My experience and difficulties with 12v power

Good Afternoon,

I felt like posting for a few reasons after some difficult experiences with my new 2 way fridge and solar panels.

My current system contains:
-2001 toyota tundra with a 100 amp alternator
-2009 Hawk
-75 amp hour Die Hard AGM with dual terminals
-Sure 1314a separator
-100 watt Renogy flexible solar panel remotely mounted (ie not mount to the roof)
-30 amp charge controller with LCD display

This system needs to power:
-Water pump
-Norcold fridge with Danfoss compressor (3 amp draw) rated to run 50% at 80 degrees
-LED lights
-Misc 12 volt stuff (negligible)

So my problem happened in the following scenario.
-Left home fully charged and fridge pre cooled (measured 12.8 volts after sitting 2 hours)
-Drove from 12 pm to 6 pm and parked
-I woke up the next morning at 6 am with 12 volts (ie less than 50% charge)
-Drove from 7 am until 5 pm doing mostly off roading with the AC on
-Arrived at destination with 12.2% (IE 50% charged)


Obviously my battery would be damaged if I left my refrigerator running on a 50% charged battery overnight so I turned my truck on and let it idle. What I noticed is that my separator was turning off and on. I checked with my multimeter and the separator was doing what it was supposed to (turning on at 13.2 and off at 12.8 v).

The lesson I learned was that my deeply discharged battery is unable to be charged with the separator in line because the voltage will drop low enough to let the separator turn off.

What I ended up doing is bypassing the separator so that both batteries were combined and let the truck idle for 4 hours to get to a charge of 12.7v. The next day when I woke up the battery was down to 12.2v so after starting the truck I again bypassed the separator and drove most of the day off road. This time when I arrived at my destination my battery was at about 12.7 with a surface charge.


So from what I have read, this is not abnormal behavior. I have noticed people with similar setups but I am assuming that maybe they don't have a problem because they are not driving as much and their system is fully charged when the sun sets.

I know some may recommend I get more storage (battery) but if my system is fully charged when the sun sets I am able to start the day with a battery that is less than 50% discharged.

So it seems like there are a few solutions I can think of to my situation.

1) Get a DC to DC charger to charge my aux battery with the correct voltage

2) Permanently mount my solar panel so I am always getting a charge at the correct voltage (except without sun)

3) Use a solenoid to connect batteries at startup



Number 1 seems like it will work if I am driving all day but what if Im in town and stop to eat and sight see regularly. I still need to power my fridge and cant put out portable solar as it may get stolen.

Number 3 seems like it should work and is basically what I did to get through my last trip but knowing the voltage is that low should I be concerned about low voltage problems within my vehicle? Also, I still have the problem of not driving enough during the day.

Number 2 seems like the best option since I will always have charge during the day and hopefully always have a fully charged system when night comes (assuming there is good to moderate sun). The only problem is if I stay parked stationary in the shade. But I guess I can at least buy another panel for this situation which is still cheaper than a dc to dc charger.

What does everyone think and what is everyone's experience with this? Am I understanding everything correctly or am I missing something?

Thanks?

It could be the truck battery is weak and not taking a full charge causing the separator to cycle more than normal.
The fridge may also be using more amps than the manufactures rating, you will need a logging amp meter to check your current draw over time.
Mount the solar panel on the roof for a while, and see how much difference you have in your recharge.

Dsrtrat

If your charge line to the house battery is to small a wire size it will cause a voltage drop which will affect charging. With the truck running check to see what the voltage is at the house battery. You might want to consider a larger battery bank, if you get into rainy weather or heavy cloud cover sometime with no sun for 2 or 3 days you will need it..

Sounds like you need to know what your demands on the house battery truly are. I can recommend the Bogart Engineering Tri-Metric. It is not the least expensive option. Others will likely recommend the "Watts Up" meter sourced form Amazon. Either way you'll be able to see what the demands on the battery are, and by pulling fuses and turning things on and off you'll be able to determine what each load really is.

What I'm hearing makes me think that you may have a load that you don't know about, though if the house battery has been treated this way for too long it may be weak and need to be replaced.

With all LED lights and rarely running out 3-way off the batteries (except when driving) the roof-mounted 100W panel & 15A PWM controller that I added have had no trouble keeping the camper batteries up. I really don't expect that a 2-way fridge (I'm really, really tired of the 3-way's unpredictability) will tax the system.

dsrtrat said:

It could be the truck battery is weak and not taking a full charge causing the separator to cycle more than normal.
The fridge may also be using more amps than the manufactures rating, you will need a logging amp meter to check your current draw over time.
Mount the solar panel on the roof for a while, and see how much difference you have in your recharge.

Dsrtrat

Click to expand...

I thought about the starting battery being low. It tests between 12.5 and 12.6 after sitting all night. From what I read that's normal for a wet battery unless I don't understand correctly. I thought about maybe getting an AGM starting battery but it seems like an expensive attempt at a dilution.

Beach said:

If your charge line to the house battery is to small a wire size it will cause a voltage drop which will affect charging. With the truck running check to see what the voltage is at the house battery. You might want to consider a larger battery bank, if you get into rainy weather or heavy cloud cover sometime with no sun for 2 or 3 days you will need it..

Click to expand...

I thought about this too. I checked the voltage from the starting battery all the way back to the aux battery at each point. They all read the same voltage which was 13.5 at the time. No drop down to the 0.1.

I do plan on getting more storage but I'm waiting until I have enough money to get two 6 volts and rebuild my cabinets to fit them. With that said, that won't fix my recharging problem if I do run then down to 50% like I do now.

For now I drive most of the time on trips and if my alt would charge me up I would be OK if there was rain or cloud.

ntsqd said:

Sounds like you need to know what your demands on the house battery truly are. I can recommend the Bogart Engineering Tri-Metric. It is not the least expensive option. Others will likely recommend the "Watts Up" meter sourced form Amazon. Either way you'll be able to see what the demands on the battery are, and by pulling fuses and turning things on and off you'll be able to determine what each load really is.

What I'm hearing makes me think that you may have a load that you don't know about, though if the house battery has been treated this way for too long it may be weak and need to be replaced.

With all LED lights and rarely running out 3-way off the batteries (except when driving) the roof-mounted 100W panel & 15A PWM controller that I added have had no trouble keeping the camper batteries up. I really don't expect that a 2-way fridge (I'm really, really tired of the 3-way's unpredictability) will tax the system.

Click to expand...

I would love to get one but can't afford it at the moment. Despite not knowing my exact draw, I do know I draw less than 50% over a long night in 90 degree weather. I tested it out in my driveway from full charge. So basically, my capacity should be sufficient if I can have my system fully charged when night falls.

I plan to achieve this with my solar for now but from the replies I'm getting from everybody maybe what I'm experiencing is not normal.

From reading other forums many people say they don't get more than an 80-85% charge on their aux battery from their alternator. Is anyone else running a 2 way fridge on just their alternator and their aux battery without problems?

I feel my problem is that I can't get my battery fully charged before night and then I wake up with less than 50% charge and the alternator can't recover. Anyone agree or disagree? Any more ideas to try?

Ntsqd- also I made sure I don't have a random draw by hitting the kill switch and checking the voltage then turning it back on with everything turned off. I got no change in voltage even with out being able to turn off my co detector.

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.

camelracer said:

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.

Click to expand...

I was afraid I would hear this. I'll look into diagnosing the alt then. The only thing I tried so far was to see if the voltage to the aux battery or starting battery increased when held at 2500 RPM. It didn't, so maybe thats my problem. Its funny because I've been working on my own cars for years and have never had to diagnose an alt problem. Guess there is always a first.

Now that you said this is not normal behavior, I am also wondering if my separator is my problem. I have also had my Hawk on a 2004 Dodge diesel and the separator would cycle pretty often but would still eventually charge my battery. Only, back then, I didn't have the fridge. I guess I will try bypassing the separator and checking voltage as well.

Thanks for the lead!

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

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'.

Ethergore said:

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

Click to expand...

camelracer said:

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.

Click to expand...

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.

LAWNMOWERMAN said:

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

Click to expand...

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.

DesertDave said:

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'.

Click to expand...

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?

MarkBC said:

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.

Click to expand...

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.

Ethergore said:

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

Click to expand...

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)

MarkBC said:

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)

Click to expand...

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.

Ethergore said:

...How much battery storage do you have?

Click to expand...

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....

Click to expand...

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.

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