Battery bank replacement: power projects aboard

Battery replacement project

More than six months ago our battery bank ticked past the five year mark. That’s a pretty good life for marine AGMs, so we’ve been thinking for a while about where and how it would be replaced. You can’t always count on easy access to boat bits in the islands of Southeast Asia, so the big concern is that the bank would nosedive in an inconvenient location with complicated and costly results. We wanted to wait as long as possible, but expected it to become necessary at any moment, making it the top priority in a string of power projects on Totem but one that hung in the air for several months.

Battery replacement project

What we put in
Battery replacement project
Totem has AGMs (Absorbed Glass Matt), the deep-cycle sealed batteries commonly used on cruising boats. As we talked to other cruisers in the area, many reported good results with AGM batteries sourced from a local manufacturer. Good batteries, fresh from the factory, with minimal shipping cost (heavy batteries can make it absurdly expensive): a perfect combination. We just had to make our existing bank last long enough to get to the Malay peninsula!

When they finally arrived, it took a couple of dinghy loads to manage the weight. Each one is heavier than Jamie! Thank goodness for friends in the cruising family to help get them on board. If you’ve been on Totem’s Facebook page recently, you already saw how handy the dinghy davits were for loading these monsters on board. They came in really handy, not just to have purchase on the weight, but because could swing them out over the dinghy, then back over the deck, vastly simplifying the transfer.

Tweaking location

Moving weight on the boat was a meaningful side benefit of the project. Totem has listed slightly to starboard since we bought her in 2007. This is primarily the result of tankage being moved around from the original plans, skewing weight on the starboard side. Our house battery bank was also located on the starboard side, just under the nav station (photo above). For the new batteries, Jamie built a box under our bunk in the aft cabin. This would create a significant weight shift: with about 400 lbs coming off the starboard side, and over 600 going in just to port, we might just get a flat boat.

Battery replacement project

Of course, it’s never as simple as just building a box. Over a period of several weeks, Jamie built out the box for the new set under our bunk: grinding down fiberglass (wow, that’s a lot of fine dust), fitting lumber to make a strong base (discovering the many lumber yards on Langkawi!), and building the frame up (I love the smell of polyester resin in the morning…not) to securely hold the new bank. It was a lot of work.

Battery replacement project
before wiring, double-checking with Calder

What about Lithium?

Lithium batteries are getting more common on boats and we’re familiar with some installations that get raves from their owners, on the yachts Tahina and Nimrod. They have some great benefits: because they can be drained more deeply (and charged more fully) without affecting their lifetime use, which provides far more usable power for the same total amp hours in a bank. Their lifetime value- amps delivered vs cost- is superior. This saves weight, too, a meaningful factor on some boats.

On the other hand, they have a higher upfront cost. In addition to the battery cost, we’d have to take on additional projects. We’d need to make sure our alternator was big enough (it probably isn’t). We’d need to check the voltage requirements of every device on the boat, because unlike AGMs and their ilk, lithiums can put out higher voltage- over 15v- in a 12 volt system. For voltage sensitive devices like our watermaker, we’d have to put in a regulator.  Maybe in five more years we’ll move to lithium batteries, but it’s too much to take on now.

It’s all good.

The new bank is 1000 amp hours, a nice bump in capacity that we definitely need. Totem is floating- dare I say it? nearly level on her lines. I don’t get to examine the waterline often, but every time I melt butter in a frying pan and don’t see it all run immediately down to one side, I’m going to smile.

Battery replacement project
Amped up readers know we get a charge out it when you read this on the Sailfeed site.

6 Responses

  1. Behan,
    Every liveaboards curse is batteries and power management (well besides the toilets). We pamper them, constantly watch them under anchor and cherish them. We never have enough. I know we need new ones but I am hoping we can hang onto them for just one more season…

  2. WOW! A thousand amp-hours . . . I’m jealous! Having enough power is one of the big keys to having a livable cruising lifestyle, or at least it was to us. We never went wild on the gizmos, and turned off lights and so on, but not freaking every time we wanted to turn on a light or use the computer is HUGE. It’s one of our big questions with the new boat: how many amp-hours do we need? It has propane refrigeration, you see, and LED lights (which weren’t out when we cruised Que Tal).

  3. I am impressed with your 1000 amps/hrs. We too replaced our battery bank last summer. Fortunately we were on the hard but to save our backs we installed golf cart sized AGM’s. Since we are a 24v boat that took a lot batteries. But very are very happy now to have that behind us as I am sure you are too. Enjoy the power.

    1. Hi Sophie, the wind turbine tops out at 420 watts and the solar panels are 570 watts. Of course, you need wind and sun to max them out! We are in the rainy season near the equator, it will be much better in the trades next year.

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