Adding a panel to older system

[Gengfawn]

About 5 years ago I purchased an off-grid cabin with a system that was installed in 2012.

The system it came with was:

4 x 180watt panels
Morningstar CC - TS-MPPT-60
12 x 232ah 6volt GC2 batteries
3000 watt - 24v Inverter
Iota Auto Transfer Switch - ITS-30A
Iota Charger - DLS 27-25
Gas Generator

I've done my best to look after the batteries by not discharging below 24v and keeping them topped up with distilled water but they are past their useful life for me now and I find myself having to rely on my generator quite often.

Ive been wanting to replace the FLA batteries with LiFePO4 but I was having a trouble finding a supplier that would ship to my location. Recently I found that Exliporc on Alibaba will ship to me so I ordered some cells. My plan for the battery is as follows:

8 x 314ah Hithium Cells
JK BMS (JKB2A8S20PHC)
24v self regulating heating cable to allow charging when below 0C
Mersen 400a class T fuse and holder
Pass thru terminals for the box
Epoxy sheets between the cells
Kapton tape to hold together the cells
Plywood box lined with cement board
Plastic storage bin lined with fiberglass insulation to place plywood box inside of

After building the battery from what I understand I will need to change the charge settings in the charge controller by uploading a custom profile, change charge profile for the ac - dc charger with the LiFePO4 IQ4 module, and use a precharge circuit prior to attaching the batteries to the inverter to prevent in-rush.

Besides the battery I also plan to add a solar panel to the system. I was having trouble finding a panel that matched perfectly but I found a panel that has similar voltage. The old panels are 35.5 Vmp and 5.07 Imp with the current arrangment being 2s2p so the charge controller has about 10 amps at 71 volts supplied to it. The new panel is rated 13.37 amps at 37.41 volts. I plan to wire all panels in parallel to supply the charge controller with about 33.5 amps at 35.5 volts and fuse each postive wire with an inline MC4 fuse (8amp on 180 watt panels and 25amp on 500 watt panel).

I've attached a diagram of my planned design. Any input or advice would be greatly appreciated.

 

[Rednecktek]

I plan to wire all panels in parallel to supply the charge controller with about 33.5 amps at 35.5 volts and fuse each postive wire with an inline MC4 fuse (8amp on 180 watt panels and 25amp on 500 watt panel).

Skip the inline fuses and go with a 6-way combiner box.

 

[Gengfawn]

Skip the inline fuses and go with a 6-way combiner box.

I was having trouble finding a solution that would allow 8amp max breakers for 4 panels and a high enough rated breaker for the new panel in the same combiner box. I assume there is a way to build a customized solution but it seemed to be expensive.

I thought that individual fuses although would be a nuisance if they ever do fail seemed easier/cheaper and I still have the disconnect to isolate all the solar from the charge controller.

Other than tidyness and ability to disconnect individual panels is there another reason I'm missing on the combiner panel?

 

[Rednecktek]

All the combiner boxes I've used have a standard size fuse for each panel input so you can replace those with whatever size you need. You can pop each fuse out if you need to disconnect a specific panel.

The breaker inside is usually just a DC rated DIN rail breaker, so if the factory breaker isn't enough, you can swap it out too. The ones I've used come factory with a 63a breaker which is plenty.

Having a combiner box is a more solid connectiin than notoriously flakey inline fuse holders, has less points of failure exposed to the weather, and just makes things easier to work on if everything is in one place.

As for cost, the $150 for a complete box isn't a bad investment. There's no need to spend $$tupid money on a combiner box.

 

[Gengfawn]

All the combiner boxes I've used have a standard size fuse for each panel input so you can replace those with whatever size you need. You can pop each fuse out if you need to disconnect a specific panel.

The breaker inside is usually just a DC rated DIN rail breaker, so if the factory breaker isn't enough, you can swap it out too. The ones I've used come factory with a 63a breaker which is plenty.

Having a combiner box is a more solid connectiin than notoriously flakey inline fuse holders, has less points of failure exposed to the weather, and just makes things easier to work on if everything is in one place.

As for cost, the $150 for a complete box isn't a bad investment. There's no need to spend $$tupid money on a combiner box.

Thanks, That makes sense.

I was wrongly assuming that each string was on a breaker instead of a fuse which can be easily swapped.

I'll order the combiner box instead

 

[Suijkerbuijk]

About 5 years ago I purchased an off-grid cabin with a system that was installed in 2012.

The system it came with was:

4 x 180watt panels
Morningstar CC - TS-MPPT-60
12 x 232ah 6volt GC2 batteries
3000 watt - 24v Inverter
Iota Auto Transfer Switch - ITS-30A
Iota Charger - DLS 27-25
Gas Generator

I've done my best to look after the batteries by not discharging below 24v and keeping them topped up with distilled water but they are past their useful life for me now and I find myself having to rely on my generator quite often.

Ive been wanting to replace the FLA batteries with LiFePO4 but I was having a trouble finding a supplier that would ship to my location. Recently I found that Exliporc on Alibaba will ship to me so I ordered some cells. My plan for the battery is as follows:

8 x 314ah Hithium Cells
JK BMS (JKB2A8S20PHC)
24v self regulating heating cable to allow charging when below 0C
Mersen 400a class T fuse and holder
Pass thru terminals for the box
Epoxy sheets between the cells
Kapton tape to hold together the cells
Plywood box lined with cement board
Plastic storage bin lined with fiberglass insulation to place plywood box inside of

After building the battery from what I understand I will need to change the charge settings in the charge controller by uploading a custom profile, change charge profile for the ac - dc charger with the LiFePO4 IQ4 module, and use a precharge circuit prior to attaching the batteries to the inverter to prevent in-rush.

Besides the battery I also plan to add a solar panel to the system. I was having trouble finding a panel that matched perfectly but I found a panel that has similar voltage. The old panels are 35.5 Vmp and 5.07 Imp with the current arrangment being 2s2p so the charge controller has about 10 amps at 71 volts supplied to it. The new panel is rated 13.37 amps at 37.41 volts. I plan to wire all panels in parallel to supply the charge controller with about 33.5 amps at 35.5 volts and fuse each postive wire with an inline MC4 fuse (8amp on 180 watt panels and 25amp on 500 watt panel).

I've attached a diagram of my planned design. Any input or advice would be greatly appreciated.

View attachment 245648

In series all panels have to be same ampère
If you set a higher model that model will only do what the weaks ampère panel do .

Do not go in in parallel
The cable will not handel really good that 35a .

Series and parallel is the best option to go.
For the mppt it do not care so long the volts are in the limit of the mppt
And multi strings is not a problem so long both strings have the same volts output put
You do need if you go that way.
A one way block diode by Multi strings in the pv cable from both strings.

Mppt only look to the watts it can pull van de the panels
So 500watts in series or parallel will not change the max charging for the mppt.
Both will be the same output from the mppt.

The pv cable connect on the solarpanels are 4mm2 (25a) or 6mm2 and it can max handel 30a in parallel or series.
Just a option to think of .
Personal i go for high volts the mppt wil start faster on the day and end later in the day.
For the winter the same way it will have more performance than in the summer.

 

[Rednecktek]

In series all panels have to be same ampère
If you set a higher model that model will only do what the weaks ampère panel do .

Do not go in in parallel
The cable will not handel really good that 35a .

Series and parallel is the best option to go.
For the mppt it do not care so long the volts are in the limit of the mppt
And multi strings is not a problem so long both strings have the same volts output put
You do need if you go that way.
A one way block diode by Multi strings in the pv cable from both strings.

Mppt only look to the watts it can pull van de the panels
So 500watts in series or parallel will not change the max charging for the mppt.
Both will be the same output from the mppt.

The pv cable connect on the solarpanels are 4mm2 (25a) or 6mm2 and it can max handel 30a in parallel or series.
Just a option to think of .
Personal i go for high volts the mppt wil start faster on the day and end later in the day.
For the winter the same way it will have more performance than in the summer.

Problem being that the new panel is a 500w and there's no good way to add that to the existing 180w panels without adding a new MPPT just for the new panel.

With the voltages as close as they are, and if he's willing to pull that heavy a wire, then 5p is going to be the most effective way to do it.

 

[Suijkerbuijk]

Problem being that the new panel is a 500w and there's no good way to add that to the existing 180w panels without adding a new MPPT just for the new panel.

With the voltages as close as they are, and if he's willing to pull that heavy a wire, then 5p is going to be the most effective way to do it.

No he do not have that panel .
Its in the future update if i read it correct
So in his case i will go for a 2x200watt panels with the same volt . (Not for 1x 500watts)
That use the same space like 1 x500 watts model .

Than if his mppt can handle it.
1 stream with 2x180 +200 in series.
2 stream with 2x180 +200 in series.
Than both parallel.
Than he have a max output of 540watts in on stream . (He lose 20watts from the 200watt panel)
So both will be 1080watt : 14volts = 77a max from the mppt for charge
His own mppt can handel max 60a charge .
So he is al ready go overpanel with that mppt controller.

This is what i will do personal.

The mppt can handel 150volt input
3x40volt max panels = 120volt pv input.
So his controller can handel it.

So his mppt on 12 volt battery connect can handel max solar panels of 840watts.
On a 24 volts systeem 1680 watts panels
On a 48volt systeem 3.360watts.

 

[Rednecktek]

8amp on 180 watt panels and 25amp on 500 watt panel).

4x 180w panels and a 500w panel.

 

[Gengfawn]

Sorry if I wasnt clear in the original post but I do already have the panel.

Buying panels in small quantities where I am isn't very cost effective but I was able to get a good deal on a 500watt panel locally.

If I were to buy 2 x 200 watt panels it would have cost 1.5 times as much for 20% less output. With the 500w panel I lose about 25 watts due to the difference in voltage and a slightly higher installation cost due to increased wire gauge size.