Tap onto 6V batteries in parallel

Hi All,

I have 2 sets of 6V batteries in parallel (2 in each battery box). The PO had 5 positive leads off one battery in the 2nd battery set. Can you tap off the positive from the 1st box? That was a finding by the surveyor (too many leads on one post).

Dave

Yes but it isn’t the proper way. Run a lead to a terminal strip and then you can tap off the terminal strip as much as you want

Dave_E said:

Hi All,

I have 2 sets of 6V batteries in parallel (2 in each battery box). The PO had 5 positive leads off one battery in the 2nd battery set. Can you tap off the positive from the 1st box? That was a finding by the surveyor (too many leads on one post).

Dave

Click to expand...

Yes, if the loads are reasonable. If the two sets of 12V batteries are truly in parallel, and have a large enough cable connecting them, then the two positive posts are essentially at the same "potential" and are all one battery.

Again, this would not be true if the loads are large, e.g. >0.25C, in which case it is not a black or white threshold, either.

Theorists may argue minutia, but for all practical purposes, yes.

Best solution is to install positive and negative buss bars and connect your 12 volt pairs of golf cart batteries to them. Then all of your other connections can be made to the bus bars. Blue Sea makes these.

+1

Ken E. said:

Best solution is to install positive and negative buss bars and connect your 12 volt pairs of golf cart batteries to them. Then all of your other connections can be made to the bus bars. Blue Sea makes these.

Click to expand...

^^^^ This.

Not only does it ensure that you are getting good conduction at your battery post, but it cleans up the wiring tremendously. While you are at it, I would make sure that you have a fuse on the positive cable from the battery to your new buss bar.

NAPA and others sell "military " battery connections.

These are about $5.00 each and square with 2 bolts thru each one.

They therefore can take 4 wires each with no problem, a terminal end under each bolt head or nut.

The good news is the wire terminal will touch the cast unit which passes the current with the least amount of resistance, especially compared to a steel or SS bolt with poor ampacity.

Images for military battery terminal




















More images for military battery terminal

To do the same I plan to use something like this



L

Lou_tribal said:

To do the same I plan to use something like this

L

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No offense, but a poor choice. The compression type lug doesn't adequately support the wire and provides only a single point of contact. If the connection ever loosens, the wire will be subject to arcing or shorting by coming apart. Minimal isolation between fused conductors. Far better to use a bus bar where a lug is crimped onto the wire and that is attached to the bus bar. Check to see if the pictured device meets ABYC standards, I think you'll find it does not. Go with Blue Sea hardware, far better.

Dave_E said:

Hi All,

I have 2 sets of 6V batteries in parallel (2 in each battery box). The PO had 5 positive leads off one battery in the 2nd battery set. Can you tap off the positive from the 1st box? That was a finding by the surveyor (too many leads on one post).

Dave

Click to expand...

Add some positive and negative distribution busbars close to the positive and negative battery bank take off points, as shown below.




Ideally there are only a few things that get connected directly to the batteries themselves;

#1 Other series or parallel batteries.
#2 Positive and Negative System Take Offs
#3 Battery Temp Sensors (negative post or side of case only)
#4 Voltage Sensing

Everything else, and unless you have LiFePO4 voltage sensing can be at the distribution busbars, should be connected to the positive or negative distribution buses. Keep these busbars as close to the bank as is possible and the positive lead should have over current protection within 7" of the positive terminal. For fusing off the distribution bus there are many options including MRBF fuses, fuse distribution blocks etc.

The Marinco Pro-Installer line are quite good and they come standard with a cover for positive distribution. Just choose how many 5/16" or 3/8" studs you need. Generally you may have an inverter/charger, DC panel, windlass, thruster, alternator, charger, solar, wind, bilge pumps, head, VHF, etc. etc. all connecting to the distribution buses.






Four 6V batteries for a 12V bank in a series / parallel configuration should ideally be wired as shown..



When you add positive & neg distribution busbars it would look more like this:

Post 10 shows the correct way to do things. Don’t over look the fact that all the wiring and terminal connections are symmetrical.

Lou_tribal said:

To do the same I plan to use something like this

L

Click to expand...

Oh No. Button head hex, even/especially stainless are a bad choice. Bolts and ring terms for vibrating things like boats.

Ditto...The post by CMS is the way to do it.

Duly noted, thank you to fix my insanity

L

Dave_E said:

Hi All,

I have 2 sets of 6V batteries in parallel (2 in each battery box). The PO had 5 positive leads off one battery in the 2nd battery set. Can you tap off the positive from the 1st box? That was a finding by the surveyor (too many leads on one post).

Dave

Click to expand...

How about this alternative?



http://www.boatsteer.com/battery.html

SiestaG said:

How about this alternative?

View attachment 71250

Boat Steering Solutions - Terminal Tamer

Click to expand...

Interesting. solves some problems.

But, Fail for me. Too much weight hanging off of a piece of lead.

And what, give every wire its own fuse, no way to quickly isolate the bank?

Depends how its wired.

Not every boat needs to be wired like a space craft.

As long as circuits are fused or protected with CBs....job done.

some people can still figure out how to isolate circuits if there is an issue.... pull hard, wire cutters, bolt cutters, machete, etc...

Boats need only be safe, no more complicated or adorned than the owner wants.

May not be pretty or fancy or expensive....but perfectly suitable as long as certain things are covered.

FF said:

NAPA and others sell "military " battery connections.
...
More images for military battery terminal

Click to expand...

Your links worked, but all the images show up as broken here.

I suspect due to those crazy long URLs.

john61ct said:

And what, give every wire its own fuse, no way to quickly isolate the bank?

Click to expand...

Good points.

On my sailboat when I redid my batteries I ended up with 4 x 6v golf cart batteries. I had limited space to work with. I used this terminal fuse block from Blue Seas to add two terminal fuse blocks to the positive terminal. The voltage sensor wire ended up on the battery terminal, then on one fuse block was a #1 cable to main 12 panel, and the other fuse block had one smaller cable from the alternator and another from the charger. This solved some space issues as well as providing appropriate fuse protection for the wiring.

It would have been a bit better to run one large cable from the battery to a positive buss bar, but this was what I could fit.

http://www.go2marine.com/docs/2/4/7/2/247249F-f.jpg

Yes those MRBF are great, also Class-T and ANL all good for high currents, and getting close as possible to the post is A Good Thing.

Only caveat for MRBF, be careful the base of the "other end" is well supported if very heavy gauge wire is required, and the wire itself so as not to bear down with too much weight.

If heavy leverage is applied in any direction on the "outside" end, it can put too much stress on the battery post or bolt area, maybe eventually causing wear or cracking.

tiltrider1 said:

Post 10 shows the correct way to do things. Don’t over look the fact that all the wiring and terminal connections are symmetrical.

Click to expand...

If you upgrade your wiring, the symmetry becomes less critical.

Ken E. said:

Ditto...The post by CMS is the way to do it.

Click to expand...

SiestaG said:

How about this alternative?

View attachment 71250

Boat Steering Solutions - Terminal Tamer

Click to expand...

If you use MRBF fuses and have lots of head room, that just might work. Many boats of my size lack the room above the batt bank to allow for that. I added an MRBF fuse to my start battery and had to bend it down to make room for the cover.

I have 6 golf cart batteries. Each pair runs a heavy cable to a high-current fusible link. So there are 3 of these fuses. Then the individual pairs are switched by 3 cutoff switches so each pair of two 6-volt batteries can be isolated, and finally two heavy copper buss bars provide a positive and negative buss. These are on the back wall of the electrical panel, the front of which pulls down (hinged) for access. All breakers feed off these two buss bars.

Two group 24 starting batteries have their own fusible link and cutoff switch, and there is a fifth switch that can connect the house bank to the starting bank.

Each fuse and switch adds resistance thus voltage drops that can add up quickly.

My preference is minimum necessary for safety, but at least be aware and measure for issues.

"have their own fusible link"

Do you carry on board replacements , should a problem arise?

Class T fuses are rated for most wire amperage used on boats , and replacements are easily stored and installed.

SiestaG said:

How about this alternative?

View attachment 71250

Boat Steering Solutions - Terminal Tamer

Click to expand...

ABYC states if you use an unsheathed wire, you must have current protection with in 7” inches. You also increase the risk of an accidental short from a dropped tool or part. While you have meet the letter of one rule you have made the situation much less safe.

tiltrider1 said:

You also increase the risk of an accidental short from a dropped tool or part.

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Very good point!

I do believe ABYC discusses connections inside a battery box.

CMS said:

Keep these busbars as close to the bank as is possible and the positive lead should have over current protection within 7" of the positive terminal.

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Ok. So therein lies the problem! According to Bluesea: “In any case, fuses, circuit breakers, and switches should not be installed in battery compartments because of the risk of corrosion coupled with the potential presence of explosive gasses.”

So...how do you realistically achieve this? On the stringer near the battery box?

My over current protections located near the positive bus bar, some distance from the battery box. Currently (pardon the pun) I am not in compliance.

Jim

JDCAVE said:

Ok. So therein lies the problem! According to Bluesea: “In any case, fuses, circuit breakers, and switches should not be installed in battery compartments because of the risk of corrosion coupled with the potential presence of explosive gasses.”

So...how do you realistically achieve this? On the stringer near the battery box?

My over current protections located near the positive bus bar, some distance from the battery box. Currently (pardon the pun) I am not in compliance.

Jim

Click to expand...

First you get 72” before you need over current protection. That’s plenty of distance to find a good location for a buss bar. At that point you can separate your starter path from your house path. If your circuit breakers are farther than 72” from the battery you can put in a large fuse to protect the house circuit wire. Starter circuit does not need to be fused.