Foretravel Owners' Forum

For those of you that have solar what do you do with the battery charger when plugged in. Solar off charger on when plugged in, or charger off unless needed. Can you just leave both on and they play nice togather(outback controller)?

Leave both on. Each charging source will read voltage or soc and shut off as necessary.

I personally leave all charging up to the solar (when parked ie no engine running) and when I plug in (very few times) I turn off the inverted charge. I should reset that dip switch to have it in the "off" mode but keep forgetting to do it because as I say we seldom are plugged in. When we need 120v we use the inverter and as soon as done with that we turn it off. Remember with our Res' fridge we have another smaller inverter for that power and it does not have charging function. Plus our gen set is not used- unless Ruth needs 120v on for an extended time while cooking etc.
JohnH

X2 on leave both on.

With solar, you actually have 3 possible charging sources: Alternator, inverter/charger, and solar.  They all seem to get along fine on our coach, and I never give the question of what is doing the charging any thought.  One exception - if we are dry camping, and our house batteries are depleted in the morning, I like to run the generator (to power the inverter/charger) for a couple hours before we hit the road.  This takes some of the load off the alternator when we start the big engine.  Then, once we are ready to leave, I shut down the generator, and the alternator and solar controllers rapidly finish the job of bringing the batteries back up to 100%.

We mostly only turn on our two solar controller breakers (one to panels & one to house battery bank) when not using solar panels.  That means Cummins engine running, generator running, shore cable connected, solar is usually turned off.  No two battery chargers play well together all the time.  The charger with the highest voltage reading can fool the others to believe the battery is full, when it is not.  Ie: When batteries are low and need an hour+ of 100-amp Xantrex charging, solar may charging at a much lower amp rate, but at a higher voltage than Xantrex, causing Xantrex to stop charging.

As long as something is charging the batteries, and they end up at 100%, what difference does it make which device is "in charge" (ha, ha)?

In my 3 previous solar installations, once I have them up and running I do nothing about switching anything. Is it the best way....maybe not. Has it worked....always. I wash the panels every couple of months, but other than that I ignore the system and enjoy the silence.

Put in new 8D's and they lasted two years before burning up. Charger/inverter problem. New batteries three years ago and ONLY solar charging them and no problems. Plenty of solar to do the job so ALL 12 vdc if from solar one way or another. Happy!

Chuck, the difference it makes is if the smallest capacity charger (solar, with little sunshine) charges at a voltage higher than the highest capacity charger (Xantrex, Magnum), the higher capacity could think battery bank is full, and stop charging.  It takes amps to fill the battery, but the "is it full yet?" measurement is by reading voltage.  Easy for multiple chargers to step on each other.  So the one "in charge" may not the most capable.

We see the conflict in action when our Xantrex meter amps is zero, when it should be pumping.  We get around this by using a lower solar charge voltage profile when not dry camping.  We use higher solar charge voltages when dry camping like our two weeks in Quartzsite.  Higher voltages charge faster.

Some charging systems take battery temperature in consideration to modify charge voltage, while others may not.

RVs have many limited resources and choosing to manage them is just a matter of personal choice.
 

This subject is out of my field and I am curious as to how a lower amp (solar) putting out higher voltage could cause the battery to reach 14.2 volts to fool the inverter charger to stop charging. Doesn't the charger read the battery voltage not the solar output voltage?

The "battery voltage" is always the highest supply voltage.  That's why you have to remove all charging sources to measure true battery voltage.

This guy explains it pretty good.
".12.8V would be an atypical charging limit for a regulator. Most regulators go in constant current bulk mode until 14.2-14.8V are reached after which they go into a constant voltage mode and ramp the current down to stay at this voltage during the absorb phase before shutting mostly down into a maintenance mode at 13-13.5V.

If your battery bank is large, or if it has been drawn down some, it will not reach the 14.2-14.8 volts until quite a bit of the bulk mode charging has occurred.

If all of your charging sources have multistage regulators that are all set to the same charging regimen points (and you have a large enough, or sufficiently depleted battery bank), then all of them will put out all they can during the bulk charging stage.

When bulk charge is reached, then they may start to play against each other and the output of one charging source might shut down the output of another due to slight variations of the regulator set points and how charge is sensed. But now it doesn't matter because your batteries cannot accept the higher current of all your charging sources and as long as one of those sources can supply the absorb current, all is well.

In fact, it is dandy if you have multiple charging sources. For example, if you are in the absorption phase of the charge cycle and your solar panel regulator has shut down your wind generator regulator and is supplying the entire absorption charge, then when clouds decrease the solar output, your wind generator will step in and shut down the solar regulator and continue the charging regimen.

We have 480W solar, a 125A AC charger and two 60A engine alternators as charging sources. The solar and AC charger regulators are set to the same charge points. When the AC charger is on and it is sunny, both the solar and charger regulators contribute full on when the batteries are low. When the absorption voltage is reached, the AC charger regulator over-rules and the solar regulator shuts down the panels completely. When the charger is turned off, the solar regulator immediately comes back on line and continues the charge regimen.

The only true conflict for us is the engine alternators. They are internally regulated and ramp down output at 13.8V. So when it is sunny and we are motoring, the alternators shut down before bulk charging is complete even though the batteries can take more charge than the solar is providing. I put a diode and switch in line with the alternator sense wire to drop the voltage 0.5V which helps a lot in keeping the alternators on-line during the bulk charge phase.

Long story short: make sure your charging source regulators are set to the exact same points and they will all play nice together until you are sufficiently charged that it doesn't matter if they interfere and swap roles with each other."

I leave both the solar and Xantrex charger on all the time.  Never a problem. I monitor Xantrex, solar, and Xantrex Amps and volts.  If I have shore power and a sunny day, the Xantrex supplies normal charging, up to 105 Amps and holds the battery voltage high enough that the solar charge controller adds nothing.

I guess I will try the KISS first and see how it works leaving both solar and charger on and see how it works. In the end likely I will rely on solar only to handle the battery charging chores as long as we have sun.

You are correct. You can put 14 volts into a depleted battery that will still read 12 volts. As the battery accepts the charge, the voltage will start to rise to the charging voltage, this is bulk charge. At a certain point, battery voltage and resistance will be enough to tell charger [ no matter what charger it is, if it multi-stage and set to correct voltages for your type battery] to change the charge voltage to the absorb stage, here current will decrease to battery till it reaches float stage, where just enough current is passed to battery to keep it at that stage voltage. At some point, one charger type may act differently than another, but is not a critical factor because the battery is probably already 95% charged and the current will be low anyway.

My (personal) thanks to Barry and Jim C. for the detailed explanation of how the different charging sources interact.  I will have to get the books out for my solar controllers and the Magnum inverter/charger, to see exactly how they are set up.  I'll try to determine how they compare to each other, especially in the settings mentioned by Jim.  I certainly don't dispute anything said by either of these two knowledgeable members.

That said...In my experience, KISS works very well.  This is based on living for a year with our particular setup on our coach, and operating under all different conditions.  I leave our inverter on all the time, our charger on all the time, and our solar controllers on all the time.  Our batteries always reach 100% some time during the day.  This is true if we are plugged in to shore power, or dry camping, or driving down the road.  As I mentioned above, the only time I intervene in the otherwise totally automatic charging operation is if I think the generator is required - usually under one of two circumstances.  First, if we are dry camping and I want to bring the batteries up before hitting the road early in the morning, and second if we are dry camping and there is no sun.  Otherwise, I do...nothing (except glance at the battery meters occasionally).

Perhaps I should be more proactive in my monitoring and control of the charging systems...BUT, if it works and the desired result is achieved, why mess with it?

(Once again, this is just me.  I do not encourage other members to be so lackadaisical in their approach to battery charging control)  8)

I do not think you will have any problems, solar panels thru a good charge controller put out 14.5 volts to a battery on bulk.
A good inverter/charger will put out 14.5 volts to a battery on bulk. A good 3 stage charger the same. I once had a wind generator running through a charge controller that put out 14.5 volts, even though the motor on the wind generator produced anywhere from 15 to 100 volts according to wind speed. Battery does not know or care where voltage is coming from, as long as it is the correct voltage and current to charge the battery. My panels now are in series/parallel and supply 125 volts to charge controller, guess what the battery gets from the charge controller? yep 14.5. It makes no difference how many sources you have, as long as each charge controller or charger follows the same protocol. Some controller and chargers can be  customized, but in general, if set to a battery type eg. agm, all charge exactly the same way, a 8 amp panel through a controller, or a 100 amp inverter/charger.
Old type converters and 1 stage battery chargers had constant voltage and constant current.
These cannot charge a battery well. They are often called "battery boilers" and in their day ruined many batteries.
Your engine alternator is a little different and unless you buy a special voltage regulator for it, will not bring you batteries up to full charge, but will come close.
Almost everything you can buy today is at least 3 stages and follow pretty well the same charging patterns.
If you do not have a charge controller and try to feed your battery directly from the panels, you could have a problem because you cannot regulate voltage or current from the panels which of course changes with the amount of sun . With a battery and a small panel you could be okay. {Like the ones you put on your dash and plug into a cigarette lighter socket]

I remember wolfe10 mentioned using 13.6 volts max here.

Without a battery temp charge control  the all temp max on a gel is 13.7.

Too many boiled batteries long ago makes me careful.

Solar is installed 840 watts Outback 80 controller. It's is currently wired (negative cable) to the shunt for the Link 2000 so it shows current and volts. How are yours wired stand alone or through the shunt?

Through the shunt is fine, using link info and controller info you will be able to track your production and usage.
Of course the easiest way is to install trimetric, all information you need on one gauge.    home - Bogart Engineering (http://www.bogartengineering.com/)