House battery bank question

[wild1]

My house battery bank consists of two 100 amp hour deep cycle batteries wired in parallel. They are side by side and are joined with heavy gauge jumpers.My question concerns the best position to attach the positive and negative leads. I currently have both the positive and negative running from the same battery. This is the setup shown in many wiring diagrams but I have also read that the better system is to connect the positive lead to one battery and the negative to the other. What do you think is the most effective system. Thanks for any help you can offer.

 

[ntsqd]

Do you need 12 volts or 24 volts?

Positive to positive, negative to negative yields 12 volts with the combined amp-hours from each battery.

Positive to negative yields 24 volts.

 

[wild1]

Sorry I wasn't clear on my question. The batteries are wired in parallel so they are producing 12 volts and 200 amp hours. My question concerns the outputs from the batteries to the distribution panel.I currently am running both the positive and negative outputs from one battery but am wondering if it is better to run the poitive from one and the negative from the other. Hope that this clarifies my question. Thanks

 

[cnynrat]

There is a theory that it is better to take the positive from one battery in the bank and the ground from the other. The thought is that might help ensure current is drawn from both batteries equally. Frankly, I don't think it would matter much, particularly if you are using the right guage wires. I think electrical differences, primarily small differences in the internal resistance of the two batteries, will be the dominant factor in determining how the batteries behave in this configuration.

IMHO, dual batteries wired in parallel is an approach that has many problems with it, but that's another question.

 

[keezer37]

That's what I have seen, for the sake of a balanced circuit, take one lead from one battery and one from the other.

 

[wild1]

Thanks for the insights, I switched the wiring to the recommended setup. It is not quite as tidy but it does seem reasonable that it would provide better balance. I tend to agree that the two battery approach is probably not the best method to gain amp hours but the batteries I used had a small enough footprint to fit into a spot that one large battery of comparable output wouldn't. They also allow the option of wiring them in series for 24 volts and using a battery powered welder for emergency repairs.

 

[Peter_n_Margaret]

In theory..........make sure each battery gets identical treatment.
In practice that will happen if the cables are heavy enough to eliminate any voltage drop.

Another method (called STAR connection) is (in theory) even better, is to take a heavy wire from each positive to a common point and take the power from that point. Each heavy wire should be identical in length and termination. The earths are likewise connected.
The STAR method may be better if larger numbers of batteries are involved.

In all cases use good quality terminals that are properly crimped to the cables.

Cheers,
Peter

 

[whatcharterboat]

That's what I have seen, for the sake of a balanced circuit, take one lead from one battery and one from the other.

This is common practice in the renewable energy and marine electrical scene here. I do seem to remember studying this back at college too and was taught this as best practice. As for one battery vs 2 to gain amp hour storage >> sure one is more efficient but don't feel too bad about it. The difference is hardly worth worrying about and sometimes there is just no other option due to the physical layout of the battery compartment.

Of course as someone else just said here >> always make sure your connections are good. I'm sure you have access to good battery care products such as "CRC Battery Terminal Maintenace Spray" , "CRC Battery Terminal Protector Spray" and "CRC Electro Shield".

Regards John.

BTW Hi Peter

 

[Peter_n_Margaret]

BTW Hi Peter

Hi John......

Cheers,
Peter