Best way to charge house batteries: Solar or Alternator

I'm still leaning towards these craigslist high voltage types as they are $180 for 215w, whereas the low volt panels seem to be just as much for half that wattage around here, requiring two panels. I would just need a 20-30a MPPT charger, right? Is one like this for $145 shipped going to do the trick, or do I "need" a $400 Morningstar?

General Disarray said:

I'm still leaning towards these craigslist high voltage types as they are $180 for 215w, whereas the low volt panels seem to be just as much for half that wattage around here, requiring two panels. I would just need a 20-30a MPPT charger, right? Is one like this for $145 shipped going to do the trick, or do I "need" a $400 Morningstar?

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The cheaper one doesn't really have enough info to make a decision. The more expensive controllers will let you set it appropriatley to your battery. The cheaper ones will be generic lead, agm, gel settings which may be ok depending on the battery requirements.

Most "cheap" MPPT controllers are POSs. I have even seen be that performed worse than no controller at all, in spite of it's supposed MPPT capability.

With expensive battery banks, I would spend the money on name brand controllers, Morningstar, Xantrex are the best known, Midnight Solar is a great brand, but are (along with outback) generally too big for small RV arrays. Bluesky makes a number of acceptable small MPPT controllers specifically for the RV market. My personal favorite is the Rogue out of Oregon.

By any means, avoid BZ products, and many of the other off brands (IMHO)

Icarus

icarus said:

Most "cheap" MPPT controllers are POSs. I have even seen be that performed worse than no controller at all, in spite of it's supposed MPPT capability.

With expensive battery banks, I would spend the money on name brand controllers, Morningstar, Xantrex are the best known, Midnight Solar is a great brand, but are (along with outback) generally too big for small RV arrays. Bluesky makes a number of acceptable small MPPT controllers specifically for the RV market. My personal favorite is the Rogue out of Oregon.

By any means, avoid BZ products, and many of the other off brands (IMHO)

Icarus

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I guy I know has this one on his boat -- he's happy with it, and it's sized to fit RVs and boats:

http://www.emarineinc.com/products/Blue-Sky-2000E-12V%2d25A--350W-Solar.html

^That would be a Bluesky controller, one of the (reasonably) good guys. I actually own one, in standby service behind a Rogue.

Icarus

If you use small solar panel you can leave it on almost all the time, no charge controllers
minimum dollars outlay just a voltage check occasionally.

Amboman said:

If you use small solar panel you can leave it on almost all the time, no charge controllers
minimum dollars outlay just a voltage check occasionally.

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How "small"?

So, I'm assuming I'm on the right track with the logic of one HV panel (215w) for $180 covering my needs and being more economical than my other local options of LV panels @ $150/75w and $250 for $135W. I'd like to just jump in and get something going before my trip in May. One of the these HV's, a Bluesky MTTP @ $245, and I'm in for $450 plus the batteries. This might work. Anything I'm overlooking?

Again, the alternative is a low voltage panel and pwm controller. You can purchase a very nice 20A pwm controller with temperature control for about $20 on ebay. I just purchased the 10A version on ebay for $13 a few days ago to charge a small agm battery.

Have you measured your fridge current yet? That would be the first step.

Haven't "measured" it. Its a 55w unit; says its .08kw/24 hours on sticker. That's all I know for sure at this point. Doesn't that put me at about 40ah per day with the fridge? I definitely need over 100ah in batteries then, right? I think I'm going to buy 1000ah in batteries, and 500w of panels just so I don't have to do the math

I know about pwm/low volt panels typically being cheaper. What I'm saying is locally the lv panels are $150 for 75w or $250 for a 135w. Anything else involves shipping up here to the little mountain town I'm in. I can instead buy a used 215w high voltage for $180 from a dude on craiglist, and voila I own panel with the wattage I need. I guess I could shop around on the interwebs for a good deal on low volt panels, but that sounds like work (and I'm not very savvy at that sort of thing). Anyone know where cheap panels and or batteries I can order into my little mountain town?

If refrigerator is a 12 volt DC and 120 volt AC, buy a "kill-0-watt" meter. Plug refrigerator into 120 volt and measure actual amperage. My Dometic 80 liter refrigerator draws 4 amps DC or 0.4 amps AC. Refrigerator runs maybe 1/3 to 1/2 the time depending on interior van temperature.
The maximum size of the solar panel (s) might be determined by the capacity of the solar controller. My Morningstar Sunsaver MPPT model SS-MPPT-15L is rated at maximum 200 watts for nominal 12 volt panels and 400 watts for nominal 24 volt panels. I have been satified with that controller. I paid $238.43 on 8-3-10 to Northern Wind and Sun for the controller.
Thanks to NBB, I now would buy a nominal 24 volt panel of 200 to 240 watts and use it with the Morningstar controller. The 240 watt Canadian Solar # CS6-240 I found is the same length as my existing panel and 13" wider. It will fit and still be stealth.
My existing system has a 12 volt 135 watt solar panel. The existing system on sunny days about matches the power required for the refrigerator. It would be nice to have a bit more available to have some excess above my normal use. I normally never have to charge the 255 amp-hr battery with my second "vehicle" inverter or shore power.
Since the 24 volt panels cost less and a MPPT controller that can reduce the voltage down from 24 volts to 12 volts, that seems to me to be the best solution.

Thanks Dave. Sounds like a great system.

1) where do these 255ah battery arrays come from? At what $$?

2) are there 200+ watts of panels to be had, to my door for $200? Can seem to combine search words in google that can get me to the bottom of this ??

3) what exactly do I need to charge the battery off the factory alternator as a backup for cloudy days? A solenoid and cable? What exactly?

My fantasy is to get the supplies together at a good low cost, and drop the whole thing off with someone who can wire it all up for me. I don't want to pay the mark up that our local solar dude putts on his parts after investigating for myself. His 75w panels are $150 for chrissakes! Now that I know better, I don't want to deal with him at all.

1.The 255 amp-hr is the 8D AGM battery that I have.

2. Search for 24 volt nominal solar panels to find a panel around 200 watts. Hopefully you have added up your loads so they are compatible with the size of the inverter and solar panel. I priced the 240 watt solar panel at $237.60 to be picked up locally. Generally panels larger than 135 watts can not be shipped UPS so finding a local source can save freight costs on the larger panels.

3. There are several ways to charge the battery from the Sprinter that have been described to you. If you do not understand, then try to find someone in your area who can help.

This is just my observation of this thread - you could save money to assure quality deployment of the electrical conversion by going to know-how folks. This thread is active for the last 6 months and it seems it is still steep learning curve for you. From the distance this thread is a little like driving on a roundabout from the "European Vacation". Perhaps someone can help you to evaluate your expected load including getting correct data from the fridge and design and build your conversion with local resources.

You can save money on components but null these savings once a know-how installation person will need different items. A wrong PV panel can set you off by hundreds.

Good luck,

George.

GeorgeRa said:

This thread is active for the last 6 months and it seems it is still steep learning curve for you. From the distance this thread is a little like driving on a roundabout from the "European Vacation".

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Well, frankly your "observation" is a bit dismissive and unnecessarily condescending. Actually the the thread is 6 months old, but there is a four month gap of dormancy between Dec and March; I resurrected it a month ago to ask for more details. I started this thread not knowing anything about either method, and I think my last few posts demonstrate I have a pretty good grasp on the various options for charging batteries. At this point I'm wondering where folks are getting their AGM's at good prices, and a few minor things. But for the most part Ive learned a lot with this thread, and am incredibly grateful for all the contributions; save one or two unproductive ones

Wow, I made it thru this entire thread and learned a lot... I often use the principle that when there are more than one way to do things, and in the lack of compelling research that shows one way is significantly better, then the prudent decision would be to take the easiest and cheapest route. At this time, still awaiting the arrival of a '14 4 cylinder Sprinter, and having pretty much the same needs as the OP, I am planning on an aux battery / relay as supplied by the dealer (I didn't order it, so it will have to be after delivery add-on, which hopefully the dealer will do)... I don't understand electricity but I trust MB does. Thank you all for helping me make a decision.

I am considering a similar plan. Boats often use dual alternators, or have selector switches to switch from onboard genset power to alternative 110v. National Alternator makes a dual alternator kit with MB parts that allows you to add an additional alternator (MB offers this on Sprinters from the factory). Its, not cheap, with the v regulator its close to $2 K for the parts, then you need a selector switch, probably a set of relays to control the alternative power sources, and of course labor. I suspect you'd be in for about $3500. The kit offers a 200 Amp second alternator, so assuming you run load at a max of 75% that is 150 amps continuous load @ 12 volts. Since we know that Volts x Amps = Watts we can figure that at 12 v X 150 amps is 1800 watts. divide by 10 to convert 12 v to 120 v and you have an approx 15 amp circuit, should be more than enough to drive the AC on low, probably high speed. The original alternator would keep the batteries charged, and run the fridge. Just don't use the microwave and AC at the same time. Outfits that build ambulances or the like can probably do the work. The trick is you don't want to butcher the existing electrical system, that's why I'd use the additional alternator and inverter, basically creating a parallel system that you select between.

http://www.nationsstarteralternator...tor-Kit-with-270-Amp-p/sprinter-dak-270xp.htm

rrm said:

I am considering a similar plan. Boats often use dual alternators, or have selector switches to switch from onboard genset power to alternative 110v. National Alternator makes a dual alternator kit with MB parts that allows you to add an additional alternator (MB offers this on Sprinters from the factory). Its, not cheap, with the v regulator its close to $2 K for the parts, then you need a selector switch, probably a set of relays to control the alternative power sources, and of course labor. I suspect you'd be in for about $3500. The kit offers a 200 Amp second alternator, so assuming you run load at a max of 75% that is 150 amps continuous load @ 12 volts. Since we know that Volts x Amps = Watts we can figure that at 12 v X 150 amps is 1800 watts. divide by 10 to convert 12 v to 120 v and you have an approx 15 amp circuit, should be more than enough to drive the AC on low, probably high speed. The original alternator would keep the batteries charged, and run the fridge. Just don't use the microwave and AC at the same time. Outfits that build ambulances or the like can probably do the work. The trick is you don't want to butcher the existing electrical system, that's why I'd use the additional alternator and inverter, basically creating a parallel system that you select between.

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I installed a Nations Alternator system, more or less as you describe:

https://sprinter-source.com/forums/showthread.php?p=394758&highlight=nations#post394758

These kits are rated at 270 Amps, not 200. They produce 200 amps at idle, and they really do deliver this. My system does not interact with the Sprinter charging system in any way. There is no need for any selector switches or relays--the Balmar (which BTW is a true, programmable 3-stage charger, not just a regulator) takes care of everything. You can wire the alternator output directly to the house bank. All you need is fuses. Installation is pretty much bolt-on. There is no way it would cost you $3500, unless you are including the inverter.

My system can run the A/C without skipping a beat. It will also bulk-charge my 440a/h battery in about an hour's driving.

In case it is interesting, Suniva makes very decent panels in the 200 and 300 watt (nameplate) range. Even made in the US.

A friend of mine suggested that it might be better to make the panels removable, so a person can park in the shade, and put the panels in sunny areas.