Batteries on Boats

photo by: Joanna Poe

Last weekend, we attended a lecture at the Cruising Association on ‘Power Systems on Boats’, by Matt Boney. 

We’ve attended a lecture on electrics on boats there before, but it’s always good to hear more on this topic again. Confirms that this is definitely something we need to master. Loads of studying ahead for the Can Opener…

Here are the key highlights from the notes I required the Can Opener take down (Hey Furrball, I’m self-motivated! I do not need you camped on my shoulder, waggling my ears like horse reigns to make me write faster…):

Battery Capacity

• Most cruisers do not have enough
• 150amps/day is a small amount
• You probably need a minimum of 300amp hours at 50% of DoD (depth of discharge)
• and batteries only top up to 80% of their capacity
• so you need to actually have more like 420 amp hours to be able to use 300 amp hours/day… and still would have to charge every day
• AND you don’t want to run your battery to 0… only want to run it down to about 25% of battery capacity
• therefore you need even more capacity!

Which battery to use?

• You can mix battery sizes to increase capacity (lifeline tested this) as long as batteries are
• the same age and
• the same make

• With batteries you ‘get what you pay for’… quality costs..

 Types of batteries

• Sealed leisure or marine batteries 
• are ‘maintenance-free’, 
• but can’t be topped up so they won’t last long. 
• They are also affected by temperature.
• Gels 
• are useful, 
• slow discharge
• old technology
• expensive
• hard to find

• AGMs
• are the best (?)
• becoming more popular
• make sure you get the right AGM for the right purpose! (There are many potential uses for these…)

Monitoring your batteries
You should 

• charge your batteries to 100% every month to anti-sulfate them – otherwise they will become permanently sulfated
• should estimate when you hit 50% DoD by measuring battery voltage
• must have a panel mounted digital volt meter
• must have a small digital multi-meter
• all batteries must have multi-stage regulators
• test your batteries 2x/year
• use your alarms!
• monitor regularly!

Ways to generate electricity?

• shore power charger
• solar – recommended 600Watts+ or you won’t be able to replace daily usage
• wind or towing generators – expensive, but easy and convenient
• AC or DC diesel generator – DC is the quieter of the two
• Honda petrol generator – don’t get this one. There are no petrol stations at sea. And you are not really saving a lot on size.

What type of batteries are you using? What kind of generator(s) are you using? Are you getting the voltage you need out of them?

–Captain Cat 

 (transcribed by the Can Opener)

Corrosion & Metal Fatigue On Boats

Hold the oysters! 

We’ve just been to a blue water seminar this past weekend at the Cruising Association – and it was awesome. 7 lectures on how to cruise that were of riveting and relevant interest. Couldn’t get more near and dear to our heart than that.

Vyv Cox, a mechanical engineer who has written quite a few articles for Yachting World, etc*, led off with a talk on ‘mid-ocean things that could spoil your day’. 

Well, yes. And most of them involved metal fatigue and corrosion. The kind of thing that causes masts to come down and boats to sink. Sure made for some edge of the seat listening. 

But good news – although you cannot eliminate all risk and there are no guarantees, you can take steps to minimise the chances of quite a few scary situations. 

Most of them involve sealants, choosing the right materials and check, check, checking your equipment. Good stuff.

Here’s what we learned…

Corrosion

Galvanic corrosion

• 2 metals in salt water generate electricity… and causes one of the metals to corrode preferentially
• common example: stainless steel and aluminum
• antidote: 
• isolate different metals
• avoid using different metals close together if possible
• exclude water – use sealants to protect eg. Duralac paste, tefgel
  

Crevice corrosion

• if water covers the top of a crevice – then air is excluded and corrosion can occur
• thread roots are crevices – eg lower swaged ends of shrouds are suspectible
• so keep water out – fill it with sealant, lanolin, Waxoyl
• Waxoyl is available in an aerosol – warm up the shrouds with a hot air gun, then spray the Waxoyl on
  

General corrosion

• is materials related
• is unlikely with 300 series stainless steels
• carbon steel is suspectible but generally not used except in engines, engine components, mountings, chain etc
• NOTE: Jeanneau only uses 400 series which is not very anti-corrosive
  

Seacocks & Fittings

How to avoid corrosion… choose your materials well

• EU regulations only require fittings to be good for 5 years (Huh? Yep, the wrong seacocks can sink your boat…)
• brass suffers from dezincification – the loss of zinc from brass
• the fitting will show the pinkish colour of copper on it
• it may only affect the surface but severly reduces strength
• thread roots are particularly susceptible
• if the fittings are chrome-plated – then they are brass

Where to find these short-life brass skin fittings?

• Tonval, Guidi products – all brass
• Manganese bronze… is brass (and some other metals mixed in) – often found in propellers
• Naval brass = brass

Who uses brass skin fittings?

• Beneteau
• Dufour
• Hallberg-Rassy
• Malo
• Maxi
• Najad
• X Yachts
• …

Yeah. Surprised us too.

So what materials should your seacocks and skin fittings be made of?

If you discover you do have brass fittings, then it’s time to replace them with the good stuff… And yes, it costs a lot.

• DZR is the good stuff – it includes arsenic which slows corrosion (cZ132Cu62Zn35.2Sn0.7Pb2As0.1)
• NOTE: no DZR is chrome-plated 
• The symbol ‘CR’ (corrosion resistant) means it is DZR – but only if you see this symbol on valves!!
• Mysteriously Guidi’s brand symbol on skin fittings looks a lot like ‘CR’… but Guidi = brass. Be careful!
• ASAP brand made with DZR
• Blakes seacocks also made with DZR (at least for the last 25 years)
• Bronze – very good… and expensive

What else should you do to protect your boat from corrosion?

For mountings on hull use:

• Sikaflex 291
• 3M 5400
• Pu40
• Boatlife Lifecaulk

For threads use:

• Liquid PTFE
• Sikaflex 291
• PTFE tape

re: Bonding

• If you have bronze or DZR you don’t need to seal because your fittings will not corrode.
• (If you do bond, then you will create a galvanic situation.)
• Bonding is done in North America, not in the EU/UK.

re: Anodes

• Be careful where you place your anodes – they work only on ‘line of sight’. If you place them on the other side of an obstacle (say, a hull…) then they won’t work and can even make matters worse.

Fatigue

• Fractures occur due to cyclic stress.
• eg shrouds and stays, fittings, masts, shafts
• eg if you let off the back stay every time you are at the dock, then you incresae fatigue in mast which could lead to failure (hmmm, the boat we train on does this…)
• Therefore eliminate stress raisers and allow freedom of movement. 
• (So, does this mean never put the backstay on? Or leave it on all the time?…)
• Failure of bolts are always due to not being tightened enough, which allows play, leading to fatigue and failure.
• Make sure that swaged fittings are in line (no ‘banana’ swags or cracks) and that toggles are on all ends.
• Inspect all of the mast and mast fittings for cracks
• Low profile T-ball fittings are best.

Have you ever been caught on the wrong side of corrosion? What did you find the last time you inspected your mast?

We will certainly be going over Un Tigre Beau‘s mast with a giant magnifying glass this winter I can tell you…

–Captain Cat 

 (transcribed by the Can Opener)

* coxengineering.sharepoint.com

Don Casey’s Sailboat Maintenance Manual – Arrived!

links below at bottom of post

I just got Don Casey’s Complete Illustrated Sailboat Maintenance Manual in the mail to add to the library. ‘Six books in one’ is anyone’s idea of good value. 

I’ve assigned it to my First mate by day for some light reading (ha!). He needs to cover this giant reference book cover to cover. In particular, I want him to focus on its overview of how to survey boats. The book weighs in at about 3 lbs, so it’ll take him a while.

By night, however, the book is mine! A few good snoozes stretched over this tome should allow all the info contained therein to leech upwards into my sizable and osmotically inclined brain. I’ll be done absorbing its info long before the Can Opener. 

Then I can move on to selecting the right shade of organic catnip slip covers for the berths in the saloon. 

A captain’s work is never done.

 

–Captain Cat

(transcribed by the Can Opener)

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The Plan to Refit the Boat

 

Part 5 of Captain Cat’s Invincible Plan to Get Cruising:

What will need to be done to prepare the boat for blue water sailing? Since we are planning to buy a previously owned boat, chances are – just about everything…

Assuming we decide to buy (or co-purchase) a boat, then the Can Opener will need to get straight to work on preparing the boat for blue water travel. I am allowing for a year of dedicated refit within my Invincible Plan to Get Cruising.

Depending on the needs of the boat, he may need far more (or less?) time, but based on an unscientific survey of others’ experiences, this seems like a conservative estimate to plan around.

If we wind up volunteering as crew on someone else’s boat, it may need to have a refit too, in which case he will gain excellent training and experience. It’s all good.

1. Make a list from bow to stern of what needs to be done – 
• refer to marine survey/ discuss with surveyor from purchase
• emergency preparedness system – life raft, GPS etc
• research others’ refit lists and compare 
• review advice of long term cruising ‘pros’
2. Research solutions for needs above: 
• Internet 
• Club members/friends 
• Forums for owners of similar designs
3. Research prices
• special offers eg at boat shows 
• second hand solutions
• when to buy new
4. Purchase materials
5. Learn to install
6. Install
7. Test and review performance
8. Set up records to track ongoing performance

Any other key refit steps to add?

   

–Captain Cat

(transcribed by the Can Opener) 

N.B. Part 6 of Captain Cat’s Invincible Plan to Get Cruising is: The Plan to Blast Off.