Open/close to maintain 12 V battery constantly???

I have a 2005 TM 2720SL. Every time I return from camping I have to reopen my trailer and remove the 12 V battery (so I can connect it to the battery maintainer), then close the trailer. When I'm ready to go camping again I have to open my trailer again to put the battery in, then close the trailer for towing. Unsafe to stowe battery (12 V gel) in my SUV while towing. Can't connect battery maintainer while battery's in closed trailer, needs ventilation, etc. Any way around all this opening, closing, installing, uninstalling battery? Thanks, Juniper

[ShrimpBurrito]

I have not heard of anyone else that does this. Major PITA.

I keep my battery on a charger 24/7 on my 2000 2720SL while closed. The battery box is vented, but I'm not sure how effective it is because the box itself is not sealed very well. Atmospheric hydrogen (diatomic, H2) is among the smallest molecules on earth (much smaller than atmosphere oxygen and nitrogen) and thus to seal it, it has to be much better than even air tight. My point is that there likely are no RV-grade battery boxes sold anywhere that are hydrogen-tight. Fortunately, the same goes for the battery compartment, so my theory is that any hydrogen leaks out of the box and out of the compartment into the atmosphere. So far, so good.

If you believe that theory, and your TM has a 3-stage charger built into the converter, the only thing you need to do when you get home is plug the TM into the wall and leave it there 24/7. If your converter does not have 3-stage charging capabilities built-in, you can install one yourself (about $125). Alternatively, or if your TM shells cover the pigtail access hole like mine does, you can do what I did:

• install a low-current (I use 2A) battery charger inside the battery compartment and connect it directly to the battery (with a fuse). Using a low-current charger should help reduce the risk of generating hydrogen.
• drill a hole in the floor of the compartment just inside the door such that it enters the rear bumper.
• run a short piece of tubing through that hole, and run a wire through the tubing (the tubing protects the wire).
• on the end in the battery compartment, put on a single outlet. You will plug the charger into this outlet. On the other end in the bumper compartment, put a plug.
• You can now plug in this charger with the shells down.

Dave

[ThePair]

Gel batteries are sealed, and shouldn't under most conditions expel hydrogen. This is part of why I got one, the other reason being no water level issues.

So, you should be able to safely just plug in your converter if it's 3-stage, and be done with it. But, I don't think the 2005's had 3-stage converters, so an upgrade may be in order...

[ShrimpBurrito]

AGM batteries also should not release hydrogen under normal charging conditions as well. They're about 2x the price as flooded lead acid.

Dave

I don't have a three stage, I use a "Batteryminder Plus" maintainer. I'm not knowledgeable about batteries and maintainers or three stages, any idea if it's ok to keep my gel battery plugged into the Batteryminder (maintainer) 24/7 WHILE THE BATTERY'S IN THE COLLAPSED TRAILER, the battery compartment does have a vent.

I did not check your specific battery maintainer, but most have a max output of one amp, then drop off to mAs once charge is reached. At these rates it is difficult to generate enough hydrogen to worry about, in addition the TM is not that air tight when closed. I run a battery tender on mine 24/7 with no problems. Battery tender sits under tm in small enclosure to keep it dry. I ran the trickle charge cord thru the shore power opening.

[ZekenSpider]

Originally Posted by Juniper Spring

I don't have a three stage, I use a "Batteryminder Plus" maintainer. I'm not knowledgeable about batteries and maintainers or three stages, any idea if it's ok to keep my gel battery plugged into the Batteryminder (maintainer) 24/7 WHILE THE BATTERY'S IN THE COLLAPSED TRAILER, the battery compartment does have a vent.

My experience with a closed 2010 3326K (equipped with a WFCO 55 AMP three stage converter/charger) has been very good. No evidence of hydrogen build up or of battery water loss.

I have plugged my 30 Amp 120 VAC camp ground pigtail into a 120 VAC outlet at my storage yard for several years (since 7/29/09). It remains plugged in as long as it is in storage. I have a battery monitor installed and have mounted it so that I can periodically observe battery voltage and charge current. This charging process works well and I see no evidence of battery damage.

If you do not have a converter/charger that will idle down to "maintenance mode" i.e. trickle charge, you can connect the "battery maintainer" type of charger to the Bargman connector +12VDC and Ground pins and charge or maintain the battery from the hitch connector(TM to TV) even if the TM is folded. You can also measure the battery voltage at the same point. Never let that voltage drop below 12.0 VDC before recharging. When fully charged (on the maintainer), it should rise to 13.2 VDC or a little higher and stay there. When the maintainer is removed (if you decide to), the voltage will slowly drop (over a month or so) and should be recharged before it drops to 12.0 VDC

Probably the safest approach would be to make a special connector that would allow you to plug your TM Bargman into a mating connector that has pigtail leads that you can attach your charger alligator clips to. Just be sure to observe correct polarity.

Attached is a schematic of the 7 pin Bargman attached to your TM.

Hope this helps,

Jerry

Wish I was as knowledgeable as you...very thoughtful response, thanks so much.

Jerry
Most computer controlled battery maintainer units recommend not extending the connection to the battery as it meters the charge current based on the voltage measured at the charger end of the circuit. The introduction of a Bargman and the wiring in the TM would introduce drop and disrupt the performance.

[ZekenSpider]

Originally Posted by rumbleweed

Jerry
Most computer controlled battery maintainer units recommend not extending the connection to the battery as it meters the charge current based on the voltage measured at the charger end of the circuit. The introduction of a Bargman and the wiring in the TM would introduce drop and disrupt the performance.

Generally true for multi purpose chargers (especially Bulk and Absorption mode) but not really a problem at the low currents utilized by a dedicated maintainer type charger such as the Battery-Tender-021-0128-Plus-Charger (1.25 Amp max but only 0.010 to 0.03 Amps during maintenance). Voltage drop becomes a problem only at higher current charging.

If the battery is located at the back of a 20 ft TM, the voltage drop from one end of a 40 ft #12 gauge wire run (20 ft. each way) at .03 Amps is less than 0.01 Volts. Even at 1.25 Amps the drop is only 0.08 Volts. If the wire is #10 gauge (like it is in my TM), the 1.25 Amp drop is only 0.05 Amps.

IMHO this is not a problem for any one using the 1.25 Amp Battery-Tender-021-0128-Plus-Charger. It is a problem for someone using something like the DieHard Microprocessor - Controlled Battery Charger and Tester, 80 Amp Engine Start, Sears Item# 02871225000, Model# 71225.

Respectfully,

Jerry