Should I?

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mconlonx

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http://www.solarsystems-usa.net/solarpanels/talesun/tp660m-255/

I'm planning to go solar on my current build and have an opportunity to pick up a 255w Talesun panel, cheap. $100 cheap.

Thought was to start with a battery charging off the alternator and eventually go solar, but now this comes along and seems like a deal. Advertised as "24v output, but can be made to work with 12v systems."

I don't know enough to believe or refute this...

Based on what I've been picking up, but with no solid research, I was thinking 250w would be the way to go. For: internal 12v LED lighting, charging of phones and laptop, perhaps a small Dometic fridge, CO/propane sensors, roof vent fan, and misc aux equipment. I'll be cooking and heating with propane, no needs for big draw power tools, air conditioner, microwave, hot plate andthe like.

Sound reasonable so far?

Immediate question is: can this panel be made to work?

Follow-up questions would be:
Assuming this panel, controller suggestion? To also accommodate draw from van electrics and possibly shore power?

Sane battery setup?

I know a lot of this is "It depends..." and if more info is needed for the follow-up questions, then more immediately, should I jump at this deal?

Other 250w panels I've been scouting are usually $200+...
 

loess

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That panel looks good to me! As for a charge controller, definitely take a look at the Rogue MPT-2024. It will take your 24v panel and feed the current into a 12v battery bank, no problemo. Used to be that you had to pony up big bucks for the MPPT controllers that were designed for larger solar arrays, but Rogue came along and put a ton of great features in a smaller more affordable unit. They are made in the USA, high quality, and a small company that backs up their products with integrity and honest customer service. Matter of fact I called them on a whim when I was in a similar situation to you and had found a killer deal on a barely used 24 volt 235W Astronergy panel. At the time I had barely dipped my toes into trying to make sense of all of this solar stuff, but I had to move on the opportunity to buy that panel quickly. I wanted to be sure before I bought it that it would work with the MPT-2024 and Marc from Rogue spent a bunch of time on the phone with me and gave me all the info I needed.
 

SternWake

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All 200 watt +panels are going to be high voltage panels requiring MPPT controllers.

there are some less expensive MPPT controllers out there but stick with the Non Ebay chinese ones. The Rogue is good.

Please elaborate on this part of your question:

To also accommodate draw from van electrics and possibly shore power?

Any Solar is better than no solar, but having too much solar is difficult. The best solar systems are those which can keep the batteries the happiest.

Happy batteries are those which are recharged quickly after depletion. Many try to size solar to be able to replenish amp hours used by end of day. But at least 105% and upto 150% the amp hours removed must be returned, to fully recharge.

I think that on a good sunny day the controller should be in acceptance stage by 11 AM. This means that on a not so sunny day the same system has a much better chance of getting the battery bank back up to near 100%

A solar controller which has adjustable acceptance and float setpoints allows the user to fine tune the system for the specific batteries.
Like Trojan t 105's want/ require 14.8v acceptance. A controller which only does 14.4v will not keep the trojans healthy and happy for a long time.

RV converters are good 'shore power' power supplies and battery chargers/ Iota., Progressive dynamics. Powermax are 3 good ones. One should have a means of charging via the grid, and higher amp converters can help to wake up a battery bank that has been kept in the 50 to 80% range for whatever reasons.

I think you can get away with 2 golf cart batteries with that 250 watts. There is a tendency for people on this forum to want gobs of capacity, just to have apparently, and then have undersized solar for that large capacity.

All battery manufacturers will list minimum bulk recharging currents and usually solar is woefully inadequate at meeting these rates, so having a higher solar wattage to lower battery capacity ratio will be better for the batteries, unless of course you are cycling the batteries below 50% every cycle.

But your listed intended draws are not huge. 250 watts should be more than adequate, and a pair of GC-2 golf cart batteries should be more than enough capacity and are very tolerant of deep cycling.


While the panel itself is a great deal, you'll need a rather expensive MPPT controller.

If you get smaller solar panels that are nominally 12v ratedwired in parallel, not series, then you can get a much less expensive PWM controller. Still shoot for that 250 watt range though. Very hard to have too much solar. Shop around, decide what you can fit on your roof

If one has too little solar, then it must be considered as a usage offsetter, and not as a proper recharging source. This is fine for some who want to make a battery last for an outing of a few days, but not for the full time dweller hoping the solar and the solar alone can take the batteries back to 100% or nearly so every day, day after day.

Now if other charging sources are regularly applied, like the alternator and a thicker alternator circuit, or an Rv converter or other stand alone grid powered battery charger, then one can get away with less solar and get a good lifespan from the batteries.

But when the primary recharging source is to be solar, one needs to match the battery capacity to the Solar wattage a bit better, and make sure their usage does not exceed that 50% discharge level, and a shooting for no less than 65 to 70% State of charge is better.

It is easier and much less expensive to use less electricity than it is to create and store gobs of it.
 

akrvbob

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kyonu

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Curious--I'm seeing a pallet of panels for $5393 bux, which makes all 25 roughly $215 a piece. How are you getting it for $100~? Cuz now I'm interested!
 
D

Donedirtcheap

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Stern said it well. Dont go below 50% and buy a hydrometer and a pair of safety goggles. The bottom line in battery life will depend on specific gravity not voltage readings. You can even get good voltage readings on a battery that is low on water or has a weak cell but you cant fool the hydrometer. I'm not ready for solar yet but I would imagine that I want an adjustable volt so I can approach 15 volts. You will be able to do 13.6 or 14.4 volt charges for a short time but at some point you do need to hammer the voltage up to prevent sulfation. You need to drive the battery to gassing. Some converters are 4 stage with the 4th stage being desulfation at a predetermined interval.

https://www.google.com/search?q=bat...2%2Fviewtopic.php%3Ff%3D6%26t%3D56378;793;271
 

SternWake

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Some converters are 4 stage with the 4th stage being desulfation at a predetermined interval.

This is not correct. Basically any time you charge a battery it is being Desulfated. Some chargers claim a special desulfating feature which claims to break up hardened sulfate and return it to the electrolyte there by freeing up surface area on the plates and allowing a full recharge. I personally think this is more marketing than actual engineering, though some claim it is effective.

The 4th stage on some converters, which up the voltage to the mid 14's every so often after the converter has taken the battery upto "100%", is intended for DESTRATIFYING the acid on a sitting battery, by causing bubbling every so often, that it mixes up the electrolyte so the stronger acid solution does not seek the bottom levels and become more corrosive to the plates. Just the motion of driving can destratify a battery.

And how many people on this forum actually sit in one place with a converter plugged in day after day that this 'destratification' 4th stage is even going to occur?

Some other misinformation by those in in the marketing department of chargers concern the term equalization.

Equalization is an intentional overcharge of a flooded battery. After many cycles and after a regular recharge, the individual cells on a 12v battery can and will read differently, ie 1.280, 1.290, 1.265, 1.270, 1.270 and 1.275. The equalization, this forced overcharge is an attempt to get all the cell's Specific gravity up to that 1.290 level. This can take hours at 16 volts to achieve, and is pretty hard on the battery, but cells sitting undercharged for a long time is harder on it.

The equalization cycle is kind of like a battery reset. After a proper EQ charge cycle is performed the battery will be at its maximum energy density, however much is remaining. Some manufacturers recommend one every 30 days but this varies. The way to know is with a Hydrometer.

Many batteries that "no longer hold a charge" really just need some lovin Via a good EQ cycle.

My flooded battery needs an EQ every freaking week, and I screwed around with different voltages to do it, 15.2, 15.5, 15.7, 15.9 and guess what, the most effective is 16 volts. I can apply 16v, through my solar every week and get the battery back upto 1.285 on every cell and then it performs nicely. This is with a 14.8 volt acceptance setting and my float setting is 15.1v. Much higher settings than most every charger out there will apply. I use the float as a "finishing" charge, but if I were to stop cycling the battery I would lower float voltage to 13.2v or whatever.

The lower my Acceptance and float settings the lower and lower the SG falls every cycle, and the longer the EQ cycle needed to restore the SG back upto maximum baseline. The 16 volts minimizes the time required to max out the SG. I've gotten it down to 45 minutes. It would take 4 hours at 15.5v. It might not even reach baseline at 15.5v no matter how long it is applied.

But 16 volts is too high for most 12 volt electronics, so an EQ should be performed with vehicle cables removed from batteries.

Do Beware of any claims and features by charger/converter companies. Their marketing departments have a bunch of clowns in it that have no idea what a battery actually requires to reach full charge. Automatic chargers primary function is to NOT OVercharge a battery. They all use different algorithms to achieve this planned undercharge, and will make such and such a claim and try to impress possible consumers by adding another "Stage". Well a 4 stage charger has to be better than a 3 stage charger right? ha. Some chargers out there have battled their way up to 8 stage charging. Perhaps we should get together and market a 10 stage charger and make millions.

Most automatic battery chargers stop charging well before the battery is indeed fully charged. That blinking or solid green light seems to release enough serotonin in the brain of the user that they are convinced their purchase was justified and their confidence in the product is justified. Dipping a hydrometer into the flooded battery whose charger is flashing that green light would be a slap across the face of such a person.

The charger most capable of maxing out the SG on any flooded battery is a single stage manual battery charger, but it is not automatic. There are no blinking green lights. The user has to monitor the battery voltage and the Specific gravity, and battery temperature and know when to turn off the manual charger.

Eq cycles should be performed when the SG of the cells varies by more than 0.015., and only after the regular charging source has given up and thrown on the magical serotonin releasing yet lying SOB flashing green light. Enough amperage should be applied to quickly raise the voltage to 16v. The formula for this is 5% of the amp hour capacity measured at the 20 hour rate. So 5 amps for a 100 amp hour battery. 16 volts should be applied until the SG stops rising or battery temperature starts rising. More than 120 F is the rule, but in general this is reaching uncomfortable zone, but the higher the temp the better the chance the EQ cycle will revert hardened sulfate back into the electrolyte and restore lost capacity.

When I do an EQ cycle, I start it after my Solar has taken the battery upto 14.8 volts and the current required to hold it at 14.8v has dropped to 0.8 amps. My controller then goes to 15.1 volts and usually 1.2 to 1.8 amps is required to hold this voltage. I then pop the cap, dip the hydrometer and will see anywhere from 1.220 to 1.270. I then move all my loads to my other battery, readjust my Acceptance and float voltages upto 16 volts and it will take 6.2 amps to raise and hold the battery at 16v, which is right around 5% of the 130 amp hour capacity.

SG will take anywhere from 30 minutes to 4 hours to climb back upto 1.285 on all cells. by the enmd of the EQ cycle, when SG has stopped rising, the amps required to hold 16v have tapered to the 3.2 range. After an EQ cycle, that night, the battery performs admirably, in terms of voltage held for the loads placed on it.

This is a strange battery and most Flooded batteries should not require a weekly EQ cycle but figuring out what the battery requires to reach maximum energy density has little to do with the blinking green light, or claims by the charger manufacturer and the only tool out there which can let you know this is a Hydrometer. Watching a voltmeter closely and noticing that the battery seems to lose voltage more quickly than before can be a sign, but the only way to Know is with a Hydrometer.

Now this may seem like a lot of effort to go to. It is, but relying on a plug and play charger to properly tend to any specific batteries is like drinking the Kool aid.

It might not be worth the extra lifespan that providing a more aggressive properly monitored recharge regimen can provide.

After all, batteries are only rented.

Armed with this knowledge, you can decide how far you care to go to max out battery lifespan and performance during that lifespan. But whatever you do, do not fall into the blinking green light stupor that so many do. Blinking green lights mean little. It is more indicative that the technically clueless lawyers and the bean counters and marketing department have overruled the engineers once again.
 

mconlonx

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There's a local solar group in my area who are offering these to members at a discount. They seemed to have multiples, but said they'd go fast. Not even sure if I will end up with one -- ex-wife who is a member alerted me to the deal, but I do not have confirmation that I will end up with one yet.

Thanks, all, for the studied responses. I need to do a lot more reading up on the subject, but am now headed in the right direction.

Sternwake, plan was to get a battery or two hooked up off the alternator, like you suggested in another thread. So that would still be part of the overall plan, just that now, if I get this panel, I will go with some solar as well. Also thinking I might build one of those 12v generators. We'll see. So for the time being, 250w-ish panel on the roof, auxiliary charging off the alternator.
 

SternWake

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I think if you take advantage of all the alternator can offer, and with a 250 watt solar panel, with the loads you have listed, you probably don't need a 12v generator too.

But I think building a 12v generator is a neat idea too. With a big alternator it has to be an awesome bulk charger.

I'm all for blasting batteries with high amperages when they are depleted, and cycled daily. Sure high recharge rates are abusive to a battery, but not more abusive than letting the battery begin another discharge cycle when far from fully charged, day after day.

My alternator is my amp blaster, but a dedicated 12v generator would be superior by far.

Limit the voltage to the mid 14's and let the batteries decide how much amps they can take as they climb upto ~14.5 and then hold that voltage until they decide that ~ 4 amps or less is needed to hold 14.5, and then you are right in the 90% charged range. Adjustable voltage regulators exist to control the alternator so one could dial it in for the 14.8v required for trojan t-105s or the 15.1v required by my flooded group 31 US battery.

Use Hydrometer to verify on flooded batteries.

My batteries always responded favorable to 50+ amps for 10 minutes in the morning. Much more so than not running the engine and the solar "completing" the charge throughout the day.
 

mconlonx

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Scored the panel! Sweet! Probably lots more questions to come, but in the meantime, some studying up to do. This is the local group to which my ex belongs: http://searei.org/
 
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