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Old 25-11-2014, 20:52   #1
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Battery Charger Output Amperage

When refitting our boat I installed a 10 amp ProMariner ac battery charger. The original plan was to have solar panels and wind generator but as time was running out we had to put these items on the "later list". Instead we purchased a Honda 1k generator to run battery charger when we are on the hook. This has worked but feel we are under loading the generator (we also use generator for charging laptop, ipad and phones which are all minimal loads) and not charging the batteries efficiently. Refrigeration is our big power hungry device on the hook. House batteries are two six volt in series with 440 ah capacity total.
Did some number crunching and figured 120 vac @ 8 amps ac is 960 watts and that is enough power to output 12 vdc @ 80 amps dc not counting losses.
If these numbers are correct I am thinking I should install a 12vdc charger @ 60 amps dc. Output of ac generator is 15 amp ac so do not want to exceed that output. Any thoughts? Appreciate any help,
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Old 25-11-2014, 21:51   #2
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Re: Battery Charger Output Amperage

First, if you have a Honda EU1000 the max AC output is only 8.3 amps. Constant load 7.5. In simple terms Watts = Volts X Amps in AC or DC power (ignoring power factors, etc). So in simple terms you could use a 1000 Watt charger or 83 amps in theory.

However, you have to look at the max constant load the Honda can take, inefficiencies and losses in converting AC to DC. In practical terms 60 amp charger is the max I would try to run with the Honda and that would be for a unit with a good power factor. Might be safer to go for 50 amps depending on the charger.
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Old 25-11-2014, 23:10   #3
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Re: Battery Charger Output Amperage

Skipmac's numbers look right to me.
A Newmar 80 amp 12 volt charger requires 12 amps at 115 volts. Too much for your little Honda.

A Newmar 40 amp 12 volt charger requires 6.8 amps at 115 volts.
A Blue Sea 40 amp 12 volt charger requires 7.5 amps at 100 volts. Wonder why they rate it at 100 volts?


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Blue Sea Battery Chargers
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Old 25-11-2014, 23:31   #4
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Re: Battery Charger Output Amperage

When running the numbers, remember that you're doing your bulk charging (full output of charger) at something like 13.5 to 13.8 volts. Your 1000 W becomes about 73 theoretical Amps @ 13.65V, and the 900 W continuous rating of the generator is about 65A. Most of the marine chargers are somewhere around 80% efficient, which takes you to 52A maximum charger capacity out of that 1000W generator. A 40A or 50A charger is the largest you'll be able to reliably run from the 1000W Honda, so either one of the units HopCar pointed to would be suitable.
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Old 26-11-2014, 01:02   #5
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Re: Battery Charger Output Amperage

I agree with the 3 responders.
Just another observation: you said you have a capacity of 440 Amp hr; if so, then these are 2 enormous 6 Volt batteries, weighing up to 60 kg each? Or do you have two 6 Volt batteries with a capacity of 220 amp/hr each? Indeed, you can add the voltage when connecting in series, not the capacity.

That being the case (220 amp/hr) maybe a charge rate of 50 Amps is a bit high for vented lead acid battery. Hmm, never seen an AGM with those capacities.
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Old 26-11-2014, 03:32   #6
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Re: Battery Charger Output Amperage

Maximum battery charger capacity is about 40A charge for the eu10 genset. Aside from time, the little Honda really doesn't suffer from the lighter load due to the inversion technology it uses when in economy mode. Some chargers are more efficient than others. One 35 amp charger I looked at had a specified draw of 1080 watts which exceeds the capacity of the eu10, whereas other brands fall below the genset rating at 40A output.
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Old 26-11-2014, 05:40   #7
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Re: Battery Charger Output Amperage

When I bought my boat it came with a Truecharge 40 battery charger and a Honda EU 1000 generator. The generator would run the charger as long as there were no other AC loads.
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Old 26-11-2014, 05:48   #8
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Re: Battery Charger Output Amperage

Quote:
Originally Posted by HankOnthewater View Post
Just another observation: you said you have a capacity of 440 Amp hr; if so, then these are 2 enormous 6 Volt batteries, weighing up to 60 kg each? Or do you have two 6 Volt batteries with a capacity of 220 amp/hr each? Indeed, you can add the voltage when connecting in series, not the capacity.
I wondered about that myself. I have 6 X 6 volt golf cart batteries in my boat. Each one is about 210 amp hours. To get a 6 V 440 amp hour battery would be a very big battery.
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Old 26-11-2014, 05:50   #9
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Re: Battery Charger Output Amperage

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Originally Posted by Reefmagnet View Post
Aside from time, the little Honda really doesn't suffer from the lighter load due to the inversion technology it uses when in economy mode.
Another good point.
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Old 26-11-2014, 05:57   #10
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Re: Battery Charger Output Amperage

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I wondered about that myself. I have 6 X 6 volt golf cart batteries in my boat. Each one is about 210 amp hours. To get a 6 V 440 amp hour battery would be a very big battery.
A pair of Trojan 6V L-16H's are 435Ah's.. I suspect thought the OP has 6V GC2 batteries, so if he has two of them, then he has a 220Ah bank not 440Ah...

As for the charger and EU1000, 40A is the safe bet. You may run some 50A chargers but it is pushing the limits...
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Old 26-11-2014, 06:34   #11
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Re: Battery Charger Output Amperage

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A pair of Trojan 6V L-16H's are 435Ah's..
Had to look up that model. 125 lbs each and an odd format. Approximately 12 X 7 width/length but 16 3/4" tall. That is indeed a big battery.

I hauled around a few batteries that heavy 35 years ago when I was young and foolish but gave up that nonsense when I became older and wiser.
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Old 26-11-2014, 06:45   #12
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Re: Battery Charger Output Amperage

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Originally Posted by skipmac View Post
Had to look up that model. 125 lbs each and an odd format. Approximately 12 X 7 width/length but 16 3/4" tall. That is indeed a big battery.

I hauled around a few batteries that heavy 35 years ago when I was young and foolish but gave up that nonsense when I became older and wiser.
If you have the height they are great batteries and take up less foot print.. While heavy they are much easier to move and carry than any flooded 4D or 8D and have gobs more cycle life too....

I actually do quite a few L16 installations..
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Old 26-11-2014, 09:14   #13
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Re: Battery Charger Output Amperage

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If you have the height they are great batteries and take up less foot print.. While heavy they are much easier to move and carry than any flooded 4D or 8D and have gobs more cycle life too....

I actually do quite a few L16 installations..
Unfortunately height is what I'm short of. Had to modify my battery box to get GC2s to fit.
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Old 26-11-2014, 10:02   #14
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Re: Battery Charger Output Amperage

We have a pair of Trojan T145 Plus batteries for our house bank. Specs say each is 260 ah/20 hrs. They weigh about 75 lbs each. I was adding the two. Is two six volts in series for 12 volts equal to the same 260 ah? This would explain it.
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Old 26-11-2014, 10:08   #15
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Re: Battery Charger Output Amperage

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We have a pair of Trojan T145 Plus batteries for our house bank. Specs say each is 260 ah/20 hrs. They weigh about 75 lbs each. I was adding the two. Is two six volts in series for 12 volts equal to the same 260 ah? This would explain it.

In series you add VOLTAGE

In parallel you add CAPACITY

Two 6V batteries in series = 1 of the batteries 20 hour capacity...
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