Battery charging questions

[Byron Kinnaman]

Originally Posted by stevebaz

On my 13 foot Scamp I put together my Solar system to recharge my single Group 27 lead acid battery. According to experts I did it all wrong and it works great. I used (2) 30 watt mono-crystalline panels from e-Bay because they fit through my escape hatch. I used a cheap Sunflex 10A Pwm controller also bought on E-Bay and used Radio shack 12 awg ofc wiring used for audio systems, why, because I had it and its 2 wire and very flexible. I use a jumper between the 2 panels long enough so they can fit alongside the escape hatch. I splurged on a trolling motor plug and socket and a large size fuse holder used in audio equipment. The controller was installed wrong as it is inside the trailer by my Progressive Dynamics PD-4045 panel. Trolling motor socket is mounted by my incoming trailer wiring which goes close to where I mounted panel. I put the panels on top of my trailer and toss the cable to the front of the trailer and plug it in. With the plug in the front I can move my panels at whim should I have a shade issue. I tie my panels together around the escape hatch with rope. The panels are not noticeable up on top. Last winter we were in Quartzsite and the sun is low in the south. I hung the panels over the side if the trailer with the same rope around the hatch. We used the trailer with the heater on as the overnight temps were in the low 30’s.
My Attwood 2 furnace doesn’t draw much power through out the night, comes on about once an hour at that temperature and I like the trailer fairly warm. All of our lighting is L.E.D.'s. I checked the battery every morning before the sun came up and we were about 90% and in four hours or so in the sun we were recharged. This was using a digital volt gauge and not fancy monitors. We use allot of light and have a water pump but we don’t have a bathroom or shower using power after sundown. It works for us and we are happy with it. We live in Southern California so there is far more sun than shade. It cost me about $200 to put it together. Prior to this project the only thing I knew about Solar was what a Panel looked like.

I think you've got the right idea and the implementation is working for you. The experts aren't always. I've talked to several "solar experts" most haven't a clue. They've picked up a few buzz words and listened to lots of other experts and the myths continue to spread. You done good.

[Raz]

Originally Posted by Byron Kinnaman

I think you've got the right idea and the implementation is working for you. The experts aren't always. I've talked to several "solar experts" most haven't a clue. They've picked up a few buzz words and listened to lots of other experts and the myths continue to spread. You done good.

yup. Raz

[ruscal]

Originally Posted by Carol H

Russ, is this a new battery or a battery that was on the trailer when you acquired it?

I can get by without much worry with one group 27 battery for 3 days of dry camping without draining it below 50% capacity & before I need to put the solar out to top it back up.

I use only LED lights in the trailer and use them only as really needed. If reading late into the night I use a head lamp. Fridge runs on propane so the lights and water pump and the Fantastic Fan (again used only as really needed) are the main power consumers and they are all pretty easy on the power consumption. When dry camping in winter and I need to use the furnace which is a power hog I restrict its use as much as possible - only to heat the trailer up prior to going to bed and again in the morning. I set it very low so it does not come on at all or if it does not that often during the night. If I know its going to be a very cold night I may even shut it right off to prevent it from coming on and off all night. Just use lots of blankets instead. I will often use the battery power for phone & camera battery recharging as well but not much else - I dont run the mp3 player (use a battery operated radio instead) or the tv when dry camping.

If its an older battery that has been drained below 50% cap or drained dry a few times its not going to hold much of a charge for long and it can be as you say a struggle to get by.

Carol,
Our battery is a Kirkland RV about 6 months old. I think its condition is normal, and healthy. We go pretty light on the lighting, and use headlamps. The furnace has been needed on a couple of occasions. The CPAP uses about 10% per night. I usually panic before the battery gets to 50% and then I charge it back up. I like to think of 50% as 0%, not wanting to deep cycle it too far. I think I'll allow the battery to get a little lower on the next outing and see how many days we can go.
Russ

[ruscal]

Originally Posted by Byron Kinnaman

There's a couple of ways to extend battery life. The one I prefer is to reduce usage. I changed all the lights to LED. In the case where you have of a water pump use water sparingly. Wet Ones for cleaning hands reduce a lot of water needs. Try to use the local bathroom facilities as much as possible.
Basicly try to determine where you can reduce the need for battery power. I can get by with a group 24 for 3 or 4 days, unless it's warm at night then I can go for weeks. The LED lights don't take much current. The only other thing I have is fan in the furnace. No TV, Stereo, or DVD player.
The other way is to increase the amount of battery or constant recharge from solar.
Power consumption is something each person has to evaluate for them selves and how to reduce it.

Byron,
We do splurge on a little xm boombox music, and like to use a tablet computer for internet, so have to charge the tablet and cell phone. I have not looked at the current draw on those items, so will have to check it out. We do try to utilize the public facilities when available to save water. I think the scamp only has about 10 gallons. We are getting pretty good about conserving the water. I can wash dishes using just the humidity in the air. (almost)
Russ

[ruscal]

Originally Posted by stevebaz

On my 13 foot Scamp I put together my Solar system to recharge my single Group 27 lead acid battery. According to experts I did it all wrong and it works great. I used (2) 30 watt mono-crystalline panels from e-Bay because they fit through my escape hatch. I used a cheap Sunflex 10A Pwm controller also bought on E-Bay and used Radio shack 12 awg ofc wiring used for audio systems, why, because I had it and its 2 wire and very flexible. I use a jumper between the 2 panels long enough so they can fit alongside the escape hatch. I splurged on a trolling motor plug and socket and a large size fuse holder used in audio equipment. The controller was installed wrong as it is inside the trailer by my Progressive Dynamics PD-4045 panel. Trolling motor socket is mounted by my incoming trailer wiring which goes close to where I mounted panel. I put the panels on top of my trailer and toss the cable to the front of the trailer and plug it in. With the plug in the front I can move my panels at whim should I have a shade issue. I tie my panels together around the escape hatch with rope. The panels are not noticeable up on top. Last winter we were in Quartzsite and the sun is low in the south. I hung the panels over the side if the trailer with the same rope around the hatch. We used the trailer with the heater on as the overnight temps were in the low 30’s.
My Attwood 2 furnace doesn’t draw much power through out the night, comes on about once an hour at that temperature and I like the trailer fairly warm. All of our lighting is L.E.D.'s. I checked the battery every morning before the sun came up and we were about 90% and in four hours or so in the sun we were recharged. This was using a digital volt gauge and not fancy monitors. We use allot of light and have a water pump but we don’t have a bathroom or shower using power after sundown. It works for us and we are happy with it. We live in Southern California so there is far more sun than shade. It cost me about $200 to put it together. Prior to this project the only thing I knew about Solar was what a Panel looked like.

Steve,
Looks like you have a good workable solution. What did the "experts" think was wrong with your system? I'm thinking about mounting the controller inside and putting a receptacle outside to plug in the panel cable also. My roof is too cluttered to put panels on, so a folding stand will have to do.
Russ

[Carol H]

Originally Posted by ruscal

Carol,
I like to think of 50% as 0%, not wanting to deep cycle it too far. I think I'll allow the battery to get a little lower on the next outing and see how many days we can go.
Russ

Thinking of 50% as 0% is a good practise so do I. I actually have a small battery monitor that set off a small alarm to let me know when it hits 60% so I have time to get some sort of charge happening before it hits 50%.

Do you have LED lights? those were probable the best investment I made in reducing power.

[Raz]

Like Steve, we have a very simple set up. With LED lights, water pump, and on a hot night, two fans, we use 5 - 15 amp- hrs per day. The panel will recharge the battery even on a cloudy day. It's a 42 watt amorphous cell I bought in 2004. Amorphous cells are not as efficient as crystalline cells but are very durable. The home brew controller is in a box that came with the panel. Raz

[stevebaz]

Originally Posted by ruscal

Steve,
Looks like you have a good workable solution. What did the "experts" think was wrong with your system? I'm thinking about mounting the controller inside and putting a receptacle outside to plug in the panel cable also. My roof is too cluttered to put panels on, so a folding stand will have to do.
Russ

The experts want super fancy controllers, heavier wiring and the controllers mounted where the battery resides or remote temperature sensing of the battery. My $20.00 cheap Chinese controller mounted inside the trailer not sensing the battery is a big one. You’re not dealing with a whole lot of power from small solar panels so don’t wait until the power is drawn down. Set up the solar as soon as you set camp and let it do its job. Then forget about the battery and go have fun. I know it’s hard not to worry about battery charge but I slowly trust it all works. This is my first year with the trailer. It has been a learning curve to just let go. I started out worrying about the systems. The refrigerator temperature, the refrigerator, the propane, the propane, the heater, the heater, the battery the battery, the solar, the solar, now it just when's dinner and who's making it. I guess it’s better than tent camping where it is always what did we forget.

[ruscal]

Originally Posted by Carol H

Thinking of 50% as 0% is a good practise so do I. I actually have a small battery monitor that set off a small alarm to let me know when it hits 60% so I have time to get some sort of charge happening before it hits 50%.

Do you have LED lights? those were probable the best investment I made in reducing power.

Carol,
I converted all the lights to LED's soon after we bought the Scamp after reading the posts on this site. It is nice to see how little draw they have when looking at the monitor.
Russ

[ruscal]

Originally Posted by stevebaz

The experts want super fancy controllers, heavier wiring and the controllers mounted where the battery resides or remote temperature sensing of the battery. My $20.00 cheap Chinese controller mounted inside the trailer not sensing the battery is a big one. You’re not dealing with a whole lot of power from small solar panels so don’t wait until the power is drawn down. Set up the solar as soon as you set camp and let it do its job. Then forget about the battery and go have fun. I know it’s hard not to worry about battery charge but I slowly trust it all works. This is my first year with the trailer. It has been a learning curve to just let go. I started out worrying about the systems. The refrigerator temperature, the refrigerator, the propane, the propane, the heater, the heater, the battery the battery, the solar, the solar, now it just when's dinner and who's making it. I guess it’s better than tent camping where it is always what did we forget.

Steve,
The experts are probably correct in that there is energy to be saved if you want to spend more money. Whether it is worth the cost is another matter. Very small gains for big money. Some people think buying a Prius for $10,000.00 more than a Honda fit is a good idea to eke out more efficiency, but it costs to get that extra free energy.
If your system provides enough energy to replenish what you use, that is all you need. A little reserve capacity for bad weather may be a good idea. I will probably go for a "fancy" controller with multi-stage charging just for the benefit of battery health and longevity. Your PD converter has that feature, so you can use it when the trailer is parked at home to maintain the battery. I will just use the solar for maintenance because my converter is single stage. (Dumb)
Russ

[ruscal]

Originally Posted by Paul Braun

If I may expand on some of your observations. First, I believe the panels put out considerable more that you realize, the usual voltage on a 75 watt panel is up to 18 volts. Since the controller is dropping the voltage between the solar panel and the battery from 18 volts to 13.4 the gauge of wire is not critical. I run over 100 feet using 14 gauge and I am positive the controller is still reducing the volts. If you run the resistance calculations you do not loose enough to make a difference.

The controller should be mounted as close to the battery as possible and the gauge wire here may need your attention. However, the inexpensive controllers only have 16 gauge on the output side so it may not make sense to go with anything larger.

Paul,
If you are using a 100' extension between a panel and controller, that is 200' of 14 gauge wire in the circuit. Probably about 5 volt loss if the panel put out 5 amps. Even a 50' extension costs 2.5v. Maybe it works, but I would want bigger wire.
My controller would need to be mounted inside the front closet, or outside in a WP enclosure with air vents to be near the battery. Neither are particularly ideal. Thanks for your input.
Russ

[Byron Kinnaman]

Originally Posted by ruscal

Paul,
If you are using a 100' extension between a panel and controller, that is 200' of 14 gauge wire in the circuit. Probably about 5 volt loss if the panel put out 5 amps. Even a 50' extension costs 2.5v. Maybe it works, but I would want bigger wire.
My controller would need to be mounted inside the front closet, or outside in a WP enclosure with air vents to be near the battery. Neither are particularly ideal. Thanks for your input.
Russ

You're about 4x too high.

[Raz]

Originally Posted by ruscal

My 2003 16' Scamp has an American brand converter, and a lead acid Costco RV 12v battery. I have installed a Trimetric monitor to see what is going on when charging and monitor power usage real time. I experience very long re-charging times, and see not much current being dumped into the battery. I also use a stand alone CTEK 7002 smart charger at times, but it is also slow. Any ideas?
Russ

Have you checked your battery for charge (12.6v) with a standard DVM? When I look at the Trimetric site I see 2 shunts available. The 100 amp, 100 mV shunt appears to be the smaller of the two. Perhaps I'm missing something but a 100 amp, 100 mV ( 1 milliohm) shunt would be sending 1mV to the instrument for each amp of current flowing to the battery. Charging a single battery might be too low for the instrument to be accurate. Even at 10 amps you will only see 10 mV which could well be overwhelmed in an electrically noisy trailer environment. Just a thought, Raz

[ruscal]

Originally Posted by P. Raz

Have you checked your battery for charge (12.6v) with a standard DVM? When I look at the Trimetric site I see 2 shunts available. The 100 amp, 100 mV shunt appears to be the smaller of the two. Perhaps I'm missing something but a 100 amp, 100 mV ( 1 milliohm) shunt would be sending 1mV to the instrument for each amp of current flowing to the battery. Charging a single battery might be too low for the instrument to be accurate. Even at 10 amps you will only see 10 mV which could well be overwhelmed in an electrically noisy trailer environment. Just a thought, Raz

Raz,
I just went out and looked. It is stamped 50mV. I did check the battery voltage with a Fluke back when I was setting up the Trimetric. It agreed at that time. I installed the meter about a year ago, and have forgotten many of the details pertaining to its operation. I have been simply toggling between modes to read voltage, current flow and direction, % battery charge, etc. I forgot how to enter the amp hours used mode, and will have to re-read the manual.
Russ

[ruscal]

Originally Posted by Byron Kinnaman

You're about 4x too high.

Jeez, I can't get this electrical stuff right! I found a voltage drop calculator at supercircuits.com and just plugged in 12v DC 200' 5amps 14ga and pushed the button. It says 5 volts drop. I believe it to be correct. It didn't have a choice for copper or al wire, so I figured it would be copper by default.
Russ

[multi-task]

I use a 100 amp shunt with my trimetric and it works completely fine. However you need to set the meter to use it. There are two options, it's default is for a 500 amp shunt, the other setting is for a 100.

[Raz]

Originally Posted by ruscal

Raz,
I just went out and looked. It is stamped 50mV. I did check the battery voltage with a Fluke back when I was setting up the Trimetric. It agreed at that time. I installed the meter about a year ago, and have forgotten many of the details pertaining to its operation. I have been simply toggling between modes to read voltage, current flow and direction, % battery charge, etc. I forgot how to enter the amp hours used mode, and will have to re-read the manual.
Russ

That appears to be the higher current shunt ( 100 microvolts for each amp flowing through it). Basically a shunt is a precision resistor placed in the circuit you wish to measure the current through. The voltage across it is proportional to the current flowing through it (Ohm's law). The shunt has to be large enough to produce a significant voltage but not so large as to effect the current. With either of these shunts you are operating on the low end, with very small voltages. Voltages you could not measure accurately with the average DVM. It's a little like trying to measure the thickness of a penny with a yard stick.

Next time your battery needs charging, disconnect it from the trailer and charge it with the CTEK charger. Over night should do. In the morning, check it with the DVM. If it's 12.6 V. or higher I would say the charger is working fine. Good luck, Raz

[ruscal]

Originally Posted by multi-task

I use a 100 amp shunt with my trimetric and it works completely fine. However you need to set the meter to use it. There are two options, it's default is for a 500 amp shunt, the other setting is for a 100.

Drew,
I'll check the setting. I'm pretty sure I covered that during the initial setup, but worth checking.
Russ

[ruscal]

Originally Posted by P. Raz

That appears to be the higher current shunt ( 100 microvolts for each amp flowing through it). Basically a shunt is a precision resistor placed in the circuit you wish to measure the current through. The voltage across it is proportional to the current flowing through it (Ohm's law). The shunt has to be large enough to produce a significant voltage but not so large as to effect the current. With either of these shunts you are operating on the low end, with very small voltages. Voltages you could not measure accurately with the average DVM. It's a little like trying to measure the thickness of a penny with a yard stick.

Next time your battery needs charging, disconnect it from the trailer and charge it with the CTEK charger. Over night should do. In the morning, check it with the DVM. If it's 12.6 V. or higher I would say the charger is working fine. Good luck, Raz

Raz,
The CTEK has worked in the past, but it is slow when topping off a 80% charged battery. The battery won't accept bulk rates unless discharged more. I'll do some current draw measurements comparing the Trimetric to the Fluke to see if the Trimetric is calibrated properly. It was showing negative flow even with the CTEK hooked up while camping a couple of weeks ago. The Trimetric showed the proper charging voltage, but the current was backasswards.
Russ

[ruscal]

Does anyone know if the meter shunt can be mounted exposed to the weather? Mine is mounted on the tongue of the trailer and exposed. The brass is showing some patina. I went to the Deltec site and could not find any info.
Russ
EDIT
I Called Deltec and got the answer. They sell marine grade shunts that are plated and hold up in corrosive environments. He said that corrosion and crud buildup will affect the calibration and will vary over time. He suggested that I clean the shunt with non corrosive solvent, and then enclose it in a plastic box with vent holes drilled in the bottom. I asked it the shunt could be calibration checked with a DVM and he said no. I has to be done on a calibrated standard bench.
I will clean mine, and mount it in a box.
Russ