Adding Batteries to Existing Battery Bank

[dbrfan]

I'm looking at building a 16s bank, so 16 - 3V cells in series to make 48V. I've read that adding batteries in parallel is ok for 2p or possibly 3p, but ideally not more. I understand that adding a string in parallel would be adding another 16s for a total of 32 cells.

If I have my 16s setup, then is it possible to add groups of batteries in parallel in a quantity less than another 16? I know that I need 4 cells to make another 12V battery, so is it possible to add 4 cells to the 16s setup in parallel to maintain the 48V? If so, then how are the amp hours calculated?

 

[snoobler]

Welcome to the forum

I'm looking at building a 16s bank, so 16 - 3V cells in series to make 48V. I've read that adding batteries in parallel is ok for 2p or possibly 3p, but ideally not more. I understand that adding a string in parallel would be adding another 16s for a total of 32 cells.

If I have my 16s setup, then is it possible to add groups of batteries in parallel in a quantity less than another 16? I know that I need 4 cells to make another 12V battery, so is it possible to add 4 cells to the 16s setup in parallel to maintain the 48V? If so, then how are the amp hours calculated?

If you're saying the first 4 cells of the 16S battery are in parallel with the 4 new cells, then your first 12V would have 2X the capacity of the other 36V. It is very critical that all components in a series string have the same capacity.

Most manufacturers insist that you limit parallel strings to 4 or less. Personally, I disagree. If you can verify that all strings in a parallel bank are carrying current that does not exceed their specification, then there's no harm.

All batteries in a bank should be connected with best practices whenever possible. "Wiring" in link #2 in my signature.

 

[dbrfan]

That makes perfect sense. I wasn't thinking about the changing the capacity of one out of the 4. Thanks for the quick reply.

 

[ND3U]

Okay. Interesting stuff. I am trying to figure out the proper method of adding capacity to a battery bank. Lets say I have a 12v 1.2kw battery (just for arguments sake). I want to increase storage capacity. What is the recommended method of adding batteries to the system without changing the voltage? I'm still trying to wrap my head around series and parallel connections and have a very basic understanding of it. Diagrams are most appreciated as I am more of a visual learner. Thanks all.

 

[time2roll]

I'm looking at building a 16s bank, so 16 - 3V cells in series to make 48V. I've read that adding batteries in parallel is ok for 2p or possibly 3p, but ideally not more. I understand that adding a string in parallel would be adding another 16s for a total of 32 cells.

If I have my 16s setup, then is it possible to add groups of batteries in parallel in a quantity less than another 16? I know that I need 4 cells to make another 12V battery, so is it possible to add 4 cells to the 16s setup in parallel to maintain the 48V? If so, then how are the amp hours calculated?

Once you are operating at 48 volts the added battery needs to be a full 48 volts. So plan on adding 16 cells at a time. Possibly best to just build a second battery to run in parallel. I would not want to break down the 16s to make a 2p16s just to save on getting a second BMS.

 

[time2roll]

Okay. Interesting stuff. I am trying to figure out the proper method of adding capacity to a battery bank. Lets say I have a 12v 1.2kw battery (just for arguments sake). I want to increase storage capacity. What is the recommended method of adding batteries to the system without changing the voltage? I'm still trying to wrap my head around series and parallel connections and have a very basic understanding of it. Diagrams are most appreciated as I am more of a visual learner. Thanks all.

If you connect that first 12v battery to a bus..... additional parallel batteries can be connected to the same bus.

 

[Goboatingnow]

A direct permanent paralleling of LA and LFP is a bad idea. Li bulk charging overcharges LA. The high standing LFP voltage constantly over charges the LA. Over time the combination ruins the LA. The other thing is of a LA cell falls it can then be subject to large current flows

At a minimum fused should be installed inter battery.

Worth nothing that on boats ABYC and ISO largely forbid paralleling chemistries