controller and shore power or genny

Re: controller and shore power or genny

Assuming the Morning Star controller is firmly and correctly attached to the Battery +/- buses--then you should not need to do anything... If the controller measures the battery voltage and determines more current is needed for charging--the controller will simply add the current (when needed) in parallel with the other charging sources.

If the battery is fully charged, the controller will stop charging (and perhaps go to "float" around set itself to13.6 volts or so) even if the other controller(s) are taking the battery to 14.5 volts or so. No problem/no chance of damage to the controller or other charging systems.

Unless the battery voltage goes too high (> 15.5 volts--which could damage the controller and the battery bank) from overcharging by alternator/AC shore power)... The failing (over) charging source would need to be fixed anyway.

Or you have something else connected (like the tow vehicle battery/electrical system--where 14.5-15+ volts during equalization of the RV battery by the MorningStar controller--which can be too high for a car's electrical system)-I would not worry.

-Bill

Re: controller and shore power or genny

htwheelz67 wrote: »

Thanks Bill.

Today when I did the install I measured the voltage at the junction box (18" from panels) and got 26.07 volts about 2pm, I ran down to the very end of the wires and it measured 26.03 volts, is that my loss?

It is a voltage drop (and not much of one--a good thing).

What you also need to know is the current through those wires...

after connecting to batts around 6pm PSD, with the sun setting my rm-1 meter said 20.66 volts from the panels and 8.6 amps and 12.4 volts charging into the batts.

I don't remember the size/Vmp/Imp and series/parallel connection of your panels... But, if you are running 8.6 amps and 12.4 volts into your battery:

• 8.6a * 12.4v = 107 watts into the battery bank (is that correct?)

Note that 12.4 volts on charge may indicate a fairly discharged battery (or a large battery bank and not too much energy going into the bank relatively speaking).

Your battery resting voltage should be around 12.7 volts or so. The charging voltage will gradually increase to around 14.4 volts (or whatever your controller is programmed for)--at which point the controller will begin to cut back on its output current (Bulk is full current, Absorb is when the controller is reducing current to keep battery at 14.4 volts)--eventually, the battery will be fully charged and the controller will drop back to holding ~13.7 volts or so (float charge).

Depending on the size of your panels, size of battery bank, and current state of charge--it could take a few days before your system fully recharges your battery bank (and the charger go to "float" state before the sun goes down).

The voltage on the solar panels will be ~Vmp (actually a bit lower because hot panels drop their Vmp voltage a bit) while the battery needs full charging current. When the battery is nearly fully charged, you will see the panel voltage go up (and panel current go down) as the charge controller uses less than the panel's maximum power.

-Bill

Re: controller and shore power or genny

Yea--Batteries more than a year old tend to not recover from a 100% dead very well...

Making sure your setup charges properly with these batteries as a test subject is not a bad idea.

If you get around:

• 23v * 2 panels * 4.35amp * 0.77 derating = 154 watts into battery
• 154 watts / 12.4 volts (or whatever you measure) = 12.4 amps into battery

In the middle of a clear/sunny day, then you are doing fine.

Placing a DC master disconnect to your unneeded loads when in storage may be a good way to protect your battery bank. This guy can handle a lot of current (intended for boat battery bank):


Blue Sea Battery Switch 1-2-OFF 350 Amp

I also like a battery monitor--but even the less expensive ones (such as a Trimetric TM-2025A Battery Monitor) may be too much to justify for your small system.

-Bill

Re: controller and shore power or genny

You are doing OK so far...

Going to 24 volts and a converter to 12 volts--Unless you need a lot of power (more than 1,200 watts or so)--you are probably better off staying with 12 volts as much of what you will be running is probably 12 volts.

It will cost you some extra $$$ to run heavier gauge wiring because of the higher currents and the small voltage drop tolerated by 12 volt systems (roughly 1.0 volt end to end maximum--although, you might aim for 0.5 volt maximum for your voltage drop to the loads).

If most of your loads are 24 volt (or on an AC inverter)--then, perhaps, a smallish 12 volt converter would be OK.

You are probably kind of stuck between the 12 volt "cheap and plentiful" 12 volt devices and the ease of running stuff off a 120 VAC inverter.

Both the inverter and the 24:12 converter add losses--so you are left trying to find the most energy efficient setup (obviously with solar PV--Conservation becomes a way of life).

Doing some AC and DC power (current) measurements of your loads and estimating losses (perhaps in a spread sheet), may give you a better handle on the best way to proceed.

-Bill