Charging batteries as 6 or 12 volt

[cgmartine]

I just bought two Trojan T-105 batteries to replace my house batteries, but I will not be installing them until my next trip in several months. In the meantime, I will be placing the batteries on my garage floor. I have a slow trickle battery tender that I use on my motorcycle that I can use (1.5 amps) or a heavy duty battery charger.

Should I charge the batteries individually as 6 volts, or together as a single 12 volt?

Second question: Which ever charger I use, should I place the negative lead of the charger on the negative battery post that would go to the body frame (battery #1), and connect the positive lead of the charger to the positive post of the battery that is connected to the motorhome? The batteries (in series) will have a cable from the positive post of battery #2 to the negative post of battery #1.

I hope this makes sense!

[tenbear]

Think of your two 6v batteries in series as one 12v battery. The wire between then is only used to connect the 2 batteries. A 12 v battery is the same except the connection between the two sets of 3 cells (6v battery) is hidden inside the battery case and you can't connect anything to it.

[wolfe10]

cgmartine wrote:
RoyB, so looking at your picture, I would connect the positive cable from the charger to where it says "+12 Volts" in your picture, and the negative cable from the charger to where it says "to ground," on your picture, correct?

YES.

Again, easy to remember, it to the posts with nothing else on them. The interconnect cable is on the "other ones".

[cgmartine]

RoyB, so looking at your picture, I would connect the positive cable from the charger to where it says "+12 Volts" in your picture, and the negative cable from the charger to where it says "to ground," on your picture, correct?

[Vulcan_Rider]

RoyB wrote:
NOTE That Progressive Dynamics doesn't even list using DC Charge Voltages around the 12.0VC range as this would take alot more than 100 hours to achieve a 90% or 100% charge state.

Roy Ken

Really excellent post.....until you had a brain cramp at the end.

They don't list 12.0 as a charging voltage because......it isn't.

Applied to a completely dead battery, 12.0 will only bring it up to about 25%, which is still considered dead.

[RoyB]

I would hook them for 12VDC and charge with the 12VDC charger connections.

You are going to have to do this setup anyway when you finally get it installed in the RV...



Also I would keep a close watch for boiling out the fluids. Unless you have a smart mode battery charger you may boil out the fluids over time.

The normal single charge voltage is 13.6VDC and this is known to boil out battery fluids over time. the smart mode chargers will first start out with 14.4VDC for two hours then drop down to 13.6VDC for one hour and finally drop down to 13.2VDC. The batteries will not boil out fluids when being hit with 13.2VDC.

Actually once you get your batteries charged up to full you can just disconnect them and they will sit in the charged-up mode for a long period of time. They will also not freeze up when fully charged...

Get an inexpensive multimeter from local stores ($12-$20) and make all of your measurements with this. Harbor Frieght used to give you one free when you made a purchase there if you asked for it.

This is what PROGRESSIVE DYNAMICS says in their brochures on how long it takes to charge up deep cycle batteries.
"Progressive Dynamics ran this test on the amount of time it took a PD9155 (55-amp) converter/charger set to three different output voltages to recharge a 125 AH (Amp Hour) battery after it was fully discharged to 10.5-volts.

14.4-VOLTS (Boost Mode) – Returned the battery to 90% of full charge in approximately 3-hours. The battery reached full charge in approximately 11 hours.

13.6-VOLTS (Normal Mode) – Required 40-hours to return the battery to 90% of full charge and 78-hours to reach full charge.

13.2-VOLTS (Storage Mode) – Required 60-hours to return the battery to 90% of full charge and 100-hours to reach full charge."

This is based on having 17-20AMPS DC current available for each battery in your battery bank... NOTE That Progressive Dynamics doesn't even list using DC Charge Voltages around the 12.0VC range as this would take alot more than 100 hours to achieve a 90% or 100% charge state.

Roy Ken

[wa8yxm]

I am fond of saying there are no SIX volt batteries in RVs
Only 12 volt battereies that, for ease in handling, are broken into two pieces.

Seriously as someone else said, put 'em in series, thus making one BIG 12 volt battery.. Set your battery charger as you would to charge a 12 volt size 4D.

And let it do it's thing.

[2oldman]

cgmartine wrote:
Since I am avid believer in sticking to the old wife's tales, I had already placed both batteries on wood blocks since I tend to follow true and tried traditions.

Won't hurt, won't help.

[RJsfishin]

The answer to your question is yes !
And a battery tender + will fully charge 2 6'ers in series.

[MEXICOWANDERER]

Give. Them a good zap with the big charger enough to make the cells bubble. Then disconnect.

Easy oriental type logic for connection.

Place both batteries side by side.

Grab ahold of charger positive lead

Connect this positive lead to one positive post of one battery

Then grab negative lead lead from charger

Connect this negative lead to negative post on OTHER battery

Now have only two unconnected battery posts

Make bridge wire and connect two lonely posts

You now have happy battery.

[Vulcan_Rider]

landyacht318 wrote:

I'd charge them full, then put them on the maintainer. Don't expect the maintainer to actually fully charge them.

THIS is good advice.

The other part is just another old-wives tale.
The liquid electrolyte is a fairly efficient conductor of heat and the "cold" of the floor will quickly spread to the whole assembly.

[cgmartine]

Thanks for your replies. Since I am avid believer in sticking to the old wife's tales, I had already placed both batteries on wood blocks since I tend to follow true and tried traditions.

[Golden_HVAC]

cgmartine wrote:
I just bought two Trojan T-105 batteries to replace my house batteries, but I will not be installing them until my next trip in several months. In the meantime, I will be placing the batteries on my garage floor. I have a slow trickle battery tender that I use on my motorcycle that I can use (1.5 amps) or a heavy duty battery charger.

Should I charge the batteries individually as 6 volts, or together as a single 12 volt?

Second question: Which ever charger I use, should I place the negative lead of the charger on the negative battery post that would go to the body frame (battery #1), and connect the positive lead of the charger to the positive post of the battery that is connected to the motorhome? The batteries (in series) will have a cable from the positive post of battery #2 to the negative post of battery #1.

I hope this makes sense!

I think you have battery #1 and #2 mixed up in your description.

Anyway like Wolfe stated, battery #1 will have - 6 volts for the - terminal for your charger, then the +6 volts is connected to the negative side of battery #2, and the + side of battery #2 is + 12 volts for the other battery charger terminal.

Think of the pair of golf cart batteries as a 12 volt battery in two 'easy' to carry 67 pound packages, connected together with a wire between the first and second battery half.

Much easier to install than a 8D 120 pound battery!

Yes you do want the battery off the cold floor. Put it on some wood or something, even a 2X 6 will work great.

Good luck,

Fred.

[landyacht318]

Get the batteries off the concrete floor, not because of the old wives tale that this discharges them, but that the colder concrete floor will cause more acid stratification and the strongest acid will eat the bottom of the plates faster.

I'd charge them full, then put them on the maintainer. Don't expect the maintainer to actually fully charge them.

[wolfe10]

Connect the positive of one battery to the negative terminal of the other. You now have a 12 VDC battery.

Hook up the 12 VDC charger to the to posts opposite the interconnect cable.

So, negative of battery one to charger negative.
Positive of battery one to negative of battery two (interconnect cable).
Positive of battery two to charger positive.