Reference Materials
Alternator & Parts Price & Spec sheet & Alternator Upgrade guide
Q: I want to charge my new lithium batteries as fast as they can accept it. What do I need?
A: One of the great features of high-grade lithium batteries is the ability to recharge very quickly using powerful high-output alternators. These can often be mounted in your stock alternator position. Paired with an advanced regulator like a Wakespeed AP500 or WS500, you can maximize the efficiency of the alternator, allowing greater charging power and less fuel consumption.
Q: How much power can I produce with a new high-output alternator?
A: This depends on the alternator, the lithium battery brand/type, amp-hour capacity, the alternator RPM, and the programming of the regulator. For example, with one of our common setups, you could get 230 amps at 14V at just above engine idle – using one high-output alternator in the stock position. Note that for yachts with high energy needs, higher outputs are often required, and often higher voltage systems are used.
Q: Why higher voltage?
A: Compare these output figures from the APS HPI 12V, 24V, and 48V (all fit into the stock alternator position) for an engine rpm of 2000 with a 3:1 pulley ratio = 6000 alternator rpm:
@ 13.5V: 256A/3.4kW
@ 27.0V: 156A/4.2kW
@ 54.0V: 114A/6.1kW
Note that the effective actual output is best expressed in kilowatts (voltage x amps = W).
You can see that at the same rpm, the 48V APS HPI outputs nearly 80% more power than the 12V version.
Q: What do you need to know about my boat and batteries?
A: To start:
- Engine make/model/year
- Alternator mounting style
- Existing belt & pulley type
- Battery bank being charged: voltage, capacity, brand, chemistry/type
- If Lithium-ion batteries: What type of BMS? Can BMS communicate?
See Alternator Upgrade guide and fill out all the fields with photos.
Q: BMS? What’s that? What kind of BMS do I have?
A: Battery Management Systems, or BMS, are key components of lithium-ion batteries that protect the cells from damage, from hot and cold temperature extremes, over-and-undercharge events, overloads, and short circuits. They disconnect the battery from the electrical system when they reach a certain cut-off point.
Internal BMS – BMS is integrated into the battery structure itself.
External BMS – BMS is a separate component that protects one or more batteries.
With external communications – BMS is able to send information to a data network system. This allows safer and more customizable charging parameters.
Without external communications – BMS is standalone, unable to communicate with the system. This can be less safe, and may require carefully thought-out configuration.
Q: What do you mean, with external communications?
A: This is when the BMS is capable of sending information through compatible data networks on the boat via CANbus communications standards like J1939, RV-C, etc. This allows the BMS to integrate with the engine and alternator regulator to actively manage its charging and load sources to prevent a BMS from initiating a cut-off.
Q: What’s a BMS cut-off?
A: The cut-off point is when a BMS disconnects the lithium-ion battery from the electrical system in order to protect the cells in the battery from damage. With integrated BMS and alternator communications, when the battery approaches voltage or internal temperature limits, the charging current and/or voltage is reduced as needed to prevent a cut-off, and also maximize both fast charging and battery life.
Q: Why should I be worried about a BMS cut-off?
A: If the BMS disconnects itself from the electrical system while the alternator is running, the energy from the alternator will suddenly have nowhere to go, which can lead to a voltage spike before the alternator shuts down. This can damage the alternator, and possibly other electronics on board.
Q: I just bought new lithium-ion batteries and want a high output alternator, but the battery doesn’t have a BMS that can communicate externally. What now?
A: OPE has workarounds that can help prevent potential problems with BMS cut-off events that aren’t communicated to the rest of the boat’s systems. We can program the alternator regulator conservatively and offer other design and product solutions that will attempt to keep the system safe in the event of an unexpected BMS cut-off.
OPE will do everything in our power to create a safe and effective system, however we can not be held liable for damages caused by lithium-ion batteries that are unable to communicate externally.
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