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Old 11-01-2014, 06:23   #1
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When Does Charging Voltage Start To Matter?

I've been toying around with some small wind and water generator stuff. And by small I'm talking peak ~1amp @30 volts kind of stuff. Cheap motors, easy to work with, if they break you're out $20 and an afternoon.

For my "real" charging stuff (panels, alternator, AC charger) I dial everything in to the proper voltage for my batteries (T-105's, ~500AH worth).

What's the actual material impact of introducing something like a 30v potential with a low amperage?

I know it's not great, but similar to how you can basically have small solar panels hooked up sans charger because tiny amperages don't cook big batteries, what happens with voltage?
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Old 11-01-2014, 06:29   #2
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Re: When Does Charging Voltage Start To Matter?

Nothing, Eric. It will not matter.

We have now spent YEARS with no controller between 630 W of solar panels (17 V nominal) and 880 Ah in our battery bank. No bad result.

Once the voltage gets to about 14, we switch off a panel and then continue to do so with the rest.

In the case of your experiments, don't worry about it. The batteries will not notice those amounts.
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Old 11-01-2014, 06:33   #3
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Re: When Does Charging Voltage Start To Matter?

At one stage I had them wired in series so it was 34V, and the batteries just took it without any issue.

However, I changed the system to parallel to make it easier to drop a panel or two out of the circuit, rather than a complete circuit.

Panels are much cheaper than regulators but you have to live aboard and pay attention......
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Old 11-01-2014, 06:34   #4
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Re: When Does Charging Voltage Start To Matter?

51V at one point in series.
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Old 11-01-2014, 08:08   #5
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Re: When Does Charging Voltage Start To Matter?

If you hook a wind/water generator that can supply 30V at 1 amp to a 12 V battery bank, it will load down the generator to about 13-14 V and will supply a bit more than an amp.

You could install a MPPT controller in the circuit. It will let the generator operate at 30 V and convert its output to the 13-14 V that your batteries require. You will then get about 2 amps. But that controller is going to cost $100 or so.

If your solar system operates with 34 V panels you might try paralleling the generator with your panels and see what happens. Might work.

David
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Old 11-01-2014, 08:49   #6
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Re: When Does Charging Voltage Start To Matter?

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Originally Posted by Jimbo485 View Post
We have now spent YEARS with no controller between 630 W of solar panels (17 V nominal) and 880 Ah in our battery bank. No bad result.


//////////
Panels are much cheaper than regulators but you have to live aboard and pay attention......
I agree with Jim.
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Old 11-01-2014, 09:48   #7
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Re: When Does Charging Voltage Start To Matter?

Is 1 amp enough to be worth it? Or is this just an experiment, just for fun?
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Old 11-01-2014, 10:37   #8
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Re: When Does Charging Voltage Start To Matter?

1 amp at night would be worth it for me.
I only have solar and its the wee small hours with the fridge trying to be a freezer taking 4 amps so 1 amp in is 1/4 of my total draw (less loss, etc for the pedants)


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Old 11-01-2014, 13:13   #9
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When Does Charging Voltage Start To Matter?

Quote:
Originally Posted by Jimbo485 View Post
At one stage I had them wired in series so it was 34V, and the batteries just took it without any issue.

However, I changed the system to parallel to make it easier to drop a panel or two out of the circuit, rather than a complete circuit.

Panels are much cheaper than regulators but you have to live aboard and pay attention......
You obviously do not understand or appreciate that solar panels are primarily current sources , hence you can connect 1000000000V panels to the battery , and the " battery" will take it , until of course it needs no more current and then...

Efficiency of course is another matter entirely as a study of the V/I curves will illustrate

Dave
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Old 11-01-2014, 13:29   #10
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Re: When Does Charging Voltage Start To Matter?

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Is 1 amp enough to be worth it? Or is this just an experiment, just for fun?
We've got some big passages coming up (like 3k miles, then lots of shorter but still beefy ones) in a few months. I don't want to drop real money on a water generator, but I'm comfortable rigging a DC motor to an old outboard prop.

1-2 amps doesn't seem like much on the surface but that's 24-48 amp hours a day, which is what one of my big 135 watt panels would put out in 2-4 hours of full sun.

Our watermaker sucks down 24AH a day, so if I can rig this thing it will basically neutralize that load.
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Old 11-01-2014, 14:22   #11
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Re: When Does Charging Voltage Start To Matter?

if you feel it is going to be worth it just do it
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Old 11-01-2014, 14:31   #12
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Re: When Does Charging Voltage Start To Matter?

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1 amp at night would be worth it for me.
I only have solar and its the wee small hours with the fridge trying to be a freezer taking 4 amps so 1 amp in is 1/4 of my total draw (less loss, etc for the pedants)


Mark
Mark,
To take care of your nighttime loads, get MOON panels.
Eric,
I rigged up a permanent magnet motor (purchased at Minney's) to a braided line terminated in a 3 foot long ss rod.
That was connected to the 3 blade prop from a 10 hp outboard.
The other end to the motor which I mounted on a bracket on the transom of our LN35.
I connected it to the battery switch through a 40 amp Schottky diode.
At 6 knots, it generated about 5-6 amps and slowed the boat around a half knot.
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Old 11-01-2014, 14:42   #13
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Re: When Does Charging Voltage Start To Matter?

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Originally Posted by rebel heart View Post
We've got some big passages coming up (like 3k miles, then lots of shorter but still beefy ones) in a few months. I don't want to drop real money on a water generator, but I'm comfortable rigging a DC motor to an old outboard prop.

1-2 amps doesn't seem like much on the surface but that's 24-48 amp hours a day, which is what one of my big 135 watt panels would put out in 2-4 hours of full sun.

Our watermaker sucks down 24AH a day, so if I can rig this thing it will basically neutralize that load.
Rebel,

At just about anything below 99% SOC your battery voltage will never get above 14.4V with a 1A source. However if you kept that 1A source going until the SOC needed less than 1A to not exceed 14.4V then yes you would begin pushing over the safe voltage level.

I can tell you that when allowed to become "CHOCK FULL" by unregulated sources:

*220Ah's of 6V Lifelines can be pushed over 15V with a 12W solar panel or about 0.7A, when CHOCK FULL...

*A 125Ah group 31 deep cycle, by US Battery, can be pushed over 15.5V when CHOCK FULL with a 12W solar panel...

*400Ah's of Trojan L-16's require just 0.1A to maintain 14.4V when CHOCK FULL....


The key in all these scenarios is "chock full" or sources allowed to keep pumping in current until the battery simply can not take any more........
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Old 11-01-2014, 17:22   #14
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The key in all these scenarios is "chuck full" or sources allowed to keep pumping in current until the battery simply can not take any more........
I always thought it was "chock" full.
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Old 11-01-2014, 17:36   #15
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Re: When Does Charging Voltage Start To Matter?

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You obviously do not understand or appreciate that solar panels are primarily current sources , hence you can connect 1000000000V panels to the battery , and the " battery" will take it , until of course it needs no more current and then...

Efficiency of course is another matter entirely as a study of the V/I curves will illustrate

Dave
At some point they find out the difference between the red- and the black- wires and now they can tell anything about impedance matching, optimal charge curves and yes, even cost:benefit ratios
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