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Old 02-09-2011, 14:04   #1
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Please Help - Need Advice on Charging via Solar

I've been living aboard my 43 foot boat for 6 months now. when i moved aboard i purchased new batteries for the system. I have 3 4-D liquid acid batteries which produce about 600ah. I charge these with 400 watts of solar via a c35 xantex controller. the only electricity i really use aboard is my refrigeration system which eats up about 4 amps all day and all night. I live in Hawaii, and start receiving enough solar to run my fridge at 8am. by 10 i am receiving anywhere from 5-10amps of positive solar (this is monitored by my heart interface link 20). every afternoon by 2:30 or so my charger says the batteries are topped off. I check them with a volt meter with the fridge not on at the end of the day and it reads 12.7 volts. the thing that gets me is that the specific gravity stays around 1.2-1.75 indicating the batteries need to be recharged. so i decided maybe i'm not getting enough solar during the day. so i took my batteries in to be charged on shore, and sure enough the batteries specific gravity begins to rise after a day on the charger. so i decided that i would turn off the fridge at night, by 12pm the batteries say that they are topped off but still have the same results. The controllers Bulk charge setting is set to 14.4volts and the float is set to 13.5 volts. right now it is 10am and i am recieving 8amps at 13.8volts. I do not see my charger very often reaching 14.4 volts. could this be the problem? I've checked the solar panels and they all seem to be putting out ~19 volts when the sun is out and not connected to the batteries. does anyone have any insight on this? i would really appreciate it. I'd happily buy a new charger (as my xantrex controller came with the boat when i purchased it and i would guess is about 8 years old) if i knew it was going to solve my issues. thanks for your time, any help would be greatly appreciated.
keao
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Old 02-09-2011, 14:13   #2
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Re: Please help, Need advice on charging via solar

One experiment you may want to try before replacing the controller is to see what happens when you use your system to charge only two of those 4D batteries. The house bank may be too large for the amount of wattage you've got going into the system. In the long run, it may be better to have a 400 AH bank that charges up every day than a 600 AH bank that is never fully charged.
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Old 02-09-2011, 14:25   #3
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Re: Please help, Need advice on charging via solar

remember the batteries store more than you can make in a days time. i8t may take many days to week to "fill em up" as it were, and you use em at same time-- i know i use more then i replace daily..that makes bateries seem old. took me 3 months to figger my batts were almost dead and replace em. took longer to figger my 8d for starting was dead and replace it.
could well be that all is good, but , as i do, you use more than you make and replace.
i add my amps in and i add my amps out. i have to do this so i know where i stand.
remember, the regulator regulates input to batts to the limit on the regulator.
if is a 20 amp regulator, will only allow UP TO 20 amps in.
if your panels arenot always in sun, could be a lot less than what the regulator sez.
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Old 02-09-2011, 14:44   #4
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Re: Please help, Need advice on charging via solar

Recieving only 10 amps in, plus the 4 amps out you say, so only 14 amps input from 400 watts of solar in the sun. Sounds pretty low, what is your solar controller rated for? Did you add panels but never upgrade the controller at the same time?
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Old 02-09-2011, 14:46   #5
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Re: Please help, Need advice on charging via solar

You might have better luck with an MPPT charge controller such as Blue Sky.
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Old 02-09-2011, 14:56   #6
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Re: Please Help - Need Advice on Charging via Solar

Also keep in mind that measuring the battery's voltage is not a very good indicator of its state of charge when its been used in the past day or so. It takes a battery a while to come to a "resting" voltage. Just cutting all the loads and then taking a voltage reading is always going to be somewhat off the mark of the true state of charge.
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Old 02-09-2011, 14:59   #7
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Re: Please help, Need advice on charging via solar

The regulator should not consider the batteries are charged until the batteries have been kept at the absorb voltage (14.4) for a couple of hours or so. If this is not the case something is wrong.
If the parameters are adjustable as they are in many regulators, has the absorb time been set very short? This would explain the symptoms.
14.4 and 13.5V are a bit low for the bulk and float points of a flooded battery. Raising these points would also be helpful, but my hunch from your description is the main fault is a short absorb time.
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Old 02-09-2011, 15:08   #8
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Re: Please Help - Need Advice on Charging via Solar

I understand that the C-35 does not have a heat sink on the output transistors and so may not have great reliability under heavy usage.
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Old 02-09-2011, 15:16   #9
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Re: Please Help - Need Advice on Charging via Solar

In Hawaii with 400 watts of solar panels you should be getting more amperage than you're reporting in bright sunlight.

One possibility is to get a better MPPT controller and, at the same time, wire the panels in series rather than parallel (as it seems they are now), so that the MPPT controller receives upwards of 34 volts maximum.

With these changes you could expect higher amperage output both in sunlight and in partial shade.

Bill
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Old 02-09-2011, 15:17   #10
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Re: Please Help - Need Advice on Charging via Solar

I propose an experiment to help determine if it is a case of bad regulator (bad adjustment maybe?) or a case of power consumption exceeding available supply.

Just return to basics and remove the controller from the circuit for one day and connect solar panels output directly to battery bank. Keep power consumption on usual levels and monitor the bank voltage with a multimeter throughout a sunny day to see if the voltage ever reaches the 14.4V - 14.8V. If it does, there is enough installed power and the regulator is suspect.

You wrote that the output from panels is 19V, so they will not be working at their maximum power point in this config, but they will be close enough. Take care not to go higher than 14.8V as excessive gassing will result. If you do not have blocking diodes built in panels terminate the test at the end of day and disconnect the panels from the bank even if the voltage was not reached, as they will discharge the bank overnight.
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Old 02-09-2011, 15:27   #11
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Re: Please Help - Need Advice on Charging via Solar

Quote:
Originally Posted by keao View Post
every afternoon by 2:30 or so my charger says the batteries are topped off I do not see my charger very often reaching 14.4 volts. could this be the problem?
I have looked at the manual for your regulator. The absorption time is not adjustable, but is fixed at 1Hr.
You should see 14.4V maintained for 1hr before the regulator indicates the batteries are charged. If it indicating the batteries are charged (solid green light) its dropped back to the float voltage. If its doing this before the bateries have been held at 14.4V for 1 hr then its defective.
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Old 02-09-2011, 15:50   #12
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Re: Please Help - Need Advice on Charging via Solar

My turn :lol: The situation you have described is seen a lot in motorhomes in Australia that live on the road full time. The problem is the controller drops into float mode too early and the batteries virtually stop charging. I'd avoid going the series panel connection method because you are on a boat and high DC voltages don't mix well with wet skin so the potential for a nasty accident is just too great for any benefit you may achieve.
My first recommendation would be to reset the float voltage to 14.4v, this way the batteries will charge all the time the sun shines but not over voltage charge so the batteries won't get damaged. Keep an eye on the water levels and specific gravity of the acid, you should see an improvement within a few days. The batteries may use a little more water set up this way but they will live a lot longer.
WARNING!!! If you decide to stop living full time on the boat and turn all the loads off from the battery set the float voltage back to 13.6v or you will toast the batteries after a week or so.
Hope this helps

T1 Terry
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Old 02-09-2011, 16:14   #13
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Re: Please Help - Need Advice on Charging via Solar

everyone thank you for the advice thus far, T1 Terry, i think i will start with your advice and work my way from there up the list. I have tried a few of the other scenarios. will be in touch soon. thank you
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Old 03-01-2016, 19:41   #14
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Re: Please Help - Need Advice on Charging via Solar

Hi captain, to am refitting my house/ starterror configuration. We life and cruise the Miss. Sound to Panama city area.I have a 1000th pure sine inverter with 3 of yet large estate deep cycle bats Sam's Club had to offer.Also have a1/all/2/off switch. However my tech/electrical abilities aremail not so much.I will follow you closely.GOODS LUCK!
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Old 03-01-2016, 19:44   #15
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Re: Please Help - Need Advice on Charging via Solar

PL I WILL PRO OF READ A GOODS BIT CLOSER!
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