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2oldman

New Mexico

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Posted: 01/14/20 02:45pm Link  |  Quote  |  Print  |  Notify Moderator

twodownzero wrote:

My controller knows how large my array is and what kind of batteries (conventional lead acid) are attached to it.
My Outback controller doesn't ask how big the array is, but it does ask for the battery bank size in ah.

MrWizard

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Posted: 01/14/20 04:21pm Link  |  Quote  |  Print  |  Notify Moderator

DarkSkySeeker wrote:

2oldman wrote:

Yeah, that's why it's there.

So - here's a silly example.

If I had a big array and one battery, the charge controller would limit the 50+ amps to perhaps 4 amps to the one battery?


No..if it did, I would change controllers

DOES your converter limit charge to 4 amps
DOES YOUR ALTERNATOR LIMIT CHARGE TO 4 AMPS

It would take days to recharge the batteries

Charge rate is applied voltage versus battery resistance

My converter can do 75 amps

My previous RV I installed over 600+ ways of solar panels


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pianotuna

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Posted: 01/14/20 10:59pm Link  |  Quote  |  Print  |  Notify Moderator

During the day time, if I want to harvest some free power, after the battery bank is full, I'll use the inverter to run the water heater.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

2oldman

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Posted: 01/16/20 02:45pm Link  |  Quote  |  Print  |  Notify Moderator

MrWizard wrote:

DOES your converter limit charge to 4 amps
DOES YOUR ALTERNATOR LIMIT CHARGE TO 4 AMPS
Obviously not. I assumed he meant 'during the course of charging' it would get to a point where the current was limited.

Not that he'd actually want to set something like that.

beemerphile1

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Posted: 01/16/20 07:57pm Link  |  Quote  |  Print  |  Notify Moderator

To visualize it, think of it this way; the current isn't pushed into the battery, the battery sucks it in. When the battery is full and stops sucking, the current stops.


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ktmrfs

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Posted: 01/16/20 08:34pm Link  |  Quote  |  Print  |  Notify Moderator

under ideal conditions most flooded cell lead acid batteries will have maximum cycle life if the intial charging current is limited to about C/10 C=rated AH. However, you can still get very long life cycle even charging at an initial C/2 to C/4 rate. The charge rate will decrease as the battery bank gets near full charge, starting to taper at when the battery is about 70% charged.

So... a initial 50A charge rate isn't excessive for a couple of 12V or pair of 6V golf cart batteries.

what controls the current going into a battery is the source voltage, battery voltage, battery internal resistance, the current the source can supply and the charging algorithm.

On a deeply discharged battery on initial charge the charging current will be limited by either the source max current or the battery internal resistance. Generally the max source current is the limit.

* This post was edited 01/18/20 09:55am by ktmrfs *


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2oldman

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Posted: 01/17/20 10:42am Link  |  Quote  |  Print  |  Notify Moderator

..

Almot

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Posted: 01/19/20 05:46pm Link  |  Quote  |  Print  |  Notify Moderator

DarkSkySeeker wrote:


If I had a big array and one battery, the charge controller would limit the 50+ amps to perhaps 4 amps to the one battery?

Max current accepted by battery depends on how deeply it is discharged. Could be a lot more than 4 amps for one 100AH battery - at the beginning. Then current drops as it's nearing the Full. Then it jumps up again when you turn some powerful device On - solar outputs the energy directly into the device.

Controller controls volts, differently on different stages of charging. When it controls volts, amps (= charge flowing into battery) are also affected.

As long as it doesn't interfere too much with RV aerodynamics, there is no penalty for having a bigger solar than you think you need, but there are often benefits.

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