Charging 6v batteries

[Woody]

I have two 6v coach batteries wired to produce 12v (series-parallel ?) that I want to charge with my 12v battery charger.
With the covers on them I am unable to see which post is the + and which is the -. There are several wires on the posts at each outside end and a short connecting wire at the inside that just runs from post to post.
Can someone explain to me how these are wired and how I go about charging both batteries with my 12v charger ??
Thanks,

Woody

 

[John From Detroit]

Well, which is + and which is - depends on the batteries however there is an inexpensive solution, in fact there are two of them.

First ignore the short connecting wire, it's not part of this, go with the two that have multiple wires hooked to them

Now, the way I'd do it,,, I'd break out one of my voltmeters,  You can get multimeters (and every RVer should own one) at many places, I got lucky at a dollar store once, Yup, 1 buck per meter.  Harbor Freight is another resource.  They will show you which is which  (Red is + if the meter reads properly)

Option 2 is to use a light bulb coupled with your battery charger,  here is how it works  DO NOT PLUG IN THE CHARGER, now take any 12 volt light bulb and put the RED battery clamp on the bulb so it contacts the metal base but not the pin(s) on the bottom, they need to be exposed... If using a "Cartridge" shaped light (like the overhead light in many cars) hook the red clamp on one end so it contacts the wires.  Hook the black lead from teh charger to either post,  Tap the other bulb lead (the center "pin" or the other end) to the other post.. if the light lights.. You don't want to hook the red lead there, move the black to that post and try again, if the light does not light,,, Just for the fun of it switch the leads (This insures the bulb is good and everything is working the way I wish it to work)

Once you have the  bulb lighting one way, but not the other, hook the black lead to the post that it's hooked to when the bulb does NOT light, and hook the red lead to the post you touched the light to.. Good to go,  MARK THE POST some way so you can do it again easily

Method 3, wire tracing... One (At least one) of the big wires is likely very short and hooked to the chassis close to the battery box.  This Should be the NEGATIVE (-) lead  NOTE Should be

 

[King]

The batteries should be connected as follows:


  chassis ground ----- - {///} + ------  - {///} + ---------- coach wiring


most batteries have the "+"  and "-"  molded into the Case but if not, try connecting a bulb as in the previous message.
Art

 

[Woody]

So if I understand this right then all of the coach wiring is connected to the + terminal of one of the 6v batteries, a short wire connects the - of that battery to the + of the battery next to it, and then all of the ground wires are connected to the - of the second battery. Correct ??
I do have a Radio Shack multimeter but don't know how to use it yet. Guess I gotta get that little booklet out and read up on it.

Woody

 

[Terry A. Brewer]

Woody

>>Correct ??<<

Yes...Just put your red lead from the multi-meter to the "pos" of one battery & the black lead to the "neg" of the second battery, using the dc scale.

 

[Ned]

Woody,

Correct, the 2 6V batteries are wired in series to form one 12V supply.  Usually, the ground cable will be black and connect to the frame, and the positive cable(s) will be red, but that isn't always the case, so a check with a meter is in order to be sure.

 

[Tom]

..... using the dc scale.

Just for clarification, that would be "DC voltage" or "DC volts". The "DC amps" scale might just fry the wires &/or the meter.

 

[Woody]

OK, I finally got around to checking the two batteries with my multimeter, after I read up on it a little bit.
If I am reading the meter right both batteries might be bad. I am getting a reading of 3.04v when I just check one battery at a time and 6.94v when I attach the red lead to the + terminal of one and the black lead to the - terminal of the other.
PLUS, when I try to charge them by attaching the leads of my "smart" charger to the + terminal of one and the - terminal of the other it will only charge at about 3 amps for a minute or so then it goes off and I get the digital code for "shorted cell".
On pricing replacement batteries I've discovered these things aren't cheap. About $200++ per battery, so I really don't want to replace them unless they really are bad.
Am I doing anything wrong in checking or charging them ??

Woody

 

[Ned]

Every thing you've told us points to bad batteries.  Shorted cells would explain the very low voltage readings you're seeing.

What battery model did you price at $200?  That much money will get you AGM batteries which are much preferred over flooded cell batteries.  You should be able to get T-105 6V 220AH batteries for as little as $104 (see http://search.altenergystore.com/energy/Trojan%20105).

 

[Woody]

Hi Ned,

I started out pricing Lifeline AGM batteries. They only list one 6v and the prices varied from $260-$290. I then went onto the Interstate battery site (that is what I have now) and priced their regular lead acid deep cell 6v batteries and several sites I checked listed them for around the $200-$220 range.
I have bookmarked the site you gave me but I will have to contact them and check the size of the battery they list since I am limited to two batts that are 7"x10", no larger or they won't fit in the space.

Woody

 

[Alaskansnowbirds]

Hi Ned,

I started out pricing Lifeline AGM batteries. They only list one 6v and the prices varied from $260-$290. I then went onto the Interstate battery site (that is what I have now) and priced their regular lead acid deep cell 6v batteries and several sites I checked listed them for around the $200-$220 range.
I have bookmarked the site you gave me but I will have to contact them and check the size of the battery they list since I am limited to two batts that are 7"x10", no larger or they won't fit in the space.

Woody

Woody,

Check to see if there is a solar power company in your area. I purchased 4 Lifeline AGM 220 amp hour from Northern Arizona Wind and Sun this last January for $150 each.

 

[Karl]

I just purchased 2 Trojan T-125 flodded cell batteries for 109.99 each from, of all places, Gander Mountain. They are a master distributer. Had to be special ordered (took about 1 week), but there was no delivery charge. Whichever way you go, flooded cell or AGM, make sure your charger is a 3-stage type which prevents overcharging and frying the batteries. AGM's require a slightly different charging curve, so make sure your charger has an AGM setting, if you decide to go that way.

 

[Gary RV_Wizard]

AGMs are great (zero maintenance) but if you don't mind checking the water once in awhile, I'd go with the flooded cell lead acid type - much less expensive and last just a slong.  You ought to be able to find them for under $100 and as low as $60 in some areas.  Golf cart dealers is one source for Trojan T105's (the gold standard for wet cells golf cart batteries) but solar power stores are also a possibility.  Sams and Costco stores often have them on sale too.

But if you can get an AGM for $150, the zero maintenace is worth it, in my opinion.

 

[Karl]

Gary,

I searched long and hard for a good price, but with the cost of lead nowdays, it seems batteries have skyrocketed. Did find a few articles about $50-60 T-105's, but they were dated 2001,2002. If I could find that price or even close, I'd replace my two existing T-125's in a heartbeat. The Arizona solar stores weren't any cheaper unless you bought a pallet of 8. Some won't even sell in lesser qty's.

 

[Woody]

Karl,

One of the websites I read said that the price of lead is going down and that batteries should be getting cheaper, or at least stay at the same price for awhile.
If anyone has a URL for a site that has the cheap price for wetcell or AGM batteries with free shipping I would sure be interested. The site that Ned gave won't quote a price for shipping just says will ship by ground transportation and charge will vary.
Lifeline lists the Batteries Plus chain as one of their major distributors and I will be checking their local store tomorrow for a price. If I could get an AGM for $150-$175 I would definitely go with two of them.

Woody

 

[Gary RV_Wizard]

but with the cost of lead nowdays, it seems batteries have skyrocketed. Did find a few articles about $50-60 T-105's, but they were dated 2001,2002.

Well, I did say "under $100" , but maybe I'm out of date.  And Sams did not sell Trojans for that price - they were some other label.

Trojan T105 $103

Trojan T105 $99

Exide GC battery for $81

 

[Jim Johnson]

Woody,

Call Dave at 800 527-3224 about Lifeline AGM's.  I bought them a while back for $130 plus $16 shipping.

 

[Woody]

Thanks Jim. I'll give him a call tomorrow. If that price, or something close, still stands I'll place an order for two.

Woody

 

[Woody]

OK, I've run into another problem with this battery situation. I have read that AGM batteries need to have a converter/charger with an AGM setting because they are charged differently than regular wetcell deepcycle batteries.
In looking at my c/c and the owners manual it is a MagneTek 50amp Converter Charger Series 900 Model 950-2. The Owners Manual says that it is a "float type" charger and cannot overcharge a battery or batteries but there is nothing in it about AGM batteries. I'm not sure whether this is the original c/c that came with my 93 Pace Arrow or not but I suspect it is.
The Owners Manual lists the company address and phone number in Kokomo, IN and if they are still there and have that number I will call them tomorrow.
Does anyone know whether this will work with AGM batteries or will I need to order just regular wetcells. I don't want to have to shell out for a new c/c just so I can upgrade to AGM batteries.

Woody

 

[Ned]

The acceptance and float voltages for AGM batteries are slightly lower than those for flooded cell batteries.  You can use a flooded cell charger but the AGMs will be slightly overcharged when on float.  If you can keep a small load on them, there should be no long term problems.  If the charger has a temperature compensation setting, setting that about 10F higher than ambient will also reduce the float voltage to a value closer to the AGM value.