Adding a 2nd battery

[Madd Max]

Hey all,

I want to wire in a second 12V battery for my fifth wheel trailer, and I can't remember if you do it in paralell or series to stay at 12V. Many years ago I used to know this stuff. Paralell is Pos to pos, neg to neg. Series is pos to neg, Neg to pos , right? :confused:

Thanks in advance
Dennis

[DmaxMaverick]

Paralell. Pos to pos, neg to neg. Double check with a voltmeter. Unless the batteries are the same series (format), the poles can be oposite.

If you are going to purchase 2 new batteries, consider a pair of 6 volts, wired in series. Many new trailers are coming from the manufacturer that way. The only disadvantage with them is you can't operate on just one. The major advantage is they cycle deeper, and last longer. Optima's heavy duty deep cycle setup is a series of 6 volts.

You may also want to check your power converter in the trailer. Be sure it is rated to handle the capacity of both batteries. Some converters can't handle that duty cycle. The best option is to install a battery conditioner, which will charge and maintain the batteries without damaging them, or the converter. Most cases with a modern trailer won't cause any problems. Older trailers, even if they have room in the battery compartment for 2 or 3, fall short on the converter. Converters aren't cheap. A good one will run over $200 for 60 amps.

My 5'er is a '95 model and had a 40 amp converter. 2 months after I installed a second battery, the converter went south. I replaced it with a high quality US made 80 amp, and the batteries charge well and the DC power doesn't drop when charging the batteries are charging from full discharge (10.5V). If your converter doesn't have a cooling fan, it'll probably fail prematurely under those conditions.

There's a lot of stuff involved in this, and I learned it all over the last couple years the hard way. It cost me 3 new batteries and a converter. I added a new battery to a battery that was about 1/2 used up. The old battery failed, and took out the new battery. I should have known better, having preached for years, the "replace in pairs" when it came to the trucks. This is probably what killed the old converter. In the end, I now have a new high capacity converter, and two new Blue-Tops. The end result is OK, but the worst parts of the process showed up during dry camping, twice.

Sorry for the long answer, but most people don't think that far ahead.

Good luck!

[richp]

I second Dmaxmaverick's post. Two Trojan T-105 batteries wired in series gives you 225 amp-hours, about half of which is usable. I have 140 watts of solar panels on the roof of my fiver, and I dry camped once for 10 weeks without ever plugging in. Even 75 watts of solar and a good charge controller will give you a degree of independence you never dreamed of.

For what it's worth.

Rich Phillips
Member #27

[Madd Max]

DmaxMaverick,

Thank you, and please don't apologize for the length of your post. I consider every bit of information on any subject a big plus. In fact, because my memory is just not what it used to be :( :mad: , I keep a small 3-ring binder for each of my vehicles, I keep info on mods I've done as well as future mods and other important info to help me out.
I think I will be ok with my present converter as the svce. Mgr. told me it was set up to handle 2 batterys and it is 2005 model.
With the 2 6volt batterys in series, will my present converter charge them ok? If I need to get a battery conditioner, what are they and where would I find one? Thanks again for your time and the info. richp, thanks for your $.02 also.

Dennis

[Bob E.]

Madd Max-- What is the Brand and Model of your converter? I had an old Magnetec converter on my current trailer and it burned up batteries by overcharging. I am getting an Excel R/T this next week with a PD9145 converter with Charge Wizard which makes it a 3 stage charger when you have hook-ups.

richp-- What controller do you have? We have 155 watts of solar and I am researching a controller.

[Turbine Doc]

Lyncom controller SCR-12 is good for 12 amps has temp compensation, I have 155W solar charging at my hunting camp, I run Marine Gel cell batteries 325 AH Ea with conservative use of water and lighting I can run about a week if there with a couple of folks before I have to fire up generator & charger. Changing from incandescent to 12V flourecsent lighting saves juice, best price for that has been JC Whitney in RV section of the catalog.

check here http://www.partsonsale.com/ when I bought my panels 5 years ago they had best price on the net, I just went to their site looks like they carry a different controller now.

another good site is www.windsun.com (http://www.windsun.com)

[ 02-25-2005, 05:08 PM: Message edited by: tbogemirep ]

[DmaxMaverick]

Try this place (http://www.rvpartsoutlet.com) for just about everything RV. Very extensive inventory and excellent customer service. If you can't find a part on the website, call them or send an email for a very quick response.

I use them almost exclusively. They are pretty close to you, so shipping will be relatively quick. I get UPS regular ground stuff in 2-4 days to central CA.

[richp]

For a while I had two separate ICP controllers, because I added the panels at separate times. I recently swapped to a single Morningstar PS-30, which has a pretty sophisticated charge control capability to give optimal chargin for various battery charge states. It's particularly nice since it has an small digital readout that gives actual numbers on charge state and useage, not just LED lights.

On the non-solar side of the system, I have an Iota charger with their version of the "charge wizard" to prevent boiling and periodically hit it with a higher current to prevent plate sulphurization (I think that's the term). I'm 500 miles from the trailer right now, but I think it's a 40 or 45 amp model, which would bring my two T-105s back up from 50% discharge in a couple of hours.

For what it's worth.

Rich Phillips
Member #27

[Bob E.]

richp-- I was going to order the Morningstar ProStar 15 with meter and remote temperature sensor but the rep at Wind-Sun warned me if I was considering another solar panel that I would be very close to the controller's limit. For the extra $30-40 bucks the 30 amp is probably the way I will go. Did you get the remote temperature sensor?

[richp]

Bob,

Mine has a remote sensor for battery state, but I didn't go with the temperature accessory. Maybe should have, but the system does so well for me now that I just didn't feel like that additional cost got me that much in benefit.

Good luck.

Rich Phillips
Member #27

[Madd Max]

Bob E,

My converter is an IOTA DLS-30, it has a 30 amp otuput and it also has a cooling fan. I am not going with solar panels at this time, but I am interested in going with the two 6V in series. Is there any thing else I need to buy to accomplish this and where would I connect it?

Thanks,
Dennis

[DmaxMaverick]

....but I am interested in going with the two 6V in series. Is there any thing else I need to buy to accomplish this and where would I connect it? Just replace your old battery(ies) with the two 6V's. Connect your existing trailer batt+ cable to one of the 6V's + post. Connect your existing trailer batt- cable to the other battery - post. Using a short "jumper" cable, connect the two remaining posts together, + on one, - on the other. Be sure the jumper cable is at least the same size as the cables you are connecting from the trailer.

The route should look like this:
(trailer cable +) -> (battery #1 + post), (battery #1 - post) -> (jumper cable) -> (battery #2 + post), (battery #2 - post) -> (trailer cable -).

You can get the short jumper cable just about anywhere. Walmart has some, of different lengths and gage, with eyes on them. I recommend a 2 gage. The length will depend on how you have them arranged.

[Madd Max]

DmaxMaverick,

Do you think I would need the Battery conditioner you spoke of earlier or is that part of a solar panel set up? Sorry for all the questions, I just don't want to mess things up.

Thanks again
Dennis

[Bob E.]

Madd Maxx,

In looking at the Iota website, they offer an IQ Smart Controller for $25 that would make your converter into an automatic 3 stage charger. I would go with 2 6volt deep cycle batteries. I use the Concorde AGM 220 ah batteries. Here is a link that will tell you all about the pros/cons of batteries http://bart.ccis.com/home/mnemeth/12volt/12volt.htm

hth
Bob

[Madd Max]

Bob E.

Thank you, and all the other fellas for the input.That was a great link! I feel I know about every thing there is to know about the subject.
But I still printed it out and put it in my memory backup binder.

Thanks again,
Dennis

[DmaxMaverick]

Great!

Let us know which way you go and how it turns out.