6V In Series Or Parallel?

[ramblinboy]

My 6V Trojan T105's don't hold a charge. I'm not sure how old they are so I'm considering replacing them with T145's for more dry camping reserve. Is the set up shown in the attached pic the correct connection when I replace them?

Thx rB

[Guest BillAdams]

That looks right as you need to take 2 - 6V batteries and create one 12V circuit. That would require that you connect the + terminal at one end and the - terminal at the other with a jumper between the remaining+ and - terminal (series). If you wanted to end up with a 6V circuit (which you don't) you would connect the positive and negative of one battery to the main and then have jumpers from + to + and - to - totaling 6V but more amp hours. This is the setup you would use if you had multiple 12V batteries on board (parallel).

[wolfe10]

Yes, just as Bill said, your RV runs on 12 VDC. To make 12 VDC from two 6 VDC batteries, the two batteries are wired in SERIES.

Positive of battery #1 to house positive. Negative of battery #1 to positive of battery #2 and negative of battery #2 to house ground.

Think of the two 6 VDC batteries in series as "a 12 VDC battery in two cases".

And, wired in series, amp-hr capacity of the 6 VDC batteries remains the same, though voltage doubles. So, a pair of 220 amp-hr 6 VDC batteries wired in series will give you 220 amp-hrs @ 12 VDC.

[chucknewman]

"My 6V Trojan T105's don't hold a charge." The date of manufacture should be on the batteries. Call Trojan for help with this.

You didn't state the time period from charge to discharge. What is the actual charge voltage, and duration? Are you using a three stage charger? What is the actual combined battery voltage (series voltage) when they "don't hold a charge". How long was it since full charge? Have you done an electrolyte test? Were the batteries disconnected or wired into the coach with loads during this time period? If loaded, how many amps over what time period?

Lots of questions to ask to determine the cause of your problems. Many batteries are needlessly replaced due to charger issues and/or unknown loads on the batteries. And of course, if you determine the batteries are more than five years old, you should replace them. Even then, age is not as much a factor as how the batteries were care for -- as in maintenenace, charging, time between charges, and depth of discharge. The latter being a battery killer if overdischarged repeatedly.

The T-145 will give only 13.5% addition to the 20 hour discharge rate of a T-105. That is not significant for the added price. I really don't think that is your problem, though the existing T-105's may be toast. Also note the T-145 is about one inch taller than the T-105.

From the photo, I notice you have corrision within the wire on both positive and negative lead. Both leads need to be replaced or cut back and new stube spliced in place. Then clean and grease the battery connectors (and new splice points if used) to prevent further corrosion. But you need to find your load issue first.

Chuck

[ramblinboy]

Many thanks for the advice fellas. I have not ever had a full charge on these batteries either from the genny or shore power based on my control panel lights at least. Not having done a lot of dry camping I haven't really tested the reserve.

My converter/charger is the "IOTA DLS-55/IQ4 featuring an internal IQ Smart Charge Controller which automatically provides three-stage battery charging for safer charging and longer life for your system's battery." I've always topped up the batts with distilled water but I have not measured the SG with a hygrometer.

[wolfe10]

ramblinboy,

Those "idiot lights" are just that. To really tell voltage, you need to use a digital voltmeter at the batteries. If you don't have a digital voltmeter, get one-- they start at under $20 at Sears, Radio Shack, etc.

[ramblinboy]

I agree Brett my Harbour Freight cheapie doesn't cut the mustard. I'll get a DVM and then get a better feel for the issue. I've found out the date code on the batts so will have a look at the age.

http://www.trojanbattery.com/Tech-Support/FAQ.aspx

[ramblinboy]

Based on the advice here I will not buy new batts until I've actually tested the current pair with my new digi voltmeter - 20 bucks invested could save me a few down the road. Sounds like good advice here:

http://www.macandchris.com/RVBatteries.htm

• Plan your battery charging.

  
  

  • First thing in the morning, note your batteries state of charge. If they are below 50% write down how far below (let's say they're down 20 amp hours below 50%).

    
    

  • Start the generator first-thing in the morning (as soon as quiet hours are over) and start charging your batteries. Also, use this time to run other appliances as needed. Don't turn off the generator until the batteries are at 100%. This might take 2 or 3 hours, maybe more. It's also OK to take them up to 95% 3 out of 4 days and then 100% on the 4th day.

    
    

  [*]

  Be frugal with power use all day. Turn off anything not needed. Remove phantom loads. See Conserving Power and other chapters for more tips.

  [*]

  During the day/evening, any time you run the generator to power the microwave, toaster, etc. be sure to charge batteries too (assuming your generator will do both at the same time)

  [*]

  Re-start your generator when your batteries reach 50%, or when they reach 50% plus the previous morning deficit (see item 1 above). Be sure to charge your batteries enough in the evening so they will NOT be below 50% the next morning when you wake up.

  [*]

  Start over at #1 and repeat every day.

[wolfe10]

Sage advice, EXCEPT when dry camping it is NOT economical to run a generator to power a converter, charger or inverter/charger until the batteries are 100% charged. Charge rate tapers off dramatically as they get charged so that as they pass from BULK to ABSORPTION phase, the amps into the batteries per hour of generator run time is unreasonable low.

When dry camping, discharge to 50%, recharge to 85%, discharge to 85%.... Yes, once a week batteries need to be brought back to 100% charge.

BTW, this is pretty much second nature to those of us whose introduction to "The 12 VDC Side Of Life" was life on a sailboat where you are "dry camping" (ya, strange term for being anchored out-- had to translate that into the "land cruising term"!) and having to run the primary engine (4 cylinder diesel in our boat) so that the alternator can charge the batteries. With diesel hard to find in the islands and $5+ per gallon, we minimized run time.

Brett

[desertdeals69]

With regard to the corrosion in the picture, I have tried various treatments to prevent the buildup. About a year ago I discovered a couple of products made by CRC. One is a terminal cleaner and the other is a spray coating which dries and had a red tint to it. Unlike grease which attracts dirt buildup, my terminals and cables are clean for over a year.

[chucknewman]

Keep in mind battery terminal cleaner (or plain old baking soda) cleans off the acid residue just fine. It does not renew, repair, or change the added resistance in the wires and/or cable connectors due to pitting and loss of usable copper or steel due to being eaten away by the acid. Those issues are properly repaired only by replacement.

The "spray coating which dries and had a red tint..." does work. It's primary saleability is that it is easy to use and it "looks nice". When dry it is a sealant like a varnish. It also has a high dielectric to current flow meaning it can be difficult to get a true voltage reading after this stuff dries. And it has to be scraped off if the terminal or connector physical configuration ever changes or else you end up with high resistance connections.

Heavy weight grease is standard on battery terminals in the telecommunications business industry because it lasts as an acid vapor seal, and does not become a "hard surface". I use grease on all my exterior incandescent and LED light bases for the same reason -- instead of acid vapor it prevents water vapor from entering the bulb base and corroding the terminals.

Chuck

[desertdeals69]

As far as exterior light sockets go, I have been using DC4 compound for at least 55 years.

[deenad]

With regard to the corrosion in the picture, I have tried various treatments to prevent the buildup. About a year ago I discovered a couple of products made by CRC. One is a terminal cleaner and the other is a spray coating which dries and had a red tint to it. Unlike grease which attracts dirt buildup, my terminals and cables are clean for over a year.

I just replaced my starting batteries Friday before last and my house batteries this weekend. They were the oem's and were 9½ years old. The starting batteries were totally dead (2 hrs on a 60 amp charger) and I still couldn't start the engine. While getting them out I looked closely at the Interstate U-2200's and found they were bulging. Still seemed to work OK but we're headed out and didn't want to stranded somewhere.

I bought the CRC cleaner and spray a couple months ago because they were on sale. I used them both.

BTW, adding plain old mineral oil to each cell will almost totally eliminate the corrosion. I did it to the house batteries in 2004 and have almost no corrosion in the bay.

I used 4 oz per cell on the U-2200's.

[ronmonson]

Has anyone ever used just plain old petrolatum on the posts and connectors?

I also have a question about the cable lengths....in the recent magazine article about batteries, it states that all the battery connection cables should be the same length? I am not sure how you can do that with the different connections to different batteries?

[dickandlois]

Same Gage yes,when it comes to length, 3 to 4 feet not enough loss difference when your talking 2,4,and 6 gauge wire. Now, if you start getting up to a length of over 10 to 12 ft. same length is good.

Having said that, you will see that most of the long large cables are RED Pos. and they use the frame for the ground. That is one of the main reasons to keep all the ground points clean and tight.

Petrol Jell will keep things protected very well for the price.

R.M.