(typically by 50%), the difference in cost per kilowatt-hour gets a lot smaller, and lead-acid’s energy density numbers become much worse. Te bottom line: if you deeply discharge a lead-acid battery frequently, the replacement costs over time can turn it into the more expensive choice. Torqeedo’s 48V battery is rated at 5


kWh of capacity, and it lists for $5,200, or $1,040 per kWh. Why is it priced so much higher than their 24V battery? Tis particular battery uses proprietary technology developed by BMW for their electric cars. And the “lifetime” of the 48V battery is rated at more than 3,000 recharging cycles, rather than only 800 charge-discharge cycles for the 24V battery (which is comparable to a deep-cycle lead-acid AGM battery used at 50% depth-of-discharge). The high-voltage 5-kWh battery weighs only 80 pounds—a little more than a 100Ah lead-acid battery that has only 1.2 kWh of capacity (nameplate, not derated). And because Torqeedo’s 48V battery is designed for automotive applications, it’s much more compact (4.5 kWh per cubic foot of space) and is capable of integration and monitoring using CAN communication and control bus com- ponents, features that are required in electric cars. Unlike Torqeedo, ePropulsion (www.


epropulsion.com) designs all of their electric outboards to operate at 48 volts, which keeps the size of the power cables more manageable. And they offer three battery options, with 2, 4, and 9 kWh of storage capacity selling at $1,400, $2,300, and $4,400, respectively. And in contrast to Torqeedo, ePropulsion’s bat- teries are built using lithium-iron-phos- phate (LFP) cells, which is considered to be a safer technology than NMC, albeit a bit heavier and slower to charge. Teir mid-capacity battery weighs 117 pounds and takes up 1.8 cubic-feet of space (35 Wh per pound and 2.3 kWh per cu- bic-foot). Like Torqeedo, ePropulsion batteries can also be connected in parallel (up to sixteen of them, along with a dai- sy-chained CAN communication cable) to increase storage capacity. In addition to proprietary batteries


from the motor manufacturers, most electric outboards can also be powered by “drop-in” Li-ion batteries. BattleBorn Batteries (www.battleborn batteries.


56


Torqeedo’s 48V, 5-kWh battery with CAN control bus (Torqeedo photo)


com), based in Nevada, designs and man- ufactures stand-alone 12V LFP batteries for solar, marine and RV applications. Each battery has its own high-voltage BSM so that multiple batteries can be connected in series, and in parallel, to build higher voltage, and higher capacity, battery banks. BattleBorn’s batteries are sealed and have IP67 rating (dust tight, resistant to water spray and brief immer- sion). Since they are used extensively by RVers, they are designed to take abuse; and their warranty is considered one of the best. Many more suppliers of drop-in batteries are importing and distributing batteries made in China, where bat- tery-powered vehicle manufacturing is a major industry initiative. For marine applications, look for LFP batteries with “sealed” plastic cases and at least IP65 (dust tight, water resistant) enclosure ratings, such as those from ReLion, Mil- lerTech, AmpereTime, Chins, SOK, and EG4’s WP models. And verify that they can be series-connected (many of the 12V drop-in batteries use BMSes that are not capable of handling the higher stacked voltages). Some LFP suppliers also sell 24V and 48V drop-in LFP bat- teries that can be conveniently bussed together in parallel to increase storage capacity. Tis ensures that the batteries are “matched” and it saves a bit of wiring. Unfortunately these higher-voltage bat- teries don’t seem to experience any pric- ing discounts, at least at the present time. The cost per kilowatt-hour for pre-


mium, US-made, drop-in LFP batteries from Battleborn currently runs around $730 per kWh (as of August 2022). For comparison, the cost of ePropulsion’s 4-kWh battery works out to $560 per kWh, which coincidentally is equal to the cost of a deep-cycle AGM battery when derated by the usual 50% of name- plate capacity. Good news: Li-ion bat- tery prices are decreasing with capacity


and time. ePropulsion’s larger-capacity 9-kWh battery already breaks the $500 per kWh “cost barrier.” And while some of the imported LFP drop-in batteries now sell for less than $400 per kWh, it’s entirely conceivable that large-capacity Li-ion battery prices will fall below the price for deep-cycle AGM batteries, and potentially less than $200 per kWh, within a year or two as manufacturing volumes ramp up. To charge the batteries, on sailboats,


where shadowing by sails is an issue, it’s common to use multiple smaller solar modules with individual charge control- lers. And since the direction of the sun is always changing, the best controllers are capable of maximum power point tracking (MPPT). On a solar cruiser, however, shadowing should not be much of a problem, especially if the solar array is also used for shade. Terefore a single MPPT charge controller (or maybe two, for redundancy) with larger, series-con-


Torqeedo’s 24V, 3.5-kWh battery (Torqeedo photo)


nected modules can simplify the wiring and reduce the cost per watt of the panels. Te KID controller from Midnite Solar (www.midnitesolar.com), for example, can accept series-connected modules up to 150 volts; and it can be programmed to charge 12, 24, 36, and 48 volt batter- ies. Its maximum output current is 30 amps—or almost 1.5 kW into a 48V battery; and multiple controllers can be paralleled to increase the output. Tere is a “marine” version of the KID, but both models are rated IP64 (dust tight, splash resistant), are UL listed, and have a very good performance record. Victron (www.victronenergy.com) also produces a series of charge controllers (plus in- verters, batteries, and power monitoring systems) that have a good track record of use in RVs and on sailboats. Te charge controllers are rated by maximum input voltage and maximum output current, and are priced accordingly. The latest


SMALL CRAFT ADVISOR


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84