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Old 08-05-2019, 00:04   #1
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Do I need an alternator protection device when switching to Lithium?

Iím in the middle o switching to llifepo4 batteries and have a question. I plan to keep my lead starter battery and hook up the lithium as service bank. I have on of those normal load regulators that switch the alternator charging first to the start battery and then when it reach a certain voltage over to the service bank. Normal setup on a production boat. Now my new BMS will cut the charging with a relay at some voltage to protect the lithium bank. My question is what happens then with the current from the alternator? Does
it:
1. Switch over and charge the start again even though itís ďfullyĒ loaded
2. Burns up in flames (or at least burn the diode) since thereís no load

If no2 I guess I need something like the sterling pro arc
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Old 08-05-2019, 02:40   #2
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Re: Do I need an alternator protection device when switching to Lithium?

Simpler is better.

By "service" I guess you mean House bank, some used to say "auxiliary" as opposed to Starter, aka primary / engine / essentials.

There is no need to "prioritize" direct charging to Starter batt first, that's a marketing gimmick, Sterling being a leader in that.

Just put a lead batt direct inline with alt output all the time, if that's Starter fine. What is "normal", a simple VSR closes the connection to House based on voltage being above a setpoint, does not "switch between" the two circuits.

So if (when) a HVC isolates the LFP batteries from the charging buss, there is no load dump effect, the lead batt continues to buffer as always.

BTW I would advice keeping the BMS as a failsafe, use a production HVC for normal cycling stop-charging, only when that fails is the BMS needed.
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Old 08-05-2019, 03:35   #3
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Re: Do I need an alternator protection device when switching to Lithium?

Quote:
Originally Posted by john61ct View Post
Simpler is better.

By "service" I guess you mean House bank, some used to say "auxiliary" as opposed to Starter, aka primary / engine / essentials.

There is no need to "prioritize" direct charging to Starter batt first, that's a marketing gimmick, Sterling being a leader in that.

Just put a lead batt direct inline with alt output all the time, if that's Starter fine. What is "normal", a simple VSR closes the connection to House based on voltage being above a setpoint, does not "switch between" the two circuits.

So if (when) a HVC isolates the LFP batteries from the charging buss, there is no load dump effect, the lead batt continues to buffer as always.

BTW I would advice keeping the BMS as a failsafe, use a production HVC for normal cycling stop-charging, only when that fails is the BMS needed.
Above all sounds fair.

Not sure what OP refers to as Sterling 'Pro Arc' is though?
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Old 08-05-2019, 05:35   #4
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Re: Do I need an alternator protection device when switching to Lithium?

Pro-Con Pro Connect CVSR

Alternator Splitter "Pro Split R"

Not saying poor products, just IMO their touted unique modes are a solution in search of a problem.

Simple VSR/ACR a better choice, Blue Sea ML version as bulletproof as it gets.
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Old 08-05-2019, 09:50   #5
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Re: Do I need an alternator protection device when switching to Lithium?

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Originally Posted by Flod View Post
I’m in the middle o switching to llifepo4 batteries... question is what happens then with the current from the alternator? Does
it:
1. Switch over and charge the start again even though it’s “fully” loaded
2. Burns up in flames (or at least burn the diode) since there’s no load

If no2 I guess I need something like the sterling pro arc
I think the other posters capture this issue, that the load splitter will correctly compensate for sudden lfp battery charging changes by shifting load to the starter batt.

The other issue you don't mention, however, is the often mentioned one that alternators have to work much harder over longer periods of time to charge the LifePos, and therefore can lead to burnout through overuse and thermal issues. I myself am still looking for answers for that issue...
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Old 08-05-2019, 09:58   #6
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Re: Do I need an alternator protection device when switching to Lithium?

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Originally Posted by Whomda View Post
I think the other posters capture this issue, that the load splitter will correctly compensate for sudden lfp battery charging changes by shifting load to the starter batt.

The other issue you don't mention, however, is the often mentioned one that alternators have to work much harder over longer periods of time to charge the LifePos, and therefore can lead to burnout through overuse and thermal issues. I myself am still looking for answers for that issue...
For Alternator stress relief from LFPs go as big as you can fit and or afford.
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Old 08-05-2019, 10:02   #7
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Re: Do I need an alternator protection device when switching to Lithium?

An alternator protection device is there to protect the alternator diodes if the alternator is open circuited. If there is no load on the alternator as in when a battery switch is turned to off the voltage will spike and exceed the PIV (peak inverse voltage) of the diodes and they will be destroyed.

So the answer to your question is a question: Is there a circumstance where the alternator load would go to zero?
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Old 08-05-2019, 10:14   #8
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Re: Do I need an alternator protection device when switching to Lithium?

Quote:
Originally Posted by Whomda View Post
>>>>>>>>>>>>>>>

The other issue you don't mention, however, is the often mentioned one that alternators have to work much harder over longer periods of time to charge the LifePos, and therefore can lead to burnout through overuse and thermal issues. I myself am still looking for answers for that issue...

In every discussion of this technology this issue comes up. Have you been through the extensive and loooong discussion here? LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks


The answer is that the alternator is part of the new SYSTEM and a systemic approach must be used. Loads on the alternator increase dramatically with LPs and the impact of BMS "shutdown" must be addressed to avoid blowing diodes.


Good luck.
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Old 08-05-2019, 11:31   #9
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Re: Do I need an alternator protection device when switching to Lithium?

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Originally Posted by Whomda View Post
I think the other posters capture this issue, that the load splitter will correctly compensate for sudden lfp battery charging changes by shifting load to the starter batt.
No, just the lead batt being online is enough to buffer the LFP being suddenly taken off the circuit.

No need for a "load splitter" whatever that might mean to you

> The other issue you don't mention, however, is the often mentioned one that alternators have to work much harder over longer periods of time to charge the LifePos, and therefore can lead to burnout through overuse and thermal issues.

LFP accept (draw, pull, demand) a much higher amp rate from an alt than a lead bank many times bigger.

If the alt does not have a good adjustable VR like Balmar MC-614, then

a DCDC charger in place of the VSR, will limit current and convert the voltage to match the LFP specs.
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Old 08-05-2019, 11:34   #10
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Re: Do I need an alternator protection device when switching to Lithium?

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For Alternator stress relief from LFPs go as big as you can fit and or afford.
That can be unnecessary, very expensive and still not solve the problem.

Even a small LFP bank can burn out a large but stock-regulated alt.
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Old 08-05-2019, 11:47   #11
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Re: Do I need an alternator protection device when switching to Lithium?

Hi Flod,
You will -depending on the size of your LiFePo battery bank- need a device to protect your alternator from dying premature.
Reason is that LiFePo accepts/takes way more power than normal lead batteries and your alternator with it's standard regulator will work too hard to survive for long.
For in depth info look for Pacific Yacht Systems on Youtube in Ep 06/33-external regulators Jeff is talking 20min about these devices.
And,by the way, the boating world would be far more safe electrically if more boaters would take advantage of his huge knowledge andashared experience shared for free.
Have fun watching
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Old 08-05-2019, 12:24   #12
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Re: Do I need an alternator protection device when switching to Lithium?

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That can be unnecessary, very expensive and still not solve the problem.

Even a small LFP bank can burn out a large but stock-regulated alt.
Sheeesh John, you got me.
Did I mention 'stock regulated'.

Pardon my casual terminology. By 'big' I meant not neccesarily physicaly big, although that usually also applies, but a 'big' designed power output setup.

So ok John you obviously dont want to spend money, like 614 ext regs cost.

What is your much better and cost effective solution?
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Old 08-05-2019, 12:34   #13
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Re: Do I need an alternator protection device when switching to Lithium?

If the answer is yes, which one could argue is always true, then we (Balmar) make a spike protector that can protect the alternator:
Regulator Accessories | Balmar

Chris

Quote:
Originally Posted by stormalong View Post
An alternator protection device is there to protect the alternator diodes if the alternator is open circuited. If there is no load on the alternator as in when a battery switch is turned to off the voltage will spike and exceed the PIV (peak inverse voltage) of the diodes and they will be destroyed.

So the answer to your question is a question: Is there a circumstance where the alternator load would go to zero?
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Old 08-05-2019, 12:39   #14
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Re: Do I need an alternator protection device when switching to Lithium?

I’ll second the Balmar 614. You can monitor and program loads, alternator temperature, charge parameters, belt load. If it works as well as reported I bet it will save money over time on belts and alternators.
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Old 08-05-2019, 12:47   #15
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Re: Do I need an alternator protection device when switching to Lithium?

I'm not at all saying a full upgrade to a higher output alt, serpentine belt etc isn't worth it when called for by a given use case.

But often **just** a DCDC charger, or

just converting to a good external VR, keeping the same alternator,

is all that's needed, was my point.
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