Negatives to oversized charge controller?

Is there any negatives to oversizing the charge controller on a 400 watt system 12v besides price? I was thinking about going up to a 60amp or 80amp charge controller so I could be more future proofed. I don’t mind spending more now so I don’t have to upgrade it in the future.

Cost. That's about the only downside and is totally worth it to NOT have to buy another controller later.

My bet is that the conversion efficiency varies slightly depending on the load so there is probably a sweet spot. Usually that sweet spot if less than full rated load. It will be equipment specific but a SWAG is probably in the 80 to 90% range.

I wouldn't spend much money on 12v equipment.
If you plan to grow in the future. You will probably increase system voltage also.

There is a small reduction in efficiency.

Epever prints efficiency curves in their manuals.

Victron does not show their efficiency curves but claim they remain 90-94% efficient across the curve.

So it’s not a significant problem IMHO.

In addition to higher current consider a SCC that can handle higher voltage up to a 48V nominal battery for future expansion of your system.

timselectric said:

I wouldn't spend much money on 12v equipment.
If you plan to grow in the future. You will probably increase system voltage also.

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The more I’m learning the more I’m thinking about starting with 24v

JoeHam said:

In addition to higher current consider a SCC that can handle higher voltage up to a 48V nominal battery for future expansion of your system.

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Thanks I didn’t realize they had charge controllers that can use 12v/24v/36v/48v That seems like a no brainer. I’m starting to think I might just start with 24v was trying to stick with 12v for simplicity but it doesn’t look much harder to step it down for the DC devices

Also don’t be only forcused on current output but also VOC limit, what’s the point of having a 60a output if you can only handle 100v of PV. Not saying many units are like that but still take into account all the parameters of a SCC.

I’d much rather save some coin on conductor and run something at 150/250v from the PV array to the SCC.

With common panels running ~40v VOC doesn’t take much to be limited to 3S configurations.

One option is to have a small 12V setup (400 watts at max, probably) and a larger 24V or 48V setup. If you have sensitive electronics like radios, having a dedicated 12V can be nice in case a 12V buck converter is noisy. The buck converter will always also draw some current (not sure how much).

But, if nothing is sensitive and the idle current + efficiency loss is not a problem, I'd go with higher voltages and a buck converter if you want to go that way.

Bigger charge controllers usually draw more at idle. You also will have a better idea of what you want by the time you want to grow the setup. I understand the logic in wanting to get a bigger one to grow (I did that, too), but in the end it seemed a bit overkill.

Also consider checking Ebay for used charge controllers. Can be a gamble, or can save some. If your panels are close by, you could save a ton of money by doing them in parallel and getting a 30A PWM charge controller. Then saving up towards a bigger 48V system that would be better for higher loads, especially inverters.

If you go 24V and DIY lithium I'd go for two parallel strings of batteries as you can reconfigure them for 48V later. I just found the JKBMS I got for 48V can be wired for 8S. Then the only major component you can't keep if you change the system to 48V is the inverter.

Two separate systems is no bad thing, aside from a little more time watching it. I'm making that kind of decision now, and leaning towards one system, but with enough parts that *no* one device failing can take the whole thing down, and many two devices won't either.

iwasforcedtopickausername said:

One option is to have a small 12V setup (400 watts at max, probably) and a larger 24V or 48V setup. If you have sensitive electronics like radios, having a dedicated 12V can be nice in case a 12V buck converter is noisy. The buck converter will always also draw some current (not sure how much).

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This is how I’m doing it for my off grid setup. Small 12v system to start off and will use the small and extremely efficient victron 12/1200 inverter to power 24/7 loads like a mini fridge, circulation fans, some security lights and cameras with out worrying about big idle consumption numbers. I will eventually add a larger 48v system with a multiplus II that will only get turned on when I’m at the property and want to run AC/Heater, microwave, and other large appliances.

Smeeg said:

The more I’m learning the more I’m thinking about starting with 24v

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I started with a 24V inverter, SCC and 200w of panels last Christmas, I made a back up power supply for my coal stove with an automatic transfer switch....
As I'm typing this my house is running off 22kwh DIY battery power, through a 48V 6kw AIO, charged by my 5.6kw of panels (I need way more ( ground mount is next).
Keep learning until it all just makes sense one day, I'll warn you it's an addiction that's fun, expensive, green, potential dangerous, satisfying and so much more.

740GLE said:

Also don’t be only forcused on current output but also VOC limit, what’s the point of having a 60a output if you can only handle 100v of PV. Not saying many units are like that but still take into account all the parameters of a SCC.

I’d much rather save some coin on conductor and run something at 150/250v from the PV array to the SCC.

With common panels running ~40v VOC doesn’t take much to be limited to 3S configurations.

Click to expand...

Thanks I wasn’t even looking at the VOC limit great point