Charge controller manual?

[SolarSamSurfer]

I recently got a cheap PWM charge controller to be able to charge my batteries individually to do some tests and charge my car battery if i need to. The controller says Max PV voltage 50v and Max PV power 390W. In the manual it has a note "12v battery with 18v solar panel. 24v battery with 36v solar panel". Now i am not sure if my panel will be to big or not. my panel is 385W 9.7A at Pmax and 39.7V at Pmax. I was certain it would be fine as the controller was advertised as max 50v. But this note in the manual has made me unsure.

 

[chrisski]

A better solution would be to get a better MPPT SCC.

Your panel at 39 volts may be good for 24 volt charging, but too much voltage for 12 volt charging. Honestly though, if I hooked the panel up, it would only be to a 24 volt system and only if I could accept the loss of the controller and or battery. It’d be exceeding specs.

Those cheaper PWMs are quite lacking on documentation, so it’s hard to tell for sure.

Also hard to find a panel at exactly 18 volts and 36 volts, so there’s some leeway. An 18 volt panel would have more voltage when cold and less when hot.

 

[Bud Martin]

It will not be efficient using that large panel. What is the Voc of the panel?
Learn more here:

Can I use a 24V solar panel to charge a 12V battery?

Yes, you could do it. The voltage isn't too much of a concern, it is the current the panel can provide. What is commonly known as a 12V panel is usually a 36-cell module with an open-circuit voltage of 22V, making maximum power at 18V. Traditionally so-called 24V pane

www.acopower.com

 

[SolarSamSurfer]

yes i wish i could buy a better controller but i dont have the money to so i guess ill just have to leave it here and find another way to charge my batteries. the voc is 48.6v

 

[timselectric]

If you want to use it, until you can afford a better one. Just keep an eye on it, while charging. Don't leave it connected, and unattended. Check the charging specs, for the battery. And don't let it get too far off.
This way, you can get some use out of it. And if it craps out, oh well.

 

[DerpsyDoodler]

yes i wish i could buy a better controller but i dont have the money to so i guess ill just have to leave it here and find another way to charge my batteries. the voc is 48.6v

That panel is fine for the controller. It's not an all the time thing. It's so he can individually maintain his 12V FLAs when he needs to.

 

[chrisski]

That panel is fine for the controller. It's not an all the time thing. It's so he can individually maintain his 12V FLAs when he needs to.

Have you connected a 40-volt or 48 VOC panel to a PWM SCC for 12 volt charging?

This is where exceeding specs for a PWM and I’m not sure what will happen. In general, the PWMs I've looked at ask for a 18 volt or so panel for a 12 volt battery or 36 volts or so for a 24 volt battery. I do see the sticker on the side that says 50 volts is OK, but usually there is a different spec for voltage. When I see two different specs, I go with the most restrictive until I can confirm the other is correct. I find mis-matching guidance a little bit.

I own a 60 amp PWM for a 12 volt system, but have only used it once. I found with the voltage limitations of around 18 volts for a 12 volt charge, I could only hook up 100 watt panels, and then to get to the 60 amp output, I'd need to parallel 9 or 10 panels, without putting any in series just to meet the specs. That's some thicker wiring than I wanted to deal with and a bit of voltage loss as the runs get longer.

Depending how the PWM is built, I could see it taking more volts like you mention, but I can also see the PWM not converting it efficiently and bleeding this waste off as heat, and maybe even the magic smoke some have talked of. I don't know if that's what that PWM SCC would do, but would not be the first on my block to try it.

 

[sunshine]

yes i wish i could buy a better controller but i dont have the money to so i guess ill just have to leave it here and find another way to charge my batteries. the voc is 48.6v

It is very easy (for many) panels to convert them to a lower voltage....YT is your friend!

Maybe even simpler with your panel since it has a Voc of 48 as you can wire straight into the connection box at the back of the panel giving you 3 panels at 16v.

 

[DerpsyDoodler]

yes i wish i could buy a better controller but i dont have the money to so i guess ill just have to leave it here and find another way to charge my batteries. the voc is 48.6v

Unfortunately that controller doesn't even do a proper equalization cycle. 14.6v isn't suitable. If you still want to try to use it, there are options. Coming up with a voltage divider circuit to put in series between the panel and controller, or what sunshine recommends above. Personally I would lean toward a voltage divider circuit, as it doesn't involve mucking with panel wiring internals.

That said, I don't feel comfortable with providing instruction for this. I'll say that voltage divider circuits are simple, and large resistors are cheap. You would have to put several in parallel (enough to handle the power) and the same amount again in series. Look up voltage divider circuit.

Try any of this at your own risk. Someone else may be willing to help, but at this point I am bowing out.

Here is my last but of advice:

Invest in the proper equipment. Either get an MPPT and consider it a worthy investment or get a benchtop power supply like I originally suggested (I urge the benchtop PS, it is cheaper and more flexible than an MPPT), even if you have to go to the town center to plug it in and use it. I guarantee this won't be the last time you need this toolset.

 

[Zil]

those panels will fry the 12 v battery using a pwm cc. you can use this for 24v

 

[SolarSamSurfer]

Not going to be using the controller for this purpose in the end, i will keep it for the future for any project that could come up!