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Old 30-05-2019, 12:27   #1
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No big battery chargers?

I've been endeavoring to learn all I can about the charging system on my boat and just when I think I'm understanding it I get surprised by something. Electrical stuff is generally easy for me to understand and work on, but I'm not all the way there on charging.

My boat has no solar or wind (yet). I have an older Trace U2512 inverter/charger (2500 watts, 12v, up to 120 amp charging), a 110 amp Balmar alternator on my engine, and a 120vac/8kw generator with it's own 70 amp Balmar alternator. Have Balmar ARS-III regulators and a ProMariner battery isolator. It's a well put together system, thanks to previous owner(s).

For house batteries I have 6 GC2 six volt AGMs in a series/parallel config giving me 12v and 750 AH.

I don't love the old Trace inverter/charger although I can't say it's not working. While it is "smart" and does appropriate staged charging it's finicky to set up (no pre-programmed charging maps, each stage is set manually) and it does not have a battery temp sensor, just a small knob to set (guess) at expected ambient temps at the batteries.

I don't have big loads. Maybe 8 amps avg for refrigeration 24/7 plus more for lights at night on the hook; maybe 22-25 amps underway with instruments and autopilot running. I've reduced my loads about as far as I can I think.

Most of my charging comes from my generator and I want to minimize run time as much as possible. As a side note I noticed that when on 120- 125v shore power my Trace would push 120 amps when in bulk (when bank at 50% soc), but the generator only put out 110 volts and I'd maybe see max 75 amps charge through the Trace. So I tweaked the generator to put out ~120 volts and it now does as well as shore power. This was a big win as it dramatically reduced my generator time, and got me thinking about everything.

So I got to wondering if I should replace my inverter/charger, rated at 120 amps charge output, to something with more output, and much better controls including automatic temp compensation. I see units up to 200 amp output. But then I thought I hardly ever use the inverter. A small microwave is the only remaining piece of equipment on the boat that isn't 12vdc, and we never use it. If I need 120vac for any short term thing, like the microwave, I can run the genset briefly. So why not just get a great charger and forget the inverter? This would be especially useful in that good chargers seem indifferent to the various voltages and hz I see in the Caribbean.

Now here's the rub (finally!) and my confusion. The top brands like Mastervolt and Victron only make chargers with up to a max 100 amp outputs. I can't find anything larger. What this tells me is that I'm probably wrong in thinking that bigger is better and will charge faster. But wait - you can get alternators/regulators with much bigger outputs. Why is that so, and inverter/chargers go up to 200 amps, but not stand-alone chargers?

Again my primary goal is to reduce generator run time (please don't suggest solar or wind for now, thank you). What am I miss-understanding regarding chargers? Or do I just have to buy an inverter/charger to get more charging amps and reduced charging time?

I know am about to be enlightened.

Thanks,

JR
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Old 30-05-2019, 12:58   #2
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No big battery chargers?

A bigger charger isnít going to do much if anything at all for you, cause sooner than you think, your up to absorption voltage and the one you have is backing off in amps.
What you need is Solar, then you only have to run the generator for 30 min a day first thing in the morning, and sometimes maybe not at all.
Spending your $$$ on Solar is they way to reduce generator time, not a bigger charger.
Magnum makes bigger inverter / chargers, and maybe not as fancy with Bluetooth or something, Iíve not heard of a failure on one yet, but if it does, itís highly modular with easily replaceable cards that are actually priced not so bad.

However I would not replace what you have as going bigger would only make about 15 min difference in charge time as a guess, likely less.
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Old 30-05-2019, 12:58   #3
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Re: No big battery chargers?

Yes, bigger is better for AGM battery chargers.

The AGM battery wants lots of charging current.

As-shown in the Lifeline Technical Manual (IMO the best battery manual) the batteries want recharge rates up to 5C (500A for a 100Ah battery).

The three stage charger will provide that high-current Constant-Current bulk charging until the battery reaches the temperature-specific Absorption Voltage.

The charger changes to Constant-Voltage until the charging current drops to 0.5% of the rated capacity, 0.5A for a 100Ah battery.

The charger then switches to Float Charging, also temperature-dependent.
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Old 30-05-2019, 13:02   #4
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Re: No big battery chargers?

AGM will initially accept much higher rates than flooded, but even with AGM the total time to fully charged isnít much different.
https://marinehowto.com/how-fast-can...ry-be-charged/
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Old 30-05-2019, 13:13   #5
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Re: No big battery chargers?

Quote:
Originally Posted by jr_spyder View Post
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Now here's the rub (finally!) and my confusion. The top brands like Mastervolt and Victron only make chargers with up to a max 100 amp outputs. I can't find anything larger. What this tells me is that I'm probably wrong in thinking that bigger is better and will charge faster. But wait - you can get alternators/regulators with much bigger outputs. Why is that so, and inverter/chargers go up to 200 amps, but not stand-alone chargers?>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>R

That part's easy.


The inverter charger combos are essentially two operations in one package, right? So as the inverter size goes up, so does the charger size, because they, simplistically, use the same "guts" to work AC to DC or DC to AC.


And while the difference between 100A and 120A may seem like a lot, one only sees true bulk amperage so a reasonably short period of time between startup and when the battery voltage comes up to switch to absorption. Sure, if the bank is 50% SOC this could be maybe a half hour with your bank, but it is less of an impact than you might think because to get a bank completely full takes overnight even with a huge charger because of battery acceptance - the fuller they get the longer it takes once target voltage is reached.


I believe it is almost analogous to Maine Sail's discussion of internal vs. external regulation for alternators.



How Alternators & Regulators Work PLUS External vs. Internal Regulators (by Maine Sail): http://forums.sbo.sailboatowners.com...d.php?t=125392


You have a robust house bank and AGMs accept larger bulk amperage than wet cells. You also have a fairly typical consumption.


You didn't say how you plan on using the boat. If you're weekending or doing short cruises, it wouldn't make much difference, 'cuz you're topping off your bank but not completely filling it which would take forever even on the generator.


If you want to be self-sufficient long term, then solar's the next step before I'd spend any $$ on a new charger. I have a 20 year old Heart Freedom 15, 1500W I, 75A C, 390 ah wet cell house bank, no generator or solar. I cruise locally and can go a few days of steadily diminishing returns from running the engine's 100A alternator at anchor before I either move and motor for a few hours or go plug in.


You have a very good set up already. Go solar, minimize the generator and charger dependence. Put the $$ into solar, no hurry on the charger side. Give yourself time to learn more. You can get two ProMariner or Sterling 60A units, they are highly recommended, too.


Wiring a new charger From Maine Sail:

http://forums.sailboatowners.com/ind...5/#post-880275
and
https://marinehowto.com/installing-a...ttery-charger/

IMPORTANT Advice on these charger settings: Electrical Systems 101


Good luck, you have a head start on many of us, system-wise.
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Old 30-05-2019, 13:20   #6
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Re: No big battery chargers?

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Originally Posted by a64pilot View Post
AGM will initially accept much higher rates than flooded, but even with AGM the total time to fully charged isn’t much different.
https://marinehowto.com/how-fast-can...ry-be-charged/
Good link.

It shows many things, including that using 0.4C charging rate on a 50% discharged 105Ah battery (42A constant current rate on a 12V 105Ah battery) took 20 minutes to change from constant current bulk charging to constant voltage absorption charging.

It also shows that charging at half that rate, 0.2C, 21A, took 1ľ hours to reach absorption charging.

The charger size is only a factor during the bulk charging. A larger charger will only decrease the bulk charging time and have ZERO effect on absorption or float charging.
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Old 30-05-2019, 13:44   #7
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Re: No big battery chargers?

Having automatic temp compensation on the charger would give you longer battery life. With AGMs it is more important that with wet lead, where you can always top up electrolyte if you've been overcharging.

AGM's can charge at 1/4C without shortening their longevity (in general) so if you have 750Ah of batteries, and you are able to restrain yourself to a 50% depth of discharge, in theory then you'd only be playing with a need for 375Ah of charging, and a 100A charger would do that in 4 hours more or less. Would it be worth replacing things just to cut an hour or two off that? Depends on how you charge.

But having a charger that has no presets can actually be a GOOD thing. Every battery maker has slightly different optimum charge protocols, and having to program the charger to match those correctly is what you REALLY want to do for optimum life.

If the maker says "charge at 13.8" but your charger is set to 13.9, and a lack of temp compensation pushes that to 14...the little numbers can add up. How much that affects battery life is (IMO) still more of a marketing pitch than a solid general finding. Personally, I'd rather set the charger's profiles to exactly what the battery maker says is OPTIMUM not just "acceptable" and that would include temp compensation. Considering the way battery prices keep going up...you know.

And that has to be balanced against the wallet: Good new equipment and installation never is cheap. There's something to be said about "If it ain't broke, don't fix it."
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Old 30-05-2019, 14:12   #8
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Re: No big battery chargers?

Wow, all good and quick input. I have some reading to do.

Stu, as for my usage my boat is in the Caribbean and my wife and live off the grid for 3 to 4 weeks usually, then plug in at a marina for a while for various reasons. I never get SOC back to 100% while off the grid (measured by Balmar SmartGauge). Also my charger doesn't seem to want to push me up to 100% (even on shore power) - stops at 93% - and I think that's because of how I set the temp compensation. The higher it is set the less juice goes to the batteries. I'm a bit reticent to push it harder and overheat the batteries - just don't know right strategy with this so taking he safe route. I can get to 100% with enough time motoring and the alternator doing the charging work (but we avoid motoring). I follow the general rule of running down to 50% SOC and charge back up to ~85%. We think we have maybe two more years of this lifestyle then will be back to our home port in New England. There we're at a marina a lot, off grid for several ~one week voyages, and one 3-4 week voyage each summer. I'm less concerned about this entire topic there. I probably have a few more Newport-Bermuda trips in me, so that's ~5 days each way burning batteries 24/7 and no motoring.

Solar - I know, I know. And as a techie/mechie geek I'd like to do it, but I don't see a way to easily get enough panels on my boat without building an arch on the stern and messing up the prettiness of my old sort-of classic. If I was planning a circumnavigation I'd certainly go solar. Without those big plans I'll have to be content running my generator during this phase of our cruising life.
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Old 30-05-2019, 14:23   #9
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Re: No big battery chargers?

Quote:
Originally Posted by jr_spyder View Post
I never get SOC back to 100% while off the grid (measured by Balmar SmartGauge). Also my charger doesn't seem to want to push me up to 100% (even on shore power) - stops at 93% - and I think that's because of how I set the temp compensation.
According to the Lifeline manual: "If the recharge is insufficient, the battery's state of charge will gradually "walk down" as it is cycled, resulting in sulfation and premature failure."
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Old 30-05-2019, 14:55   #10
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Re: No big battery chargers?

With the controls on the Trace I do set the bulk and float to exactly what the battery spec asks for, with a quirk. The spec for the Trace says set the voltages with the temp knob at 60 degrees F. Then once the voltages are set adjust the knob to the expected ambient temperature and the voltages will be adjusted accordingly. Makes sense, but here's the quirk. With the temp knob at 60 I can not get the voltages high enough for the spec on my AGMs. So I turn the temp knob down a bit (lets say 50, I don't remember exactly) and that lets me get up to the right spec voltages. So I'm cheating. Then I adjust up the temp knob by the same delta as needed. So in this example I'd set the temp knob to 80 if I expect ambient temps to be 90. Sounds logical, but I might be all wrong. This reduces charging voltages by a bit, and why I think my charger won't push the batts up to 100% SOC. I know this can reduce battery life.

Not having automatic temp compensation is actually frustrating me a bit, especially since I have to do some guessing as above. Maybe it doesn't matter all that much and I should stop obsessing for a better charger system. But I need at least one system on the boat to obsess over at any given time!
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Old 30-05-2019, 15:27   #11
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No big battery chargers?

You only expect two more years on the boat, donít spend money needlessly.
If your cycling between 50% and 85% anyway your most likely going to buy another bank in a year or so, but thatís a lot cheaper than new inverter / chargers etc.
Next time do NOT buy AGMís to short cycle them like that, your wasting money twice, first they cost more than flooded, and secondly they wonít las as long as flooded being cycled like that.
When you need batteries, buy good flooded deep cycle golf cart batteries, youíll get much better service out of them, for less money.
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Old 30-05-2019, 16:51   #12
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Re: No big battery chargers?

It's two more years in the Caribbean, then hopefully may more years back in New England with a different usage pattern (marina based, and coastal cruising).

My next battery replacement will certainly be something to obsess over.
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Old 30-05-2019, 17:50   #13
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Re: No big battery chargers?

Quote:
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My boat has no solar or wind (yet). I have an older Trace U2512 inverter/charger (2500 watts, 12v, up to 120 amp charging), a 110 amp Balmar alternator on my engine, and a 120vac/8kw generator with it's own 70 amp Balmar alternator. Have Balmar ARS-III regulators and a ProMariner battery isolator. It's a well put together system, thanks to previous owner(s).

For house batteries I have 6 GC2 six volt AGMs in a series/parallel config giving me 12v and 750 AH.

I don't love the old Trace inverter/charger although I can't say it's not working. While it is "smart" and does appropriate staged charging it's finicky to set up (no pre-programmed charging maps, each stage is set manually) and it does not have a battery temp sensor, just a small knob to set (guess) at expected ambient temps at the batteries.
That old Xantrex / Trace U2512 Inverter / Charger is a nice old 120A charger, but as you've stated, it doesn't have the current technology automatic temperature compensation.

A digital thermometer and manual intervention would permit the charger to satisfy the battery specifications.
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Old 30-05-2019, 17:58   #14
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Re: No big battery chargers?

Quote:
Originally Posted by jr_spyder View Post
>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>


My next battery replacement will certainly be something to obsess over.



Dagnabbit, doesn't seem you have to at all. a64 answered that question in his reply just before yours!


Quote:
Next time do NOT buy AGMís to short cycle them like that, your wasting money twice, first they cost more than flooded, and secondly they wonít last as long as flooded being cycled like that.
When you need batteries, buy good flooded deep cycle golf cart batteries, youíll get much better service out of them, for less money.




AGMs begin to make less and less sense as a product for sailboat house banks as time goes by. We now know what we know now, before back then, right?
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Old 30-05-2019, 18:29   #15
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No big battery chargers?

Marina based means a 60 amp charger is plenty, itís got at least all night to get you fully charged, even smaller than 60 is plenty, I only say 60 cause you have to subtract your house load from that 60.
120 is way more than you need.

However if your going to continue to rely on your generator for charging when away from the Marina, your going to be murdering your batteries.
Nothing wrong with that just know short cycling will reduce the life of them.
So if your going to murder them, pick less expensive ones to murder, and tough ones at that, ones that are hard to kill.
Thatís a golf cart battery, apparently people tend to murder them in golf carts too, so they are tough and hard to kill, and the least expensive battery their is too.

You may consider doing what I did if you still want more battery charger. Leave what you have installed, but also install a 60 amp Sterling Pro charge ultra, that adds 60 to what you now have, and adds a charger that is very modern and has temp sensing etc. So when your in the Marina, just run it, leave the big boy off.
It also gives you a back up, a second charger just in case the old one breaks.
My Magnum will give me 125 amps, my Sterling will give me another 60.
In the morning we wake up and have used about 130 to 150 AH from our 660 AH AGM bank and are usually between 75% and 80% SOC.
If I crank the generator and turn on both chargers, Iím in absorption voltage in 10 min or less, and in 20 or so we are down to less than 125 amps charging, so we only get the use of the big charging for less than 10 min.

But here is I guess the difference, your at 50% SOC and only want to charge I guess for an hour or so?
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