LIthium batteries - built in Bluetooth required?

[Cutwater28GG]

Am I reading the design correctly and its alternator to engine battery and then dc to dc charger to lithium?

don't you miss out on lithium fast charge using this method direct from alternator (i recognise this reduces the other wiring changes required) but thats a good feature of the lithium is how fast you can dump power into them.

 

[Submariner]

Am I reading the design correctly and its alternator to engine battery and then dc to dc charger to lithium?

don't you miss out on lithium fast charge using this method direct from alternator (i recognise this reduces the other wiring changes required) but thats a good feature of the lithium is how fast you can dump power into them.

You are correct.

This is where a diesel has a big advantage over a gas outboard for LFP.
The Yamaha F300 has a 70 amp alternator. The diesel engines run alternators around 110amps. It's also easier to upgrade to a bigger alternator on a diesel than an outboard.

You don't want to just connect your alternator to the LFP battery bank. The alternator doesn't know how to charge LFP correctly (different charge profile). Another reason, should something bad happen and the BMS shuts down the LFP battery, that would leave the alternator with no place to send its current which would cause the alternator to fry nearly instantly.

For outboards, the easiest/safest way for engine charging is to have the engine connected to the engine battery. Install a DC to DC charger between the engine and house battery banks. The DC charger knows how to charge LFP. Sizing of the DC charger is usually 1/2 that of the size of the alternator. This is meant to prevent the alternator from overheating due to excessive load since LFP charges so easily, and they are usually larger battery banks meaning the alternator will work harder for much longer periods of time.

For diesels, you could do the same as an outboard illustrated above. Or you could connect your alternator directly to LFP but only if you installed an external voltage regulator for the alternator. Then tie that external voltage regulator in with an external BMS which allows the BMS to tell the alternator what to do. This is how you would be able to take advantage of LFP's faster charging rates with a larger alternator.

The Yamaha F300 with its 70 amp alternator, at most, it'll output 50 amps when cruising at 25 knots. The boat will consume about 15 amps for the chartplotter, radar, sonar, VHF, etc... That leaves 35 amps left over. If I turn on the hot water heater via the inverter it'll consume another 65 amps, resulting in a 30amp deficit.

While LFP does have a great feature of being able to be charged quickly, my Yamaha outboard alternator just isn't big enough to really take advantage of that. I put in a 30 amp Orion-TR DC to DC charger (1/2 the size of my alternator). I get 30 amps of engine charging for a 320amp-hour battery. While I'm cruising though, the boat is using 15 amps which leaves only 15 amps of engine charging. So, I may get 60 amp-hours a day of engine charging after cruising 100 nautical-miles at 25 knots.

The vast majority of our electrical needs on Channel Surfing are met with the 400 watts of solar on the roof. We go through about 110 amp-hours a day. The hot water heater will tack on another 70-90 amp-hours for any day I run it. I will usually see 100 to 180amp-hours a day from solar and get maybe 60 amp-hours a day from engine charging.

The Li3 LFP battery I installed supports up to 150 amps of charging. I can't even generate that much if I was at the dock with shorepower (+60 amp battery charger) and it was noon in July and clear blue skies (+30 amps from solar), and running my engine battery charger (+20amps) via the engine to house dc to dc charger. 110amps is the most I could generate for charging, but only at the dock. But that'd recharge the battery quick. 🙂

Great question, by the way.

External Voltage Regulator
https://www.wakespeed.com/product/ws500-advanced-alternator-regulator/
https://www.wakespeed.com/wp-conten...tron-Cerbo-GX-Setup-Guide-11.18.2022-V4-1.pdf

 

[Submariner]

ABYC (American Boat Yacht Council) just posted this on Facebook and I thought it timely for this topic.

LITHIUM ION BATTERIES – FAQ – PART 2

QUESTION: Is the overcurrent protection still required if my battery has a BMS or internal breaker?
The answer is YES. Overcurrent protection is required and its primary function is to PROTECT THE CONDUCTOR.

Battery Management System (BMS) is designed to protect a lithium ion battery or battery bank from hazardous situations such as overcharging or overdischarging, charging or discharging in high and low temperatures, etc. Even if there is an additional internal circuit breaker it is intended to protect the internal battery components, not the conductor. The battery manufacturer doesn't know the size of the conductor that would be connected to the battery and this information is necessary to correctly size the overcurrent protection that will be protecting this conductor.

Overcurrent protection is a device, such as a fuse or a circuit breaker, designed to interrupt the circuit when the current flow exceeds a predetermined value in order to protect the conductor in case of overload or a short circuit.

• The current rating of a fuse of the breaker is determined based on the size of the conductor that this device is protecting.

• Another impotent factor is the ampere interrupting capacity (AIC) of the overcurrent protection (the maximum short circuit current that an overcurrent protective device can safely interrupt). AIC rating that is required will depend on the size of the battery bank or more precisely on the short circuit rating of the battery or battery bank. If necessary, a battery bank needs to be subdivided into units such that the ampere interrupting capacity (AIC) of the overcurrent protection device is not exceeded.

For additional information please refer to ABYC E-13, LITHIUM ION BATTERIES.