Too much or too little Solar?

[Almost There]

I'm a bit confused. I get all the math, but I don't get how I'm seeing all of these builds on youtube and elsewhere where people have fridges and microwaves and TVs and one or 2 100W solar panels to run them

Ha, you're still believing everything you see on the internet as being true...

 

[Seraphim]

I'm a bit confused. I get all the math, but I don't get how I'm seeing all of these builds on youtube and elsewhere where people have fridges and microwaves and TVs and one or 2 100W solar panels to run them

I can't help you there - we keep our needs minimal and don't use AC powered devices off our batteries. We generally use about 25 amps a day - highest has been under 35 - on a 400 watt system with 210ah battery capacity. I can't offer much experienced advice since we never seem to run our batteries down even though we live in the east and have a lot of overcast skies.

I know there are people like Bob who have - in addition to solar - generators, or charge off their alternator like Sternwake (I think it was). Also, you have to take some bloggers with a grain of salt sometime. I trust the people here, because I know there are knowledgeable people who can spot an unrealistic claim lol.

But I think you might be asking more of your system in total than some others. Again, I'm no expert.

 

[SternWake]

One certainly cannot believe the claims one reads online, and I have seen a few claims, no0t recently though, on this site which are a bit ridiculous.

Factors to keep in mind, is the alternator, properly cabled, can do in under an hour what it takes 200 watts of solar on a sunny day to accomplish.

Do one hour of driving in the morning and let the solar top off the batteries the rest of the day, and much is possible.

Not having that alternator blast changes what is possible.

Any and all charging sources need to be employed whenever possible whenever the batteries are less than full charged.

Returning the batteries to full charge as often as possible, will extend their life and allow good performance during that life.
After 14 cycles without returning to full charge, only then it becomes noticeable  via voltage under load that the batteries have walked down in capacity.

Extra time and voltage must be applied at this point in an attempt to regain lost capacity from these abused, punch drunk batteries.

A solar controller which allows one to change absorption and float voltage can be vital for getting a battery to 100%.

Being able to plug in to the grid or have a generator to power a charger which can do 16V's can do a proper equalization and keep batteries happy

Letting the batteries to sit for days never getting above 50% or 80% charged will kill them quickly.  Even the venerable t-105.

Often you will hear claims of " I haver this and do this and it works 'just fine' "

Just fine = Has not yet failed, still meets my needs.

You want to impress me? Claim this and that and to be on your 500th deep cycle( 60% or lower)  and everything is still 'just fine', and I won't believe you. Not if you've got lead acid batteries.

If you can prove it, I'll salute you, and eat my week old underwear.

I'm approaching my 400th cycle, and the capacity loss is obvious, and it still meets my needs, but you'll not catch me saying the battery is 'just fine', even though my system is close to optimized.  I've got the tools and the experience to measure their performance.

My poor battery is working hard for its living.  The limiting factor is the 12 volt lead acid jar.  6v would be better, but I cannot fit their height into my system without too much other compromise, and if I could, I'd only expect 40% more cycles at the best.

However much amp hours storage you have, attempt to double this in solar wattage. 1 solar watt per 1 amp hour of storage should be considered the absolute minimum, in my opinion.

Limited on rooftop space? Limit total amp hours capacity, and find ways to consume less electricity.

Unwilling to? Then prepare to replace batteries more often. 

How often?.... depends on how well you can meet the info specified above.

 

[akrvbob]

200 watts and 2 golf carts will run a 12 volt compressor fridge no problem, I've been doing it for years.

If you want a microwave and a 12 volt fridge I'd recommend a minimum of 400 watts and 4 golf carts.

I have 570 but I never even tax my system. I have a microwave, 12 volt fridge, and watch 4 hours of satellite TV at night.
Bob

 

[Seraphim]

So Bob - yu never use your generator?

 

[Seraphim]

And how many amps do you use a day?

 

[Matt71]

Ok I think I have this worked out


Powered via Shore or Generator Only

1 - BluRay Player (2.5Ah @ 12V)

1 - Projector (21.5Ah @ 12V)

1 - Frigidaire 5,000 BTU Window-Mounted Air Conditioner (48Ah @ 12V)

1 - Westinghouse WCM660W 600W Microwave (50Ah @ 12V)

1 - Sony Laptop (12Ah @ 12V)(might not bring)



Powered Via Solar - 130A per day total

3 - Gold Stars GW21500 RV Reading Lights (0.78Ah @ 12V)(4A per day)

1 - Roadpro 12 volt oven (12Ah @ 12V)(12A per day)

1 - A MacbookPro w/ 85W Adapter (7Ah @ 12V)(42A per day)

1 - cPap (6Ah @ 12V)(42A per day)

1 - Fan (3Ah @ 12V)(30A per day)



Battery Bank

4 - Trojan T-105 6V 225Ah Batteries



Solar - 111A (estimated) per day at 60% sunlight for 5 hours

3 - 210W 18.5V Panels

1 - Renogy® Tracer 4210 40 Amp MPPT Charge Controller

1 - 12V 2000W Pure Sine-Wave Power Inverter



Generator

Westinghouse WH2000iXLT 1800W generator


We won't know until we are on the road how much we will actually be using the computer, but I estimated it at 6 hours per day between the two of us which is way less than we use it now, but we will be busier and won't have the internet to eat away our time like we do now. And when we do, we'll probably be on shore power anyway. I might also go down to a 1000W power inverter to save a hundred bucks. Now that I've pared things down I don't think I'll need the 2000W. I didn't calculate in phone and tablet charging, but I'm guessing that won't eat up much power.


So, am I finally being reasonable?

 

[Seraphim]

Looks like reasonable expectations to me, and you've got got everything covered for any situation, even days worth of rainy weather. And there's always the alternator.

 

[Matt71]

I read that using your alternator to charge your house batteries isn't a good idea because it can overtax the alternator.
If I could do that without risking damage it would make things a lot easier.

 

[Seraphim]

I'm curious as to how the alternator could be overtaxed. Unless it means the alternator won't be able to charge cars battery as well as it should because it's sending amps elsewhere.

 

[Matt71]

I don't remember what the exact issue is. The only part that really stuck in my head is that it's not an ideal set-up.
It's completely possible that I've been misinformed

 

[SternWake]

Idling the engine to spin a high output at(at Idle speed) alternator, can overheat it.

When driving, the airflow under the hood allows it to pull cool air through it, and keep it cooler

No doubt asking it to produce all it can degrades ultimate lifespan. no arguing that.

Nearly every time I drive I max out my alternator those first few miles.
It has been doing this for 7+ years, an I have a slightly smaller pulley on it to make it spin faster.

My alternator is easy to replace, and cheaper than a single Deep cycle battery, so for me it is a no brainer.

Those really worrying about their alternator health can limit wire sizes between alternator and house battery to no thicker than 6awg, and should have no issues and still get a respectable amount of amps from it.

Those wanting to harness everything the alternator can make at any given rpm into depleted batteries should go for 4AWG or thicker cabling.

Banks of AGM's batteries are more prone to overloading alternators when the cabling is adequate.

Boaters rely on their alternators, and their engine compartments are way hotter, granted their alternators are more HD than automotive Alternators, but they tend to get good lifespans from them. Worst thing to do to an alternator is to remove the load from it when it is making a good output.
POOF go the diodes.

I have plans one day to make a cold air intake for my alternator, but I developed these plans many years ago, and have not bothered.

Idling to recharge is a waste of gas anyway, especially when one has a generator.

 

[Matt71]

We plan to drive quite a bit, especially when we won't have shore power, so we won't be idling.

I assume we could also charge the batteries when hooked to shore power as well with a speed charger like THIS ttp://amzn.com/B000H961YI

 

[Seraphim]

Our truck camper was already setup with a charging system - it charges off shore power and the truck alternator. Our solar setup is only necessary for long extended stays while boondocking. When we drive every day, the alternator charges our house batteries in a short time.

The only time I encountered any problems was on our old Class B - the house battery had died, and our alternator was powering the vehicle and running the 12v fridge. When we stopped and idled, the alternator was putting out insufficient power, and the engine stumbled. I turned off the fridge. That was a one time occurrence. I use a propane fridge now. But the Class B was setup the same way - alternator and shore power recharged the house battery (which was only 75 AH - and it was old, which was why it died).

Sternwake has posted instructions for setting up an alternator charging system. There are diagrams online as well for an RV style electrical setup.

 

[Seraphim]

I don't see any concerns about charging off the alternator. I'd certainly look into a charging system for when you have 110v. Then the solar would only be needed for multi-day boondocking. If you're going to drive several hours each and every day, solar might be redundant.

 

[Matt71]

I'm betting the size of the alternator plays a roll too.
Ford E-250s either have either a 95 Amp or 130 Amp alternator depending on the year.
The 95 Amp alternator would probably have a harder time.

 

[Seraphim]

http://www.where-rv-now.com/Notes/Amp/2004Diagram.png





Sent from my iPad

 

[Seraphim]

I'm betting the size of the alternator plays a roll too.
Ford E-250s either have either a 95 Amp or 130 Amp alternator depending on the year.
The 95 Amp alternator would probably have a harder time.

Yes. You can upgrade the alternator. My diesel has two - the second was added in case the owner wanted to use a snowplow. The snowplow upgrade cost me about $245 when I bought the truck. Each about 145a, I think...

 

[SternWake]

With 4 t105's you are best off with as high a charge rate as your generator can provide.

An RV converter like an Iota has an absorption voltage of 14.8v which is what Trojan recommends.

I would not go less than a 40 amp charger, with the dls-55 being even better.

An RV converter is designed to 3 stage charge batteries, while also powering 12vDC loads
A regular battery charger, will get confused and shut off when loads on the 12v system increase or decrease.

http://www.amazon.com/DLS-55-AUTOMATIC-BATTERY-CHARGER-SUPPLY/dp/B0074JVO0A

The problems with converters, and all automatic chargers, is that they stop too early. Which is OK when one has grid power and 25 hours to fully recharge.

But when trying to minimize generator run times, and the charging source drops voltage prematurely, then amp flow and recharging comes to a near standstill. while at 14.8v the batteries might have been accepting 15 amps and are 85% charged, once the voltage drops to 13.8 or less, then the amp flow drops to 1 to 2 amps, if that, and getting those last 35 amp hours into the batteries will take another 10 to 15 hours.

Since Lead Acid batteries behave better the higher on can recharge them each cycle, then one finds a charging source which does not prematurely fall to float voltages is quite advantageous.

Now I bring up the following product for those interested in getting to as high as possible a state of charge as possible while allowing the generator to run.

These are fully manual products. nothing automatic, no stages, it is an adjustable voltage power supply. The human charging the baqtteries needs to insure that absorption voltages are not held too long and overcharge the batteries. It is a frontal lobe charger, requiring one use their brain. It is not for everybody. It requires one to set 14.8v, or whatever absorption voltage the battery manufacturer recommends, when there is no load on the power supply, and mark this level on the dial with a sharpee of piece of tape, and also set the float voltage when not loaded, and mark that.

http://www.bestconverter.com/Boondo...ower-ConverterCharger_p_585.html#.VNKavNLF_cw

Do note that powerMax makes 4 stage units as well. The ones purchased from Bestconverter have higher absorption voltages(14.6) compared to if one were to buy one from amazon (14.4). These powermax units in the 75 amp or Higher amperage are power factor corrected, basically more efficient, and can be operated off of a standard 15 amp household outlet. The Iota dls55 is right at the edge of being able to run off of a 15 amp outlet.

I bought a Meanwell RSP-500-15, to which I have added a 10 turn potentiometer to dial in voltages, I've a thread on it here:

https://vanlivingforum.com/Thread-My-newest-electrical-toy


Now people tend to shy away from high amp charge rates and tout the 'trickle charge' as the best way to recharge a battery. Get this though out of your head in this lifestyle completely, and smack the first person who suggests it to you.

trojan recommends a 10 to 13% charge rate when charging via a plug in charger. 10 to 13% of the amp hour capacity(20 hour rating).

So 4 t 105's at 464 AH. 13% of that is 60.32 amps!

Do not fear the high amp charger. It is your batteries best friend in this lifestyle.

My flooded 31, a 12 volt battery, easily accepts 41 amps for over an hour when 50% charged, and USbattery recommends a 10% rate, which would be 13 amps.

Do not fear the high amp charger.

Best Converter also sells a 100 amp adjustable voltage Powermax. One has to order it, and they are easy to get a hold of. These are made to order and not on the website. My friend's 100 amper just arrived. It will be feeding two group 31 Northstar AGM batteries.

When the batteries are below 80% state of charge, they will accept everything the charging source can provide. then amps taper as battery voltage rises to the maximum set voltage( absorption voltage) of the charging source.

Full output can max out a generator so that it cannot power other things in addition to the charging source. One needs to factor this into generator choice and usage. I'm not sure what generators can power what chargers. I have no generator and have not researched them, or paid much attention to Max AC amperage a powerful charging source requires.

 

[SternWake]

Also the adjustable voltage powermax, or meanwell can properly Equalize a battery bank. The powermax sits says max voltage of 15.5v and 16V can be required on some stubborn batteries. I plugged in my buddues powermax yesterday and unloaded, it was able to provide 16.4V.

How often an EQ cycle is needed varies a lot with battery brand and usage and how well they are recharged. An EQ cycle is abusive to a battery so should not be performed more than necessary to even out the Specific gravity cell to cell.

It is a forced and monitored overcharge, and is like a reset button on a punch drunk battery bank. One needs a good hydrometer, a voltmeter, and a charger than can do at least 15.5V to perform an EQ cycle.

Stop when Specific gravity no longer rises, or battery temperature exceeds 117F. Do not exceed 16 volts.

Do Not attempt with AGM or GEL batteries.