Sizing solar charge controller for 1.65kw solar panel array wired in parallel

[Hedges]

I prefer panels wired in series. But with only 3, that would be 150V nominal, more on a cold day.
If you get four you can wire them 2s2p. Each "2s" can be oriented differently, reducing peak current and extending hours.
That will be about 100Voc, so a 145V or 150V max MPPT charger could be good.
Program the charger for the max output current you want into the batteries.

 

[Offgridder8888]

I think two of these big batteries would be overkill for my needs. The battery says it can handle a max load current of 80A, they just don't sell anything bigger than a 50A charger at this particular store. But I figure that there's no inherent dangers or issues with using a 60amp solar charge controller with a 50 amp battery charger, it would just be less efficient, which I'm ok with. Is there a flaw in my thinking here? Would the battery not charge at all with this setup or does it risk damaging the battery? The other solution is that I can try and find a 60 amp charger somewhere else,

 

[Hedges]

Why do you say using ... solar charge controller with ... battery charger?

One charges battery from PV panels. The other (presumably) charges from AC source.
Might you use both simultaneously and be putting in 60 + 50 = 110A?

Lithium batteries accept almost any charge rate up to their max. They don't like being kept 100% charged (especially hot) or 0% empty, but are happy to sit somewhere in between for a long time. A 10A charger should be fine, just slower.

lead-acid usually has a minimum preferred charge rate. And needs to get fully charged including absorption.

Nothing wrong with overkill regarding performance an capacity. Just a problem with the price, if much more than minimum to meet your needs.

 

[rmaddy]

Why do you say using ... solar charge controller with ... battery charger?

Yeah, I'm confused by this too.

You don't need a separate battery charger. Or at least you won't be using it with the solar charge controller.

Let's back up a bit. We suggested a 60A solar charge controller based on the amount of solar panels you plan to have and the battery voltage. But it was assumed that your battery bank could accept a 60A charge.

If your battery bank can't be charged at 60A then there's no reason to get a 60A solar charge controller. You might as well get a solar charge controller that matches the lower max charge current rating of the battery bank. And then that means you probably want a fewer solar panels attached to the solar charge controller.

Again, the size of the battery charger that this vendor supplies is irrelevant. What is critical is the actual max charge current rating of the battery. That is what will determine the max size of the solar charge controller you should use which in turn determines how much solar you should use.

Related to this is the other side - the battery's max recommended discharge current. Make sure that meets the needs of any inverter you plan to attach to your system. That's a separate topic from the solar and charging but equally important.

 

[Offgridder8888]

OOOH I was confused, I didn't realize the battery charger was meant for AC source, thanks for the clarification! So one of 24V200ah batteries should work with the 60amp solar charge controller, correct?

Thank you for all your help guys!!! You guys are awesome!

 

[rmaddy]

If the "80A max load current" really means "80A max charge current" then you are fine with one battery and the 60A solar charge controller.

Google Translate is translating the Portuguese word "carga" to "load" but I think it should be "charge" in the context of battery power. This is based on both a Spanish-English dictionary and Portuguese-English dictionary app. Both show lots of meanings for "carga", including "load" but both also show "charge" as related to battery power.

 

[rmaddy]

BTW - you can use the battery charger that comes with the battery to charge the battery before connecting it to your solar setup.

 

[Hedges]

"Building off-grid solar system" ... "24V"

For your relatively small amount of PV, 24V should be fine for whatever loads you plan to power.
Most larger systems are 48V.
Depending on future plans, choose the voltage you really want now.

You can get an MPPT charge controller good for 24V & 48V banks. It will need to accept high Voc to work with 48V.
PV panels would need to be able to be assembled in an array meeting the voltage requirements (likely 2s2p rather than 3p)

If you were to go 48V, with 24V batteries make sure they say they can be connected in series (unlike lead-acid, because these contain transistors in a BMS, need to be able to handle the voltage.) A 48V battery would be preferred rather than two 24V or four 12V in series.

For 24V system, connecting 2x 24V batteries in parallel, connect charge controller and inverter to diagonally opposite terminals so current splits evenly between them. (More critical for lead-acid, but good to load the lithium batteries equally as well.)

 

[Mattb4]

I agree that it's irregular and you might be right. Here are the exact specs of the batteries that I bought :

Deep Cycle 24v 100Ah with waterproof case LiFepo4 lithium battery pack with 100A BMS for golf trolley golf cart camper caravan motorhome solar energy RV+29.2V 10A charger​

Description

• Voltage : 24V
• Capacity : 100Ah
• Chemistry : lifepo4
• Size:415*335*180mm / 166*272*355mm
• Charge voltage : 29.2V
• Discharge Cut-off Voltage:20V
• Charge Current:10A
• Continuous discharing current:100A can be customized
• Battery pack weight: about 12kg
• Recharge cycle : More than 2000 times

...

You are confusing the supplied charger ratings with how much the batteries can be charged at. That is not mentioned in the ad but typically a 100ah battery can be charged up to the discharge current rating. It does better to charge a .1C to .2C for longevity. You also have to consider that charging current varies during the charge.

 

[Offgridder8888]

Thanks for all the advice guys I really appreciate it!! I plan to buy a 3 kw pure sine wave inverter for this system, would this be a good one? Anything I should be careful about in terms of selecting the right inverter for my off grid solar system? Thanks in advance guys!!

Input voltage : DC 24V / 48V


Output voltage: AC220V


Frequency: 50Hz


Max Output power :3000W


Continuous power :1500W


Protection: Short-circuit, overload, super-charge, over-temperature protection
PURE SINE WAVE Inverter! Genuine Pure Sine Wave with very good quality.

The inverter has a DUAL Digital Display (PIC 2) and has accesories!

Features:
Converts electricity from AKI, Batteries to AC220V electricity. Suitable as a solar panel device and others

 

[rmaddy]

That appears to be a 1500W inverter with a 3000W surge capability. But without a link to the actual inverter it's hard to be sure.

 

[Offgridder8888]

Thanks Rmaddy here's the link: https://shopee.co.id/product/69558223/8060527147?smtt=0.775765043-1658460956.9

 

[rmaddy]

Thanks Rmaddy here's the link: https://shopee.co.id/product/69558223/8060527147?smtt=0.775765043-1658460956.9

There's not enough information on that page to be sure. The listing says 1500W continuous. To me that means it is a 1500W inverter. The 3000W maximum doesn't state if that's a surge capability or how long you can run it that high.

Most inverters are sized based on their rated continuous power. Most inverters support a very brief (a second or two) surge usually twice the continuous.

If you will never need more than 1500W of actual usage at any one time then that inverter may be fine. If you need to run 1500W - 3000W for more than a second or two then I wouldn't trust it without confirming what the actual limits are of the "3000W max output power".

 

[Hedges]

220V, 50Hz - I guess that means you're not in the U.S.

The starting surge of motors is about 5x nameplate current for about a second.
If inverter can deliver 3000W for a second or so, should start up to a 600W or 2.7A rated current motor. Maybe a small window A/C for instance.

 

[Offgridder8888]

Thanks Rmaddy! For now I don't think I need more than 1500 watts but I want to oversize my inverter in case I need to upgrade in the future. I found this one that is listed as a 6000 watt inverter but I guess it's really only a 3000 watt inverter since it's continuous power is 3000watt. Here's the link. Thanks for all the advice guys!!

https://shopee.co.id/product/573452663/13486659084?smtt=0.775765043-1658462176.9

 

[rmaddy]

That one seems to be a bit clearer that it is a 3000W continuous inverter with a 6000W surge capability despite the misleading marketing by calling it a 6000W inverter.

 

[Hedges]

DC water heater element?

Has anyone tried these? Just wondering if they actually work. I was wondering what to do with extra energy from the panels I have.

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