36 replies to this topic

[LAWNMOWERMAN]

What is the voltage at the house battery with the truck running?It should be close to 14v.

[DesertDave]

It sounds like you have checked for voltage drop between the truck and camper and you don't really have any, so you probably have no major issue there.

 

My experience is that driving the truck (even for 8 hours) never gets my battery bank above 85%.  I say this because  of the charging scenario that my solar system goes into when I stop driving - it is never in float mode, always bulk or absorption.  So I always plug in my camper when I return home to get the batteries closer to 100%.  Even the factory charger/converter doesn't get them to 100%, according to the charging scenario of the solar.  It does get them close, as I only need 4-5 Amp Hours (AH) from the solar to kick it into float mode, which is my best available data that the batteries are fully charged.

 

There is no way that a 100W panel will replace what your fridge requires.  I have measured between 5AH a day up to a max of 28 AH a day from a single 100W panel.  (I have a Zamp 100W on the roof).  If you find a cloudless day, park in full sun from 10AM to 4PM, during late June, you will get more than that, but in practical use I don't count on more than 25AH per panel if I am parked where it will charge between 10 and 4. 

 

Your fridge will draw something between 50 and 60 AH a day.  Maybe a little more is some scenarios.  So I suspect on a normal good charging day you would run a deficit of 25 to 35 AH .  If you don't want to damage your AGM battery it is best not to always drop it below 50%, although occasional drops down to 30% or even 20% may not damage it, as long as it doesn't reside there - ie you get it back to 100% very soon afterwards. There are probably differences between makes of AGM batteries - you should read what your battery specifications are for charging and discharging, not assume what internet folks like me say, since I have Lifeline batteries and their literature quotes different numbers than say the Excide AGM specs are.

 

I did the math before I bought my camper, but only had the on-line marketing and technical materials available for my calculations.  As a general rule it seems that the load data has been fairly accurate (ie the 2.2 to 2.5 AH draw for my fridge) while the charging potential of the vehicle charging system and the solar panels is probably only 75% to 80% of what you will read as their output.  I think that the panel literature is quoted under what some might call 'ideal' situations or else a standard testing scenario.  It is useful in comparing products to each other, but perhaps should be discounted a bit when estimating what you will experience in daily use.

 

I also have the Renogy flexible panel which I use as a portable, and it is also run through the same Zamp controller as the roof mounted panel.  Unless I am in ideal solar conditions I am still running a daily power deficit even with the two panels charging my batteries.  So in normal use even 200W of solar won't  completely keep up with the fridge draw.  So I also have 300AH of battery capacity, which seems to let me base camp with minimal charging for three days before I risk battery damage (say in the winter) and possibly a day or two longer if I can get some decent solar charging.  I would need more solar if I wanted to truly claim I could camp 'indefinitely'.

[MarkBC]

...What I noticed is that my separator was turning off and on....

 

 

I don't understand why your battery separator is cycling. Your alternator should be putting out enough power to maintain the minimum lock in voltage. I would check the alternator output or a large cyclic load under the hood.

 

Yep -- From my experience the separator should not be turning off and on when the truck is running.  Mine doesn't. 

 

I'd recommend a solar panel on the roof connected and charging all the time.  Most/many/(all?) solar charge controller are 3-stage so have the ability to really top off the camper battery -- so it reaches a full charge.

[Ethergore]

What is the voltage at the house battery with the truck running?It should be close to 14v.

I am only getting 13.5v. I was thinking this was fine as the starting battery was charged and disconnected from the aux battery. Also the ac was running as I was trying to simulate slow off roading with the ac on to see if I could get a charge.

[Ethergore]

It sounds like you have checked for voltage drop between the truck and camper and you don't really have any, so you probably have no major issue there.
 
My experience is that driving the truck (even for 8 hours) never gets my battery bank above 85%.  I say this because  of the charging scenario that my solar system goes into when I stop driving - it is never in float mode, always bulk or absorption.  So I always plug in my camper when I return home to get the batteries closer to 100%.  Even the factory charger/converter doesn't get them to 100%, according to the charging scenario of the solar.  It does get them close, as I only need 4-5 Amp Hours (AH) from the solar to kick it into float mode, which is my best available data that the batteries are fully charged.
 
There is no way that a 100W panel will replace what your fridge requires.  I have measured between 5AH a day up to a max of 28 AH a day from a single 100W panel.  (I have a Zamp 100W on the roof).  If you find a cloudless day, park in full sun from 10AM to 4PM, during late June, you will get more than that, but in practical use I don't count on more than 25AH per panel if I am parked where it will charge between 10 and 4. 
 
Your fridge will draw something between 50 and 60 AH a day.  Maybe a little more is some scenarios.  So I suspect on a normal good charging day you would run a deficit of 25 to 35 AH .  If you don't want to damage your AGM battery it is best not to always drop it below 50%, although occasional drops down to 30% or even 20% may not damage it, as long as it doesn't reside there - ie you get it back to 100% very soon afterwards. There are probably differences between makes of AGM batteries - you should read what your battery specifications are for charging and discharging, not assume what internet folks like me say, since I have Lifeline batteries and their literature quotes different numbers than say the Excide AGM specs are.
 
I did the math before I bought my camper, but only had the on-line marketing and technical materials available for my calculations.  As a general rule it seems that the load data has been fairly accurate (ie the 2.2 to 2.5 AH draw for my fridge) while the charging potential of the vehicle charging system and the solar panels is probably only 75% to 80% of what you will read as their output.  I think that the panel literature is quoted under what some might call 'ideal' situations or else a standard testing scenario.  It is useful in comparing products to each other, but perhaps should be discounted a bit when estimating what you will experience in daily use.
 
I also have the Renogy flexible panel which I use as a portable, and it is also run through the same Zamp controller as the roof mounted panel.  Unless I am in ideal solar conditions I am still running a daily power deficit even with the two panels charging my batteries.  So in normal use even 200W of solar won't  completely keep up with the fridge draw.  So I also have 300AH of battery capacity, which seems to let me base camp with minimal charging for three days before I risk battery damage (say in the winter) and possibly a day or two longer if I can get some decent solar charging.  I would need more solar if I wanted to truly claim I could camp 'indefinitely'.

Thanks for the thorough response. What you are saying about your battery bank only getting to 85% is more in line with what I hear from other forums. So this makes me think that other than the cycling on and off of my separator my battery is charging as expected from my alternator.

I'm fairly sure my factory charger gets my battery to 100% as I have the iq4 installed but I can't confirm other than by checking voltage. I can't verify with my charge controller like you because I just realized it is not a 3 stage charger:-(

As far as my solar being under matched for my needs I am really just using it to supplement. From dark until light during a 90 degree night here in redlands, ca I drained my 75 ah battery down from 12.8 to 12.4 (maybe 35-40% depending on who you ask) so that is 26-30 ah for 12 hours in hotter temp than I plan to camp in. That makes your guess at the use of my fridge door on. I agree I need a second panel if I plan on not driving but for now I never sit for a whole day. I always do some driving.

I'm really hoping that for now at least I can use the panel to run the fridge when I'm parked during the day. Then I can get another panel for when I plan on camping in one location for multiple days.

It sounds like what I need to do is make sure my alt is charging correctly, add solar to the roof and get a bigger battery bank. Maybe since my charge controller isn't 3 stage and my separator might be giving me trouble, I'll spring for the ctek DC to DC charger to get 3 stage charging from my alt and my solar.

What batteries do you have to get 300 ah?

[Ethergore]

Yep -- From my experience the separator should not be turning off and on when the truck is running.  Mine doesn't. 
 
I'd recommend a solar panel on the roof connected and charging all the time.  Most/many/(all?) solar charge controller are 3-stage so have the ability to really top off the camper battery -- so it reaches a full charge.

Thanks for sharing your experience. How low do you usually discharge your battery to? Does it not cycle even if it's discharged too far ie past 50%?

I think you are right about the solar on the roof. Seems like the way to go.

[MarkBC]

... How low do you usually discharge your battery to? Does it not cycle even if it's discharged too far ie past 50%?...

 

It could be that I'm not understanding -- either the question or maybe I don't understand the system as well as I think I do...so I don't want to mislead you because of my ignorance.

That said, I assumed that the alternator -- through the separator -- charges the camper battery no matter how low the camper battery's voltage gets, whenever the truck is running.  When I said that mine doesn't cycle off and on I meant that it's always on when the truck's engine is running.  (well, to be honest, all I know is that I've never found it not charging -- but that doesn't prove that it's always charging)

 

But for me, the truck's contribution doesn't matter much anymore (so I don't have to understand it much anymore) because I have so much solar panel on the roof -- 240 watts.  Some will say that that's overkill -- and they're probably right.

On my recent 3-week trip to southern Utah I turned off the camper electrical system (the main switch) whenever I was driving (thus disabling charging of the camper battery by the truck alternator) as a test to see if I could run the camper indefinitely on solar power alone, without input from the truck alternator.  And I could and did.

(my DC compressor fridge runs on a dedicated line from the battery, so it still runs when the camper electrical system is off)

[Ethergore]

It could be that I'm not understanding -- either the question or maybe I don't understand the system as well as I think I do...so I don't want to mislead you because of my ignorance.
That said, I assumed that the alternator -- through the separator -- charges the camper battery no matter how low the camper battery's voltage gets, whenever the truck is running.  When I said that mine doesn't cycle off and on I meant that it's always on when the truck's engine is running.  (well, to be honest, all I know is that I've never found it not charging -- but that doesn't prove that it's always charging)
 
But for me, the truck's contribution doesn't matter much anymore (so I don't have to understand it much anymore) because I have so much solar panel on the roof -- 240 watts.  Some will say that that's overkill -- and they're probably right.
On my recent 3-week trip to southern Utah I turned off the camper electrical system (the main switch) whenever I was driving (thus disabling charging of the camper battery by the truck alternator) as a test to see if I could run the camper indefinitely on solar power alone, without input from the truck alternator.  And I could and did.
(my DC compressor fridge runs on a dedicated line from the battery, so it still runs when the camper electrical system is off)

That's awesome you can run it that way. How much battery storage do you have?

I guess my thinking is that when my auxiliary battery gets discharged too much, it causes my starting battery to quickly dump it's nice full charge into my poorly charged aux battery. This "equalization" lowers the voltage of the whole system enough to turn off my separator so the alternator can bring the starting battery back to full charge. At this point the system reconnects and the process starts again.

I have noticed that my separator does not cycle if I only have a small discharge on my battery, like 12.4 v or more. I was wondering if others have this cycling occur with a certain point of discharge on their aux battery or if this occurrence is not normal at any state of discharge.

[MarkBC]

...How much battery storage do you have?

 

I have a bank of two of these: Trojan SCS225 .

 

...I guess my thinking is that when my auxiliary battery gets discharged too much, it causes my starting battery to quickly dump it's nice full charge into my poorly charged aux battery. This "equalization" lowers the voltage of the whole system enough to turn off my separator so the alternator can bring the starting battery back to full charge. At this point the system reconnects and the process starts again....

 

OK, got it -- I understand now.

And I know that I don't know enough about how it works to make a worthwhile suggestion.

But if I was to make a wild guess then if what you think is happening really is happening, then maybe the problem is on the truck side -- battery or alternator.

[Ethergore]

Markbc- thanks again for the help. Where do you have your batteries if they have to vent?