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Leisure battery connecting


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2 minutes ago, WotEver said:

Note that repeating others’ assertions that ‘fat’ interconnects solve the problem is to ignore the fact that Gibbo refers to the resistance of the connections, not the fat cables on their own. 

 

Agreed but it is still the total resistance of everything. I agree on a theoretical level with what he says but once we got all the interlinks the same & sufficient size and the take off at opposite ends of the bank experience suggest that banks of three or four batteries connected like that can and do wok well enough for the majority of people. Naturally they wont if you neglect keeping your battery connections clean and tight. Once we get to more than four batteries then though I have no long term experience I am sure both busbars and you way of wiring will reduce the effects of voltdrop across the bank so enhancing the charging to a degree. I am not talking about unbalanced charging, just the interlinks etc causing voltdrop that must degrade charging.

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7 minutes ago, Tony Brooks said:

... once we got all the interlinks the same & sufficient size and the take off at opposite ends of the bank experience suggest that banks of three or four batteries connected like that can and do wok well enough for the majority of people. Naturally they wont if you neglect keeping your battery connections clean and tight. Once we get to more than four batteries then though I have no long term experience I am sure both busbars and you way of wiring will reduce the effects of voltdrop across the bank so enhancing the charging to a degree. I am not talking about unbalanced charging, just the interlinks etc causing voltdrop that must degrade charging.

Yes indeed. And Gibbo says as much on that page. 

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19 minutes ago, system 4-50 said:

Is this a 3 battery system that has been extended to a 5 batt system?  Just curious.

Looks that way, doesn’t it? And solar added at the same time or thereafter. 

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48 minutes ago, WotEver said:

Note that repeating others’ assertions that ‘fat’ interconnects solve the problem

 

I have to say, I'm still not sure what the problem is that Gibbo solves with his prescriptive diagrams of interconnect configurations.

 

 

 

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5 minutes ago, Mike the Boilerman said:

I have to say, I'm still not sure what the problem is that Gibbo solves with his prescriptive diagrams of interconnect configurations.

Unbalanced batteries. 

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1 minute ago, Mike the Boilerman said:

 

And given nice fat low resistance interconnects result in tiny degrees of 'unbalance', why does that matter?

There’s absolutely no point in me repeating what Gibbo wrote very clearly over 10 years ago except perhaps to snip just a single quote:

I have to be honest now and say that when I first did this calculation in about 1990 I completely refused to believe the results. The results seemed so exaggerated. So much so that I wired up a battery bank and did the experiment for real, taking real measurements. The calculations were indeed correct.

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1 minute ago, WotEver said:

There’s absolutely no point in me repeating what Gibbo wrote very clearly over 10 years ago except perhaps to snip just a single quote:

I have to be honest now and say that when I first did this calculation in about 1990 I completely refused to believe the results. The results seemed so exaggerated. So much so that I wired up a battery bank and did the experiment for real, taking real measurements. The calculations were indeed correct.

 

This is getting very circular. You say this matters because Gibbo says it matters....

 

 

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I do not have the wherewithal, experience, equipment, nor the inclination to attempt to replicate his experiments and so, having no reason to disbelieve him, I accept his calculations. 

 

If you refute his assertions then why not back up that refutation with some evidence?

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4 minutes ago, WotEver said:

If you refute his assertions then why not back up that refutation with some evidence?

 

Don't be silly. 

 

I'm suggesting (get it? A suggestion, not a refutation) that in real life these battery imbalances are trivial and don't matter. They pale into insignificance on a real boat on a real boat.

 

Now you are making rather silly demands for calculations and proof of my opinions. Thats,all they are, opinions based on real life experiences of boats and boating. Why ARE you so desperately defensive of anything Gibbo says? 

 

 

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I probably sit halfway between Mike & Gibbo. I know from experience that Gibbo is correct all the time but gets more correct each time you add a battery to a bank. The more batteries the more important unequal and total volt drops across the bank become. I also agree with Gibbo that taking both feeds from the same end of the bank, even on small banks, is not the best idea. I agree with Mike that experience tells me that once you get the feeds on opposite ends of smaller banks (say 3 or 4 batteries) any improvement in volt drops by altering the wiring method is very marginal. In fact Gibbo all but states this.

 

If only boat fitters and DIY people would read and understand what Gibbo said I am sure we would have fewer batte problems.

 

 

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16 minutes ago, Tony Brooks said:

experience tells me that once you get the feeds on opposite ends of smaller banks (say 3 or 4 batteries) any improvement in volt drops by altering the wiring method is very marginal. In fact Gibbo all but states this.

Actually he DOES state this. His words:

There really is no excuse whatsoever (apart from, perhaps, incompetence or laziness) for using the first example given at the top of this page.

The other three methods achieve much better balancing with the final two achieving perfect balancing between all four batteries.

 

Whether or not ‘perfection’ is required depends on your own OCD quotient. His calculations demonstrate that (with 4 batteries, it gets worse with more) Method 2 isn’t perfect but the imbalance is marginal. 

25 minutes ago, Mike the Boilerman said:

Why ARE you so desperately defensive of anything Gibbo says? 

I’m defensive of anything factual. If you want to start a thread suggesting that Apollo 11 never landed on the moon then I’ll be equally as defensive. 

 

 

Edited by WotEver
Added a missing worm
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26 minutes ago, Mike the Boilerman said:

I'm suggesting (get it? A suggestion, not a refutation) that in real life these battery imbalances are trivial and don't matter.

Then are you suggesting that Gibbo’s calculations and measurements are incorrect, or that he’s lying?

 

If you’re suggesting that the difference between methods 2 & 3 for four batteries are pretty trivial then I’d agree, as does Gibbo. 

3 minutes ago, Paul C said:

What do newly-built narrowboats with a domestic battery bank of 3 or 4 batteries come with?

I’d expect them to come with all connections on diagonally opposite corners. What they actually come with depends entirely on the bloke that connects them up. 

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48 minutes ago, WotEver said:

. What they actually come with depends entirely on the bloke that connects them up. 

Ok no worries, I'll leave it to others who might have a new(er) boat with unaltered wiring to post. It would be interesting to see if the "problem" of poor battery balancing is ignored by boatbuilders, or whether they're taking it into account when wiring up.

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4 hours ago, WotEver said:

Gibbo certainly knows his stuff and is one of the world’s leading experts on LA battery use and abuse. As with any other expert though, you are completely free to ignore his advice. 

 

He supplies some figures prior to ‘example 2’ on the battery interconnects page but once again, you’re completely at liberty to ignore them, or indeed disprove them if you have alternative calculations. 

 

Note that repeating others’ assertions that ‘fat’ interconnects solve the problem is to ignore the fact that Gibbo refers to the resistance of the connections, not the fat cables on their own. 

If all the fat cables are the same crossectonal area the the resistance ratios are the same regardless of how fat they are 

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2 hours ago, Paul C said:

Ok no worries, I'll leave it to others who might have a new(er) boat with unaltered wiring to post. It would be interesting to see if the "problem" of poor battery balancing is ignored by boatbuilders, or whether they're taking it into account when wiring up.

That will prove nothing because first of all far too many boat builders do what suits them or costs least and secondly as we often say batteries are consumables so a boater with sub-optimal battery connections is unlikely to know if a short battery life is down to their poor practices or poor wiring.

 

As far as I am concerned Gibbo's stance is correct BUT it is debatable how cost effective it is to do any more than put the feed cables at opposite ends of the bank. I think that is where any disagreement is and even Gibbo admits that any gains by more complimented wiring are far less that the change from "all on one end" to "everything at opposite ends". For clarity - I am talking about banks of up to four batteries, after that the balance should still be OK but each extra battery increases the voltdrop in the connections so doing something more complicated may well give better early stage charging.

 

 

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Thanks to everyone for commenting on my odd battery connections, I feel I know my boat a lot better after going through this exercise.

 

I couldn't see any good reason to have the starter battery in the middle of the leisure and it's good to see no-one can think of one either so I'll look at the implications of moving it. At least I can then move the inverter -ve feed to the end of the bank without adding any cable. I also can't see why two batteries are rotated 180 degrees to the rest, as you say Tony, just confusing.

 

As to the value of the calculations in the article, they make sense to me as someone who did a three year electronic engineering apprenticeship (a very long time ago but I believe the electrons still move the same way) and with a 100amp load the imbalance is startling. Of course most of us aren't pulling 100a most of the time but I di when I'm microwaving a ready meal and that's enough to make want to balance the load better. Thanks again for helping my thought process.

 

 

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1 hour ago, Mike the Boilerman said:

 

 

 

He appears to know his stuff but those of us who know less are in no position to judge and confirm his expertise. In any given subject, even those who only a little more than oneself, appear expert.

 

I'm not saying Gibbo is wrong, but I  AM saying I suspect the differences in battery performance between different interconnect configurations is negligible in practice, provided the interconnects are fat, and I have yet to read anything by Gibbo that convinces me otherwise. He 'talks a good book', but people here seem to swallow everything he says unquestioningly.

 

I agree. When i was working as a critical power project manager I oversaw the installation many, many, battery systems over the years, from 24 volt to 400 volt, in telephone exchanges and data centres.

 

They were always connected with the take-offs at either end (as per the first diagram in post #3).

 

Whilst there are theoretical benefits from equalizing the resistance of each connecting lead, in practice it doesnt matter PROVIDING the connections are of sufficient cross sectional area.

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2 hours ago, WotEver said:

Exactly. 

please bear in mind that the fatness of the cables is only one (relatively small) part of the equation...............  to guote Gibbo:

 

Typically the batteries are linked together with 35mm cable in a good installation (often much smaller in a poor installation). 35mm copper cable has a resistance of around 0.0006 Ohms per metre so the 20cm length between each battery will have a resistance of 0.00012 Ohms. This, admittedly, is close to nothing. But add onto this the 0.0002 Ohms for each connection interface (i.e. cable to crimp, crimp to battery post etc) and we find that the resistance between each battery post is around 0.0015 Ohms.

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Just now, Murflynn said:

please bear in mind that the fatness of the cables is only one (relatively small) part of the equation...............  to guote Gibbo:

 

Typically the batteries are linked together with 35mm cable in a good installation (often much smaller in a poor installation). 35mm copper cable has a resistance of around 0.0006 Ohms per metre so the 20cm length between each battery will have a resistance of 0.00012 Ohms. This, admittedly, is close to nothing. But add onto this the 0.0002 Ohms for each connection interface (i.e. cable to crimp, crimp to battery post etc) and we find that the resistance between each battery post is around 0.0015 Ohms.

Yes exactly. If that wasn’t the case why would connecting the diagonal corners be any different to connecting at one end? MtB suggests that connecting at one end instead “is trivial and doesn’t matter” which we all know to be nonsense. 

 

Going the the extra mile for ‘perfection’ is probably irrelevant for most (all?) of us as Gibbo more or less states himself. 

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