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03-02-2025, 14:39
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#91
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Marine Service Provider
Join Date: Oct 2020
Location: Ft Lauderdale
Boat: Bertram 28 FBC
Posts: 15
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Re: The external regulator we've all been waiting for!
This is still on my list of products that I need to try. The system that I have now is far too complex and I now have to replace the BCM as the screen now has dead spots, luckily I have a new spare for now but this approach seems far more practical for me. the current system that I'm using doesn't have an adjustment to control output based on RPM
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03-02-2025, 17:31
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#92
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Registered User
Join Date: Nov 2018
Location: San Diego
Boat: Shannon 50 Ketch
Posts: 744
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Re: The external regulator we've all been waiting for!
Quote:
Originally Posted by Dockhead
If the regulator is programmed to support a float level voltage which is higher than the open circuit voltage of the battery bank, then the alternator will indeed support house loads, no?
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Not on my system using the SOC% relay to kill the regulator's ignition wire voltage. It can't float anything if the voltage regulator has no power because the SOC% relay shut it off.
I was only addressing how my setup works.
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04-02-2025, 04:44
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#93
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Moderator

Join Date: Mar 2009
Location: Denmark (Winter), Cruising North Sea and Baltic (Summer)
Boat: Cutter-Rigged Moody 54
Posts: 35,223
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Re: The external regulator we've all been waiting for!
Quote:
Originally Posted by jordanbigel
Not on my system using the SOC% relay to kill the regulator's ignition wire voltage. It can't float anything if the voltage regulator has no power because the SOC% relay shut it off.
I was only addressing how my setup works.
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Understood. I believe I will program my regulator to keep the alternator working at float voltage (less than the voltage which would add charge to full batteries), to run the loads when the main engine is running rather than pulling the batteries down. I believe that's the default lithium configuration for most regulators.
For the Balmar M624 (what I have), the default program for lithium has float voltage of 26.8V, but can be customized.
__________________
"You sea! I resign myself to you also . . . . I guess what you mean,
I behold from the beach your crooked inviting fingers,
I believe you refuse to go back without feeling of me;
We must have a turn together . . . . I undress . . . . hurry me out of sight of the land,
Cushion me soft . . . . rock me in billowy drowse,
Dash me with amorous wet . . . . I can repay you."
Walt Whitman
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04-02-2025, 06:41
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#94
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Registered User
Join Date: Jun 2019
Location: Rochester, NY
Boat: Chris Craft 381 Catalina
Posts: 6,954
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Re: The external regulator we've all been waiting for!
Quote:
Originally Posted by Dockhead
Understood. I believe I will program my regulator to keep the alternator working at float voltage (less than the voltage which would add charge to full batteries), to run the loads when the main engine is running rather than pulling the batteries down. I believe that's the default lithium configuration for most regulators.
For the Balmar M624 (what I have), the default program for lithium has float voltage of 26.8V, but can be customized.
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That's the logical way to do it in my mind. I'd rather have the alternator float the batteries at a voltage that keeps them 95 - 99% charged (so something like 13.4 / 26.8V) rather than letting them cycle down to, say, 75% before charging again. The float solution means that after a long motoring period I can count on arriving with the batteries at, say, 95%. The other solution means that depending on where I am in the cycle, I could potentially arrive with the batteries only 80% charged, having wasted some power production opportunity.
For those who disagree, keep in mind that if you have to produce power from fossil fuel at any point, once you factor in fuel and maintenance, power from an alternator on the main engine(s) while already motoring is the cheapest power you'll get. A well loaded genset can match it in terms of fuel in vs power out, but it's still more maintenance cost compared to slightly increasing the load on an engine that's going to be running anyway.
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05-02-2025, 09:17
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#95
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Registered User
Join Date: Jun 2009
Location: Annapolis, MD
Boat: Sabre 34-1 (sold) and Saga 43
Posts: 2,777
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Re: The external regulator we've all been waiting for!
This issue of what to do at 100% is a challenge. When actually living on the boat, getting to 100% and holding at something over 95% is very useful. For those of us that aren't full time on the boat, it's a challenge.
* My solar can product far more than my daily in-port-not-on-boat loads (the fridge, basically). As a result, uncontrolled charging results in the battery rarely being below 90% SOC.
* In the winter, it is far worse. My daily loads are about zero (bilge pump in rains?). The battery spends all its time at 99.9% SOC.
LFP likes to be below 90%, preferably below 70%. That's a bad solution to cruising, of course. Leaving it on float above 99% is potentially harmful, as "float" is typically above a voltage that the LFP likes to be at (3.35V => 13.4V is probably an OK level). Anything above that can be bad.
I can solve the winter problem by simply pushing the "disable all charge" switch and check it once a month or so. When SOC gets to 40%, do a charge to 70%. Pretty easy, since the boat is in my front yard.
The summer-idle is vastly harder. The fridge can wipe the battery slick in under a week, so it can't be ignored (turn off charging and forget about it). My BMS has a setting to restart charging after dropping to a setpoint, factory default of 3.4V =>13.6. Voltage is hard to use, I'd prefer it to be SOC -- then I'd set it at 85 or 90%, and so would never have it below 85% (to your point about arriving in port too low). I'm planning on setting it at 3.3V=>13.2V, which is about 70%, and then play with it to find a sweet spot that meets the battery needs while also not stressing me on SOC anxiety. The problem with using volts is that 3.3 is about 70%, and 3.4 is about 99% -- that's a tenth of a volt between 70% and 99%! One trick that my help if I want to kick start it is to turn on the inverter to a big load for a few minutes -- LFP doesn't drop like AGM but it does drop, and that may get it to slide from 3.35 to 3.30 and restart charging.
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05-02-2025, 12:18
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#96
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Registered User
Join Date: Sep 2008
Location: Auckland, NZ
Boat: Hood 38 - Wauquiez
Posts: 758
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Re: The external regulator we've all been waiting for!
Have I created a network loop here?
Ie I only need one path to N2K?
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Yesterday, 05:57
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#97
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Moderator

Join Date: Mar 2009
Location: Denmark (Winter), Cruising North Sea and Baltic (Summer)
Boat: Cutter-Rigged Moody 54
Posts: 35,223
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Re: The external regulator we've all been waiting for!
Quote:
Originally Posted by sailingharry
This issue of what to do at 100% is a challenge. When actually living on the boat, getting to 100% and holding at something over 95% is very useful. For those of us that aren't full time on the boat, it's a challenge.
* My solar can product far more than my daily in-port-not-on-boat loads (the fridge, basically). As a result, uncontrolled charging results in the battery rarely being below 90% SOC.
* In the winter, it is far worse. My daily loads are about zero (bilge pump in rains?). The battery spends all its time at 99.9% SOC.
LFP likes to be below 90%, preferably below 70%. That's a bad solution to cruising, of course. Leaving it on float above 99% is potentially harmful, as "float" is typically above a voltage that the LFP likes to be at (3.35V => 13.4V is probably an OK level). Anything above that can be bad.
I can solve the winter problem by simply pushing the "disable all charge" switch and check it once a month or so. When SOC gets to 40%, do a charge to 70%. Pretty easy, since the boat is in my front yard.
The summer-idle is vastly harder. The fridge can wipe the battery slick in under a week, so it can't be ignored (turn off charging and forget about it). My BMS has a setting to restart charging after dropping to a setpoint, factory default of 3.4V =>13.6. Voltage is hard to use, I'd prefer it to be SOC -- then I'd set it at 85 or 90%, and so would never have it below 85% (to your point about arriving in port too low). I'm planning on setting it at 3.3V=>13.2V, which is about 70%, and then play with it to find a sweet spot that meets the battery needs while also not stressing me on SOC anxiety. The problem with using volts is that 3.3 is about 70%, and 3.4 is about 99% -- that's a tenth of a volt between 70% and 99%! One trick that my help if I want to kick start it is to turn on the inverter to a big load for a few minutes -- LFP doesn't drop like AGM but it does drop, and that may get it to slide from 3.35 to 3.30 and restart charging.
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This is a real conundrum.
You can't have an automatic system to choose what state of charge to hold the batts at, because the computer can't know your plans. If you're at the dock for days or weeks, you'd rather have your batts at 40% to 60% and leave them there. If you're getting ready to go for a long sail, you would like to bring them up to 100%.
It would be good to have a switch to choose between "Fully charge batteries when possible" and "leave the batteries at 40% to 60% SOC".
Although, it might also be an academic question, since none of us will live long enough, probably, to wear out a set of LiFePo4 batteries by cycling them. It might be rational just to charge them to 100% and forget about it, except when you're off the boat, when you might disconnect and isolate them entirely.
__________________
"You sea! I resign myself to you also . . . . I guess what you mean,
I behold from the beach your crooked inviting fingers,
I believe you refuse to go back without feeling of me;
We must have a turn together . . . . I undress . . . . hurry me out of sight of the land,
Cushion me soft . . . . rock me in billowy drowse,
Dash me with amorous wet . . . . I can repay you."
Walt Whitman
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Yesterday, 06:27
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#98
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Senior Cruiser

Join Date: Sep 2014
Location: puget sound washington
Boat: 1968 Islander bahama 24 hull 182, 1963 columbia 29 defender. hull # 60
Posts: 13,087
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Re: The external regulator we've all been waiting for!
Quote:
Originally Posted by Dockhead
Although, it might also be an academic question, since none of us will live long enough, probably, to wear out a set of LiFePo4 batteries by cycling them. It might be rational just to charge them to 100% and forget about it, except when you're off the boat, when you might disconnect and isolate them entirely.
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Speak for yourself  I'm only 60 and my bank is already 5 . I plan to wear them out before I go
__________________
Non illigitamus carborundum
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Yesterday, 07:02
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#99
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Registered User
Join Date: Jun 2019
Location: Rochester, NY
Boat: Chris Craft 381 Catalina
Posts: 6,954
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Re: The external regulator we've all been waiting for!
Quote:
Originally Posted by Dockhead
This is a real conundrum.
You can't have an automatic system to choose what state of charge to hold the batts at, because the computer can't know your plans. If you're at the dock for days or weeks, you'd rather have your batts at 40% to 60% and leave them there. If you're getting ready to go for a long sail, you would like to bring them up to 100%.
It would be good to have a switch to choose between "Fully charge batteries when possible" and "leave the batteries at 40% to 60% SOC".
Although, it might also be an academic question, since none of us will live long enough, probably, to wear out a set of LiFePo4 batteries by cycling them. It might be rational just to charge them to 100% and forget about it, except when you're off the boat, when you might disconnect and isolate them entirely.
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When I convert, my tentative plan is to make use of the Victron solar/wind priority feature so they get at least lightly cycled when the boat is at the dock (rather than just being held full at 13.4 - 13.5 volts). If the boat is going to be un-used for a while, I'd probably just set the DVCC max charge voltage to 13.2 or so, allowing them to sit partially charged without having to power anything down.
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Yesterday, 13:36
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#100
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Registered User
Join Date: Feb 2011
Location: Meandering about the Gulf of Alaska coast [NNE Pacific]— where the internet doesn't always shine... [Even Elon's...] Homeport: Wrangell Island
Boat: Nauticat 43 [S&S Staysail Ketch]
Posts: 1,797
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Re: The external regulator we've all been waiting for!
Quote:
Originally Posted by Dockhead
This is a real conundrum.
You can't have an automatic system to choose what state of charge to hold the batts at, because the computer can't know your plans. If you're at the dock for days or weeks, you'd rather have your batts at 40% to 60% and leave them there. If you're getting ready to go for a long sail, you would like to bring them up to 100%.
It would be good to have a switch to choose between "Fully charge batteries when possible" and "leave the batteries at 40% to 60% SOC".
Although, it might also be an academic question, since none of us will live long enough, probably, to wear out a set of LiFePo4 batteries by cycling them. It might be rational just to charge them to 100% and forget about it, except when you're off the boat, when you might disconnect and isolate them entirely.
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Hi DH,
Does your BMS [or other external control e.g., Victron GX device, etc.] allow you to set max SoC% in prep for a storage situation? Or is there a method for automatically bleeding off a few Amp-hours in case an LFP achieves a high SoC during storage for any reason?
I ask because I have both capabilities, but I am only familiar with the [internal] BMS options on the LFP batteries I am in the process of installing. But I wonder if most other BMSs have similar options as relate to setting a lower LFP SoC when in ‘storage mode’?
Overview:
I am still learning about my first LFP integration [four parallel (initially) SFK 300HP 12Vdc 300Ah; EVE LF-304 cells], and still in the process of bench testing/refining settings and relay/ GX logic.
I am sharing some of the SoC control options available in my system in case any apply to other BMS/ Victron GX systems I am unfamiliar with.
First, the Bluetooth app that came with my batteries currently allows me to set max SoC between 80-100% in 5% increments for each individual battery. [And I can set all 4 batteries at once on the Cerbo; 80% meets this battery manufacturer’s higher limit storage recommendations.]
Cerbo control: For granular, centralized control, the vendor provides a driver for Victron Venus OS for GX devices [Cerbo GX Mk2 in my case.] This allows full duplex integration with up to 8 batteries [currently I have 4.] On a GX device the batteries display- and are configurable- both as aggregated [virtual battery bank] and individual batteries. [I see 5 items in the battery list on the Cerbo: 1 bank; 4 individual batteries.]
In the Cerbo [or any GX control device- including Raspberry PI] SoC limits can be set for all batteries at once in the aggregated [virtual battery] or in each battery individually. [Likewise for all other settings the BMSs and Cerbo allow- and since it can also update BMS firmware via the Cerbo- it is my primary control hub of choice, with the BT app secondary.]
Another failsafe option: A feature SFK just added to their latest GX driver [which was released simultaneously with the recent Venus OS 3.54 update] includes the user configurable capability to slightly lower SoC automatically- per battery- by gently cycling the built-in heating pads. [Time delay before initiation, SoC%, and max battery temperature are set by the user within conservative parameters set by manufacturer.] This function was developed mainly to facilitate a poor person’s approach to balancing series wired batteries within a bank.
While preventing a high SoC during storage is preferred, I may use this as a fail-safe in case of an unlikely failure of the BMSs, Victron MPPT solar controllers, and all the other safeguards while absent from the boat.
The above heating pad SoC bleed-off is likely a battery/BMS specific feature, but one could mimic this storage mode failsafe logic by programming a control device [e.g., Cerbo] to activate a fan/light/ other useful light load dump circuit via relay when the batts hit the max setting of a user configurable SoC% range.
Attempting to stay within scope of your stated conundrum, these are just a couple of the quick and dirty tools available that I am aware of within my LFP ecosystem to help avoid a high SoC during LFP battery ‘storage’ periods [ignoring adjusting charge source settings to lower ‘storage’ voltages, etc.]
In case any of this is of interest and similar to what may available within your system- or may spawn even better ideas…
Cheers, Bill
__________________
SV Denali Rose
Learning every day- and sharing if I can.
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Yesterday, 17:01
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#101
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Registered User
Join Date: Apr 2016
Location: SE Asia, for now
Boat: Outremer 55L
Posts: 4,161
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Re: The external regulator we've all been waiting for!
Well, some BMS do allow for multiple charge profiles, so you can have one for passages (keep everything charged up), one for sunny cruising locales (allow to cycle lower, say 30%, since solar will charge it back up reliably), another for storage that cycles between 40% and 55%, etc.
That said, setting your alternators to float at less than charging voltage is a good idea, but it needs to be well below 13.4V. 13.2V will never fully charge an LFP battery and is a safe voltage even if motoring for extended periods - it roughly corresponds to the middle of the flat voltage range.
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Yesterday, 20:37
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#102
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Registered User
Join Date: May 2006
Posts: 1,442
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Re: The external regulator we've all been waiting for!
That’s all ok if you want to play around with your alternators float sweetspot to keep your batteries nearly full while motoring, but as you all see, it’s not so easy.
So think about this…
Let’s say you have a 560ah bank because that’s what you need and you need to come into the next remote bay fully charged. So all the above comments apply about arriving fully charged as if you don’t, you might just be compromised if you stay for an extended time.
The solution is to add a 3rd bank so you have 3x 280 =840 ah and just change your thinking to not caring about state of charge and instead put back what you took out and keep it above 60%.
Another advantage is that it adds redundancy… imagine if your nicely usage balanced 560ah system suddenly became a 280ah system for some reason when you are far from spares…
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Today, 02:12
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#103
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Moderator

Join Date: Mar 2009
Location: Denmark (Winter), Cruising North Sea and Baltic (Summer)
Boat: Cutter-Rigged Moody 54
Posts: 35,223
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Re: The external regulator we've all been waiting for!
Quote:
Originally Posted by rslifkin
When I convert, my tentative plan is to make use of the Victron solar/wind priority feature so they get at least lightly cycled when the boat is at the dock (rather than just being held full at 13.4 - 13.5 volts). If the boat is going to be un-used for a while, I'd probably just set the DVCC max charge voltage to 13.2 or so, allowing them to sit partially charged without having to power anything down.
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Why would you want to cycle them at all? Cycling is what wears them out. Albeit very slowly.
__________________
"You sea! I resign myself to you also . . . . I guess what you mean,
I behold from the beach your crooked inviting fingers,
I believe you refuse to go back without feeling of me;
We must have a turn together . . . . I undress . . . . hurry me out of sight of the land,
Cushion me soft . . . . rock me in billowy drowse,
Dash me with amorous wet . . . . I can repay you."
Walt Whitman
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Today, 04:25
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#104
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Registered User
Join Date: Apr 2016
Location: SE Asia, for now
Boat: Outremer 55L
Posts: 4,161
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Re: The external regulator we've all been waiting for!
Quote:
Originally Posted by Dockhead
Why would you want to cycle them at all? Cycling is what wears them out. Albeit very slowly.
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Bouncing between 45% and 55% is not cycling, until you’ve done 10 or so of them to equal one cycle. It’ll take a fair few years to approach 10k cycles and go, darn, I lost 3K additional cycles. After 4 years of full time live aboard and frequent BMS charge stops to allow them to discharge to below 20%, we're barely above 400 cycles!
Two storage strategies depend on what is left running while in storage. If nothing, and especially if on the hard, disconnect the batteries after they’ve been discharged to 12.8V. If on the water, and especially if you have left loads like fridge and freezer running, small cycling around 50% is better than a continuous low voltage charge current. And if stored in the water, consider what will power your bilge pumps and any remote monitoring system you have.
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Today, 05:45
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#105
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Moderator

Join Date: Mar 2009
Location: Denmark (Winter), Cruising North Sea and Baltic (Summer)
Boat: Cutter-Rigged Moody 54
Posts: 35,223
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Re: The external regulator we've all been waiting for!
Quote:
Originally Posted by newhaul
Speak for yourself  I'm only 60 and my bank is already 5 . I plan to wear them out before I go 
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Lucky you.
But 6000 cycles (and a "cycle" is 0 to 100%; 25 to 75 is only half a cycle) is 38 years, if you do a full cycle THREE TIMES A WEEK, which is a half cycle almost every day, 365 days a year.
I sail at most 4 months a year, and am not on battery power the whole time, so I will certainly never cycle out my batteries.
So it may just not make any sense to worry about this, and just charge them to a 100% and forget about it.
Or maybe derate the battery pack to 90% or something and live without the extra 10%.
Or maybe have normally charging stop at 80%, and have a setting to allow you to go to 100% when you need the capacity.
Or maybe really just not over think this.
__________________
"You sea! I resign myself to you also . . . . I guess what you mean,
I behold from the beach your crooked inviting fingers,
I believe you refuse to go back without feeling of me;
We must have a turn together . . . . I undress . . . . hurry me out of sight of the land,
Cushion me soft . . . . rock me in billowy drowse,
Dash me with amorous wet . . . . I can repay you."
Walt Whitman
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