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Old 09-08-2014, 11:33 AM   #1
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Charging from Gen set

I have a 5KW NL AC gen set hooked up to a Mastervolt 24/30/3 charger. This has three outlet ports for charging the high amp port goes to my 24V AGM 420 AH house bank. The most charge I ever see is 20 DC amps on that line and more often 12-16 AMPs. This means that it takes a long time to charge my house bank. The motor will charge 4X faster and a separate shore powered inverter/charger will also charge fast. I am thinking the builder undersized the charger hooked to the GEN set. Mastervolt makes a 24/60/3 unit and I am thinking I should switch to this. So my question is will my 5KW support this? I think so but I am not an electrical know it. The other question is if I pull my 2 year old perfectly good MV 24/30/3 out is there anybody who will want to buy it?
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Old 09-08-2014, 11:41 AM   #2
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You have asked several questions.

You charger is smaller than should have been installed. With a 420 amp bank you could be charging at 100 amps (25%). Usually chargers that large are inverter/chargers. A 5kw generator could support two such chargers so this is not a problem.

As to whether anyone will buy your current charger, likely yes, but then I don't know the market for small 24 volt chargers. Others may chime in.
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Old 09-08-2014, 11:44 AM   #3
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Not familiar with the Mastervolt, but most 3 bank chargers divvy the load up in some fashion and can't allocate full power to any one bank. I take it no inverter/charger attached to this bank, or the one you have is for some reason not driveable by the genset? ? 60 amps at 24 v is about 1.5kw allowing for charger inefficiency.
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Old 09-08-2014, 01:09 PM   #4
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If there is room usually belting a good alt and 3 stage V regulator is the best way to recharge a good sized house bank from the noisemaker..
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Old 09-08-2014, 01:17 PM   #5
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So you have three outlet terminals- what are the three connected to? A 30A charger with three outlets will not put full charge out to each, that is a total. If only one 24v bank being charged, you can and should tie all three outlet terminals together. Then you will get the full 30A. Not sure your charger fits the above, but some do.

Still undersized for your bank. And yes, gennie can handle it. 60a at 24v is about 1.5kW, due to inefficiency it might draw up to 1.8kW.
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Old 09-08-2014, 01:27 PM   #6
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The genny already has a HUGE alternator on it. Just get a 2k inverter/charger. Probably cheaper than a dedicated charger and more amperage. Most will charge at 50 amps easily on 24 volt. Tie it into your ac system and you will be amazed at how much less you need to run the gen. And when you do need to run it the load is better due to the batt charger. Run time will be diminished and load factor will be better. Get Nigel's book.
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Old 09-08-2014, 01:28 PM   #7
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I think that your charger is undersized for a bank that large, plus what ever other banks are on the 2 remaining legs. I would call MasterVolt and discuss the issue. You have plenty of Generator capacity to power a larger charger. I am curious why you have a 24 Volt system and if you have an inverter for A/C loads?
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Old 09-08-2014, 02:21 PM   #8
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The genny already has a HUGE alternator on it. Just get a 2k inverter/charger. Probably cheaper than a dedicated charger and more amperage. Most will charge at 50 amps easily on 24 volt. Tie it into your ac system and you will be amazed at how much less you need to run the gen. And when you do need to run it the load is better due to the batt charger. Run time will be diminished and load factor will be better. Get Nigel's book.
X2 on the inverter/charger. Keep the small charger as a spare or eBay it.
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Old 09-09-2014, 02:32 PM   #9
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eyschulman:

You and I talked on boatdiesel about one part of this question, but I am just now seeing this post which provides more information.

You say that you have an inverter/charger that charges fast, right? And it is hooked to shore power. Normally all of the shore power loads are switched over to the genset with either a transfer switch or locked out breakers. So normally the inverter/charger would be able to charge the batteries from the genset.

Since that doesn't seem to be the case for you, I would suggest having a marine electrician look at your boat and figuring out how to use that inverter/chager from the genset. It might take a simple rewiring job to make it work.

And FWIW all of the above discussion about a 3 output charger not being able to supply its full charge to a single load is probably correct. Tie all three outputs together and you might get a little more charge.

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Old 09-10-2014, 06:33 AM   #10
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>So normally the inverter/charger would be able to charge the batteries from the genset.

Since that doesn't seem to be the case for you, I would suggest having a marine electrician look at your boat and figuring out how to use that inverter/chager from the genset. It might take a simple rewiring job to make it work.<

Perhaps but,,,

More likely with only 5KW of gen set the POWER (the area under the sine wave) is to weak to feed a charger properly.

POWER is required , not mere voltage , and less than 10KW (usually) can never match shore POWER.

Thats why I always go for a 135A truck alt , or a 200-300A bus unit for BIG fast battery recharging in 12 or 24V.

Time is money , probably $10.00 per hour all counted for a noisemaker , so cutting charge times with a big charging alt can save loads of boat bucks if folks anchor out as a rule.
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Old 09-10-2014, 07:25 AM   #11
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>
More likely with only 5KW of gen set the POWER (the area under the sine wave) is to weak to feed a charger properly.

POWER is required , not mere voltage , and less than 10KW (usually) can never match shore POWER..
Not with you here. A 5Kw gen is more than enough to power a 2Kw Inverter/charger unless the other house loads added in total over 5Kw. Power factor will eat up a little more but not 5Kw worth. A good example is a popular Magnum 2012. In charger mode it requires 15 amps @ 120 VAC input with a better than .95 power factor or about 1800-1900 Kw.
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Old 09-10-2014, 07:48 AM   #12
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Is it possible that the battery charger is not charging the battery because it is sensing the genset alternator output at the battery and therefore doesn't calculate the need to charge.
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Old 09-10-2014, 09:44 AM   #13
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1800-1900 Kw.
I meant 1.8-1.9 Kw.
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Old 09-10-2014, 10:38 AM   #14
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The problem with little (under 10KW) noisemakers is the quality of the power.

Just as a cheap chop chop inverter can spin a large motor , the motor does not perform properly , tho it runs.

Air cond , big water makers and scuba compressors have very poor performance on square wave power , as the POWER (energy) is not there.

Look at a small noisemaker with a modest load with a scope , then look at what comes out from the power co.

The difference , what is under the sine wave,, is POWER ,

Weather the load is .5KW or 5KW the lack of POWER in the electric produced is the problem.

Same problem as with the cheap chop chop inverter.
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Old 09-10-2014, 12:02 PM   #15
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If I'm not mistaken the NL 5kw is not a "small" gernerator. It is an 1800 rpm heavy copper and iron machine that has a very good power factor. And not square wave at all. I agree that most light weight 3600 rpm units are exactly as you say.
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Old 09-10-2014, 12:44 PM   #16
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Quote:
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I have a 5KW NL AC gen set hooked up to a Mastervolt 24/30/3 charger. This has three outlet ports for charging the high amp port goes to my 24V AGM 420 AH house bank. The most charge I ever see is 20 DC amps on that line and more often 12-16 AMPs. This means that it takes a long time to charge my house bank. The motor will charge 4X faster and a separate shore powered inverter/charger will also charge fast. I am thinking the builder undersized the charger hooked to the GEN set. Mastervolt makes a 24/60/3 unit and I am thinking I should switch to this. So my question is will my 5KW support this? I think so but I am not an electrical know it. The other question is if I pull my 2 year old perfectly good MV 24/30/3 out is there anybody who will want to buy it?
The 5 kw is plenty to power the 60 amp, 24volt charger. The unit you have would be fine for a small go fast fishing boat that needs to keep the batteries charged when hooked up to shore power. Your needs are different, so it's too small but I would think you can find a home for it. 60 amps will be plenty because the batteries won't accept more than that for very long before their acceptance rate falls below 60 amps.
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Old 09-10-2014, 03:16 PM   #17
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I don't know much about the larger inverters, it is a gap in my knowledge base. But I know some of the larger inverters can do a seamless transfer from invert to shore power, then become a charger and top up batts.

Could the gennie be tied in similar to shore power, with a shore/gen transfer switch so that all the gennie output goes through the inverter the same as shore power? That way regardless of shore, gennie or invert is selected the ac power in the boat will be seamless, and no need for a large charger unless you want a backup.

So instead of gennie being fed into system downstream of inverter and directly into panel, it is upstream of inverter like shore power. No more blinking clocks or waiting for fridge to bleed pressure.
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Old 09-10-2014, 03:36 PM   #18
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So instead of gennie being fed into system downstream of inverter and directly into panel, it is upstream of inverter like shore power. No more blinking clocks or waiting for fridge to bleed pressure.
This is a normal arrangement on many boats. Some circuits are fed from the inverter with pass through from shore power or the genset, while other circuits, water heater, refrigeration a/c are fed only from shore power or the genset.
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Old 09-10-2014, 07:55 PM   #19
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My inverters (2 ME2000s) run everything except the saloon AC. I normally turn off the bigger loads when just using the inverters. The saloon AC is a 16,000 btu unit. It handles the 5000 btu AC in the master well enough. Recharge time is extended substantially after a warm night. I can charge at 200 amps. House bank is 8 T105s. The genny (15 kw) has a decent load in the morning making hot water, coffee, laundry and drying clothes, charging, etc. Usually runs 2 to 3 hours.
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