V battery to 12V battery you will get sparks and flame!!!

Some MPPT controllers are capable of throttling back a higher battery voltage, to charge a lower voltage battery.

Cariboocoot · March 2014

Re: Charge Controller Question

Inexpensive PWM controllers such as the SunSaver 10 you mention do not have any kind of input over-Voltage protection. Put more than their rated V in and components will fry.

Even high-end controllers have their limits: an MX60 for example will shut down at 141 Volts but if the input Voltage rises above 150 again components are in danger of instant death.

I wouldn't use a wind turbine capable of 250 Volts on a battery system. Be sure you're not looking at one designed to feed something like a Windy Boy GTI.

Steven Lake · March 2014

Re: Charge Controller Question

Thanks guys. I kinda figured that would be the end result, but figured to ask just to be sure.

Cariboocoot, I'm not actually looking at getting or building with any of those items. Like I said, I didn't see anything that told me what would happen if certain criteria were exceeded, so I asked. The windmill was just used as an example of something that could put out insane amounts of voltage as an object point for my question.

PS, I looked up what a Windy Boy was. Very interesting! Never heard of one of those!

See? You guys really are awesome. I always learn cool stuff from you every time I come here.

Oh, one final PS. This thought came up from something Mike mentioned. He said, "Don't connect a solar controller input to anything but solar PV panels." My guess is because solar is more limited on its voltage swings and more regular than wind would be. But what about a hydro generator with a predictable output that's within the range limits of the controller? I saw one hydro generator that did 13 volts and 8 amps and another which did 15 volts at 6 amps (assuming both are spinning at the same rate of course). It's not a big deal. Just figured to ask since we're on the topic. Probably because we still have that 300 watt hydro generator laying around waiting to find a use.

mike95490 · March 2014

Re: Charge Controller Question

Steven Lake wrote: »

... something Mike mentioned. He said, "Don't connect a solar controller input to anything but solar PV panels." My guess is because solar is more limited on its voltage swings and more regular than wind would be. But what about a hydro generator with a predictable output that's within the range limits of the controller? ....

Aside from the voltage, there is also the likelyhood of AC ripple confusing the controller. Many *mills have a polyphase AC generator inside, a rectifier stack, and output ripplely DC.~~~~~~~~ That ripple may be enough to confuse the controller, sometimes a simple cap at the input is enough, sometimes a beefy LC filter is required.

BB. · March 2014

Re: Charge Controller Question

Just to be clear--It is don't connect any solar "PWM" controllers to non-solar panel power sources.

A PWM controller is just a "fancy" on/off switch. If you connect (for example) a 24 volt battery to a 12 volt battery through a switch, you will get very high current through the switch and wiring.

However, a good/true MPPT type solar charge controller can be connected this way (24 to 12 volt battery for example). They are true switching power supplies with current and voltage limits/controls.

There are MPPT controllers, such as those from Midnite Solar, designed to work directly with Wind/Water turbines (include optional dump loads).

And Wayne from Nova Scotia Canada has a small hydro turbine on a smaller MorningStar MPPT charge controller that works great for him (the MPPT controller just matches the turbine I*V output to the battery voltage--Actual charge control is done elsewhere).

The big issue with alternators is that their output voltage can rise over the maximum input voltage of the MPPT controller (MPPT controller shuts down, wind/water turbine with no load starts to over speed, voltage soars takes out MPPT controller, and alternator can even self destruct).

Not a project for those that don't have some extra money to experiment with/purchase (not cheap) equipment designed for the task.

-Bill

Cariboocoot · March 2014

Re: Charge Controller Question

The way PWM controllers are used with turbines is to attach the turbine directly to the battery bank and then use the controller in diversion mode to operate a dump load and 'bleed off' excess power. The battery then acts as a filter and stabilizes the ripple current. Not all controllers can be used in this manner, though.

Details, details, details!

Charge Controller Question

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