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Electricity on Board

Published in Dinghy Cruising Journal

Reading Roger Barnes' Cruising Dinghy Companion convinced me that I should have battery power on board to be self-sufficient for 2 weeks.I therefore planned to have two 12V batteries under the bridge deck of Hatseflats and added 60kg to the weight calculations.Reality proved to be unimpressed by my planning and so I sailed Hatseflats without batteries during the first season.

During the winter of 2019 I listed my electrical requirements:

  • ICOM M73-EUROVHF radio 7.4V
  • Garmin ETREX 20x GPS 2xAA
  • all-round light 3xAAA
  • two smartphones
  • 5V Powerbank 4000mAh for emergencies

Since each device is battery powered, the 12V battery would only only needed to charge batteries.I reckoned that my modest requirements would be met very easily by installing 2 YUASA 20Ah jetski batteries.

At only 7.5kg each the Jetski batteries would save 45kg compared with a pair of standard 12V car batteries.The advantage of using AGM batteries is that they are robust and watertight and therefore safer than conventional lead-acid batteries (but also a lot more expensive).

When I explained my plans the dealer told me that the YUASA batteries would be short-lived if only used to charge other appliances.With this plan out of the window, I was pleasantly surprised when a friend offered me a surplus 110Ah 12V AGM service battery from his cruising yacht.I decided to put the 32kg battery under the aft deck because this had proved to be the driest part of the boat and its weight here would not hurt the balance of the boat.

Before the 2019 season I installed the battery on a foam pad on the bottom of the aft compartment and glued four tie-downs to the bottom and inner bulkhead to hold the battery in place. I bought a CTEK MXS 5.0 charger to charge the battery through a 12V socket.I installed two 12V sockets and two USB 5V sockets in the aft bulkhead. A battery charger running off a 12V socket was bought to charge my AA and AAA batteries.

In 2019 Klarie and I sailed 30 times on Hatseflats. Most of our sailing was in F3-4 conditions but we also had some heavy going in F5-6 beating up lake IJsselmeer in a chop.We charged our phones, VHF and batteries off the 12V battery and never bothered to charge them before a trip.During the entire season I had to tighten the straps of the battery only once. Each 2-3 months I charged the battery using the CTEK charger to 12.6V. We never discharged the battery below 12.4V.In July I replaced a corroded USB socket. This took a couple of hours because I had to unwire the battery. Afterwards I bought a mains-switch but never got round to install it.

From a technical point it was all going well. However I was not entirely happy with the new setup. First because lugging a big battery around is comparable to taking a 10-year old on each and every trip. Now I don't have a grudge against 10 year-olds but I can do without the weight if they don't add to the conversation.With the extra weight Hatseflats appeared a bit slower and less responsive than in the first season.The second problem was the loss of storage space due to the battery.The big aft compartment of Hatseflats is reached through a rather small hatch. With the battery sitting behind the hatch we could only store small items under the aft deck.

At the end of the sailing season I realised I needed less power but more storage space.I found a lightweight power supply in the form of the XTorm Power Bank Brick 23K. This 5V 23Ah power bank has a power inverter to provide 220V AC through a power socket.The 5V USB outlets can be used to charge smartphones, batteries and power banks.Its AC power provides max 80W which helps to charge your laptop or maybe your power drill.The Power Bank Brick itself is charged from a USB connector. So typically you would charge the Powerbrick at home or in the car driving to the venue and recharge when needed in a camping or marina during the trip.

Using the AC inverter of the Power Bank Brick (for example to run an AC battery charger or the VHF charger) should best be avoided.So I bought a GoalZero Guide10 charger to charge 4 AA or AAA batteries off the USB outlet of the Powerbrick.To make the most of the Powerbrick I now charge the VHF, AA and AAA batteries before going on a trip. The Powerbrick and other adaptors now fit in a small watertight sandwich box.

I removed the battery, sockets and wiring from the aft compartment and gave it away to a colleague with a garden plot where its size and weight will not be a problem.The reclaimed space under the aft deck will be very useful when we take Hatseflats for longer trips in the new season.

The lesson I learnt is that there are two extremes: too much power if you take big 12V batteries on board, or too little power if you depend on powerbanks alone. For everything in between, small 12V service batteries would be an ideal solution but they seem don't seem to exist.So if you are without AC power for just a couple of days and use electricity sparingly it pays to travel light and bring a few pre-charged powerbanks and maybe a solar panel.

YUASA AGM battery for Jetskis
Big boat 12V 110Ah service battery - 32kg
Aft bulkhead with power sockets wired to 12V battery.
Power Brick charging VHF, power bank and GoalZero Guide10 battery charger
Reclaimed space for camping gear