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05-04-2013, 08:55 PM
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#1
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Senior Member
Join Date: Aug 2012
Posts: 1,076
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Quick Battery Charging While Boondocking
Just a question- why are there no gas powered generators that operate like the alternator in a car just for quick battery charging. Now, I'm familiar with all charging systems (aviation maintenance background), constant current, constant voltage, no stages, 3 stages, lead/acid, NiCad, etc and I realize that an alternator charges with a diminishing voltage charge and may not be the ideal method to charge a battery for maximum life but they seem to work well in cars for several years of battery life. I believe heat and staying charged have more to do with battery life than charging method. The strong point for an alternator charging system is speed of recovery. Most batteries , even depleted ones, will take a 90% charge in 30 mins with an alternator due to the high current input in the beginning. Yes, some heat is input to the battery but not enough to cause harm from my standpoint. My point is why not a quick recharge to 90 or 95% and then shut the noise off. I can live on 12 volts quit easily I just don't like to hear the gen set run for hours to recharge at 4, 5 even 8 amps.
To this end I am building a 50 amp alternator driven by a small Honda motor just to see how this would work in real life.
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05-05-2013, 02:35 AM
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#2
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Registered User
Damon Owners Club Workhorse Chassis Owner
Join Date: May 2008
Location: N. Palm Springs CA (in winter)
Posts: 2,420
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I like my alternative, solar and I carry a battery charger with extension cord for emergency use only. My father had an occasion in the middle of nowhere when the alternator died and he hooked up the charger to the battery and ran the generator while going down the road.
It came in handy too for toys and toads of friends too.
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05-05-2013, 08:26 AM
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#3
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Senior Member
Join Date: Nov 2007
Location: somewhere in the west
Posts: 1,168
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Question did not take into account the difference between a start battery, and a house battery which is quite different in charging requirements as a start batt requires a higher initial "jolt", while a deep cycle requires a lower, normally longer, charge.
I believe the answer to your desire for a high amp recharge lies in the AGM battery which accepts much higher charge rates without damage.
Also, in an practical answer, study of battery construction and limitations may be in order.
All IMHO
Ed
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05-05-2013, 08:44 AM
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#4
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Junior Member
Join Date: Aug 2012
Posts: 4
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I was a full time yachtie for 15years. 90% of the time we were at anchor(like boondocking) and had to provide all of our electrical power and water capability. You can build a charging system to minimize run time. It's not cheap but if you use it a lot, worth it. Here is some info that can get you started. Steve D'Antonio - Marine Consulting Services for Boat Buyers, Boat Owners, and Manufacturers
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05-05-2013, 10:01 AM
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#5
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Senior Member
Join Date: Aug 2012
Posts: 1,076
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Ed and Bruce thank you for your comments. Bruce, the reference you gave was a very well written article. BTW, the idea to use the gen set to power the battery charger to get home was a good one :-)
I live in "houseboat heaven" where we have large HBs with banks of 20 and 30 6 volt house batteries. Very few use 3 step chargers and many change out their banks every 2 years because of that, A VERY SIGNIFICANT EXPENSE. So, yes, 3 step charging is the best by far especially for huge banks.
I will look for more info on the charging alt size needing to be 25% of the bank capacity as the article stated. I've never heard that one.
There are many different internal regulators that are available for standard alternators. One aspect of using AGM or gel cells is the requirement for a specific charging voltage different from the voltage for a flooded cell battery. Just popping in an AGM won't work well unless the regulator is changed to the proper one.
When I look at the typical battery bank in a TT or RV it's 2 - 4 batteries. Given that internal regulators look at the state of charge in the bank by sampling the voltage, they do supply a large amount at first for a "bulk" charge and then taper off as the voltage of the battery comes up. Now, granted that stopping the charge at the bulk time provides a less than full charge it still brings the bank up to a good point for the day of boon-docking. Even a week of this "undercharging" would not be detrimental to the batteries as once the trip is on the way home the bank would be recharged to its fullest by the trip home. Battery life I do not feel would be compromised by this method for boon-docking. I just have a problem with running a gen set for many hours to recharge at a slow rate. Solar is a good choice but I'm still working on the gas powered alternator system.
I'll try out my quick charger and see how it works.
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05-09-2013, 12:24 AM
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#6
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Registered User
Join Date: Mar 2007
Location: Somewhere I guess?
Posts: 453
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That's my plan too. I don't have any solar yet but I will try to get at least a 100w panel around next month. I jst finished installing a new grey water tank (the original was gone) and that set me back about $350 for the tank and parts... installed it myself.
I know my way around electrical enough to install the solar as well. My van has a 2.7kw generator so it can recharge the batteries from the RV converter if need be, but I also have a regular 12v battery charger I can run via the generator if I get in a tight spot battery wise somehow.
I will only need to power LED lights (1156 warm white LED bulb replacements) and charge my cell phone at bare minimum.. and maybe run a 12v fan if it's a bit warm. My furnace lacks a blower, my fridge is a 3 way and the water heater is 120v only (which kind of stinks).
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05-12-2013, 10:41 PM
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#7
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Junior Member
Join Date: May 2013
Posts: 1
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I have a 33 ft 5th wheel and am considering adding solar so I can stay out of the camp grounds and hit remote fishing areas. Anyone know how much solar I need to do this? How about solar brands to use or avoid? How effective are solar panels for keeping batteries charged up on RVs?
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05-12-2013, 10:49 PM
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#8
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Registered User
Join Date: Mar 2007
Location: Somewhere I guess?
Posts: 453
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It boils down to what you want to run.
In my case, I will only need to run LED lights at nice, water pump on demand, smart phone charging, and a 12v fan for air circulation as needed.
Mine lacks a blower in the furnace no 12v needed for that. I can get by with 100-200w pretty well. You might need as much as 400-500 depending on what your needs are.
The idea is to have enough solar to compensate for what your needs are. You need at LEAST equal solar input as what you take out in a 24 hour period.
So lets say you use 100AH a day, you need to put back at LEAST 100AH to keep the batteries even.
So many people want to run their RV like a 3 bedroom house all on solar with a 100w panel.. that's not going to work in any way, shape or form.
A 100w panel puts out about 7 amps max during peak hours (which can be between 4-6 hours a day, depending). So you might get 28-42AH a day, maybe 32-50AH tops from a 100w panel. If you use 100AH, you'll need at least 200w or more solar to compensate, if not 300w.
My needs will be very small... if it's hot at night and I need a fan, 3 amps max for a fan for about 8-9 hours... about 24-28 AH for that. My LED lights take almost no juice.. but lets say 3 amps a day. Smart phone charging might use 2-3 amps a day since it's slow to charge. Water pump on demand might use at most 2 amps total. Mind you, i'm over compensating for some of these figures, they'll probably use less.... but that puts my usage around 35-38AH a day which is right in the range of a 100w panel. However, I think I may go with two 100w panels so I have extra. It's better to have too much than not enough, otherwise you'll have to run a generator or cut back on what you are running.
I would LIKE to be able to run my 3 way fridge on solar but it's probably unrealistic at 8AH. That's 192 AH per 24 hours. To compensate, I'd have to have 640w just for the fridge! (This is assuming the heater element runs 24 hours a day, that is). So I'll either not use it when off the grid, or run it on propane.
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