Battery cutoff with solar

My bad, Don Piano - didn't know about this feature of Xantrex C35. It can be "configured" as a load diverter. But then it will work only as a diverter. Yes, C35 is a good one. Reliable, adjustable and you don't need a laptop to set it up.

What I meant is that manufacturers of low-end models like slapping a low-power auxiliary output on. Not too useful feature, this isn't the same as load diversion.

pianotuna wrote:
My controller, alas, does not do diversion loads. So if the battery bank is bursting full, I turn on the electric water heater for 15 minutes. That causes the panels to work hard. *grin*

What a nifty idea. I've always hated "wasting" all that free solar energy out there.

My wimpy 1000W inverter can't handle the water heater, but I know it can run the 260W frig. Same idea, just sort of inverted heat-wise. So I'll try running that on 700W of solar during the day after the batts are fully charged.

And try not to forget to turn it back to propane before night falls.

pianotuna wrote:
Hi grizzzman,

From the owner's manual

"dump loads and consume power from the battery bank to prevent the battery bank from being overcharged by the renewable energy source(s) (e.g.wind turbine, hydro, and solar).

7. Connect a cable from the controller’s other terminal marked COMMON NEGATIVES to the negative terminal of your DC diversion load. This is the black wire marked “7” in Figure 3 below.

8.Connect a cable from the controller’s terminal marked PV+/LOAD+ to the positive terminal of the DC diversion load. This is the red wire marked “8” in Figure 3 below."

grizzzman wrote:

C35, C40 and C60 charge controllers can be used as a charge, diversion, or load controller.

"Or" you would need to buy two for charge and diversion.

Hi ya pianotuna

From the same Manuel

Right out of the Manuel "The C35/C40/C60 (C-Series) controllers can be used with 12-volt, 24-volt, or 48-volt DC systems (depending upon model) as Charge Controller or a Load Controller."

Important: The C-Series controller cannot operate in more than one function at the same time. If several functions are required in a system, a dedicated controller must be used for each function.

Hi grizzzman,

From the owner's manual

"dump loads and consume power from the battery bank to prevent the battery bank from being overcharged by the renewable energy source(s) (e.g.wind turbine, hydro, and solar).

7. Connect a cable from the controller’s other terminal marked COMMON NEGATIVES to the negative terminal of your DC diversion load. This is the black wire marked “7” in Figure 3 below.

8.Connect a cable from the controller’s terminal marked PV+/LOAD+ to the positive terminal of the DC diversion load. This is the red wire marked “8” in Figure 3 below."

grizzzman wrote:

C35, C40 and C60 charge controllers can be used as a charge, diversion, or load controller.

"Or" you would need to buy two for charge and diversion.

pianotuna wrote:
Hi Almot,

I said good--not expensive. The venerable Xantrex 35 amp PWM 12/24 volt controller does diversion loads and it is $99 bucks on Amazon. It has adjustable voltage set points and provision for a battery bank temperature sensor.

I think MrWizard may be using one.

C35, C40 and C60 charge controllers can be used as a charge, diversion, or load controller.

"Or" you would need to buy two for charge and diversion.

Hi Almot,

I said good--not expensive. The venerable Xantrex 35 amp PWM 12/24 volt controller does diversion loads and it is $99 bucks on Amazon. It has adjustable voltage set points and provision for a battery bank temperature sensor.

I think MrWizard may be using one.

Joel_T wrote:
with a big enough load all of the solar panels amp output would make it to the battery,

"To" the battery but not "into". This semantics only makes simple things difficult.

Look at it this way:
Post-controller current is consumed by either hungry battery or loads (or both).
When battery is full, it needs no current.
No load, - the same.
Result: no current from controller.

Like Don said, there exist some expensive controllers that will divert the solar energy to auxiliary loads in this case, i.e. the loads that you wouldn't turn on otherwise.

Now, if battery is full but you apply load, the post-controller current goes to the load. Not to the battery. Because the battery is full and when it's full, it doesn't need any charge.

If you apply "big enough load", at some point the load demand will exceed the controller output, so the load will start sucking the charge out of the battery. Because solar alone won't keep up with the load demand.

In reality it's a little more complicated, but the bottom line is - increasing the load won't result in the increase of current into the battery. This is a variation of your earlier question on how the increased drain would "help" with battery in storage on solar. Not gonna happen :)

My controller, alas, does not do diversion loads. So if the battery bank is bursting full, I turn on the electric water heater for 15 minutes. That causes the panels to work hard. *grin*

pianotuna wrote:
Hi Joel,

You may send more amps post controller--but they will be consumed by the load you have placed on the electrical system. So no extra amps will go into the battery. In fact the load may be draining your battery.

Some (good) PWM controllers come with a diversion load feature so that once the battery bank is full the "extra" energy can be sent to (for example) a 12 volt element for the water heater.

Hi, thanks for the clarification.

I missed Almot's point I guess. I, or Ralph really, was just saying that with a big enough load all of the solar panels amp output would make it to the battery, whether or not it was consumed by loads after the battery was of no value, only that current was measurable as you say, post controller.

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