Interesting Article on Interconnection of Batteries

[Dockhead]

This article on the importance of the scheme of interconnection of batteries:

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

had some things in it which were quite surprising to me. That the current drawn from individual batteries in a big bank can be so hugely different based on slight differences in how they are interconnected.

I am this weekend in Cowes on my boat installing my new Trojan batteries. Bright sunshine and cold! The sea is calm so I might blast across the Solent in the dinghy to see my new mooring in the Hamble

My house battery bank was actually two banks of four batteries each in two different places a good 20 feet away from each other.

The former individual banks are in fact wired up the way it is recommended in the article, but obviously there is no good balance -- in the way the article talks about it -- between the two former banks. The forward former bank has bow thruster, windlass, and four electric winches connected to it. The aft former bank has all the house loads. They are interconnected so that I can use the whole capacity of both banks. I guess, if the article is correct, that there will be a very large imbalance between the two former banks, with respect to any particular load, but probably they will both stay in balance inside themselves -- I mean among the four batteries of which each one consists. I guess that should be ok, but I'm still trying to digest the significance of this article. I would be interested to know what anyone else thinks.

[Lagoon4us]

Wow that's quite surprising!!! There's lots of other good info there too, Thanks....

[MacG]

I have two series of batteries: The one what is called the "Housebank" and the batterie(s) for starting the engine.
I can choose from the main switch which bank should be loaded. The simple fact that there is a distinctive difference between the two banks - different amperage and different make - is the basis that I keep those two fully separated. In no way they are interconnected. The charger charges either bank one or bank two, but never both banks at the same time. That would' t work because of the different amperages.
It is therefore a very good article and actually fully understandable. I bookmarked the page. Thanks Dockhead.

[goboatingnow]

Of course what Charles sterling ignores, is that there are far more differences in battery internal impedance and other characteristics, then interconnection resistance. Hence his model is very misleading.

Dave

[s/v Jedi]

This article is correct. The theory and calculations are sound, and measurements in a test configuration were performed to verify the math. That test did verify it.

I have done similar tests with similar results. I use 6x Trojan L16 batteries and noticed the big differences in load with my clamp-on DC Amp-meter. When I replaced the batteries with 6 new ones, I therefor decided to install two extra busbars to create the (option 3 in the article) setup that solves this.

Here is a picture of how simple ths is; every lead between battery and bysbar is exactly the same incl. length:


ciao!
Nick.

[Rhapsody-NS27]

Nice link. After reading through, I probably would have connected as the first example shows but I guess I know better now.

Thanks, This is helpful.