Leisure batteries - care and upcoming developments
Chris Hogan, 24th August 2015, Boat
Leisure batteries are important for enjoyment of many boats and yachts, especially as it looks like autumn's come early this year, so lighting becomes more important. We offer tips for keeping your batteries in good condition and look at upcoming developments that will mean you can keep those lights on for longer.
At the moment most leisure batteries are of the lead-acid type used for cars, although they are significantly different. They need to provide a more constant, low level power supply rather than the occasional short, sharp burst of starting an engine and are therefore designed to withstand going to low levels of charge more often.
Having said that, we all know that fully discharging a lead-acid battery will shorten it's life considerably, so it's to be avoided if at all possible. If the battery has caps on the cells then check the levels every three months or so and top up with distilled water. Many batteries are now sealed for life so that's a chore a lot of us no longer have to worry about.
Keep the voltage high
If your boat doesn't have a battery monitor on-board it's well worth getting a multimeter as a simple voltage check will tell you roughly how much charge you have. Disconnect it before measuring though, and if you've just been charging it, allow about half an hour to pass before testing.
A fully charged sealed or flooded lead-acid battery will show 12.7V or more, a half charge around 12.2V. There are other types of lead-acid battery, such as valve-regulated lead-acid (VRLA) which comes in two forms – gel and absorbed glass mat (AGM) – and spiral wound.
Sealed batteries and AGM in particular have become popular with boat users because they're effectively spill-proof. The voltages at different charge levels will be slightly different for these, but not way out. Check with the manufacturer or retailer for exact figures.
If you look to prevent your battery going below 12.2V you should get the recommended three to five years out of it. Multimeters used to be very expensive but are now available for around £10 – a lot less than a replacement battery!
Alternator charging
If you're running on an engine and using an alternator to charge the battery, it might not fully charge it, particularly if it's a car one. Many boats have car alternators because they are cheap and plentiful but a marine alternator will provide more electrical power at low engine revs and at a higher rate (14V rather than 12V)
If you have a car alternator then you'll need to top up charge on shore or try adding a solar powered charger – see below.
Charging on shore
Depending on your type of boat and where you store it you may be able to plug in a charger, or connect to shore power if you have a charger built-in. If you have neither of these, then solar panel-based chargers are the way to go. These have revolutionised leisure battery care, particularly during winter lay-ups, and lugging batteries out to take them home and charge them should now be a thing of the past.
Solar powered chargers are now available for as little as £15, although more expensive ones will deliver more with lower light levels. Also look for a controller which will stop charging once the battery is charged or becomes fully depleted.
What's new?
It does look like the days of the lead-acid battery might be numbered though. Lithium batteries, of the kind used in laptops, cameras and other electronic devices are coming to the leisure battery market, although initially they were horribly expensive. The benefits are that they are lighter and longer-lived, with up to fifteen year lifespans now being talked about.
Lithium batteries are currently about three to four times the price of lead-acid, so the prices have a way to go before they'll make sense. The marine industry is very keen though, because of weight saving and more efficient charging cycles.
Lithium-based arrays of batteries are now going into larger vessels – see the link below for the power and monitoring systems that Energy Solutions put into the Port of London Authority's (PLA) new multi-purpose maintenance vessel, London Titan.
Safety and control
Another issue is that fires were caused in the early days of using lithium batteries in marine applications. The industry is working to bring the same level of safety precautions that the car industry uses for lithium batteries being used in electric and hybrid cars, so it might be a while yet before we see widespread use with smaller boats.
This means that control and monitoring systems need to be installed and probably different charging systems. Straight replacement lithium batteries are available but at the moment they are being marketed more heavily to lightweight motor vehicles like quadbikes, jet-skis and motorcycles rather than boats and yachts.
What's been your experience?
Have you had any experiences with leisure batteries, good or bad, that you'd like to share? Perhaps you've managed to keep a lead-acid battery going for way over the manufacturers quoted lifespan, or taken the plunge into lithium batteries already?
Or maybe you've not had the service from a solar panel that you'd expected? Drop us an email and we'll run a follow-up article if there's enough interest.
