Using a charge controller with an all-in-one power station

[Jobey99]

So I have a couple of questions I want to run past some people far more knowledgeable than myself.
I recently purchased a Vtoman Flash Speed 1500 just because I had seen it on Black Friday and it was an amazing deal I couldn't turn down.

I also purchased a 120-watt solar panel from POWOXI that I think was mispriced on Amazon.

Plus, I already own a 60-watt Allpowers panel.



The solar panels are 18 volts Vmp and 22 volts Voc.

The power station has 2 DC inputs, one being a 30-60V, 400W solar input and the other being a 12-20V, 200W DC car input.

I would like to connect the panel or panels to this power station; however, they only have 5521 DC connectors on them, and I don't really want to adapt them to MC4 to try and series connect them, as I want the option to connect just one.



My questions are:

Can I connect the panel to the 12–20 volt DC port directly on the Vtoman? (I imagine this would be fine, but I don't want to try yet.)



If I can connect them to this port, could I connect them in parallel with a 5521 "Y" cable?



If I can't connect directly, could I connect the solar panels to a charge controller and then connect that to the 12-20V port?


Thank you to anyone who could share some insight.

 

[zanydroid]

Was going to ask for specs screenshots but noticed that you put it in text (screenshots might be easier for folks to notice).

If you connect the panel to 12-20 directly you're going to get some unknown variation on the theme of directly connection a solar panel to a small battery. Worst case, it'll pull power with current/voltage/impedance behavior so far outside the mpp that very little power comes through.

Presumably the solar input has an MPPT in it which will avoid those issues.

30-60V works with a single garden variety 400W residential panel, and there should be plenty of used supply in many areas.

 

[Jobey99]

Was going to ask for specs screenshots but noticed that you put it in text (screenshots might be easier for folks to notice).

If you connect the panel to 12-20 directly you're going to get some unknown variation on the theme of directly connection a solar panel to a small battery. Worst case, it'll pull power with current/voltage/impedance behavior so far outside the mpp that very little power comes through.

Presumably the solar input has an MPPT in it which will avoid those issues.

30-60V works with a single garden variety 400W residential panel, and there should be plenty of used supply in many areas.

Thank you for such a quick reply. I was going to post a screenshot, but the website for the power station is all pretty pictures and fancy slides, so I thought text would be better. I'll keep that in mind, though.

I'm glad I haven't tried the 12-20v port yet. Do you think I'd be able to use a change controller hooked up to the DC input port?

I have found multiple solar panels capable of direct connection to the solar input; however, I'm interested in using what I've got before I look into that. I also failed to mention in my original post that my use case is mostly camping and outdoor use, so the panels I have currently are portable and foldable.

Would another option be to use a DC-DC step-up converter to get the 30 volts needed?

I will eventually buy a 400w 40V panel, but the budget and GF disagree strongly with this option.

 

[zanydroid]

Thank you for such a quick reply.

I (and a few others) are going to try browsing by recent unanswered posts in random forums.

I'm glad I haven't tried the 12-20v port yet. Do you think I'd be able to use a change controller hooked up to the DC input port?

Maybe. It depends on if the charge controller does some kind of battery presence logic, if it does it may not like the input of the DC charger inside the power station. I don't know how common/uncommon that is. If it passes this then things should work OK.

You would also bottleneck charging capacity on the weaker of the DC charger and the charge controller.

Would another option be to use a DC-DC step-up converter to get the 30 volts needed?

The orthodox way is to connect panels in series until you get the voltage needed to activate the MPPT. It can be OK to do this with unmatched panels. The critical parameter to match is the I_mpp. Not matching is OK, you're just wasting the output potential of the panels that have higher I_mpp, which is better than not having a working system.

And of course don't let Voc go over the maximum voltage on the solar input. That can instant kill it.

Problem with a generic step-up converter is that it does not do MPPT. Solar panels are kind of shitty power sources -- they can be modeled as a constant current source to some extent, except if you go over their Vmpp their output will start nosediving until it hits zero at Voc. MPPT is nothing but a DC-DC converter / DC-DC charger that has a built in control loop on the input to hover around Vmpp (ideally) / avoid operating at a terrible point (pessimistically). I believe the control loop varies current while watching the output power. It might do a global sweep or it might stop at a local maximum while going down from Voc.

Step-up SCCs are somewhat rare, but they exist. Look for a MPPT/SCC targeting the eMobility space (EG scooters and eBikes). Typically those batteries are higher voltage than a single portable panel, or even a full size 400W panel.

I will eventually buy a 400w 40V panel, but the budget and GF disagree strongly with this option.

These things are way cheaper used than you might think. The possibility of a massive amount of solar panel e-waste is a real thing. Maybe less so in your area. I'm in California which has had tons of rooftop and utility solar for a long time, so there's always seemingly unlimited amount of random used panels you can grab. So for us the bottleneck is whether we want to bother with these heavy, scratch/dented, whatever modules. They would require a lot of expertise to use while car camping, etc. But some people do it.

 

[zanydroid]

The critical parameter to match is the I_mpp. Not matching is OK, you're just wasting the output potential of the panels that have higher I_mpp, which is better than not having a working system.

Forgot to mention that you also want to make sure the maximum system voltage and maximum series fuse rating are compatible.

Maximum system voltage is only of theoretical concern for the voltages you’re using.

The maximum series fuse rating of all panels needs to be larger than the largest Isc of the panels in the string. IIRC. Usually when you put together non matching full size panels in series this is no worry. But with random foldable panels I don’t know

 

[Jobey99]

Thank you so much. This has cleared a lot up. Sadly, I live in the UK, where we only maybe get 10-15 days even close to California, so solar panels are quite difficult to source, mainly from used solar roof installs, although nothing portable. As you mention, solar e-waste is the last thing I want; hence, I'm trying to rig something together to use with my current setup.


I have a few old charge controllers I may try. I have a 180w theoretical max and a 30A PWM charge controller that I no longer use; it came with an old solar panel but looks cheap, and I strongly doubt it has much logic in it at all. The downside of that is that I want to make sure my setup is safe.

My original idea of connecting the panels in series may be my best and safest option. I will do some more research into this before going much further, though.

Since writing my first post, I have connected my DC variable PSU to the input port and tested the voltage between 12 and 20 volts, and the power station seems to accept this fine. Part of me wants to plug in the panel and see what happens. I also tested the power station voltage and found it's 24 volts. I guess that makes sense from the solar input port voltages.

I want to assume that the 12-20V port is already using a step-up converter to feed the charge controller built into the unit.

I have to thank you once again. I really appreciate the time and effort you've put in to help. I have learned far more than I expected to. I think I'm going to have a think over the next few days and try to take in the information a bit and learn some more before I try anything.

 

[zanydroid]

I want to assume that the 12-20V port is already using a step-up converter to feed the charge controller built into the unit.

It should be pretty safe to plug in a panel with < 20Voc in there to see what it lands on. I would recommend testing it with a low charge on the battery so that you can see what happens at the full charging rate.

If you are down to trust the overvoltage protection on this thing you could go higher than that.

I also tested the power station voltage and found it's 24 volts. I guess that makes sense from the solar input port voltages.

Yes, that was my guess with 30-60V solar input since MPPT needs a few volts of headroom for the buck converter and some other stuff.

 

[Jobey99]

If you are down to trust the overvoltage protection on this thing you could go higher than that.

I can see myself giving this a go when I build up the courage. I should add I emailed the company and got a pretty poor response that I can't see being true but I'll quote it here anyway.

From myself:
"This mentions a 12-20v 200w DC input, could I try an 18v solar panel on this port or would this cause damage to my unit?"

Support:
"Yes if you plug the solar panel in the small round DC jack then the solar panel voltage is 12-30v, so your 18v solar panel can be plugged in the DC input jack."

So although I only mentioned 18V support seems to say anything up to 30V is fine however, if 30V is okay I can't see why they wouldn't mention this in the product manual or website.

 

[zanydroid]

I can see myself giving this a go when I build up the courage. I should add I emailed the company and got a pretty poor response that I can't see being true but I'll quote it here anyway.

From myself:
"This mentions a 12-20v 200w DC input, could I try an 18v solar panel on this port or would this cause damage to my unit?"

Support:
"Yes if you plug the solar panel in the small round DC jack then the solar panel voltage is 12-30v, so your 18v solar panel can be plugged in the DC input jack."

So although I only mentioned 18V support seems to say anything up to 30V is fine however, if 30V is okay I can't see why they wouldn't mention this in the product manual or website.

I don't trust the customer support for anything at this price point :laugh: