Isotherm fridge

[jage]

Originally Posted by daveb

I’m just saying why cycle the batteries unless you are out in the field and doing what they are made for?

I think charging them improperly should be in there. I'm not sure where it goes, or how it's done, but I've roasted many a cell battery by quick charging off the 12v, whereas the same cells last forever if I use a mini-110v invertor and the "wall" charger.

Also, I've given up on keeping my laptop battery in my laptop. Once a frank discussion with a tech gleaned the admission that the battery constantly drops to 98/99% and is topped off. To the battery life that counts as a charge cycle, and there are a limited number of charge cycles.

Personally I wonder if there is ANY way to keep any battery in good condition over time. Sometimes I wish the van took AA and I could just go to Costco and pick up a pallet of Duracell to refill my batteries.

http://www.youtube.com/watch?v=s_8n2Qgguto

[Scalf77]

Dave,
I think your data looks pretty solid, I do question this statement "I have a nasty habit of leaving my fridge stocked ready to head to the hills and my charger seems to let them drop to like 70% by morning." Are you saying that when you are plugged in and charging that you will drop the down to 70% overnight with the refrigerator running? That does not seem right to me, or I'm just interrupting it incorrectly.

I think we have two or three ways to keep our batteries charged,

Alternator
Plug In - Charge with inverter/charger
Solar

I don't have Solar so I use the first two, alternator and Plug in. When parked in my driveway I have it plugged in and charging, the refrigerator is always turned like yours. Like I have said this appears to work for me. If I come out and take the van, when I unplug the batteries are at 100%.

I know a lot of people have solar and it is enough to keep their batteries topped off. It obviously may not work for some people year round.

The part that confuses me the most is that in this thread some have expressed reluctance to plug in all the time to keep the batteries charged. There are obviously things that can go wrong, but why would you be more comfortable with a two stage charger (I believe most solar controllers are two stage) while a good inverter/charger is three stage. I just don't see anything wrong with plugging in and using a good charger to keep you topped off. I have more concerns with the bi-directional separator then I do plugging in all the time.

So, back to Angel's issue, she apparently was not getting enough charge from Solar to keep her batteries charged all the time while parked (with the refrigerator running). Did not feel comfortable with using the inverter/charger all the time, so she looked for a different solution. In that she found an AC converter for fridge, this would allow her to plug in the refrigerator, it would now it's power from AC through the converter (Still running off of 12 Volts, but not the House battery 12 Volts). This now solves her issue with keeping the refrigerator running and all the time, and hopefully solar will keep her batteries topped off.

As with most solutions, there are sometimes unintended consequences. The consequence of her solution is now that when she turns on her inverter the refrigeration will now switch and run off of AC through the inverter. Not knowing the specs on the equipment she has, I will use 90% efficiency for both her inverter/charger and refrigerator converter. So she now has a refrigerator that is using 20% more power then if it was just running straight off of the house battery. A 10% loss from going from 12 volts to 115 and a 10% loss from going from 115 to 12 volts. So what does she do now? if she does not use her inverter that much when dry camping, nothing and live with 20% extra power usage. If she does use the inverter a lot she may have to look at putting in a switched outlet like Jage did.

I'm with you, I am certainly not an expert and reserve the right to be totally wrong. This has been a good thread

[daveb]

Greg, what inverter / charger do you have? Time to dig out the Prosine manual I guess. Maybe it's set to a default mode.
I was seeing a similar problem that Angel did. Like I said, I don't fully understand how the charge cycle works on the Prosine only that it's a 3 stage charger with a temp probe. For what ever reason, the charger reaches the float stage and stays there. This might not be a problem if the charger is set to 12.8 as 100% (fully charged) If the battery state would not drop below 12.8v I probably would not consider it a problem but is doesn't and drops below that. It could be the Prosine is not configured correctly. But I still stick to the rule that any extra cycling on a battery is bad and I don’t want to charge when it’s really hot out. So if the van is just sitting why not let the fridge run on AC. Angel's refrigerator is 12 volt only and she claimed the batteries were dropping to 12.2 or lower by morning. I don't think she plans to use the inverter to run the converter only run it off shore power to power the fridge. You're correct in saying her converter should be able to be shut off when the inverter is being used.

[daveb]

Well it looks like I have some reading to do. There are several configurations to look into and 21 charge modes. I need to contact SMB and see how they set this thing up. Just scanning over the PDF, it looks like the charger is going into a sleep mode after the batteries are charged up. If the load sensing is turned off it might not see the fridge on and won't restart the charge over. The manual is kind of complicated.
http://www.wholesalesolar.com/pdf.folde ... Manual.pdf

[Scalf77]

Dave, I have the standard Tripp lite that SMB uses, I believe it is the RV1512UL.

greg

[windguy]

interesting thread guys, thanks for sharing your thoughts.
I'm trying to learn more about the electrical system for my pending Sprinter design.
I have to admit, my head is spinning a bit and I'm a technical person.
Would my comprehension go up if I'm drinking beer while reading this?

What do most folks do when they park their van in the driveway between trips?
Do they plug in to 110V shore power (from the house) or just run off of solar?
Not sure if we need to keep the fridge running when not in use. Is there a better practice?
Empty what's left in there and turn off and let the solar support any electronics that are running or have a master breaker that turns everything off.
I guess a lot depends on how often you take trips.
My preference is to not plug in to shore power at home since we're technically not allowed to park an RV in our driveway and the Sprinter isn't an RV, right?

thanks!

[yvrr]

I tend to not plug into shore power at all any more...ever. (We don't carry our cable with us at all.) We don't keep our Isotherm going when we aren't using the van and I installed a toggle switch years ago to easily turn off the detectors so there is no draw on the house battery when parked in the driveway. Thus, no need for shore power even if we didn't have solar.

A day or so before a trip, I turn the Isotherm to Manual and "overcool" the refrigerator. Before dark that day, I turn the ASU to Automatic. In that position, the ASU will monitor the voltage of the house battery and stop drawing on the house battery when the it gets to 12.2v. I pack the refrigerator the morning we are going to leave...packing the refrigerator requires continually opening and closing the frig which will result in the temperature rising but doing it early in the morning (before the outside temperature is very high) helps and gives a full day of driving, etc. to give the refrigerator temperature time to get back down where it belongs. During the summer months, I'll start the refrigerator a day earlier and load it after dark.

(Be sure and pre-cool everything. We once loaded the refrigerator with a number of cans of Coke and bottles of water that hadn't been precooled and the refrigerator never did get caught up...we ended up dumping a lot of stuff in the refrigerator in order to get the temperature up to where it needed to be.)

Our recommendation...get an Isotherm refrigerator and solar and you won't worry about house batteries until you need to replace them due to age...

[Scalf77]

Windguy,
That is the beauty of an SMB, you can design it for how you are going to use it. If your requirements are that you won't be able to plug in, you can obviously do that. Jack has a system with solar that works great for him. I don't have solar, but I can plug in. I find my method works fine for me. Dave's method is working for him. Everybody here may have slightly different methods for approaching things, if that sounds like it fits your needs and their having positive results, go for it, I wish the forum was here when I bought my rig.

it only gets better.

-greg

[windguy]

Jack & Greg, thanks for the plug in tips and advice.

[jage]

yvrr you should send me your "extra" shore power cord! I'd like a second one because I loathe that the final step before travel for me is always unplugging and stowing the shore power. I keep meaning to get an "home" cord, but never get around to it!