12 volt battery charging boondocking

[eamarquardt]

I think this statement precludes one from fully charging a discharged battery in a mere twenty minutes:

"9.1.1. The BULK stage is where the charger current is constant and the battery voltage increases, which is normally during the first 80% of the recharge. Give the battery whatever current it will accept as long as it does not exceed 25% of the 20 hour (expressed "C/20") ampere hour (AH) capacity rating so, if you can only put back in only 25% per hour it's gonna take 4 hours to get back to full charge, 10% of the Reserve Capacity (RC) rating, I'm not sure if they mean you can't put in, in amps, more than 10% of the RC time, in minutes, or not but they seem to be clear that there is a definite limit to the current one can safely use of the wet batteries do not exceed 125° F (51.5° C), and VRLA batteries do not exceed 100° F (37.8° C).

If you discharge a 100amp/hour battery you can get about 50 amp hours from it. If you want to put that back much power back into it in twenty minutes yer talking 150 amps which far exceeds any interpretation of the guidelines above. It just ain't a viable plan.

As far as: "where do you think most off the (say 150 amp) output goes when "electrical system" is below the preset regulated voltage..." it doesn't go anywhere as it doesn't get generated in the first place. If you look at the output lead of an alternator there is no way it's gonna carry 150 amps for very long at all. The internal resistance of the battery and the voltage regulator will limit the current.

Cheers,

Gus

[rollintent]

Well If I go with the tow vehicle route I think the isolater seems worth the time to me anyways for my comfort. I understand many are comfortable without it and that it is not "needed". Back on the solar panel topic. Lets say I had a 100 watt panel parked under an oak tree somewhere in the midwest all day. It won't get direct sun at all. Would it or could it produce enough power to replace any usage from the battery?

I read somewhere that if even a small shadow hits a panel that is otherwise exposed to direct sun maybe even 5% of the panel shaded it will be totally unproductive or shut down as it was put in the article. Wouldn't this be the case in the full shade situation? Or, Would it be that the whole panel recieves a reduced but even amount of light across all of it's cells would it just have much reduced output.

Is anyone running their solar panel not attached to the roof of the trailer, parking the trailer in the shade and running a short cord out into the sun and placing the panel on a stand some relatively small distance from the trailer where it would get direct sun exposure. I had thought about making a rack for the solar panel to be in the back of my pickup while towing and connected to the battery on the tongue of the trailer and when I got where I was going I would take the panel out of the bed of the pickup and prop it up in the sun while my trailer was mostly in the shade if such a spot was available and if not place it in the best possible spot. I know it all depends how much I feel like messing with that but I am mostly trying to find out just how much shade will limit a panel's output.

[eamarquardt]

Shadow Catcher and BDOsborne seem to have the most experience with panels. From what I've heard overcast isn't as bad as shade. There have been reports that success can be had even in a forest.

I suspect that moving the panels to open sunlight would be the best compromise. You'd have to be careful though as if you can easily move them some one else can also easily move them right out of your possession.

The biggest thing one can do, though, is to conserve. I used to spend a week away from the dock at a time when we had our boat. I had a shore powered battery charger so when we left the dock all three 100 amp/hour batteries were pumped up. I generally only used one (and held two in reserve for starting the engine) and ran the engine only about a half hour per day to make hot water via the heat exchanger. We used virtually no energy during the day (no computers and such back then) and at night we only ran a couple of florescent lights, the propane solenoid for a bit, a TV and VCR for one movie, and the anchor light. We never ran even one battery down.

You don't have to replace juice that you don't use.

Cheers,

Gus

[bdosborn]

I read somewhere that if even a small shadow hits a panel that is otherwise exposed to direct sun maybe even 5% of the panel shaded it will be totally unproductive or shut down as it was put in the article. Wouldn't this be the case in the full shade situation? Or, Would it be that the whole panel recieves a reduced but even amount of light across all of it's cells would it just have much reduced output.

Shade bad! Here's why: 8% shading = 94% reduction in power.

Is anyone running their solar panel not attached to the roof of the trailer, parking the trailer in the shade and running a short cord out into the sun and placing the panel on a stand some relatively small distance from the trailer where it would get direct sun exposure.

Yup, I do it all the time and it works great. I'd do a folding panel if I had to pick just one panel, especially if you like to camp in the shade.



Here's a link to my system of roof mounted panels and a folding panel: Boxcar PV System

Here's how to make your own folding solar panel: DIY Folding PV Panel

I set a new system record for peak power production this weekend, 17 amps at 14.3V. That was with dirty panels and a bad angle to the sun.

Bruce

[Dale M.]

I think this statement precludes one from fully charging a discharged battery in a mere twenty minutes:

"9.1.1. The BULK stage is where the charger current is constant and the battery voltage increases, which is normally during the first 80% of the recharge. Give the battery whatever current it will accept as long as it does not exceed 25% of the 20 hour (expressed "C/20") ampere hour (AH) capacity rating so, if you can only put back in only 25% per hour it's gonna take 4 hours to get back to full charge, 10% of the Reserve Capacity (RC) rating, I'm not sure if they mean you can't put in, in amps, more than 10% of the RC time, in minutes, or not but they seem to be clear that there is a definite limit to the current one can safely use of the wet batteries do not exceed 125° F (51.5° C), and VRLA batteries do not exceed 100° F (37.8° C).

If you discharge a 100amp/hour battery you can get about 50 amp hours from it. If you want to put that back much power back into it in twenty minutes yer talking 150 amps which far exceeds any interpretation of the guidelines above. It just ain't a viable plan.



Cheers,

Gus

Well, the wire on my 110 amp alternator on jeep is a #8 wire but surge amperage only last maybe 10 to 15 minuets.... IF it were continuous, meaning forever it may be some what questionable ..

And where except out of the blue does this statement comes from...

As far as: "where do you think most off the (say 150 amp) output goes when "electrical system" is below the preset regulated voltage..." it doesn't go anywhere as it doesn't get generated in the first place. [b]If you look at the output lead of an alternator there is no way it's gonna carry 150 amps for very long at all. The internal resistance of the battery and the voltage regulator will limit the current.

Because a alternator (or generator) will only put out current to supply the demand up to max capability of charge unit (alternator, generator, inverter) at battery float voltage...

Spent 38 years in telecommunications setting up and adjusting battery charging systems, be it small little 12 or 24 volt battery system for aux generators or sealed battery systems for remote suites (cell site system and fiber optic systems) or main 52 volt, 2,000 amp hour systems powering main telephone offices....

I do know something about battery charging...

Dale

[milliejohn]

With all the hot air, how about wind generators?

LED lights and low current draw toys are a big help when dry camping, 2 six volt golf cart batteries wired in series gives you 12 volts and a much bigger amp/hour capacity, extending your time between charges just as 2 gas tanks extend your driving range between fill ups.

Moving solar panels to catch the sun may be fine for charging, but I would rather move camp to catch more fish.

[Dale M.]

Did not really mean to get deep in to technicalities of the chemical and physical aspects of battery charging... The "20 minute" remark was sort of off the cuff..... Real intent of my original comment was there is a complete system available with out the need for extra solar or wind or generator... Or if you choose one of the alternate systems and it fails, recovery or backup is a mere plug in to TV for battery charge if you have charge while towing connections....

I'm out of this before it turns into a war zone of theoreticals....

Dale

[Shadow Catcher]

I have a high voltage panel, a mistake on my part as it was meant for a residential grid tie system. It puts out 40+ volts and it works far better than it is supposed to. When we stayed at Big Basin Redwoods State Park we were in the trees and watched a movie powered the laptop the lights and XM radio. and the one 185W panel brought it up to 100% SOC the next day. The one difference is that the refrigerator was in the car and running from its battery.

[Bogo]

How long will it take to charge a 100-130 amp hour 12 battery back to 100% from an 80% full state with a small generator and a good automatic charger? If I can charge the battery once or twice a day with the generator running for one to maybe three hours I would be happy with that. I am also needing advice on brands, sizes, and types of chargers that have proven themselves through use with people that really rely on them.

If you decide to go the generator route. The last 10% to 20% of the charge takes a long time. Why not just skip it. Use a deep cycle battery down to 60% charge, and then recharge it back up to 80% to 90%. You don't need to recharge a lead-acid battery to full charge each time. In fact during recharge when nearing full charge is one of the periods when the battery takes the most damage. Figure out how much fuel the generator uses per hour when charging, and only give it enough fuel for the time you wish to charge. When it runs out, charging stops. A full recharge and equalize only needs to be done every couple weeks, and that is something that is maybe better done when hooked up to the power line, or using a solar system.

Yes, I'd use a large charger to reduce generator run time. Get a RV Converter with a modern battery charge controller in it, these are 120VAC to 12VDC converters. It will be both useable with the generator, and at electric RV sites. It can also be used to keep the battery topped off when the TD is parked at home. The Progressive Dynamics Inteli-Power 9270V is an example: http://www.pplmotorhomes.com/parts/rv-c ... 0-amps.htm It outputs 70 Amps which will make short work of recharging your batteries. There are other sizes and brands out there. The PD 9270V will suck down 1250 Watts @ 120VAC. If you are using a Honda "2000 Watt" inverter generator that leaves some wattage spare for recharging laptops and cell phones directly from AC. The reason I "" the "2000 Watt" is the real long term use output of the generator is something like 1800 Watts and it likely isn't good running it a absolute maximum for long periods. I've debated on if the 2000 or 3000 is better to get. I'll likely end up with the 3000IS as it will run a RV air-conditioner. The 1000 isn't worth it in my view as it is louder than the 2000, and costs nearly as much. The Honda inverter generators are relatively quiet. Quiet enough that you likely won't mind one running at your camp site.

[rollintent]

Thanks to all for the input. It all helps in one way or another.

Thanks for the links to your page Bruce. Definitely got some ideas there. You said you got some of your panels from E-bay. Is there a big difference in output and durability between some of the economy panels (Chinese) and other brands? I know I always try to not get suckered by lowest price alone but I am not opposed to saving a few bucks here and there either. Lets face it I won't be putting these out for use every day. If they work for a few days at a time over the next 5-10 years. I would be fairly satisfied I think. Are there some brands you can recommend or suggest? Has anyone made a good Youtube video on rigging these things up like making wiring modifications attaching charge controlers and meters etc. geared for camper purposes? I have found a few videos but not that get into the details of wire size and changing wiring harnesses and more custom setup details.

[bdosborn]

I did a write up a few years ago, try here for basic info:

FAQ:Solar Panel without the Technical Stuff

I've bought a couple of solar panels off eBay from this guy:

UL Solar

His panels are okay, at least they have been for the week or three mine are in the sun every year. I don't think I would buy them for a house size array but they're okay for a teardrop. Here's a very nice panel, a little big for what you want but top quality:

Kyocera Panel

Remember to check the charging voltage of the panel, you want a 12V panel so you can use a cheaper PWM controller (like the Sunsaver).

Bruce

[rollintent]

Bruce,

Thanks for keeping guys like me from wasting our money and time.

[drewh1]

I looked all over for an answer to this question but haven't found it.

Can I have solar charging system hooked up to the battery AND the car charging system without a switch? Or do I need to isolate the solar system while the car is running? I am considering a 65Watt solar panel system with a solar charge controller.

Basically I want to drive away while charging the battery without having to remember to switch anything.

thanks,

[bdosborn]

Yup, no problem connecting everything to the battery. They all play well together and will come on and off line automatically without the need to switch anything or worrying about overcharging the battery.
Bruce

[NoResults]

I have a 2000i inverter generator from Costco (basically same as a Yamaha and uses the same engine. Should you charge the battery from the dc outlet or use the ac outlet to another charger. I have a onboard trickle charger but think the direct to battery from the dc connection would be best. Any recommendations.

Thanks

Dave