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12 volt battery bank hookups

parrotguy

By parrotguy
in Boat Equipment

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parrotguy Engager

parrotguy

Posted
Posted

i have 4 -6volt batteries wired up parrel/Series, now what? Want to be able to use each battery as fairly as possible. I have to hook up an inverter,solar controller, windmill, 15hp yahmaha engine, and all the other stuff that runs a boat, like bilge pump, runnig lites, depth finder, vhf, question is what terminals for a good balance? And how do you treat or understand the 2 cross over batteries fron neg. To pos. What is thier title now. Have I confused you all as much as I am confused? Please take stab at it. How did some bloke from Florida get on this site? Wwell there was another web site that showed an answer from Simileypete and said that he could be found on this site. Now if this message gets out I will be happy cause I am doing it off a little cell phone with web servie which is lacking at times. Didnt mean for this to be this long. Sorry for that.

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springy Proficient

springy

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Posted (edited)

Ignore the pos->neg connection and plan as if you had two 12v batteries not 4 @ 6v, once youve decided on

the rest then your two pos-neg leads turn your "physical" 4 @ 6v into two @ 12v

 

Do you need bank isolation - do you have separate banks for engine & domestic ? or is that just not relevant

 

springy

Edited by springy
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PhilR Experienced

PhilR

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Posted

i have 4 -6volt batteries wired up parrel/Series, now what? Want to be able to use each battery as fairly as possible. I have to hook up an inverter,solar controller, windmill, 15hp yahmaha engine, and all the other stuff that runs a boat, like bilge pump, runnig lites, depth finder, vhf, question is what terminals for a good balance? And how do you treat or understand the 2 cross over batteries fron neg. To pos. What is thier title now. Have I confused you all as much as I am confused? Please take stab at it. How did some bloke from Florida get on this site? Wwell there was another web site that showed an answer from Simileypete and said that he could be found on this site. Now if this message gets out I will be happy cause I am doing it off a little cell phone with web servie which is lacking at times. Didnt mean for this to be this long. Sorry for that.

 

Is the engine a Yamaha outboard or a Yanmar inboard used for propulsion? ..... Or is it a Yanmar genset and you have a separate propulsion engine?

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parrotguy Engager

parrotguy

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thank guys. Now I am understanding a bit better. It is a lot easier balancing 2 batteries. And no I dont need isolation I dont think. And I use engine and house together since engine starts very easy and i keep it swiched to both batteries all the time.

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smileypete Veteran II

smileypete

Posted
Posted (edited)

First off, if you're wiring an boat, especially for offshore, there's no waaaay a few forum posts are likely to give you all the information you need to do a competent job.

 

It'd be by far the best to seek the advice and oversight of a local reputable marine electrical specialist as well. Even if you only pay for an hour or two of advice and do the work yourself, you're almost certain to save their fee and more by doing things the best way and avoiding expensive mistakes.

 

OK so having made that clear, the main considerations for connecting items are cable current ratings, maximum voltage drops, fuse ratings, and quality of connections.

 

For cable ratings the instructions for larger items like inverters and solar controllers should state what size to use, if not and for other items a good rule of thumb is take the max current draw in amps then divide by 3 to get the minimum size in mm2 csa (cross section area), then use the next available cable size up. So an inverter drawing 100A would need a minimum of 100/3 = 33mm2, in your case you'll have to use the next equivalent size up in AWG.

 

As far as voltage drops go, you need to work them out for each item and check they're kept to a reasonable minimum. A cable loaded at 3A per mm2 will drop 0.05V per metre length, so in the above case an inverter drawing 100A though 4m of 33mm2 cable will create a total drop of 4 x 0.05 = 0.2V at the inverter.

 

Don't forget to include both the cable length there and back between the batts and the item so an inverter 2m from batts will use 2m cable there and 2m back for a total of 4m.

 

For the minimum voltage drops to meet, on a 12V boat, a reasonable total minimum is 0.2V for charging circuits, 0.3V for critical navigation circuits, and up to 0.5V to 1.0V for non critical circuits. If the minimum cable size calculated for current draw doesn't give an acceptable voltage drop, the cable size will need to be increased pro-rata to bring the voltage drop down to the acceptable level.

 

For fuses, most larger items and some smaller ones will have instructions that state the required fuse size, otherwise reasonable rule of thumb is to use a fuse size which is no higher than the cables max calculated current rating of 3A per mm2, but no less than the current draw of the item.

 

All cables that go to the positive batt bank common should be fused with 6" of the batts, and of course fuse boards or fuses used where a larger positive cable feeds a number of smaller cables in turn going to individual items.

 

Finally when making connections that may be exposed to damp or salt air at any time, tinned stranded cable must be used along with decent quality and properly sized crimp terminals, and decent crimping tools like ratchet crimpers. For tubular type crimps ensure they're fully sealed with glue lined heatshrink too.

 

Best thing to do now is make a wiring diagram showing the batt bank and all the electrical items on the boat, together with cable sizes, cable distances, max current draw and calculated voltage drop, then take this to a marine electrical specialist and see what they advise.

 

There's a bit of an acquired art in choosing the best way things are connected for tidiness and high reliability while keeping cost to a minimum, and a marine electrical specialist can be a big help here.

 

Finally if the engine isn't an outboard that can be started by hand, best have a sufficiently sized well maintained and tested sealed battery with a safe means of connection, for an emergency backup. Also keep a repair kit with stuff like a spare fuses, meter, pliers, cutters, screwdrivers, cable, screw terminals for emergency repairs.

 

Now if I can sum up the most important part from this monologue it's "Plan as best you can then seek professional advice from a reputable marine electrical specialist" smile.png

 

ETA: Try forums like Cruisers Forum too, lots of knowledgeable US based people on there:

 

http://www.cruisersforum.com/

 

cheers, Pete.

~smpt~

Edited by smileypete
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parrotguy Engager

parrotguy

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thanks simleypete tried this earlier but phone got locked up ,quess reply was to big. Will shorten it. Over the years stuff has been done like you suggested. Now I am switching from three batt. To a small bank. I am thinking of hooking inverter pos. To pos. Of one batt. And neg. To other batt. And with two remaining post I am hooking controller poos. To pos. Of one and neg.to the other. Remaing wires from cicuit breaker, mostly small stuff, spiltting them up equaly between post..idea is this a pretty decent balance forr all batt. Concerned?

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bottle Veteran II

bottle

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Posted (edited)

Parrotguy

 

I may be misunderstanding on how you are going to wire your battery bank and the connections for take off's

 

Apologies if I am but....

 

When you have made all the interconnects to make the batteries into a bank, then treat that bank as one big battery.

 

Make all the positive connections to the battery at one end and all the negative connections to the battery at the other end.

 

If you have not been here: http://www.smartgauge.co.uk/batt_con.html it will give you all the reasons for doing so. (lots of other info on that site)

 

Edit: If there are to many connections, you may need to fit bus bars.

Edited by bottle
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blodger Rising Star

blodger

Posted
Posted

ok looking at 4 bank batt. Again i still wonder why I cant use ethier post of pos. Or neg. Each one should have the same volts and amps.

It is good practice to take the power off battery banks from diametrically opposite positive and negatives of the battery bank; It better balances the discharge and charging of the batteries stopping one from doing more work basically.

If that was what you were asking?

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GUMPY Veteran II

GUMPYDonate to Canal World

Posted
Posted

as long as I wire the 2 pos and 2 neg together I have the big batt with a total of 4 post available

not quite.

The loads would have to be balanced externally.

If you put all the heavy loads on one side then one battery will take most of the load leading to that battery failing first.

 

You need to take the +ve to an isolation switch so in reality you only have one +ve terminal......

As it says on the SG site take the feeds from opposite sides.

you will then need a -ve bus bar to do the -ve distribution and a +ve bus bar after the isolation switch to do the +ve distribution.

 

Did I mention a fuse in the main +ve feed!

 

Although people think its only 12v its easy to fit it isn't easy to do it properly unless you know what you are doing.

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bottle Veteran II

bottle

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Posted (edited)

parrotguy

 

Forget supply to boat, just wire the batteries up with the interconnects.

 

because you have 4X6v and want 12v it is a little more involved.

 

Take two 6v batteries and connect positive on one to the negative on the other, you now have a 12v battery

 

Take the other two batteries and do the same, you now have another 12v battery.

 

Take the two '12v batteries' and connect the unconnected positive on one to the unconnected positive on the other.

 

The same with the negatives take the unconnected negative on one to the unconnected negative on the other.

 

You now have a 12v battery bank.

 

Your take off's will now be where you made the last connections, positive on one of the 12v batteries and negative on the other 12v battery.

 

Someone may be able to put up a diagram to make it clear, or try drawing it out on paper.

 

Edit: to use the batteries in a balanced way you only have two (one positive and one negative) terminals to use.

Edited by bottle
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Nickhlx Veteran

Nickhlx

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Posted

To Parrotguy ...

 

The reason why you have to take all connections from ONE point is that even heavy inter-connects have a significant resistance in practice. This will cause a small voltage drop under heavy current conditions and cause one battery string to work harder than the other and cause its demise sooner / deteriorate performance overall. Yes we are talking millivolts, which a meter may not be able to resolve, but it will make a difference. Naturally everything tapers off to "being worthwhile" but if you aim to set it up correctly, it will be at least as in the right ballpark and trending towards as good as can be...

 

The Battery connections sheet on Gibbo's Smartgauge site is excellent, and should/does explain all points in full detail..

 

Nick

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  • 3 weeks later...
bowten Rising Star

bowten

Posted
Posted

parrotguy

 

Forget supply to boat, just wire the batteries up with the interconnects.

 

because you have 4X6v and want 12v it is a little more involved.

 

Take two 6v batteries and connect positive on one to the negative on the other, you now have a 12v battery

 

Take the other two batteries and do the same, you now have another 12v battery.

 

Take the two '12v batteries' and connect the unconnected positive on one to the unconnected positive on the other.

 

The same with the negatives take the unconnected negative on one to the unconnected negative on the other.

 

You now have a 12v battery bank.

 

Your take off's will now be where you made the last connections, positive on one of the 12v batteries and negative on the other 12v battery.

 

Someone may be able to put up a diagram to make it clear, or try drawing it out on paper.

 

Edit: to use the batteries in a balanced way you only have two (one positive and one negative) terminals to use.

I have found this while searching.I could do with a diagram if possible,anybody able to do this.Cheers.

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  • 11 months later...

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