Looking for some unbiased advice

[AngliaUSA]

I have a back up solar system which I am recommissioning for service.
The whole system was purchased in 1999 but only used for a few years -

A Trace DR3624 24V Inverter 3000W

Solar panels WERE 12 x 80W VLX . I need new panels with new batteries.

I was running 16 x T105 Trojans 6v in series for 24 V output to my inverter. 2 banks of 8 batteries.

I need some knowledgeable and sensible advice on what new panels to buy .. thinking of 4 x 300W panels (1200w output) and 4 x 6v 370 AH L16 batteries.

Basically I need the right batteries and panels to match to my existing electronics and back up system. I look forward to hearing from you.

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[AngliaUSA]

Here's the rest of the system parts and the roof which it will be attached to ....
Southern California @ 6500 ft ... South facing gets 8 - 10hrs of direct sun per day.
Plenty of room for panels. Thanx again for any / all advice.

[max2k]

Here's the rest of the system parts and the roof which it will be attached to ....
Southern California @ 6500 ft ... South facing gets 8 - 10hrs of direct sun per day.
Plenty of room for panels. Thanx again for any / all advice.

are you sure you want to recommission 18 year old electronics?

In case you are I think you should be OK- Trace C40 is PWM controller so you need to select some commonly available 60 cell panels with Voc around 40V max. This way you'll be able to utilize about 70% of your 1200W panel's output to charge your batteries. 1200 x 0.7 / 24V = 35A which is fine for 370Ah FLA batteries (if you meant those). During daytime system will be able to store 1200 x 0.7 x 5hrs = 4.2kWh of energy, about 50% of your planned battery bank capacity. Your battery bank might be short on capacity but it's hard to tell without knowing your load requirements.

[littleharbor]

I was running 16 x T105 Trojans 6v in series for 24 V output to my inverter. 2 banks of 8 batteries.
QUOTE]

Are you sure that's not 4 strings of 4 batteries? Yes the L-16's would be a better choice. You can get away with 2 strings of 4 batteries, if needed. 4 strings of batteries will be problematic.

If you stay with that controller you need to use 72 cell (24 volt nominal) panels. Most of the 300 watt range panels are 72 cell count. They are substantially larger than old 80 watt panels. Probably goes without saying, get some help mounting them.

[NEOH]

AngliaUSA ,

All advice is biased.

Read these Sticky Notes regarding Solar Panels and Deep Cycle Batteries ...
https://www.solarpaneltalk.com/forum...-panel-systems

[AngliaUSA]

Thanx for the advice .. when I say Unbiased ... I meant from a company trying to sell me a product ....

The history of my system dates back to the Y2K scare ... I had it up and running from 1999 to 2001 on a remote cabin in So Cal .... I sold the cabin with the solar panels attached to the roof ... new owner wanted them but not the batteries or electronics. So the guts of the system / the electronics only ever had a couple of years of light use before being disconnected and the whole thing put into storage at the back of my garage. Fast forward to today I have a new weekend cabin and want to install the old back up solar system.

Hence the need for new batteries and new panels. I had 12 VLX 80W panels ... 2 banks of 6 , 12 volts from each bank, I think, putting 24vots to the Trace C40 charge controller .. but I would need to check all that .... Pretty sure I can set up the C40 to accept, 12, 24 or 48 volts.

I am reasonably confident that the set up will work with new panels and batteries ... but there isn't really an easy way to bench test the electronics , prior to purchasing and hooking those up ....

Worst case scenario .. it doesn't work and I will need a new inverter and charge controller . I have $2k set aside for that .. just in case.

So I had 960 W of PV .... so If I am aiming for 1KW - 1.5KW of new PV are there any specific panels you'd recommend ... I'd rather 4 x 300 W panels than 12 x 100W panels just for ease of installation etc.

Cheers.

[NEOH]

AngliaUSA ,
If the Voc of the 4 x 300 Watts Panels on a cold day does not exceed the Inverter's Max Input Volts, then why not ?
300 Watt Canadian Solar may need two parallel strings, of two PV in series = 65 Vmp ?

The Charging Amps is 40 A ( 1,200 PV Watts / 30 Volts ) which is enough to charge the 370AH L16 Bank 's at C/10 ?

[max2k]

AngliaUSA ,
If the Voc of the 4 x 300 Watts Panels on a cold day does not exceed the Inverter's Max Input Volts, then why not ?
300 Watt Canadian Solar may need two parallel strings, of two PV in series = 65 Vmp ?

The Charging Amps is 40 A ( 1,200 PV Watts / 30 Volts ) which is enough to charge the 370AH L16 Bank 's at C/10 ?

with MPPT controller... OP original one is PWM. Besides Voc of the panels is not relevant of inverter's Vin max as inverter takes that from the batteries.

[max2k]

Thanx for the advice .. when I say Unbiased ... I meant from a company trying to sell me a product ....

The history of my system dates back to the Y2K scare ... I had it up and running from 1999 to 2001 on a remote cabin in So Cal .... I sold the cabin with the solar panels attached to the roof ... new owner wanted them but not the batteries or electronics. So the guts of the system / the electronics only ever had a couple of years of light use before being disconnected and the whole thing put into storage at the back of my garage. Fast forward to today I have a new weekend cabin and want to install the old back up solar system.

Hence the need for new batteries and new panels. I had 12 VLX 80W panels ... 2 banks of 6 , 12 volts from each bank, I think, putting 24vots to the Trace C40 charge controller .. but I would need to check all that .... Pretty sure I can set up the C40 to accept, 12, 24 or 48 volts.

I am reasonably confident that the set up will work with new panels and batteries ... but there isn't really an easy way to bench test the electronics , prior to purchasing and hooking those up ....

Worst case scenario .. it doesn't work and I will need a new inverter and charge controller . I have $2k set aside for that .. just in case.

So I had 960 W of PV .... so If I am aiming for 1KW - 1.5KW of new PV are there any specific panels you'd recommend ... I'd rather 4 x 300 W panels than 12 x 100W panels just for ease of installation etc.

Cheers.

just pick any ~300W 60 cells panels with Voc around 40V and Vmp around 36V. Your current PWM charge controller would produce about 33A of charging current from 4 such panels in parallel. Failing to work you'll be able to replace your charge controller with MPPT one and extract full 1200W power (40A charge current) from them by connecting panels in series or some mix of parallel/series depending how high input voltage your new charge controller will allow.

[AngliaUSA]

Thank you sir(S) much appreciate the input. I'll keep you posted as to how I get on.

[max2k]

Thank you sir(S) much appreciate the input. I'll keep you posted as to how I get on.

BTW, my comment relates to 24V battery bank which consists of 4x 6v 370Ah L16 batteries in series as you originally stated.

[littleharbor]

just pick any ~300W 60 cells panels with Voc around 40V and Vmp around 36V..

Max2k, why would you recommend 60 cell panels for a PWM controller? Granted they do make 300+ watt 60 cell premium panels, the majority of the 300 watt panels are 72 cell, 24 volt nominal. The 300 watt 60 cell panels I'm finding are running 32.0 Vmp Can you show an example of a 40 Voc. , 36 Vmp. panel?

[max2k]

Max2k, why would you recommend 60 cell panels for a PWM controller? Granted they do make 300+ watt 60 cell premium panels, the majority of the 300 watt panels are 72 cell, 24 volt nominal. The 300 watt 60 cell panels I'm finding are running 32.0 Vmp Can you show an example of a 40 Voc. , 36 Vmp. panel?

I can't, you're correct they're 32V Vmp which I think is even better for PWM controller in terms of panel utilization as 32V will still be enough to charge 24V lead acid battery and the charge voltage (28V?) would be closer to 32 V Vmp.

[littleharbor]

Not necessarily in hot conditions, especially when you want to equalize in the 31 volt range. Granted the latest higher efficiency cells are raising voltages above what they used to be and you may be able to get away with a 60 cell, 32 Vmp. panel. Personally I still feel a 72 cell panel is the proper cell count for straight PWM charging of a 24 volt battery.

[max2k]

Not necessarily in hot conditions, especially when you want to equalize in the 31 volt range. Granted the latest higher efficiency cells are raising voltages above what they used to be and you may be able to get away with a 60 cell, 32 Vmp. panel. Personally I still feel a 72 cell panel is the proper cell count for straight PWM charging of a 24 volt battery.

I see what you mean: at +45C surface temperature 31Vmp panel with -120 mV/C coefficient will produce only 28.6V which is only enough for charging without room for equalization. Hope OP gets himself MPPT controller eventually and all this would become irrelevant . Short of that 72 cell panels would be way to go.