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Using small generator to charge Batteries.


mrdfred

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I have 2 Interstate 12v deep cycle batteries and no onboard Generator or solar panel. I have a 1500 watt gen to use to charge my batteries when boondocking. I will use a 8 AMP 12v Stanley 3 stage charger to charge my batts. Should I disconnect the batts from the coach while charging? Any advice on this procedure? I could also plug the shore line into the gen, but I think the charger would be more efficient in charging the batts. Any help would be appreciated.

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With a 1500 watt generator you likely have around 1300 watts (check the long-term power rating to be sure) available for charging. With that kind of power you might do well with a charger that puts out more than 8 amps. How high you can go depends on your batteries (see link below) and the generator output. I'd look at getting a charger that will charge as fast as is safe since that will cut down on your generator run time.

 

http://www.trojanbattery.com/BatteryMaintenance/ChargerSelection.aspx

 

 

When selecting a charger, the charge rate should be between 10% and 13% of the battery's 20-hour AH capacity. For example, a battery with a 20-hour capacity rating of 225 AH will use a charger rated between approximately 23 and 30 amps (for multiple battery charging use the AH rating of the entire bank). Chargers with lower ratings can be used but the charging time will be increased.

 

Trojan recommends using a 3-stage charger. Also called "automatic", "smart" or "IEI" chargers, these chargers prolong battery life with their well programmed charging profile. These chargers usually have three distinct charging stages: bulk, acceptance, and float.

 

 

Another thing to consider is using your RV's converter to charge with, many converters today are very good battery chargers and if you have or can add a "charge wizard" charge controller to them they become excellent options. If you tell us about your converter we can tell you if it is going to do the job.

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Good Questions, here's my response:

 

"Should I disconnect the batts from the coach while charging?"

 

No need for that assuming all else is standard and working okay

 

"Any advice on this procedure?"

 

Of course, sparks (such as when connecting or removing a charger) are huge NO NO around batteries, especially while charging and especially around their tops where explosive

gasses may be present. If you were hooking up battery charger leads Id connect the Red/Positive FIRST and the Black/Negative LAST and reverse that when disconnecting (unhook

Neg first). ALSO DO NOT PLUG IN OR TURN ON THE CHARGER UNTIL AFTER THE LEADS HAVE BEEN CONNECTED TO THE BATTERIES. And then let the batteries rest and

stabilize (no more outgassing or bubbling) after turning the charger OFF before you unhook any charger leads as sparks may occur.

 

 

" I could also plug the shore line into the gen, but I think the charger would be more efficient in charging the batts."

 

I have no idea what type or brand or quality (if any) Converter/Charger the coach may already have built in, working and connected???????????????

 

If its an old style cheaper noisy humming buzzing type of typical RV Converter/Charger, which is more like a near constant voltage source (13.4.to 13.6), and NOT any 3 or 4 stage

modern progressive stage so called "Smart Charger" there's a good chance your Stanley 3 Stage Charger may do a better quality job of correctly charging your batteries HOWEVER

if its only an 8 amp unit it will take longer then the factory Converter/Charger if its more like a 20 or 30 amp device. A person could used the 20/30 amp for the initial faster Bulk charge

and then let the quality smart 3 stage charger complete the job BUT THAT REQUIRES YOU TURN THE CONVERTER/CHARGER OFF AFTER SOME TIME.

 

Not knowing what if any type or quality or brand of Converter/Charger you may have now I just cant answer your questions other then above about how to disconnect and that a quality 3/4 stage smart charger will do a better job of charging then an old style dumb constant voltage converter/charger although an 8 amp will take a longggggggggggg time.

 

John T

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Thank you all for your advice, especially Stanley P. for his suggestion about the Charge Wizard. I called my Trailer manufacturer and found out that the power converter in my unit was a Progressive dynamics with a built in charge Wizard. So now, all I have to do is plug the shore line into my generator and let the power converter mind the batteries. I would have never thought of finding this out without all of your help. :rolleyes::rolleyes:

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So now, all I have to do is plug the shore line into my generator and let the power converter mind the batteries. I would have never thought of finding this out without all of your help

On my rig with the Progressive surge protector it will not let the gen hook up without connecting the neutral/ground at the generator. If you don't have a surge protector will just plugging in the generator work?

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We'd just plug the converter into our generator to charge, that avoided any power problems as we were dumb and bought too small a generator for our needs. With your 1500 the size shouldn't be an issue but it can be incompatible with one of the fancy power systems. Plugging in the converter directly as we did will bypass the issue without fiddling your wiring.

 

I recall seeing wiring suggestion to deal with the grounding issue but can't recall where.

 

 

I blame my teachers who never taught me that a 1000 watt generator would only put out 843 watts after a couple minutes for my purchase of a too-small generator. Bad enough it wouldn't run the 950 watt microwave but the inability to run the 910 watt coffee pot was worse.

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On my rig with the Progressive surge protector it will not let the gen hook up without connecting the neutral/ground at the generator. If you don't have a surge protector will just plugging in the generator work?

 

Yes, but making up a ground to neutral plug for your genset will allow you to still use your surge protector. A cheap DIY plug will do just fine and only takes minutes to put together. Just a matter of buying a male plug end then using a wire to jumper the ground and neutral... or... cut off the end of an old extension cord, strip the wires, cross the ground and neutral, cap and tape it all up and plug it into your genset.

 

With a portable inverter type genset it's not really necessary to have the surge protector as the output is well regulated/protected already, but to me it's easier to shtick in a plug than it is to disable my surge protector... and then remember to turn it back on later.

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Make sure to that the fridge is set to run on propane.

I use a small Honda 1000 with the specific purpose of recharging batteries (camper batteries, 3 laptops, 3 cell phones, elect toothbrush etc.)

A bigger genny would be nice but we don't have the storage space.

Adding solar is the next step so that we can charge the small devices all day long with the use of an inverter.

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As I thing Stan said, the Progressive is not typically in the genset path. eg. the hardwired progressive should be wired before the transfer switch in the shore power line. But when using a portable genset on the shore power line you cannot avoid the Progressive. Putting the jumper on the portable generator will solve the Progressive issue. If you want to understand what is happening more, read this article I wrote some years ago. Hopefully it will be understandable.

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As I thing Stan said, the Progressive is not typically in the genset path. eg. the hardwired progressive should be wired before the transfer switch in the shore power line. But when using a portable genset on the shore power line you cannot avoid the Progressive. Putting the jumper on the portable generator will solve the Progressive issue. If you want to understand what is happening more, read this article I wrote some years ago. Hopefully it will be understandable.

After reading the technical info, I was unsure of my set up. I called the manufacture of my generator, Champion, and asked them. They said that my model has been used with many RVs, and at any rate, plug it in and see if it works, there will be no harm to either the RV or the generator. Sounds eminently practical! If it doesn't work, they said to attach a ground wire to the provided connection on the front of the panel and attach it to a stake in the ground. They don't believe this is necessary however. Also, I search the customer reviews on Amazon of people who purchased the same generator and found reviews of people using this generator with their RV with no reported problem. So far ... so good.

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