Marine battery bank

How To Keep Your Yacht Battery From Dying Over the Winter

Depending on whether you plan to keep your battery in your yacht or you want to take it out for the winter, maintaining a proper voltage will ever remain the secret to a long-term battery sustainability for optimal performance.

Marine battery bankEnsuring that your battery is fully charged by maintaining full voltage will greatly impact its lifespan and performance. The short answer to this question is to keep the batteries charge from dropping too low whilst also trying to avoid overcharging.

Some yachts, especially the older ones may contain small parasitic draws of current which can affect any battery by fully discharging it if left for a long period of time. Therefore, it is advisable that you remove your batteries from the yacht and store them in a cool environment to keep its charge, avoid overcharging and also keep it ready for use when the season comes up.

Having a plan to maintain the charge of the battery in the winter is most beneficial to battery health and should be a part of any yacht owners winter ritual. While just disconnecting the battery may not be enough from keeping the battery from dropping to too low a voltage if the yacht will be stowed for any length of time. Fully-charging your battery, disconnecting it and keeping it on quality maintenance is the best way to avoid the charge from dropping as you also avoid overcharging.

A Word On Marine Batteries

The three types of marine battery recommended are Flooded, Gel and Absorbed Glass Mat (AGM). Most boats under around 50ft in length operate on a 12V system and are rated in ampere hours (the amount of energy charge in a battery that will allow one ampere of current to flow for one hour) and the number of cycle charges the battery will withstand in its lifetime.

Depending on the type of boat, use and budget will greatly effect which type of batteries you have.

Flooded Batteries – A sulphuric acid reservoir acts as an electrolytic pathway between the lead plates and results in essentially, a lead acid battery. As a by-product of the process, hydrogen and oxygen are given off as by-products and this type of battery needs to be vented and topped up with distilled water. It’s alos advisable to make sure the boat has a vented battery box.

Flooded batteries usually self discharge at a rate around 6 – 7% per month so over the course of a long winter, or period of non use could discharge your battery by 30 – 40%. That’s assuming good conditions, as it could easily be higher. This type of battery will almost certainly require some off season charging

Discharging more than 80% of a flooded battery type will effectively kill the battery. However, a flooded lead acid battery can much more easily handle overcharging than other countering Gel and AGM type batteries,

Gel Batteries – This battery type is a combinations of sulphuric acid, silica, distilled water and phosphoric acid. They are called ‘recombinant’ batteries as the oxygen and hydrogen venting when charging reform to recreate water. These types of batteries charge at a lower voltage and thus high voltage overcharging should be avoided.

Absorbed Glass Mat – AGM batteries are normally maintenance free with an added benefit of being better at receiving shocks and vibrations, which is useful on a boat. AGM is a specially designed glass mat designed to wick the battery electrolyte between the battery plates. AGM batteries contain only enough liquid to keep the mat wet with the electrolyte and if the battery is broken no free liquid is available to leak out. Again, useful on a yacht.

A bonus to the AGM type battery is that they have a lower internal resistance and thus recharge faster. They are also considered ‘long life’ batteries as the discharge rate with no load is around 3%, so these types of battery make the AGM style an ideal choice for the small yacht owner. Unfortunately they are also the most expensive. I like these types of battery as they seem purposely designed for yachts but you will need a smart charger to regulate the power delivered to these battery types.

Properly maintaining a battery should give it a lifespan of around 3 years

Obviously, your yacht battery is much the same as your car battery in many respects. When the engine is running, the engine is used to deliver voltage to battery to keep it fully charged. Thus if you live near your boatyard then popping down every now and again and running the engine for an hour or so could well top up your battery just fine.

Yacht batteries however are much like using the radio and electric windows in a car without the engine on. There is a lot of draw on a yacht battery, the most obvious being the need to maintain navigation lights whilst sailing or an anchor light. A well maintained battery is not just for your ipod music system.

Some Basic Battery Tips

You should stay with one style of battery, don’t mix and match. Each type prefers a specific charging voltage and thus can under or over deliver charge to one of the mismatched batteries with both options not being good for the battery. A smart regulator is a wise investment, and almost a necessity for AGM or Gel batteries.

Marine battery bankA shallow discharge will result in a longer battery life. Purchasing a solar trickle charger therefore seems like a wise plan.

Despite the name, ‘deep cycle’ battery it isn’t advisable to keep fully discharging your battery before recharging. An 80% reduction is considered about the limits.

Don’t mix battery ages as a failing battery can effect significantly a new ones performance. Coupled batteries tend to level out and you don’t want a good battery declining to the level of an old battery.

Check and maintain distlled water levels in lead acid batteries and clean terminal connectors regularly.

Personally, I prefer deep cycle batteries but the disadvantage with them is that they aren’t as good at delivering short bursts of power, such as trying to overturn a heavy diesel marine engine. They are designed for long continuous use and can be discharged beyond the recommended 50% discharge that other battery types enjoy.

Effects Of Overcharging The Battery

So you’ve taken the wise decision and removed the battery from your yacht for safe winter storage and to keep it in a well maintained condition. Free from saltwater and the corrosive effects of the weather you can plug it in to the battery charger and all is well.

Overcharged Marine batteryWell, hang in there because you could well damage your battery quite fatally if you over charge it.

With the lead acid batteries the effect of overcharging is to produce hydrogen and oxygen which is an explosive mixture at the best of times.

When a battery is plugged into a charger the battery starts to receive charge. When the battery voltage is sub optimal, and is partially discharged the charger starts to recharge the battery. Once at 100% most chargers then give the battery what is known as a tricklt charge, that is a smaller delivery of power. Make no mistake though, the battery is still receiving a charge even though it doesn’t need it.

Overcharging can change the internal chemistry of the battery and lead to a loss of capacity and if unchecked can permanently disrupt your batteries ability to store power, thus defeating the object of the battery. At worst it won’t hold any charge at all an be potentially dangerous.

You are then of course talking about having to purchase a new battery.

Impact Of Letting Your Battery Die All The Way

Marine battery bankSo what about the other way. Instead of overcharging, you will discharge the battery and then top it up to 100%. Like you do with your phone. You use it until the power is 4% and about to die and then put in the wall to charge.

Well, turns out you will damage your yacht battery doing this. Most batteries you can do this with once or twice. A new battery has a significantly better capability to withstand this type of abuse, as does a deep cycle battery. However, essentially the stability of the battery dies and may not deliver the 12v supply that you need to power your yachts systems.

Most batteries don’t like being discharged beyond about 50% before recharging. Deep cycle batteries can go further, to a maximum of 80% but the internal battery chemistry dislikes being overly discharged.

The Happy Medium – Whereabouts Is That Then?

So now we are in a bit of a conundrum. We can’t oversupply a battery with power. We can’t let it fully run down and now have to work out where a good amount of discharge is allowed before recharging to 100%

If you work on the theory that a battery will loose about 10% of its power every month Thus 6 months of storage, you will have a battery at around 40% available power. Now depending upon your yacht, this might not be sufficient power to turn over an engine that hasn’t been used in 6 months.

What is recommended is that you don’t let the battery drop to below 80% capacity and use the small and often approach. Once it is topped up, let it sit idle with no load and wait for it to get to 85% to 95% of available maximum power and then recharge. Expect it to take around 2 weeks to drop this far without a load being applied. Keep the battery in a temperate climate and away from rodents or other tools that may damage it if dropped.

It’s important to remember that no matter how careful you are a battery has a lifespan. Treating it well you can get 3 to 5 years of life out of a marine battery, but treat it badly and you could be buying one every season.

What this means in practice is that if you are planning to be away from your yacht for under 2 months then those two months should produce a battery drop to 80% maximum power. Thus anything over 2 months away from a stowed yacht and you will need to remove the battery for recharging. At least in battery quality of life terms.

Depending upon your level of interest, deep cycle batteries will maybe be your most preferred option. This is because they are built with thicker plates compared to the starting batteries and can be regularly discharged to fifty per cent without damage.

How To Remove A Battery From Your Yacht

Often removing a battery from a yacht is not as easy as removing a battery from a car. As this may require more attention and also added skills so as not to make mistakes that will either destroy the battery and the yacht.

As winter can last a while depending upon where you are (The North?), most likely you will need to remove your yacht battery or batteries.

Marine battery bankBEFORE doing anything around your yachts power system make sure your power is disconnected and all appliances are off. To make doubly sure, you can go around the yacht and turn of everything. Swich off the panels, the refrigerator and TV’s. Make sure there is nothing charging, thus withdrawing power. Switch off all lights, cabin or otherwise. After locating the battery station then you should see black cables and red cables. These are the common colors for negative and positive terminals.

A good tip at this point is to take a photograph to record the whereabouts of cables if you are not sure what you are doing. It will identify what battery went where (if you have more than one) as well as the location of any braces that are being used.

Start by disconnecting the negative cable, which is the black one.

Next, take off the connecting terminals of the red one, which is the positive terminal and keep the connectors away from each other. Make sure they don’t touch. They may well be stiff after being on their for a number of seasons and you will need a good torque wrench set.

Once the batteries are free from restraint and the cables safely tucked away so they don’t lay across any terminals then you should be able to start taking the batteries out, one by one. These batteries are going to be quite heavy so be careful. They are now ready to take away and store in their safe location.

Put all the screws, bolts and braces in a small bag and make sure you remember where you put it. Probably a good idea to label it.

For a really great demonstration, this video is helpful

How to Charge the Battery Outside of Your Yacht (Trickle Charger)

As mentioned before, your typical yacht battery will drop to 80% capacity within a 2 to 4 week time frame. Absent any use, the battery will no longer be getting any top ups from an alternator while an engine is being run.

You can actually use a car charger if you have one and put it on trickle charge and monitor the battery capacity. You don’t want to keep the battery on charge once it’s at 100% as you will risk over charging it and damaging the battery.

It should only ever be charging from a 20% decline so it shouldn’t take too long to regain its maximum status. Some chargers have a winter setting for this purpose. Keep an eye on how long it takes to drop to a certain level and how long it takes to recharge from this drop. You should then get an idea of the routine you need to repeat. It wouldn’t be untypical for a few hours charging avery 3 or 4 weeks to keep the battery at optimal levels.

The trickle charger is basically known to charge at a very low amperage rate. And in most cases, it is considered to be more of a luxury than of a necessity. Having considered that you are not using your yacht for a period of time, a trickle charger may be the convenient option. Hence, before connection, ensure to set the voltage and amperage appropriately for your battery. Some chargers have a 12v or a 24v setting.

Alternatively, solar trickle charger are an option. Using the free energy of the sun they keep a battery topped up and many now come with overcharge protection. Personally I prefer just to remove the battery from the charge. That way I know that it’s not receiving any overcharge.

Putting The Battery Back After Winter Is Over

After a lovely snowfall and Christmas dinner and some sledging, finally the biting wind is giving way to tiny glimpses of sun and you are thinking about going sailing again. Throughout the snowy months you have been exceptionally diligent and charged the yacht battery every time it dropped to around 80% of its capacity. The good weather is coming and with more sailing comes the yachts own capacity to charge its own batteries. The batteries are good to deliver to a 12v system and you won’t need to replace any.

They have just come off a recent charge and the batteries are ready to go back into the yacht in the hope that they will start the engine.

If you’ve taken them out and still have that photo (did you email it to yourself with the subject line of ‘yacht batteries before removal’) then this should be a relatively straight forward process. It’s a simple matter of doing the reverse of removal to install them. Now where did you put all those bolts and braces?

Essentially you need to locate the batteries in their respective placement areas and place the positive (red) cable(s) on, and tighten up slightly. Then place the black (negative) cables on the terminal and tighten so that there is a good connection.

Place the bracing on, and if possible check that there is current flow. Make sure they are firmly fitted and you want to test a few of the yachts systems to make sure all is well with the electrical circuits. If lights are coming on then you have yacht power.

You can now firmly tighten up the respective nuts to make sure those batteries are securely located, and won’t slip and slide all over the place under a hard heel.

If the yacht is in the water and no lines are near the propeller then slip her into neutral and fire up that engine. Mission accomplished.

If you#d like a quick look at charging a battery here’s a quick little video.

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