Batteries--series or parralel?

[Anjinsan]

I want to hook-up 4 batteries to my charger and circuit board. Should this
be in series (-) to (+)---or parralel(all (+) together)? And what about the voltage? Won't 1 way be 12-volt, and the other 48-volt?
Thank-you to anyone who can straighten me out.
Anjinsan

[erps]

If they are 12v batteries, you will want to hook them up in parallel.

[motion300]

series will give you 48 volts same amps, parallel gives you 4x the amps and 12 volts

[Stillraining]

Yes parallel retains same voltage... series combines the voltages.

OK Double post...Jinks you owe me a soda..

[Anjinsan]

Thank-you, gentlemen,
I get it.
Pure information that helps me.
I am glad I joined sailnet.
Anjinsan

[pedcab]

Originally Posted by erps

If they are 12v batteries, you will want to hook them up in parallel.

The only problem being that an internally shorted or otherwise damaged battery will drain all the others in the bank.

Personally I don´t see the point on having a bank of batteries, based on the excuse of reliability, only to find out latter that the battery bank is only as good and reliable as the worse battery of the bunch...

My advice to anyone about battery banks aboard boats is DON'T CONNECT THEM TO EACOTHER AT ALL.

Instead you can have them independently interconnected via a battery selector switch with the obvious advantages in the effective increase in reliability.

As for the charger, you can wire it the same way (through a selector) or just buy a multiple output unit...

[erps]

Personally I don´t see the point on having a bank of batteries, based on the excuse of reliability, only to find out latter that the battery bank is only as good and reliable as the worse battery of the bunch...

Good point. I can see a benefit of having a means to disconnect a large bank if your boat is unattended for a length of time. The flip side of the coin for a large bank is that a battery's life depends partly on how much you deplete it. The theory goes, that if you consume X number of amps between charges that you would ruin a battery with too small an amp capacity in just a few discharges but if you put together a large enough bank, the bank will give you back more discharges at a lower cost than replacing ruined batteries.

[oldironnut]

Also be aware that regular "starting" batteries such as in automotive applications are more easily damaged by often charge-discharge situations. Deep cycle batteries are more suitable for applications where they are likely to be totally discharged. Another thing to watch out for is the sometimes confusing term "marine battery". It is often thought to mean "deep cycle" when it may be either a starting battery or a deep cycle battery.

[Bene505]

IMHO, I think the advantages of increasing the size of your battery bank outweigh the risk of one battery going bad and draining the others.

By connecting multiple, similar, same-age batteries in parallel you are extending the life of your batteries more than is immediately obvious, due to the decrease in the peaks of current felt by each battery and by reduction in peaks of % discharge felt by each battery. And you'll get more available power also.

And isn't it the abuse (i.e., big peak % discharges) that actually causes a battery to go bad in the first place? So you'd be directly addressing the "battery goes bad" risk too.

So connect them up in parallel, cover them to prevent screwdriver-across-the-terminals accidents, and enjoy.

Regards,
Brad

[Architeuthis]

Having replaced battery banks with hundreds of batteries we looked into these questions and our basic conclusion was that the best is buying single cell batteries of the ampacity required.

Cells fail. A single cell failing will sometimes take out the bank as they can fail explosively. These failures are the result of an open circuit and are not as common as a short circuit. A single cell short circuit means the bank will continue to function at a lower voltage.

Sometimes for practical or cost reasons you do not want to use that configuration. For example when a single cell becomes so heavy it cannot be handled safely then it is better to go with smaller cells in parallel and series to get the voltage and ampacity required.

When it comes to sailboats the best option, individual cells, may not be possible due to how the boat is made. That means that practical considerations will outweigh what is best for the batteries.

For most modern well equipped boats the idea battery bank size would take up the whole boat. So we use a variety of compromises and charging systems to offset that.

The result is those who are giving exact answers are…well exact answers are what people like so they are doing what people like but those banks are not going to last the 15 plus years that I have seen in well designed banks.

Battery bank life is one of the costs of banks on boats. Reliability is another.

General rule would be to fit as many batteries as you can fit, or want to buy, or want to lug around. Then break them up into banks to get increased reliability and the ability to mix banks of different ages and capacities. Then plan to replace them depending on condition which will vary depending on many things, which includes use.