Batteries

What are the best batteries for an Electric Boat?

We recommend Lifeline AGM Batteries for Solar Electric Boats and Odyssey AGM2 Batteries for Diesel Electric Boats or boats equipped with an Outback Inverter Charger.

Lifeline Batteries are hand made to the highest standards, typically last 8 to 10 years, are rated at 500 cycles at an 80 % depth of discharge and are made in the United States.   Lifeline Batteries have a lug terminal option, which allows fastening of the cable terminal directly to the lug terminal  This eliminates the need for a battery clamp terminal, which gets rid of two connections per battery, eight connections per 48 volt battery string.   Lifeline Batteries are forgiving to accidental deep discharges, charge well at low currents typical of solar charging, are compatible with most standard lead acid charging algorithms.  Lifeline Batteries Charge at 14.4 to 14.6 volts bulk and 13.4 to 13.5 volts float.

Odyssey Batteries are are the second generation of AGM batteries, also called Thin Plate Pure Lead (TPPL) batteries.    Odyssey Batteries require a unique charging algorithm, charging at 14.7 volts bulk and 13.6 volts float.  Odyssey Batteries require either a very high current charge or an extended absorption time period.   Preferrably, the absorption time is truncated by a minimum current setting rather than a set time period, to insure the batteries are fully charged.    Odyssey Batteries are not forgiving to accidental complete discharges.

Both Lifeline Batteries and Odyssey Batteries are rated to 80% depth of discharge.

Do you recommend Lithium Batteries?

Lithium batteries are definitely the way of the future and prices are coming down, but they are still about 3 times as expensive as a good AGM.  Though most boats can benefit from the space savings, weight is not so critical on monohulls.    We recommend Lithium for race boats and for catamarans or trimarans.   There are a number of companies selling great Lithium batteries with internal cell balancing.   If money is no object and you want performance in a small space, Lithium is the way to go.

Lithium can also be purchased as independent cells for less:

Lithium cells are at 2.5 to 3 volts and require cell balancing, which can be accomplished in one of two ways:

1) if one cell in the string becomes too high in voltage, that energy is diverted to one that is lower in voltage.   The problem with this approach is wires end up all over the battery pack.

2) a resistive load is placed on each cell that burns of any power above a given voltage.   The problem with this is having resistive loads all over your battery pack.   We do have one boat in construction right now that is employing this method and will be able to report results back soon on this technology.

How should I mount the batteries in my boat?

ABYC states that batteries should not move any more than 2 inches in either direction.    I recommend that they don’t move at all.    If all of your batteries move 2 inches at the same time, every time you tack the batteries move.   If your batteries weight 1,000 lbs, and they all move 2 inches that can affect how your boat handles.

Strap the batteries to a wall or a bulkhead if possible.   Use wood to hold them down.   If they are mounted on the hull, make sure they don’t point load the fiberglass with one of the battery corners.   Place a sheet of 1/4 inch marine plywood under the battery if mounting onto the hull and you need spread a point load.   Fiberglass in schedule 80 PVC tube with a space under it to pass a strap.   Double of triple strap big batteries in.

Where do you put the fuses for the batteries?

Sometimes we place the fuses directly on the batteries but we would rather place them in a fuse holder as close to the battery as possible.