Professional BoatBuilder - December-January 2018

34 PROFESSIONAL BOATBUILDER

SYSTEMS: Battery Technology

If you have to run an engine

(the main engine or a genera-

tor) solely for the full charge

cycle, it is extraordinarily inef-

 cient. An antidote to this is to have

su cient solar panels on board, but the

array must be con gured so it is pro-

viding the necessary extended charge

cycle, as opposed to being consumed

by house loads. An even better solution

would be to eliminate the sulfation

issue and thus the need for the extended

full charge cycle.

Some years ago it was discovered

that by sprinkling carbon dust into the

active material in the negative plates of

an AGM battery, the carbon inhibits

sulfation. Now, a family of these bat-

teries, known as NSB Blue, is available

from NorthStar. I have yet to test any,

but this appears to be a signi cant

step forward for partial-state-of-charge

operation.

 e ultimate battery in the carbon-

doping world comes from Fire y. In a

“normal” lead-acid battery, there are

plates with a grid composed of lead

least amount of heat during fast

charges and discharges.

Within the AGM family, we have a

subgenre described as thin plate pure

lead (TPPL), the best known of which

are the Odyssey and SBS batteries

from EnerSys, and the NSB Energy1

batteries from NorthStar.  ese bat-

teries have the highest charge accep-

tance rate of any AGM battery with

the best e ciencies.  ey will tolerate

repeated deep discharges, down to

around 20% remaining capacity. Over

the past eight years, I have partici-

pated in aggressive testing of dozens

of these batteries. In general, they have

performed well, except that unfortu-

nately if operated in a partial state

of charge, they su er from sulfation.

 is means boat operators regularly—

ideally once a week—must subject

them to an extended charge cycle at

low rates of charge.

and repeatedly terminates the charge

before the batteries are fully charged

(this is known as operating in a partial

state of charge), the batteries su er

damage from sulfation. (See “Solving

Sulfation” on ProBoat.com.)

Lead-acid batteries are also rela-

tively ine cient at converting electri-

cal energy into chemical energy and

vice versa.  is ine ciency manifests

as heat. If you force the pace on the

charging side, a lot of heat is gener-

ated. If the battery gets too hot, it goes

into a condition known as thermal

runaway, in which the internal elec-

trolyte boils, producing hydrogen and

oxygen. In the worst cases, the battery

blows up, or the vented hydrogen

accumulates inside the boat, is ignited

by a spark, and the boat blows up.

Of all the lead-acid batteries cur-

rently on the market, the absorbed

glass mat (AGM) family has the best

overall properties for most recre-

ational cruising boats. In particular,

these batteries have the highest charge

acceptance rate of any lead-acid bat-

tery, to the highest states of charge,

and, having the highest efficiency

(around 85%, as opposed to around

60% for wet-cells), they generate the

As carbon has been shown to inhibit

sulfation, Fire y replaced the lead grid

on the green battery, right, with carbon

foam. The thin plate pure lead (TPPL)

battery, left, is a subset of absorbed

glass mat (AGM) batteries; it can

endure deep discharge but is still prone

to sulfation.

Far left—Lead-acid batteries can

suffer damage from sulfation,

which occurs when they’re oper-

ated at a partial state of charge

and crystals form on the plates.

Left—The in ated balloon shows

that  ammable hydrogen is leak-

ing out of a sealed battery, a

result of overcharging.

Batteries170-ADFinal.indd 34 10/31/17 12:19 PM