100+ ambient Temp - ARB 50qt - 100 watt solar panel - Not enough?

[dstock]

Thanks guys, a wealth of information here!! It's given me a lot of ideas on things I can do to improve our setup and our habits, that's why I love this forum! Hopefully others will benefit as well.

For the record, we did start off with a fully cold fridge running off AC and very full. The other factor here was the ambient temp at night was still in the high 80's -90's, so not much relief at night either. Still lots of things we could have done better and more efficiently. We live and we learn!

 

[dstock]

Making sure the cooling unit can transfer the heat removed from the box is the single best way to increase efficiency. The air intake and exhaust for the cooling unit must not have any restrictions, and keeping the interior of the vehicle at no higher than ambient temps is of utmost importance too. Clean the dust and hair off the condenser can make a huge difference.

Now Odyssey batteries are a fine battery, but when cycled deeply, they require huge recharging currents. They do not make a good "solar only" recharge battery.

If after several cycles they are not fed with a 40% recharge rate, they cannot deliver their rated capacity.

So 100 watts of solar was not enough to keep up with the demands of the fridge, and it certainly is not enough to properly recharge Depleted Odyssey, even if it were not powering a fridge.

Odyssey recommends a minimum 40% current until 14.7 volts are reached( constant current). 14.7v is then to be held for 4 hours while the amps required to hold 14,7 naturally taper( constant voltage). After 4 hours then float at 13.6. If one cannot float at 13.6, better to disconnect the battery than to float it at 13.2v.

So if Your Odyssey batteries have been cycled deeply previous to this outing, and not recharged according to the above regimen, you did not begin this outing with the batteries near their fully charged capacity, even if you drove 20 hours to get there, even if you drove 40 hours. It does not matter how big and shiny and expensive your alternator is either as it is still unlikely to make 40% and then hold 14.7v for 4 hours.

The Odyssey engineer I spoke at length with said such batteries, those deeply cycled, and not recharged according to their recommendations, would require at least 2 cycles down to 50% probably 3, then recharged at the 40% to 14.7 for 4 hours rate before they could reach their maximum energy density.

So there is that.

Great information. My batteries had not been cycled deeply previous to this outing, so I believe we did start with our best foot forward battery-wise.

So now my question is, what is the best way to get the aux battery back to it's maximum level? Since it won't be deeply cycled anytime soon, should I look into a battery charger/conditioner? It is getting charged as I drive everyday as my JK is my daily driver but wouldn't be getting cycled and recharged in the manner you mention above.

 

[wrcsixeight]

It is hard to recommend cycling a battery to 50% when not needed, however I think this, and a proper recharge will keep that Aux battery in top condition for the next outing.

NOw the issue is with the Chargers. Odyssey has a list of approved chargers and without exception they meet this 40% rate and at least come close to the 14.7v Acceptance.

http://www.odysseybattery.com/documents/ODYSSEYapproved12VchargersMay2013_000.pdf

Odyssey sells their own charger, made by Schumacher to meet their charging algorithm, but they are expensive, and should only be used on one battery at a time. If your NL relay will combine both batteries when it sees charging voltages on either, then it should be disabled so the full amperage goes only to one battery.
http://www.amazon.com/Odyssey-Batte...84441&sr=1-1&keywords=Odyssey+battery+charger

The Odyssey engineer I spoke with mentioned there was another way to squeeze every last amp into the battery, and that was with high voltages(16+), at very low amperages. this of course dictates that nothing be connected to the battery but the charger at the time of charging as those voltages are in the danger territory for many 12v devices.

The 40% rate is what kept me from getting an Odyssey as my solar can barely make 20% on the best day mid summer.

I did Buy a NorthstarAGM battery, which had a longer list of approved chargers. I suspect NS and ODYssey are very similar internally though, as they make many of the same claims. I cycled it 60 to 70% nightly for a week and allowed it solar only recharging, and it still held a resting high OCV and seemed to hold voltage the same each night under similar loading, but when I transferred it back to engine starting duties, i could tell that extra "oomph", that near violence at spinning the starter motor so quickly had diminished somewhat. So I cycled it again to about 50% and then fed it 25 amps from my Schumacher and that violent starting Oomph was back.

Also when this battery was spanking new, it had an open circuit voltage of only 12.84v. NS claims it should be 13 or over. I could not force any more amps into the battery at this stage at voltages under 14.8, and was in a mind to return the battery.

Remembering the Odyssey specs I decided to cycle it to 50% and give it 40% recharge rate. It really seemed to wake the battery up. That first engine cranking after that 50% cycle and 40% recharge rate was very surprising, and after that, fully charged resting voltages have been no lower than 13.06v.

So While it is hard to recommend cycling a battery unnecessarily, I have found that doing so, and recharging at a high rate seems like a slap across the face of a lazy battery.

I am giving my NorthStar battery 25 Schumacher amps as I type this, as I turned a few switches and took it down to 12.1v overnight. I had not given it any Schumacher amps for a while and only have been cycling it very shallowly, but it seemed to have lost a bit of that starter violence in just sitting around, or just doing engine starting duties.

I've also noticed my Flooded group 31 battery enjoys being recharged at a higher rate than my solar can do, after a 50% cycle. It really holds a higher voltage during the next discharge cycle, and measuring Specific gravity confirms this too. And this battery manufacturer recommends only a 10% rate which is 13 amps, I was feeding it 25 amps in bulk mode.

The Low and slow mindset of battery charging should be locked up with the old wives and their tales, in my opinion.

 

[dstock]

Thanks wrcsixeight for the education!

 

[1leglance]

Maybe I missed it but you mentioned Diehard Platinums but not what size they were...
There is a big range of Amp Hours depending on the size of your battery.

For example I used a Diehard Plat group 31 which states 100 Ahr with a Kyocera 120w panel to run a ARB 60L low profile fridge for 4 days at the Overland Expo, opened and closed it without thinking twice and never got before 12.3v on the battery when checking first thing in the am (should be the lowest level).

However a group 34 Diehard is only 68Ahr....big difference in keeping up with the fridge if you run that one.

Otherwise great info in this thread and I plan to reread a few of the post till I understand them

 

[dstock]

Maybe I missed it but you mentioned Diehard Platinums but not what size they were...
There is a big range of Amp Hours depending on the size of your battery.

For example I used a Diehard Plat group 31 which states 100 Ahr with a Kyocera 120w panel to run a ARB 60L low profile fridge for 4 days at the Overland Expo, opened and closed it without thinking twice and never got before 12.3v on the battery when checking first thing in the am (should be the lowest level).

However a group 34 Diehard is only 68Ahr....big difference in keeping up with the fridge if you run that one.

Otherwise great info in this thread and I plan to reread a few of the post till I understand them

I am running the group 34 so it is more of a challenge for sure then the group 31. The 31 is too big for my application.

This is the first time it's been an issue, the high ambient temp day and night certainly played into the scenario and are constant swapping out of waters (and beer) didn't help at all.

I'm with you on the re-reading, it's actually starting to make sense! :wings:

 

[dstock]

After all the battery talk, I have an additional solar question.

Like many of the portable solar panel kits, my charge controller is mounted on the back of the solar panel and then has a long lead to go to my battery. It seems to me to avoid a drop in voltage the solar charge controller should be as close to the battery as possible.

Is this correct?

 

[wrcsixeight]

After all the battery talk, I have an additional solar question.

Like many of the portable solar panel kits, my charge controller is mounted on the back of the solar panel and then has a long lead to go to my battery. It seems to me to avoid a drop in voltage the solar charge controller should be as close to the battery as possible.

Is this correct?

Yes, and using thick wire, thicker than you think you need, can really help increase what makes it into the battery. The longer the lead, the thicker the wires needs to be. If the wire was provided with the solar kit, expect that it is too thin, as thicker wire would cut into profits.

Also the cable/wire terminations are very important. Proper crimp or soldered ring terminals can seriously reduce resistance, Compared to just squishing bare wire under a Nut, especially as the connection ages.

 

[dstock]

Yes, and using thick wire, thicker than you think you need, can really help increase what makes it into the battery. The longer the lead, the thicker the wires needs to be. If the wire was provided with the solar kit, expect that it is too thin, as thicker wire would cut into profits.

Also the cable/wire terminations are very important. Proper crimp or soldered ring terminals can seriously reduce resistance, Compared to just squishing bare wire under a Nut, especially as the connection ages.

Should the wire from the solar panel to the controller be thick as well?

 

[wrcsixeight]

Yes, but if the run is very short it won't make as much of a difference.

 

[Crom]

Didn't read the whole thread...just wanted to share my experience.

I have a an ARB 50q fridge. I recently added a canvas transit bag to it and on a recent trip it froze some of our food where previously it did not, I had to adjust the thermostat up a bit. This was in 98* heat. At the same time though I added insulation to the truck...

I also added reflectix to my truck topper windows to keep the sun out.

For what its worth I use a 96AH Walmart Marine hybrid battery, 75W solar array, and a CTEK 250 Solar/DC-DC charger. It has been working awesome for over a year now.

 

[unseenone]

That's good info and pictures there.

I'd be curious about those panels with integrated charge controller. What exactly is it. It would be interesting to be sure what it's putting out.

The wire size required is going to be determined by the voltage and current running through it, and the distance it needs to travel. That's calculated in total wire distance, so if you're wire run is 10 feet, the electrical length is 20 feet. The 20ft number is what you would want to use to calculate wire size. For example if you wanted to have a 30 amp run at 20' based on AWG guidelines you will need AWG 8 -- Here's a neat calculator to help you figure what size wire you need. http://www.bulkwire.com/wireresistance.asp

I like this wire for Auto and Marine use. The standard on DC for boats is Red and Yellow for ground, to avoid mixing AC and DC wiring. On Autos, and generally it's Red & Black. http://www.jamestowndistributors.co...milyName=Ancor+Marine+Grade+Duplex+Flat+Cable

ref: https://en.wikipedia.org/wiki/American_wire_gauge

 

[bat]

It seems to me to avoid a drop in voltage the solar charge controller should be as close to the battery as possible.

I had the same question so I called up Morningstar and spoke to a tech and he did not see a problem with the controller on the panel as long as the wire is big enough to carry the load. I told him I was using #10 marine grade wire at 25 feet and he said no problem, the wire on most foldup setups is pretty small and an upgrade is a good idea.

 

[SteveG]

Great thread... lots of good info.

I was recently in a similar situation. We spent a few days in Death Valley and my battery had a hard time keeping up with the fridge in the high temps. I'm a fair weather camper, so it's not a big deal but on occasion, I will be in the heat so I'd like to have some solutions (or, at least, improvements) for my fridge/battery worries. I was planning on making some shades for the rear windows and will pick up a transit bag, too.

I was also thinking about putting a small battery operated fan in the car. I have a fan (powered by 2 D batteries) we use in the tent that runs all night on low will little to no loss in speed overnight. I wonder if it would help the fridge. Thoughts?

 

[wrcsixeight]

While 'x' gauge wire is rated to carry 'X' amount of amps at a certain distance, the goal with solar battery charging is to get as much from the panel as possible, meaning minimal voltage drop, and minimal voltage drop is accomplished with fatter wire, and good quality connectors at the ends. Now this does not mean that someone should buy 60 feet of 4/0 gauge wire for minimal voltage drop, for a 100 watt panel, but it does not mean 18 awg is acceptable either since it is rated to carry 10 amps at that distance, and the panel will never make more than that.

I think 10awg at 25 feet, 50 feet total circuit length is inadequate for a 12v nominal panel with the CC on the panel itself. Perhaps if it were a 24v nominal panel sending juice to the Mppt CC located near the battery that would be good.

MPPT is more affected by voltage drop than PWM controllers.

About the fan in the car. Will this be exhausting hot air from the car, or exhausting air from the cooling unit on the fridge, or just be moving hot air around inside the hot car?

If there is no restrictions around the vents on the fridge, the best location would be sucking hot air from the highest point of the car. In an extreme case I could imagine running some ducting to force ambient air to the inlet on the fridge.

There are some 12v computer muffin fans that consume so little electricity and move a good amount of air that the decreased amp draw of the fridge will make up for the electricity consumed to spin the fan.

This Fan draws 0.05 amps and Moves 53 CFM, and makes very little noise. I switched out the Fan provided with my Vitrifrigo c51is with this Noctua:

http://www.noctua.at/main.php?show=productview&products_id=42&lng=en&set=1

Wire this to a ciggy plug, and put it in a window, perhaps with cardboard shroud covering rest of opened window, and your vehicle will stay reams cooler inside.


Since the wire on a portable panel will also be in the sun it will heat up more too increasing resistance causing more voltage drop.