Wiring In Series (pro vs con)

[john61ct]

And truly large banks are routinely blocks of 2V cells, each barely maneuverable.

I agree two parallel strings do give some redundancy when critical safety systems far from shore make that a priority.

But too many interconnections definitely create lots more potential points of failure.

[thomm225]

Originally Posted by capt-couillon

External or internal connections are academic.

I'm thinking internal is much better.

External connections on batteries located on boats is where most of your problems occur.

So the few connections there are the better..........

[ramblinrod]

Originally Posted by Cheechako

Hmmmm... so a 12V battery is really 6 x 2 volts cells in series right? So does this mean your 12V battery is only the amperage of one cell?

Absolutely, unequivocally correct.

It is the law!

(Kirchoff's Law actually.)

[a64pilot]

Originally Posted by PaulinOz

How long would a 10 volt bank last with 12 volt chargers connected?

That is why I said I'd want programmable chargers, all four of mine are now.
Plus you usually have two banks, if you have two banks then to really get down to 10 V house bank, you would have to lose two cells.
I likely won't run a series bank of two volt batteries, but I see no compelling reason not to if you really had a reason to.


Many ways to skin a cat

[ramblinrod]

Originally Posted by a64pilot

Plus you usually have two banks, if you have two banks then to really get down to 10 V house bank, you would have to lose two cells.

The post that raised my ire, suggested a 12 Vdc house bank consisting of only one series string of 6 x 2 Vdc cells, as the best way to go (and then became insulting when I suggested that is not a great idea).

[mickelsen]

That cleared away some of the mist.
Thanks, Peter

[Cheechako]

Originally Posted by ramblinrod

Absolutely, unequivocally correct.

It is the law!

(Kirchoff's Law actually.)

Yeah, I was scratching my head a bit obtusely about the post:

"Comment: when batteries are connected in series you add terminal voltages, but can only draw as much current as a single battery in the series can offer by itself.
Example:Three 4V batteries connected in series at 450A capacity each will yield 12V, but the series string can only produce 450A."

Which means... not much....as cells are in series..... some internally... some not.

[Cheechako]

Originally Posted by camel2012

Just curios. has anyone lost a battery cell individually, or a single 2, 4, or 6 volt battery? I've shorted a cell in a lab but only after repeated electrical dump abuse that I would never do on a boat. Wondering how likely this situation is for planning purposes.

I've had 2... hmmm... maybe 3 marine batteries with a shorted cell. Coincidentally two of them were 8D types and not that old. One about a year old and one about 3 years old.

[Suijin]

I think the best thing for the OP to do is wait until the 12v product is no longer backordered lol.

[rwidman]

Originally Posted by camel2012

Just curios. has anyone lost a battery cell individually, or a single 2, 4, or 6 volt battery? I've shorted a cell in a lab but only after repeated electrical dump abuse that I would never do on a boat. Wondering how likely this situation is for planning purposes.

I have experienced both shorted and open cells in 12 volt batteries. It happens.

Wet or AGM cells are nominally 2 volt so a 4 volt battery is two 2 volt cells in series (internally). A 6 volt battery is three cells and a 12 volt battery is six cells in series (internally).

Any of these combinations will work but 2 and 4 volt batteries will be difficult to find if you need one right away. 6 and 12 volt batteries are available in just about any town.

The technical stuff: The jumpers you make to wire cells in series have more resistance than the internal jumpers in a manufactured battery. The combination you cobble together will have a higher internal resistance and a more significant voltage drop at high loads. This gives a slight edge to a 12 volt battery.

Wiring batteries in series does not increase the amp hours available. Wiring them in parallel does.

[rwidman]

Originally Posted by Cheechako

Hmmmm... so a 12V battery is really 6 x 2 volts cells in series right? So does this mean your 12V battery is only the amperage of one cell?

That is correct. Adding more cells in series increases the voltage but not the available amperage.

[rwidman]

Originally Posted by Suijin

I think the best thing for the OP to do is wait until the 12v product is no longer backordered lol.

Or buy a different brand of battery.

[john61ct]

Very few true deep cycle batteries are even available in 12V.

If the same form factor as automotive starter or pseudo-DC "dual purpose", then very very likely that's what it is.

Labels like "marine" and "deep cycle" are lies lies lies 99.999% of the time in big box retail.

I realize none of this applies to the OP, just reinforcing for posterity, relative noobs coming across the thread.

And perhaps a reason why some see batteries with internal damage more often than they should.

See Maine Sail's excellent treatise, well deserved rant, on the topic.

Only exception I've seen are 6V golf car batteries.

[ramblinrod]

Originally Posted by john61ct

Very few true deep cycle batteries are even available in 12V.

If the same form factor as automotive starter or pseudo-DC "dual purpose", then very very likely that's what it is.

Labels like "marine" and "deep cycle" are lies lies lies 99.999% of the time in big box retail.

I realize none of this applies to the OP, just reinforcing for posterity, relative noobs coming across the thread.

And perhaps a reason why some see batteries with internal damage more often than they should.

See Maine Sail's excellent treatise, well deserved rant, on the topic.

Only exception I've seen are 6V golf car batteries.

Ummmmm, careful.

According to East Penn (one of the largest manufacturers of FLA batteries in the USA), their Grp 27 "start" is a different design than their Grp 27 "dual purpose", is a different design than their Grp 27 "deep cycle".

Trojans (one of the better GC2s) may last longer than cheap Grp 27s, but they are more expensive too. On a cost / a-hr (real life) cycled analysis, I don't know if they actually represent better value for money.

Will a bank of cheap GC2 last any longer than a bank of cheap Grp27 "Deep Cycles", everything else equal? The jury is still out on that one.

[mickelsen]

You guys are terrific. Rock on!