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Old 23-03-2017, 09:25   #1
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Do I need a "Smart" voltage regulator?

I'm replacing the house bank on our P-34 with two group 31 FLA's. I have no high output alternator, but want to have enough battery capacity to run refrigeration around the clock. Should I be installing a smart regulator in order to keep the battery bank over 50% charged? If so, which models fit this application?
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Old 23-03-2017, 09:53   #2
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Re: Do I need a "Smart" voltage regulator?

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I'm replacing the house bank on our P-34 with two group 31 FLA's. I have no high output alternator, but want to have enough battery capacity to run refrigeration around the clock. Should I be installing a smart regulator in order to keep the battery bank over 50% charged? If so, which models fit this application?
That, I believe, depends on your alternator. If your alt is capable of having an external regulator, then it would allow for better charging of the batteries while the engine is being run. Post what make your engine / alt is, and perhaps someone can determine whether an external reg can be added. However, you will hardly ever get your batteries fully charged by running the engine, unless you have a long day of motoring...

Which brings me to what you really need... a solar panel with a controller. A 100 watts ought to do it. With the controller, this shouldn't cost much more than the alt regulator (maybe $300, not including mounting?).

This is really the only way to keep your bank charged while your not motoring (unless you have shore power). If you're asking about keeping the refrigeration running while your on the hook for a few days, solar is still the preferred route.

Perhaps you already know this, but lead acid batteries really want to be fully charged to remain healthy and long lasting. If your goal is only to keep them above 50%, I doubt you'll hardly ever get them past 90%, let alone 100%. Perhaps you are fine with replacing the bank every two years, but if you're not, get the bank to 100% as often as reasonably possible (some say once a week is the longest period between a full charge, other try for after every discharge). Shore power, solar and wind are the practical ways to get you there.

Whatcha think?
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Old 23-03-2017, 10:13   #3
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Re: Do I need a "Smart" voltage regulator?

I think you are going to need a bigger battery bank. You may make it though charging am and pm. With a bigger bank you will need a bigger alternator to replenish it. I found I barely kept up with a small refrig, a 100 amp alternator, a smart regulator, running 1.25-1.5 hours a day.
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Old 23-03-2017, 12:35   #4
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Re: Do I need a "Smart" voltage regulator?

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I have no high output alternator, but want to have enough battery capacity to run refrigeration around the clock. Should I be installing a smart regulator in order to keep the battery bank over 50% charged?
Yes, see http://www.cruisersforum.com/forums/....php?p=2354480

Bigger alt, that EVR, bigger bank, as many solar panels as possible.

Charge using fuel early AM from the Alt well into Absorption phase, so that the solar can finish topping up to full 100% ideally every day.

The 50% point is what you try to never go below. Both these required to maximize battery longevity.
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Old 23-03-2017, 12:38   #5
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Re: Do I need a "Smart" voltage regulator?

Quote:
Originally Posted by RSB333 View Post
I'm replacing the house bank on our P-34 with two group 31 FLA's. I have no high output alternator, but want to have enough battery capacity to run refrigeration around the clock. Should I be installing a smart regulator in order to keep the battery bank over 50% charged? If so, which models fit this application?
In a word: YES
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Old 23-03-2017, 13:52   #6
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Re: Do I need a "Smart" voltage regulator?

I'd go Solar first, alternator and regulator second. Unless you plan on motoring every day that is.
Or go with a Honda suitcase gen
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Old 23-03-2017, 18:24   #7
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Re: Do I need a "Smart" voltage regulator?

Thanks for all the good tips. I will try to get the make and model of the alternator and determine it's output. The engine is a Universal M-25.
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Old 23-03-2017, 18:45   #8
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Re: Do I need a "Smart" voltage regulator?

I think you also need to determine how much juice your fridge pulls. Will be determined by the age/type of fridge unit, the size of your box, the quality of the insulation, and your cruising grounds. At the very least do a simple test to see what it draws when it's running and a rough estimate of how many hours per day it runs.

Assuming that your box draws in the neighborhood of 60 amp hours per day on average, It's going to draw 60% of your available power. Probably significantly more during the height of summer.

A smart regulator will optimize your charging but it's not going to make a huge difference to how long each day you need to run your engine to adequately charge your bank.
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Old 23-03-2017, 21:36   #9
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Re: Do I need a "Smart" voltage regulator?

You do realize, I hope, that you will need about 5 - 7 hrs. to recharge your batteries. Maybe even longer. Please read the many threads about battery maintenance.
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Old 23-03-2017, 21:46   #10
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Re: Do I need a "Smart" voltage regulator?

Actual alternator output will vary from published specs - some drop output dramatically when they heat up. We cruise in BC about same latitude as you and have a 420 Ah bank. That will run our boat for 2 days at anchor - freezer, fridge and minimal lighting. Determined through testing that our daily draw was
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Old 23-03-2017, 21:59   #11
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Re: Do I need a "Smart" voltage regulator?

Quick reply too quick !! Our daily draw was 105 Ah so keeping battery bank above 50%. But alternator was only rated at 55 amps and put out a lot less hot. Alternator output should be about 25% of the size of your bank so I was horribly undersized and couldn't recharge with any amount of motoring. No room to fit enough solar so went to a 120 amp alternator and external regulator so we can cruise in more remote locations.
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Old 24-03-2017, 06:40   #12
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Re: Do I need a "Smart" voltage regulator?

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Actual alternator output will vary from published specs - some drop output dramatically when they heat up.


This, I can get 80 amps out of my 125 amp alternator, and it cuts back intermittently due to heat.
To generate power, you generate heat. How can the same size and weight alternator with the same cooling fans etc., make three or more times the power without overheating? I don't think they can.
My belief is if you try to actually pull the high amps out of these that they can make, without thermal protection, you will burn one up.
I'm not real sure your getting more actual output out of these big small frame alternators than a medium power one.
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Old 24-03-2017, 06:53   #13
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Re: Do I need a "Smart" voltage regulator?

http://www.cruisersforum.com/forums/....php?p=2354480

Nice thing about the MC-614 is it gives you good control over the amperage output, independent of your bank's demand.

Lots of stock setups do all kinds of sub-optimal stuff when they heat up, so a good VR upgrade will help you tune things even keeping the same alt.

But yes a nice large frame HO alt is the way to go if you can, even if you only set it to output half its rated capacity.
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Old 24-03-2017, 07:01   #14
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Re: Do I need a "Smart" voltage regulator?

Something like this to start with:

https://sterling-power.com/collectio...tor-regulators

and then something to monitor the state of the batteries, so:

Clipper BM-1 Battery Monitor - Nasa Marine Instruments

Both available in the US but often re-badged under another name.

That gets you charging the batteries but as A64pilots says in his first post, solar is the long term answer.

We are a similar size and are just upgrading from a 80w plus 30w and 60w suitcase panels, to 150w plus 30w and 60w suitcase panel. Why? because it takes hours to bring our 2 x 31FLA batteries up to full charge with the alternator. The panels can sit there quietly doing their thing whilst I don't have to listen to the engine gurgling away running cool and under no load charging batteries.

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Old 24-03-2017, 07:08   #15
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Re: Do I need a "Smart" voltage regulator?

Hi RSB

So far I think most replies have offered very good information. My two cents and maybe to summarize.

1. First thing, you need to get an estimate of your energy use. How many amp hours/day your fridge, lights, radio, etc will use. Generally the fridge will be by far the largest draw so check that first.

2. Based on the answer from #1 you can then determine how many batteries you need and the best way to keep them charged.

3. Smart charger? YES, if your alternator can be modified to use an external regulator AND it has the capacity to put out more power over a long time without overheating. If this is the stock alternator that came with the engine then you can only boost the output so far.

Important considerations,

1. As someone mentioned, to fully charge your batteries from engine alone will take most of the day. With properly sized alternator and battery bank you can charge them from 50% to about 80% in an hour or two.

2. SOLAR!!! By far the best, most reliable system to keep batteries charged off the grid. However, unless your fridge is very small you will need more than a 100 Watt panel.


Bottom line, if you plan to keep your boat off shore power and especially if you're running a fridge (even a small one) you're going to have to put some attention into the charging system or you will be replacing batteries every couple of years or so.
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