Charging/ Battery Question

Murph60 · 05-17-2021, 09:49 AM

New Rockwood A122S owner here and I am finding out all that I don't know. I picked it up on May 11th and our first trip will be over Memorial Day weekend. If the TT is sitting for only 2-3 weeks, do you put a charger on it, hook up your generator, just pull the negative cable or don't worry about that short a time frame.

BTW, if it matters, using 2 Group 27 AGM batteries.

Thanks

Blackrock · 05-17-2021, 10:02 AM

Depends on where you have it parked. I keep mine lugged in at home on a 30amp service. You can also plug into a standard 110v with an adapter and keep the batteries charged up through the converter.

ScotNH · 05-17-2021, 10:03 AM

I always either unhook the batteries to prevent them from draining, or plug my trailer in to keep them charging. It may be overkill, but I do that whether it’s 3 days or 3 weeks between trips.

Murph60 · 05-17-2021, 10:06 AM

Thanks. I am also thinking of installing a battery disconnect.

Murph60 · 05-17-2021, 10:13 AM

right now both batteries read 12.92 volts

CHICKDOE · 05-17-2021, 10:22 AM

You’ll get different opinions. Much has to do with whether electricity is available where you store it. If it is many will say just leave it plugged in. If electricity is not available it is best to ensure the batteries are fully charged and then disconnect them. Fully charged batteries without a load will last months.

Chewman · 05-17-2021, 10:38 AM

Interstate battery says 12.4 is 50% capacity on batteries, which you should not go below.
When you are running electrical things the batteries can drop to 11.9 volts and will bounce back up to 12.4 volts without a draw on them. So 11.9 is the lowest point you should ever drain them to. It is my understanding that if you do go below that you don't ruin the batteries, you just shorten the life. Once again this information came from Interstate.

I plug my trailer in about once a week to charge the batteries. I don't know if keeping them charged fully is best or letting them run down some and then charging them.

Your A122S looks like a great trailer, have a wonderful weekend trip!

Murph60 · 05-17-2021, 10:50 AM

Can I hook up my trickle charger with Battery connected to TT or do I need to disconnect before charging?

Thanks

TitanMike · 05-17-2021, 10:58 AM

Quote:

Originally Posted by Murph60

Can I hook up my trickle charger with Battery connected to TT or do I need to disconnect before charging?

Thanks

Just hook it up. No need to disconnect batteries.

Lead acid batteries will last longer and retain more capacity if kept fully charged. Battery maintainers are great for this task as they don't provide so much current that electrolyte boils.

Lithium batteries, on the other hand, prefer to be stored with a partial charge due to their chemistry.

kcmusa · 05-17-2021, 10:58 AM

Quote:

Originally Posted by Murph60

Can I hook up my trickle charger with Battery connected to TT or do I need to disconnect before charging?

Thanks

No need to disconnect, connect your trickle charger, no harm. It will maintain the battery.

Murph60 · 05-17-2021, 02:20 PM

really stupid question, but after it is charged and I disconnect the neg to prevent draw when it is idle, do I only need to disconnect the neg where the TT negative is connected to or do I have to disconnect both negatives in a two battery set up?

At some point I will be installing a disconnect.

CHICKDOE · 05-17-2021, 03:06 PM

I’m assuming two 12 volt batteries connected in parallel.

You should have a couple of jumper cables between the two batteries. One between the two positive terminals and one between the two negative terminals. Just leave those jumpers, no need to disconnect them.

Then you should have an additional negative cable that goes from one of the battery negative terminals to the chassis ground. Make sure you only have one additional negative cable connected to the battery negative terminal. This is the one that you want to disconnect!

Jim_74 · 05-17-2021, 03:15 PM

If you have electricity and a charger with a float phase, then leave them on the charger or leave the trailer plugged in. If not, make sure they are fully charged and then disconnect them once parked. Either a disconnect switch or remove the trailer negative connection (not the parallel jumper). If there is more than one negative lead (hopefully not), remove them all so there is no load.

Murph60 · 05-17-2021, 03:52 PM

Yes, installed in parallel. I have the TT negative to battery A, TT positive to Battery B. Neg to Neg jumper and pos to pos jumper. So I only have to remove neg from TT. Got it and thank you all.

Murph60 · 05-18-2021, 03:06 PM

One more stupid question. If they are connected in parallel, with house negative disconnected, if I hook up the charger to one battery will they both charge? Or do I need to charge each one separately. Sorry and thanks.

CHICKDOE · 05-18-2021, 07:55 PM

Those jumpers between the two positive terminals and the two negative terminals effectively turn the two batteries into a single larger battery, with twice the capacity. Leave the jumpers in place. Put the positive lead from the charger on a positive terminal and put the negative lead from the charger on the negative lead of the other battery.

Murph60 · 05-18-2021, 08:41 PM

Quote:

Originally Posted by CHICKDOE

Those jumpers between the two positive terminals and the two negative terminals effectively turn the two batteries into a single larger battery, with twice the capacity. Leave the jumpers in place. Put the positive lead from the charger on a positive terminal and put the negative lead from the charger on the negative lead of the other battery.

Thanks Much. That makes a lot of sense.

kcmusa · 05-19-2021, 07:26 AM

https://lh3.googleusercontent.com/pr...a266JDAYcWff6P

Wiring diagram

Murph60 · 05-19-2021, 01:20 PM

So I let the batteries rest, disconnected neg, to get a more accurate reading. It is at 13 volts, compared to 12.92 yesterday when connected. Is 13 to high to put a trickle charger on before I go camping next weekend? In other words can you damage the battery by charging if it is near or above 100%. Would the smart chargers take that in into account?

Thanks. Just wondering if is advisable to put them on the charger before we leave since there is no AC at this campground.

CHICKDOE · 05-19-2021, 02:19 PM

They appear to be full. I wouldn’t even bother with the trickle charger. They should hold their charge for months if fully disconnected. Since you appear to have power available for the trickle charger just connect the batteries back up the day or night before you leave and plug your normal shore power cord into the electric source and let your built in converter top them off. But this is just me. Others may have different suggestions.

You may also like: