Dual Battery Shore Power Charging Question

[1Louder]

Weekend Report:

Solar worked great. My 60 watt panel can for sure keep my trailer battery charged up with very little effort. However, on my vehicle it was a bit harder to tell. My National Luna controller is NOT working properly. It is allowing power to drain from both batteries and not isolating them as it should. From what I can tell the batteries are trying to level themselves to the same voltage as many have described. So until I can fix this issue, maybe it is the solenoid itself I can't test my solar properly. When I hooked up the panel to the 2nd battery you can see it charging that only. When I hook it up to the main battery when sun light was strong you could see the controller go through its normal sequence (start a timer, and then connect the batteries for charging) but typically that didn't last long. Only a few minutes. I have read the lengthy albeit a bit old thread on National Luna problems. Replacing the solenoid is a cheap possible solution. If anyone has experienced the National Luna system not separating the batteries when a charge in not applied please let me know.

In the end solar is the way to go and if I can get the controller to work properly I likely will put the solar panel on the main battery and let the controller do its thing.

 

[dstock]

I have my 100 watt solar panel connected to the Aux battery as that is where all my loads are connected. The main battery is left alone for vehicle starting duties. I had the opposite problem with the NL solenoid where it would separate the batteries at some point even though a charge was being supplied, thus my Aux battery would not get charged. This seemed to be a heat related issue and would mostly occur when ambient temps rose.

I switched to a BlueSeaACR and everything now works as it should. In addition, enough power coming from the solar panel to the Aux battery will trigger the BlueSea ACR to combine both batteries and then my main battery get charged as well. I also have the option of manually separating the batteries with a switch if I only want to charge the Aux battery.

I think the solenoid is the weak link in the NL, even after the unit was swapped the same problem occurred with the new one. I got tired of messing with it so I moved on to the BlueSea ACR.

YMMV

 

[1Louder]

I have my 100 watt solar panel connected to the Aux battery as that is where all my loads are connected. The main battery is left alone for vehicle starting duties. I had the opposite problem with the NL solenoid where it would separate the batteries at some point even though a charge was being supplied, thus my Aux battery would not get charged. This seemed to be a heat related issue and would mostly occur when ambient temps rose.

I switched to a BlueSeaACR and everything now works as it should. In addition, enough power coming from the solar panel to the Aux battery will trigger the BlueSea ACR to combine both batteries and then my main battery get charged as well. I also have the option of manually separating the batteries with a switch if I only want to charge the Aux battery.

I think the solenoid is the weak link in the NL, even after the unit was swapped the same problem occurred with the new one. I got tired of messing with it so I moved on to the BlueSea ACR.

YMMV

It was not hot on this trip. I am going to replace the solenoid and see what happens. Is this what you purchased? https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A or this one... https://www.bluesea.com/products/76...rging_Relay_with_Manual_Control_-_12V_DC_500A or something else!

Thanks,
Chris

On a side not for future purchasers I have heard more complaints about the NL system than others. A friend has the IBS Unit and has had no issues.

 

[dstock]

It was not hot on this trip. I am going to replace the solenoid and see what happens. Is this what you purchased? https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A or this one... https://www.bluesea.com/products/76...rging_Relay_with_Manual_Control_-_12V_DC_500A or something else!

Thanks,
Chris

On a side not for future purchasers I have heard more complaints about the NL system than others. A friend has the IBS Unit and has had no issues.

I went with the 500 amp version, the second link you posted, my Jeep alternator is rated at 160 amps, didn't want to take any chances after the NL issues.

 

[1Louder]

I went with the 500 amp version, the second link you posted, my Jeep alternator is rated at 160 amps, didn't want to take any chances after the NL issues.

Ok thanks for the report. Hopefully I don't have to replace mine but will budget for this.....

- Chris

 

[1Louder]

I installed a new solenoid for my National Luna controller. We will see if this fixes my issue with my starter battery draining. Both batteries are on a long charge now. I will throw my fridge in and see what happens tomorrow while I am away at work. I have so much crap under my hood with 2 batteries, etc that I am having trouble finding a place to install the solenoid to cut the power to my trailer with the ignition off. If I was to do all of this over again I would likely ditch the dual battery setup and get a nice solar setup along with one of those small battery jumpstart boxes. Then again I may just end up ditching the National Luna and going with what Bluesea has to offer. Worst case I move my 2nd battery to my trailer and find an easy way to plug my fridge into that while camping.

Again thanks for all of the info and feedback from everyone. It's a great topic.

 

[1Louder]

My solenoid was bad on my National Luna controller. I am still having loss of voltage on my main battery. I'm pretty sure it's the battery and not anything in the system so when I get a chance I will disconnect the battery after being charged and see what happens after 12 hours if possible.

 

[1Louder]

Another weekend another saga ha ha... The mount for my 2nd battery failed. Everything was still hooked up but it may have caused some charging issues. No idea. Long story short it had to be removed for the time being. 6 hours of driving along with my trailer in tow and according to the NL controller the voltage was low. 12.4 on the main battery and 12.5 on the 2nd battery. In 65 degree temps and 8 hours later the 2nd battery was down to 12.2 and main battery 12.1. No idea why. Only thing running was my fridge. Yes I know they can draw a fair amount of power but it shouldn't have been running that often.

So everything is now on my PM-1 with no 2nd/House battery. We will see what happens. Hard to test things at home when it is still 8000 degrees in Phoenix. Not a fair test when the car is 120+ and trying to keep a fridge at 38 degrees. If I see unreasonable voltage drops on the main battery with all accessories off I will swap the PM-1 out for the Optima Yellow Top and see what happens.

After all of this I am really leaning towards a single battery in my truck. Maybe 2 in the trailer and relying on my Solar panel for longer multi-day trips in a single camp site. I can say I am not really impressed with the National Luna system. It never reads accurate voltage. The connection to the controller is horrible and that is a common complaint. It's been 1.5 years since I installed the dual battery setup although the current 2nd battery is only 3 months old and the other was new at the time of install. Now solar is much cheaper and getting more powerful. I know they are not equal and there are many variables to decide what each person needs. 99% of the trips I do are with groups. So if I ever have a battery problem I could get a jump from my little jumpbox or someone else. I don't have a winch so for now I probably don't need this setup.

 

[Ducky's Dad]

Not a fair test when the car is 120+ and trying to keep a fridge at 38 degrees.

I was in the desert east of Yuma for most of the first two weeks in September, and daytime highs averaged around 111F, with the highest day at 128F (two separate thermometers). Had an Indel B fridge in the back seat of the truck hooked to a pair of new Optima G34 Blue dual purpose batteries, with the fridge set to max cold as a freezer. It would run for about 38 hours on those two batteries before the batteries needed to be recharged, and the fridge got down to as low as -21C in the mornings, with overnight ambient lows around 80F.

according to the NL controller the voltage was low

I don't have a Nat Luna controller but I do have Nat Luna monitors on all three batteries. I checked the battery voltages with a multimeter and the Nat Luna monitors in the cab read about 0.1V lower than the meter on the battery post shows. That's about right for voltage drop and close enough for practical purposes.

So everything is now on my PM-1 with no 2nd/House battery.

That will probably cause long term problems with sulfation on the PM-1 and kill the battery prematurely, unless you use an approved conditioning charger on that battery.

If I see unreasonable voltage drops on the main battery with all accessories off I will swap the PM-1 out for the Optima Yellow Top and see what happens.

If the Optima yellow is the common G34, it has only about 60% of the amp hour capacity of a PM-1 that is in good condition. "Good condition" is often a foreign concept with the PM-1, unless you are scrupulous about maintenance.

 

[DiploStrat]

… 6 hours of driving along with my trailer in tow and according to the NL controller the voltage was low. 12.4 on the main battery and 12.5 on the 2nd battery. …

You need to do some work to establish your baselines, otherwise we are all guessing in the dark.

-- What is the output voltage of your vehicle? Updating myself, I am guessing that it should be about 13.9v with the engine running. That is low (as noted by Ducky's Dad), but usable if you top up periodically from shore power.)

-- What is the gauge/length of the cabling from your starter battery, through the relay, to your second battery? I suspect that it may be way too small.

-- What is the voltage measured at the camper battery's terminals with the engine running and the relay closed? If it is not well over 13.5v, then you can drive all day and you are not going to do much good for a battery that wants to peak at about 14.7v. A clamp on ammeter will also give you some interesting numbers; you want to see at least 50A when the camper battery is discharged and first put on charge.

Naturally, one assumes that all of your connections are good, brackets tight, etc.

I would take these readings with a proper hand held meter, rather than rely on the National Luna meters. You can make all of this work and easily, but you do have to proceed step by step. You may, indeed, want to replace the National Luna unit with a Blue Sea ACR or some other product, but unless your wiring is correct and your alternator putting out its full voltage and amperage, it will make little difference - a relay is a relay as long as it is big enough.

Good luck.

 

[AndrewP]

Louder-Is your alternator charging at all? While driving, your batteries should read 14 volts. I don't entirely understand your set up but I'll look back through the thread and see exactly what you have set up. It sounds to me you need to get rid of the NL set up.

Diplo suggested the most important test you should do way back in this thread. You need to start your truck, and measure the voltage with a good voltmeter at your main (engine) battery terminals. It sounds like you are assuming your scan gauge is showing you that, but that isn't always the case. If you aren't showing 14v right there, then you have a problem somewhere between your alternator and your battery. It could be wiring, corroded terminals etc.

But with that said, from reading threads like this, the National Luna dual battery systems sounds like one to avoid. Does everything work properly with it removed from the truck?

Could you post a pic of your wiring?

 

[1Louder]

I was in the desert east of Yuma for most of the first two weeks in September, and daytime highs averaged around 111F, with the highest day at 128F (two separate thermometers). Had an Indel B fridge in the back seat of the truck hooked to a pair of new Optima G34 Blue dual purpose batteries, with the fridge set to max cold as a freezer. It would run for about 38 hours on those two batteries before the batteries needed to be recharged, and the fridge got down to as low as -21C in the mornings, with overnight ambient lows around 80F.


I don't have a Nat Luna controller but I do have Nat Luna monitors on all three batteries. I checked the battery voltages with a multimeter and the Nat Luna monitors in the cab read about 0.1V lower than the meter on the battery post shows. That's about right for voltage drop and close enough for practical purposes.


That will probably cause long term problems with sulfation on the PM-1 and kill the battery prematurely, unless you use an approved conditioning charger on that battery.


If the Optima yellow is the common G34, it has only about 60% of the amp hour capacity of a PM-1 that is in good condition. "Good condition" is often a foreign concept with the PM-1, unless you are scrupulous about maintenance.

When everything was working properly and camping at cooler temperatures there was not a significant voltage drop. In my 100+ degree garage and driveway I brought the Optima battery down to the point of the fridge shutting off in around 12 hours. I can't remember the exact time frame and there were a few tests with my solar panel and a quick drive in between.

I totally agree that the PM-1 has more reserve than the Yellow Top. I would only swap to see if I am having an issue with the battery itself. Like it can't hold a charge. Not a long term solution. I have a conditioning charger from Noco the G3500. Not on Odysseys official list. Also, based on that I should either swap the batteries around or put all the accessories on the main battery and just use the Yellow Top as a backup. Since I have to build a new mount if I am going to keep this setup I will take that under consideration. I have also thought about buying a standard starting battery and then leaving the PM-1 in as the house battery and not the main battery.

As for the differences between the NL and my volt meter in most instances it was .2 to .3 voltage difference. .1 I understand especially with rounding. But if my battery is at 12.4 (at the battery) and 12.1 on the controller well something seems to be a miss.

NOCO Genius UltraSafe Smart Battery Charger
by NOCO
Link: http://amzn.com/B004LWVEKS

Thanks!
Chris

 

[1Louder]

You need to do some work to establish your baselines, otherwise we are all guessing in the dark.

-- What is the output voltage of your vehicle? Updating myself, I am guessing that it should be about 13.9v with the engine running. That is low (as noted by Ducky's Dad), but usable if you top up periodically from shore power.)

Looking at my Ultragauge while driving it ranges from 13.8-13.9. I am pretty sure it is the same with my volt meter but I can start the engine and check. I will also check it with lights on and AC on etc.

-- What is the gauge/length of the cabling from your starter battery, through the relay, to your second battery? I suspect that it may be way too small.

It is 8 AWG. Purchased at a marine supply store in bulk. Length is shortest as possible I would say around 6ft. NL controller is on the sidewall about 1 foot from the firewall. Then the cables run along the firewall to the 2nd battery which is in the back left corner of the engine compartment. The main battery is front right. So the cables running to it are maybe 2.5 ft tops. With a breaker in between.

-- What is the voltage measured at the camper battery's terminals with the engine running and the relay closed? If it is not well over 13.5v, then you can drive all day and you are not going to do much good for a battery that wants to peak at about 14.7v. A clamp on ammeter will also give you some interesting numbers; you want to see at least 50A when the camper battery is discharged and first put on charge.

I will check this when I leave to run errands this morning. The battery is on my charger. It has been on there for about 18 hours and is showing 75% charge complete. Not sure if it will make it to 100% maintenance mode before I have to leave in a couple of hours. With the charger connected the there was 13.68 volts at the battery. Being a smart charger that may vary as it goes through the charging cycle.

Naturally, one assumes that all of your connections are good, brackets tight, etc.

I would take these readings with a proper hand held meter, rather than rely on the National Luna meters. You can make all of this work and easily, but you do have to proceed step by step. You may, indeed, want to replace the National Luna unit with a Blue Sea ACR or some other product, but unless your wiring is correct and your alternator putting out its full voltage and amperage, it will make little difference - a relay is a relay as long as it is big enough.

Good luck.

I don't rely on the NL readings. It just makes me mad when it shows the batteries super low like 11.8 volts and the battery is really at 12.1-12.3. This is without anything running like the fridge.

Thanks for all of the suggestions. Hopefully others can learn from this thread.

 

[DiploStrat]

Trying to push 100A through six feet of 8 AWG will give you a drop of .75v. This means that at high output your alternator is only delivering 13.1v to the camper battery, right around float voltage:http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=13.9&phase=dc&noofconductor=1&distance=6&distanceunit=feet&amperes=100&x=61&y=12 Not terrible, but your Toyota starts with a rather low voltage.

Assume a lower output of 50A and the numbers get better: http://www.calculator.net/voltage-d...ance=6&distanceunit=feet&amperes=50&x=39&y=15 Remember, voltage drop drops as the amperage decreases - which it will as the battery charges.

Were it me, I would run another 8 AWG wire in parallel over the entire system. With a 100A alternator, your charge rate won't remain that high, that long, but I would still want to harvest all I could.

Free advice is worth ...

 

[1Louder]

Louder-Is your alternator charging at all? While driving, your batteries should read 14 volts. I don't entirely understand your set up but I'll look back through the thread and see exactly what you have set up. It sounds to me you need to get rid of the NL set up.

Diplo suggested the most important test you should do way back in this thread. You need to start your truck, and measure the voltage with a good voltmeter at your main (engine) battery terminals. It sounds like you are assuming your scan gauge is showing you that, but that isn't always the case. If you aren't showing 14v right there, then you have a problem somewhere between your alternator and your battery. It could be wiring, corroded terminals etc.


Could you post a pic of your wiring?

From the original install when my engine compartment was fairly clean.

This gives you an idea of the setup. Some of the wiring was replaced because the run was too short as you can see in the picture. The mount was also moved to the right for better side clearance. All 8 AWG wire. That is also my old Optima battery. Current one is 3 months old.

To the right of the breaker you can barely see the NL system on the right side/fender wall.

Larger images can be seen here: https://flic.kr/s/aHsjEXVFgo

Does everything work properly with it removed from the truck?

Not sure what you mean here? I can say that the Optima Yellow top has been disconnected for 24 hours and is holding 12.52 volts.

On a side note here are the specs for both batteries:

Optima Group 34:
Performance Data
Cold Cranking Amps: 750
Cranking Amps: 870
Nominal Voltage: 12 volts
Open Circuit Voltage (fully charged): 13.1 volts
Internal Resistance (fully charged): 0.0028 ohms
Capacity: 55 Ah (C/20)
Reserve Capacity: BCI: 120 minutes (25 amp discharge, 80°F (26.7°C), to 10.5 volts cut-off)

Sears PM-1
Power Ratings:
Cold Cranking Amps (CCA at 0 deg.F):1150
Reserve Capacity (RC):205 min.
Amp Hours at 20 Hour Rate:100
Capacity Amp Hours at 10 Hour Rating:92