Noob Questions About Failing SLA Batteries

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pseudo_mccoy

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I have two, 35ah SLA batteries. They're only a month old and seem to be loosing steam.

They are charged by 120w solar panels. The panels came with a 10 amp charge controller. I think the rule is to have 1 amp of panel for every amp hour of battery. But is it ok to have less battery than panel? I know 70ah is low, but I don't use a lot of electricity.

I frequently check the batteries with a multimeter. The batteries rarely go below 12v and I've never let them drop below 11v. Optimistic Paranoid was kind enough to point out that a battery reading of 11.8 is considered totally dead.

However, the Sealed Lead-Acid 12-Volt Battery Buying Guide on ebay says, “Deep cycling happens when the battery is discharged to below its fully discharged voltage. For 12-volt batteries, this means that the battery’s loaded voltage drops below 10.20 volts.” So, dead is somewhere between 10.2 and 11.8, right?

Optimistic Paranoid went on to explain I should not let the batteries go below roughly 12.2v. Unfortunately, I've let this happen several times. Here's why...

The best information I could find specific to the batteries was on cycle use:

100% depth discharge 200 times
80% depth discharge 225 times
50% depth discharge 500 times

But I don't understand at what voltage the battery is at a given percentage. Before I used the batteries, I contacted Chrome Battery for details. All they said was the batteries would be fine if I usually kept them above 10v. Was the representative mistaken?

I know each battery's discharge limits vary by manufacturer. How can I find at what voltage a battery is at a given percentage? Is this called a charge curve? Or maybe a voltage state of charge? Should I expect a manufacturer to have this information available? Chrome Battery certainly didn't.

TL;DR I probably just wrecked my batteries out of ignorance. Where can I get voltage/percentage details?


Sorry, I posted this in the wrong forum. I meant for it to go in Electrical: Batteries, Generators, Solar. Do I have to wait for a mod to move it?
 

MrNoodly

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You should avoid going below 50%. However what 50% is changes with ambient temperature. For example, a chart I got somewhere says:

12.26V @ 90°
12.16V @ 80°
12.06V @ 70°
11.96V @ 60°
 

SternWake

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Voltage, when under load, is a horrible indicator of state of charge.

You can take that fully charged 35 amp hour battery, put a 10 amp load on it, and within a minute it will be reading voltages somewhere in the 11's give or take.

Generally SLA batteries are AGM batteries, and AGM batteries are known to hold higher voltages than flooded batteries for the same amount of discharge.

The rule is generally one watt of solar per one amp hour of storage, but my opinion is leaning toward this as being too low.

I am also of the opinion that these cheap SLA batteries are likely the inexpensive Asian AGM batteries, and we all know the quality control measures Asia takes when shipping products overseas to us barbarians.

Try giving the batteries a break one night and let the solar go off on them for 2 days.

Unfortunately with sealed batteries there are few effective ways to know how the battery is actually doing in one's use.

If using voltage, then one needs to remove all charging or discharging sources for at least an hour( the longer the better) and see what the voltage rebounds to.

The voltage/ State of charge charts commonly posted are just general guides. Each individual battery will be different to some degree or another and 50% will also change as the battery ages.

If you really want to know state of charge, you need to be able to count amps into and out of the batteries.

This product can do one or the other but not both at the same time.
http://www.amazon.com/High-Precision-Power-Meter-Analyzer/dp/B00C596UIA.

It only counts 64 amp hours before flipping back to zero, and will only count amps in one direction. There is a source side as well as a load side.

I have one of these and it is not accurate with loads below 0.8 amps though. At agrees closely with my shunted and clamp on ammeters above 0.8 amps though, and I find it to be extremely useful, even with its limitations.

https://vanlivingforum.com/showthread.php?tid=5120
 

akrvbob

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I'm afraid you learned he hard way that most sales people in the 12 volt world know nothing and most of what they know is wrong. Here it is in a nutshell:

1) It's hard to get an accurate reading of the true voltage of your battery. If it's being charged or used at all, the reading is wrong.
2) The only simple way to get a basically accurate reading is to let it sit unused overnight and check it in the morning. That's pretty close to a true reading of it's charge.
3) You want to try hard to never take it below 12.2 volts.

There are lots of addendums to be made to every one of those things, but for your purpose they are all you need to know for now.

Unless you are having lots of rain or clouds 120 watts should be enough for your very light usage. My guess is it's a a cheap battery that just isn't up to the job at hand. Does it have a warranty? Can you exchange it under warranty?
Bob
 

pseudo_mccoy

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Thanks for the charts slow2day and MrNoodly. I'll be sure to write them down.

SternWake, you rock. I'm not the brightest crayon in the shed so it may take me a while to parse your input. In the meantime, I'll give the batteries a rest as you suggested.


Thank you for breaking it down, Bob. I seem to remember reading somewhere that it's best for a newbie to buy cheap batteries because there's a good chance they'll just end up wrecked anyway. Now I know.

They are under warranty. I intend to find out if they'll honor it.

Interestingly, the Chrome Battery had great reviews on amazon so I ordered them. However, when I opened the boxes, I saw a couple Pirate Batteries an apologetic letter explaining that there was no difference between the brands. Maybe, in addition to running them too low, I also fell for a bait and switch.
 

MrNoodly

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SternWake said:
The rule is generally one watt of solar per one amp hour of storage, but my opinion is leaning toward this as being too low.

I wonder why you're inclined to think that. Not that you're wrong. I'm just curious about your reasons.

My system, with ACM batteries, has slightly more wattage than amp hours, and on a sunny day the charge controller will switch from absorption (14.4V) to float (13.7V) sometime during mid-morning. On overcast days it might take until lunch. And that's with the fridge running and electronics being charged. It will remain on float until sundown. Then the voltage will settle in at 12.9V and run down to about 12.75V overnight. Sometimes 12.8V. May whether 1W-to-1Ah is enough depends on how much power you use daily.
 

SternWake

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I have one AGM whose fully charged resting voltage is 13.07 volts. My other battery fully charged and rested is 12.68v.

A rested 12.40v reading on this AGM battery is under 50% State of charge, and a rested 12.40v reading on the other is well over 50% State of charge.

There is NO voltage absolutes that applies to all batteries, and voltage readings on anything but a well rested battery is inaccurate in the extreme.

A voltmeter measuring voltage on the battery terminals themselves is ONLY accurate on a battery which has not seen charging currents or discharging LOADS for hours and hours. It will not be the exact same battery to battery, and it will not even be the same on the same battery after it has aged for a year, if it even lasts that long!

If you see 11.8 volts while there is still a load on the battery, it might very well rebound to well above 12.4 once the loads are removed and the battery allowed to rest for at least an hour, and 11 hours later it might rebound another few tenths.

The faster the voltage rebounds when the loads are removed, in general, the healthier the battery is. There is no rule to how fast any specific battery will rebound, nor how much it will drop under any specific load, nor how much this will change as the battery ages. Just a trend, downward.

Voltage is a piss poor method of determining state of charge. Often voltage is the only tool one has to have any idea of the state of charge of their batteries, but far too often and spouted as gospel far too often, is the 12.2v is 50% and never let the battery go below this, without any mention that this is ~50% ~12.2v figure is accurate ONLY on a rested battery, one that has not seen charging or discharging currents for a period of time, and the longer period of time, the better.

But those who are loading their battery and stop at 12.2v are treating their battery better, just not using all the capacity they could and perhaps seriously inconveniencing themselves by thinking they need to stop at this point, especially if the loads are fairly large, like while running a laptop and watching tv and while their fridge compressor is running.

The higher the load, the lower the voltage will drop under load.
The higher the battery capacity, the less the voltage will drop under load.

The more a battery is fashioned toward the starting battery end of the spectrum, the less the voltage will drop under load.
The more a battery is designed as a deep cycle battery, the more the voltage will drop under load.
AGM batteries will tend to always hold more voltage under load than their similarly sized flooded counterparts.

A carbon pile load tester is calibrated for a starting battery. The expectations on a deep cycle battery must be lowered as they are not designed to support extremely large loads ( 1/2 the CCA rating) as are starting batteries.

My Flooded group 31 battery rated at 130 amp hours and 630 CCA when fully charged will drop to 8.x volts cranking my engine
My AGM battery rated at 91 amp hours and 930 CCA drops to ~10,x volts under the same engine cranking scenario. You can't compare the two batteries as they are constructed completely differently. One would look horrible under the carbon pile load tester one would read outstanding and neither reading would mean very much.

You really cannot accurately compare an AGM battery to the performance of a Flooded battery by voltage or a carbon pile load tester without fairly extensive experience with each particular battery, and a basis for comparison.

-------



Mr Noodly, I am leaning toward higher solar wattage to capacity ratios to better meet the battery manufacturer's minimum recommended bulk currents. Sizing a solar panel to Only Replace the amp hours used + 10% might be fine and dandy on many systems, especially those not cycled each and every day, but most manufacturers will have recommendations to meet a certain minimum initial bulk current. Since Solar current ramps up slowly, until solar noon, it cannot meet these minimum bulk charge rates instantly anyway, but the faster it ramps up, with more solar wattage, then the closer it comes to these manufacturer recommendations, which cannot just be dismissed.

Any charging current is better than no charging current, but the correct sized charging current for the particular discharged battery is much better than just any amount of current the battery discharger happens to have available to feed the battery. This is why when somebody with a van asks how much solar I need I will recommend as much as they can fit on their roof. Perhaps some can get away with less if they drive a lot or plug in often, or go someplace where they can fire up their generator for as long as their heart desires, or if they simply have little need for anything that uses battery power.

The lesser discharged ( 80 to 100% State of Charge) battery is not as susceptible to not having this minimum bulk rate met. The deeper one cycles the batteries(20 to 70% SOC) the more important it is to be able to meet the minimum bulk current the manufacturer specifies. If one sizes their bank large enough and never draws it below 80%, or not much below 80%, the batteries would never accept the minimum recommended bulk current anway, or if it/they did, not for very long before the voltage rose to 14.4x or near, and the controller started limiting current so as to not allow voltage to exceed this Voltage setpoint.

But if one sizes their battery bank so that it is discharged to the 40% to 60% range nightly and their Solar does not meet the minimum bulk currents then the battery is NOT getting charged as it should, as the manufacturer recommends. There might not be enough hours in the day to do so, especially in winter. Even if the solar controller does manage to flash the green light by sundown, it is very likely a hydrometer reading will reveal the Specific Gravity is NOT where it would be if indeed the battery were fully charged. The closer one comes to meeting the minimum bulk current, the more likely the SG, the energy density of the battery is approaching maximum. When cycling each and every night, ones goal should be to get the battery to as near as possible to maximum energy density, and often the flashing green light has little correlation with this desired daily goal. Most people will never know this, and might still make claims the batteries are such and such an age, and perform just like new, but such a statement is only indicative of their ignorance. The batteries might still meet their needs would be accurate, to say they perform just as new is folly. Too many people put too much faith in their charging source. Human nature I guess.

Trust if you must, but Verify before making any claims. You can't verify? Then make no definitive claims.

There is No way to measure SG with AGM. Often AGM batteries will just stop accepting current at such and such a voltage and this is the indicator that they are at or very near at 100% This figure varies AGM battery to AGM battery and with age of the AGM battery in question. Flooded batteries will still accept current after they SG is maxed out. How do you measure current if your solar does not have a display you ask? You can easily clamp this product, or a similar one over one just wire near your battery.
http://www.sears.com/craftsman-digital-clamp-on-ammeter/p-03482369000P


I urge everybody with Flooded batteries and Solar to make sure their charging sources that flash the green light, indicating a full charge, to verify it with a Glass turkey baster style Hydrometer that has temperature compensation.
IMG_1613copy_zpsae3d76a3.jpg


http://www.amazon.com/OTC-4619-Professional-Battery-Hydrometer/dp/B0050SFVHO

One makes sure, first, that there is no bubbles sticking to the glass float, then reads the float level then adds or subtracts .0XX to the float reading. The thermometer on the base of the hydrometer which will respond to the temperature of the electrolyte within, will say how much to add( higher temps) or subtract( lower temps).

In the picture above, the reading is just over 1.280, and not visible below, the thermometer at the base of the Hydrometer was saying to add 4, as the electrolyte was hotter than 77f by a few degrees. So 1.285, which as high as I can ever get this battery. If I were to raise the electrical pressure to 20 volts, the amps required to raise and hold the battery at 20 volts would likely be about 10 amps, the electrolyte would bubble like a freshly opened seltzer bottle, but the SG would never rise any further, and this would be extremely abusive to the battery as well.

Only when the SG can go no higher can the battery be considered truly, 100% fully charged. SG and the blinking green light rarely agree. Luckily 97% is good enough and a true 100% required much less often. Most automatic chargers will flash their green light in the 92 to 95% range. Same with the solar controller. Some better, some worse, and this will always vary, and more so with varying temperatures and strength and length of recharge cycles, and of course the depth of the discharge cycle.




Lots of little things to be aware of when taking a Hydrometer reading, but number one is protect your eyes!

Number two is the plastic hydrometers are not very accurate nor precise( repeatability test to test) The Glass float is fragile but worth the hassle of protecting it.

The person who believes that the blinking and soothing green light has fully charged the battery, will likely be surprised to find that when they expect to see 1.270 or higher, they are only seeing 1.250 or less. The voltage of the 1.250 battery can still read 12.6v to 12.8v when rested well after the light blinks green, as Voltage is a Piss Poor method of determining actual state of charge. And can be, even on a rested battery!

Use a Hydrometer, or remain ignorant! The Blinking green light lies, often!

My previous set of batteries wanted 18% of their capacity fed to them when discharged deeply to~ 50%. My solar was not able to meet even 5% or this rate, and they did not live as long as they I expected, nowhere near.
When these first 3 pairs (2007 to 2013) of expensive true 12v deep cycle batteries could no longer meet my overnight needs, I replaced them, and deliberately lowered my overall battery capacity, and my current battery manufacturer recommends a 10% initial bulk rate ( 13 amps for 130 amp hours of capacity). I can just barely meet that rate at high noon in summer, not counting the load I use while charging, and the battery is holding its capacity much better. I am discharging it further each night, percentage wise, than I did the larger capacity bank, but it is being recharged at a higher rate, and is responding well so far, and I am carrying 62 less pounds around, and when this battery fails, it was ~ half the purchase price and will be ~ half the cost to replace.
And I have never needed all that extra capacity I used to carry before! Not once.

If you never are going below 12.75v, then you are certainly not using much of your battery capacity . Those using 50% of their capacity regularly will be much better off with a much higher solar wattage to capacity ratio. Especially if they are using a lot of power during daylight hours, driving little, and run into bad weather for a few days.

I think too many people want a lot of capacity to get them through bad weather, but more solar and a little conservation during bad weather might very well make the batteries happier by bringing the lesser capacity bank to a higher state of charge daily. Lesser amounts of solar, allowing the larger battery bank to discharge lower and lower slowly over those several days of bad weather, and not being able to meet the minimum bulk charge requirements/ recommendations of the battery manufacturer when the sun does return, could very well be more detrimental to the capacity of the higher capacity battery bank over that same timespan.

The less time spent below 80% the better. The longer a battery spends below 80% and the lower it goes below 80%, the more the battery will protest and lose capacity and require a higher percentage of energy returned into it to reach maximum energy density again, however compromised it might or might not be at that point in the battery's life.



It is not as if no charging happens in cloudy weather, one can still see perhaps 30 to 50% of what they see in full sun, depending on a lot of factors.

If one never takes a house deep cycle battery below 80%, then, basically, that full time Van dweller has too much battery capacity, and even a small ratio of Solar Wattage to battery capacity can keep the battery healthy for a while, and the dweller gets the warm and fuzzies by having that " emergency capacity" available. I did it for years. Mostly, it was bragging rights and nothing more. I never used all the capacity I had. Never came close.

Since 2007 I've spent close to 750$ on batteries( not including my current pair), and perhaps if I had bought half as much capacity in '07, I would have gotten better life from the battery, and ultimately would have spent a third of that!

It is really very dweller dependent. The 1 watt to 1 amp hour is a general recommendation. There are so many variables to each person's usage and climate one can not pin down an exact figure.

I have found, in my usage, and in my environment, coastal Sunny San Diego, that 1 to 1 ratio is too little. I do not drive much at all, I rarely plug in, I cycle my batteries to below 70% each and every night, and my 130 amp hour battery is responding much much better to 198 watts of solar, than my previous banks of 230 amp hours did to that same solar wattage. I spent 60% as much for the lesser capacity battery bank, I carry around 60 less LBs of battery, and when it fails, I am out 40% less money on replacement. I might even get the same overall timespan from this single battery as it is being charged in a manner closer to what the manufacturer recommends, so return on investment, might very well be double or even triple what it was before, and perhaps even more.

Time will tell.

The thing can fail tomorrow, but right now it is 12.24 volts under a 7.8 amp load with only 28 amp hours removed from it, and that is right where I expect it to be under this amp load and that level of depletion. By morning, it might have hit 11.8 volts when the fridge compressor was running under a 3 to 4 amp load, including my fans and other things I might not have bothered to turn off. Somewhere around noon tomorrow it will be in the high 14's and at some point it will have came very close to seeing that 10% rate my battery manufacturer recommended for best lifespan and longevity and performance during that lifespan. I bet the battery would love to see that 14.9v well before noon. When i do drive somewhere in the morning and my alternator exceeds the minumum recommended bulk current by a large margin, the voltage held that night during the same usage is noticeably higher during the same amount of discharge, proving to me anyway that this meeting or exceeding this minimum recommended rate is not just Mumbo jumoistic ravings of a twisted van dweller.

Perhaps when this battery does fail, I will lower my capacity even more, as I can fit no more solar.

I have the ability to turn off all loads on either battery. I have done so right before sunrise when battery voltage read 11.7v under a 3.2 amp load. Do you want to guess what that battery voltage read 6 hours later, with no loads and no charging sources on it?

If you guessed under 12.42, you were wrong. It would probably have jumped another 0.06v in another 6 hours.

So in conclusion:
1. Voltage can be overwhelmingly misleading as to battery state of charge. It can be completely worthless, especially when one is not aware of fluctuations caused by loads and rebound time.

2. Battery manufacturers usually have a published recommended charging regimen, the closer one can come to this regimen, the better the battery will perform, and the longer it will perform for. Do not disregard the manufacturer recharge recommendations. Solar is usually not considered in this manufacturer recommendation. If a minimum bulk charge rate is specified, Size the solar wattage to at least approach this minimum bulk charge rate. If one comes nowhere near close to it, then one cannot view their solar as a proper recharging source, and needs to have a method which CAN meet the manufacturer recommendations, at least every 10 to 14 cycles.

3. Perhaps capacity is not king. If you cannot meet the manufacturer minimum bulk rate for the capacity you want with the solar you have, then lower your overall capacity to come closer to it, or resign yourself to finding and using a charging source which will provide the current needed over the timespan required to reach maximum energy density and a Specific gravity of at least 1.270.

4. Van dwellers mostly cycle their batteries each and every night, and likely use the batteries while they are being charged by solar too. This use must be accounted for when trying to meet manufacturer recommended minimum bulk rates. Many recommendations as to wattage/capacity ratio do not account for the DAILY cycling, nor loads placed on the system during recharge. Many other RV sites will make recommendations on this ratio knowing that at some point the RV'er goes home, and plugs in and the converter or the solar has all the time needed to return the batteries back up to maximum energy density, as the Rver moves back into the stick and brick and asks for no more from the batteries.


5. Do not trust the green blinking light. There are several tools available if you wish to verify, which you should, every so often, if you care. The Hydrometer, will reveal the most. The Clamp on Ammeter, or other ammeter showing the battery cannot accept much current at 14.x volts is good, as long as the current source is capable of delivering in excess of this amount. Battery monitors can be very enlightening as they will count amps into and out of the battery, but they can only be considered ~ 90% accurate when calibrated properly, and not as gospel. If you can reset the battery monitor when the hydrometer agrees that the battery is fully charged, then you can be much more confident in it, but verify it in two weeks of cycling with the hydrometer, especially if you are under the 1 watt per 1 amp hour of storage.

6. Everything is a compromise. They are just batteries. They are only rented anyway. It is only Money, and the choice is yours, as to how much effort and time you wish to expend to get everything you can from your rental contract. I'd prefer not to throw money at this rental contract.

I am also interested in this stuff and much of what I write and share here is what I've learned slowly, through mistakes, and reading other sources, and observations through many different tools, and experiments, and is designed to help all of you not have to learn the hard way and spend more money on this contract than you need to, just to have enough power to live semi comfortably in your rolling freedom machines.

I get a little overanxious to correct mistakes I've seen other people relate, and I apologize if I come off as arrogant or disrespectful. That is not my intention nor how I am in person.
 

Seeker

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SternWake, Bob and everyone else very good info. I am not asking for specifics but could you give me a general idea of what wattage solar panel and battery combination will get me in ballpark range. I will be running an ARB fridge like this 50 quart http://www.amazon.com/ARB-10800472-...TF8&qid=1405174180&sr=8-1&keywords=arb+fridge ceiling vent fan Fantastic or Maxxair roof vent and some LED lighting. I do have a Honda 2000 generator that could help charge the battery on occasion. Its Chevy Express standard length cargo so not a lot of room for panels.
General recommendation Please ?
Thanks
A SEEKER
 

Zil

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Being that small I would guess they are jell type batteries. Not that it matters. If you let them run "dead" and then tried to recover they will not keep up.
The quick test is to use a good charger to fully charge the battery, let rest, then get a load test to see if the batteries are worth using.
Just fully charging them may be enough to get a little more service out of them. But you can't ever get 70 amp hours from two 35 amp hour batteries. More like maybe 30 working amp hours. That is 15 amps for 2 hours, or 3 amps for 10 hours. Any more that that is battery abuse.
 

SternWake

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The website for "Chrome" batteries likes to use the SLA terminology a lot, but the finer print says they are AGM, which of course many people love to refer to as a gel cell, and Gel batteries do exist, and their construction and charging requirements are different from AGM or Flooded batteries. Gel batteries and AGM are not one and the same, though many will refer to an AGM battery as a Gell Cell.

There are some sealed flooded batteries which are SLA batteries, but in general most SLA batteries are AGM. but a true Gel battery will also fall into the Sealed Lead Acid category too.

I really believe these chrome batteries to be the Asian Universal Battery with a Fancy Sticker on them.

http://www.amazon.com/UPG-D5722-Sealed-Battery-UB12350/dp/B001VV0318

If one looks at the spec sheets for these, they do not enjoy the low self discharge figures of other higher quality AGM batteries. They are not much better than flooded batteries in this regard.

Their CCA figures are not nearly as impressive as other high quality AGM batteries.

And another oft touted performance benefit of AGM batteries is their ability to accept very large initial bulk currents, where as these Universal AGm batteries usually place a limit on initial charging current where as most flooded batteries place no limit on initial current as the battery will limit what it can accept. Too much initial current on an AGM that lists a maximum current, can pop the vents and compromise the battery to some degree.

Combine the not impressive self discharge figures, Asian quality control, and the fact that they come here on a slow boat from China then wait on some shelf to be bought, the battery could very well already be significantly sulfated before it is even put into use.

Sulfated = capacity compromised. Very unlikely that the most high tech wiz charger out there can revert any of that hardened sulfate back into the electrolyte and restore any significant capacity.

These Asian AGM batteries might win the price wars, but I believe them to be bad deals overall, and the OP's case tends to solidify my thoughts on this matter.

With Batteries, always buy the freshest you can find. If you can find manufacturer documentation about their recommended recharge parameters, you should hope they can meet your charging source's output.

I've seen many a deal on AGM batteries online, and even with free shipping I think they are a bad deal, as one has no idea how old the battery is, how long it has been shelved, and how much capacity it has lost just sitting on that shelf waiting to be bought.

Being initially frugal, often is akin to shooting oneself in the foot, especially with batteries.
 

Zil

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second for stern wake. especially the last couple of inches in the previous post.
 

akrvbob

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Your needs are pretty basic so I would recommend the exact system I have. I bought it from Northern Arizona Wind and sun in Flagstaff AZ and these are the actual prices I paid last summer. I haven't looked recently, but I bet they are about the same now:

1 Trina 240 watt panel -- $240
1 Blue Sky High Voltage mppt controller -- $200
1 Meter for controller $90
2 Crown flooded 6 volt golf cart batteries $240 total
Miscellaneous cables, fuses etc -- $$75

And that's it! 240 watts of power should do everything you need even in the winter.
Bob
 

akrvbob

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Here is what I recommend:

1 solar panel around 250 watts.
1 MPPT controller able to handle the voltage of the panel.
2 6 volt golf course batteries.

That's basically what I have and it cost me about $900 total from Northern AZ Wind and Sun.
Bob
 

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