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Old 15-02-2009, 07:58   #1
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charging system question

So, I need a little help here please, I am installing ( have installed) a new charging system
The main question is do I need a regulator as well as the battery combiner?
These are the details of the system- and I do not use a lot of power, no refrigeration, no pressure water.
I use wet cell 12v batteries which I like. 300AH in house bank, plus a starting battery.
63 Amp alternator, externally regulated.
No Battery switch, each bank is on a separate Blue Seas breaker, 150 Amp for the engine bank and 50 for the house bank, each with its own voltmeter.
West Marine 100 combiner.
I have read/ heard that the battery combiner acts as a regulator and adding a heart/xantrex regulator is just muddling things up, is this true?
Thanks in advance
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Old 15-02-2009, 08:18   #2
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I don't quite understand your question as you say that you already have an external regulator. Is this a 3 stage regulator? What make/model is it?

Your combiner does just that, it combines the battery banks automatically for charging, it does not regulate anything. It also isolates the battery banks when you are not charging in order to keep your start batteries from discharging by house loads.

It sounds like your alternator is really not adequate for a 300 ah battery bank. You would be better off with about 80 amp alternator (25 % of bank capacity) or perhaps better, a 100 amp alternator. Although it sounds like your house loads are low (you don't really mention what your loads are and I am assuming they are low). Hopefully your alternator connects directly to the house bank.
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Old 15-02-2009, 08:42   #3
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Deep Frz, thanks for the answer,
I do not yet have an external regulator, just switched to a different alternator. I realize my alternator is small, but actually the alternator really does not get much use in supplying power to my system, almost all power into the batteries comes from 2x100 watt solar panels and a wind generator. Total usage when cruising runs about 25-35 AH a day,
interior lights are almost all LED's, no auto pilot, just a windvane, running lights are all LED, the heaviest power draw is the GPS/ Laptop.

I already have the combiner as was wondering if I need a regulator as well, by your answer it looks like I do.....
THanks
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Old 15-02-2009, 08:53   #4
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I would recommend an external 3 stage regulator unless your internal regulator is 3 stage. I doubt it but don't know for sure. A 3 stage regulator will protect your batteries from over charging while ensuring a quick charge when motoring. You are right that your power requirements are low and in your case the alternator you have should be fine if you can control it with a 3 stage regulator.
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Old 15-02-2009, 09:08   #5
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If I understand correctly you have an alternator which requires an external regulator and you have not bought one for it yet. If this is true then it is doing very little. The field coil is what makes the magnet, so that spinning the rotor coil in that magnetic field makes electricity. You can directly plug the field connections to a 12 volt source and the the field coil makes a magnetic field, then alternator will produce its maximum current, this will result in frying your batteries. If the field contacts are shorted no magnetic field, no produced electricity. If they are open a little unknown amount of electricity is made by the rotor inducing a magnetic field in the field coil (This discovery was made trying to troubleshoot a car failure in the middle of nowhere on the highway.)

The simplest regulator is an automatic switch for turning the alternator (powering the field coil) on and off at a preset voltage. So if the battery is low, it is on, when the battery is at the voltage that you don't want to exceed it turns off.

The combiner is another automatic switch, it has nothing to with controling the alternator. It mimics you looking at a voltmeter. When the voltage is high enough on the battery that your alternator is attached to that you know it is charging, you connect all the batteries together so they all charge, when the engine dies and you see on the voltmeter that the voltage decreases below the charging voltage, you separate the batteries from each other.

John
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Old 15-02-2009, 09:20   #6
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Thanks John,
just got back from buying a xantrex 3 stage regulator.
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Old 15-02-2009, 11:55   #7
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Battery combiners are not voltage regulators. Battery combiners are a fancy on-off switch that close when you reach predetermined voltage level and then open so as to isolate two different DC circuits after a certain voltage level has been reached....making it "impossible" to draw down one of the two circuits too much.

The problem with battery combiners is they are mechanical devices prone to failure either through the solenoid failing or there being too much of a current surge caused by the batteries equalizing when the combiner closes. They are rated to a specific number of amps.

Personally I like battery isolators (a big diode) better because they are not mechanical and therefore more reliable. You can compensate for the voltage drop across an isolator by placing the alternators voltage sense wire on the battery side of the isolator. The resultant slightly higher voltage on the alternator side of the isolator is not going to hurt anything...even fancy computerized engine controllers and sensors, which are designed to take voltage fluctuations.
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