Always keep the engine battery charged

Always keep the engine battery charged

Date: Thursday, September 12, 2024. 2038Z
Location: 38°41'26.4N, 20°41'58.7E — Vlicho, GR

Whenever new people come onto the boat, apart from the brief safety talk, I usually explain why boats have two batteries. I go through the whole “don’t ever disconnect the batteries while the engine is running” stuff, to put the fear of god into them. I show them how to move the battery selector switch from 2 (House) to 1 (Engine) when starting, and then when the engine is running, I show them how to set it to Both and finally back to 2 when the engine is stopped. You’d think I would pay attention to my own blathering lectures!

We had a nice day in Spartochori, but as with everything this year, the fun was short-lived. Jerry, the usually-very-friendly co-owner of Taverna Spilia, and the guy who takes your lines when you arrive, was at pains to tell us that a bad storm was coming through, from the north-west. You go Bows-To here because there is a lot of spoilage and rock beneath the quay, which would make short work of your rudder. It’s fine. Come in with your bow lines ready, and Jerry will get you sorted. There’s a lazy line so you don’t even need to kedge your way in. The only down-side is having to get on and off the boat via the bow.

However, a gale from the north or thereabouts will bring a large fetch into the bay and your bow will surely bounce off the quay wall. Even if you stretch out the bow lines and pull in on the lazy line, it would not be a comfortable night’s sleep as you await the dreaded crushing noise of fibreglass against concrete. Over the course of the day, boats slipped their lines and headed for shelter. Boats which arrived, were turned away. We did our usual morning coffee, and prepared to depart. Only to find the engine battery was very dead. House battery and engine battery, deader than dead.

I’m not sure if I mentioned this, but the trick to happy cruising power is to keep the engine battery for one function only. That function is starting the engine. Think of this as Rule One of battery management. The engine will repay it by keeping it topped up. On Nikea as with most boats, the solar panels drive directly to the house battery. When it’s particularly sunny, you don’t need to put the battery selector to both (which connects both batteries together, and shares any charging voltage). This is because the engine battery should always be at 100%. Just keep it away from running the fridge, the lights, the phone chargers, and everything else. Definitely share the engine charge with the house battery, so depending on your setup, connect them together or set the selector switch to both when the engine is running. As your engine battery shouldn’t need much energy restored from the starting operation, it’s only fair to let the house battery have some of the alternator power.

So, on our first day, Rabbit used the engine battery to turn over the engine and try to prime the fuel system. Absolutely nothing wrong with this, except I should have remembered that. I should have considered that I now had an engine battery which was not anywhere near a full charge. We motored from Vlicho bay to Spartochori, a journey of perhaps less than an hour. The engine battery would still be in a low or critical state. In addition to this, I discovered the battery switch had been left at both which means the engine battery would have shared what meagre solar power was on offer, but in turn would also have shared the load. I should have checked. I didn’t. Well, I did when I went to start the engine.

So here’s the problem. We’re in a bay which has an impending, bow-crushing storm approaching. We can’t sail backwards, so hoisting a sail won’t do anything for us. We have no battery charge and no charger or indeed shore power. What are the options? We could possibly tow ourselves into the bay using the dinghy and the very meagre outboard, drop the anchor, and try to brazen out the storm and the swell in the middle of the bay. We could take the ferry to Nydri and charge the battery or buy a new one, except it’s now getting late. However, we do have a solar panel…

Engine batteries and toilets have one thing in common. Have you ever waited for a toilet cistern to fill, then decided it was full enough and operated the lever only to find it wasn’t anywhere near full enough, and now you’re back at zero again? A starter battery has the same fatal flaw. It really should have a name. You can charge the battery for an hour, decide that should be enough juice to spin up the diesel engine, so you give it a go, and suck all of the hour’s worth of energy out of the battery and now you can start the timer again. The trick is to wait as long as humanly possible. Longer, even.

We disconnected the house battery entirely, and connected the solar panel to the engine battery. Luckily there’s a decent voltmeter on board (don’t leave port without one of these!). I know it’s decent because I bought it. Forget your €6.99 cheapie things in the chandlery unless you can’t find anything else. If you have any concerns about electricity on board a boat, and I mean even the slightest concern, buy a decent “Digital Multimeter” or DMM. Expect to pay upwards of €40 but your sanity will be assisted greatly. So, we sat in the cockpit, considering our fortunes, and every hour, checked the battery voltage. Hour by hour, it crept up. I figured we had until around 4PM at which point, given the landscape in Spartochori, the panel would not produce any more power. Whatever energy was stored in the battery at 4PM was going to have to do us. Meanwhile, a very agitated Jerry kept telling us to move. We explained about the battery and the solar panel, but he seemed to think we were making excuses and trying to overstay our welcome. At 4PM, we duly restored the power circuits to their original condition, set the battery switch to 1 (Engine), and cranked the engine. It started! Relief all round. We slipped our lines and decided to head for Kalamos.

I’ve written about Kalamos before. It’s a tricky harbour to get into, and it’s not a great swimming location. However, it’s very sheltered from anything westerly or indeed northerly. Plus, George (the harbour master) is very friendly and it’s a delightful place. But it’s now after 1600 hours and I can’t be the only one to think Kalamos is a safe harbour against the storm. It is likely to be full. The only other alternative is another night in the cockpit and rain in Vlicho. So normally I would say let’s not bother. But an anchorage such as Vlicho is never ever crowded. You can arrive at any stage and find a bolt-hole. Kalamos is quite a distance away, but we’re using the engine, and it would be nice to get both batteries to 100%. We decide we might as well burn some diesel and motor towards Kalamos anyway. At the same time, we tried to make some phone calls to ascertain how full it might be. We got to the northern tip of the island, when we finally got through on the phone, and yes, not an inch of quay wall. So much for travelling at the end of the season!

We did a 180 and headed for Vlicho. Sigh! The bright news is we got a very solid charge on the batteries, and I can now go back to lecturing people on the importance of never letting the engine battery go flat! We are now at anchor right where we started two days ago, at the southern end of Vlicho bay, waiting for whatever Mother Nature might have in store for us.

Dermot Tynan's Picture

About Dermot Tynan

Part-time sailor, full-time procrastinator. Software Engineer, Writer, Film-maker. Interested in all things cloud, sailing, autonomous systems and robotic sailboats.

Galway, Ireland https://intothemystic.eu