rvupgradestore.com Composet Products Fridge Defend
RV Life Magazine RV Park Reviews RV Trip Wizard

Author Topic: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY  (Read 722 times)

Markowb

  • ---
  • Posts: 8
INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« on: July 24, 2020, 10:11:44 AM »
I dry camp from time to time. What would inexpensive generator would you recommend that would charge my battery in about 4 hours. I only want this to charge my battery.
Thank you

Lou Schneider

  • Global Moderator
  • ---
  • *
  • Posts: 10288
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #1 on: July 24, 2020, 10:30:32 AM »
The generator won't directly charge your battery, it sends 120 VAC to your converter which in turn charges the battery.

This means the generator size will be determined by the power draw of your converter and whatever else is turned on at the same time.

A 1000 watt inverter generator is marginal, it may or may not be able to supply the power you'll need.  Prices start at less than $200 for the Sportsman to $900 or more for a Honda or Yamaha.

A 1600-2000 watt inverter generator will definitely do what you want, again prices range from $400 for a Wen or Sportsman up to $1100 for a Honda or Yamaha.

Avoid the $99 specials.  Their 2 stroke engines sound like a chain saw running wide open.

The Harbor Freight 2000 watt Predator inverter-generator at $500 is a good compromise between price and durability.  It's often on sale or you can find a 20% off coupon.

All of the inverter generators at a given price point are about the same - as you go higher in price you gain in areas like durability and the availability of replacement parts. The Honda EU1000i generator I bought 20 years ago is still running fine. You want an enclosed inverter generator because they're much quieter than a conventional generator with an exposed engine.  Do a Google or Amazon search for the best prices.
« Last Edit: July 24, 2020, 10:47:25 AM by Lou Schneider »

donn

  • ---
  • Posts: 3894
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #2 on: July 24, 2020, 10:34:57 AM »
Be careful with cheap generators.  They tend to be noisy and not really neighbor friendly.  Harbor freight Preditor series does offer a couple that are kind of quiet as do other places.

Lynx0849

  • ---
  • Posts: 658
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #3 on: July 24, 2020, 11:54:11 AM »
No reason he canít use a conventional battery charger plugged in to a small generator. It would have to support the 12v loads and charge the battery but not power the AC loads.

A 2000 watt class inverter should do it, be quiet enough and light enough to stow.
Rob & Deryl, Nettle & Tigger
Clyde, a 2015 RAM 3500 Cummins Longhorn SRW w/ARE cap
14í V nose utility trailer as mini toy hauler (for now)
A Grand Design 337RLS in the future.
N1ICB (Nursing 1 Ice Cold Beer)
N1SPA (up to my neck in hot water, as always)

Isaac-1

  • ---
  • Posts: 3620
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #4 on: July 24, 2020, 12:03:07 PM »
You don't say what size battery you have, regardless assuming you have a conventional lead acid battery, if it is significantly drained you are not going to fully charge it in 4 hours  due to the charge acceptance rate of a lead acid battery.  Simply put with a lead acid battery, the first 80% of the capacity can be charged fairly fast, but the last 20% gets slower and slower before eventually being fully charged.  Therefore you should expect with 4 hours per day of charging and running the battery down to 50-60% charge each night, to never get over 85-90% charge, which in the long run is bad for the battery.
2002 Safari Trek 2830

Lou Schneider

  • Global Moderator
  • ---
  • *
  • Posts: 10288
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #5 on: July 24, 2020, 12:18:06 PM »
No reason he canít use a conventional battery charger plugged in to a small generator. It would have to support the 12v loads and charge the battery but not power the AC loads.

Most conventional battery chargers will only produce about 10 amps on a continuous basis.  Many will do up to 50 amps but that's only for a few minutes before they shut down until they cool off.

120 watts (12 volts x 10 amps) is hardly an efficient use of a 1000-2000 watt generator.
« Last Edit: July 24, 2020, 12:19:49 PM by Lou Schneider »

Isaac-1

  • ---
  • Posts: 3620
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #6 on: July 24, 2020, 03:03:13 PM »
I don't know about that, it depends on the generator, my Honda EU1000i on ecothrottle mode running at low engine speed only puts out about 250 watts before throttle up.  Still a larger charger would be good, which is where the onboard converter comes into play as it allows the battery to charge at a higher rate, plus provides power to the other DC systems in the RV while the generator is running, so perhaps a couple of hundred watts or so if lights etc. are  being used at the same time, more if you are running any AC appliances.
2002 Safari Trek 2830

NY_Dutch

  • ---
  • Posts: 6066
  • Home is where our wheels are!
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #7 on: July 24, 2020, 07:18:22 PM »
Years ago I had a little 1.5 HP gas engine mounted on a board along with a belt driven single wire 12-volt alternator. I charged many batteries with it when a 120 VAC source was not available for my charger. As I recall, the only parts I bought for it were the belt and one pulley. The alternator came from a car i was parting out and the engine from a broken farm sprayer pump.
Dutch
2001 GBM Landau 34' Class A
F53 Chassis, Triton V10, TST TPMS
2011 Toyota RAV4 4WD/Remco pump
ReadyBrute Elite tow bar/Blue Ox base plate

Chakara

  • ---
  • Posts: 224
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #8 on: July 24, 2020, 10:22:58 PM »
  For just charging a 1000W should be enough for most rigs.  You don't state what you have as to rig/battery/charging systems so I'm guessing here.

  If the above is true, I agree with the others and loo for an inverter generator.   You and your neighbors will like the quiet.

  Honda is the bee's knees in this space for quietness and reliability (I have a 13 year old one).   But Yamaha is a close second in the forums.  Below that I don't know......

Good luck!
-Chak
2018 Arctic Fox 27.5L
2015 Chevy 3500 Dually LTZ


Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 71040
  • RVer Emeritus
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #10 on: July 25, 2020, 09:30:42 AM »
The issue here is expecting to charge in 4 hours. You can't fully charge even a modest size 12v battery (Group 24?) in 4 hours, but you can get to around 80%-90% level.  The typical 8-10A automotive charger would be hard-pressed to do it, but a 45-55 amp RV converter/charger probably would.  In any case, you only need about 600-800 watt generator to power the charger only. Problem is, there are usually at least a few other items that will try to use some 120vac power if allowed. If you want to charge with a minimal size generator, you are going to have to make sure some things are disabled from using 120v.

A better choice is a 1000-1200 watt generator to give you some cushion on the power demand. They aren't much larger or more expensive.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

AkSpaktown

  • Posts: 1
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #11 on: September 14, 2020, 09:40:39 AM »
First time posting. What have you guys found to be the quickest way to charge the batteries when boondocking? I have two 6v 235AH golf cart batteries in series for 12v. My travel trailer converter is a wf-8955PEC but I'm not sure how fast it charges. I own a 2000w interter generator for charging. Should I use the converter on the camper or should I buy a separate battery charger (like a 40amp)? Please add links to what to purchase.

Thanks
« Last Edit: September 14, 2020, 09:44:44 AM by AkSpaktown »

Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 71040
  • RVer Emeritus
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #12 on: September 14, 2020, 10:51:14 AM »
The WFCO 8955 converter/charger is capable of up to 55A charging. The 55 amps are shared between charging and whatever the house amp demand may be, so keeping lights and such off leaves more for battery charging.

The main limit, however, will be the batteries themselves.  They will only accept so many amps/hour and that number decreases as the charge builds up.If you buy a high speed charger to try to force more amps faster, the battery life will be shortened, perhaps greatly.

It can take 12-16 hours to bring a battery back to 100% charge, so when off-grid, most RVers operate with their batteries between 50% and 80% of full charge. Your 8955 will bring a battery 50% back up to 80% in 2-4 hours, but getting from 80% to 100% may take several hours more.  The optimal rate of bulk-charge is  about 1/4 of the battery capacity in amp-hours, so your 230 AH battery bank can be charged at roughly 230/4 = 57A. That rate is sustained only during the bulk charge phase; once the battery begins to fill up the rate will slow down simply because the battery won't accept a high rate.

Don't discharge much below 50% r battery life will also be be shortened.
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

garyb1st

  • ---
  • Posts: 3637
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #13 on: September 14, 2020, 11:01:11 AM »
AKSpatown, we have a Honda 2000 and use it to charge the our two golf cart batteries when dry camping.  It works fine.  But it will not bring our batteries up to a full charge in 4 hours.  As Gary RV_Wizard says, the generator will only bring your batteries to maybe 80-90%.  That will keep you going, but if you don't find a way to fully charge your batteries you could shorten their life.  I don't know how long it takes to fully charge a battery with a 2000 watt generator and it will very based on other draws while charging.  For example, when I have it on, I'll be using my computer and maybe the electric coffee pot.  They both take energy and reduce the amount going into the batteries.  The problem, as I understand it, is the batteries like a full charge and by continuously charging them to only 80% you may shorten their life.  Running a generator until they are fully charged will take longer.  Just how much longer I don't know.   
Gary B1st

2005 Pace Arrow 35G
2016 Jeep Wrangler


Poverty exists not because we cannot feed the poor, but because we cannot satisfy the rich.

Gene50

  • ---
  • Posts: 153
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #14 on: September 14, 2020, 11:21:35 AM »
  both Honda and Yamaha 1000 and 2000 W inverter generator is come with the VC charging cord but charging is limited to 8 amps or under so youíre coach inverter/converter Charger may be the best bet. 

 I found that camping with no hook ups and being limited to a two hour limit on generator operations once in the morning and once in the evening, if I combined the use of a 100 W solar panel during the day  that I didnít need to run the genset so long in the evening.

With the solar panel, I hooked it up directly to the batteries without a charge controller and the batteries topped up fine without exceeding a 14.5 V maximum On a nice sunny day.

Maybe a combination set up like that is your solution.
2011 F350 Lariat 6.7PS
2015 Dutchman Denali 262RLX

Mark_K5LXP

  • ---
  • Posts: 436
  • 2005 Itasca Sunova
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #15 on: September 14, 2020, 01:15:41 PM »
Bulk amps, below 80% SOC restore pretty quickly.  It's when you get north of that the rate will diminish to a handful of amps and that's irrespective of the converter used.  That's all the batteries are going to accept.  If you "force" current by jacking the voltage way up you'll end up damaging the batteries, so that's not a useful option.  You just have to let them sip until they're full.

It's true that if you keep a lead acid battery at 80% for an extended period it will be damaged.  One has to quantify "extended" though.  It's a cumulative effect, something that would have to take place repeatedly for periods extending into weeks.  For someone that's using their batteries for boondocking for a week or two at a time a few times a year, this kind of short cycling has little impact.  If you're full time and leave it below 80% every day then life will be markedly diminished.   

The 20% to 80% SOC operating range is perfectly OK if that represents a sufficient number of Ah for what you're trying to do.  If you can get them north of 80% then fine, and certainly once you're back on shore power you want to restore a full charge and maintain them that way.  But don't be concerned much about running a partial state of charge for short trips, they can take it.  Your batteries are there to run your stuff, don't be afraid to use them.

Mark B.
Albuquerque, NM

jubileee

  • ---
  • Posts: 639
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #16 on: September 14, 2020, 05:29:45 PM »
  Iíve fabbed up a half a dozen or so 12 volt generators like Ny_Dutch was talking about. Friends with camping trailers wanted them because they were light, cheap, and fast charging.
  If youíre handy, have welder and some scrap, easy to make. HF 6.5 hp engine always on sale $100. One wire gm 80-100 amp alternator $80. Belt and misc bolts $5.
   If you have an old lawn mower with a decent engine, itís only a little more work to rig alternator to vertical drive engine. I did one and fella wanted it left on mower base and wheels so he could push it around.

Mark_K5LXP

  • ---
  • Posts: 436
  • 2005 Itasca Sunova
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #17 on: September 14, 2020, 06:30:06 PM »
If you have an old lawn mower with a decent engine, itís only a little more work to rig alternator to vertical drive engine.

Been there, done it.  Results are not stellar.  Alternators need to spin upwards of 6000 RPM to reach anywhere near their rated output, way faster than your basic lawnmower can run.  With mine it peaked around 400 watts at full throttle.  Using pulleys can give you the RPM multiplication you would need but with somewhat greater mechanical complexity.  Not to mention it won't charge a battery any faster than a converter so you get to listen to it hammering away like a contractor generator for hours.  When you figure you have to build the thing, it only puts out 12V and it's no smaller than a commercial equivalent gnerator having 2-3x of 120V output I consider it a solution waiting for the right problem to come along. 

https://www.qsl.net/k5lxp/projects/Lawnernator/Lawnernator.html

Mark B.
Albuquerque, NM

NY_Dutch

  • ---
  • Posts: 6066
  • Home is where our wheels are!
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #18 on: September 14, 2020, 07:13:19 PM »
Been there, done it.  Results are not stellar.  Alternators need to spin upwards of 6000 RPM to reach anywhere near their rated output, way faster than your basic lawnmower can run.  With mine it peaked around 400 watts at full throttle.  Using pulleys can give you the RPM multiplication you would need but with somewhat greater mechanical complexity.  Not to mention it won't charge a battery any faster than a converter so you get to listen to it hammering away like a contractor generator for hours.  When you figure you have to build the thing, it only puts out 12V and it's no smaller than a commercial equivalent gnerator having 2-3x of 120V output I consider it a solution waiting for the right problem to come along. 

https://www.qsl.net/k5lxp/projects/Lawnernator/Lawnernator.html

Mark B.
Albuquerque, NM

Your link shows that a lot of labor and pieces can make a nice commercial looking unit that I agree, would be better served by a commercial generator. The 12-volt unit I built and described above took very little labor and minimal expense. I ran the alternator at about 4,500 RPM with the motor running at 3600 RPM. With a good muffler, the unit wasn't very loud at all. But it sure did the job when commercial power wasn't available for battery charging.
Dutch
2001 GBM Landau 34' Class A
F53 Chassis, Triton V10, TST TPMS
2011 Toyota RAV4 4WD/Remco pump
ReadyBrute Elite tow bar/Blue Ox base plate

Seon

  • ---
  • Posts: 201
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #19 on: September 14, 2020, 07:20:11 PM »
Several years ago I bought a WEN 2000 generator from Amazon and a battery charger used to charge batteries in my boat, tractor and especially for my cl c parked in my barn that doesn't have electricity. Often times the RV starting battery was dead so I'd start the generator, connect the charger to the battery, set the timer to one hour which was enough to start the motor.

Here's a link to the Wen's review.
https://generatoradvisor.com/wen-56200i-review/
26' R-Vision Trail-Sport
'07 Yukon SLT XL
Lake Camanche, CA

Gary RV_Wizard

  • Forum Staff
  • ---
  • *
  • Posts: 71040
  • RVer Emeritus
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #20 on: September 15, 2020, 07:09:10 AM »
The WFCO 8955 is rated at 940 watts, but that's a worse case power draw and would mean it was putting out the full 55 amps @ 14v.  Still, that's what you need to plan for so a 1000W generator would be minimum and 1200-1500 a better choice.

There are cheap, small generators available. Somewhat noisy and vibrating, but they get the job done. A nice Honda or Yamaha is a superior piece of equipment but cost 2x or 3x the other brands. An inverter-generator will be more quiet under most conditions, so worth the extra cost in my opinion. You can usually find a portable inverter generator in the 1200 watt range for $400-$500. Here's one:

 https://www.amazon.com/Westinghouse-iGen1200-Portable-Inverter-Generator/dp/B01N2AKRTT
Gary
--------------
Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Tom55555

  • ---
  • Posts: 263
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #21 on: September 15, 2020, 07:29:19 AM »
If you invest in a portable generator meaning hand held. I recommend one you won't outgrow meaning it will run your RV AC.

 https://www.amazon.com/Pulsar-G2319N-Gas-Powered-Generator-Capability/dp/B00YFT914I/
« Last Edit: September 15, 2020, 10:14:19 AM by Lou Schneider »
2015 Winnebago 22R

wndopdlr

  • ---
  • Posts: 27
Re: INEXPENSIVE GENERATOR TO CHARGE A 12V BATTERY
« Reply #22 on: September 15, 2020, 05:18:14 PM »
Years ago I had a little 1.5 HP gas engine mounted on a board along with a belt driven single wire 12-volt alternator. I charged many batteries with it when a 120 VAC source was not available for my charger. As I recall, the only parts I bought for it were the belt and one pulley. The alternator came from a car i was parting out and the engine from a broken farm sprayer pump.

Love the ingenuity!
2018 Outdoor RV 24KTS