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Old 14-05-2012, 10:17   #31
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Re: Charger Only Recommendations

I vote itoa as well

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Old 14-05-2012, 10:39   #32
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Re: Charger Only Recommendations

Originally Posted by btrayfors View Post

An excellent question!

First impression is that an 8D AGM dedicated to starting a small-to-medium size diesel is WAY overkill. A group 31 flooded or AGM would be more than enough (like the Lifeline GPL-3100T). That third 8D could be used for the house bank, increasing its capacity to 675AH.

If I understand correctly, you have two 50A alternators and one 50A battery charger. So, at dockside or with a generator you have a maximum of 50A charging capacity. And, with the engine running you have a maximum of 100A charging capacity.

Those AGMs when 50% discharged will take up to their AH rating in charging amps, e.g., the two 8Ds now in your house bank can take up to 450 charging amps rather easily. Three of them could take 675 charging amps.

While it's highly unlikely that you could ever have enough charging capacity to reach those numbers, it is a good idea to have charging capacity of at least 25-30% of AGM's rated, say, a minimum of 100-125A charging capacity.

From that perspective, it looks like you're way under-equipped in terms of charging ability, particularly for short dockside overnites or for generator-supplied charging.

Also, it's unlikely that the two alternators could put out their full 50A rating each for very long, without overheating. And, through the natural process of heating up to operating temperature, alternator output drops. So, let's assume that those two alternators -- working to their normal operating temperature capacity -- could together put out about 80-85 amps.

AGMs have a relatively low internal resistance, so can take lots of amps even in the acceptance phase.

Whether or not it's worth it to you to upgrade your charging capacity depends on how you use the boat, and whether or not you're comfortable with charging those AGMs long enough for them to reach a full charge at least once every couple of weeks.


Yes, I know about the oversized/underutilized eng start batt, but only because you & others told me so awhile back in a different thread! The boat came to me from the PO with the 3rd 8D for starting only(??), and neither I nor apparently the tech who I had replace all the batts & charger two years ago knew any better at the time. Your advice is particularly apt since I have crossover relays that allow me to draw on the two house batts if need be when starting either the eng or genset! (The gen has it's own, much smaller start batt which is charged by a BEP VSR echo-type charger off the eng batt -- maybe this could also be used for an eng start). After two years in he current configuration, however, the consensus seems to be to now wait until I need to replace all the batts. to reconfigure. Agreed?

Yes, dockside or via my genset I have a max of 50A charging capacity with my Xantrex. When motoring, I have one 50A eng alt. that charges only the one 8D start batt., and a 2nd 50A eng alt. that charges only the 2 house batts that comprise the house bank. So the two alts are not combined -- they charge the two banks separately.

So if/when I reconfigure to put the 3rd 8D into service as a house batt., the wiring for the input/charging side of the system -- via the Xantrex or the eng alts -- can theoretically remain the same, albeit with enhanced charging capacity as Bill suggests. The existing Xantrex, for e.g., could be dedicated to a single 8D, and a second, 100A charger for the remaining two 8D's. (Xantrex doesn't seem to make the XC series anymoe so I'm not sure I could combine them). Likewise, I could leave one of the 50A alts that already charges only one 8D in place, and then upgrade the 2nd one to 100+ amps for the other two 8D's. Maybe??

On the output side, I have a 1-2-ALL-OFF switch for the two house 8D's, and a separate On-Off switch for the eng start 8D. Not exactly sure what to do about this yet but hopefully there's a reasonably simple solution w/o having to invest in more components. Could I combine all 3 house batts. onto the one switch? Does that mean I need a 1-2-3-ALL-OFF switch or does it not matter if all 3 are wired in parallel as one house bank? Or maybe re-wire the eng switch to use for the new #3 house?

I'd like to think I could avoid bringing more complexity into this already far too complicated system but we'll see. I'd also like to think I could accomplish much of this myself this time, but we'll definitely have to wait & see on that one! If not, at least this time I'm hoping -- thanks mostly to this forum -- I can be more on top of what is going on. Thanks for all the great advice & apologies for getting off-topic here.


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Old 14-05-2012, 11:31   #33
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Re: Charger Only Recommendations

Originally Posted by HopCar View Post
+1 on the Newmar chargers. They are just about bullet proof. I've sold many brands of marine battery chargers including Xantrex, ProMariner, Charles, Guest and others. We've had warranty issues with all of them, except Newmar. The only Newmar I've had to return in the last six years had been underwater. If you decide on a Newmar I would love a chance to quote you on it.
DC Power Onboard with Newmar's Phase Three Smart battery charging technology is now available in a wide range of power levels, allowing you to select the right size, features and flexibility you require for virtually any application from small recrea
My boat was delivered from new with a Newmar charger. It's a very pretty, professional looking piece of gear in a stainless steel box with current meters on it. But it blew up at nine years old -- and more cost to fix than to replace. The electrical genius of Cowes told me it was a typical failure for Newmar chargers -- some capacitor or something. I have a second, smaller Newmar charger on board which is dedicated to my engine start battery.

I replaced the failed Newmar charger with an expensive Victron charger/inverter which (knock on wood) has been performing well so far. My electrical guy in Cowes didn't really approve. He is a Victron dealer and says that he sends more Victron stuff back for warranty repairs than anything else. "Not worth the money", he said, "although, by all means, buy one from me if you insist, the margins are much better for me".

He says that the el-cheapo Sterling chargers are the really bulletproof ones, despite their low cost. He intalls them, and then never sees them again, he said.

For What It's Worth! As they say. I am loving my Victron inverter/charger with its current-limiting and power boost functions, and its excellent inverter, but those who know more than I recommend the "cheap and cheerful" Sterling.
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Old 14-05-2012, 11:40   #34
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Re: Charger Only Recommendations

I've always 'heard' good things 'said' about Mastervolt & Magnum, but it could be just that . . . 'hear-say'. Not sure if either makes a stand-alone charger, however. I also think they're both kinda pricey compared to some others. Nothing but good luck with my Xantrex thus far, but it's only been two years. The first one I had installed, btw, was defective and had to be exchanged. Both were the XC5012 model.

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