How quickly do lithium batteries charge off the alternator?

[bman5150]

I’ve read that lithium batteries charge up very quickly and even get noticeable charge boosts when running the big motor. How long are we talking? How long of a boat run (time) to charge the battery, say 10% more than where it started?

I want to factor this in as I decide what battery I get as far as Amp Hours.

thx

[DREWTICK]

depends on amps going in and out during the time you are running, the Proxs 200 can charge very fast and you could see as much as 60 to 70 amps going into the battery when running , that will depend on how many graphs are running at the time and using up some of the amps from the alternator, many people running a Merc 4 stroke and a 125ah that move around a lot find that their battery stays 80 to 90% all day, others running 5 graphs and FFS that start on the trolling motor all day need more than 125ah

[bobcoy]

As Drew says “it depends”. I say get a bit more than you think you will need. It is penny wise to scrimp a bit on capacity, but in the long run your battery will thank you in years of service by not draining as much you will add to its life and the lack of worry on your part might benefit your longevity as well. Bob

[bman5150]

Do you guys know if a Merc 4-stroke PROXS 200 will put out a bunch of juice even when idling? I could see just starting the motor and letting it idle for 15 minutes if that was going to charge up the battery significantly. I fish some TM-only places all day, dawn to dusk so I’m guessing I should just get a bigger battery though.

[goodman_fishing]

Do you guys know if a Merc 4-stroke PROXS 200 will put out a bunch of juice even when idling? I could see just starting the motor and letting it idle for 15 minutes if that was going to charge up the battery significantly. I fish some TM-only places all day, dawn to dusk so I’m guessing I should just get a bigger battery though.

Would you be allowed to fire up and idle on "TM-only" places anyway? Seems like that would go against their rules?

[bman5150]

I wasn’t clear in my previous statement. I fish some TM-only lakes and would need to fish dawn to dusk and not complete drain my starter battery since that’s what I would be running my HDS Live 9”, ActiveTarget 2 transducer and HDS Live 12”. I’d also have my console HDS Live 9” but that one would be on standby all day. For these lakes, I wouldn’t be running anything else though (no live wells, etc.)

I also fish some smaller lakes that are idle-only. That’s one situation where I could potentially get some charge back into my batteries if I fished dawn to dusk.

lastly, I fish some bigger waters where I might only make one big run to a particular area and then I’m on the TM the rest of the day. Might make 1-2 more shorter runs before ending the day. Again, if I was fishing in my area and the juice got low, I’m wondering if I could just start the motor and have it idle for 15 minutes to help get some charge into the starter battery.

[DREWTICK]

you can run 2 HDS 9s and a 12 with At2 12+ hours on any quality 120ah to 125ah dual purpose lithium and still start that 200 at the end of the day, any idle time will just add to that

[billnorman1]

I’ve read that lithium batteries charge up very quickly and even get noticeable charge boosts when running the big motor. How long are we talking? How long of a boat run (time) to charge the battery, say 10% more than where it started?

I want to factor this in as I decide what battery I get as far as Amp Hours.

thx

Your battery will take all the amps your system will deliver if it's low. Lithium batteries have a higher voltage than conventional batteries so that can make a difference too. If your regulator is set to the voltage a lead-acid battery needs it might not fully charge a Lithium battery. Experience will tell you.

[yam911]

What model motors have voltage regulators with adjustable outputs?

[78Staff]

My 125ah always seemd to have power to spare, but did some tests this winter running "full tilt" with 4 MFU's, AT, 3DSS, Go Pros, Radio, PP's, etc & my "common" amp draw with livewells running is 14ah... so I'm concerned about getting a full/long day out of it. Now, it's not like I am going to sit in one spot all day and never run the big motor, but still I am thinking about supplementing it with an additonal Ionic in Parallel. Just haven't decided if adding a 50 is enough, or if I should go full out with another 100 or 125ah even.

[billnorman1]

What model motors have voltage regulators with adjustable outputs?

None that I know of but the system has a preset design voltage. It might be excellent for lead acid but not quite enough to hit 100% on a Lithium.

[goodman_fishing]

None that I know of but the system has a preset design voltage. It might be excellent for lead acid but not quite enough to hit 100% on a Lithium.

Most I have seen are in the 14.5v range, pretty good for either chemistry.

[billnorman1]

Most I have seen are in the 14.5v range, pretty good for either chemistry.

Well I'm not sure of the exact charging profile, so I bought Lithium rated chargers for my leaky old scow.

[CJ1]

Most I have seen are in the 14.5v range, pretty good for either chemistry.

What from your experience is the minimum voltage to achieve a full charge. I know most say 14.6 is optimum but what is your experience for the min. There has to be a rough minimum. I do know that 14v will charge the ones I have to 90+% as my Lithium chargers add very little to top them off. I also wonder what would be the min voltage to balance the cells also? CJ

[PMantle]

Since getting my fusible link replaced on my Merc, I have not had to charge my 125 once. Actually thinking about replacing my 3 bank with a 2 bank just for the TM batteries. Running three 9" graphs plus Livescope in small lakes.

[yam911]

What from your experience is the minimum voltage to achieve a full charge. I know most say 14.6 is optimum but what is your experience for the min. There has to be a rough minimum. I do know that 14v will charge the ones I have to 90+% as my Lithium chargers add very little to top them off. I also wonder what would be the min voltage to balance the cells also? CJ

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.

[rid 05 198]

I’ve read that lithium batteries charge up very quickly and even get noticeable charge boosts when running the big motor. How long are we talking? How long of a boat run (time) to charge the battery, say 10% more than where it started?

I want to factor this in as I decide what battery I get as far as Amp Hours.

thx

So 10% more than where it started? 10% of a 120 amp battery is 12 amps. So if the alternator is putting out 60 amps, you will get your 10% in 12 minutes..? Will check that.

[SLYDoggie]

Let's give the math a shot for a 125 Amp Lithium Cranking Battery, a motor that charges at 50 Amps, and fishing electronics that consume 20 Amps, and your battery is currently at 30% (37.5 Amps). The thing to keep in mind is that the alternator and fishing electronics are Amps/Hour. In other words, in one hour the motor will supply 50 Amps of charging and in one hour the Fishing electronics will consume 20 Amps.

I'm going to assume a perfect world and that everything is performing exactly as specified, but this may or may not be the case:

The battery is currently at 37.5 Amps, so let's see where the battery will be in 1 hour with the big motor and the fishing electronics all in use. In one hour, you would have a net of 30 Amps added to the battery (50 charging less 20 discharge = 30 net Amps). Add the 30 Amps to the starting 37.5 Amps and you now have 67.5 Amps. This raises the battery percentage from 30% (37.5 Amps) to 54% (67.5 Amps).

You can see from the above that it takes a while to get any significant net charging to the battery. You can easily do the above with your specific Battery/Alternator/Electronics Amp numbers.

[rid 05 198]

So for his 10% more than where it started, a motor at 50 Amps and with electronics on, ballpark, he will get his 10% in 25 minutes. Ya it pays to turn off electronics if you can.

[lpugh]

What model motors have voltage regulators with adjustable outputs?

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