How quickly do lithium batteries charge off the alternator?

[bman5150]

None are adjustable, most are set to 14.2 to 14.6 max, The lithium battery will accept all the current that is availble without cutting back on charge rate until it is fully charged. For instance, my 2 stroke has a 50 amp alternator, the requires 20 amps to function. at cruising speeds, I have constant 29 amps going into my battery which will replenish it quite fast. Lead acid batteries have a much higher internal resistance, and the current flow will rapidly fall from say 25 to around 10 amps or less going into the battery in just a few minutes,
At idle alternator ouput is very low, most of is needed just to run the motor, allmost nothing left to feed the battery

I wondered if alternator output would be pretty low at idle. So my idea of letting my big motor idle for 15 minutes while I eat lunch or fish wouldn’t really charge the battery much at all. Instead, it sounds like I’d need to make. 10-15 minute run.

in nearly all of my fishing situations, I usually do make at least a few runs each day. However, there are some situations where I barely use the big motor or don’t use it at all. Looks like I’m going to just have to suck it up and get a lithium with more AHs to account for these scenarios.

[lpugh]

Personal test I did: Battery was down to 89%, in a 15-minute run a various speed to another location, the battery was back to 99%, the entire time the app showed 28 to 29 amps going into the battery. This was with a 50-amp alternator, the motor requires 20 of those 50 amps.

[rid 05 198]

Personal test I did: Battery was down to 89%, in a 15-minute run a various speed to another location, the battery was back to 99%, the entire time the app showed 28 to 29 amps going into the battery. This was with a 50-amp alternator, the motor requires 20 of those 50 amps.

[bman5150]

@lpugh - thank you for sharing that info.

[CJ1]

In theory any voltage above the resting voltage should fully charge a battery. It is just going to take a while.

Playing with a variable voltage power supply and charging my small Ionics battery at 13.5 volts, it will go to 100% SOC.

The individual cell voltage was and is never exactly the same. A few millivolts difference. Not sure what the maximum cell difference can be before the cells are considered to be out of balance.

This is what I am seeing also. When I get more experience with them (mostly need time!) I'll post what I find. I truly believe anything in the 13.9 and up range will fully charge and balance a good lithium battery. Cj

[bobcoy]

I am not getting that deep into it, but it seems 14.4 comes up quite a bit when talking balancing cells. JMO Bob

[78Staff]

Personal test I did: Battery was down to 89%, in a 15-minute run a various speed to another location, the battery was back to 99%, the entire time the app showed 28 to 29 amps going into the battery. This was with a 50-amp alternator, the motor requires 20 of those 50 amps.

Mirrors what I saw with my 2016 SHO - bascially pushing out 29amps (to battery) at running speed, and dropping back to single digits at idle speeds.

[MTW]

Personal test I did: Battery was down to 89%, in a 15-minute run a various speed to another location, the battery was back to 99%, the entire time the app showed 28 to 29 amps going into the battery. This was with a 50-amp alternator, the motor requires 20 of those 50 amps.

so the altenator doesnt provide enough voltage to top it off at 100%? is that what effectively what keeps the BMS overcharging cutoff from engaging?

[lpugh]

so the altenator doesnt provide enough voltage to top it off at 100%? is that what effectively what keeps the BMS overcharging cutoff from engaging?

it will charge it to 100% with enough run time. The alternator regulator controls voltage to 14.4 to 14.6 volts, it also regulates current flow as the battery voltage comes up to its peak it will reduce current flow as well, BMS will not switch off if regulator is doing its job.
This is why manufactures do not recomend lithium batteries across the board yet.
If the BMS turns off while running the pcm will shut down the motor because the voltage will spike very high, 20 to 60 volts. Possible PCM failure when this happens, hooking the boat or worse!

[yam911]

so the altenator doesnt provide enough voltage to top it off at 100%? is that what effectively what keeps the BMS overcharging cutoff from engaging?

It is not voltage that tops off a battery at 100% SOC. It is current.

Current flow depends in part on the voltage. Less voltage simply means less current flow which means a bit longer to reach 100% SOC.

[yam911]

Helps at times to think of voltage as pressure. Say fuel pressure from a fuel pump. The higher the fuel pressure the faster gasoline will be flowing. The faster the fuel flow the more quickly a gas tank will reach 100% full.

[MTW]

it will charge it to 100% with enough run time. The alternator regulator controls voltage to 14.4 to 14.6 volts, it also regulates current flow as the battery voltage comes up to its peak it will reduce current flow as well, BMS will not switch off if regulator is doing its job.
This is why manufactures do not recomend lithium batteries across the board yet.
If the BMS turns off while running the pcm will shut down the motor because the voltage will spike very high, 20 to 60 volts. Possible PCM failure when this happens, hooking the boat or worse!

yeah thats why i ask because someone asked me about their set up with a 250 pro xs was seeing his voltages spike to around 24v sporadically. his units even gave a high voltage alarm. his charging system checked out and the only thing i could think the BMS was disconnecting. i told him to call lithiumhub and talk to their engineers because nothing was wrong with his units.

[MTW]

It is not voltage that tops off a battery at 100% SOC. It is current.

Current flow depends in part on the voltage. Less voltage simply means less current flow which means a bit longer to reach 100% SOC.

which is what i meant voltage at full throttle. i dumb down sometimes so folks can understand. i have a BSEE from UT knoxville and enough electronic certs to wallpaper my bathroom.