Cheapest Non-Solar Solution for Minimalist?

[Boyntonstu]

AFAICR Bob has a video showing a woman who uses the vehicle alternator as the only source of power for charging.

We have to use efficient, minimum drain devices for the power consumption budget.

Assume a manual disconnect Isolator and a 110 Ah battery.

Would the following items be a reasonable solution for a minimum system?

Lighting - $12 LED light kit from Ebay  http://www.ebay.com/itm/10X-3-LED-C...2V-/401045487749?_trksid=p2141725.m3641.l6368

12V 10x3 LED Lamp Car Interior Lighting Kit Bright White
Voltage: 12V
Power:14w
LED Quantity: 30
Light Color: White
Size: Show as the picture
10 LED Modules Total Length: 164cm
Long lasting, low power
This kit includes 10 LED Modules with a total of 30 LEDs.
Full lighting throughout your van
Custom layout, install them how and where you want with sticker on the back
Super bright, Great for work lighting, or finding parcel quickly and safely

Refrigerator - 2 cu ft  12V/110VAC  compressor type as BW just reviewed.

[video=youtube]

Laptop and Cell Phone charging -  ENERGIZER 900 Watt Power Inverter converts 12V DC from car's battery to 120 Volt AC with 2 USB ports 2.1A shared compatible with iPad iPhone  https://www.amazon.com/dp/B00ATXERNO?tag=tomsguide_forum_vgl-20

Roof fan - Fan-Tastic or ?
Interior fan(s) - ?

Have I left anything out?
Would a 110 Ah battery be enough?

 

[lenny flank]

Not gonna run a fridge off your alternator, unless you drive nonstop all the time.

 

[Van-Tramp]

The length of time you would have to run the engine to keep the battery charged would cost you more in gas pretty quickly. Lenny is right, it wont work realistically.

If you really want to go minimalist, why go with an expensive to purchase, and expensive to operate, fridge? I loved for years on a generic ice-chest from the 80's for my foods that needed to be cooled, which amounted to the following items; beer, milk, and what ever meat I was going to eat that day/night. Even a little 6-pack cooler will do the trick and cost you nothing to buy, and only a few dollars a month in ice. Most other foods you can find a non-refrigeration version of. More at http://www.van-tramp.com/wp/no-refrigeration-foods/

 

[Boyntonstu]

Ice chest.  Would a doubly insulated refrigerator that was cooled down while driving act as an ice chest?

Other than the refrigerator would the other items be OK on a 110 Ah?

 

[Van-Tramp]

An ice chest works great even without using any power while driving. If you ALREADY own one of those fridges, then great. Plug it in while you drive, and use it as an ice-chest when you are sitting still. If you do not already own one, are you really going to drop $600+ on one? Or $40 on an ice-chest? (wrap it in a sleeping bag for extra insulation).

My recommendation is to steer clear of that 900 watt inverter. Nothing you have will take anything near that sort of power, and that large of an inverter consumes power itself. It is one of the largest mistakes that most newcomers do; buy some huge inverter to power a microwave, even though they have no microwave. So how big do you need?

The laptop takes 50-60 watts (4-5 amps) normally per hour - when in use. Charging and powered off will take less. That is your largest power consumer. Phones, tablets, and LED lighting really take no significant power out of your battery. A roof fan will take 1 amp of power for every hour used. The fantastic fans have additional power settings so take (roughly) another amp per hour for each increment in power setting. Even if you have everything plugged in and charging, you are looking at using 6-7 amps of power, that is about 100 watts. So, why get anything larger than you need? (says the minimalist) A 150 watt inverter that plugs into your cig-lighter will do, costs significantly less then the 900w, and needs no extra wiring. If you want to have the ability to run more, then I suggest one of the 400 watt inverters that plug directly into the battery (found at Walmart for $40). That gives you a lot of headroom for extra devices.

Now the question is, how are you going to recoup the power you use? Your 110ah battery gives you 55ah of use before you start hurting the battery (going below 50% storage capacity hurts battery). If you used your laptop for 6 to 8 hours during the day, you will use up 30-40 amp hours of your battery storage. Driving your car, or running your engine for an hour will NOT re-charge that much power. In fact, a car alternator will NEVER charge your deep-cycle battery back to 100%. At best it will get you to 80-85%, even if it ran 24 hours a day. Auto-alternators simply are not intended to re-charge deep-cycle batteries to their max. So, after a single day's use, you will only eve have about 30 aH to use out of your battery, and will never recoup that last 20 aH without solar.

Luckily, you can (now that you saved $600+ on that fridge) go buy a cheap solar kit to deploy when you are sitting still. $100 will get you a 45 watt kit at Harbor Freight. Not great, but will get the trick done. Spend $200 and you van get a *good* 100 watt panel and a 10amp charge controller and you are set no problem. Deploy as needed, pack away when you are done with it. Add another 100 watt panel down the road and you can buy, and run, that fridge (with care, and constant sunny days).

Hope this all helps.

 

[Van-Tramp]

If you are interested in some solar kits, I'd be happy to recommend a few.

 

[Boyntonstu]

Great advice!  Thanks.

We are getting somewhere near the minimum power requirements.

I believe that Bob swears by a 400 Watt inverter.

As for the $500 refrigerator, how about his much cheaper DIY alternative?

[video=youtube]https//www.youtube.com/watch?v=Z77kgVoqKeE[/video]

The Peltier unit that looks like the one in the video is here: https//www.youtube.com/watch?v=Z77kgVoqKeE

At 10 A each  could the alternator supply the 20 A while driving?

Would a Lithium battery that can be greatly discharged be an alternative to a high current charging to 85% LA battery?

 

[frater secessus]

Not gonna run a fridge off your alternator, unless you drive nonstop all the time.

Since OP is talking about a 110AH and isolator, I think this means the alternator was the only source for charging the house battery.

OP:   It is possible that 110AH of house bank t would be sufficient to power a compressor fridge and some light loads, particularly if the vehicle was already going to be moving a couple times a day (delivery driver,  going into town, etc).  

The real challenge is that alt charging alone is unlikely to lead-acid chemistries fully charged since Absorption can take hours.  Incomplete charge (Partial State of Charge, or PSOC) over time will result in battery murder.   

How to avoid (or attenuate)  battery murder with this scenario:

• get access to shore power every couple of days to get the bank fully charged.  This will retard the murderification process; or
• use a different (and $$$) battery alternative like LiFePO4 (no problems with PSOC) or carbon foam (needs full charge every couple of weeks?); or
• add in a small amount of solar.  

The solar add-on is probably the best option, and can be done for cheap.  Given regular alt charging, 100W would be fine, 200W would be rainbows in the sky and unicorns dancing around your camper, and 50W would probably be sufficient for a 110Ah bank.

The reason for this is related to how lead-acid banks charge;  they can take a ton of current in the first 80% of charging (Bulk) then they hit a kind of wall.  At that point you could drive 100mph or hook the bank up to the Hoover Dam's electrical output and it wouldn't finish charging much faster.  It takes time, but relatively little power. 

From 80% to 100% (Absorption) requires little current but a long time holding at a relatively high voltage.  So in our alt+solar scenario the alternator does the heavy lifting in first bit and then a small solar install does the light (but lengthy) work at the end.

 

[rina]

Will Prowse recently posted an ULTRA cheap but effective solar system.

 

[Boyntonstu]

You guys are lead-acid-Aphobic and I don't blame you.

Heavy, expensive (Bob paid $1,000 for 4 6V AGM golf cart batteries), 50% discharge, extremely hard to fully charge...  Have I left something out?

IMO The best DIY alternative that avoids the LA battery issues would be to use 18650 laptop cells.

As for solar charging, I recommend series charging the Lithium battery.  

I use a constant Voltage lab quality power supply precisely set at 48.0 V to charge my cells to 4.0 V (average).  Yes, I do check for imbalance but I have never needed to balance charge.

If you used a Zener to limit the solar panels to 12.0 V, the 12 V Lithium battery cells would be happy and last a very long time.

I run my bike between 4.0 V and 3.8 V every day.

Don't be greedy when it comes to battery charging is my rule.

Just thought of another way to charge a 12 V Lithium battery after I discovered the site below.
Use a separate solar panel (3 total) and a charging circuit (3) for each 4.0 V cell.

https://www.homemade-circuits.com/2013/03/simplest-safest-li-ion-battery-charger.html

 

[highdesertranger]

Peltier cooling units are very inefficient. they do not cycle, so 10A means 10A continuously, 24/7. plus they will only cool 40 degrees below ambient, which I feel is over optimistic. in real life I found it to be more in the range of 30 degrees below ambient. so if it's 90 out the inside of your cooler will be 50-60 degrees, not safe for food storage. IMO don't waste your money on Peltier units. an ice chest would be a better option. highdesertranger

 

[Boyntonstu]

Thanks for pointing out the limits of Peltier cooling.

The photos show them all iced up and I was led to believe that they could cool to 32*F.

 

[Stargazer]

"Cheapest Non-Solar Solution for Minimalist?"

My first van, I used the X-treme Ice Chest, two solar rechargeable and battery operated lanterns, iPhone for Internet and music, and Nook tablet for books.  That was all.  Recharged the phone and tablet using the starter battery.  Never had a problem!

No other source of power.  But no laptop, no TV, no stereo, nada.  Worked great for me, the almost extreme minimalist.

Best wishes.

 

[highdesertranger]

they can go 32 and below, the ambient needs to be 62 and below and you are still using those 10A's. highdesertranger

 

[Boyntonstu]

they can go 32 and below,  the ambient needs to be 62 and below and you are still using those 10A's.  highdesertranger

Are you referring to a commercial Peltier refrigerator or to the Peltier unit itself?

I saw a very crude Peltier device about 45 years ago in a demo. 

At room temperature, the scientist grew ice on the Peltier unit.
At the end of the talk he reversed the leads and boiled it off. 
[font=Roboto, arial, sans-serif]
[size=medium]If you reverse connections you are still starting from "P" but now hot and cold will be flipped. They are polarized, but the only "bad" thing about reversing the polarity is, the hot side gets cold and vice-versa. So you can use one side of a peltier as a heater or cooler by simply reversing the polarity.[/font][/size]

 

[highdesertranger]

yes, by reversing polarity they can warm. but the same 30-40 degree temp change still applies. highdesertranger

 

[Boyntonstu]

A possible circuit to limit a solar panel Voltage to 12.0 V in order to series charge a Lithium battery to 4.0 V per cell.

http://www.electroschematics.com/6899/12v-ldo-solar-charge-control/

 

[Spaceman Spiff]

Peltier cooling units are very inefficient . . . they will only cool 40 degrees below ambient

 . . . I was led to believe that they could cool to 32*F.

You are both sort of right.

Consumer grade peltier coolers are lucky to get a 20ºC temperature differential.  Lab grade peltier effect coolers can achieve up to 70ºC temperature differential.  Consumer units are in the $100s range, lab units are in the $1000s range.  This is mostly a function of the materials used in the Peltier plates.

And they are energy hogs.  IIRC the lab unit I used took ~ 3,000 - 4,000 watts to reach a 50º delta.  According to my Mechanical Engineering Handbook, compared to an ideal Carnot cycle refrigerator peltier effect refrigerators average about 15% efficiency.  And their efficiency gets worse the bigger the temperature difference.  A reverse Rankine refrigerator (compressor/expansion system) can reach 60% efficiency.

And peltier coolers need to be run constantly.  This is because the heat from the hot side starts transferring to the cold side as soon as power is disconnected.

 

[highdesertranger]

yeah, I was going to mention that NASA and the ones on the ISS perform much better but they aren't consumer products. so I didn't mention it. highdesertranger

 

[frater secessus]

Consumer grade peltier coolers are lucky to get a 20ºC temperature differential.
...
And peltier coolers need to be run constantly.  This is because the heat from the hot side starts transferring to the cold side as soon as power is disconnected.

When I moved into this rental there was no fridge.  I found an Igloo 32qt peltier at a thrift store for $10;  it held right at 40F below ambient.  Since temps were in the 70s it worked great until I got a residential fridge.

I'll push back on the the "run constantly" claim.  In a situation where the hot side is fan cooled to the outside there is little hot left to transfer back when the unit is off.

On that note:  I'll be starting an experiment with that old igloo this week.  Going to add a temp switch to it and see how well it holds a given temp.  I suspect that in sub-70F ambient temps the switching will save a lot of juice.

I don't recommend anyone to buy a Peltier cooler new but if you find one at a garage sale and have a lot of power it could be better than an ice cooler.  Or at least fun to play with.  Like I say, the experiment will show if I am out in left field again.