Battery Charging Questions...

[colemj]

Originally Posted by Kettlewell

I can't claim any expertise on this subject of battery wiring, but I would appreciate Andina and GoBoating commenting on what SmartGauge writes about this. Here's what happens when you tap one end of 4 batteries in parallel, according to SmartGauge:

A prolonged 100A load is not a reasonable assumption of usage for most of us.

Occasional short term 100A loads, even if it resulted in the data provided, would not make a difference in the battery discharge or lifespan.

For the normal 3-20A loads most of us see, there may be temporary differences in battery currents of an amp or so. Again, nothing to be concerned about.

Mark

[Kettlewell]

My own personal non-scientific observations were that three three identical 12-volt GP31 batteries in parallel performed better when I switched the cabling to run from opposite ends of the bank instead of from one end of the bank. What prompted this was noticing that the battery at one end of the bank with the leads was losing water at a faster rate than the other two batteries, and I observed more bubbling action in that battery shortly after a vigorous charging session. After switching the cables the loss of water stopped in that first battery.

[goboatingnow]

Originally Posted by Kettlewell

My own personal non-scientific observations were that three three identical 12-volt GP31 batteries in parallel performed better when I switched the cabling to run from opposite ends of the bank instead of from one end of the bank. What prompted this was noticing that the battery at one end of the bank with the leads was losing water at a faster rate than the other two batteries, and I observed more bubbling action in that battery shortly after a vigorous charging session. After switching the cables the loss of water stopped in that first battery.

Yes that could be the case , where the inter battery connections had issues. if one battery was bubbling , then actually all batteries should be bubbling, your solution solved the problem by adding resistance thats all.

Dave

[colemj]

Battery water usage rates are also intrinsic to individual batteries. For example, the battery farthest from our cabling uses more than the rest, followed by the middle. The one connected to the leads uses the least - go figure. The previous set of batteries used water middle-closest-furthest.

All of them start gassing at the same time, though.

Mark

[sailinglegend]

Originally Posted by colemj

A prolonged 100A load is not a reasonable assumption of usage for most of us.............

But a 100 amp charging current IS reasonable for many of us.

A trickle charger should not be used on a cruising boat to recharge deep cycle batteries.

Any Cruising boat should have about 400 Ah of service bank capacity for any sensible "at anchor" cruising lifestyle. That needs a 100 amp multi-stage shorepower or alternator charger for best charging practice - (25% of capacity).

Wiring the charging circuits, and loads, from opposite ends makes a lot of sense, even if it makes the smallest bit of difference in prolonging the battery bank life it has to be worth it - instead of arguing about it.

When - not if - the connecting cable between batteries corrode and the resistance increases then a "balanced" system is a much better engineering solution.

I think many posters don't understand what good engineering means.

[goboatingnow]

Wiring the charging circuits, and loads, from opposite ends makes a lot of sense, even if it makes the smallest bit of difference in prolonging the battery bank life it has to be worth it - instead of arguing about it.

When - not if - the connecting cable between batteries corrode and the resistance increases then a "balanced" system is a much better engineering solution.

I think many posters don't understand what good engineering means.

I think you are confusing 'practice' with science.

ANy examination of node currents using Kirchoffs laws, a 101 action for engineering students in this case with a simple therein equivalent voltage source and simple models of interconnection resistance will show how this DC network works.

It will further back up the point that for a large part of the charge cycle, including the last 20-30% such wiring topologies have no real effect on a typical boat battery bank of maybe 3-6 batteries. Many of these topology 'practices' came from large backup banks etc, that are then just parrotted to different uses . ( Just like the nonsense that AGM is a better battery in a boat- hah).

AGain wiring from top to bottom is a 'good' practice, but equally if you wire it any other way , the difference is minor and will have no real effect , certainly no affect on battery life .

IN very high current draw situations then such good practice has a small advantage , but only a small one and in real life likely drawfed by poor interconnection and other wiring issues on boats. Electrical 'systems' are just exactly that , systems.

Dave

[goboatingnow]

Wiring the charging circuits, and loads, from opposite ends makes a lot of sense, even if it makes the smallest bit of difference in prolonging the battery bank life it has to be worth it - instead of arguing about it.

Could you give us the science 'sense' behind it so, please

Dave

[sailinglegend]

Originally Posted by goboatingnow

.....your solution solved the problem by adding resistance thats all.

It equalized the resistance - which is the whole point of the argument!

[goboatingnow]

Originally Posted by sailinglegend

It equalized the resistance - which is the whole point of the argument!

well yes and no, the fact is the orginal point Andina made and I agree with is that the change in resistance is too small in comparison to other factors to make any real difference.

Dave

[Andina Marie]

Originally Posted by Kettlewell

I can't claim any expertise on this subject of battery wiring, but I would appreciate Andina and GoBoating commenting on what SmartGauge writes about this. Here's what happens when you tap one end of 4 batteries in parallel, according to SmartGauge:

Just because it is on the Internet it doesn't mean its true unless you are a French Model and can say bonjour.

If you look back we were talking about a trickle charger, not a 100 amp charger.

I pointed out that for starting currents of hundreds of amps the situation is different. If you are able to balance the loads it could "equalize" the discharge patterns so all batteries age at the same rate and all die more or less at the same time.

But in the real world, some batteries are new, some are old, some are different size, some need water, etc. Balancing to microvolts on the connections between them becomes ludicrous in comparison. Yes the tougher batteries will carry more load than the weaker ones but within a fraction of a second after starting the motor, battery to battery current will even out the charge level imbalance due to wiring and each will have contributed in proportion to its capacity.

Even with a 100 amp charging source the suggestion that the closest battery in a ladder connection structure would be gassing while the others are still charging is also ludicrous. The gassing voltage is not a precise threshold. It slowly increases once the batteries get over about 14.2 volts. The difference in gassing between 14.2 and 14.25 volts will be insignificant compared to the other battery parameters stated above.

I get the impression that engineers writing the quoted articles have never had to maintain a boat in real life. Perhaps for the first year the batteries appear identical (but they aren't). But you don't replace the whole bank when one dies, and from then on they will be matched even less. Theory is OK on the internet. Some of us have practical boats.

Bonjour.

[goboatingnow]

I get the impression that engineers writing the quoted articles have never had to maintain a boat in real life. Perhaps for the first year the batteries appear identical (but they aren't). But you don't replace the whole bank when one dies, and from then on they will be matched even less.

No the problem is that I suspect there are very few electronics engineers, here at all, becuase if so we'd see a scientific attempt to justify the their ( its) ascertain and to contradict yours. ( or even mine).

Its a simple kirchoffs node problem, using a few resistances and a simple resistive thevenin equivalence of a imperfect voltage source.

Even smartgauge do no such thing ( always be skeptical when people tell you, 'its too complex to explain' and just present conclusions , white mans magic as my dad used to say ) .

dave

[Teknav]

...Electrical Engineer, here...but not getting involved in this discussion. Get a gasoline powered generator to charge your batteries; problems solved. Mauritz

[colemj]

Originally Posted by Teknav

...Electrical Engineer, here...but not getting involved in this discussion. Get a gasoline powered generator to charge your batteries; problems solved. Mauritz

OK, so talk down to this non-electrical engineer - how does a gasoline powered generator supplying power to a charging source change the equation? What if it was propane powered? And why is it different than diesel powered, or solar or alternator?

Mark

[Teknav]

Hi! A gasoline powered generator is an independent/backup source, with a small footprint and with a very high sustainable reliability; can last 3-5 years of service, if well maintained. All others sources mentioned, can produce the power needed. It is the reliability factor that is in the heart of this issue. Mauritz

[colemj]

I think I will need to reread the thread, but I don't think anyone has been discussing reliability of charging sources. The OP asked about connecting a trickle charger, and others have been debating the merits of where the power cables should be connected on a multiple battery bank.

BTW, our diesel genset has lasted far more than 5 years and our solar and alternators have been going strong for 15yrs now (did lose one alternator and solar controller in a lightning strike).

Mark