Dual Battery Shore Power Charging Question

[1Louder]

I have the National Luna setup in my FJ. If I hook up a charger to the main battery the National Luna sees the charge and then distributes the charge to both batteries.

1. Is this a bad thing other than the charging process taking a lot longer?

2. Is there an easy way to prevent this besides disconnecting a battery from the system when I want to give it a good charge? I believe this only happens when charging the main battery but need to see how the NL reacts if my charger is hooked up to the 2nd battery.

I have search the the National Luna documentation and don't see anything with regards to charging.

I have two deep cycle batteries a Sears PM-1 as my starting battery and an Optima Yellow top as my 2nd battery with all accessories connected to it. When the PM-1 dies I will likely go back to a traditional starting battery. I have read that the alternator can't really charge the PM-1 as it should so every once and a while I want to give this battery a good charge in the garage.

Thanks,
Chris

 

[DiploStrat]

I have the National Luna setup in my FJ. If I hook up a charger to the main battery the National Luna sees the charge and then distributes the charge to both batteries.

1. Is this a bad thing other than the charging process taking a lot longer?

No, it is a good thing. The charge won't take any longer unless the cabling between your two batteries is way undersized. When the voltage at either battery rises above whatever setting NL considers to be "full" charge, normally about 12.7v, then the relay closes and you have one big battery, which is exactly what you want when charging. If either battery is at a higher state of charge it will help to recharge the lower battery.

2. Is there an easy way to prevent this besides disconnecting a battery from the system when I want to give it a good charge? I believe this only happens when charging the main battery but need to see how the NL reacts if my charger is hooked up to the 2nd battery.

If NL does not include an override switch as part of the package, it is relatively easy to wire up a three position override with - force connect, force disconnect, auto. N.B. If you want to get fancy, as I did, you can even have two tell tales, one that comes on when the relay closes and another that comes on when the switch is in the force combine position, so you don't forget.

... I have read that the alternator can't really charge the PM-1 as it should so every once and a while I want to give this battery a good charge in the garage.

??? Why not? If it is because your charging voltage is not high enough, then you need to fix that. If it is simply because you don't drive enough and don't have solar backup, then a shore charger overnight is a great idea and you DO want it to charge both batteries. Unless your NL is misbehaving, simply connect a good charger to either battery and you are done.

N.B. I do this from time to time, but in my case, the connection is to the camper battery and the charging is done via my onboard inverter/charger.

 

[1Louder]

??? Why not? If it is because your charging voltage is not high enough, then you need to fix that. If it is simply because you don't drive enough and don't have solar backup, then a shore charger overnight is a great idea and you DO want it to charge both batteries. Unless your NL is misbehaving, simply connect a good charger to either battery and you are done.

N.B. I do this from time to time, but in my case, the connection is to the camper battery and the charging is done via my onboard inverter/charger.

The PM-1 is a big marine battery and I have heard that they like to be charged at a rate higher than what an automotive alternator can do. I have seen a hack for the FJ alternator that changes a fuse in the engine compartment to force the alternator to charge at a higher rate but don't have first hand experience with it. Something that is sold via eBay. http://www.ebay.com/itm/Toyota-FJ-C...MK3-/221855846860?hash=item33a7a391cc&vxp=mtr

Thanks for the feedback!

 

[DiploStrat]

Before you do anything ...

or spend any money, determine the output voltage of your alternator when charging your battery(s). If your alternator puts out 14v or more, you are fine. Depending on type of battery and temperature, you want to see voltages ranging from between 14.2v all the way up to 15.5v when the temperature is below freezing.

The device you have found is merely a plug 'n play version of this discussion: http://www.smartgauge.co.uk/alt_mod.html

One of the Toyota modules here might be better as you can adjust them: http://www.mechman.com/voltage-control-modules/

Volts is volts and amps is amps; you simply need to be within the correct range for your battery. A big marine battery (deep cycle? Not sure what they mean) just needs to be charged like any other battery. If you are using it as a starter battery, it will use the same number of amps to start your truck (i.e. not many) and still need the same number of amps to recharge as a dedicated "starter" battery. I would not be in a great hurry to change it. (Indeed, if you looked in another forum, I recommended that our Hungarian friend consider simply running two marine batteries with no isolator as the easiest way to cram enough battery for his Africa trip, under his hood.)

Unless you have been having problems with your starter battery, I would simply hook on a decent charger and run it overnight before long trips and from time to time - say once a week.

 

[1Louder]

I run an ultragauge which helps me keep tabs on the alternator output. I will do a test at the battery as well to make sure I am getting proper output. I wish I could find one of the articles where they talk about alternators not being able to keep up. Here is a video from 4X Overland which references battery selection and electrical systems. https://www.youtube.com/watch?v=XzfrJJ6Px3o

I won't replace the battery until it dies. It is only 2 years old at the moment and working fine. What I have noticed is that it may not be holding a charge as well as it should. I need to find a period when I don't need to drive to disconnect it from the system to see how long it holds a charge. Maybe I can get a chance this weekend. I have checked for any phantom power draw on the battery and there is none. All of my non-factory items are on my 2nd battery with a dedicated Bluesea fuse block.

On a side note I do have a 60 watt solar setup for overland/camping trips.

- Chris

 

[DiploStrat]

Methinks you are letting my Afrikaner buddies spook you a bit! (And yes, I have driven across some of the same pans they have.)

They are working on the assumption that your Toyota has a charging system that puts out less than 14v. These lower voltages had the advantage of reducing that chance of overcharging your starter battery.

If that is the case, they are correct; it will take a LONG time to charge the batteries. But most vehicles made over the last ten years or so, already have modern high voltage systems. (See my discussions with dwh on this forum.) If that is the case, as it is with my 2013 Chevrolet, you are fine with your NL "split charge" relay.

Remember, in that video they are looking at old Land Rovers and Land Cruisers as sold in Southern Africa. Hence their love for CTEK. (See also Sterling, Redarc, and other B2B systems.) Worth noting that CTEK, acknowledging the limitations of their D250S, i.e. a charge rate limited to 20A, now sell what they call a SmartPass, which is a split charge relay that integrates with the D250S. Basically, it closes the relay (like your NL system) to harvest a higher amp rate and then, when the batteries are almost charged, it falls back on the D250S to complete the charge.

A discussion of alternator regulators (also known as B2B - battery to battery chargers), like the CTEK can be found here: http://www.smartgauge.co.uk/controllers.html Remember, this is advertising by a competitor, but I think they are correct. (And National Luna would agree.)

But basically, I think that their approach is entirely wrong; rather than get your charging system running at the higher voltage required for modern batteries, they are proposing to chronically undercharge batteries and throw them away. That does not seem to be a very good idea to me.

Rather than pay a lot of money for CTEK or similar products to build a secondary charging system for your camper battery, spend less time and money to assure that your vehicle's system can work the way it is supposed to. Your US spec Toyota should be quite capable of putting out over 60A at 14v+. If you are not seeing a charge voltage of over 14v, then you need to fix that in any case; simply going to a cheaper starter battery and planning to throw that away is expensive.

Finally, I would question their assumption that deep cycle batteries have higher internal resistance. Perhaps, but AGM deep cycle batteries, like the Lifeline batteries that I use on my truck have extremely low internal resistance. What are you running as a camper battery.

Bottom line, I understand what they are saying, but I doubt that it applies to your US spec Toyota.

Hope this helps.

 

[Ducky's Dad]

If your alternator puts out 14v or more, you are fine.

Probably not, if he is trying to properly charge an Odyssey 2150 G-31. Even Odyssey says they need 14.7V or more to properly charge from the alternator, otherwise you probably need to put it on a high voltage/high amperage conditioning charger designed to accommodate the charging profiles of AGMs and the specific appetite of the 2150. This is directly from my discussions with Bruce Essig at Odyssey. Other batteries are easier to charge and to maintain.

 

[1Louder]

Probably not, if he is trying to properly charge an Odyssey 2150 G-31. Even Odyssey says they need 14.7V or more to properly charge from the alternator, otherwise you probably need to put it on a high voltage/high amperage conditioning charger designed to accommodate the charging profiles of AGMs and the specific appetite of the 2150. This is directly from my discussions with Bruce Essig at Odyssey. Other batteries are easier to charge and to maintain.

I was looking for info on the FAQ page there. Maybe I missed it. Appreciate all the info so far. If the alternator can't keep up how often should I put the battery on a charger then? It is my daily driver but that means only about 40 min or less use per day with more on the weekends. Of course the same applies for keeping a good charge on the 2nd battery and I have a trailer too.. Ha Ha it has shore power though.

I came across this old thread and will give it a read as well. One of my questions is discussed. http://www.expeditionportal.com/forum/threads/80568-AGM-Battery-maintenance-charging-for-dummies

 

[pugslyyy]

I was looking for info on the FAQ page there. Maybe I missed it. Appreciate all the info so far. If the alternator can't keep up how often should I put the battery on a charger then? It is my daily driver but that means only about 40 min or less use per day with more on the weekends. Of course the same applies for keeping a good charge on the 2nd battery and I have a trailer too.. Ha Ha it has shore power though.

When you aren't on a trip, what is the load on the batteries? If you are running a fridge, fan, etc then you may need to do something other than the 40 minutes a day to top it off - solar comes to mind.

If they are just sitting, then they should be fine.

My truck sits when it is not in expedition mode, so I keep the house plugged in to shore power and the start batteries on a cheapo float charger. BUT I have a $2000+ investment in Lifeline batteries so I view my paranoia as justified.

 

[DiploStrat]

Gang, you are REALLY trying to polish bricks. The numbers you want are:

Absorb voltage, amp flow, and temperature. That is, most manufacturers declare that a battery is fully charged when it reaches a given voltage and the amp flow drops to a given number. Of the two, the amp flow is the key, the voltage just determines how long it will take you to get there. (It is when the amp flow drops, typically + a few hours, that the charger shifts from absorb to float.)

As all lead acid batteries have a long absorb stage, often longer than you will drive, you are more likely to reach these numbers with your shore or solar charger than with your starter battery.

But your starter battery doesn't do that much work. It is the load on the starter battery that matters, not its type. Starter, Marine, or Deep Cycle, starting a Land Cruiser simply is not that much of a task.

The folks on the video were talking about the task of recharging a deeply discharged battery, one with high internal resistance, with a low voltage vehicle, on a short game drive. As noted, it may not be your starter battery that you should be worrying about, but rather your camper battery, especially if you have refrigerator and only 60w of solar. One assumes that you have some form of hour counting meter on the camper battery, no?

In any case, for daily driver use, an overnight on a proper charger (E.g., CTEK or similar) should keep both of your batteries happy.

 

[Ducky's Dad]

If the alternator can't keep up how often should I put the battery on a charger then?

Your starting battery is a Sears DieHard PM1. The PM1 is an Odyssey 2150 31M rebranded for Sears. Bruce Essig at Odyssey has a 2150 in his non-daily driver 4x4 (I think it's an H3, but hazy on that detail) and he has his calendar set to put that battery on a conditioning charger every two months, whether he is driving the truck or not. He told me to do the same thing with the new 2150 in my truck. He can get any battery he wants, as often as he wants. Since I have gone through several batteries without doing the conditioning charge thing, I'm going to listen to him. The new Odyssey chargers are not out yet (as of last week), but the previous Ultimizers are pretty much limited to Odyssey batteries. The Ctek 25000 is a 25 amp 8-step conditioning charger that Odyssey recommends for that battery. After you drive your vehicle a while let it sit overnight and then check the open circuit voltage (OCV) on the 2150 at some reasonable ambient temperature, like 70F. If the OCV is less than 12.84V on a 2150, then you have a charging problem. Optima starting batteries (generally those with the dark gray case) are fully charged around 12.7V, while the Optima dual purpose (generally those with the light gray case) are fully charged at around 13.1V. If you don't have a multimeter, it's time to get one. My experience with both battery lines is that the Odysseys have more capacity in the same group size, but are more finicky about charging and maintenance than the Optimas. You may need to polish your brick if you want it to last.

 

[Ducky's Dad]

I have checked for any phantom power draw on the battery and there is none.

I don't know what the parasitic drain should be on an FJ, but my Dodge was right on 35 ma before the recent changes to the system. Everybody, including Dodge, said that is right on the money for that truck, and my main battery was still going dead when the truck was parked for long periods. I'm guessing that your FJ has more factory electronic gadgetry than my Dodge 2500, so parasitic drain on your primary battery is probably about the same or greater.

 

[1Louder]

I don't know what the parasitic drain should be on an FJ, but my Dodge was right on 35 ma before the recent changes to the system. Everybody, including Dodge, said that is right on the money for that truck, and my main battery was still going dead when the truck was parked for long periods. I'm guessing that your FJ has more factory electronic gadgetry than my Dodge 2500, so parasitic drain on your primary battery is probably about the same or greater.

Of course there is something but not anything unusual non-factory. I can't remember the exact number but it was very small. Leave a door open and that goes up. I went through all the fuses to make sure there was no drain from some other piece of equipment. This morning after a long charge the PM-1 was at 13.1. I should have brought my multi-meter with me to check when I get back home. In AZ it is darn hot at the moment so no 70 degree test until Feb! I will see what the NL says when I get in before I start the car but it does a lot of rounding of #'s. The Optima was at 12.9. The Optima is very new (2 months old). All accessories are off at the moment via breaker so it will be interesting to se what it reads. Normally I don't see unusual drain there. As for my alternator at idle it was around 13.4 and while at highway speeds/rpm 13.9.

This is the charger I have: NOCO Genius G3500 6V/12V 3.5A UltraSafe Smart Battery Charger

 

[DiploStrat]

To Review the Bidding ...

as this seems to be wandering.

-- The first question is whether a shore charger would work properly on a dual battery vehicle with an intelligent relay system. The emphatic answer is yes.

-- The next question is whether the factory charging system on a Toyota FJ is capable of properly charging a Sears PM-1 battery. The answer is probably.

-- The real question is probably not the starter battery, per se, but rather the total load of starter and camper batteries. 100A at only 13.9v may be a bit low.

I don't own an FJ, nor do I have any way to measure one, but from basic internet chatter, it appears that the factory alternator puts out about 100A. Based on the readings you mention, the factory voltage setting may be a bit lower than I would have expected. (It is also possible that your battery was fully charged and the Toyota is smart enough to go into float mode.)

There are lots of magic numbers being thrown about, but basically:

-- The simplest battery charger is another battery. As long as your charge source has a higher voltage than your battery, it will charge. Period. Increase the voltage and the battery will charge faster, that is, it will accept more amps longer. So if we define a full charge as being between 12.7 and 13.1v, a charger running at 13.9v will charge. It will simply not charge as fast as one running at, say 14.2.v

-- So why don't we charge at 20v? Heat and outgassing. Simply put, the charge voltage specified by the battery manufacturer is the highest voltage that the battery can take, at the recommended amperage (anything from between C/5 to as much as 5C in the case of Lifeline AGM), without the battery overheating or spewing acid. Or, in the case of an AGM, opening its vents.

Assuming that your FJ is reasonably in tune and starts reasonably well, and also assuming that you have no massive parasitic loads, a forty minute drive should keep you starter battery, whatever the type, very happy. A weekly or month charge, assuming that the charger is smart enough to go to float, won't hurt. Your NOCO sounds perfect for this.

The real issue may be your camper battery(s). What kind of load do you put on them and how long do you drive? In my case, I blow off around 125A overnight, you you may be sure that I am very happy that my truck puts out 14.4v (at 70F) because I want the fastest charge I can get.

If your Toyota has 100A available at 13.9v, it may not be able to recharge your camper battery on a typical daily drive.

 

[1Louder]

The real issue may be your camper battery(s). What kind of load do you put on them and how long do you drive? In my case, I blow off around 125A overnight, you you may be sure that I am very happy that my truck puts out 14.4v (at 70F) because I want the fastest charge I can get.

If your Toyota has 100A available at 13.9v, it may not be able to recharge your camper battery on a typical daily drive.

I have an off-road trailer with an RTT. The battery runs basic lighting, water pump, on demand water heater, and a relay for the gas line solenoid to shut off the stove if the drawer is closed. I don't normally charge phones, etc off of this battery and generally my ARB fridge stays in my vehicle. I do know that driving down the road does not charge my trailer battery a whole lot even after a full days driving. That's why I got the solar set up.

The point of my thread was to learn a bit more and make sure I am taking care of my expensive batteries as best as I can. I still don't like the National Luna controller bouncing back and forth between the two batteries and think it makes more sense to charge them individually once a month as has been suggested.

Again thanks for all the info and feedback to date.

- Chris