Dual Battery Shore Power Charging Question

[1Louder]

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&eres=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...istance=6&distanceunit=feet&eres=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 ...

My battery in the trailer is pretty buried and real pain to get to the posts. I will try to do that test. I can easily test at the 7 pin connector. My battery is in my tongue box so there is not an unusual amount of wiring. It is 10 AWG on the connector though for the 7 pin. Everything under the hood is 8. I used an eTrailer 7 pin kit that came with 10 AQG wiring.

 

[DiploStrat]

... I can easily test at the 7 pin connector. My battery is in my tongue box so there is not an unusual amount of wiring. It is 10 AWG on the connector though for the 7 pin. Everything under the hood is 8. I used an eTrailer 7 pin kit that came with 10 AQG wiring.

Granted that I am a wire/amp fiend, but run the numbers on your trailer with a 13.9v alternator and twenty feet of 10AWG wire. Let's guess that the alternator is making 50A. http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=3.277&voltage=13.9&phase=dc&noofconductor=1&distance=20&distanceunit=feet&amperes=50&x=82&y=16
That gives you a 2v drop, less than 12v at the trailer. (And we won't even talk about the losses of the connector.) At that point, you might as well disconnect the trailer battery and simply depend on your shore charger.

A friend of mine wanted a quick disconnect for his camper; he ended up with 1/0 AWG and massive "Power Pole" connectors. But he also ended up with a good charge.

The twin batteries under the hood look clean. If I read the specs correctly, your Optima battery gives you about 25Ah usable. That is not a lot to run a refrigerator. I would have expected that battery to be about 100Ah, that is, 50Ah usable, but I am not familiar with Optima batteries.

 

[1Louder]

Diplostrat,

I tested the 7 pin connector and voltage at is was the same with then engine running and engine off. Meaning they were equal to what was showing at the main battery. around 13.1 with engine off and 13.5 with engine on. I did get some higher alternator output readings before my drive. It was 14.1-14.3 with no lights etc and 14.0 with lights and AC on Max. I will save it for another day, believe it or not it's raining in Phoenix. To hook the trailer up to my vehicle and test the battery voltage with my engine running to see if there is anything less than the 13.5 volt reading. All of this has led me down the solar path. I have the 60 watt panel that can be run either on the trailer or my FJ. At some point I may put a flexible panel on the FJ and ditch the dual battery setup once and for all. I added this to a different post but if I keep this setup based on the PM-1's capacity I really should have all of my accessories on it and use the Optima solely as a backup to the starting battery. I have a busy work schedule this week but I will try to put my fridge in the weekend and do some testing again with just the PM-1 powering everything.

Thanks for all of your engineering work.

 

[DiploStrat]

In the end, you may need to get your hands on an ammeter to see what you are sending to which battery.

Based on my exchanges with Ducky's Dad, and confirmed with a source at Toyota, I was surprised to learn that the FJ (and a few other Toyotas) only charge at 13.9v. That is enough to get the battery "fully" charged, but it will take longer, and you will got give them the little micro equalization at 14.Xv that more and more manufacturers are recommending. This may argue for an investment in a good shore charger.

You can get a decent charge all the way back to a big bank of batteries at a distance from your starter battery; I do it all the time, but it does require:

-- A reasonably high charging voltage, ideally temperature compensated.
-- A set of rather large (and expensive) cables.

With an FJ you are right on the cusp of considering either raising the voltage of your whole system, or springing for a B2B like the CTEK D250S/SmartPass or one of the various Sterling Power units.

In all cases, a healthy solar charge system can help no end. This is one place where the CTEK D250S really excels as it includes a small solar controller.

 

[AndrewP]

Some of the under hood wiring is pretty suspect. The clamp terminals do not look clean, there is no heat shrink on the terminals and the wires look oxidized. With wiring like that you are getting not only the voltage drop in the wiring (which should not be too bad), but each of those less than perfect connections also induces a voltage drop.

What I'm not getting is understanding when you were driving around, the voltage in both batteries was still dropping. That is a major charging problem.

The trailer wiring sounds more straight forward. Your wiring is too small for rapid charging, but likely OK if you're driving a long distance.

Spend some quality time with your volt meter, clean all your connections and grounds and I'll bet this will be easy to sort out. Iam still very suspicious your NL dual battery system is doing something bad to your system.

 

[1Louder]

It's been about half a day and the PM-1 has been stable at around 12.5 volts. It was just at 13.1 when I came home from running errands but dropped to 12.55 after an hour. I am going to leave all accessories off for the remainder of the night and will take a reading at 4:30 and then when I finish work around 7:30pm but will activate the accessories.

My Optima charged pretty quickly and seems to stable at 12.8 volts sitting on my work bench not connected to anything.

More on Wednesday when I am off again and can mess with things...

Thanks!
Chris

 

[Ducky's Dad]

the PM-1 has been stable at around 12.5 volts. It was just at 13.1 when I came home from running errands but dropped to 12.55 after an hour.

Without knowing how long you were running the truck, it seems there may be issues with that battery. Full resting open circuit voltage (OCV) on a PM1 is 12.84V or higher. Anything less than that after you flash off the surface charge or let it rest for about eight hours indicates sulfation.

My Optima charged pretty quickly and seems to stable at 12.8 volts sitting on my work bench not connected to anything.

May be a similar issue with the Optima. I'd have to check the specs, but I think an Optima yellow is fully charged at 13.1V or higher. My "retired" Optima yellows stabilize between 12.65 and 12.85V after a stint on a small AGM conditioning charger, and they will hold at that level for up to a year. I always keep a couple around for emergencies and for testing lights and such.

 

[1Louder]

What I'm not getting is understanding when you were driving around, the voltage in both batteries was still dropping. That is a major charging problem.

While driving the voltage does not drop. The batteries are charging. Yes, when my battery mount fell a part something was a miss. This happened one time only.

 

[DiploStrat]

Without knowing how long you were running the truck, it seems there may be issues with that battery. ...

I would agree. You need to go after this step by step.

1. Does your alternator charge you starter battery?
2. Is that battery good?
3. Does your relay close when expected appropriate?
4. Do you get the proper voltage/amperage at the second battery?
5. Is the second battery good?

Once this is all checked, you can move on to the trailer battery.

Not hard, but can be complex.

 

[1Louder]

Without knowing how long you were running the truck, it seems there may be issues with that battery. Full resting open circuit voltage (OCV) on a PM1 is 12.84V or higher. Anything less than that after you flash off the surface charge or let it rest for about eight hours indicates sulfation.

It was on the charger for 18 hours. I then drove for 45 minutes with 2 engine starts during that time. Battery was charging off of the alternator. When I took it off of the charger the voltage was 13.1. When I stopped driving it was 13.1. When I checked it an hour later it was 12.55. Seems like a big drop in an hour. Sears will probably say the battery is fine but I will take it out and have it tested. I have a spreadsheet where I am documenting everything. On my days off I can test them almost every hour if need be.

 

[1Louder]

I would agree. You need to go after this step by step.

1. Does your alternator charge you starter battery?

Yes, and I don't think I have ever indicated that it didn't.

2. Is that battery good?

TBD. It is less than 2 years old and we have gone back and forth about specifics with Odyssey batteries and how they are unique. May be the wrong kind of battery although many seem to run it. I can ask some of my friends with the same battery what their resting voltage is. Although most run a fridge 24/7.

I am willing to buy a good tester if there is one that won't break the bank. Here are two possible options:

SOLAR BA5 100-1200 Cold Cranking Amps Electronic Battery Tester
by Clore Automotive
Link: http://amzn.com/B0017R5EQK

Schumacher BT-100 100 amp Battery Load Tester
by Schumacher
Link: http://amzn.com/B000AMBOI0

3. Does your relay close when expected appropriate?

If you are talking about keeping the batteries separate the solenoid was not working properly and it was replaced. New one seemed to be working. The controller does open and close for charging the 2nd battery per the specifications.

4. Do you get the proper voltage/amperage at the second battery?

When charging it was receiving the same voltage as the main battery. I can't test further because it has been removed because the mount failed.

5. Is the second battery good?

It's 3 months old. I would hope so. Without the fridge running it always seemed to be fine. Maybe not at 13.1 volts but I would possibly attribute that to the Toyota alternator and not the NL Controller. So many readings and tests it's hard to remember exact numbers but I think it would stay around 12.8 or 12.9 with no load.

Once this is all checked, you can move on to the trailer battery.

Not hard, but can be complex.

For the trailer battery I found an issue with the gas cutoff relay. This is a safety switch so if the stove drawer is closed the gas will cut off. Something is up with it and will be troubleshooted. That's why there was a voltage drop/parasitic draw. Temporary solution is to pull the fuse which is easily accessible if it keeps acting up. I am also guessing that the factory alternator has trouble charging 3 AGM deep cycle batteries at once. That's why I added solar to at least keep the trailer battery charged and possible keep 2 batteries charged with the dual battery setup or a single battery and the trailer hooked up to the 7 pin connector.

I agree with your complex statement. That goes back to my thoughts on gutting the system and keeping things simple. I will continue to read, test, etc and hopefully share what I have learned with others in my off roading circle. I am always willing to help others when I think I know what I am talking about.

 

[pugslyyy]

It's been about half a day and the PM-1 has been stable at around 12.5 volts. It was just at 13.1 when I came home from running errands but dropped to 12.55 after an hour. I am going to leave all accessories off for the remainder of the night and will take a reading at 4:30 and then when I finish work around 7:30pm but will activate the accessories.

My Optima charged pretty quickly and seems to stable at 12.8 volts sitting on my work bench not connected to anything.

More on Wednesday when I am off again and can mess with things...

Thanks!
Chris

Hey Chris - I'll just pile on here and agree with the others, you need to do some basic troubleshooting. By my tables, an at rest AGM battery showing 12.5 volts would only be at 75% SOC. (I actually don't like for my house batteries to be below 12.5V after a a night of running stuff.)

So the question is - Is it a charging system issue, cable issue, battery issue, or none of the above? Sorry I can't help more, but that low a resting voltage shows that something is going on, IMHO.

Like some others here, I have a fairly substantial investment in AGM batteries to protect, so this is a subject that is near and dear to us!

 

[Ducky's Dad]

Seems like a big drop in an hour.

That is a big drop in an hour, but the most important detail seems to be that the battery is not fully charged unless it stabilizes at 12.84V or higher. After 18 hours on the charger, I have to wonder if the charger is doing what it is supposed to do. Assuming that it is a conditioning charger with appropriate AGM charge profiles, the following questions come to mind:
Are you disconnecting the battery from all loads when you put it on the A/C charger? That is important for desulfation.
Is the charger delivering the 14.7V+ that the PM1 requires?
Is the charger delivering at least 25 amps (50 amps is even better)?
Do you have the charger set correctly? Most of the "correct" chargers will have a "snowflake" or similar setting for batteries like the PM1.

Re load testers, it's hard to beat the Schumacher BT-100 for the price. It's way better and more reliable than the cheaper digital testers. The best tester would be a quality carbon pile tester.

If Sears is not giving satisfactory customer support on the battery, try calling Kathy at Odyssey tech support. She is very helpful.

Just had another thought. After giving the PM1 as full a charge as you can, leave the truck parked overnight with the battery completely disconnected from load. Check the resting OCV at night (after flashing off the surface charge) and again the next morning. If the battery is good, there should be little or no change. If that is the case, then you know the problem is in the truck, probably a short somewhere or something staying on (glove box lights, etc.). If you have an aftermarket alarm, that would be a good place to start looking. If the battery shows significant voltage drop overnight, then you know the battery has an issue, probably sulfation. If it is sulfated, some chargers may be able to correct that. If the battery is still in warranty, Sears should just swap it out, but you'll still need to deal with the root cause of the problem.

And another thought: If the charger needs 18 hours to bring the battery to 13.1V, that indicates that it may just not be putting out the amperage required to keep the PM1 happy.

 

[Ducky's Dad]

I just found this in one of your earlier posts:

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

I think that charger, combined with the Toyota's relatively low alternator output, is the crux of your problem. The Toy's alternator can't adequately feed the battery, so it is sulfating. The NOCO charger does not put out enough amperage to overcome the sulfation, so you get a surface charge, but the plates are still sulfated. AFIK, the NOCO is not an approved charger for any Odyssey batteries, but it is certainly too small for a PM1. I think you need to invest in a better charger if you want to keep using Odyssey batteries. Not good news, but it is the same conclusion I reached on my big Odyssey batteries. Odyssey may still have their Ultimizer 40 amp 3-bank charger on closeout for about $140, delivered. I have one of those and it does work, but it is big and heavy and cumbersome with all those cables and clamps hanging off it. If I were doing it again, I'd get a Ctek 25000 for about $208 (Amazon) (and may still do that). Call tech support at Odyssey and check my theory before you spend money on a new charger. The NOCO charger may be fine for your Optima batteries.

 

[1Louder]

I just found this in one of your earlier posts:

I think that charger, combined with the Toyota's relatively low alternator output, is the crux of your problem. The Toy's alternator can't adequately feed the battery, so it is sulfating. The NOCO charger does not put out enough amperage to overcome the sulfation, so you get a surface charge, but the plates are still sulfated. AFIK, the NOCO is not an approved charger for any Odyssey batteries, but it is certainly too small for a PM1. I think you need to invest in a better charger if you want to keep using Odyssey batteries. Not good news, but it is the same conclusion I reached on my big Odyssey batteries. Odyssey may still have their Ultimizer 40 amp 3-bank charger on closeout for about $140, delivered. I have one of those and it does work, but it is big and heavy and cumbersome with all those cables and clamps hanging off it. If I were doing it again, I'd get a Ctek 25000 for about $208 (Amazon) (and may still do that). Call tech support at Odyssey and check my theory before you spend money on a new charger. The NOCO charger may be fine for your Optima batteries.

Page 16 of this document talks about the ability to use a 10amp or 20amp charger although earlier in the document Odyssey says you should use a 40amp. Noco makes a 26 amp and those are a little more in the tolerable price point range. So I am curious if anyone has had success with a lower amp smart charger.

PC1350, 31-PC2150
& 31M-PC2150

10 AMP Charger - 16 hours
20 AMP Charger - 8 hours

http://www.odysseybattery.com/documents/us-ody-tm-001_0411_000.pdf

Still not cheap but just under $200.00
NOCO Genius UltraSafe Smart Battery Charger 26 Amp
by NOCO
Link: http://amzn.com/B004LX14Z2