Why use solar if the alternator is giving off 70 amps?

[BigT]

No room for bank of batteries. Heck, there's barely room for 1! I may connect to the alternator later, but for now the plan is to charge by solar only.
No inverter, just going to run a few 12V items (CPAP, LED light, fan).

To be honest, the cost of the 20A MPPT ($139) worries me a little. It's the cheapest I've seen, and sometimes that's not a good thing. I need to settle on something, though, or I'm going to be planning this for the rest of my life.

That $56, 30 Amp PWM with the LCD display looks like it should do nicely.

 

[akrvbob]

My suggestion, flip a coin and buy one!
Bob

 

[BigT]

Thanks, Bob, I think I just did!

 

[jimindenver]

Actually the cheapest 20 amp MPPT charger can be had for as little as $85 delivered if you catch a ebay auction just right. I used them for 3 years with out a failure.

 

[Canine]

Hi all,

Sprintersnale nailed my issue with getting solar... In the SW, especially my current home base of Phoenix, I have to park in the shade a few months a year during the daytime else my van, even with its white top, gets too darn hot inside. That heat soaks into everything and radiates out slowly... But I would get good solars, at least 5-6 hours a day on fixed panels on the roof...

However, if I choose to park under the cover or in the lee of a building or tree, I wouldn't be able to use any solar, but the van would stay cooler... So which should I do?

One idea is to accept the heat buildup, then get in and run fans and vehicle ac for a few to like maybe 20 minutes to get it to cool down... Costing maybe a gallon of gas but having charged the battery or batteries with both solar and vehicle alternator. So what's the best idea during the triple digit months of May thru or and September, if I have to be here for work?

 

[SternWake]

I don't understand this concept of one or the other that some seem to be planning on.


Every and all charging sources should be employed whenever possible to keep the batteries as at high a state of charge as possible, within reason of course

Alternator + solar is a winning combination.  If you can't have  solar on a specific day, because you are parked in the shade, the alternator  is still a valid option to getting back upto 80%.  If you don't have to drive anywhere but are in the sun, well no big deal.  Silent free energy all daylight long.
  And if the Van is too freaking hot, don't hang out in it.

Plan on Solar now, and plan to run some copper to a solenoid too, If not now, then later.  It is not complicated.  No original vehicle wiring needs to be trifled with.  You are only adding a very simple circuit with vast potential benefits.  It is not rocket science.  It certainly is not an either or situation, even with budget limitations, as both need not be installed at the same time.

Initial expense will be made up in battery longevity.  Cycles per dollar.  Both solar and hooking the alternator up to Aux battery will extend your battery's life, and your comfort level, since stressing over your undercharged battery will not be nearly as much of a factor.

 

[highdesertranger]

I don't understand this concept of one or the other that some seem to be planning on.


  And if the Van is too freaking hot, don't hang out in it.

that first sentence says it all. the second one also makes a lot of sense. highdesertranger

 

[rvpopeye]

Ditto HDR

 

[Canine]

The option I would choose is to park it in the sun until about an hour before I'm off, then move it to a shaded spot. The low angle of the sun doesn't do much for a flat fixed panel on the roof anyway. Right now I don't worry about solar because I drive from 10-20 miles a day and use very little power in the evening. When I get a better van setup (re. flatter roof) I'll sure look at something simple like a 100-150 watt panel. Since I don't have a microwave or gaming device I don't care too much about power.

Great info all, always good to read and really consider things before a bigger purchase. I've finally broken myself of impulse buying or hurried decisions, so much money wasted by changing my mind when if I had just waited, the decision would have been different due to a change in circumstances. I try to use a 30 day rule at a minimum... For bigger things.

 

[johnny b]

if i had to go without solar and rely on alternator power, i'd add one of these:
http://www.sterling-power-usa.com/SterlingPower12volt130ampalternatortobatterycharger.aspx

a second alt on the vehicle would add reliability.

lawn mower engine + alternator + above charger would be an excellent portable charger.

but for the money, and vehicle reliability i'll stick with solar.

 

[SternWake]

I'd only consider one of those sterling DC to DC regulators, if the vehicles voltage regulator could never provide the battery's recommended absorption voltage.

While mine allows 14.9v, which is a bit too high, sometimes it only allows 13.7v maximum, when the battery still would enjoy time higher voltages.

Not ideal, but spending 450$ just for ideal alternator charging is not on my to do list.

My alternator is now something like 8 years old and is regularly maxed out by a depleted battery over thick copper, and is just a junky remanufactured model.


On a bit of a tangent....
Asking a alternator to work hard to recharge depleted batteries, certainly shortens its lifespan. How much shorter is a rather large variable.

Any new or remanufactured alternator should not be asked to work hard for the first ~500 miles. Make sure to fully recharge the battery before asking a newly installed alternator to begin life underhood. Many people with failed alternators have issues with replacements for this reason.

The brushes need time to mate with the commutator. If asked to recharge a depleted battery before this seating occurs, issues can arise with the brushes glazing over or getting stuck in their holders and not making contact.

 

[GotSmart]

if i had to go without solar and rely on alternator power, i'd add one of these:
http://www.sterling-power-usa.com/SterlingPower12volt130ampalternatortobatterycharger.aspx

a second alt on the vehicle would add reliability.

lawn mower engine + alternator + above charger would be an excellent portable charger.

but for the money, and vehicle reliability i'll stick with solar.

For $450 I could buy solar.

 

[Canine]

Hey SternWake, this may have been asked before, but how does the alternator figure out what to do with different types of batteries? I have read, probably from you, that AGM's and FLA require different bulk and float levels. If you have an AGM house battery and a standard FLA starting battery, are they both hooked up to the alternator and go through the vehicle regulator? Must not be else the alternator would "see" one or the other and either overcharge one or undercharge the other... I mean when it's running, what will tell the alternator, "time to stop charging the starter battery and give the house battery 15.3 V and lots of amps" unless they are wired separately and have separate regulators, with some sort of cut out for one or the other?

I admit to being stupid about electricity...

Thanks

 

[SoulRaven]

if i had to go without solar and rely on alternator power, i'd add one of these:
http://www.sterling-power-usa.com/SterlingPower12volt130ampalternatortobatterycharger.aspx

a second alt on the vehicle would add reliability.

lawn mower engine + alternator + above charger would be an excellent portable charger.

but for the money, and vehicle reliability i'll stick with solar.

With a lawnmower engine and an alternator you don't need a $400+ gizmo added to it in the first place.  I used just such a generator to keep my house battery charged for well over 20 years before I switched to charging while driving over a year ago.

I like solar for hot water, solar cooking can be fun, but solar for battery charging never worked out for me, and the expense is just plain stupid when there are better, more reliable, and far cheaper ways to have full time power.  I'll keep parking in the shade in the summer and actually enjoy hanging out in my van.
82

 

[Canine]

With a lawnmower engine and an alternator you don't need a $400+ gizmo added to it in the first place.  I used just such a generator to keep my house battery charged for well over 20 years before I switched to charging while driving over a year ago.

I like solar for hot water, solar cooking can be fun, but solar for battery charging never worked out for me, and the expense is just plain stupid when there are better, more reliable, and far cheaper ways to have full time power.  I'll keep parking in the shade in the summer and actually enjoy hanging out in my van.
82

So OG24/7, if you quit using a gennie to charge with, you either have very minimal power needs (like me at the present) or drive enough to top off your house battery. Which is it, or some of both?
I will pay a price for inefficient engine and alternator usage if it is nominal as opposed to fast idling for an hour a day. I wouldn't do that. If I ever leave the urban areas, like this summer when the Phoenix heat arrives, then I have more difficulty keeping charged, that's where a small solar battery top off capability would be nice.

 

[SternWake]

Dusty, the vehicle has no idea what type of battery it is trying to recharge. If the battery does not like the voltage the vehicle voltage regulator allows, then tough shit.

Influencing the voltage regulator to do one's bidding is not easy. That sterling product linked is a solution, albeit a 400$ solution. Other methods exist too.

Topping off a depleted battery requires time at high voltages. There is no speeding up the process without forcing the battery to higher, damaging, voltages.

Assuming that a 20 minute drive is topping off your batteries is extremely unwise. Assuming it is being recharged at a good rate is unwise.

Without tools to measure voltage and amperage, one remains absolutely clueless as to battery state of charge or recharging currents. Any claims as to how charged a battery is without the tools and desire and knowledge to measure it, are unwise.

It works or it does not. That is all 90% of people will ever know about their battery. It is a shame when those 90%ers give advice on something they have no grasp of. Bigger shame when those trying to learn, listen to them, and put any weight on their words.

 

[Canine]

Now I'm not sure if I just got spanked or what...

I'd still like to know if there's an acceptable way, either separate wiring and separate regulators, for the alternator to send a different amount or length of charge to one battery vs the other. I wouldn't want to be chronically under or overcharging, if and when I ever get a second battery set up. Alas, I am in the 90%... Sigh. Back to my ice cream...

 

[SternWake]

No spanking was aimed at you dusty.


Batteries are tolerant enough of different charging voltages that stressing about too high or too low Not being ideal, is a waste of time.  Just be aware of the voltages, and don't expect short drives to fully charge the battery.  

Some AGM's might not like voltages higher than 14.4v.
Mine is one, and my Van allows 14.9v.  This AGM is now 18 months old and a recent capacity test revealed its capacity is still  very good and this 14.9v it sees regularly, every time I drive, has not damaged it.

Overcharging is not likely in most set ups, undercharging is.

You cannot really depend on the alternator to top off the battery, but it certainly can be used to get a battery in the 80%+ range. and a battery returned here daily when driving  daily can live a fair lifespan.

Maximum lifespan is achieved by 100% recharges as often as possible, and this can be taken to extremes vs the method where one can just plan to replace batteries more frequently.

If your needs are light, a marine battery, a simple solenoid, and 4 awg copper between alternator and Aux flooded marine battery will meet your requirements for quite a while before you even notice the capacity loss.

If you are stressing your Van's maximum allowed voltage, put an inexpensive digital voltmeter  with a voltage sense wire right on the (+) of the engine battery.

 http://www.amazon.com/DROK-Display-...825&sr=8-10&keywords=digital+voltmeter+3+wire

I've got two of those, in green, on my dashboard. One for each of my batteries.  Now one just reads 0 as my flooded battery is removed