12v Batteries

[dvieira]

Hi. .



Does it hurt the trailer electrical system if a person has 2 12volt

batteries hooked up to the system at the same time, or should use one battery at a time?



thank you

dave

 

[Thomas]

Hooked in parallel=Good



Hooked in series=Bad

 

[FParisi]

My 5er came with 2- 12v batteries - very common. When they went out I replaced with 2 - 6v in series to make 12v - for better deep cycle service.

Frank

 

[dvieira]

Hi.



parallel is that= + post, then neg to neg, then +post again?



series= is that +post then neg to +post then neg. .

a little confused hee, will have to look up. .



thank you

 

[Thomas]

Parallel is + to + & - to -



I believe you are thinking correctly.

 

[FParisi]

Right. Look at your truck - 2 12v batteries in parralel.

 

[Teacher]

Battery series

Frank,

 

[Teacher]

Battery series

Frank,



For the uninitiated like myself, please give more details about the 6V series set-up and exactly why it is more advantages.

Thanks!

Jim

 

[FParisi]

My understanding is that the 6v batteries (golf cart) are very good for deep cycle use because they have thicker plates -each one is the size of a big 12v - so they tolerate the deep discharge/recharge cycles better.

Frank

 

[BK]

Yes, FParisi is correct.



just to add a bit. . it's not just the cycling. . but the current levels...



The main reason for the 6v battery is that they tolerate Much Higher charge and discharge rates (current/time) for the reasons FParisi mentioned. In your trailer applications, you don't see 150 - 300 amps draw for 10's of seconds... as in an electric vehicel application. In the EV apps, is where the 6v's space, weight and size had been tolerated for their performance.



But with some of the newer battery technologies the better 12V batteries have the same "capacity" for use in your trailer as a pair of 6volts do... the good single 12volt will be about the same price as the two 6volts. . but the single 12 would be smaller allowing for more amp/hour per square inch... . main reason, you don't need the appility for the very high current draws in the order of 100's of amps.

 

[Teacher]

?????

Bk.



Yes, well uh, um it's getting clearer now. Now can anyone put that valuable information into practical englishese?????

Thanks to all who have responded.

Jim

 

[BK]

Sorry.

I know that I do a lot of rambling at the keyboard as it spills from the brain to the fingers... and at times I know I'm not the best writer either. .



So let me try it again... if there's a particular point I didn't word well... (I'm terrible at reading what I wrote. . I read what I thought I wrote... )



I'll start by saying the 6v golf cart batteries are really designed for just that. . to power the drive system on an Electric vehicle. . such a battery pack is known as the "traction pack". During acceleration, current draw can be very large depending on lots of things. . Easily 300 amps can be seen, so the battery needs to be made to handle such current. . heavier plates and such to reduce things like internal resistance. But when you make internal contacts heavier, plates heavier. . other characteristics my suffer...



Your trailer. . you might draw as much as 30 amps at times. .

So do you really need a battery designed to live nicely through 300 amps?. . since your giving up space to those big heavy plates. . your giving up energy storage capacity,which is what you really want.



The way a battery works, more plate surface area is more capacity. Capacity is the amount of engery you can draw from the battery over time (amp/hours).



So you can either design a battery to have real thick heavy plates to handle high currents. But capacity and voltage suffers.

Or in the same size, you can change the technology and use "thinner plates" (foil wraps) , fit in more to raise the voltage (12V as aposed to 6v) and increase the surface area so more energy can be stored (amp/hours). What you loose is the ability to handle very high currents well and high charging currents (can't charge the battery has fast by using high currents without reducing the number of cycles it will live through... and causing excessive heat which is death to a battery)



So what I'm saying is there are battery designs out there that are designed for work such as for the trailer. If you put two of them in (2 12v in parrallel), you would have twice as much stored engergy than you would with the two 6v's(in series). . in the same area. . (foot print and height)

Because the 6v's aren't designed for energy storage denisty. . but high current applications. FParisi is totally correct in saying that they can live through more punshiment and deeper cycling. . since they can handle the heating better thats caused by the high currents.



But. . when charging your batteries from the trailer's AC-DC 12 power supply, that charge current is well within the safe zone for 24/27 group size car battery or gel cells... the battery wont get hot. Your discharge currents in the trailer arent high. . 30 amps is a lot. . again these 12v batteries wont get hot from that. Charging from your truck. . the wire going back to your battery will act as a current limiter due to it's resistance. I doubt you'll see much more than 60 amps (when your batteries are fullly discharged) being drawn by the trailer batteries because of the wiring and connector resistances. Again that's not a current that's going to kill the batteries.





So what are the things that harms the batteries, even the 6 volt batteries:

--The voltage that the charger is set to. If you leave your trailer plugged in all the time, your charger (ac-dc in the trailer) shouldnt be set higher than 13. 2 - 13. 4. Some are selectable. 13. 2 for being constantly plug into to Ac. 14. 5 for quick charge, meaning you plug the trailer in two days or so before you drive away with it.

-- very deep discharges (yes the 6v are better designed to handle this, but you can be giving up capacity for this. other gel cells - more money - are as good as the 6v but have more capacity in the same space)

--partial charges, than deep discharge.

--maintance. . the gel cells are the best at being maintance free. But in both cases keep the top of the batteries clean. The dirt on top of the batteries becomes conductive. Doesn't allow the battery to fully charge and decreases capacity by discharging the battery even though you don't think your using it.

-Vibration, again the gel cells are the best cure for this problem.



I guess I did some rambling again. . added a bit. tried to explain myself a bit more...

any better, or did I do just as bad as the other post?



Bob

 

[dvieira]

BK...



as Lawrence Welk said "Wonderful Wonderful", {i think}

.



anyway, as to my original question, my friend had the battery wires hooked wrong, for some reason, the manufacture had both negative & positive cables red, whoa !! after i figured it out,told him to either mark the neg black with tape/paint or buy black cables, that is why he ask about the using 2 batteries, he was hearing strange sounds inside his trailer... . :--)



thanks all... .



dave

 

[BK]

Dave,

sorry. . was just addressing the 6v vs 12v cell part of the conversation since the replies about the series and parrallel connections allready completely addressed that initial question.



Just to address the crackling you mentioned.....





I guess your buddy has shaved a few years of the batteries at best,, if he hooked the batteries incorrectly in parrallel by hooking BatteryA + to BatteryB -

and

BatteryA - to battery B+.



like this:

#ad




he shorted the batteries together.

If the batteries were charged, might have seen some hot / smoking wires that connected the batteries together.





If he made a 24volt battery by hooking them in series...

Battery A- to Battery B+

and then

the negative feed for the trailer to Battery B-

the positive feed for the trailer to Battery A+. .

like this:

#ad


he would have put 24V into the trailer. Any thing that was on and was powered by the 24V is probably fried by now... maybe that was the crackling... ????







This is what he wants todo, as descriped above by others:

#ad


Hooking them in parrallel correctly wont hurt a thing. It'll just take longer to bring them both up to charge. .

 

[dvieira]

BK...



i was commenting on your explanation, it was beautiful, well

written, and "I" understood it.....



as for your drawing, I'm printing them out !!!!



and then laminating them, and tacking them inside my battery/storage area in my 5th'er... .



thanks much BK... you made it simple... for me and a whole

bunch of other people.



dave

 

[BK]

Thankyou, I thought maybe you were being kind, regarding my ramblings... . which I'm noted for... and sometime going off on tangents.



When I saw your comment about the noises in the trailer after hooking the batteries up incorrectly...

I hoped a couple of pictures would be worth and easier than a million of my rambling words.





thanks for the kind words. .





Bob

 

[B.G. Smith]

Batteries

There is a good article on batteries in this months Trailer Life. bg

 

[merryman]

For a really complete and well done coverage of everything RV electrical--especially batteries and their care and feeding see

www.phrannie.org/battery.html



Vaughn

 

[bombero]

Yep; when I had my TT custuom made i made several mistakes. One of the big one was that I didnt get ^vt batteries

 

[Teacher]

Thank You

BK,



Thank you very much for your time and expertise. "You done good. " There is always something to learn and you "lurned me gud. "

I too loved your diagrams and will print them out for future reference.

It' this sort of thing (exchange of positive information, etc... ) that makes this site worthwhile ( as opposed to flaming!).

Thanks again and I hope I can repay the help sometime.

Jim