Combine 3 solar panel systems by charge controller outputs

saadmubeen · April 2016

I have 3 300w solar panels systems... 2 300w solar panel system are connected to 165ah and 1 is connected to 2 110ah battery and each system is connected to 30amp charge controller... Each system is absolutely isolated.

My Question is can I join all the output wires of these 3 charge controllers to the load? I will connect all the positves together and the negatives together of the output, so that i get a single output of these 3 charge controllers. I think this will be a parallel connection and voltage will remain same and current will add up. Will it damage my appliances? I read somewhere that voltage is upon supply and current is drawn by load. Am I correct? I want all these batteries to charge separately by their respective solar panels as all solar panels are of different make and capacities. 2 300w solar panels systems comprises 2 150w panels where as the 3rd 300w solar panel system consists of 1 120w panel, 1 150w panel and 1 30w panel....

vtmaps · April 2016

Welcome to the forum,

Generally, there is no problem connecting several charge controllers (each with their own array) to a single battery bank.

What you are proposing is to make a single battery bank by putting the 165 ah battery and the two 110 ah batteries in parallel.

Bad idea. generally, putting batteries in parallel is not optimal design. If you must make a parallel battery bank, the batteries should all be identical (age and model). You also need careful attention to the wiring, to make sure that all batteries see the same resistance from the loads and from the controllers. As a practical matter, that is best achieved with bus bars.

--vtMaps

saadmubeen · April 2016

vtmaps said:

Welcome to the forum,

Generally, there is no problem connecting several charge controllers (each with their own array) to a single battery bank.

What you are proposing is to make a single battery bank by putting the 165 ah battery and the two 110 ah batteries in parallel.

Bad idea. generally, putting batteries in parallel is not optimal design. If you must make a parallel battery bank, the batteries should all be identical (age and model). You also need careful attention to the wiring, to make sure that all batteries see the same resistance from the loads and from the controllers. As a practical matter, that is best achieved with bus bars.

--vtMaps

Thanks. Really appreciate your response.

So you are saying if i join all the load wires of these 3 CCs and take these to my appliances, this way my batteries will also become parallel.

So CCs output is like battery terminals? I thought it wont effect batteries.

Will it also effect charging?

Can it be dangerous for my appliances??

Last question is i have 2 165ah batteries, each connected with 300w solar panel and a charge controller and both systems are isolated ... Can these two be connected the way i quoted above by joining the outputs of their CCs. These batteries are identical in every way and have same life as well.

You also said that parallel design is not optimal, why? Which design is better?

I am a noob in this regard, please bare with me.... Looking forward for your reply.....

Thanks
Saad

BB. · April 2016

Here is a good explanation of the options on how to wire a parallel battery bank:

http://www.smartgauge.co.uk/batt_con.html

Personally, I prefer (for example) two 6 volt batteries in series (6 volt @ 200 AH) for a 12 volt @ 200 AH battery bank vs two 12 volt @ 100 AH batteries in parallel (12 volt @ 200 AH).

There are a few reasons for this:

fewer battery cells to check and water (6 vs 12 cells in this case, larger battery bank can be way more cells)
easier to check batteries with simple volt meter (each 6 volt battery can be measured directly. Batteries in parallel all have same voltage--Cannot find weak/bad batteries as easily)
more wiring in parallel banks. Harder to notice bad wiring (one corroded connection will take out a battery string, but bank voltage will be OK. With series connection open, a single string bank will lose voltage).
Lead Acid batteries are relatively low resistance. Getting them to properly share current can be difficult (see link above on wiring).
Lead Acid batteries are also temperature sensitive--If not good air flow and/or bad battery, temperature differences of cells can cause charging/discharging imbalances.
When you put 3 or more strings in parallel, each string should have its own fuse or circuit breaker (more money for wiring parallel banks).

-Bill

saadmubeen · April 2016

Now, i have connected 2 CCs each with 300w solar panel array to one battery bank. How will i get the output from this system? Should i use only one CC load terminals or should i use both CC load terminals in parallel? Or, should i get output directly from the battery bank? Which is the right way.....

Also, what should be the charge voltage of both the CCs? Should all the settings of both the CCs be identical? Will one CC be superior to other CC in some way... Please explain.

Been searching for it but didnt get any solution...... Looking forward for urgent replies.

Regards
Saad

Raj174 · April 2016

The CC's should be the same make and model. The settings on both CC's should be identical and configured for the charging requirements of the battery bank. Loads should be connected to the battery with appropriate breakers or fuses. Keep in mind that not all charge controllers are made to work together. The manual or manufacturer's website will usually state that they work together if they do.

mike95490 · April 2016

Only small loads should be connected to the charge controller LOAD terminals. Large loads always connect to the battery via a proper fuse

Combine 3 solar panel systems by charge controller outputs

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