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Old 17-09-2021, 17:01   #1
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Alternator burn out charging lithium

Hi,

I am new to lithium batteries and after watching a Victron video on charging lithium a low RPMs i got a little concerned about my current set up.

I have a 14v125A alternator - the max charge current my lithiums will take is 90amps but...I have two...does this make the max amps 180?

I do also have a battery isolators with two AGM banks (as well as the lithium bank) attached to it.

I am wonder if i need to install an external regulator to protect my alternator...anyone know?

Sorry if a silly question...any help would be appreciated.

Thank you
Paul
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Old 17-09-2021, 17:22   #2
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Re: Alternator burn out charging lithium

Yes, you should get an external regulator.


Have you already installed the Liths?


The reason is simple: only an external regulator, preferably with temp sensors, will allow you to dial back the AO so it doesn't burn up due to the high acceptance of Liths.


It's also true for AGMs.


You should also get rid of the isolators, which drop Voltage thru them by ).7 to 1V.


WADR, it appears you could use some reading on this subject. Try marinehow.com Is for Sale.
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Old 17-09-2021, 18:07   #3
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Re: Alternator burn out charging lithium

Thank you, and yes they have already been installed.

I'll look into installing an external regulator.

The isolator (Cristex 180-1E- 3IG ) has a low voltage drop, at max output will not exceed 0.4v according manual...however guess even <0.4v having a diode restrict my charge voltage is not idea...rather not drop any voltage

Thanks for the link, will take a look.
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Old 17-09-2021, 18:14   #4
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Re: Alternator burn out charging lithium

Hi Paul,

First off, Welcome to Cruisers Forum!

The only silly question is the one not asked.

The short answer is that an external regulator is an excellent idea, for several reasons.

LiFePO4 batteries are pretty amazing. They'll absorb pretty much all the current you throw at them. But alternators are not really designed to put out their "rated" current for very long. If you try to make them put out a lot of current for too long, they'll get too hot & burn out.

This wasn't a problem with lead/acid batteries, because their voltage would rise quickly, which would cause the alternator to cut back its current before it got too hot. But LiFePO4 voltage stays pretty much the same right up until it's full.

Also, when charging LiFePO4 batteries, you really want to see tenths of a volt. An internal regulator can only "see" the voltage at the back of the alternator. With wiring losses, battery isolators, & maybe a bit of corrosion at connectors, this is often pretty far from actual battery voltage.

To properly charge any battery quickly & safely, you want to start with the charging system pushing as much current into the battery as it can (Bulk stage), until the battery voltage reaches a certain value, which is different for each battery type, & changes with temperature for lead/acid batteries. Then it holds that voltage (Acceptance stage) until the battery is full, & then it goes down to a Float stage where it drops the voltage so essentially no current is going into the battery, but the alternator takes care of any other loads (fridge, lights, etc).

This is classic 3-stage charging that has long been recognized as the best way to charge a battery. But it's only available with external regulators. Internal regulators simply take the battery to a certain voltage (defined within the regulator & not adjustable) & holds it there. For safety reasons, this voltage is NOT the most the battery can take, it's the most that a flooded lead/acid (FLA) battery can tolerate long-term. This lower voltage means that you'll be running your engine for significantly longer to fully charge any battery.

Another problem is knowing when the battery is full. Many external regulators simply hold Acceptance for a certain length of time, typically 2-hours. This is seriously silly, as the regulator has no idea of the State of Charge (SOC) of the battery. A seriously discharged battery will need to be charged for much longer. And if you've just left the dock & your batteries are already full, then a timed system can overcharge your battery for all that time. You can kill newer high-tech batteries very quickly by overcharging them.

The best way to tell when a battery is full is to monitor the current going into the battery during the Acceptance phase. A good regulator usually does this by monitoring the shunt for your amp-hour meter (which all cruising boats should really have, as it's the best way to know the SOC of your battery). When the current going into the battery gets down to 1% of the Amp-hour capacity of the battery, then the battery is full & the system should go into Float. So, for, say, a 400Ah bank, the charger (ANY charger) should go into Float when the current required to maintain the Acceptance voltage drops down to 4A. Unfortunately, few regulators use this method.

An external regulator is designed to charge your batteries (any type) as quickly as possible, to minimize engine time, while still protecting your valuable battery/charging system. Part of that protection is to monitor the temperature of the battery (for lead/acid systems, because the Absorption voltage is temperature dependent) as well as the temperature of the alternator (for LiFePO4 systems) to keep them from getting too hot.

There are a few regulators that meet these criteria. My favorite is the WS500 from WakeSpeed (& no, I have no financial involvement here). Microprocessor controlled, presets for most battery types (as well as fully programmable profiles for us geeks), temperature probes for battery & alternator, independent leads for monitoring both battery voltage & current into the battery, CAN-bus & USB communications, & much more. It's expensive, but it's good kit.
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Old 17-09-2021, 18:23   #5
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Re: Alternator burn out charging lithium

Hi Paul, welcome aboard!

Check this site:

https://marinehowto.com/lifepo4-batteries-on-boats/

The discussion just before this posting is for lead-acid batteries.
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Old 17-09-2021, 19:33   #6
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Re: Alternator burn out charging lithium

Welcome.
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Old 17-09-2021, 20:03   #7
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Re: Alternator burn out charging lithium

Quote:
Originally Posted by Jon Hacking View Post
Hi Paul,

First off, Welcome to Cruisers Forum!

The only silly question is the one not asked.

The short answer is that an external regulator is an excellent idea, for several reasons.

LiFePO4 batteries are pretty amazing. They'll absorb pretty much all the current you throw at them. But alternators are not really designed to put out their "rated" current for very long. If you try to make them put out a lot of current for too long, they'll get too hot & burn out.

This wasn't a problem with lead/acid batteries, because their voltage would rise quickly, which would cause the alternator to cut back its current before it got too hot. But LiFePO4 voltage stays pretty much the same right up until it's full.

Also, when charging LiFePO4 batteries, you really want to see tenths of a volt. An internal regulator can only "see" the voltage at the back of the alternator. With wiring losses, battery isolators, & maybe a bit of corrosion at connectors, this is often pretty far from actual battery voltage.

To properly charge any battery quickly & safely, you want to start with the charging system pushing as much current into the battery as it can (Bulk stage), until the battery voltage reaches a certain value, which is different for each battery type, & changes with temperature for lead/acid batteries. Then it holds that voltage (Acceptance stage) until the battery is full, & then it goes down to a Float stage where it drops the voltage so essentially no current is going into the battery, but the alternator takes care of any other loads (fridge, lights, etc).

This is classic 3-stage charging that has long been recognized as the best way to charge a battery. But it's only available with external regulators. Internal regulators simply take the battery to a certain voltage (defined within the regulator & not adjustable) & holds it there. For safety reasons, this voltage is NOT the most the battery can take, it's the most that a flooded lead/acid (FLA) battery can tolerate long-term. This lower voltage means that you'll be running your engine for significantly longer to fully charge any battery.

Another problem is knowing when the battery is full. Many external regulators simply hold Acceptance for a certain length of time, typically 2-hours. This is seriously silly, as the regulator has no idea of the State of Charge (SOC) of the battery. A seriously discharged battery will need to be charged for much longer. And if you've just left the dock & your batteries are already full, then a timed system can overcharge your battery for all that time. You can kill newer high-tech batteries very quickly by overcharging them.

The best way to tell when a battery is full is to monitor the current going into the battery during the Acceptance phase. A good regulator usually does this by monitoring the shunt for your amp-hour meter (which all cruising boats should really have, as it's the best way to know the SOC of your battery). When the current going into the battery gets down to 1% of the Amp-hour capacity of the battery, then the battery is full & the system should go into Float. So, for, say, a 400Ah bank, the charger (ANY charger) should go into Float when the current required to maintain the Acceptance voltage drops down to 4A. Unfortunately, few regulators use this method.

An external regulator is designed to charge your batteries (any type) as quickly as possible, to minimize engine time, while still protecting your valuable battery/charging system. Part of that protection is to monitor the temperature of the battery (for lead/acid systems, because the Absorption voltage is temperature dependent) as well as the temperature of the alternator (for LiFePO4 systems) to keep them from getting too hot.

There are a few regulators that meet these criteria. My favorite is the WS500 from WakeSpeed (& no, I have no financial involvement here). Microprocessor controlled, presets for most battery types (as well as fully programmable profiles for us geeks), temperature probes for battery & alternator, independent leads for monitoring both battery voltage & current into the battery, CAN-bus & USB communications, & much more. It's expensive, but it's good kit.
Thank you very much. Great detail and very helpful.

I looked at the WS500 but was unsure how it would handle all three battery banks - appears only to monitor one bank. I have three banks with different charge profiles - 2AGM (crank and thruster), 1 LiFePO4. I guess I could charge one bank, then use a dc/dc charger for the other two…and toss out my battery isolator.

Do you know if there is an external regulator that would throttle back the alternator if it was getting too hot?
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Old 17-09-2021, 20:58   #8
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Re: Alternator burn out charging lithium

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Originally Posted by SV-NoBadDay View Post
Thank you very much. Great detail and very helpful.

I looked at the WS500 but was unsure how it would handle all three battery banks - appears only to monitor one bank. I have three banks with different charge profiles - 2AGM (crank and thruster), 1 LiFePO4. I guess I could charge one bank, then use a dc/dc charger for the other two…and toss out my battery isolator.

Do you know if there is an external regulator that would throttle back the alternator if it was getting too hot?
The WS500 certainly throttles back the field current to the alternator to keep it from getting too hot. Some external regs just shut the alternator down, but the WS500 anticipates the temperature rise & starts backing off the current as the alternator approaches that temperature (which you can set), in order to maximize current while preserving the alternator.

Several others do as well. You have to look at the specs to make sure they say they include an Alternator temperature probe. Almost all will have battery temperature probes, but alternator temperature probes have really only become necessary with the rise of LiFePO4.

Some of the Balmar regs monitor alternator temp. I'm not a big fan of Balmar, as it seems that most (all?) of their external regulators employ a time component somewhere, & they often don't actually monitor current into the battery, preferring to infer that current from how much the alternator is producing, which is very sub-optimal. But I've never owned one, so I could be wrong. (We use Very Smart Regulators, or VSRs, predecessors to the WS500)

I don't know of any external regulator that will handle multiple battery banks. They can't, really. How would they direct current to one bank & not another?

This problem is well known, however, & there are multiple ways to handle it, usually involving DC/DC chargers. These are small electronic components that act as chargers for your secondary batteries, charging them from your primary.

In your case, you'll probably want a pair of AGM DC/DC chargers, one for your start battery & one for your thruster. Some of these have multiple charge profiles built in, & you select one. Others you buy with the correct profile for your battery. This would also let you throw out your battery combiners.

You're not using either of those batteries for very long, so you're not taking many Ah out of either of them, so your DC/DC chargers don't have to be very big.

They also don't have any external sensors at all AFAIK (voltage, current, temp). Most only measure the voltage of the battery through their charging leads, & that charging current introduces distortions, so they're not optimal chargers, but they're good enough. Since those batteries are at rest when you're not starting or thrusting, you only want trickle charging anyway. Just mount those DC/DC chargers close to the batteries (to minimize measurement inaccuracies) & make sure the chargers turn off when they're done, so you don't drain your primary battery.
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Old 17-09-2021, 20:59   #9
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Re: Alternator burn out charging lithium

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Originally Posted by SV-NoBadDay View Post
..............
.......................................


Do you know if there is an external regulator that would throttle back the alternator if it was getting too hot?

Balmar regulators have inputs for alternator temp sensors. Please consider this as an automatic backup failsafe if the settings you implement don't keep the AO low enough to keep it cool.

You can read all about external regulators at www.balmar.net Download the MC-614 manual, you will learn a lot about how they work and how to install one.


Maine Sail's website has a How to Program article, too.


I admire Jon for writing some very well presented summaries of important issues. Nice job.


This part is, however, needs some clarity



Quote:
An internal regulator can only "see" the voltage at the back of the alternator. With wiring losses, battery isolators, & maybe a bit of corrosion at connectors, this is often pretty far from actual battery voltage.

Correct about internal regulators. The advantage of an external regulator is that there is an input called battery sense that can, and should, take a wire from the batteries, not the back of the alternator (AO) and use the real battery voltage to adjust output. But still, an even better reason to diss your isolators, 'cuz when you sense the batteries, then the AO is deficient when it gets there with voltage drops however small you may think they are.


Remember, full vs empty batteries is 12.8 vs. 11.8 i.e. ONE volt.

0.4 of one volt is 40%!
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Old 17-09-2021, 23:30   #10
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Re: Alternator burn out charging lithium

Your isolator is probably helping the alternator keep from burning out at the moment, if you have an internal regulator and no voltage monitoring circuit direct to the battery, as the extra voltage drop will be causing the regulator to wind back the alternator output.
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Old 18-09-2021, 07:16   #11
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Re: Alternator burn out charging lithium

Thank you very much for all the inputs. Sounds like i have a little reading to do over the winter to design a system with an external regulator and chuck that battery isolator.

Again very much appreciated

Regards
Paul
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Old 18-09-2021, 08:07   #12
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Re: Alternator burn out charging lithium

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Your isolator is probably helping the alternator keep from burning out at the moment, if you have an internal regulator and no voltage monitoring circuit direct to the battery, as the extra voltage drop will be causing the regulator to wind back the alternator output.

WADR, huh?!?


The internal regulator measures the V at the back of the alternator, and is preset, usually not adjustable. So, let's say it is set for 14.2V.


The AO goes out and to an isolator that drops let's say 0.7V. 14.2 minus 0.7 = 13.5V.


That's the highest V that can get to the batteries (neglecting voltage drop completely ford this discussion).


All that will happen is that the batteries will be woefully undercharged, and NOT "causing the regulator to wind back the alternator output." That will simply not happen, it is not how it works.
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Old 18-09-2021, 08:08   #13
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Re: Alternator burn out charging lithium

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Originally Posted by SV-NoBadDay View Post
Thank you very much for all the inputs. Sounds like i have a little reading to do over the winter to design a system with an external regulator and chuck that battery isolator.

Again very much appreciated

Regards
Paul

Paul, you are aware that there is a very looong and helpful thread in this very forum about this subject?
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Old 18-09-2021, 08:19   #14
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Re: Alternator burn out charging lithium

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Paul, you are aware that there is a very looong and helpful thread in this very forum about this subject?
Hi Stu, no sorry i didn't look. Would you have a link or the title for me to search for it?

Paul
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Old 18-09-2021, 08:43   #15
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Re: Alternator burn out charging lithium

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WADR, huh?!?


The internal regulator measures the V at the back of the alternator, and is preset, usually not adjustable. So, let's say it is set for 14.2V.


The AO goes out and to an isolator that drops let's say 0.7V. 14.2 minus 0.7 = 13.5V.


That's the highest V that can get to the batteries (neglecting voltage drop completely ford this discussion).


All that will happen is that the batteries will be woefully undercharged, and NOT "causing the regulator to wind back the alternator output." That will simply not happen, it is not how it works.

Stu - I try to keep up with most of the acronyms, but WADR???

WTH? (what the heck)
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