Interconnecting (5) Multiple batteries

[Sapphal]

I am in the process of cleaning up my battery terminals and the general compartment.  I have 1 starter and 5 leisure batteries.  The leisure batteries are presently connected together as Method 2 on the smartgauge site http://www.smartgauge.co.uk/batt_con.html.

Would it be of considerable worth to rewire the batteries to equalise the resistance using method 3?  Downside is that it will require 2 studs and 10 cables all the same length.

Method 4 (thanks to smileypete) may be better.  Trouble is I can't work out how to connect 5 batteries and get each one to have the same overall length of cable.  I'm sure it's not too difficult - just can't get my head round it.

Any help appreciated.

[WotEver]

27 minutes ago, Sapphal said:

Would it be of considerable worth to rewire the batteries to equalise the resistance using method 3?

No. 

‘Considerable’ being a subjective word of course.  

It’s possible that you’d be able to measure the difference albeit unlikely. If you’re in the habit of taking a huge current from the batteries then the difference might be more measurable but still not considerable. 

Edited February 19, 2018 by WotEver
Typo

[Robbo]

No, just use thick cables.

[smileypete]

Yeah method 2 and thick cables.

Edited February 19, 2018 by smileypete

[Ssscrudddy]

Why did the OP say thanks smileypete re method 4? This makes me think he came up with it, in which case why is he now saying method 2 is ok?

Basically I have the same question for 5 leisure batteries (plus 1 separate starter battery). My boat originally came with 5 leisure batteries, 1 of which was clearly a lot newer than the rest. In short time 1 of the batteries failed, a bit later the rest started dropping out. They was wired as per method 1.
We replaced all with 3 batteries, which have now reached the end of their life, & want to go back to 5.

Method 3 seems ideal but I'm not sure I have the room, so I would also like to know how to do 5 via method 4.

Edited February 20, 2018 by Ssscrudddy

[Asia_Off_Grid]

2 hours ago, Ssscrudddy said:

Why did the OP say thanks smileypete re method 4?

Because, if you visit the page linked above, and then scroll down to "Method 4", you will see that David Small composed the following:

[WotEver]

2 hours ago, Ssscrudddy said:

Why did the OP say thanks smileypete re method 4? This makes me think he came up with it, in which case why is he now saying method 2 is ok?

For the same reason that I and everyone else has said #2 is ok, namely that you’d be extremely unlikely to see any difference. #4 might be ‘perfect’ but if you use nice fat cables you’ll never see any difference between 2 & 4. 

2 hours ago, Ssscrudddy said:

I would also like to know how to do 5 via method 4.

You can’t. 

4 minutes ago, Asia_Off_Grid said:

you will see that David Small composed the following

Who?

[Asia_Off_Grid]

3 minutes ago, WotEver said:

Who?

David Small. I posted that same article, after having gained written permission from him (David Small) to do so, through the Smart Gauge Website. This was just shy of 5 years ago. 

[WotEver]

But he’s just a Merlin employee. He neither wrote the SmartGauge website nor owns copyright to it. 

[Asia_Off_Grid]

28 minutes ago, WotEver said:

But he’s just a Merlin employee. He neither wrote the SmartGauge website nor owns copyright to it. 

Well, he's the person whom I contacted, when asking for permission to post the article on another forum. He must have some authority, due to being the contact person on the contact page of the site.

 

Edited February 20, 2018 by Asia_Off_Grid
Correction.

[WotEver]

23 minutes ago, Asia_Off_Grid said:

Well, he's the person whom I contacted, when asking for permission to post the article on another forum. He must have some authority, due to having given me specific permission to post it.

Yeah, Gibbo (the author) won’t mind anyone quoting from it. 

[Detling]

What size interconnects are you using? if you use 95mm^2 welding cable any voltage drop at normal less than 30 amp loads, is negligible, a big inverter at 200 amp may drop a few milliVolts across the bank but you would only use that for a few minutes I hope.

[plainsman]

I have 70mm cables on five domestic batteries (12345) I have the in/out diagonally opposite but one battery in if that makes sense. That is the pos in/out is on battery No2 and the neg in/out on battery No 4. I think I picked up this configuration on the forum some time ago so I am not claiming credit.

[Ssscrudddy]

Thanks for the replies. Completely forgot I even posted!

[Ssscrudddy]

Now I'm curious, with plainsman's set up, with the in/out on battery 2 & 4 (5 batteries) vs the in/out on battery 1 & 5.

I don't know enough to do any calculations, but I counted the interconnects. 

Plainsman's comes out as 4,2,2,2,4.

Whereas the other way is 4,4,4,4,4.

So basically which of those two would be better?

& how thick is an adequately thick cable please?

[WotEver]

7 minutes ago, Ssscrudddy said:

Plainsman's comes out as 4,2,2,2,4.

Whereas the other way is 4,4,4,4,4.

So basically which of those two would be better?

You already know, don’t you?  Which one looks more balanced? (Hint, it ain’t Plainsman’s). 

9 minutes ago, Ssscrudddy said:

how thick is an adequately thick cable please

The thicker the better. 70mm² is good. 90mm² is better. 

[Ssscrudddy]

Ta

[plainsman]

On 2/21/2018 at 22:45, WotEver said:

You already know, don’t you?  Which one looks more balanced? (Hint, it ain’t Plainsman’s). 

The thicker the better. 70mm² is good. 90mm² is better. 

Need some help here, this is my layout, I assume it's obvious and down to me being slow but don't know where 42224 comes in or 44444 in 'the other method' (whichever that is). Is this better or worse than  Smartgauge method 2 (POs in/out at batt 1 and Neg in/out at at batt 5)?  As I said I got this from some other source as being an improvement on Smartgauge method 2.  Help appreciated

                                                                                                    

[WotEver]

20 minutes ago, plainsman said:

don't know where 42224 comes in or 44444

Count the links from each battery to the main connections, adding up the negative path & the positive path. Batteries 1 & 5 have 4 links, Batteries 2, 3 & 4 have two links. This means that the bank isn’t balanced; Batteries 2, 3, 4 will be loaded fractionally more heavily than 1 & 5.  

20 minutes ago, plainsman said:

Is this better or worse than  Smartgauge method 2

Worse. But it’s not something I’d lose any sleep over. 

Edited February 24, 2018 by WotEver
Got me numbers wrong

[smileypete]

On 2/20/2018 at 11:28, Ssscrudddy said:

Why did the OP say thanks smileypete re method 4? This makes me think he came up with it, in which case why is he now saying method 2 is ok?

Basically I have the same question for 5 leisure batteries (plus 1 separate starter battery). My boat originally came with 5 leisure batteries, 1 of which was clearly a lot newer than the rest. In short time 1 of the batteries failed, a bit later the rest started dropping out. They was wired as per method 1.
We replaced all with 3 batteries, which have now reached the end of their life, & want to go back to 5.

Method 3 seems ideal but I'm not sure I have the room, so I would also like to know how to do 5 via method 4.

As long as the batt wiring is half decent, it will play an exceedingly minor role if any in the typical battery death problems.

As for cable size, I'd not go above 25mm2 (minimum for BSS) unless planning to have an inverter from 1kW up, then go with what the inverter needs. If anyone has some real world evidence to show otherwise then I'm all ears.  (Of course if the inverter is way away from the batts then you'd need to take account of that.)

Edited February 24, 2018 by smileypete

[Ssscrudddy]

It's got a 2kw inverter, I was going to get the 95mm squared wire until you said that. The existing connectors are 12mm diameter & I lost 2 & 1 fell apart.

Now I'm confused again, because the others said 70 good 90 better.

Edited February 24, 2018 by Ssscrudddy

[smileypete]

37 minutes ago, Ssscrudddy said:

It's got a 2kw inverter, I was going to get the 95mm squared wire until you said that. The existing connectors are 12mm diameter & I lost 2 & 1 fell apart.

Now I'm confused again, because the others said 70 good 90 better.

Assuming you're 12V, a 2kW inverter pulling up to about 200A will need at least 70mm2, based on 'amps divided by three', so 95mm2 isn't far off.

The instructions might give a specific size, some use dual terminals and the instructions mention twinned cables for supply, eg 2x35mm2 for both positive and negative, easier to route the cables I s'pose.

[MtB]

Provided your interconnects are fat enough, it doesn't matter a toss in real life what pattern you use to connect up the batteries. 

[Ssscrudddy]

Thanks again then peeps. 95mm2 it is then, after all I only have to do it once.

& before anyone is bothered about how much electrickery I'm going to try & use at once, definitely not that much. Microwave & washing machine only with the engine running (or on shore power), no hair dryers or anything else here. Dehumidifier just no, not even with the engine running, that thing wants about 70amps at 12V, so hell no, shore power only!

[WotEver]

4 minutes ago, Ssscrudddy said:

after all I only have to do it once.

Exactly so