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Old 24-05-2019, 07:40   #1
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Voltage surge, a problem?

I am going for a setup with 2 battery banks, A and B:
A. 200 amp. Lifepo4, B. 50 amp. redtop optima.
Alternative 1. House loads run from A; thruster, winch and engine from B
The concern with this is whether the voltage surge, when running the thruster will affect the electronics on the engine (Volvo Penta d2 55hk) – otherwise this setup should be OK (engine is running when winch or thruster is used and only one of those are used simultaneously)

Alternative 2. House loads and engine from bank A and thruster and winch from bank B.
The concern with this setup is whether the voltage surge from starting the engine will affect e.g. navigation instruments. Now I know that LIPO batteries are quite resilient to voltage surge, but does anybody have any experience with this?
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Old 24-05-2019, 08:00   #2
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Re: Voltage surge, a problem?

It wouldn't be voltage surge, would it? It would be voltage sag.


IIRC, Mine Sail has suggested using the house bank because it is normally a lot larger than a start or reserve bank, thus able to handle larger loads.
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Old 24-05-2019, 13:01   #3
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Re: Voltage surge, a problem?

First off, do not use LiPo.

LiFePO4 is great, but maybe its care & infrastructure not as simple as you think.

Next, forget Optima as a deep cycling batt, not that great value for money long term even just as a Starter.

That said, **if** the input from engine alt is high relative to the big-load

= thruster / winch (windlass, high gph watermaker etc)

**and** big-load is just very short bursts, then Optima can handle #2, but not as well as #1.

LFP will deliver more amps longer to big-load with less voltage sag.

Now, interference with engine loads? Not a concern either way.

Another data point - can crank the engine just as easily from either.

Now, sensitive electronics **may** be affected by transients from big-load operations.

Here's my two proposed solutions, and assuming a smaller lead X Reserve bank not necessarily Optima. LFP House is Y.

A: Put in two make-before-break 1-2 switches (no Off position) directing each of two load circuits as you like,
1. cranking engine Starter, and big-loads
2. Sensitive electronics
between X or Y

B: lower cost and complexity, only one such load-directing switch for #1 loads above, leave load #2 hard-wired to House.

Scenario either way is, can support #1 big-loads off either bank as you like, suggest House by default. Obviously A gives more flexibility to run #2 off the other bank from #1's.

Another alternative (could be added to B later if proven necessary) is to give #2 its own little battery Z, but I think moving to A would be better.

Note none of the above has to do with directing charge sources. Ideally all important ones go directly to Y House, and X is fed by a DCDC charger, Z could tie into either side via small VSR or Echo Charger, depending on its chemistry.
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Old 24-05-2019, 13:27   #4
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Re: Voltage surge, a problem?

Quote:
Originally Posted by john61ct View Post
First off, do not use LiPo.

LiFePO4 is great, but maybe its care & infrastructure not as simple as you think.

Next, forget Optima as a deep cycling batt, not that great value for money long term even just as a Starter.

That said, **if** the input from engine alt is high relative to the big-load

= thruster / winch (windlass, high gph watermaker etc)

**and** big-load is just very short bursts, then Optima can handle #2, but not as well as #1.

LFP will deliver more amps longer to big-load with less voltage sag.

Now, interference with engine loads? Not a concern either way.

Another data point - can crank the engine just as easily from either.

Now, sensitive electronics **may** be affected by transients from big-load operations.

Here's my two proposed solutions, and assuming a smaller lead X Reserve bank not necessarily Optima. LFP House is Y.

A: Put in two make-before-break 1-2 switches (no Off position) directing each of two load circuits as you like,
1. cranking engine Starter, and big-loads
2. Sensitive electronics
between X or Y

B: lower cost and complexity, only one such load-directing switch for #1 loads above, leave load #2 hard-wired to House.

Scenario either way is, can support #1 big-loads off either bank as you like, suggest House by default. Obviously A gives more flexibility to run #2 off the other bank from #1's.

Another alternative (could be added to B later if proven necessary) is to give #2 its own little battery Z, but I think moving to A would be better.

Note none of the above has to do with directing charge sources. Ideally all important ones go directly to Y House, and X is fed by a DCDC charger, Z could tie into either side via small VSR or Echo Charger, depending on its chemistry.
What, apart pretty stars, does **if** **and** and **may** mean? More of your special Shorthand code.
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Old 24-05-2019, 13:52   #5
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Re: Voltage surge, a problem?

That's no shorthand and nothing special. If you're old enough to remember when we could ONLY type in plain ASCII with no pretty emotigifs and no choice of fonts, setting a word in ALL CAPS or setting it with an asterisk on either side was the only way or providing emphasis for important words.

And today, yes, right here and now, some of us can still only interfact the forum with text editors that use plain ASCII, no "pretty processors", so the ancient and venerable ways of indicating emphasis, or what the first versions of HTML called /STRONG, are still used.
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Old 24-05-2019, 14:21   #6
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Re: Voltage surge, a problem?

Yes my editor uses Markdown flavor of formatting markup

https://www.markdownguide.org/basic-syntax
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Old 24-05-2019, 14:39   #7
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Re: Voltage surge, a problem?

Thanks Stu, my understang of setting up the power supply is likely better than my English - "sag" is the word I was looking for. Now, I am interested in whether voltage sag could create any problems either way. The Volvo has a sensitive electronic control box that doesn't like low voltage events, neither does the B&G autopilot or plotter. On my previous boat my Lifepo4 bank was twice the size (400 amp) and I ran everything from that without problems. But, that boat had a Yanmar engine without electronic steering box...
I am not worried about whether the optima together with the alternator will be able to drive the winch and the thruster, that's been tested in real life over a couple of years….
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Old 24-05-2019, 14:45   #8
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Re: Voltage surge, a problem?

john-
IIRC "strong" and "emphasis" were both, what do they call it? Denegrated? Deemed obsolete and no longer fully supported in some modern HTML, so it could even be something in the web forum software that is getting upset and "reverting" them.
One more reason to stick to ASCII editors and avoid the man behind the curtain.
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Old 24-05-2019, 14:59   #9
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Re: Voltage surge, a problem?

The redtop isn't a deep cycle battery or even dual purpose battery. It's a starting battery. When I start my engine from my now aging (but otherwise relatively healthy) 220 a/h AGM's it causes the voltage sensitive stuff to start resetting and I get met with a chorus of beeps every time I turn the starter key. I'm beginning the process of installing a redtop as a starter and 200 a/h LFP house bank. I don't have a thruster, but I have a 1200w anchor winch. LFP shouldn't drop voltage under load quite like lead acid does, but it is very important to make sure that the battery discharge rate isn't exceeded or there is a risk they will shut down at an inopportune moment. My plan is to start the engine with the starter battery and run everything else, including anchor winch, from the LFP.
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Old 24-05-2019, 15:33   #10
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Re: Voltage surge, a problem?

Deprecated.

I am not concerned about how they get rendered for display, they indicate strong emphasis as they are in plain ASCII, which is why I use that rather than html.
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Old 24-05-2019, 15:44   #11
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Re: Voltage surge, a problem?

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Originally Posted by Reefmagnet View Post
LFP shouldn't drop voltage under load quite like lead acid does
Nothing at all like lead does, if sized properly should be of no concern at all.

> it is very important to make sure that the battery discharge rate isn't exceeded or there is a risk they will shut down at an inopportune moment.

That would only be a concern if you chose the wrong BMS, or installed so-called "drop-ins", not recommended.

Full BMS protection can be designed so there is no C-rate discharge limit, just use fuses for OCP.

> My plan is to start the engine with the starter battery and run everything else, including anchor winch, from the LFP

That is sound, but IMO dedicated Starters is carrying more "dead lead" than you need to.

If your LFP bank dies completely when you're far from shore, will the Starter be enough to get you back to safety?

Not saying it won't, but the question must be asked for each use case.

Note a little LI jumpstarter powerpak, kept charged and regularly tested, can act as (belt & suspenders) extra cranking redundancy if the "House + deep cycle Reserve" design seems not enough.
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Old 24-05-2019, 16:17   #12
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Re: Voltage surge, a problem?

Quote:
Originally Posted by john61ct View Post
Deprecated.

I am not concerned about how they get rendered for display, they indicate strong emphasis as they are in plain ASCII, which is why I use that rather than html.
I dont care what you write either. But if you dont write in plain English dont expect me or others to understand what you are attempting to say. In which case I will just pass your post over or make my own WAG that may offend you.

Makes no difference to me.
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Old 24-05-2019, 16:30   #13
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Re: Voltage surge, a problem?

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Originally Posted by Q Xopa View Post
I don't care what you write either.
You sure do put a lot of time and energy into contradicting that.

Feel free to just ignore my posts, if that helps increase your peace of mind.
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Old 24-05-2019, 21:31   #14
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Re: Voltage surge, a problem?

The redtop is in there for its low weight, high CCA and as a dump/buffer if the BMS (or me manually) disconnects the Lifepo4-bank from the charge bus. When on shore power the Lifepo4 block is isolated and all 12 volt service is run by the shore charger via the redtop.
Anyway, the thruster draws a nominal 540 amp which is within the specs for the Winstons (3C on a 200 amp bank), so I will probably follow Mainesail's recommendations and put the thruster and winch on those and the engine on the redtop. If I get trouble with the navigation instruments due to voltage sag, I will put them on a DC-DC converter.
(John: I too find it very difficult to read your first post, but thanks for your reply all the same)
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Old 24-05-2019, 21:36   #15
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Re: Voltage surge, a problem?

Quote:
Originally Posted by john61ct View Post
You sure do put a lot of time and energy into contradicting that.

Feel free to just ignore my posts, if that helps increase your peace of mind.
Youre right your content I can decipher that you preach that is rather fast and loose with facts I do try and not let that be perpetuated.
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