N. Luna Split Charge and a battery charger...

[nuclearmonkey]

So I'm trying to wrap my head around using a CTEK 7002 battery charger and the National Luna Split charge system. I'm running a 125 AH Lifeline as the house, and a 75 AH Deca as the starter. The CTEK is set to 'Normal' which has a bulk charge rate of 14.4 v. It should be noted that when plugging in the CTEK, the NL controller was reading that both batteries were at 100%.

So here's the question: After plugging in the CTEK, the NL controller showed the first two of the 4 green lights lit on the starter battery (13.2v). After the 5 minute timer, the solenoid opened, and the NL Controller continued to show both batteries at full, with the starter having the two green lights lit. After about 30 minutes, the house dropped from 100% (12.6) down to 12.5v. Still no 'charging lights' showing on the house side of the controller. I then used a multimeter to test the voltage coming through to the starter battery terminals (where the CTEK is hooked to), and its reading 13.5v.

So is it safe to assume that the starting battery - while showing full on the NL controller before hooking up to the CTEK really wasn't full, and when the solenoid opened it starting receiving a charger from both the CTEK, and the house battery? Secondly, I'm not quite sure why the multimeter is showing 13.5... I was expecting to see 14.4 from the 'Bulk' charge of the CTEK. Thoughts? For the record, the CTEK charges at 7amps

Thanks so much in advance!!

-Aaron

Update: 2.5 hrs in, both batteries are showing 2 green lights lit above each battery on the NL controller, voltage is showing 13.3 on the multimeter.

 

[DiploStrat]

Fools Rush In

Since no one else has taken a swing at this ...

First of all, I assume that you are simply misstating. The National Luna has a five minute delay (silly feature IMO) after which the relay is supposed to close, not open. See here: http://www.nationalluna.com/Datasheets/Intel Solenoid Instructions.pdf

If both batteries were, in fact, fully charged, that is a voltage of 12.7v or higher, the relay should have been closed; that is the batteries are connected together before you connected the charger. (They should remain connected until either battery drops below 12.6v or so.) I suspect, however, that unless you were running your engine or have a solar charger, the voltage was below 12.7v and the relay was open.

If you attach the CTEK charger to your starter battery it will go through its soft start and will probably start to charge, producing about 14.4v, depending on the profile selected. See: http://smartercharger.com/wp-content/uploads/2010/11/Multi-US-7002_us.pdf

If the National Luna relay is open, and it detects a voltage of 13.2v or higher, it starts its five minute delay and then closes. (Not clear what happens if it is already closed when it detects a rising voltage.)

The CTEK should keep charging until the charge rate drops enough to end the bulk and absorb charge stages, at which time it will reduce the voltage to its float setting of about 13.6v. It should hold the voltage at about that level indefinitely.

I would not place any reliance on the National Luna battery monitor readings, but would rather confirm the proper action of the relay and measure the battery voltages with your multimeter. If the relay is closing when it should, you should see the voltages of both batteries move towards the same level. (The speed at which this happens depending on the size of your wiring.) and, at the same time, the voltages of both batteries should rise to something approaching 14.4v and then, as they reach full charge, the voltages should drop to the float level of around 13.6v. Remember, your camper battery is twice the size of your starter battery. Logically, it will take longer to charge.

FWIW: The CTEK only charges at 7A. If you look at the guesstimated charge times in the CTEK manual you are looking at over twenty hours for a 150Ah battery.

Hope this is helpful. (And accurate.)

 

[nuclearmonkey]

Thanks for the reply!

So before I hooked up the CTEK, the batteries were showing full on the NL controller, but were definitely separated by the solenoid (the truck has been sitting for 3 days). When the NL sensed the increased voltage from the CTEK, it eventually (after the 5 minute period) linked the two together. So at this point, if let's say the house battery was drawn down to 50%, both of the batteries that are now linked will begin to equalize as they are receiving the charge from the CTEK (or alternator)? I guess that makes perfect sense considering they're now connected in parallel.

So the other question: is there a reason that during the bulk charge from the CTEK the multimeter was showing 13.2-13.5 v reading off of the battery? Shouldn't this be showing 14.4? (CTEK was set to 'normal' - so 14.4 during bulk). Is this indicative of a drain somewhere in the system?

FWIW, I checked on the system this morning... CTEK was at the 'float' stage, multimeter was showing 13.4 at the battery.

Thanks!

 

[DiploStrat]

So the other question: is there a reason that during the bulk charge from the CTEK the multimeter was showing 13.2-13.5 v reading off of the battery? Shouldn't this be showing 14.4? (CTEK was set to 'normal' - so 14.4 during bulk). Is this indicative of a drain somewhere in the system?

FWIW, I checked on the system this morning... CTEK was at the 'float' stage, multimeter was showing 13.4 at the battery.

CTEK makes nice stuff. Lifeline Batteries recommend CTEK chargers and if you go to your Audi dealer and buy a charger, it will be a CTEK. National Luna seems to have a mixed reputation, but it sounds as if your set up is working perfectly.

-- Truck sitting for three days. Depending on age of the batteries, background draws, etc., I would suspect that during that time one of the batteries dropped below 12.6v, so the relay should have opened.

-- You connect the CTEK, to either battery and, after the time delay, the voltage of that battery will begin to rise. How fast? Depends on the degree of discharge and it will be slowed by the fact that your CTEK is a very low powered charger.

-- Once the connected battery passes 13.2v (and there may be another time delay here), the relay will close. Now that 7A charger is looking at both of your batteries, some 200Ah of battery. Depending on the differing states of charge of the two batteries, one will seek to charge the other as the CTEK tries to charge both.

-- With only 7A available, I will take a long time, think hours, for the voltages to rise to the absorb level. The batteries themselves are the "drain" you are seeing. Once they do rise to the absorb voltage, 14.4v @ 25C, the CTEK will drop back to float voltage.

Again, from my distant perspective, that would appear to be exactly what you are seeing.

 

[nuclearmonkey]

Ok - so it's not very likely that I'm going to see the 14.4 from the multimeter if attached to the batteries when in bulk charge?... (I know, it must be like trying to explain calculus to a sheetrock wall - I promise, I'm not always this slow! :snorkel When I checked on the batteries this morning, they were already at the float stage, so the voltage is dropped by then anyway. I guess the real surprise for me was I was expecting the multimeter to show 14.4 at the batteries as if watching a flow meter of water filling up a jug. If the multimeter is simultaneously reading the draw from the batteries being charged, then that makes perfect sense. I guess I'm really just trying to make sure we don't have any ghosts in the system peeking out - the entire wiring (and there's a lot of gadgets) of the truck, as well as engine, etc is all brand new. Again, Thanks so much for taking the time to hash this out!!

-A

 

[DiploStrat]

Would need to know a bit more about alternator capacity, wiring size, type and age of truck. The other big question is your background loads. In my case, with a refrigerator and heat, my background drain is around 5A. But all of my chargers a capable of producing between 25 and 200A - a lot more than the 7A of your CTEK.

But basically the next time your batteries are reasonably discharged, watch the indicator lights on the CTEK and measure the voltages. It will take a lot of hours at only 7A, but the voltage should rise to 14.4v and stay there for the two - four hours of the absorb stage, before dropping to 13.6v (or so) for float.