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Old 03-10-2016, 18:47   #1
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Shore power charger

Did a search , can't really find a answer . I have a solid state charger It's a Guest 10 amp. 2 bank , it is not the old transformer type . I'm charging 2 6v Trojan T 105's (series) and a sealed 12v starting batt . The start batt charges up just fine , the Trojans charge up to 12.6 v that's after I let them sit 24 hrs. off the charger. According to Trojan, the Trojans need to cycle 50 to 100 times before they get to full capacity , so I'm not worried about 12.6 as 12.7 is 100 % . Anyhow , my question I was talking to the Trojan tech . and he told me my 10 amp. charger was no good and that I needed at least a 30 amp charger . I have had the 10 amp for over 10 yrs. and was always happy with it . So what do you guys think ? Thanks , mw
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Old 03-10-2016, 19:11   #2
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Re: Shore power charger

The Guest 10A, dual output is only good for 5A @12V on each outlet. So you are charging your series connected T105s at 5 Amps. You've got over 200Ah of storage there, assuming you run it down to 50% SOC, that 5 Amp charging circuit has to put in well over 100Ah. It will do the job eventually, but it's going to take a long time (probably 24 hours at least to reach full charge).
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Old 03-10-2016, 19:57   #3
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Re: Shore power charger

Thanks for the reply Stu . As I understand it you are correct , 10 amp charger two batts. they get 5 amps , ea . 24 hrs .( or more ) for a full charge . I'm good with that , so why would the Trojan guy tell me I need a 30 amp . charger ?
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Old 03-10-2016, 20:26   #4
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Re: Shore power charger

Another consideration is ability to handle loads on the battery. You can only turn on 5A of lighting or whatever before your batteries aren't charging at all. That's 2 or 3 incandescent lights. I'm using 8A of an evening, and that's with mostly LED and flourescent lighting. Have a couple of incandescents for the warm light.

The recommended charger size for the Pronautic I just bought is partly based on boat size, and the above is why.
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Old 03-10-2016, 21:15   #5
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Re: Shore power charger

If you've got current draw while you're charging then you have to discount this draw. Fridge, 3 amps, computers/phones/ chartplotter on anchor watch 1 amp, tv/sound system 4 amps, interior lights led 2.5 amps tungsten 8 amps, water pressure pump .5 amp and that's per hour etc etc. even an idle inverter sucks power. Do an energy audit and then deduct that current draw from your charger. This will reduce the available charge and increase the time needed to recharge the batteries.
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Old 03-10-2016, 21:28   #6
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Re: Shore power charger

Trojan states a 10 to 13% charge rate which on a pair of T-105s is 22.4 amps to 29.12 amps

They also spec a 14.8 absorption voltage.

Get a temperature compensated hydrometer and use it before you declare 12.6v = 100% charged

When you start cycling these things deeply an adequate charging source will be required to get a good cycle life from them.

When the new charger first drops to float voltage, bust out the hydrometer again and prepare to curse loudly.
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Old 04-10-2016, 02:17   #7
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Re: Shore power charger

Mark I have a 40 amp xanerex truecharge in good condition for sale $115.
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Old 04-10-2016, 10:05   #8
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Re: Shore power charger

Thanks for the thoughts guys , I never really thought about stuff running while charging . Probably because we don't really , we also have very little in the way of draw , no reefer and I have converted over to LED's . When I referred to 21.6v soc I didn't mean that was 100% Trojan says 12.7 is 100% after 50 to 100 cycles .
A temp . controller hydrometer ? I'll look into that . 10 to 13 % charge rate that sounds like why the Trojan guy was talking about a 30 amp charger .
Andy thanks for the offer on the charger . but I would prefer to buy new .
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Old 04-10-2016, 12:44   #9
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Re: Shore power charger

Sure Mark no problems, and good luck
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Old 04-10-2016, 19:42   #10
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Re: Shore power charger

Quote:
Originally Posted by andyft View Post
Mark I have a 40 amp xanerex truecharge in good condition for sale $115.
Does that include shipping?
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Old 04-10-2016, 20:52   #11
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Re: Shore power charger

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Originally Posted by markwesti View Post
A temp . controller hydrometer ? I'll look into that .
The OTC 4619 has a little thermometer on the base telling you how much to add or subtract from the reading on the float.

Save the box it comes in to protect it.

Might not be totally accurate as far as actual specific gravity goes, but useful compared against itself to compare to baseline full charge readings when battery(s) are new.

When charging, the center cells get warmer than outside cells making the thermometer more important for an accurate reading.

Don't bother with the plastic hydrometers that claim to be temperature compensated. Both inaccurate and Imprecise.

If money is no object and accuracy is paramount, google Francis Freas.

Bubbles like to stick to the float and throw off readings.

When cycling them deep, it will take longer than one suspects for specific gravity to max out. Most automatic chargers will need to be restarted after loading batteries to reduce voltage and restarting.

Trojan upped their recommended equalization voltage from 15.5v to 16.2v recently.
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Old 04-10-2016, 23:47   #12
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Re: Shore power charger

Your charger is fine--I ran a 500 amp-hour bank at the dock for two years in Australia with a 6 amp automotive charger, and the batteries were very happy. Its all about daily input vs output--the charger had the capacity to put in 144 amp hours/day, and my average use was about less than 100.
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