Trying to cobble together a 24V system...with 12v batteries and panels

[DaddyBUDsDoorags]

4 12v 200plus lowtemp batteries.
100a 24v mppt controller.
4000w 24v pure sine wave inverter.
Currently 4 100W Harbor Freight panels(18v?). Will expand more as I progress in the future build.

I think I can wire batteries in 2s2p configuration.
Can I do the same with panels?
Can I mix different sized panels and not harm the current panels?

I need help figuring out what else I need to complete this system (fuses, breakers, cutoff switch, cables, etc.)
I'm not quite sure how to determine what I need to do this.
All the charts confuse me.
The videos either over simplified the subject or are filled with language above my antique knowledge base.

 

[yodamota]

what controller do you have?

 

[DaddyBUDsDoorags]

This is being shipped out already.
It has the remote monitor

 

[littleharbor2]

Something fishy with your "MPPT" controller. It looks like the real thing except the max voltage limit. That tells me it's not MPPT. Can we ask what you paid for it?

 

[DaddyBUDsDoorags]

what controller do you have?

 

[DaddyBUDsDoorags]

Something fishy with your "MPPT" controller. It looks like the real thing except the max voltage limit. That tells me it's not MPPT. Can we ask what you paid for it?

$220

 

[profesor79]

You can wire it as 2p2s or 4p - and tfor me it will depend if all panels will get equal sun or shadows.
The specs allow for that (max 96v open circut)

100A 80A 60A-20A MPPT Solar Panel Regulator Charge Controller 12V/24V PV 100V K1 | eBay

MPPT K100A MPPT charging mode. Model MPPT P40 MPPT P60. PV input Power:2400W. PV input Power:2000W. PV input Power:1500W. PV input Power:1000W. PV input Power:1200W.

www.ebay.co.uk

 

[littleharbor2]

$220

The price looks appropriate but the low max Voc and Vmp seem odd Plus the Max of 100 amps PV input sounds odd as well.

 

[littleharbor2]

You can wire it as 2p2s or 4p - and tfor me it will depend if all panels will get equal sun or shadows.
The specs allow for that (max 96v open circut)

100A 80A 60A-20A MPPT Solar Panel Regulator Charge Controller 12V/24V PV 100V K1 | eBay

MPPT K100A MPPT charging mode. Model MPPT P40 MPPT P60. PV input Power:2400W. PV input Power:2000W. PV input Power:1500W. PV input Power:1000W. PV input Power:1200W.

www.ebay.co.uk

His specs say Max 72 Vmp for 24 volts and 36 for12 volts. Thats very low for a MPPT controller.

 

[profesor79]

The price looks appropriate but the low max Voc and Vmp seem odd Plus the Mac of 100 amps PV input sounds odd as well.

The connectors are not build for 100A,
and here is a discussion regarding this device: https://diysolarforum.com/threads/ooycyoo-charge-controller-questions.47411/

 

[DaddyBUDsDoorags]

$220

 

[DaddyBUDsDoorags]

You can wire it as 2p2s or 4p - and tfor me it will depend if all panels will get equal sun or shadows.
The specs allow for that (max 96v open circut)

100A 80A 60A-20A MPPT Solar Panel Regulator Charge Controller 12V/24V PV 100V K1 | eBay

MPPT K100A MPPT charging mode. Model MPPT P40 MPPT P60. PV input Power:2400W. PV input Power:2000W. PV input Power:1500W. PV input Power:1000W. PV input Power:1200W.

www.ebay.co.uk

I'm going to add more panels once I measure available space.
Can I add higher capacity panels to my system and configure them to feed the same 100A mppt controller?
As long as they are on different streams.

 

[profesor79]

so 3 feet connection cable shall be 3AWG... which is 2 times bigger that the 10mm2 connecteor on the charge controller.
source here: https://www.omnicalculator.com/physics/wire-size

You can try to squize the device, but I will suggest to put 70amps on it, but always you can add more charge controllers to the system.

 

[DaddyBUDsDoorags]

It's not obvious to everyone that the specs from the advertisement are for all the different versions of the controller I bought.
I will get the 100A version...
I'm grateful for all the help but it's impossible to discern which comments are based on knowledge or confusion.
This wasn't my intent when I posted this comment.
Maybe I need to find experienced technicians to get accurate help.

 

[profesor79]

we all here trying to help,
this device looks great on the paper - but real life experience could be different.
I think that it will be good if other members will share their toughts, so you could make the best from your purchase.
(Personally I have some of those chinesse stuff, so I am trying to avoid any circumstances that could lead to unnesessary fire).

have a great day - it is time to bed for me :D

 

[DaddyBUDsDoorags]

Thanks
The main thing I was searching for was fuse, breaker and wire gage sizes for the panel to controller to batteries to inverter sizes and what size fuses (location) along with breaker location and sizes...to isolate components to avoid fires...paranoia can be both useful and annoying simultaneously...ha ha

 

[Rednecktek]

Considering you're running a 24v system, and your controller maxes out at 96v, you've got some complications to work with.

First issue is the SAE heads on those panels. You're going to need to lop those off and replace them with MC4 plugs so you can connect them up in 2s2p. The Vmp is 18v but the Voc is 25v+ which is more than your controller can take in 4s. If you want to add panels later, try to keep them as similar as possible so you don't nerf your other panels. If you go with more of the 100w panels, you can get 2 more and upgrade to 3s2p.

So, now that you've got them re-headed and running in2s2p you don't need a fuse on that end.

From the controller if you do a fuse to the battery, you'll only be getting 20a out of it max, but if you want to give yourself room to grow later go with a larger wire and fuse for that wire size. Figure out how big a wire you're gonna stick in there, figure out how much amperage it can take, and add 20% (rounding up).

The inverter is going to need 2/0 wire and a 200a fuse (4000w ÷ 24v = 166a × 1.2) according to the Blue Sea Ampacity Table.

As for other things that are good to have:

A proper shunt to keep track of how your battery is doing. Aili and Renogy make well likes and cost effective units.

A DC breaker between your batteries and inverter, and another one from the controller to the panels make servicing much easier. Avoid the tube type.

A proper amp clamp meter that can read DC amps and inrush current is an invaluable tool.

 

[DaddyBUDsDoorags]

I've got mc4 fittings coming.
Was going to do 3s anyway...can I do 3s3p or 3s4p?
This will be my first expansion (with more panels) if I'm not exceeding the controllers capacity. Should I add 30a inline fuses on each 3series run to isolate (incase of damage to a panel)? Those wires all seem to be 10awg, right? Is that adequate all the way to the controller?

The shunts come in various sizes...should I stay at 200A like the breaker on positive wire to inverter?
Would cutoffs be as good for panels to controller and controller to batteries, with 20A(?) fuse ?
The current 4 batteries are in front section of 30ft RV (beside the current 110v and 12v RV fuse panels) and will be close to inverter so short 12in runs to bus bar then 24in to inverter, with 200A breaker on positive wire to inverter.

I'm confused about 20a fuse from controller to batteries?
They will be 5-6ft apart.
What size wires are we talking(suggestions)?

If I add batteries and rear panels they would be in different location in RV(between 10-20ft away) ...should I just run a different mppt instead of a 10ft jump across the RV to the current mppt/inverter? I'd like to use the one 4000w inverter for convenience.
I'm getting a 24V to 12V converter to power my current RV fuse panel...any suggestions?

Damn, this is alot of questions...sorry for that, but I'm learning .

 

[DaddyBUDsDoorags]

Update: I ordered the 10awg and 0/2 wire, fuses, breakers, "Y" branches, bus-bars, wire ends, crimping tool, battery monitor/shunt.
Still need 12v converter and panel mounts

 

[jungleplant]

4 12v 200plus lowtemp batteries.
100a 24v mppt controller.
4000w 24v pure sine wave inverter.
Currently 4 100W Harbor Freight panels(18v?). Will expand more as I progress in the future build.

I think I can wire batteries in 2s2p configuration.
Can I do the same with panels?
Can I mix different sized panels and not harm the current panels?

I need help figuring out what else I need to complete this system (fuses, breakers, cutoff switch, cables, etc.)
I'm not quite sure how to determine what I need to do this.
All the charts confuse me.
The videos either over simplified the subject or are filled with language above my antique knowledge base.

like to keep it mobile