Connect multiple batteries

[math55]

I am all new to the solar world. In my cabin which I just bought I have 2 300W panels = 600W. At the moment, these are connected to a 12V | 80Ah car battery. I was wondering if its somehow possible to charge multiple of those batteries by putting more batteries in series.

What I want is to charge multiple batteries one after the other and also take the power from them one after the other. I saw videos where it was done that way, just not sure if it needs more equipment or if I missed something.

Thanks for helping a newbie !

 

[SamDeleted]

Hi Matt

That is getting complicated fast

First off, if you've got batteries in series the voltage doubles , 2s = 24v, 4s = 48v

So you'd need to have equipment designed for your chosen voltage




In my opinion you are better off putting the batteries in parallel, charging and discharging all at the same time equally

 

[SamDeleted]

12V | 80Ah car battery

I'm sure you already know, but car batteries are not really suitable for this application. They'll work but won't last long


If possible try to find some deep-cycle lead acid/AGM/gel batteries. They come up cheap second hand, ex-telicoms, folklift truck batteries, ex-UPS

 

[Rednecktek]

I'm sure you already know, but car batteries are not really suitable for this application. They'll work but won't last long


If possible try to find some deep-cycle lead acid/AGM/gel batteries. They come up cheap second hand, ex-telicoms, folklift truck batteries, ex-UPS

WallyWorld DC27 deep cycle batteries are 110Ah for about $100 out the door with tax & core and will give you probably about 3x the capacity. If you get a pair of those you'll have about 1280 watt hours of capacity for $200. I like to tell people that if you might destroy something, destroy something cheap!

I was wondering if its somehow possible to charge multiple of those batteries by putting more batteries in series.

Parallel, not series. Positive to positive to positive and negative to negative to negative. Series is positive to negative to positive to negative. Series adds voltage together, parallel adds amperage/capacity.

What I want is to charge multiple batteries one after the other and also take the power from them one after the other.

Unless you're going to watch a meter and swap cables all the time, go with parallel, preferably to bus bars if you get 3 or more batteries involved. All the batteries will discharge together and all charge back up together. It's healthier for the batteries, easier to wire, and gives you more amperage draw capacity because each battery will be sharing the load.

 

[math55]

I get it, what would be the advantage of putting them in series compared to parallel? When I put the batts parallel, will they last 3 times longer when they are loaded? So if I get 3 hours of running time with my devices, will I get 9 (more or less)?

Thanks !

 

[Steve_S]

Batteries in SERIES increase the Voltage but not the amount of energy stored (Amp Hours).
Batteries in PARALLEL increase Storage (AH) but not Voltage.

Standard Auto-Grade batteries actually have very thin lead plates and are not designed for Energy Storage use and will wear out fairly quickly. Energy Storage Lead Acid batteries have much thicker plates and are designed for purpose... BUT these are coming to end of life as LFP (Lifepo4) battery prices have dropped significantly and the ability to use 100% versus 50% makes it an all around win.

Please refer to this document from Victron on Battery System setup & configuration.

https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

 

[Rednecktek]

I get it, what would be the advantage of putting them in series compared to parallel? When I put the batts parallel, will they last 3 times longer when they are loaded? So if I get 3 hours of running time with my devices, will I get 9 (more or less)?

Thanks !

Exactly. If you put 3 in series you'd have a 36v bank that would last about 2 seconds on your 12v inverter. ?

 

[Steve_S]

ALSO Very Important !
Remember to have a Fuse between Battery System & Inverter !
See template image below showing batteries in parallel in a standard component based system.
ALSO for future reference, it is suggested to never exceed 250A draw from a battery system by default.
@ 250A Draw, 12V can handle 3000W, 24V can handle 6000W and 48V can handle 12,000W.

 

[math55]

Batteries in SERIES increase the Voltage but not the amount of energy stored (Amp Hours).
Batteries in PARALLEL increase Storage (AH) but not Voltage.

Standard Auto-Grade batteries actually have very thin lead plates and are not designed for Energy Storage use and will wear out fairly quickly. Energy Storage Lead Acid batteries have much thicker plates and are designed for purpose... BUT these are coming to end of life as LFP (Lifepo4) battery prices have dropped significantly and the ability to use 100% versus 50% makes it an all around win.

Please refer to this document from Victron on Battery System setup & configuration.

https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

Thanks for the answer. Why would I want to increase the voltage?

 

[Tomthumb62]

Thanks for the answer. Why would I want to increase the voltage?

The main advantage of increased voltage is you can get away with using smaller wires.

12v is low voltage but if you want to send 1200W of energy through, you need 100A. Higher amps requires thicker copper wiring. Which is expensive.

At 24v, you only need HALF as thick of copper wire to send the same 1200W. The amps required will only be 50A, so it’s possible to use the thinner wire.

BUT there’s a serious consideration of higher voltage. At 12v, a shock to the human body (wet your fingers and touch + and - terminals at once) is merely annoying. At 24v it’s much stronger. At 48v, you’re into serious hurt yourself territory.

 

[fpgt72]

I am a noobie myself but can add a few things.

There are places on the internet that will tell you for this amp draw use this size of wire. And all wire is not created equal.