National Luna Split-Charge System Charging Issues?

dwh

Tail-End Charlie
I am curious about this system, wondering if for some reason that there might be a millisecond of voltage reduction that would trigger the IS to drop out.

Hrmm... I don't know anything about that charging system, but just looking at this theory...

I would think it probably shouldn't matter. Even if the alternator cut out briefly, the battery should still hold the bus voltage up high enough to prevent a disconnect...certainly for an extremely short cut out in the milliseconds.

For the theory to work, there would have to be both a momentary drop in alternator output, *and* a simultaneous high load on the bus to bring the voltage down.


Can anyone point me to any docs on the net that describe the functionality of that system?
 

dwh

Tail-End Charlie
For the theory to work, there would have to be both a momentary drop in alternator output, *and* a simultaneous high load on the bus to bring the voltage down.

Thinking about it a bit more...

I have my doubts that any modern high-tech computer controlled voltage regulator is going to let the bus voltage fall that far (12.7v) before it energizes the field coil in the alternator.
 

Equipt

Supporting Sponsor Presenting Sponsor of Overland
The more I think about it, the more I agree with you. It logically just doesn't make sense for it to act in that fashion, and the battery voltage itself would sustain a higher voltage over a span of milliseconds. So much for that idea.

The comments made so far about charging batteries have been enlightening. I hadn't researched these batteries to this extent. I am more the mind to install the best battery I know, let the vehicle charge them both while on the road, and when a battery starts to fail 4-5 year down the road I replace it. A $250 battery used over 5 years is $50 a year. Money well spent. And in that time, using the NL system and the Platinum batteries, not once have I ever been stranded because of my batteries. I haven't been stranded, period. Knock on wood. That includes several month stints to Central America and Baja, a run to Alaska and back, even a 120 degree southern Utah 4+ trail guide run with 2 fridges and video camera charging around the clock. With the accessories on the aux battery, the main is charged. Even with issues charging the aux, the main is charged. It's great to know all this, so if something does happen you can rely on your knowledge to get you home.

The NL system is designed to set off an audible and visual alarm if the voltage input goes above 14.7V. It considers a voltage above 14.7V to be damaging to the electrical system of the vehicle and wants to alert the user of a possible voltage regulator issue with the Alternator. Trucks are getting smarter, and now there are variable voltage output alternator systems. The LR4 is one of these, as are others. On cold mornings they will ramp up the output to get the vehicle to running/interior temperature quicker. So be it, as long as the situation is known, and you an silence the alarm it will work just fine. But I don't believe vehicle manufacturers at large are building their vehicles to put out a voltage higher than 14.7V. So my question would be, why would Odyssey/Platinum create a battery that requires such a high charge rate when they know the vehicles the batteries are being put in will not be able to provide that? It doesn't make sense they would. I could be wrong here, but it doesn't seem like a smart long term business plan to do so.

Just my 2 cents.
 

dwh

Tail-End Charlie
Yea, I've been trying to figure out a way that it could happen.

Best I can come up with is if the charging system had both a float mode and temperature compensation. I could maybe see it if was doing something goofy like floating at 13.2v and then applying a temp compensation factor to lower the voltage even more. I guess something like that could possibly let the bus drop to 12.7v.

Seems highly unlikely though.
 

dstock

Explorer
I agree with your sentiments Paul, and that is my main concern, that I do not want to be stranded somewhere. I'm also not trying to be an alarmist, but the sudden drop in resting rate had me concerned, being that I live in SoCal and it doesn't really get cold here. As long as it does not continue to drop, I will probably let it ride for a bit and just keep monitoring it to see what happens. 4-5 years battery life is fine by me also, 2-3 however is not. It seems with all the information on batteries this has brought to light, most if not all of the popular AGM batteries will likely have the same issue.
I brought the same point up in the "other" battery thread, why are they marketing these batteries to us when they know hardly any vehicle can maintain them? Just to sell us chargers too?

Anyway, thanks for your all your input on the matter. I will update this thread if anything changes.
 

DiploStrat

Expedition Leader
Fools Rush In ...e

where Angelsfear to tread. That said, here goes. :)

I run a system that is very similar to the National Luna, that is, I use an an intelligent voltage sensing controller (A Magnum SBC) to open and close a 200A Blue Sea relay. While each manufacture will claim various advantages to their approach, e.g., the National Luna incorporates a timer, they are all basically the same. All can work well, all can fail. It would appear that National Luna may have some heat sensitivity, but that is a quality control issue and does not argue against the approach. The only weakness that I can see in the National Luna unit is that it cannot handle the higher amperages that I have.

A lot of the OP's questions come close to mixing apples and oranges. And some of the comments slightly confuse voltage and amperage issues. As noted by dwh, Page 6 of the Odyssey manual contains the most critical information. (And, should you want to explore this more deeply, Handy Bob explores all of this very well for the amateur, like me: https://handybobsolar.wordpress.com )

Starter Battery: This is generally easy as this battery is not normally deeply discharged and you generally drive long enough to recharge it. Modern electrical systems are much better at keeping the voltages and amperages high, even at idle. It is worth noting that the National Luna system, if installed according to the instructions, has absolutely no/no impact on this system. If your starter battery is not charging, the National Luna is not the cause. (Or the cure, for that matter.)

Auxiliary Battery Combine: Fairly simple, the batteries will combine whenever the starter battery voltage exceeds a programmed voltage (13v) and a 5 minute countdown is satisfied. These conditions met, the batteries will remain connected until the system voltage drops below 12.7v. (My system works the same way, but lacks the 5 minute timer and I have the disconnect voltage set closer to 12.5v) The 13v connect voltage was selected as it is higher than the normal "full charge" voltage of 12.7v. That is, it is highly unlikely that any battery will exceed 13v unless it is on charge. Once the starter battery is over 13v, then the relay closes and the alternator charges both batteries.

Auxiliary Battery Charge: This is where things get interesting. The National Luna instructions have some very good passages (labelled "Before Installation") about the challenges of charging a deeply discharged second battery. If, as noted, recharging a starter battery is easy, an auxiliary battery (aka "house", "camper", or "domestic" battery) is harder because:

-- The degree of discharge may be greater, that is, instead of using 5 - 10 Ah to start your vehicle, you may be looking at 50 to 150 Ah overnight for your refrigerator, or whatever. In freezing weather, I use about 55Ah to run the heat, refrigerator, lights, composting toilet, etc.)
-- This means that you need to replace more ampere hours. (Depending on whom you believe, between 100 and 150% of what you have used.)
-- This requires a longer charge period, perhaps by an order of magnitude.
-- There may also be voltage losses due to longer cable runs.

The big problem is that many people simply don't drive long enough to fully recharge a badly discharged auxiliary battery.

How charged is Charged? There is a lot of mojo going around about the magic of 14 vs. 14.2 vs. 15v. It really isn't that hard.

-- For the fastest possible charge, you want the highest possible voltage that does not cause the battery to overheat and spew acid. For open cells, this can be a bit higher as you can easily replace lost moisture. For sealed or valve vented batteries the voltage is a bit lower because any moisture lost cannot be recouped. For this reason, most AGM manufacturers call for a voltage of somewhere near the "magical" 14.2v. This being high enough for a fast charge and (hopefully) low enough to avoid any risk of popping the vents. Note, however, that this is at 25C (77F). Warmer and the voltage required drops, colder and it rises.

-- To get past surface charge you need the longest possible charge, the absorb/acceptance stage.

-- What happens if your charger can't reach the magic number, in this case 14.7v @ 25C? Not much, the charge simply takes longer. Same thing happens if your charger cannot supply as much current (amperage) as your battery can take. Remember, while "full" charge is described as being 12.7v, that is 12.7v when NOT on charge. When connected to a charger, the voltage will quickly rise to over 13v and will probably be at over 14v for most of the charge cycle. "Full" charge to a charger means that the battery will no longer accept current (amperage) at greater than a specified rate - it is not determined by the voltage. Once that happens, most intelligent chargers will drop the voltage back to a float voltage, somewhere between 13 and 14v.

Battery charging is a chemical reaction and thus metaphors of water flowing or using air to inflate tires can be helpful, but they are not exact. That said, here goes: Two batteries can be likened to to containers of water with a pipe between them. Water seeks its own level, thus water will flow between the two containers until the reach the same level. That level can be likened to voltage. The rate of flow is determined by the difference in level (voltage) and the rate of flow (average) is determined by the size of the pipe, or in our case, wire. The flow is greatest when the difference in level (voltage) is greatest and slows as the levels approach equilibrium. All of this technobabble simply means that two batteries connected together will eventually reach the same voltage. The speed with which the reach the common level is determined by the difference and the size of the connection.

Sooo, could a badly discharged second battery draw down the starter battery? Perhaps, but not likely as the National Luna should break the connection between the two batteries whenever the voltage of either battery drops below "full" charge, that is 12.7v.

So how do you get a large second battery (in my case 600ah) to "full" charge? You rely on the engine alternator to provide the bulk (high amp) charge and on a solar kit or shore power to complete the job. Depending on your engine alternator and the distance you drive, every day, I suspect that you would be hard pressed to recoup more than about 50Ah in typical use.

Bottom line, assuming that you are fully charging your batteries, excessive drop in resting voltage indicates a problem with the battery, not the charger. The first task is thus to assure that your vehicle's charging system is up to the task and that has nothing to do with your National Luna controller/relay.

Hope this is helpful and I hope there are not too many silly misteaks in speling and logic.

 
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dwh

Tail-End Charlie
Evildeadgroovy.jpg





I got a couple of hairs to split. :)




For this reason, most AGM manufacturers call for a voltage of somewhere near the "magical" 14.2v.


Typo eh? Prolly should say 14.4v?



The rate of flow is determined by the difference in level (voltage) and the rate of flow (average) is determined by the size of the pipe, or in our case, wire. [snip] The speed with which the reach the common level is determined by the difference and the size of the connection.

And the internal resistance of the batteries.



Sooo, could a badly discharged second battery draw down the starter battery? Perhaps, but not likely as the National Luna should break the connection between the two batteries whenever the voltage of either battery drops below "full" charge, that is 12.7v.


I just learned on this thread, that the NL actually only monitors the cranking battery voltage to make decisions. I thought it did "either side" but I guess not.
 
Why 14.7 volts ???? Had to go back and refresh my memory. Page 16 of the Tech Manual describes the impact of raising charging voltage from 14.2 to 14.7 volts, again for deep cycling applications. In their words, "The message to be taken from this graph is clear – in deep cycling applications it is important to have the charge voltage set at 14.4 – 15.0V. A nominal setting of 14.7V is a good choice, as shown by the test results."

My focus on 14.7 volts absorption, 13.6 float and them living above 12.84 volts has always been in the context of maximum life (and as it relates to deep cycling) and that still holds true. So, in reading the entire section on Charging Odyssey Batteries, you will find a lot of latitude for charging (absorption) voltages. As the TM states, 14.7 volts is a good choice (and not a REQUIRED choice). But not only is it a good choice, it is THEIR choice for absorption voltage to obtain maximum life. It is the voltage that their Ultimizers are set to deliver in absorption stage and the voltage that is shown on their charge profiles. In my posts, while I erred with statements like 14.7v being needed to overcome internal battery resistance, I stand corrected. I may be wrong on a few other statements as well. I also stated not to rely on my word but to consult Odyssey, as I could be wrong.

For those of you who are not interested in obtaining maximum life of the Odyssey battery but still want to stay with them, you obviously have greater lattitude in charging them and will likely be happy with replacing them more frequently. That is now closer to a personal choice based on what you know about them and not something that comes as a surprise to you when they fail.

I still recommend consultation with Odyssey on the 14.7 volt issue and before buying the Ultimizer for use in conjunction with the Platinums in the NL system, unless of course replacing them more frequently is satisfactory or the decision is to go to something else.
 
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dwh

Tail-End Charlie
Hey DiploStrat,

Can you give me a link to the specs on your truck's charging system again? The details are vague in my memory and I'm betting the Jeep system is probably very similar.
 

KellyM

Adventurer
I have a very similar system to dstock. I have two Deka AGM Deep cycle 34M batteries that are less than a year old in a 2013 JKUR with a NL dual battery split charger kit. I have an ARB fridge, lights and a few power outlets tied into the aux battery. As dstock mentioned, my system stops charging the aux. battery after about 20 - 40 minutes and I can not override the controller to manually connect both batteries. I also have been seeing both batteries settling to 12.2-12.3 overnight after getting a charge from the alternator while driving. The aux battery typically continues to drop over several days as mine is not a daily driver. However, my main concern is figuring out why my charge system is disconnecting the aux battery after a relatively short period of drive time. I am far from proficient in this area, but I suspect that the repeated occurrence of discharge without full recharge has damaged the aux battery which is why I quickly show the relatively low voltage on the NL battery monitor for the aux battery even without any accessories live.


I would be fine getting new batteries once the system is operating correctly and even adding solar if necessary to assist in charging the aux battery to run the fridge when remote for multiple days, but I first want to get the system to the point where the alternator will provide a (mostly) full charge to both batteries while the Jeep is running.


Paul - thanks for joining the discussion. I won't be able to check the thread much over the next few weeks because of work commitments, but I would like to explore my options with you at some point.


Thanks in advance for the assistance.



Kelly


P.S. my wife has informed me that the fridge is the most important mod to the Jeep, so I need to fix this soon.
 

dstock

Explorer
Dug up my receipts for the Platinums and they are less than 2 years old, so I called Sears, told them about the resting voltage and they said "bring them in". Will be doing just that this weekend, will report back how it goes.
 

dwh

Tail-End Charlie
As dstock mentioned, my system stops charging the aux. battery after about 20 - 40 minutes and I can not override the controller to manually connect both batteries.

There is an interesting thead I found here:

http://www.jkowners.com/forum/showthread.php?t=82078

Which supplies some information about how the Jeep's system works.


The upshot of that thread is that there was a grounding issue, which, due to the way the system operates, caused a severe over-voltage.

From what I gather here, the problem with NL seems to happen more with Jeeps.

So what I'm thinking about what you just described, is that the NL is disconnecting because the Jeep's charging system in raising the voltage up over 14.7v and keeping it there.

Why that would be happening - if indeed it is - after driving for a while...

Well, it's probably that that's simply how long it's taking for the charging system to bring the aux battery up to a surface charge that high. In other words, the (relatively) low aux battery is drawing down the bus voltage, the charging system is keeping the alternator turned on to try and achieve whatever it's trying to achieve, and it takes, as you described, 20-40 minutes for the aux battery to get there.

Okay, that's all well and good and is normal behavior. The odd behavior would be that the charging system is not backing off and is keeping the bus voltage very high, and this is why the NL won't reconnect.


So then the questions would be, A) IS it holding a high voltage, and B) Why?

I'd first want to see real no-BS voltage measurements while driving. (I've done that before by taking a length of cut up extension cord and running it from the battery into the vehicle and then hooking up a multi-meter and setting it on the dash and watching it all day while I drove.)


If it really is holding a voltage over 14.7v, then the effect would that the main battery is (possibly) being overcharged, and the aux is (certainly) being undercharged.


Then the next question would be why is it doing that, and according to the thread linked above, that could likely be a grounding issue which is confusing the computer.
 

dstock

Explorer
dwh,

While that is in interesting thread, I don't believe over-voltage to be the issue.

The DBC on the NL system has an over-voltage alarm for the main battery. This has never gone off. Also, I have looked to see what my voltage gauge is showing at the time I was having the high heat dis-engage and it was still within normal 14-14.3 parameters.
 

dwh

Tail-End Charlie
dwh,

While that is in interesting thread, I don't believe over-voltage to be the issue.

The DBC on the NL system has an over-voltage alarm for the main battery. This has never gone off.


Ahh. Now that you mention it...I do recall that being mentioned in another post.


Also, I have looked to see what my voltage gauge is showing at the time I was having the high heat dis-engage and it was still within normal 14-14.3 parameters.

What gauge was that? In that thread I linked someone said the factory gauge was rigged to lie for some reason. (Just curious and still trying to figure out the Jeep system. If the NL has an overvoltage alarm, that's a pretty good indicator that that isnt the problem (provided the alarm is actually working of course).)
 

dstock

Explorer
There would have to be a factory gauge for it to lie.
I use an aeroforce gauge which pulls info from the obd2 port. The gauge has always matched what I get with a multi meter so I don't believe it is lying either.
 

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