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Optimising house battery charging from the generator (21D)


pwyngaard@...
 

Hello!

We have a 2021 View 24D (21D). It has the stock power system: two 12V Group 31 105Ah lead acid house batteries, a Xantrex XC Freedom 2000 inverter/charger and 200W of solar on the roof with a Zamp ZS30A PWM controller/charger. It also has the stock compressor fridge that requires 50-60Ah/day to operate. On days we are not plugged into shore power and not driving to charge the house batteries, we use the generator to charge. I'm trying to think about how to optimize our generator utilization, as it's noisy and we don't like to run it.

The generator charges the house batteries through the Xantrex, which has bulk, absorption, and float modes (and equalization too). Bulk attempts to provide constant charging current until a configurable absorption voltage threshold is met, then maintains the absorption voltage until either the charging current falls below a threshold or six hours have elapsed, and then goes into float mode which maintains battery at 13.5V where it provides minimal charging current to maintain that voltage.

It would seem that bulk charging mode gives us the most bang for the buck, as the charger provides as much current as the house batteries will handle until a voltage threshold is met. After that, current is limited to ensure voltage doesn't rise any higher, so the noisy generator is not giving us as much charging value at that point.

1. Would folks generally agree that turning the generator off once the Xantrex transitions to absorption mode gives us the most bang for our "buck" (noise)?

The absorption voltage threshold is set in two ways: (1) if you specify a "custom" battery type you can set it to be whatever you want, or (2) if you specify a lead acid battery it sets the absorption voltage threshold based on a temperature setting. The unit does not have a battery temperature sensor, so you can set it to HOT, WARM, or COLD. Xantrex does not document the corresponding temperatures, but I called them and they said they are 100F / 70F / 40F for HOT / WARM/ COLD. The unit is set to HOT by default. The corresponding absorption voltages for lead acid batteries are 14.0V / 14.4V / 14.8V.

If I were to change the temperature from HOT to COLD, the generator would be able to drive more current into the batteries in bulk mode, getting us more bang for the "buck".

I know the purpose of these 3-phase charging algorithms is to avoid overcharging and gassing the battery. I just don't know how to quantify or mitigate the risk of overcharging.

2. What do folks think? Has anyone messed with the absorption voltage thresholds in their chargers? Is 14.8V a risky setting?

Interestingly, the Zamp charger has an absorption voltage threshold of 14.7V at 25C / 77F, with a -24mV/degreeC temperature compensation coefficient. So at the Xantrex's HOT/WARM/COLD temperatures of 100F/70F/40F, the Zamp's absorption voltages are 14.4V/14.8V/15.2V versus the Xantrex 14.0V/14.4V/14.8V. So Zamp is 0.4V higher than Xantrex at any temperature.

Thanks!

Peter


Jerry Knowles
 

Wow!  That’s way too technical for me.  I would only run my generator for an hour if my batteries go dow to 50% and wait for the sun to rise on the morning.

As an aside, is it more efficient to run the generator vice idling the engine.  Both fuels cost about $2.50 per gallon and I understand that you can idle a diesel without causing damage.  Engine is certainly quieter than generator.  Both generate about the same power.
Jerry K
18J


On Oct 17, 2020, at 9:24 AM, pwyngaard@... wrote:



Hello!

We have a 2021 View 24D (21D). It has the stock power system: two 12V Group 31 105Ah lead acid house batteries, a Xantrex XC Freedom 2000 inverter/charger and 200W of solar on the roof with a Zamp ZS30A PWM controller/charger. It also has the stock compressor fridge that requires 50-60Ah/day to operate. On days we are not plugged into shore power and not driving to charge the house batteries, we use the generator to charge. I'm trying to think about how to optimize our generator utilization, as it's noisy and we don't like to run it.

The generator charges the house batteries through the Xantrex, which has bulk, absorption, and float modes (and equalization too). Bulk attempts to provide constant charging current until a configurable absorption voltage threshold is met, then maintains the absorption voltage until either the charging current falls below a threshold or six hours have elapsed, and then goes into float mode which maintains battery at 13.5V where it provides minimal charging current to maintain that voltage.

It would seem that bulk charging mode gives us the most bang for the buck, as the charger provides as much current as the house batteries will handle until a voltage threshold is met. After that, current is limited to ensure voltage doesn't rise any higher, so the noisy generator is not giving us as much charging value at that point.

1. Would folks generally agree that turning the generator off once the Xantrex transitions to absorption mode gives us the most bang for our "buck" (noise)?

The absorption voltage threshold is set in two ways: (1) if you specify a "custom" battery type you can set it to be whatever you want, or (2) if you specify a lead acid battery it sets the absorption voltage threshold based on a temperature setting. The unit does not have a battery temperature sensor, so you can set it to HOT, WARM, or COLD. Xantrex does not document the corresponding temperatures, but I called them and they said they are 100F / 70F / 40F for HOT / WARM/ COLD. The unit is set to HOT by default. The corresponding absorption voltages for lead acid batteries are 14.0V / 14.4V / 14.8V.

If I were to change the temperature from HOT to COLD, the generator would be able to drive more current into the batteries in bulk mode, getting us more bang for the "buck".

I know the purpose of these 3-phase charging algorithms is to avoid overcharging and gassing the battery. I just don't know how to quantify or mitigate the risk of overcharging.

2. What do folks think? Has anyone messed with the absorption voltage thresholds in their chargers? Is 14.8V a risky setting?

Interestingly, the Zamp charger has an absorption voltage threshold of 14.7V at 25C / 77F, with a -24mV/degreeC temperature compensation coefficient. So at the Xantrex's HOT/WARM/COLD temperatures of 100F/70F/40F, the Zamp's absorption voltages are 14.4V/14.8V/15.2V versus the Xantrex 14.0V/14.4V/14.8V. So Zamp is 0.4V higher than Xantrex at any temperature.

Thanks!

Peter


David Harper
 

I thought that idling the diesel was not recommended.  Read something on an expediters web site that said it was not adviseale.  Said running slowly prematurely clogs the EGR valve, and may not generate enough RPM to get oil circulating properly.  Apparently there is a high-idle switch that is often used by ambulances and the like that are required to idle for extended periods.  This raises the idle to 1,200 or more to keep the whole system intact.

I have zero experience with this, so don't listen to me!  I have just always understood it not advisable to idle the Sprinter for very long.  I am sure Mercedes dealer would know.

DHH
2008VJ



On Oct 17, 2020, at 9:21 PM, Jerry Knowles <knowlesjv087@...> wrote:

Wow!  That’s way too technical for me.  I would only run my generator for an hour if my batteries go dow to 50% and wait for the sun to rise on the morning.

As an aside, is it more efficient to run the generator vice idling the engine.  Both fuels cost about $2.50 per gallon and I understand that you can idle a diesel without causing damage.  Engine is certainly quieter than generator.  Both generate about the same power.
Jerry K
18J


On Oct 17, 2020, at 9:24 AM, pwyngaard@... wrote:



Hello!

We have a 2021 View 24D (21D). It has the stock power system: two 12V Group 31 105Ah lead acid house batteries, a Xantrex XC Freedom 2000 inverter/charger and 200W of solar on the roof with a Zamp ZS30A PWM controller/charger. It also has the stock compressor fridge that requires 50-60Ah/day to operate. On days we are not plugged into shore power and not driving to charge the house batteries, we use the generator to charge. I'm trying to think about how to optimize our generator utilization, as it's noisy and we don't like to run it.

The generator charges the house batteries through the Xantrex, which has bulk, absorption, and float modes (and equalization too). Bulk attempts to provide constant charging current until a configurable absorption voltage threshold is met, then maintains the absorption voltage until either the charging current falls below a threshold or six hours have elapsed, and then goes into float mode which maintains battery at 13.5V where it provides minimal charging current to maintain that voltage.

It would seem that bulk charging mode gives us the most bang for the buck, as the charger provides as much current as the house batteries will handle until a voltage threshold is met. After that, current is limited to ensure voltage doesn't rise any higher, so the noisy generator is not giving us as much charging value at that point.

1. Would folks generally agree that turning the generator off once the Xantrex transitions to absorption mode gives us the most bang for our "buck" (noise)?

The absorption voltage threshold is set in two ways: (1) if you specify a "custom" battery type you can set it to be whatever you want, or (2) if you specify a lead acid battery it sets the absorption voltage threshold based on a temperature setting. The unit does not have a battery temperature sensor, so you can set it to HOT, WARM, or COLD. Xantrex does not document the corresponding temperatures, but I called them and they said they are 100F / 70F / 40F for HOT / WARM/ COLD. The unit is set to HOT by default. The corresponding absorption voltages for lead acid batteries are 14.0V / 14.4V / 14.8V.

If I were to change the temperature from HOT to COLD, the generator would be able to drive more current into the batteries in bulk mode, getting us more bang for the "buck".

I know the purpose of these 3-phase charging algorithms is to avoid overcharging and gassing the battery. I just don't know how to quantify or mitigate the risk of overcharging.

2. What do folks think? Has anyone messed with the absorption voltage thresholds in their chargers? Is 14.8V a risky setting?

Interestingly, the Zamp charger has an absorption voltage threshold of 14.7V at 25C / 77F, with a -24mV/degreeC temperature compensation coefficient. So at the Xantrex's HOT/WARM/COLD temperatures of 100F/70F/40F, the Zamp's absorption voltages are 14.4V/14.8V/15.2V versus the Xantrex 14.0V/14.4V/14.8V. So Zamp is 0.4V higher than Xantrex at any temperature.

Thanks!

Peter



Dick Stevenson
 

Hi all,

I come from the marine world of widely wandering boats.

Prevailing wisdom among this group is that using your diesel engine for periods of time only to charge your batteries is not good for the life of the engine. Diesel engines like to work and work fairly hard. Alternators are just generally not enough load to do that. The result is soot/carbon build up resulting, in part, because the engine does not reach optimal operating temperatures. Enough of this and the life of the engine is compromised.

I am not sure about the vehicles (long haul truckers for ex) who leave their rigs on idle when in truck stops for a meal. Sometimes it is to keep refrigeration going, but much of the time it just seems to be left idling.

Like the ambulance mentioned, why leave the engine in idle, even high idle, unless it is to make some of the systems on the ambulance functional.

My best, Dick Stevenson


old_b4_my_time
 

On Sat, Oct 17, 2020 at 09:24 AM, <pwyngaard@...> wrote:
two 12VV Group 31 105Ah
I'm not sure why they put these batteries in new coaches.   Maybe they get them at a discount :-)  Most people replace factory stock with two 6V golf-cart batteries (noted as GC2) wired in series because the golf cart battery in the lead acid family is the most durable, largest plated and is the only true deep cycle, something you can't really find in any line of 12V battery (trolling motor, et.al.). (From the GC2 decision, most branch off on name brand affiliation, AGM for those who don't like managing the water levels and it goes on from there, add a couple of cups of doctor feel-good and you've got a solution.)  I elected for two Duracel EGC2 manual maintenance models)  I have a separate charge converter set on permanent boost on a wind up timer wired directly to my series battery set which in my case doesn't interfere with the house converter because I only "wind it up" when out boondockign and the batteries fall below a 60% charge.   For my 230aH setup (50% of that they claim is usable) when I get down to about 55%, I start the generator, set the timer for 75 minutes and I'm up to 90%, ready for the next day by the time the timer clicks off.  One doesn't attempt to charge above 90% normally because at around 90% charge the generator run-time starts to climb exponentially for that final 10% so it's not worth it.  But then that means you are working from 90% the next morning but this is what I personally factor in as cost of doing business while relying on solar that gets cloud cover from time to time.  The unit I use for boost function only is a Progressive Dynamics with output of 70A and factory modified for 14.8VDC boost voltage.

Still that doesn't address your refrigerator drain and it's currently my opinion if one wants to live a full and robust life electrically while boondocking and with a compressor fridge, they are going to need to either go to a lithium setup or add two more GC2 batteries for a total of 4 (search here for all the reasons that this will overload your coach weight-wise, etc.)   I currently run with 2 laptops, 2 tablets, a few phones, normal LED lighting, water pump use, furnace use or multiple fan use in the summer, consume about 70-80aH/day while full timing.   The compressor fridge would break my bubble using my current GC2 system.   With the 21D house battery, I wouldn't even think of leaving the power pole but if you aren't hooked on the computer or TV like most people, you are likely going to be overbudget with the compressor fridge if you go with my dual GC2 solution and WAY over budget with your dual 21D solution.
 
--
Don - 2006 Navion J


old_b4_my_time
 

RE:  "Gassing the battery"
My manual maintenance set of GC2s don't seem to mind getting gassed.  (Of course I wouldn't want to play around with this had I chosen AGM.) With my cheap standard GC2 batteries, the solar controller set to 14.6V boost and the generator application powering the temporary 14.8V manual boost, and the generator utilized only on full cloud cover days, I loose about 1/8" to 1/4" of water a month (I think there's about an inch to play with between full and the time the water starts to crest the top of the plates.).   On average I use the generator charging at 14.8V to recover from a cloudy day about 3 weeks out of every year but I travel in southern areas normally and don't spend a lot of time in the PNW as many do.   Still one could just keep the water sufficiently above the lead plates and with that, be good to go.   If  battery life is reduced by 10, 20, 30 percent, considering  $100K just flew out the bank for a coach - may as well live a little and toss in a couple more hundred every couple of years and thus replace those bats a shade more often than the guy who claims his last 6 years..  After all what's the real reward in life being able to brag to others that you are running on the same battery set for the past 10 years?  Maybe your batts only last for two years but remember you can always buy a new set when they go bad.   Still I'm getting a good 2 years out of my dual GC2s and the only reason I upgrade is because I want the full aH possible out of them and since I mostly boondock and as a full-timer, I can't really afford to watch my daily supply cycle deplete year after year just for the sport of it.  

Still I don't run with the PD 14.8V on a daily basis because my 470W of solar takes care of me on all but those infrequent full-cloud days.   So I only go to 14.8V boost cycle when powered with the generator and recovering from a day of heavy cloud cover .   If the unit you are speaking of makes it easy to change settings, I suppose you could just set it for 14.8V for the cloudy days and shut the generator down when the SOC reached 90% or better and set it back to 14.4V or so for normal shore power day to day operation.   Otherwise I am only guessing but my philosophy is why stress the batteries with the higher boost voltage under normal usage and daily operation if you don't have to.   If I had the choice and it was easy, I'd slip up the dial to 14.8V only on the days you are getting any true benefit from it, e.g. recovering from clouds or rain and when you are not that excited about listening t the generator run all day long.

Still with that compressor fridge, you are at a quagmire because if you go boondocking often enough, constantly starting the generator to recover your undervbudget system is likely going to get old, even if you only have to do it once a day to "keep up" with the fridge. And all this is speaking of a GC2 battery setup.   As far as the 12V ones that come new in these vehicles, I'd donate them to a good charity and go from there.
--
Don - 2006 Navion J


Steve Alabaster
 

Also read on past messages that condensation in the engine is produced and would not be totally evaporated without temperatures being normal running temps (> 150). Could produce rust.

Steve 16NJ WA state


Jerry Knowles
 

Hi Don,
Well I just ran my generator for 90 minutes on this cloudy day and just recovered from 57.5 to 70.5.  Don’t know what the difference would be from your experience.  I have the Oman propane generator.

Does anyone know how I can rule out the inverter as a source of discharge by disconnecting?  I tripped the GFCI on the receptacle on my inverter, but Incan still turn the inverter on and off above the fridge.
Jerry K 18V


On Oct 18, 2020, at 9:47 AM, old_b4_my_time <donphillipe@...> wrote:

On Sat, Oct 17, 2020 at 09:24 AM, <pwyngaard@...> wrote:
two 12VV Group 31 105Ah
I'm not sure why they put these batteries in new coaches.   Maybe they get them at a discount :-)  Most people replace factory stock with two 6V golf-cart batteries (noted as GC2) wired in series because the golf cart battery in the lead acid family is the most durable, largest plated and is the only true deep cycle, something you can't really find in any line of 12V battery (trolling motor, et.al.). (From the GC2 decision, most branch off on name brand affiliation, AGM for those who don't like managing the water levels and it goes on from there, add a couple of cups of doctor feel-good and you've got a solution.)  I elected for two Duracel EGC2 manual maintenance models)  I have a separate charge converter set on permanent boost on a wind up timer wired directly to my series battery set which in my case doesn't interfere with the house converter because I only "wind it up" when out boondockign and the batteries fall below a 60% charge.   For my 230aH setup (50% of that they claim is usable) when I get down to about 55%, I start the generator, set the timer for 75 minutes and I'm up to 90%, ready for the next day by the time the timer clicks off.  One doesn't attempt to charge above 90% normally because at around 90% charge the generator run-time starts to climb exponentially for that final 10% so it's not worth it.  But then that means you are working from 90% the next morning but this is what I personally factor in as cost of doing business while relying on solar that gets cloud cover from time to time.  The unit I use for boost function only is a Progressive Dynamics with output of 70A and factory modified for 14.8VDC boost voltage.

Still that doesn't address your refrigerator drain and it's currently my opinion if one wants to live a full and robust life electrically while boondocking and with a compressor fridge, they are going to need to either go to a lithium setup or add two more GC2 batteries for a total of 4 (search here for all the reasons that this will overload your coach weight-wise, etc.)   I currently run with 2 laptops, 2 tablets, a few phones, normal LED lighting, water pump use, furnace use or multiple fan use in the summer, consume about 70-80aH/day while full timing.   The compressor fridge would break my bubble using my current GC2 system.   With the 21D house battery, I wouldn't even think of leaving the power pole but if you aren't hooked on the computer or TV like most people, you are likely going to be overbudget with the compressor fridge if you go with my dual GC2 solution and WAY over budget with your dual 21D solution.
 
--
Don - 2006 Navion J


David J
 

You can assume that the inverter is a phantom load. I gave up worrying about all of those, just install a little more solar, which doesn't need to be much (even if you have none) to keep up with all the things that need a trickle of 12 volts to stay happy. My design goal is to not have to think about the RV systems when I'm using it.


Dick Stevenson
 

Hi Steve, I believe that this is more of an issue for starting an engine for just a brief period and not waiting for it to get to operating temps. Running a diesel for periods to charge batteries will usually allow the engine to reach operating temps, but this no-load (or little load) condition for long periods will burn off moisture, but is still a killer to diesel longevity.
My best, Dick Stevenson


waydigs
 

I admit I have not followed this for any time, but letting any kind of engine idle for long periods of time is never a good idea.  If you will look at your MBZ operators manual you will see that they have an option  for a "fast idle" that one  could perhaps get as an add on.  
Wayne


waydigs
 

David J.
My thoughts exactly.  😁   Some things are just meant to be what they are and us mere mortals should not be too concerned..
Wayne


bike_for_life2003
 

Don,

I really enjoy reading your missives.  That said, not everyone wants to boondock for weeks on end.... We find our 12V flooded house batteries do just fine for an occasional night or two off shore power.  Yes, we have solar power..  a solar oven and a small solar charger for cell phones.  'Nuff said, eh?

-----------------------
Paul and Christine
06 View 23H in NW FL


old_b4_my_time
 

On Sun, Oct 18, 2020 at 02:11 PM, Jerry Knowles wrote:
90 minutes on this cloudy day and just recovered from 57.5 to 70.5
I have a 70 amp capable supply which supplies a constant 14.8V which charges two GC2 batteries.  If yours does not go that high, then you would not charge as fast.   I think I paid around $240 for this converter which is pretty pricy by my standards but it beats things out.
 
--
Don - 2006 Navion J


old_b4_my_time
 

On Mon, Oct 19, 2020 at 04:41 AM, bike_for_life2003 wrote:
That said, not everyone wants to boondock for weeks on end...
Granted.   Also not everyone wants tuna fish or Oscar Myer for dinner.   Each of us here presents our own "dish specialties" and those reading the menu get to choose what they want to eat and when for what meal. (And with that, there's no real value in saying tuna smells bad or franks are made of pig eyes, because the person who enjoyed them once will likely partake again.)  Still I seem to generate a lot of undeserved attention here for some reason LOL.   I am flattered though that you enjoy my contribution because otherwise I don't see that much kindness passed this way.  (Maybe a couple of thanks over history - but I enjoy exaggerating.)   Being only human, we each can only present what is our own experience and hopefully our audience can pick and choose from those ideas, gatering them collectively to assemble that which works best.   It is better I have found to be able to pick one's direction from a smorgasbord of ideology rather than to wrestle with the ideas of only a few.   It's also great in the rare occurrences where we celebrate the diversity of our contributors rather than challenging them when they don't match our own ideas.

In fact a fellow member here and I were talking offline recently and we were both surprised that we both noticed the same thing, and that's how the V/N group seems to be preoccupied with so many challenges of other's ideas rather than following a format similar to other great resources like Sprinter-Source and IRV2 where everyone there seems to present their take on things and with that, there's an absence of criticizing other's opinions.   Here after watching and participating for a good while, an underlying tendency toward challenges of ideas can be seen rather than what could be a much more friendly and helpful environment.  Of course also obvious is the prevalent "out-degreeing" or "out-experiencing" others, which gets a little silly after a while to be frank.   (And don't call me Frank LOL!).   Still please don't think I'm directing this toward you in any way other than being curios why I seem to command more than my fair share of attention and "call-outs".  I'm only presenting my own experiences.  Otherwise regarding the kudos for the entertainment perspective, I do appreciate it.  This is actually one of my life's specialties.  
--
Don - 2006 Navion J


lou Thomson
 

I havent seen any sprinter chassis that WGO uses with the factory high idle option that was available at the time in order to have the engine idle set at the correct RPM..this company I see does have an aftermarket product I looked into it as i liked the remote start also   https://www.midcityengineering.com/product/smartkey-starter-remote-start-alarm-for-mercedes-benz-freightliner-sprinter-sksng907rv/