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Old 02-11-2019, 09:42 PM   #11
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Default Re: is there a solar charge controller that can do this?

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Originally Posted by PaulDavis View Post
I am wondering if there's a charge controller that can use a measurement point like the Trimetric, understand that we're actually drawing power from the system while it is charging, and increase the power delivery from the panels while this is happening.

Specific case in point: charge controller is delivering 150W (from 540W of panels) at 10A to the batteries. Trimetric shows 9.2A being delivered ... we're good. Now plug in a 135W laptop charger. The charge controller does NOTHING different. I'd like one that understands what has just happened and responds by increasing the delivery from the panels.

Does this exist?
There are charge controllers that use a remote battery monitor so that the charge controller can sense the voltage at which it is charging the battery directly at the battery. That helps solve the problem of voltage drop in the cabling leading from the charge controller to the battery. If there was a load pulling the voltage down I would expect the charge controller to increase the voltage in the system if it had enough supply (i.e., enough sun on the panels if it is solar PV) so that the voltage at the battery measured what it expected at that point in the charge cycle.

Someone in the thread mentioned a charge controller that has separate "load" connections from the battery charge/discharge connections. That sounds like it would make the charge controller even smarter with respect to battery state versus system state.

Wizardry usually has its price, so there are probably tradeoffs in terms of the component cost to have a smarter system that you would weigh against the payback either in extended battery bank life or more usable power on the daily cycle.
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Old 02-12-2019, 01:51 AM   #12
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Default Re: is there a solar charge controller that can do this?

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Originally Posted by OrioN View Post
If the one you have the Morningstar Tristar MPPT60, it is custom programmable and can do what you require.

Read the manual to learn how you can create your desired algorithm with the MSView program utility.
I have the manual. I see how to reprogram the bulk/absorb/float stuff. But that's not what I desire. I'm quite happy with the current programming.

I just want a solar array that can deliver the correct charging current to my AGM's (given their current SOC) but ALSO deliver more to the system if there is a current draw other than the batteries.
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Old 02-12-2019, 01:52 AM   #13
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Default Re: is there a solar charge controller that can do this?

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The tricky area is pulling low / moderate currents when the battery is in that 80+% SOC area. The charger thinks that it is doing its job supplying small currents for the ABS and Float stages, and the load can be sufficient that SOC is actually decreasing.
Precisely.
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Old 02-12-2019, 02:21 AM   #14
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Default Re: is there a solar charge controller that can do this?

Reading the Morningstar MPPT manual, it would appear to only be a VOLTAGE controlled/sensing device (with one overcurrent exception).

So it's going to be putting out as much current as it can for the voltage levels it's trying to achieve.
The only current *limiting* it does is if the battery is accepting more than 130% of the controller's rated output.
At which point the controller will shut down for 10 seconds. And blink LEDs at you.

So if the unloaded battery is accepting less than full-rated current due to a high state of charge, AND you turn on your load, the controller's current output WILL increase to keep the battery up at the desired voltage, to the limits of its output rating. If it achieves that goal (the battery reaching the float stage, for example), then you could say that all of the controller's output is actually going to the load ... and the battery's just along for the ride.

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Old 02-12-2019, 02:24 AM   #15
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Default Re: is there a solar charge controller that can do this?

Hi Paul,
Perhaps have a look at an Enerdrive DC2DC+ epower charger? Multi stage, multi source with MPPT.
Apparently when in float stage it can support additional loads like lighting or refrigerators, effectively using the charger as a dc power supply.
It may also be available under the Kisae name?
I don't know enough about it; it may satisfy your query, but hope this is of some help
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Old 02-12-2019, 02:26 AM   #16
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Default Re: is there a solar charge controller that can do this?

We have the Sunsaver MPPT which has a 'load' connection.
Says it provides 'battery' power for lights, etc.
We don't have anything connected there in our van.

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Old 02-12-2019, 12:28 PM   #17
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Default Re: is there a solar charge controller that can do this?

I have both the TriMetric meter and charger. I’m not sure I understand what you are saying the Morningstar does/doesn’t do, but the TriMetric shows me when excess solar is available for other purposes when the batteries are not taking in all that is available.
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Old 02-12-2019, 02:04 PM   #18
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Default Re: is there a solar charge controller that can do this?

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I have both the TriMetric meter and charger. Iím not sure I understand what you are saying the Morningstar does/doesnít do, but the TriMetric shows me when excess solar is available for other purposes when the batteries are not taking in all that is available.
I mostly want the reverse. I want the charge controller to know when the panels can deliver more than the batteries should receive AND there's a load above and beyond charging that can use the extra.

Eg. batteries at 85% SOC, charge controller decides to deliver 13.0V at 10A to keep the batteries healthy. Now add a load (e.g. a 135W laptop charger, or a refridgerator or whatever) ... the charge controller can deliver a lot more power "into" the system without harming the batteries, while still continuing to charge them at the optimum rate.

But the charge controller doesn't know this because the only measurement it has is voltage in the system, and these loads don't change the voltage sufficiently for the controller to do anything differently. If it watched the current arriving at the batteries, like the Trimetric does, it would know that something else is sucking power from the system, and it could increase its output accordingly.
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Old 02-12-2019, 02:15 PM   #19
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Default Re: is there a solar charge controller that can do this?

It seems like you have a fundamental misunderstanding of how lead acid charging works. These solar controllers, and most chargers in general are voltage sources with current limits. The solar is limited to what the panels are producing, and charger is limited by its circuitry. Charging lead acid from a charger that is less than the banks max charge current (which is usually the case) is done as follows.

Connect charger (or sun rises). Charger outputs its max available current. Voltage is wherever on the charge curve that current corresponds to. SOC will rise as the battery charges and so will charge voltage. At some point the batteries acceptance will drop below the chargers output. At that point the charger will hit its voltage setpoint, and the current will drop. The current will continue to drop while voltage holds steady until the chargers absorb timer (or return current for shunt aware units) is reached. If the charger is in absorb mode, and the voltage is below the absorb setpoint, this means the loads and the batteries acceptance are greater than the chargers output.

Once absorb is complete the charger will change its voltage setpoint to the float level. Usually around 13.3-13.5V. Note that many controllers prematurely go to float, causing unnecessary battery capacity loss.

I do not believe that the solar controller you are using is return current aware. For example, my outback solar controller interfaces with my battery monitor. It is set to charge until the return current drops below 1% of C at the absorb voltage.

If return current feedback is not an option, I would suggest setting a long absorb timer. For full-time live-aboard vehicles, I would suggest at least 4 hours, likely up to 6. Monitor your return current during the absorb cycle. If it doesn't drop below 1% during a typical day, extend the timer.
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Old 02-12-2019, 02:15 PM   #20
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Default Re: is there a solar charge controller that can do this?

The problem is how to determine how much amperage the panel could deliver. Easy to determine how much power the controller is sending to the battery. The difference between the two amperages is what you are trying to measure.

How can you determine the maximum output available from the panel when battery is full?

If you knew the difference how would you change your electrical usage during the time excess power was available? What else would you power?
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