# How many batteries can run in series

Jlwaterman
I live off the grid and am looking to upgrade my battery bank. I now have 12 6v batteries. 4 are ran in parallel to make a 24v system. The rest are run in series to increase watt hours. is there a maximum amount of batteries I can run in a series?

## Answers and Replies

yungman
I live off the grid and am looking to upgrade my battery bank. I now have 12 6v batteries. 4 are ran in parallel to make a 24v system. The rest are run in series to increase watt hours. is there a maximum amount of batteries I can run in a series?

You got it mixed, you must be running 4 in series to get 24V, not in parallel.

Jlwaterman
Forgive me for the mix up. I am still trying figure out how many batteries I can hook up

Gold Member
If you add batteries in series there is not a practical limit. Your output voltage just continues to rise. I have used 450 large glass 1.2 volt lead-acid battery cells connected in series in an Uninterruptable Power System.

When you begin to put batteries in parallel you encounter the problem of differences in the batteries causing unwanted current/power flows between the cells themselves. This can become catastrophic and dangerous with possible fire, explosions, and injuries. Be sure to consult with qualified and certified engineers if you are doing home-made projects.

Staff Emeritus
Science Advisor
Forgive me for the mix up. I am still trying figure out how many batteries I can hook up
Without special monitoring, no more than 2 in parallel (i.e., side by side), and then only if they are both new and of identical manufacture and part number, and in similar state of charge. When you discharge them, only partially discharge, don't discharge until the lights go dim!

For cells in series, no more than 3 or 4, and then only if they are of identical manufacture and part number, and in similar state of charge. When you discharge a series connection of non-identical cells, the weakest cell is placed in mortal danger of having its polarity reversed. To minimize this risk, take care not to discharge anywhere near the rated AHr capacity of a series string. It would be safest to electronically monitor the terminal voltage of each 6V battery and trip the load relay if any battery voltage falls below that safe level. (I would expect some chemistrys to be more tolerant of polarity reversal than others, but I wouldn't rely on this.)

pantaz
jsgruszynski
If you add batteries in series there is not a practical limit. Your output voltage just continues to rise. I have used 450 large glass 1.2 volt lead-acid battery cells connected in series in an Uninterruptable Power System.

When you begin to put batteries in parallel you encounter the problem of differences in the batteries causing unwanted current/power flows between the cells themselves. This can become catastrophic and dangerous with possible fire, explosions, and injuries. Be sure to consult with qualified and certified engineers if you are doing home-made projects.

This may be informative. Don't do this at home...

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