Another noob question

Just Me · September 2009

Hi all, new guy here. Great site. Been lurking for a while and have some questions about two Siemens M75 48W panels that were given to me. I uses them on my 5th wheel toy hauler about 12 - 4 day weekends between Oct and May, at the Imperial Sand Dunes west of Yuma, AZ.

I pop riveted them together and wired them in parallel. Aimed directly at the sun, I get over 6 amps short ckt and over 19 volts open ckt at the junction box and at the end of a 10’ 12/2 cable that plugs into a panel on my 5th wheel trailer. The panel is wired with about 18” of 12/2 to the + cable on my genny that goes directly to two T-105 Trojan batteries wired in series.

latitude

When I'm camping, I try to keep the panels pointed as directly towards the sun as possible. (Latitude N32° 42’+15°) The panels sit on the ground and have a pivoting arm to adjust the angle. I have been told that I should be using a CC, but I don't know which kind. I do not plan on expanding my array and don't want to put too much money into solar. Just want to get the most out of what I have.

The fridge, water heater control modules and the air sensors are on all the time, drawing about .5A. I use a 300W inverter to run my LCD TV, and laptop. The propane heater draws a lot at night also. I don't know what my amp/watt hours are, but the solar panels used to bring my test panel up to full on a sunny day. Lately, they rarely charge the batteries fully during the day. The Trojans are 4 years old and are bulging on the sides. Me thinks sulfated and my smart charger doesn't seem to rectify that.

I just fired up my trailer and these are my ~amp draws with different appliances on:
1:00 PM, 19V and 6.06A with a clear sky and cold panels.

CO2 + Propane = .18A
+ Fridge ===== .51A
+ 1 Lite ===== 1.46A
+ Inv/w TV === 6.06A
+ Heater ====11.00A

I guess it would be hard to figure my amp-hours with the heater coming on and off during the night.

When camping, I have been leaving my trailer plugged into my truck with two 12V batteries and it does draw down the truck batteries, but there have been times when the solar panels did bring it up to full charge as shown by the lights on my battery test panel. Would it be better to disconnect the cable to the truck?

I’m in the process of installing a Trimetric 2020, but a back injury has slowed that down. I’ll know more when I get it installed. Should be interesting.

So, aside from this meter, would I also need a charge controller. Are the $30 ones good enough for my 96W solar panels?

Will my panels keep up if I charge the batteries with the genny in the morning? I should be pulling < 5A with just the TV and inverter on. During the day, I am away from the trailer for an hour or two at a time, so it gets the full charge minus the fridge, CO2 and propane sensors.

Anybody out there have a used MTTP CC for sale? I only need one that can handle 6 amps.

I'll probably get some Sam's Clubs cart batteries for $73 each when the dune season starts. I'd get some hydro readings, but they are in a 13x15x12 enclosure and I would have to disconnect them and remove them. My back would not like that at all.

Thanks for any input,

Mike

Cariboocoot · September 2009

Re: Another noob question

First off, check your Trojans with a hydrometer. If they've failed there's nothing that will charge them up again.

Second, yes you do need a charge controller. You've been playing Russian Roulette with letting the panels feed whatever they can produce into the system. At a glance your loads would appear to exceed the charge capacity (without generator) - especially that heater. Never heat with electric if you can avoid it.

You don't need an MPPT charge controller for 12V panels feeding a 12V system. Their main advantage is in 'downconverting" higher voltage panels to the best available charge current at system voltage.

Frankly, you're way short of panels to keep 225 Amp/hrs of battery 'happy', regardless of loads. You'd need at least 135W under ideal conditions for that. If you've been relying on the panels and not the generator, chances are the batteries have become hopelessly sulphated. As that happens, their capacity goes down, down, down - so even though the Voltage reads "charged" there simply isn't any power there anymore. Like the difference between a penlight cell and a 'D' battery: both are 1.5 Volts, but with considerably different power potential.

You should be able to plug a Kill-A-Watt meter in between your inverter and its loads. This will give you a good idea of actual usage over time. Then you need to decide whether to replace the batteries with smaller ones that the 96W panels can handle (less than 160 Amp/hrs) or upgrade panels and batteries so you're not so generator dependant.

mike95490 · September 2009

Re: Another noob question

Cariboocoot wrote: »

Second, yes you do need a charge controller. You've been playing Russian Roulette with letting the panels feed whatever they can produce into the system.

Generally, I'd say No, not needed. 6A into 2 monster batteries, is barely going to equalize them, and might get them bubbling lightly. You have a lot of loads, and little recharge. But you HAVE to monitor the fluid level in the batteries, and if you have a bad back....
What happens when parked, and not camping - Is PV connected and charging, or what ? You should charge 1x a month, or if PV is on all the time, you will need a charge controller

After you replace the batteries, you WILL need to monitor the levels, or they will eventually boil down, and die prematurely.

I would also swap out the incandescent lamps, and use some LED lights, that will save you some too.

While parked, disconnect from your starting battery,
a) you don't want to drain that flat
b) it's not a deep cycle, and will not last long with deep cycling.

Cariboocoot · September 2009

Re: Another noob question

You can kill a battery by over charging or under charging; it's just as dead either way. And he doesn't have any reliable way of telling what state it's in. I wouldn't trust bunch of indicator lights.

Just Me · September 2009

Re: Another noob question

Thanks for the replies. The heater is propane, but the blower pulls a lot of amps.

At home, I only have a BatteryMinder hooked up to the batteries and when it fully charges them, it goes into the pulse mode to de-sulfate the cells. I check the fluid level about once a month, especially in the AZ summer heat. I have never found the level below the plates.

Gonna check NAPA for a good hydrometer. All the other ones I have had broke the glass tube if looked at wrong. What number LED lights should I look for?

mike95490 · September 2009

Re: Another noob question

12v automotive LED's http://www.ledtronics.com/index.htm & http://superbrightleds.com/1157.htm are good places to start shopping at

Just Me · September 2009

Re: Another noob question

Thanks, will check them out.

icarus · September 2009

Re: Another noob question

Consider a proper battery monitor, like the Bogart Tri-metric. It can give a running total of ah in, ah out, cumulative ah, real time volts/amps and percent full based on your own parameters. Pretty cheap insurance. Cheaper than one set of T-105s

Tony

Just Me · September 2009

Re: Another noob question

I am in the process of installing it now. I just spelled it wrong.

Just Me · September 2009

Re: Another noob question

Finished installing my Bogart Tri-metric 2020 and it shows the same reading I got with my hand held volt/amp meter as I posted above.

I'm not trying to substitute total solar for what my genny puts out. I just want these panels to charge my batteries during the day when I am only drawing about .50 amps. With the panels putting out ~6 amps during the day, I am hoping the batteries would be charged enough to keep me from running the genny during the evening or night. I would then run the genny in the morning to replace what the propane heater blower drew down.

The reading posted above are cumulative. It's not like the amps increased 6+11, but from 6 to 11. so the blower motor only added 5 amps.

Forgive me, I am a retired old man, trying to make what I have work to the best of my ability.

Just Me · September 2009

Re: Another noob question

Today, at noon, I plugged in my panels and my Bogart Tri-metric 2020 showed 4 amps in and 13.7 volts. The amps slowly went down and the volts went up to 14.4. I didn't want my portable panels to grow legs sitting out near the street, so I didn't watch it for too long.

I read that article about Trojans' needing 14.8V to charge properly. When I get a chance, I'll leave the PV array connected longer to see how high the volts go without a CC.

I really like the Bogart Tri-metric 2020 I bought from those people at the top of the page. They have great customer service and prompt shipping.

mike95490 · September 2009

Re: Another noob question

Just Me wrote: »

I didn't want my portable panels to grow legs sitting out near the street,

That's the problem with portable panels !

Just Me · September 2009

Re: Another noob question

Since I bought the Tri-Metric 2020, I will be attaching a lock and chain to them so when I'm at the dunes they don't wander off.

Just Me · September 2009

Re: Another noob question

I saw that deleted reply from R.J. about:
"Do your homework and you'll be amazed at what you find."

I have done that, but don't have the mega bucks like some of you have to facilitate a total solar setup. Like I said before, I use my 5th wheel trailer(toy hauler) at the dunes 10-12 times a year for 3-4 days at a time.

I did a lot of homework and found a lot that amazed me about solar energy. As shown in this thread, some think I need a CC and another says I don't. Who do I believe? Do I go by post count?

I posted: "I'm in the process of installing a Trimetric 2020" yet someone later posted: "Consider a proper battery monitor, like the Bogart Tri-metric." Hello, can you comprehend English?

I appreciate your knowledge and experience, but give a new guy to solar a break and don't come down on me like I am a complete idiot. I am a retired electronic technician with over 43 years experience in the electronic field, working at Motorola and AT&T.

Just Me · September 2009

Re: Another noob question

Today, when I plugged my "BatteryMinder" brand charger into the umbilical cord to my trailer, my Tri-Metric showed about .45 amp charge rate. Later, when it figured that my batteries were charged, it went into the de-sulfate pulse mode. The Tri-Metric then showed -.13, as if it was drawing from the batteries. Anybody else notice this?

BB. · September 2009

Re: Another noob question

I think the comment about getting a proper battery monitor was just a mistake--may have missed your saying you wanted to get that unit.

Regarding if you need a charge controller or not--Currently, you are in the zone where it is sort of not really needed--assuming that you keep a watch on your battery electrolyte levels... Your ~5-6 amps of charging current into 225 AmpHours (guessing) 12 volt battery bank give you:

5 amps / 225 AH capacity = 0.02 or 2% rate of charge

Generally, if you are in an off-grid application and you wanted to use solar (or other chargers)--the rule of thumb for charging current is ~5-13% of the 20 Hour battery capacity.... Less than 5%, you will have difficulties using the solar panels to bring the battery back to full charge. Over 13% and you can overheat the battery bank and/or it is possibly a waste of money because the battery will simply not absorb that much current (some batteries, like AGM's can take more current without overheating).

For your 2% rate of charge--that is getting down to the point where a flooded cell battery will be OK without using a charge controller--Once the battery bank has been charged (AC mains, genset, etc.), that level of current will not damage the battery and probably just require you to add a bit more distilled water (every month or so) to keep the plates covered.

If you want to add more panels--then you should very much look at getting a charge controller.

There was a comment above that talked about not getting a MPPT CC -- If you do not know--a MPPT Charge Controller is a "Maximum Power Point Tracking" charge controller that is basically has a switch mode buck type power supply front end. It can take high voltage/low current from the solar panels and "transform" it to low voltage/high current for the battery (at better than 90% efficiency).

An MPPT charge controller is expensive and generally not really very efficient for small arrays (under 400 watts--MorningStar has a 15 amp 12/24 volt MPPT controller that works efficiently down to 200 watts or less of solar panels--but it is not cheap).

There are PWM controllers which will work very well for your system, and can be expanded quite nicely (upwards of 30-60 amps). Depending on your needs (and eventual maximum solar panel array and some other issues)--a nice PWM controller with a remote battery temperature sensor would be a nice solution for you.

Our host is a good place to start looking at charge controllers. The Xantrex "C" series is PWM (old design but work very well). And the Xantrex XW MPPT CC is a very nice brand new MPPT design (see the other end of the price range). MorningStar PWM and the one MPPT unit are also very nice.

NAWS also sprinkles lots of FAQ's around their site (typically in the same area as each product type)... There are a couple good ones that explain charge controllers better than I can here:

All About Charge Controllers
Read this page about power tracking controllers

-Bill

icarus · September 2009

Re: Another noob question

Whoa there, take a deep breath:

I posted: "I'm in the process of installing a Trimetric 2020" yet someone later posted: "Consider a proper battery monitor, like the Bogart Tri-metric." Hello, can you comprehend English?

I appreciate your knowledge and experience, but give a new guy to solar a break and don't come down on me like I am a complete idiot. "

I confess that I did indeed miss that bit of information in your first post, but there was no malice in my reply. As for who do you rely on for good information: I don't think post count means much, but if you pose a question, eventually some very smart folks will weigh in and a consensus will emerge. Some folks have very good technical knowledge and others have very good practical knowledge, and a few have both. Almost never over the years have I seen someone malign someone for a "newbie" question.

You will over time get conflicting answers to a question, but as I suggest, a consensus will emerge usually. I think you will find that the subject is rather addicting to some and you may find yourself diving in deeper as time goes on.

As for you question about a charge controller. Personally, I would have one on almost any set up if the Vmp of a panel array is significantly above battery absorb voltage.

Tony

Ps Sorry if I offended. Your original post was long and involved ( a good thing) and I just missed the reference to the trimetric!

Cariboocoot · September 2009

Re: Another noob question

Yes, you will often get seemingly conflicting answers. That's because in engineering there usually isn't just one right answer to any problem. Often theres a dozen, and each will work. The tricky bit is choosing the solution that best fits your needs. A lot of us here speak from years of experiences - good and bad - and those influence our answers; different experiences, different answers. Furthermore, we have different areas of expertise; you'd be surprised at the number of specializations in electronics. On this forum, for instance, there are those who deal largely with grid-tie systems and those who are more familiar with off-grid.

I will confess that my answers are sometimes quite wrong, or at least not the best they could be. When I first learned about electricity was decades ago and much of the technology that exists today simply didn't back then. Really; I started with valves (vacuum tubes, Yanks!) and the transistors that first appeared were Germanium. Integrated Circuit? No such thing then. I try to keep up, but frankly my brain isn't as agile as it once was.

Just Me · September 2009

Re: Another noob question

icarus, and anybody else I offended, I sincerely apologize for my hasty response. It was fueled by frustration and a little alcohol.

I've done a lot of reading for the last 2 months before I joined this forum. I read the entire article by that guy that says Trojan batteries need 14.8V to fully charge and even joined another forum, soon to find out that there was a lot of bickering amongst members and very little response to my questions. The information I've found on NAWS is very helpful, but still confusing.

On the amp meter where I plug in my array, I have never seen over 5A, even though I see > 6A short ckt from the panels. I think that is due to the state of charge already on my Trojans. It does drop as they charge. This leads me to believe that I don't need a CC. With the Bogart, I have not seen over 14.4V, but will do more testing. The consensus is leaning towards not needing a CC.

When my battery bank was newer, the panels did bring the idiot lights up to full. I'm not dissatisfied with my PVs, I have just been wondering If I'm doing it right for what I have. I think if I get new batteries and treat them right, I will be more than satisfied with their performance.

Sorry again for being snippy and thanks for the replies.

mike95490 · September 2009

Re: Another noob question

When you get new batteries, you should consider ways to keep them charged. Your current panels don't have enough power to recharge fully. How long did this set of batteries last you ?
Chronic undercharge will eventually kill batteries.

BB. · September 2009

Re: Another noob question

If you have not had a chance yet, take a look at the battery FAQ and the vendor's website on their batteries.

Battery charging voltage is just a means to an end... Moving current efficiently into a battery (during charging) and not moving much current when the battery is charged (storage).

So, for day to day charging as long as you are over 14 volts or so--the battery is physically charging. The higher the voltage, the faster the charge rate (and somewhat less efficient as more heat is generated and more hydrogen gas is produced). So, the voltage from the battery is a combination of charging current, chemical processes, and temperature. If the battery is below 80-90% state of charge--the charging voltage is really set by the battery itself (and the charging current from the charger).

Once the battery is charged, any voltage between ~12.7 and 13.8 volts or so will keep the battery charged and not generate very much hydrogen.

There is a point where you need about 15-15.5 volts (again at standard temperature) to equalize the battery (approximately once per month or so). This helps to mix the electrolyte (gas bubbles mix the acid which can sink to the bottom of the battery with the water at the top--very useful for taller batteries) and to charge the series connected cells that may not be at full charge (some cells a bit weaker than other in the string--so you waste energy in the fully charged cells to bring up any weak cells).

The several things that usually kill batteries (besides old age/cycling) is:

Deep cycling; discharging below 50% capacity all the time, or below 20% of capacity even a few times
Deficit charging/storing below 75% state of charge; Never bringing a battery back to near full charge--if a flooded cell battery is below ~75% state of charge for more than a few hours or days--the sulfates begin to harden and will not be changed back during the next recharge cycle
Improper Watering; not keeping the plates covered by adding distilled water or adding contaminated water

If you avoid the mistakes above--your batteries will probably have a nice long life (all else being equal).

-Bill

Just Me · September 2009

Re: Another noob question

4 1/2 years old and I have never found the electrolyte below the plates. Usually, during the summer, I store them in a cooled garage hooked to a BatteryMinder® and fully charge/equalize them every month of so with my Power On Board Smart Charger. When in the trailer at home, I have the BM hooked to the trailer and also charge/equalize them with my Smart Charger. I'm sure there were rainy days at the dunes where they were drawn down more than they should be. My genset is propane powered, so I have to watch my usage.

With the BM in the conditioning pulse mode, Bogart sees 12.9V and +.04A. When I re-start it, it goes to 13V and +.51A. The way I understand the BM, is that it senses when the battery is charged, then goes into the float/maintenance/conditioning/desulfation mode.

Thanks to the link to the battery FAQ. I'll print the part about SOC and DOD and check it next trip. I disconnected the BM and will check the volts tomorrow to see how much they drop over night. Will that give me any indication of their condition?

BB. · September 2009

Re: Another noob question

The "resting voltage" is a pretty good estimate of the battery's state of charge (see battery FAQ). You can leave the battery off charger for a few weeks or a month and measure the state of charge and see how fast it is self discharging (evidence of age too).

Measuring the specific gravity of the electrolyte with a hydrometer is probably more accurate and gives more information (you can check the state of each cell).

Avoid too much equalization (too often and/or too long)--The oxygen that is also created during equalization eventually will cause the positive plates to corrode and fail.

-Bill

icarus · September 2009

Re: Another noob question

No harm,no foul, we all get testy now and again, and I have had my knuckles wrapped on occasion. Another battery info site, and in some ways better, is :http://www.batteryfaq.org/

Good luck,

Tony

dwh · September 2009

Re: Another noob question

Just Me wrote: »

4 1/2 years old and I have never found the electrolyte below the plates. Usually, during the summer, I store them in a cooled garage hooked to a BatteryMinder® and fully charge/equalize them every month of so.

With the BM in the conditioning pulse mode, Bogart sees 12.9V and +.04A. When I re-start it, it goes to 13V and +.51A. The way I understand the BM, is that it senses when the battery is charged, then goes into the float/maintenance/conditioning mode. When I equalize, it burps like crazy.

FYI:

As I understand it, the Battery MINDers do something called "desulfation", which is different than "equalization". Desulfation is achieved with a high-frequency low-amperage pulsing, whereas equalization is done with a sustained steady high-voltage/amperage.

I've noticed that you have used both terms to describe what your Battery MINDer does, so I thought I'd take the opportunity to point out (to whoever may be watching) that there is a difference.

http://www.batteryminders.com/batterycharger/instructions/BatteryMINDerR-desulfation-method-unique.pdf

"Sulfation (sul-fay-shun), the number one cause of early battery failures, can be safely reversed, using high frequency electronic pulses. Unlike other pulse type chargers that claim this or similar sounding features, VDC’s BatteryMINDers® use a range of high frequencies. This ensures both old and newly formed sulfation will be safely dissolved in the shortest possible time. Using just one fixed frequency may remove some, but not all, especially long established – hardened sulfate crystals."

http://www.trojan-battery.com/BatteryMaintenance/Equalizing.aspx

"Equalizing is an overcharge performed on flooded lead acid batteries after they have been fully charged. It reverses the buildup of negative chemical effects like stratification, a condition where acid concentration is greater at the bottom of the battery than at the top. Equalizing also helps to remove sulfate crystals that might have built up on the plates. If left unchecked, this condition, called sulfation, will reduce the overall capacity of the battery."

For all I know, both techniques achieve a similar result, though I note that in my quickie research the Battery MINDer docs don't seem to mention "stratification", though their process may combat that as well.

I also note that the Battery MINDer instruction manual says that the "maintainance" mode is actually the "float" stage:

http://www.batteryminders.com/batterycharger/files/pdf/12117_RevB_032009.pdf

"FAQs
1. How long does it take to go into the float (maintenance)
mode with the flashing GREEN LED indicator?

A. It depends on the size, level of charge, amount of
sulphation, and the temperature of the battery. It can take
less then a minute, hours, days, or even a couple of weeks.
A digital voltmeter connected to the battery will indicate
the charging voltage. The voltage will keep increasing until
over 14 volts then decrease to a lower voltage in the float
(maintenance) mode, about 13.5V). The GREEN LED will
flash."i]sic[/i

Thus: The Battery MINDer is a two-stage charger with desulfation, which is different than, say, a two- or three-stage charger with equalization.

Also, according to the Battery MINDer manual:

"Desulphation Pulse 1.0A @ 3.26 MHz"

So...I wouldn't expect that desulfation pulse mode to register accurately - if at all - on your TriMetric.

Just Me · September 2009

Re: Another noob question

The way I understand the BM, is that it senses when the battery is charged, then goes into the float/maintenance/conditioning mode. When I equalize, it burps like crazy.

My bad. I didn't mean to indicate that my BM did the equalization. I use a Power On Board "Smart" charger to do that. I'll edit that for clarity.

Kamala · September 2009

Re: Another noob question

Regarding the readings on the Tri-Metric... How do you connect your chargers to the battery? If you are connecting directly to battery posts, the Tri-Metric may not read accurately. The negative charger connection should go to the shunt terminal opposite the one connected to the battery.

Just Me · September 2009

Re: Another noob question

Thanks for the concern. That's just the way I have it. The only wire on the battery side of the shunt is the Sig lead on the Kelvin terminal.

Just Me · September 2009

Re: Another noob question

I hate nasty battery acid, and I hate hydrometers.

Yesterday, after I took the BatteryMinder off, the voltage at:
3:00 PM 13.31V
3:30 PM 12.86V
7:30 PM 12.70V
10:00 AM 12.65V
1:00 PM 12.65V

I bought a hydrometer and went about checking the cells. As I was squirting the fluid back into a cell, the end blew off and got acid all over the battery, me and the compartment. I had a spray bottle of water there and sprayed my legs, arms and shorts.

The bottom of the float broke off when it hit the ground. Since I usually break the glass tube, I had an extra float and was able to continue. Later, Checker Auto replaced it with a different brand that has tighter fitting bulb and end cap.

It took several times filling and draining the hydrometer get a good, consistent reading on each cell. I couldn't believe it, they all came out 1.275. I equalized it last Saturday. Does stratification happen that soon?

Trojan says 1.277 +/- .007 @80° and to add .004 for every 10° above 80°. Electrolyte temperature was around 89°.
So, 1.277 + .004 = 1.281 +/- .007 = 1.274 to 1.288. At 1.275, I'm borderline full charge.

My Smart charger says the reconditioning mode may take up to 5 times. I think I've only use it 3 times so I'm running it again.

I realize that these readings don't show the true load capacity, but at least all the cells appear to be charged the same. There may be hope for these batteries yet.

Do these reading look ok?

Cariboocoot · September 2009

Re: Another noob question

Reading a hydrometer down to 0.001 is practically impossible. If all your cells are reading 1.275 then the battery is fully charged. I wouldn't worry about trying to get that last 0.002.

mshen11 · September 2009

Re: Another noob question

what is a GOOD hydrometer to have? i checked auto stores and they all look flimsy cheap and im afraid to get them

Another noob question

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