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Chris Pink

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http://www.victronenergy.com/orderbook/

 

It's been posted a couple of times in various topics but, having just read it, I think it deserves a topic of its own.

 

The first authorative and realistic exposition of batteries, power use and generation for boats in the modern world I've come across.

 

realistic in that some of its models assume batteries will be charged to 80% and discharged to 30% (unlike some of the more theoretical treatises and manufacturers figures). Although some of his high end models may not apply to your average ditch crawling tub.

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Just browsed through document.

 

The comments about high rates of discharge from a battery reducing its effective capacity is well documented of course.

 

What I found interesting though was the claim that lost capacity in such circumstances will recover (to a degree) if the battery is left without load for a number of hours. This makes sense, as the chemical state within the plates will have a chance to equalise between surface & inner.

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http://www.victronenergy.com/orderbook/

 

It's been posted a couple of times in various topics but, having just read it, I think it deserves a topic of its own.

 

The first authorative and realistic exposition of batteries, power use and generation for boats in the modern world I've come across.

 

realistic in that some of its models assume batteries will be charged to 80% and discharged to 30% (unlike some of the more theoretical treatises and manufacturers figures). Although some of his high end models may not apply to your average ditch crawling tub.

Good link, thanks for posting.

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Glad you like it ;)

The author is a boater and part of Victron so he knows the product and the uses for it.

 

Interestingly he suggests that though paralleling batteries will get better use of power from underspun alternators, charge finishing may be best done with more respect for the chemistry of the cells and esp the plates.

Edited by Arthur Brown
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Yes, I noticed that, especially in light of discussions on here about the Peukert effect and battery bank size

 

I notice also perhaps, an acknowledgement of the growth in use of multiple banks with their own battery chargers. .

Don't quite understand what you mean about growth in use of multiple banks. As far as I am aware it has been done for years i.e. start battery/house bank/bow thruster?

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This book introduces the idea of a 4th for navigation equipment so actively considers different chargers for different banks rather than simply connecting them. It seems an interesting concept to me.

Sorry,yes I understand what you mean now. A bloke who once moored by us used separate banks with separate chargers. Can't remember exactly but I think he ran the inverter off one bank, and the 12V fridge/12V house electrics off a different bank, whilst charging separately. He reckoned it worked better for him than paralleling all of the house bank (in this case there was no shore power and he used a Honda genny with chargers.)

 

And one of the main arguments for bigger banks rather than distributed banks has always been the Peukert effect which this postulates is a temporary thing.

This is the idea that batteries "recover to some extent" after a rest? Makes sense to me; starter batteries certainly do this when engines are being difficult to start?

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Important reasons for using several banks and chargers are the different charge needs of the cells best suited for each purpose.

 

Engine starter batteries need to supply huge current but usually only for seconds, while house batteries need to supply medium current for long periods. These often have different chemistries and need slightly different charge rates and significantly different terminal voltages. Paralleling may get the best out of slow running alternators but each should be adjusted for the lead length and chemistry of their intended battery and the finishing charge should be put in by a correctly set alternator to achieve good cell life.

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I see that the Victron document says "Batteries are considered to have reached the end of their service life when the capacity they can hold has reduced to

80% of the rated capacity"

 

That is particularly interesting compared to the statement I was recently told by a battery supplier that any brand-new battery whose capacity is 70% of the rated capacity or more is regarded by his company as being perfectly OK in respect to its guarantee.

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I see that the Victron document says "Batteries are considered to have reached the end of their service life when the capacity they can hold has reduced to

80% of the rated capacity"

 

That is particularly interesting compared to the statement I was recently told by a battery supplier that any brand-new battery whose capacity is 70% of the rated capacity or more is regarded by his company as being perfectly OK in respect to its guarantee.

Slight disagreement there then? :)

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In the last year I think I have read just about every battery related document on the internet...I am really trying hard to understand battery charging! The Victron document is certainly one of the best, it feels like it is based on real first-hand knowledge.

 

The notion that Peukert is a short term effect is interesting and quite plausible; some energy will be lost as heat but mostly it is probably a surface discharge effect? I wonder what the recovery time is after returning to a lower drain current? and I wonder what Gibbo would say? maybe this thread is a plot to resurrect him!

 

Also very interesting is the table in section 4.5 This says that a semi-traction battery needs an absoption charge time of 7 hours (or more)

So with 2 or 3 hours of bulk charge thats 10 hours charge time...so a liveaboard without mains is going to find it very very hard to get a 100% charge. This is certainly my experience. Many chargers and alternator controllers (such as the Sterling) will go into float mode after no more than 3 hours (open lead acid mode). I am starting to suspect that almost all chargers try so hard to avoid water loss that they significantly undercharge batteries.

 

any thoughts from the battery experts????

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The important thing to realise is that people buy sealed batteries for ease and convenience then have to charge them carefully to preserve cell life. This usually means undercharging them because cycling 50% capacity from 80 - 30% is quickly and easily replaced by without much of an absorption charge and there is no loss of cell water if you don't get the cell to full.

 

IMO a mains free live aboard needs solar and wind-power to keep the cells topped off to full unless they are doing 6+ engine hours a day and these need a good controller to ensure that the cells are not simply cooked to dryness. The price of the house battery stack and the engine starter batteries means that a little thought put into well designed charging systems is a very valuable idea. I'm guessing that few boats live off less than £1K of batteries, yet they begrudge getting the charging right.

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  • 2 weeks later...

Charles Sterling once had an interesting document on his website (now removed unfortunately) the essence of which was the only batteries worth buying are wet lead acid that you can top up, which are the cheapest batteries. These days engine start batteries are little or no different from so-called leisure batteries, because modern vehicle batteries are still running equipment when the car is parked. I am sure I remember Gibbo some years ago writing that he had taken apart some modern "leisure" batteries, and that there was no discernible difference in plate thickness to modern starter batteries.

 

So £1k for batteries sounds like an unnecessary amount to spend. It appears that the price difference between ordinary start batteries (non-sealed) and "leisure" batteries is the use of the word, "leisure."

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So £1k for batteries sounds like an unnecessary amount to spend. It appears that the price difference between ordinary start batteries (non-sealed) and "leisure" batteries is the use of the word, "leisure."

 

That's why it's worth putting money into at least traction batteries, unless you hardly use your batteries (like been on shore power majority of the time and/or run your engine daily for a good amount of time).

Edited by Robbo
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That's why it's worth putting money into at least traction batteries, unless you hardly use your batteries (like been on shore power majority of the time and/or run your engine daily for a good amount of time).

I agree with that. My last boat had 6v lead acid traction batteries and they had a long life span.

 

Nevertheless, I think too many boat owners today expect their battery system to deliver them unlimited power as though they were in a house and part of the National Grid, instead of adapting their consumption to living off the grid, restricting television use, discarding microwaves (a useless object if ever there was one) and, in short, changing lifestyle instead of expecting a modern house on a boat.

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Nevertheless, I think too many boat owners today expect their battery system to deliver them unlimited power as though they were in a house and part of the National Grid, instead of adapting their consumption to living off the grid, restricting television use, discarding microwaves (a useless object if ever there was one) and, in short, changing lifestyle instead of expecting a modern house on a boat.

 

A well designed battery and charging system should be able to handle the most power hungry of users so i don't believe you have to cut down on tv usage or do without gadgets and the like. Leisure batteries and a 100amp alternator won't cut it though.

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A well designed battery and charging system should be able to handle the most power hungry of users so i don't believe you have to cut down on tv usage or do without gadgets and the like. Leisure batteries and a 100amp alternator won't cut it though.

You may think so. In 30 years of boating I've never come across any narrowboat that can achieve that without having to run engines and generators for hours on end.

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You may think so. In 30 years of boating I've never come across any narrowboat that can achieve that without having to run engines and generators for hours on end.

 

Yep, a built in diesel genny is a must if your power hungry IMHO. Treat the genny as the source of power and the batteries as a buffer. I think most people see batteries as a source.

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