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Old 05-12-2007, 09:32   #1
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Hi-amperage battery chargers

I'm looking for a sanity check here. We're replacing the entire electrical system on our boat, and I'm thinking of going entirely inverter-based. My reasoning is that what I'd lose in efficiency can be more than made up by simplicity.

The boat's a Formosa 51 cutter/ketch and it's being outfitted for world cruising - so universal shore-power would be nice, hence support for 120-240V/60Hz and 220V/50Hz. We have two MarineAir A/C units, a washer/dryer - comforts of home when we're dockside (hopefully that will be at a minimum). By going totally inverter-based, we'd completely eliminate the need for frequency conversion, and universal 120-240V/50-60Hz battery chargers would give us access to just about any shore power system, as well as function as isolation transformers to protect the boat from ground faults. We have a 7.6kW genset (120-240V/60Hz) as well as a 190A alternator on the engine, and plan on a wind-generator and solar panels for extra redundancy. House battery bank would be on the order of 1000A-h. Of course, on the hook we generally wouldn't pig-out on energy consumption given the rising price of diesel world-wide.

That being said, as I've been searching for high-capacity marine battery chargers, they seem to be just as expensive as inverter/chargers, so I'm beginning to wonder if I should re-think the design. It would be great if someone made a universal input inverter/charger with 120-240V/60Hz output, but all I've seen so far are ones with auto-transfer switches that switch over automatically when shore-power is connected - meaning that they're not universal input.

Anyone know of an inverter-charger whose AC output is always inverter-based and not shore-power based? That way my AC would always be 60Hz. It wouldn't be as redundant as separate chargers and inverters, but we could always go with two such beasts.

Sorry for the misleading title - posted before I realized that while the jist of the post changed while editing, I forgot to change the title. I was originally just ask why high-amperage chargers were so damned expensive compared to high-capacity inverters, inverter/chargers, and high-cap alternators. Less market demand?
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Old 05-12-2007, 10:21   #2
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I read your post twice and am not clear on what you are looking for or want to do. So, here it goes anyway.

I have a Statpower 3000W, 100 amp DC, inverter/charger that I am generally happy with. The reason I say "generally happy" is because when I have a shore power connection where if I cannot pull a good amount of current, the charger will take itself offline if it sees a large enough voltage drop. It is protecting it's circuitry against too low of a shorepower voltage, which is a good thing. So sometimes, if I did not have a smaller charger, I would not be able to keep my batteries topped up because my large charger would keep kicking itself offline. The point I am getting at is you will also need a smaller charger, like a 30 amp, in case you are plugged into some lousy shorepower. Besides, having the redundancy is a good idea.

I set up my 3-way (A-Off-B) AC control switches so that I am in control. In other words, I have to manually switch over from ship AC to shore AC. I don't let the inverter do that automatically for me. I also see it as a safety issue for when I am working on the boats AC system. There are inverters designed for converting European to US current or the opposite, but I have only seen the large industrial grade ones and not something that would be appropriate for a boat. There has to be something.
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Old 05-12-2007, 10:26   #3
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Personally, I'd opt for individual inverters and chargers. Why? If anything ever breaks, it will be more simple to find a new charger in some foreign port than to find this monstrous inverter/charger you are describing.

Plus, buying them all individually allows you to really select the product that does exactly what you wish it to do.

I am running nearly 100% inverter based right now (no longer on a boat, but on land - same systems though). The only items that use 12V are lights and some electronics that control the propane fridge as well as the water pump. All else is done through a dedicated 2500 watt inverter and twin 90 amp chargers along with a 5KW genset.

Works very well.
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Old 05-12-2007, 10:44   #4
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So, are there boat inverter/chargers that will covert between European and American standards? I'm not intending to hijack the thread, I thought the question would be relevant.
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Old 05-12-2007, 11:18   #5
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David,

What I'm aiming to do is create a simpler electrical system which can handle any shorepower system - be it US 60Hz 120V-30A or 120-240V-50A service, or international 50Hz 220V service - while still having the existing AC genset available for either house service or just charging the batteries. Since our existing AC appliances on-board are all 120V or 220V/60Hz, converting 50Hz to 60Hz is a problem. And rather than having some dedicated expensive electronic device do that directly, it's simpler to use universal-input battery chargers and separate inverters, since you need battery charging and DC-AC inverters anyway (to avoid running the genset anytime you need to run an AC appliance). I was just asking if anyone knows of a inverter/charger whose AC output is always generated by the inverter function and not just switched from the incoming AC service. That would get around the frequency problem. Not as efficient, but you'll have losses in a dedicated frequency converter anyway.

There shouldn't be any safety issue with the inverter/charger having an internal auto-transfer switch, as long as you have installed circuit breakers as recommended by ABYC between the shore-power connector and the inverter. All the combined units I've seen are designed that way. And ABYC calls for separation of inverter and genset output via a transfer switch to eliminate multiple neutral/safety ground connections. Of course, another way to accomplish that would be to put a manual shore-genset transfer switch upstream of the inverter/charger.

I was going to put in a smaller charger for the dedicated 24V bank handling the bow thruster and windlass. I didn't think about the low-current cut-off problem on the inverter/charger, so I guess I'll check into a dual-voltage DC charger - I know they exist.

ssullivan - I guess your comment brings me back to my original thought: why are dedicated 12V (or 24V) DC chargers with high output seemingly just as expensive as inverter/chargers with similar DC capacities? Something doesn't make sense when a 2400VA inverter with 100A DC charging capability is just barely more expensive than a 2400 or 3000VA inverter, or a dedicated 100A charger - and a hell of a lot more expensive than a 200A engine-driven alternator.

And using a 100A charger on a 1000A-h battery bank is a waste of time. You'd need two (for FLA) or four (for AGMs) to minimize charging times...
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Old 05-12-2007, 11:26   #6
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David - in a nutshell, that's exactly my question. Seems a simple thing to do: put a universal DC charger and either a US-60Hz inverter or a 50Hz inverter in the same chassis. Everything else in my other posts are just background info on why I'm looking for such a beast. As ssullivan points out, separates would give flexibility, but even on a 50-footer, space is at a premium...

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Originally Posted by David M View Post
So, are there boat inverter/chargers that will covert between European and American standards? I'm not intending to hijack the thread, I thought the question would be relevant.
And I could upgrade the genset/inverter transfer switch to be a four-way (off-inverter-genset-shorepower) for when there is 60Hz shore-power available to avoid the AC-DC-AC inefficiencies...
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Old 05-12-2007, 11:27   #7
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I believe Dolphin and Victron make multi voltage chargers. I do not know if either make a combo unit. You would need to look at there websites. But even if they don't make combo's, there is no reason why you can not have the two seperate units.
Making the boat run off the inverter alone is simply a wiring issue. Easy to do. The charger will be supplied via shore/genset only and the rest of the boat is powered via the inverter.
Now aside from that, I do have a concern with you having 1000Ah of battery capacity. It is all very well having it, but if you discharge 50%, you have to find a way of getting 500Ah back into the bank. Even with a 100A charger, that is going to be maybe 6hrs minimum of genset running time, just to recharge. My thought would be to have a smaller bank, and charge more often. 800Ah is a very large bank and in some respects, still over the top. I t is suitable for very high demand systems that may have a washing machine and microwave etc. 600Ah is more common and more realistic and will cope with most high power demand situations. 400Ah is workable and can still cope with a high power demand system. I have 400Ah and use the genset when using equipment that is high current hoging like the Microwave. The inverter is a combo and shunts 130A back into the bank as soon as the Geny is started up, while still supplying the 230V system to run everything else.
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Old 05-12-2007, 12:21   #8
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Alan,

I should have been more specific - the boat is 12V-based (24V is only for the bowthruster and windlass handled by a smaller dedicated bank). So 1000A-h is not that large - equivalent energy as a 24V-500A-h bank. Converting the whole boat to 24V would involve major changes - genset, engine, lighting - more than I want to tackle right now.

I was planning on running parallel chargers.

All - I did find ssullivan's thread "Scoping out chargers..." from 2006 - lots of good information - especially with regards to the Iota power supply/chargers. A little reading of their documentation reveals they can be externally regulated, so they have the capability of bulk/absorption/float automatically, so one wouldn't have to manually "keep an eye on them".

The one drawback is that they don't support a universal input - however, both the 120V and 240V versions are universal in frequency, so I guess as long as I can get access to two 120V/30A jacks when in the US, I'd be ok, since any properly wired shore-power station on dock with two 30A jacks would be feeding each of them off separate L1/L2 legs of a 120-240V circuit... The only thing my shorepower connection wouldn't handle would be the rare case where the two 30A jacks are the same phase - i.e., 0V between the two load wires rather than 240V...

I also checked with Mastervolt. To get higher amperage, their "Mass" series can be paralleled and run from a single remote controller via a master/slave arrangement - but they don't have universal AC input. There "ChargeMaster" series has universal capability, but according to their tech support, they don't support the master-slave capability of the Mass-series.

Right now Iota is looking good. I'll also check Victron, but with the US dollar low as it is, they're very expensive (Mastervolt's probably are also - didn't check their pricing yet).
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Old 05-12-2007, 20:58   #9
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Yeah 12V is what I was refering to. Mate, 1000Ah is huge, even for 12V. My measly 400Ah does us fine and we don't spare for anything. Infact, most go on about us having the ability to power the local town. Mate, you could take on a small city with that lot.
OK, now on the seriouse side, you have to be able to get back in what you have taken out and plus some for losses. If you use 500Ah, you have to return that 500Ah plus. 1000Ah bank means you can use a 200A charger. I have not seen anything that big. And if there is one, it is going to cost you an arm and both legs and maybe your daughter. Then ther is getting suficient current to run a charger that big. Coming down in size to say 130A, you are going to be running that genset for 5hrs. If you don't use 500Ah, then you are spending money you don't need to, taking up room you don't need to and putting weight into the boat you don't need to. If you run the AC, you should use the Genset to power them two. If you don't, they will certainly suck up the battery juice, but you have to run the genset to recharge the bank anyway. May as well just run the gennset and power the AC units and the washer/dryer when you need them.
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Old 06-12-2007, 19:23   #10
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As Alan mentioned, Victron Energy www.victronenergy.com/ has an amazing variety of solutions for power management where you can piggyback their charger/invertors to give you all the AC power you need and also automatically supplement shore power at peak times if the shore breaker is small. Plus it is the boats UPS solution. You could if you needed set up 2 x multi plus 12/2500/120 (volts/watts/charger amps), but I suggest you do your homework on load analysis before going too big on storage capacity.

Victron has an excellent guide (The book) called “electricity on board” that will walk you through the process.

I am researching a similar upgrade for my own 24v needs with a single 24/3000/70 and use my old 50 amp charger to supplement.
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Old 10-12-2007, 11:22   #11
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Thanks, Pelagic.

I've already done consumption analysis for both at anchor and on a passage. As you can imagine, the big consumers underway are radar/chartplotter and autopilot, followed by refrigeration, microwave, navigation PC, and masthead tricolor (if using a 25W incandescent). With the example numbers I worked up, I get a daily consumption of about 315 Ah. Assuming a charging efficiency of about 85% (that is, putting 100 Ah back into a battery bank actually takes about 117 Ah from the charger), that dictates a battery bank of 630 Ah (assuming 50% discharge) or 950 Ah (33% discharge). So my anticipated 1000 Ah bank is not too far off the mark - assuming my 315 Ah daily consumption is reasonable - and I think I am overestimating a "tad"... At anchor, the numbers are smaller - about 190 Ah. Autopilot and chartplotter/Radar (in power-save mode) make for huge power consumption underway! I'll be looking into a windvane (for redundancy and power savings).

My calculations assume LEDs for most lighting (or AC CFLs running on inverter), inverter efficiency at 85% (sine wave vs. modified sine).

The spreadsheet also calculates anticipated run times for the engine/alternator or genset/charger to recharge the batteries - but for now it's a simple calculation assuming a steady-state current output, which we all know is not true.

If anyone's interested, I can post a copy here of the spreadsheet I put together. It's in Excel, but I can convert it to OpenOffice Calc if anyone prefers. It allows some playing around with power sources (genset/batt charger, solar panels, wind generator) and with consumers. I also played around with it calculating recommend wiring size, but that part's not finished/checked yet. It would be a big help to have it sanity-checked.
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Old 10-12-2007, 11:31   #12
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Post Attachment

The spreadsheet is attached. Since the forum is configured to allow only picture or doc/text attachments, I added a ".doc" to the end of the filename. Just rename it to "Boat Power Calculations.xls" when you download.

Feedback - especially glaring errors on my part - would be appreciated.
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File Type: doc Boat Power Calculations.xls.doc (67.5 KB, 150 views)
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Old 10-12-2007, 11:36   #13
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630 Ah (assuming 50% discharge)So my anticipated 1000 Ah bank is not too far off the mark -
But that is nearly double the size??
Even 800Ah is plenty big enough in your situation.
I don't quite understand why you would want to run Radar all the time. It will come a reduction in life of the magentron.
Chart plotter and of nav equip. are usually pretty small users. Autopilots and refrigeration can be hungry users, but they are not always on as they cycle.
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Old 10-12-2007, 13:41   #14
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But that is nearly double the size??
Even 800Ah is plenty big enough in your situation.
I don't quite understand why you would want to run Radar all the time. It will come a reduction in life of the magentron.
Chart plotter and of nav equip. are usually pretty small users. Autopilots and refrigeration can be hungry users, but they are not always on as they cycle.
I was leaning towards Calder's recommendation of sizing the bank to be 3x the amount used between charging sessions - having 66% reserve rather than 50%. Hence, based on the conservative numbers that I "pulled out of the air" (but at least with a modicum of thought), that calls for a 950 Ah 12V house bank.

And, yes, I did err on the side of caution with the radar - right now I'm calculating based on it being in low-power mode while on passages 24 hours a day (10 minutes in standby, then 1 minute xmit).

The numbers for the refrigeration and autopilot assume they run only a fraction of the time - for the autopilot, I assumed it was actuating the hydraulic steering pump 4 hours in a 24 hour day. Since its maximum draw is 124W, I could probably re-assess that to be running peaked at no more than 2 hours a day. Right now I don't have enough real-world data, so it's just a judgment call.

I've been working on the spreadsheet off and on for several months, so after staring at it for so long I'm sure there are unknown errors in it, on top of the errors I know about and haven't corrected yet...
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Old 10-12-2007, 15:42   #15
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ssullivan -

And using a 100A charger on a 1000A-h battery bank is a waste of time. You'd need two (for FLA) or four (for AGMs) to minimize charging times...

If you're a dockside dandy or a solar panel/wind guy that would be true. If you run a genset, like I do, the above statement is quite false.

Quote:
Originally Posted by Beausoleil View Post

I guess your comment brings me back to my original thought: why are dedicated 12V (or 24V) DC chargers with high output seemingly just as expensive as inverter/chargers with similar DC capacities? Something doesn't make sense when a 2400VA inverter with 100A DC charging capability is just barely more expensive than a 2400 or 3000VA inverter, or a dedicated 100A charger - and a hell of a lot more expensive than a 200A engine-driven alternator.
Again, not sure I agree:

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