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Old 13-10-2015, 03:22   #1
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Question: Batteries in Parallel, all loads from main + & -

Not sure how best to put this...

I have 4 group 31 batteries wired together in parallel. The positive of battery #1 is the main positive and the negative of number 4 is the main ground.

All major charging and loads are connected to the main positive, but my question is; can I connect light loads like a bilge pump etc. anywhere along the line, maybe to battery #2 in the system..???

Or, should ALL positive connections be to the positive of Number one? The main reason is I have a ton of cables going to just one terminal and I want to spread out some of the connections because the leads are too short or it takes too much cable to split it the 4-5 feet between the + & - terminals...

Hope that makes sense & I really appreciate any help!
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Old 13-10-2015, 03:49   #2
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Re: Question: Batteries in Parallel, all loads from main + & -

A more usual arrangement would be to use bus bars for both +ve and -ve loads.
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Old 13-10-2015, 04:26   #3
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Re: Question: Batteries in Parallel, all loads from main + & -

Don't take feeds from different batteries.

Here's a very good article. SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

It answers your specific question:
"Finally, if your battery bank has various take off points on different batteries, change it now! It is extremely bad practice. Not only does it mess up the battery balancing, it also makes trouble shooting very much more complicated and looks awful. "

And also discusses various methods of connecting four parallel batteries.

You are implementing Method 2, it's not the worst way to do it, but it's not the best either. Implement Method 4 if you can - combined with Wotname's recommended bus bars.
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Old 13-10-2015, 04:41   #4
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Re: Question: Batteries in Parallel, all loads from main + & -

Thanks!

Here is my set up back when we were installing it. It has a box built around it now and straps to hold everything down.

Starting from the left are the 4 house batteries and the last batt. on the right is a separate start battery that shares the ground with the house bank.

You can see my + & - terminals are pretty loaded up...On the positive terminal, the yellow cable is the windlass, the fused red is the alt. and the main red runs through the 1/2/off switch to the fusebox.

The yellow arrow is the positive for the bilge pump on battery 2.



So, it would be better to run both a positive and negative bus bar and run all the leads off there?

Something like these & just mount them to the wall of the bilge...?



Thanks for your help this is new to me.
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Old 13-10-2015, 04:52   #5
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Re: Question: Batteries in Parallel, all loads from main + & -

I don't see a fuse in that positive conductor, you might want to think about that.
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Old 13-10-2015, 04:56   #6
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Re: Question: Batteries in Parallel, all loads from main + & -

Run a pos and negative bus, just like you picture, just remember bigger is better.
Mount it to a wall is fine, a current limiting device on the Pos side isn't a bad idea either.
If you can get a little airspace between each battery that helps cooling during charging
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Old 13-10-2015, 08:37   #7
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Re: Question: Batteries in Parallel, all loads from main + & -

The positive should run to a DC distribution panel (possibly through a selector switch if you have 2 banks). That way you can select what's on or not. If you have a panel, and just didn't mention it, then the bar bus is the way to go. This would be for the circuits you want ON all the time, like bilge pumps and maybe VHF radio. Everything else should be on the panel.
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Old 13-10-2015, 10:06   #8
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Re: Question: Batteries in Parallel, all loads from main + & -

Definitely put a current limiting device on every house bank take-off.


A battery terminal fuse is an effective and inexpensive solution. However, a breaker is better in that if it ever trips, AFTER you solve the problem, you only need to reset the breaker rather than find and replace the fuse. Either should be sized to suit the rating of the cable running to, or the distribution panel, whichever is less.


Every additional connection on any one terminal increases risk of a bad connection. ABYC standards prohibit having more than 4 connections on any battery terminal. I generally recommend no more than 2.


I am not aware of any ABYC standard prohibiting take-offs from other than the "end" battery terminal in a bank.


I don't see a bilge pump or VHF on a mid bank battery having a huge impact on charge balancing, but as others have said, using a bus bar or power post for all take-offs is a cleaner solution which makes battery servicing (pulling caps off for checking/filling and removal/replacement) much easier.


Many people are injured every year from improper battery handling. Just because it can't electrocute you, doesn't mean it can't hurt you.


Whenever working around batteries, always follow good safety practices, (remove all jewellery, wear protective clothing and googles, disconnect all charge sources and loads, and operate blower before disconnecting battery terminals, take care not to short terminals, etc.)


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Old 13-10-2015, 10:40   #9
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Re: Question: Batteries in Parallel, all loads from main + & -

Quote:
Originally Posted by ramblinrod View Post
Definitely put a current limiting device on every house bank take-off.


A battery terminal fuse is an effective and inexpensive solution. However, a breaker is better in that if it ever trips, AFTER you solve the problem, you only need to reset the breaker rather than find and replace the fuse. Either should be sized to suit the rating of the cable running to, or the distribution panel, whichever is less.


Breakers can be handy but any breaker used as primary bank protection should meet the minimum ABYC AIC rating for the bank it is protecting.

For a bank such as the one pictured this requires minimum AIC rating of 5000A... While the Blue Sea 187 series breakers do meet 5000A AIC at 12V they only go to 200A, which can get marginal if the house bank could ever be called upon to start the motor.

If the bank size exceeds 500Ah or 2200 CCA I don't know of a marine duty circuit breaker that would meet the ABYC standard. Over 500Ah and you're usually into a 20,000 AIC Class T fuse...
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Old 13-10-2015, 11:34   #10
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Re: Question: Batteries in Parallel, all loads from main + & -

The paralleling cables appear to be at least twice as long as necessary, have no shrink sleeve to seal the connections, and appear to be improperly crimped. Did you do these yourself?
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Old 13-10-2015, 11:43   #11
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Re: Question: Batteries in Parallel, all loads from main + & -

It also appears that the right two or three batteries are right next to your exhaust riser. Heat is not good for batteries. Do you have somewhere else to put them on the boat?
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Old 13-10-2015, 11:58   #12
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Re: Question: Batteries in Parallel, all loads from main + & -

Quote:
Originally Posted by Mr Big View Post
Not sure how best to put this...

I have 4 group 31 batteries wired together in parallel. The positive of battery #1 is the main positive and the negative of number 4 is the main ground.

All major charging and loads are connected to the main positive, but my question is; can I connect light loads like a bilge pump etc. anywhere along the line, maybe to battery #2 in the system..???

Or, should ALL positive connections be to the positive of Number one? The main reason is I have a ton of cables going to just one terminal and I want to spread out some of the connections because the leads are too short or it takes too much cable to split it the 4-5 feet between the + & - terminals...

Hope that makes sense & I really appreciate any help!
Fit a bus bar. Size the posts and therefore the terminals for each load.

As a rule I never fit more than 2 eye terminals together. We have some exceptions where space for a bigger bus bar is an issue.

Some of our bus bars impede on access to other systems. These might have 3 or more terminals together. Only light loads that arent mission or safety critical are ganged together.

Fault finding and resistance checking is easier if you group terminals logically. For example bilge pump power is alone while several light terminals can be ganged together.

I dont place any terminals, other than the main power feed direct to the battery. This way when you remove or replace the battery you're not flexing and squashing wires and connectors. Battery access for topups and hydrometer testing is generally easier. Less excuse not to check them then.

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Old 13-10-2015, 12:16   #13
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Re: Question: Batteries in Parallel, all loads from main + & -

Someone who knows more than me, like MainSail, should comment -- but I think the batteries will charge and discharge more equally if the positive and negative feeds are at opposite ends of the bank. Or you could move just the alternator positive to the opposite end to get some benefit and reduce the number of connections.

BlueSea makes a nifty multiple connection battery fuse holder:

https://www.bluesea.com/products/215...k_-_30_to_300A
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Old 13-10-2015, 12:32   #14
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Re: Question: Batteries in Parallel, all loads from main + & -

To answer your exact question, no. It wont make any difference. Everything connected to that parallel "node" sees the same voltage. Current will flow determined by resistive loads, not placement. Making the bus bars is the same theory and easier to work with but you asked Can I and yes you can.
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Old 13-10-2015, 12:48   #15
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Re: Question: Batteries in Parallel, all loads from main + & -

Click image for larger version

Name:	Bat. Bank <a title=Wiring & Switching.jpg Views: 161 Size: 421.3 KB ID: 110924" style="margin: 2px" />

A suggested method.
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