More solar array power with PWM than MPPT. Why?

[Mike90250]

Might I suggest the Tristar MPPT 60A instead of the 45A. With the 60A you can expand with more panels if needed, AND it has a web interface so you can see what is happening from your computer.
Both are shown in the catalog with the optional meter installed instead of the blank front panel.

[SunEagle]

Why would I complicate my life if I can simplify it? 8 x 435ah batts is more than enough for me in the future. The last thing I need to see is how many more panels I will need to insure my 8 batts are properly charged and if the controller I chose will handle the increase in panels.

I have the other option, again in 24V, to buy 8x225ah to start with and then buy 4 more. 12 batts in total sound better than 16 and maybe I can stick with the TSMPPT45.

Just remember that adding new batteries to an older set will reduce the life of the new ones because the old ones are weaker and will cause issues.

If your plan is to expand the system then go with the 60amp CC as Mike has suggested.

[dapago]

Yes I just sent an email to my dealer/supplier to check the CC60 price. They sell here the 45 at nearly $800 so I imagine the 60 will be @ nearly $1000. A LOT because of import tax.
About adding new batteries to older ones, is there a minimum time where adding new ones will not create issues? lets say 12 months after

[SunEagle]

Yes I just sent an email to my dealer/supplier to check the CC60 price. They sell here the 45 at nearly $800 so I imagine the 60 will be @ nearly $1000. A LOT because of import tax.
About adding new batteries to older ones, is there a minimum time where adding new ones will not create issues? lets say 12 months after

Depends on the type of battery but in most cases adding new ones to an existing set that has been used for only a few months could lead to unbalanced charging and discharging.

That is one of the biggest cons of building an off grid solar battery system. If you do not size it right the first time most people have had to replace all of the batteries at the same time to a bigger system.

Adding new to the old will work but it will also reduce the life span of the new ones to less then what the manufacturer has stated.

[dapago]

Well. I will have to take that in consideration. Thought that I could add batt without issues

[SunEagle]

Well. I will have to take that in consideration. Thought that I could add batt without issues

Most people that have not built and owned a solar battery system also think there should not be any issue doing that.

Although from what others have stated and a little hands on experience for myself adding new battery to increase an existing system is not a good action. Think of it similar to the saying about "an old bad apple ruining the rest".

[dapago]

I have heard that most people ruin there first battery bank. Apart from the $ I have available for my first solar system, I can hardly afford 4 batts and definitively not afford to ruin 8. I will of course take very much care of my system trying to learn reading and asking and maybe with luck everything will be fine.

Without any doubt I will take in consideration your advice and maybe delay the installation of my system until I can get more $ and have a proper one install. In the meantime I could stick with the generator for a bit longer (cost money but does not ruin my cash flow).

[Sunking]

I love this post, and I have an additional question. Is there a reason why all examples all online calculators we can find on the internet are restricted to 48Vdc?
My first reaction would be to have the highest voltage and the lowest current where I would consider 100-125A as a MAX value.

Once you go above 50 volts nominal on the battery, Enclosure Rules change significantly. Above 50 volts all live parts have to be inaccessible. That would mean putting your batteries in cabinets.

Voltage and current do come into play for a given power level. The problem child is current as it is the one aspect that makes things really expensive, dangerous, and requires great attention to detail. If possible, and it is almost always possible is to keep currents to 80 amps or less. Above 100 amps is going to require some large expensive wire (greater than 6 awg) tooling, and skills to work with. Get it wrong which is easy to do, and you have FIRE.

These are things the OP does not understand or otherwise he would never ever consider using PWM controllers of 12 and 24 volts. It will cost him thousands of dollar more and a good place for a FIRE.