Battery Wiring

[scottwvyc]

This is a picture of my deep cycle 8D house batteries on my 37c. I am about to install an inverter, and one of the electricians that looked at the job said that these batteries are wired incorrectly and will not draw down evenly. Just wondering what other members of the forum think? Thanks Scott.

 

[Boatsb]

2 batteries in parallel will share the load. Since they are hooked up in parallel permamently I can't understand how one could draw down more than the other and not equalize. Either your electrician is a genius like the guys who ran the financials for Fanny and freddie or he made a mistake.

 

[Beckytek]

I don't see the problem. Ron

 

[Sonny]

i'm interested in hearing the electrician's explanation and remedy, because that looks perfectly normal to me.

 

[Trojan]

The only thing that could change the draw would be unequal lengths of cable to each battery. The only difference as wired would be in the cable resistance and that would be extremely small. Are you sure he was an electrician ?


BILL

 

[Sonny]

i would also like to know his price to "fix" the issue!

 

[Pascal]

that's an easy one...

ideally, when you parallel multiple batteries you want to have the + hooked up at one end, and the - hooked up at the other end of the bank.

this will spread the loads more evenly, otherwise the battery to which the loads are connected will work harder.

It's not that critical with only two batteries, but becomes increasingly important as the number of batteries increase. It's easy to fix if the cables are long enough... just move the black cable from the left batteries to the neg terminal on the right batteries. If the cable isn't long enough to stretch, leave it alone, it's not worth it.

 

[captainwjm]

Pascal is exactly right!

 

[scottwvyc]

Thank-you guys!

 

[REBrueckner]

I agree with Pascal but would go even further: your current cabling is just fine...in other words even if there were a tiny, tiny difference in theoretical performance, likely cable flaws (such a a broken strand) , loose connections, differences in resistance of connections, minor corrosion, and that fact that batteries nor individual cells with batteries never "age" identically because of slight manufacturing differences...all makes a foot or two of cable difference irrelevant....

My own banks of start batteries are cabled as shown in your diagram as supplied from Hatteras....and if it made any difference for even heavy (high amperage) loads Hatteras would have never cabled start batteries as you show. ...
and in fact ,when I added a third battery bank I happened to cable it as you show.

Put that recabling, if you wish, at the extreme bottom of your "to do" list!!!

 

[Pascal]

Rob, as i said, i dont' think it makes a difference with jsut two batteries. I think it will on large banks (inverter) with 3 or 4 batteries / sets

 

[Trojan]

Having the cables all the same length and feeding to a common point will accomplish the load sharing. As will as reversing the cables. But with using good short cables, I doubt you could detect the difference. It would be so small you probably would need an amp meter graduated in micro amps. Not worth the effort. I hope you were impressed by your electrician


BILL

 

[OldLimey]

There is good information here about how and why to connect batteries in a bank.

http://www.smartgauge.co.uk/batt_con.html

 

[MikeP]

Oh Great...a UK Site! Wiring explanations brought to you courtesy of the country that produced Lucas electrics!

http://www.kitcar.com/articles-kitcar/humordept/lucas-prince.html

OK sorry, having owned several old British cars and bikes I couldn't resist. I'm sure things are different now!

 

[Pascal]

Mike beat me to it...

that is a good page though... makes a lot of sense to use the 3rd option, event though nr 2 is ok as well. The only thing with #3 is that you need add a pair of studs for the connection, not a big deal.

good info, thnks for posting.

 

[REBrueckner]

You can closely approximate the correct third solution by connecting the external cables to one of the center batteries.

Note however, that if you use this approach with an inverter you may now have a longer than recommended cable between the inverter and the initial battery.

 

[MikeP]

OK, that explanation addresses parallel connection but all the bats on the oem 53 are in series. I can't see any way that there can be any "wrong" way to wire them since any change would make them not in series any more and the voltage would be wrong anyway, right?

 

[rrrestorer]

Ah yes! Lucas refridgerators,,,, the reason the British drink warm beer!

 

[TedZ]

Damn poor day you don't learn something. Nice catch Pascal.

Ted

 

[OldLimey]

"Oh Great...a UK Site! Wiring explanations brought to you courtesy of the country that produced Lucas electrics!"

But how else could us UK amateurs have developed our extensive experience in fixing stuff that's broke!

Mind you, I did buy an American boat......

Hugh