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S&S Swan General - Battery management system
14 February 2016 - 19:10
Join Date: 17 March 2010
Posts: 48

Battery management system
HI Forum,

Does anybody happen to know which battery management system is a good one. On my boat I increaesd the service battery set to 5 pieces of EXIDE GEL batteries of 85Ah each. The starter battery is some Optima AGM battery, don't remeber the details. I think around 100 Ah.

I require to buy new service batteries this winter, and I wonder whether I should install a battery management system. We have the habit to spend more nights on anchor than in marinas, so an exact overview over the remaining amount of power on board would be a good thing to have.

Any thoughts or suggestions? Many thanks!

Best regards

CHINOOK, 431/003

16 February 2016 - 10:11
Join Date: 06 January 2012
Posts: 66

Hi, You've obviously made a very good choice acquiring a 431 ;)

I've got experience from 3 battery monitoring systems during the Years:
- Nasa Battery manager: the cheapest possible but not accurate. I had it in my previous boat. Also some friends of mine have the same experience of the poor accuracy.
- Victron BMV: accurate one, a bit dum looking...
- Votronic: LCD Battery Computer S + LCD Solar Computer S. Accurate. My favorite, blends quite well with the original electrical panel, see the pic. They replaced those original Nautor analog current meters at the upper corners.

My charge system consist of:
- 230VAC Victron 120A/14VDC Charger with 3...6kW sine inverter. (*1)
- 230VAC / 2kW generator Honda EU 20i (*2)
- Engine alternator 90A with "clever" Sterling charge controller
- Votronic MPPT Duo Solar controller with upper mentioned Solar Computer and some 200W solar panels.
- Batteries are 400AH Trojan deep cycle lead acid ones + 100AH for the engine

My best regards,

CAID 431-12

(*1) The inverter can synchronize with the shore power and this is needed to start the air conditioner as 17A at 230 VAC needed to start the Dometic Vector Turbo Marine Air Cond.

(*2) The Honda generator is optimized with the Victron Charger = limiting the input AC current at the generator input of the Victron Charger automatically to the same as the Honda produces at max cont. power (7,5A / 230VAC) --> we can get about max. 80...100A charging current to the batteries.

16 February 2016 - 19:38
Join Date: 17 March 2010
Posts: 48


Many thanks for your comments! Very helpful. It seems that CAID has a good, solid electric system on board.

Yes, it was a good choice back in 1995 when I bought CHINOOK. I have had the boat for a bit more than 20 years now, and I am still in love. And CHINOOK is in perfectly good shape as well. I would not exchange it with any of the modern boats! New mast, boom, furling and rig, new engine, new teak deck, third generation of winches, polished ss hatches, all deck gear new, mast collar now stainless steel, re-painted hull and deck, electric anchor windlass installed. Main sheet system lead aft to the helmsman, and 2 additional winches on the coaming back there now (actually I moved the mainsheet winches to there).

Altogether most of the technical equipment renewed, the last remaining step is my wind instrument system (still the old B&G Hengist etc. stuff in place). But all the refitted and replaced stuff is in original looks and appearance.

The only thing which is a bit off - but I admit I stand behind the concept - is that we installed a mordern fold-down sprayhood, which protects us quite nicely - and the original little cap thing now lives in my cellar. That new, bigger thing is constantly down in good weather, but we put it up during rainy and windy days, and this makes life a bit more comfortable for us oldish crew. I am 62 now.

Thanks again,

CHINOK, 431-003

17 February 2016 - 09:26
Join Date: 06 January 2012
Posts: 66

Hello Christian, it's very delighting to hear that You've enjoyed Your fine Yacht already for decades and kept it in pristine condition!

I'm a bit interested in Your sprayhood configuration. Could You send me some pics of Your solution? (please use this address: ns431 at

All my best regards,


17 February 2016 - 10:41
Join Date: 17 March 2010
Posts: 48


I am just sending you a number of pictures. 8.9 MB, altogether. In case you don't receive them (mailbox limitation or so), just let me know.

I could post the photos here, in a new thread maybe, in case this is of interest to the forum. Anybody interested, out there?



17 February 2016 - 10:45
Join Date: 17 March 2010
Posts: 48

18 February 2016 - 11:10
Join Date: 02 February 2007
Posts: 202

Interesting subject indeed!
On our Swan 41 (size is important) we have 4 110Ah lead calcium closed cells batteries, 3 of them are service batteries, one for engine and windlass. The service batteries are now in their 11th year, and the engine one in its 8th year.
Battery management system is from Mastervolt: 90 Amps alternator, "smart" multistage regulator, and battery monitor for the service battery bank, plus a Megapulse "battery refresher" on this same bank.
Everything seems to work really well, but starting to be worried about their age I bought a battery tester, for a "health check".
The problem I have is that apparently it only checks the CCA (cold cranking amperes) of the batteries.
On all my batteries I am measuring something around 400A (while a new battery of the same size is supposed to be around 700A), and it says "battery OK" .
So my question is: is there any relationship between CCA and capacity of a battery?
When should batteries be changed?
Sorry if this is to technical a question.
Perhaps our master professor could help?
Many thanks and profitable maintenance season to all.
Philippe. 41/022

18 February 2016 - 11:52
Join Date: 17 March 2010
Posts: 48

Thanks philippeV, interesting post!

Actually, none of my maintenance seasons was profitable, so far! :-((

How do you manage that to be the case? :-))

18 February 2016 - 12:07
Join Date: 17 March 2010
Posts: 48

Regarding your post, philippeV: I do not have a battery tester. My 5 pieces of EXIDE GEL batteries seemed to completely die within 2 hours, last autumn. At an age of 6 + 1/2 years.

I actually left the marina, and everything seemed OK. After one hour, under sail, the autopilot shut off, due to low voltage (it did not really shut off, still the old NECO system, but it stopped to work).

I looked at the service battery voltage, below 10V. I started the engine, nearly zero Amp charging current. I motored back to the marina, stopped the engine, voltage back to 11.8V, but down to below 10V after 10 minutes. Land charger on, charging current nearly zero Amp. Batteries completely dead.

So it took only one hour, from batteries alive to batteries dead, as it seems. I was not impressed with the 6 + 1/2 years of battery life, but people told me this is kind of normal. -> ?

CHINOOK, 431/003

18 February 2016 - 13:34
Join Date: 23 October 2011
Posts: 150

Dear Christian,
I agree that this reply post is OT, too.

I like very much your big sprayhood. I wonder if you have a more detailed picture. Is there an additional rail build on a new cross beam forward?
My boat is a 47. Has any other owner a sprayhood at the main hatch larger than the standard?
Thanks for the input

Matteo 45, Grampus 47/016

18 February 2016 - 13:53
Join Date: 17 March 2010
Posts: 48

Hi Matteo 45, yes I do have more photos. I will upload them to a new thread tonight, which I will start here. Then people can find it if interested.

CHINOOK, 431/003

18 February 2016 - 15:54
Join Date: 02 January 2008
Posts: 1547

Dear Philippe
If you calibrate your battery monitor now and then, telling it when the batteries are fully charged, it should display the remaining capacity.
Eleven years is a long time, it is likely you did not discharge the batteries too deep too often. Replacement is due when charging becomes necessary too soon.
There is no direct correlation between CCA and capacity. Suggest you take a look here
Kind regards

19 February 2016 - 18:44
Join Date: 01 March 2007
Posts: 147

Dear Matteo, In answer to your question to 47 owners, we have created a larger sprayhood for the cockpit on Sarabande. The job involved fabricating a coving to receive the hoops for the hood, replacing the main track and introducing drains to the mid deck area. I wanted to create a drier cockpit!
I have more pictures if you would like to see them.
Kind regards
Sarabande 47/029

22 February 2016 - 17:00
Join Date: 02 February 2007
Posts: 202

May I suggest that such different (and interesting) subjects be addressed in different posts. My best guess is that, in the future, nobody will ever be able to find information on cockpit protection in a battery management post!
Kind regards to all Swan Fans!
Philippe 41/022

22 February 2016 - 21:40
Join Date: 31 January 2007
Posts: 30

Probably a bit late in responding to your post, but I fitted an Adverc battery management system and 3 x 105 AGM Deep cycle batteries in 2012. The batteries are still behaving very well. I fitted a Link 10 battery monitor when I bought the boat in 2004 which gives volts, amps and ampere hours consumed and it is magic! The Adverc battery management and regulator enables me to charge to batteries considerably faster than before. The Adverc system electronically fools the alternators into thinking that they need to output more current. I have two alternators, a pessimist!

Ant Fawcett Wotan Swan 411-40

28 February 2016 - 16:22
Join Date: 17 March 2010
Posts: 48

Many thanks to all of you for your thoughts and recommendations. I learnt a lot, presently I am looking at the Votronic and at the Mastervolt systems. The Mastervolt probably has higher level software, but the advantage of the Votronic clearly is that it fits into the switch panel nicely, and also it looks good. IHe confirmed it is working OK, so that might become my choice.

Your posts also got me into re-considering the type of batteries again that I require to buy, remember my service batteries require replacing. Originally I was a fan of lead acid batteries, and did not see the big advantages of all the modern battery types. OK, somebody persuaded me, and my recent set was Exide GEL type. I admit the closed batteries are kind of nice to have, but their lifetime was not so impressive. 8 seasons. Not bad, but the lead acid ones I had before lasted more than 11 years.

IHe put my attention to the Trojan deep cycle batteries, which seem like an affordable and professional option. Definetly attractive seems that I would be able to fit 5 pieces of 130 AH capacity into the same space as I now use with 5x 85AH Exide GEL. Wow, what a huge power bank! Fyi: I installed an additional battery compartment under the owners bed, so I can store 5 batteries of this size.

Any rcommendations? 5x Exide GEL ES950 85 Ah, or 5x Trojan 31XHS 12V 130Ah deep cycle??

CHINOOK 431/003

29 February 2016 - 08:27
Join Date: 02 February 2007
Posts: 202

Hello all.
If you change your battery type, be VERY careful to adapt the charging voltage to your new battery type. I have a good friend who bought expensive gel batteries and killed them in a few month just because he charged them with too high a voltage in keeping the same voltage as for his former lead acid batteries.(if I remember well 14,3V)
All the best and happy sailing.
Philippe 41/022

29 February 2016 - 11:26
Join Date: 02 February 2007
Posts: 202

Hello dear Swan Fans.
I am back on the subject of trying to determine when to change batteries, this after reading the articles suggested by our dear professor (
I have wondered if there was not another way (than measuring the CCA) of checking batteries using our "battery monitors". These give the amount of Ampères Hours consumed but not the remaining capacity, but also the current voltage.
Knowing the discharge curve (i.e. volts / % amp hours consumed) would not it be possible to evaluate the actual capacity of a battery??
As the battery gets older, the voltage drops more for the same output.
The problem: I cannot get hold of a standard curve for a lead acid battery?
Does this exist?
Would this idea give sufficient information knowing that discharge curves appear to be rather flat??
Sorry again if this is too technical but waiting for the batteries to fail is NOT my solution!!
Many thanks for your help.
KInd regards.
Philippe 41/022

29 February 2016 - 18:07
Join Date: 17 March 2010
Posts: 48

Hi philppeV,

Yes, you are right, the charger requires to be adapted. I have a Sterling one and a Leab one. I always say I am neither an optimist nor a pessimist, I am a realist ...


Both have dip switches for this.

Regarding the death of batteries, I can only agree. But I do not know how to avoid this scenario. This time it was not so bad, they just stopped life, and I had to keep the engine on until I was moord in a marina again. Last time it was more critical. I had lead acid batteries then. And one of them started cooking on the charger. We were ashore for a coffe, and when we came back we had to take the cooking battery out AT ONCE, as we were nervous the whole boat might burn down. It took hours until the thing cooled down again!

CHINOOK 431/003

29 February 2016 - 18:12
Join Date: 17 March 2010
Posts: 48

... See my post above - is maybe this the aspect which should get me to buy Exide GEL batteries again? The cooking sulphuric acid below the floorboards I remember as quite a frightening experience ...

29 February 2016 - 18:32
Join Date: 02 January 2008
Posts: 1547

Dear Philippe
Pls note there are also battery monitors displaying remaining capacity.
Kind regards

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