Solar Charger vs Converter/Generator

[Kayak73]

Just for fun I have been trying to understand why running my generator to charge the house batteries on a recent boondock was to a great extent unsuccessful. Even on a rainy day the converter lost out for the times when light got brighter. As near as I can tell the setting for "wet" or flooded wet cells on the solar charger has a 14.7 VDC bulk rate. That seems to tell the converter the battery is charged since it has a non-changeable bulk voltage of 14.4 VDC. PD9245. OK, today in a similar rain storm/cloudy day I measured some amp usage and charging. The converter will apparently never charge those batteries once the solar "turns on" in the AM because if you knock down the batteries to say 40% SOC the solar controller jumps the voltage to 14.7 and run the genny or plug into AC all day long and you only get the lower amperage of the solar because it is going to dump bulk voltage into the battery. Next move for boondock is to install a breaker on the supply side from the solar into the controller to shut down solar when the demand requires the higher charge rate of the converter/genny. This has been far too stressful for a retired old electrical engineer. Two conflicting systems which most just ignore but my real live boondock experience says WGO should have put a breaker next to the solar controller to shut it off. Of course they didn't need it because the OEM batteries were too small to run the refrigerator anyway overnight. On the other hand if I have 400 watts of solar and a good bright day I would shut down the converter, never run the genny. One or the other but together they do not deliver. I suppose I could choose another battery type on the solar when running the genny for converter charge but the breaker seems a better option. Reality is you usually can only run the genny 8AM - 8PM and during those hours the solar controller is on so for my case with the 12VDC compressor fridge I'm down at least 40-50% every AM depending on whether I used the CPAP and what else we did in the rig, in other words near as I can tell in the as shipped OEM version you simply can't charge the batteries - great! Well, you can plugged into shore because they charge overnight with the PD9245. Food for thought or laughs for those with a like rig and fridge. You loose or you loose, every day you get lower on the power curve but you will know if you drop to 40% SOC (a bad thing) even without a Trimetric buzz because the refrigerator will shut off. I did pretty good on the 7 night dry camp but now I know why I could never get batteries out of bulk charge, even running the genny most of the day on day 5 - the crazy solar controller was putting 14.7 on em. Bulk charge is normally on for the first 85-90% of total charge then it drops to absorbtion but with the solar I had it never got close to 90%. Next trip I will be armed with the Trimetric installed, solar breaker and possibly another panel on the roof.

[Kayak73]

Just a note to continue... The spec sheet for the Zamp controller shows 14.0 for bulk and at the highest amps available. That should be OK, absorption says 14.7 and this stage takes far longer than bulk starting at around 85% SOC. I measure differently with the converter off than that or it is always going into absorption? I can set the Zamp for AGM and absorption is 14.4VDC. It would seem the only way to stop the interaction would be the breaker for solar.

[creativepart]

We dumped the OEM Zamp PWM solar controller for a much more efficient and smarter Vectron Smartsolar 100/30.

But I never encountered the issue you seem to be noticing. I’m not convinced that what you think is happening is accurate. The solar controller is directly connected to your battery bank and so is your converter. They are two separate charging sources. Just because the solar is adding volts to your batteries your batteries are still at a lower voltage and you converter should be smart enough to read that SOC.

My setup is different with OEM AGM batteries and charging via our OEM Magnum Inverter. So, my experience is going to be different than yours.

[Kayak73]

Thanks, and yeah our rig is tiny compared to yours and the 12VDC refrigerator gives me a real challenge for dry camp. As noted I do not know or expect that the PD9245 converter can actually measure SOC in any accurate way. For example it does not even know the AH rating of my batteries. It is looking at voltage. It is seeing the voltage of the solar and the batteries so in daylight solar seems to always win. When I opened up the place where I had the Trimetric on the '06 View I found it not appropriate material behind the cloth (where the ladder stores). The material is very flimsy behind the cloth, like pressed cardboard thin. I'm seriously thinking about the Victron 712 now, mount it under the sink where I can get to it if necessary but use Bluetooth normally on my phone. Like the man said, we are not running a power plant...but we really are just on a smaller scale. It was fairly easy to test, just ran the batteries down with the solar covered and converter off to about 50%SOC, left solar panels covered, turned on converter and bam, super charge in just a few hours of time right into absorption which would run for many hours longer to top off the 300AH battery. It appears with silly intuitive testing the solar wins so I'm putting in a 30amp DC breaker in the solar feed to the controller. It is pretty quick getting back to 85% SOC or thereabouts but the last 10-15% takes a long time. So in "real life" boondock with the solar breaker installed and off a two hour generator run in the AM and let solar work the rest of the day in absorption and I should be good to go long term (after adding another panel on top for 370 watts). With the fridge we have the batteries will never make it to maintenance mode in dry camp. Your AGM batteries do take a charge much faster than my Trojan wet cells, lower internal resistance.

[creativepart]

Bill, when answering your post before I had limited experience on this subject. But we are on a month-long RV trip right now and we just finished a 3-day dry camping stay in a lovely NPS campground in Arizona. We relied on our solar panels and occasional generator use to power our needs including a full sized residential fridge each day.

When we start our generator our Victron SmartSolar charger automatically stops charging the batteries. I did not realize it did that before. But learned this during our stay there.

[rarebear.nm]

I do not know about our controller. However our MorningStar MPPT controller manual states to disconnect the load side (battery) before removing solar power to the controller to avoid damage to the controller. I have three 350 watt panels on the roof wired in parallel, each with a fuse in the roof top combiner box. Next to the controller is a battery disconnect type of switch for the down haul and a breaker going to the battery. Thus I can isolate the controller on both sides.


I agree that OEM solar systems seldom work very well. Way too many people who are discouraged with their solar systems, for good reasons. I used Silfab 350 watt panels. They will continue to produce power even in very low light conditions. Opposed to solar panels frequently found on RVs. Last summer in Alaska all summer with low sun angle and even parked under trees we produced enough power to recharge the 460 AHr battery bank. The furnace typically ran at night and power SoC would be down to perhaps 87-90% by morning. Full SoC by 10-11 am almost every day. Only once did recharge go after 12:00. There was one inch of snow on the roof and under trees in a canyon. I turned off the 120 volt powered converters when I installed the solar and never used them since. I have a PD9245 & PD9270 wired in parallel for 115 amps. All summer the geny only ran for about 22 hours total. Mostly for the microwave. Our solar system has provided 100% of the 12 volt power used in our rig since it was installed.



I know many people yak that you must have full direct sun for solar to work. In many cases that is true. But there are production double sided solar panels on the market. The backside can only get scattered/indirect light and it still works. Not all panels are created equal.


I would encourage you to get a good MPPT controller, install breakers on both side the solar controller and increase your roof top solar wattage to something like 500-600 watts if you have space up there. Make sure the down haul wire is sized properly.


While designing my solar system, I had worked though the very problems you are reporting here. None of the controllers can sense only the voltage on the battery, but rather the system voltage from all sources. Thus with multiple controllers you will have a tug of war unless you custom set the various charge points of each controller to a single charging strategy. As an EE you already understand this, but other readers may not.

[Kayak73]

Well...we are all learning! I think we would be better off with a residential fridge as well in lieu of the 12VDC Norcold.



To be certain I am testing everything I can in the rig while parked at home. In the event the batteries are at 100% SOC or "full" on the solar panel, in full sun at 10:00 AM I turned off the converter and ran the fridge until 3:00 PM. The fridge and parasitic draws ran off the solar and the battery remained at 100% full. The solar charger was not "charging" batteries. As soon as I turned on the converter at 3:00PM no change. Now tomorrow I will drop the charge on batteries to about 40% and run the same test.


In any event I do agree a battery monitor like the Victron is very helpful. I have a Fluke 375 FC which I am using to test and document "things". Today I ran several recorded 10 minute runs with as installed parasitic draws on and running off solar during the above times. The Fluke was clamped onto the chassis ground cable to battery negative and around the green cable (everything to main ground on neg battery post - like connecting a shunt). I will start an album and post the findings as I move along but in a nutshell:


The DE0061 refrigerator runs a 75% duty cycle, no variation at all.
The DE0061 draws between 3.4 amps and 5.4 amps during that duty cycle depending on the compressor stage and about 75% of the cycle it is above 4.4 amps.
The parasitic loads I can find are the Propane gas monitor (about .1amp) and the stereo as you enter the coach (about .5amp in standby measured at the power cable of the unit), the step switch is off.



I think I now understand why the DE0061 is a bear for those wanting to boondock. Let's average to 5 amps for the 75% duty cycle over 24 hours and we find during those 18 hours the refrigerator is using real 90 AH.


Add the baseline load of 1 amp (.7-1.1) for the 24 hours hours, another 24AH. Now using 114 AH per 24 hour period. OK we still need to use the rig, water pump, water heater, LP switch on, let the bed up and down etc. Bummer. I was thinking "fat and happy" with 300AH batteries but now I'm just fat and dumb!


Having said all that stuff I will continue to get graphs and record things appropriately and build the album over time but if you have a rig like this...


Never leave the LP switch on unless you are using it (or do the mod to cut draw), put a power switch inline with that stereo, try to use high loads like the bed up or down when the fridge in not "on" cycle etc.


My real mistake was trying to manually time the duty cycle of the fridge before. Now I can graph 10 minute time intervals and see the true 75% duty cycle and certify the fridge draws much more than 3.2 amps DC. In other words the dealer who posted this fridge video running three days and nights with OEM batteries and only 200 watts solar - is joking, seriously. I really am happy I spent the cash for the new Fluke, the old one had no logging, no BT, no graph etc. It is far better to me than a battery monitor but I will use both.



The inline fuse above the fridge shows very little heat gain during the compressor cycle measured with the IR gun, no point in worrying about that. No matter what we are borderline for a long boondock since you will get behind the curve more each day - good for 4 nights. More than that I need more solar and lithium batteries.

[Kayak73]

Originally Posted by rarebear.nm

I do not know about our controller. However our MorningStar MPPT controller manual states to disconnect the load side (battery) before removing solar power to the controller to avoid damage to the controller. I have three 350 watt panels on the roof wired in parallel, each with a fuse in the roof top combiner box. Next to the controller is a battery disconnect type of switch for the down haul and a breaker going to the battery. Thus I can isolate the controller on both sides.


I agree that OEM solar systems seldom work very well. .

rarebear I chopped your message but yes, you are correct in analysis. The PWM controller from Zamp will not be efficient enough to win the power curve - MPPT is necessary along with rewire and appropriate breaker to shut supply solar off as necessary. We do have limited roof space in the View so new panels must be selected carefully. In general I think my real issue is noted for those with a like rig. Limited roof space, bad OEM batteries, poor solar install and controller and a really bad DE0061 12VDC fridge. To be fair the fridge is cooling fine now but it is a power hog. I also went to Trojan FLA golf cart T-1275s in parallel to get up to 300AH. We have very limited space under the steps - had to chop the storage to get those big honkers installed when replacing the ridiculous OEM group 24 dead batteries. It is a work in progress.

[bkg]

Originally Posted by Kayak73

Just for fun I have been trying to understand why running my generator to charge the house batteries on a recent boondock was to a great extent unsuccessful. Even on a rainy day the converter lost out for the times when light got brighter. As near as I can tell the setting for "wet" or flooded wet cells on the solar charger has a 14.7 VDC bulk rate. That seems to tell the converter the battery is charged since it has a non-changeable bulk voltage of 14.4 VDC. PD9245.

Throwing something in the mix - do you have the Charge Wizard pendant for the PD9245?

With the pendant you can invoke the Progressive Dynamics PD converter to stay in BOOST mode output of 14.4 volt (yes, still shy of the 14.7 VDC output Zamp Solar Controller).

However, according to the PD pendant card, the PD 9200 Series converter on AC can recharge the battery to 90% in 2 - 3 hours.
Point is, you can force the PD converter to stay in BOOST while on the generator (or shore power) if you have the Charge Wizard pendant.

As for your Norcold DC 0061 refrigerator - I'm trying to get my head around that one. I have the exact same unit but thus far have only limited use with mine being that we haven't ventured out a lot with our new View unit.
So, I've read with great interest any post of the Norcold DC unit. I've had absorption units in our past RV's, however, I welcomed the DC powered unit (although I do wish it was dual - AC and DC).
One thing you don't mention with problems of the 0061 is the ambient temp inside the coach. To me this can make some difference for 2 reasons. 1st, the forced air cooled condenser, the higher the ambient temp, the harder the unit has to work to reject the heat. 2nd, the Norcold box is not well insulated.
Considering that you mostly boondock and conserving stored power I doubt you run exhaust fan(s), so I assume the trade-off is the inside temp climbs into the upper 70's - lower 80"s.

You may have already traveled this route; Norcold owners manual provides troubleshooting tips on unit cooling problems that includes checking door seals.
A 75% duty cycle seems awfully high to me, but again, my experience is very limited on this particular Norcold unit.

Bobby