Topping off house batteries on generator?

[homelesshartshorns]

Will a 15-amp battery charger bring my house batteries full up while using a 1000-watt generator? 

[Kirk W]

It should if you run it long enough but it won't be quick. The maximum voltage it can supply is what determines if it will along with how many amps you are using when trying to charge the batteries. If you are using too many 12V appliances they may draw more than 15A and that will discharge your battery. It is the difference between the amps supplied and the amps in use that remains, if any, for charging the battery. You need to spend some time reading The 12V Side of Life by Mark Nemeth. 

[oldjohnt]

22 hours ago, homelesshartshorns said:

Will a 15-amp battery charger bring my house batteries full up while using a 1000-watt generator? 

SHORT ANSWER:   If alls well ???  it probably will given enough time !!

LONG ANSWER:

IT DEPENDS on the following:

1) What type of charger are you using (Smart regulated multi stage orrrrrrrrrrrr a basic less sophisticated more like a constant voltage perhaps 13.5 or so volt charger) 

2) What type of batteries (Flooded Lead Acid,, AGM,, or Lithium) they have different charge parameters.

3) State of Charge of the batteries, how low have they been ran down, 10% 20% 50% ?? Has 15 Amp Hours of energy been depleted or 30 or 100 Amp Hours or ????

4) How long the charger is operated. If it pumps a constant 15 Amps into the battery and it was 15 Amp Hours down it would (in theory actually different due to losses) take ONE HOUR  

5) What other loads might the batteries be supplying at the same time.  

WHY IT DEPENDS: The time it takes to charge depends on the batteries state of charge. Is it slightly discharged or is it near fully depleted ??? EXAMPLE A 15 amp charger can only supply a maximum of 15 amps so after one hour the most ENERGY (Volts x Amps x Time) it could deliver to the battery would be 15 Amp Hours per hour.

The answer can be computed if you consider the charger can supply a full constant 15 Amps (but that depends on battery) and if you know how much energy it takes to put the battery back to full charge,,, Simply divide Amp Hours of depleted battery energy by 15 Amps to get how many hours it would take. 

 A few wild guesses and pure speculation not knowing anything about your batteries but to give you the picture: An RV might have lets use a 200 Amp Hour rated battery and lets say it was 50% (100 Amp Hours) depleted THEREFORE if you pumped 15 charging amps into it would take 100/15 = 6.66 Hours to fully charge it HOWEVER there are losses and especially lead acid may not accept  x current for x time SO IT COULD TAKE 8 OR MORE HOURS ??? 

A 15 Amp Charger is small in comparison to maybe a 30 or 50 or 75 or more Amp typical RV unit and a typical RV may have at least 100 to 200 Amp Hours or more battery capacity which may be heavy discharged, SO A 15 AMP CHARGER MAY TAKE A LONGGGGGGGGGG TIME ..........

ITS IMPOSSIBLE TO ANSWER YOUR QUESTION BUT THIS MAY HELP YOU UNDERSTAND WHY. The above is NOT accurate ONLY approximations and examples trying my very best to help you see why your question cant be answered..

John T

Edited October 7, 2023 by oldjohnt

[homelesshartshorns]

Thanks for the explanation. I appreciate all the help I can get to try to understand my issue. Most all the tec stuff mostly makes me fall asleep!I have a 2000 Itasa Suncruser. I have no idea what kind of inverter/charger I have, or even where it is located.
I have two group 31 batteries that are only a few months old. We are doing more boondocking nowadays and find when my batteries are charged with the Alternator they come up to 12.7 or 8. And will last our needs overnight or longer. And as I run the generator each day that goes by, the batteries have less and less staying power. Until I start the rig again.
I have the idea that it's like a balloon at first and each day the generator and charger only pump the batteries up 80 percent of the day before.  So I understand this.
My question is how can I stay off the alternator or shore power without going to solar? 
I'm thinking I need a bigger battery charger to do what the alternator does. I have a 10 amp portable charger that only brings the batteries up to 12.6, whether charging for an hour or two or three.. same results. Falls down to 12.0 in just a few hours. Won't stay up like the alternator does. Looking for options. 

Edited October 7, 2023 by homelesshartshorns

[oldjohnt]

1 hour ago, homelesshartshorns said:

My question is how can I stay off the alternator or shore power without going to solar?

   In that case as long as your generator has adequate capacity ?? YOU NEED A QUALITY HIGHER RATED CONVERTER/CHARGER suitable for your batteries. Take a look at a so called Smart 3 Stage Regulated Charger maybe even a 40 to 50 or so Amp ?? (cant require more power than your generator can deliver)..   It sounds like your house batteries are flooded lead acid and a Smart 3 Stage Charger (to replace existing) will have Bulk, Absorption and Float charge levels which given time and battery condition can bring you back to near 100% SOC.. 

 

1 hour ago, homelesshartshorns said:

I'm thinking I need a bigger battery charger to do what the alternator does.

I think you got it !!!   If you have a 20 year old 15 Amp charger now, that's NOT very high rated plus it may not be any modern Smart type.  A new Smart 3 Stage Regulated charger isnt all that expensive and easy peasey to wire up. If you go that route remove/disconnect the old unit.. 

 John T

[Kirk W]

3 hours ago, homelesshartshorns said:

My question is how can I stay off the alternator or shore power without going to solar? 

You should be able to power something like this from the generator that you have. 35-Amp Car Battery Charger, 12V and 24V Smart Fully Automatic Battery Charger Maintainer Trickle Charger It is pretty difficult to find a charger for flooded cell batteries that is much higher current output, but this should be enough to do the job and not damage your batteries. 

[homelesshartshorns]

Mr. Kirk, does this being an 18-amp charger mean that my generator has to be able to produce 18 amps? 

[D&J]

On 10/6/2023 at 12:12 PM, homelesshartshorns said:

Will a 15-amp battery charger bring my house batteries full up while using a 1000-watt generator? 

Just plug your converter into the generator to bring the batteries up.

Denny

[oldjohnt]

  FYI Here's several more RV Converter/Chargers (for flooded lead acid, AGM, or lithium) in the 30,45,55,60,65,80 Amps I found on Amazon. Brands such as Progressive Dynamics (what I use), WFCO, Powermax, Go Power, etc. etc. 

Amazon.com : rv converter charger

HOWEVER with only a 1000 Watt GENERATOR (theoretically can deliver 8.33 amps at 120 VAC to power a charger) you are limited as to what size CHARGER you can use ????? As far as the Chargers DC output Power, i you operate at 14.6 charging volts, a 45 Amp Charger would be producing 45 x 14.6 Volts = 657 Watts Output.

Here's a typical 45 Amp charger that might work for your lead acid batteries provided your generator is big enough to power it, which it may well (but cant guarantee absent specs and data, consult manufacturer). 

Progressive Dynamics 45 Amp Charger:  Amazon.com: Progressive Dynamics PD4645V Inteli-Power 4600 Series Converter/Charger with Charge Wizard - 45 Amp : Automotive

Do your homework, check out these and other chargers and reviews, see if the manufacturer can tell you what current the charger actually draws from the 120 VAC source. IMPORTANT YOU NEED TO KNOW THAT !!!!! If your generator can only provide 8.33 Amps, the charger obviously can't require more WELL DUH lol  

   MAKE SURE ITS SMART 3/4 STAGE REGULATED TECHNOLOGY (to NOT overcharge or damage your batteries),,,, SUITABLE FOR YOUR BATTERY CHEMISTRY,,,, AND DOES NOT REQUIRE OVER 8 AMPS TO OPERATE. Disable/remove old charger, plug new unit into 120 VAC (Genset or shore), insure proper protection and wire its output to your batteries EASY PEASEY You got this !!!!!!!!!! 

PS consider a shunt based battery monitor which will accurately show your batteries State of Charge SOC 

PS When you look at chargers many size models, even low amperage, will use a 15 Amp rated power source (like a standard household 15 Amp Receptacle) and a 15 Amp Cord and Plug HOWEVER that does NOT mean they draw 15 Amps to operate !!! Of course, the more DC Output charging Amps they deliver to the batteries the more 120 VAC Input current they need. 

 Questions ?? 

John T

 

Edited October 7, 2023 by oldjohnt

[D&J]

We have a Power Dynamics 60 amp converter charging 2 AGM Optima Blue tops and I just plug my converter into my very old Honda 650 watt generator., it makes it grunt but it's old and doesn't seem to care and it doesn't trip the overload. It burns a lot less fuel than my build in 5KW generator.

Denny

[Kirk W]

16 hours ago, homelesshartshorns said:

Mr. Kirk, does this being an 18-amp charger mean that my generator has to be able to produce 18 amps? 

Quote

【35-AMP FAST BATTERY CHARGER】12V 35-Amp and 24V 18-Amp 9-stage quick battery charger, charging speed is 7 times faster than 5-Amp automatic chargers.

If you read the specs quoted above, it can supply up to 35A at 12V or 18A at 24V. Since you have a 12V battery it would supply a peak output of 35a early in the charge, tapering off slightly as the battery voltage rises to around 25-30A later in the charge cycle. Remember that the generator supplies 120V power so the output of the charger will be slightly less than 10 times as much current at 1/10 of the voltage it draws from your generator. Since watts is equal to amps times volts, the generator can supply 1000 watts, divided by 120V, or 8.33A at 120 volts.  The charger will supply a maximum of 35A times the output voltage of 12V or a total power of 420 watts so your generator should easily handle the load with some to spare. Having done a bit more looking at Amazon, the Schumacher FR01237 Fully Automatic Battery Charger might also be a good choice for somewhat less money. I have had very good experiences using Schumacher battery chargers and maintainers. 

While the advice from John is valid, those are converter/chargers and would need to be installed into your RV to replace the existing converter and then you would need to connect the RV to the generator, rather than connecting the battery charger directly to the generator. 

The short answer is that your generator can supply the necessary amps to run either of the two suggested battery chargers.

Edited October 8, 2023 by Kirk W

[oldjohnt]

14 hours ago, D&J said:

We have a Power Dynamics 60 amp converter charging 2 AGM Optima Blue tops and I just plug my converter into my very old Honda 650 watt generator., it makes it grunt but it's old and doesn't seem to care and it doesn't trip the overload.

  Thanks for that input. Strictly for the OP's info, a 60 Amp Converter/Charger iffffff charging the full 60 Amps (seldom max 60, and not long subject to battery and specs) at 14.6 Volts = 876 Watts. As I posted above, a 45 Amp Charger at 14.6 Volts = 657 Watts so the OP's 1000 Watt Generator should (no warranty consult company) handle it allowing plenty for losses and inefficiency.

You already know this but again for the OP if he replaces his old charger with a new one (be it 40 or 45 or 50 etc) I advise to do as I did and remove/disconnect the old, install the new fed by 120 VAC (from EITHER shore or Generator power) and wire its output to his batteries SAME AS OLD ONE WAS... Piece of Cake !!!!!!!!! 

 

12 hours ago, Kirk W said:

se are converter/chargers and would need to be installed into your RV to replace the existing converter and then you would need to connect the RV to the generator, rather than connecting the battery charger directly to the generator.

 You got that right Kirk, might it be said great minds think alike lol.. Thats how I did it and advised he do the same IE "remove/disconnect the old, install the new fed by 120 VAC from EITHER shore or Generator power".  The EITHER (source of 120 VAC) depends on his transfer arrangement that selects if his RV is being fed by genset orrrrrrrrr shore power. Many, especially older RV's, did NOT use any Transfer Switch, but instead the RV power cord was plugged into EITHER shore power orrrrrrrrrr directly to a Generator (to get the necessary 120 VAC) !!!!!!!! IT DEPENDS ON HIS WIRING CONFIGURATION and I suspect he has a portable generator in which case he (after rewire as above) simply plug the RV power cord direct into the generator (one of the EITHER sources of 120 VAC) same as he would plug it into the Utility if available....

OP NOTE HOWEVER CAUTION you ONLY have a 1000 Watt Generator, so if you plug the RV power cord into your genset  (and wired as I described) TURN OFF MOST OTHER 120 VAC LOADS so ONLY the new converter/charger is being powered !!!!!!!!!!!! You may get by powering a few SMALL 120 VAC loads other than your converter/charger when plugged to Generator,,, but use caution and carefully select what other small loads might be available 

 Have a great Sunday everyone, best wishes God Bless

John T

   

Edited October 8, 2023 by oldjohnt

[JimK]

None of the above comments seem to address the issue.  Batteries must be fully charged fairly frequently or they will degrade.  This degrading results in short battery life and the inability of the batteries to perform.  Degraded batteries can sometimes be returned to near original performance with what is called conditioning or equalization.  That means charging at a high voltage, about 15 amps, for about 8 hours.  (Check the manufacturer's specs for this.)

To prevent the need for equalization and to maintain battery life and performance, it is necessary to fully charge batteries periodically; i.e., at least every few days.  Check the manufacturer's manual for what is needed to achieve a full charge.  For my batteries, they need to be charged at 14.3 volts for at least 2-4 hours.  That is a long time and impractical for using a generator to recharge.  During this time, the batteries are only absorbing a trickle charge so a larger generator or better charging unit will not help speed this up.

A generator works great for bulk charging but solar is really preferred for the 2-4 hours of trickle charging needed to reach a full charge.  Shore power is the only reasonable alternative.

[oldjohnt]

5 hours ago, JimK said:

Degraded batteries can sometimes be returned to near original performance with what is called conditioning or equalization.  That means charging at a high voltage, about 15 amps, for about 8 hours.  (Check the manufacturer's specs for this.)

    GOOD INFO Jim, thanks for posting. Many of the modern quality so called Smart Regulated Chargers IF THEY HAVE THE EXTRA 4TH EQUALIZATION STAGE perform Equalization on Flooded Lead Acid batteries on a regular scheduled basis. The more common 3 STAGE only have Bulk, Absorption and Float stages.  When I used Flooded Lead Acid batteries my Progressive Dynamics Smart 4 Stage Charger had the 4th Equalization Phase. I did NOT use Equalization chargers when I ran AGM batteries.  The Amazon link I posted above has modern Smart Regulated Chargers compatible for use with Flooded Lead Acid Batteries in the 30,40,45, MANY 55, some even higher current ranges, they (40,50,60 or more amps) are NOT hard to find, but with his only 1000 Watt Generator, the size of his Charger is somewhat limited. 

I agree Solar or Shore Power have their advantages for keeping house batteries more properly and fully charged, but his question concerned Generator power, so I offered the best in that limited situation IE a BIGGER charger lol regardless if powered by EITHER utility or his generator.......

  Amazon.com : rv converter charger             (Tons of chargers over 50 or more Amps) 

PS Even if one has a high current rated charger that does NOT mean a battery(s) (especially lead acid) will necessarily consume that many charging amps for X time. In GENERAL charge time will be less if you're pumping more amps into the battery (reason for bigger charger) HOWEVER you shouldn't exceed however many amps the battery is capable of accepting so as not to cause harm. Thats where Smart regulated 3 stage chargers shine !!!! The OP mentioned TWO batteries which could justify using a bigger charger as if balanced charging current is 1/2 in each battery.   

Best wishes Jim, I enjoyed sparky chatting with you

 John T

Edited October 8, 2023 by oldjohnt

[homelesshartshorns]

I am starting to get a feel for my issue with all your comments and suggestions. My rig does charge the batteries at 14 volts, so my problem after years of traveling in this unit has only become an issue for me when off the grid for a week or so. I do use a 1000-watt generator and plug the rig directly to it to charge our toys and was hoping it would keep my house batteries up. But you're never too old to learn. So, my cheap fix will be to only boondock for three or four days at a time. I'm old, my rig is old, so I am not inclined to spend the money to fix what for the most part is not broke. Thanks for all your impute.