Maintaining battery via internal 12V Cigarette lighter plug?

[Alex T]

Hi All,

I've read a bunch about charging and maintaining batteries on the forum, but haven't been able to find any information on maintaining the battery from the inside of the trailer, via the cigarette lighter plug on the inside of the trailer. Does anyone do this?

We're new owners of a 1973 Trillium 1300, which has a group 27 12V (no converter / inverter). While I've read on other sites that this can be done (in a car, etc.) and a few battery maintainers come with the male cigarette lighter plug (I'm sure there's a more technical term for those plugs, is there any risk to the internal wiring by using it for this, rather than connecting directly to the battery?

We live on BC's wet coast and don't have a garage to do this in. Best way for us to keep the battery dry while maintaining it would be to keep it in the storage box and charge from inside the trailer, rather than exposing the battery and connecting the maintainer directly to it (and as the battery will off-gas I've read it's not a good idea to put the battery in the trailer to do this either). Thanks in advance!!

[Civilguy]

Originally Posted by Alex T

Hi All,

I've read a bunch about charging and maintaining batteries on the forum, but haven't been able to find any information on maintaining the battery from the inside of the trailer, via the cigarette lighter plug on the inside of the trailer. Does anyone do this?

We're new owners of a 1973 Trillium 1300, which has a group 27 12V (no converter / inverter). While I've read on other sites that this can be done (in a car, etc.) and a few battery maintainers come with the male cigarette lighter plug (I'm sure there's a more technical term for those plugs, is there any risk to the internal wiring by using it for this, rather than connecting directly to the battery?

We live on BC's wet coast and don't have a garage to do this in. Best way for us to keep the battery dry while maintaining it would be to keep it in the storage box and charge from inside the trailer, rather than exposing the battery and connecting the maintainer directly to it (and as the battery will off-gas I've read it's not a good idea to put the battery in the trailer to do this either). Thanks in advance!!

Alex,

I'm unclear what you mean by the storage box. A conventional lead-acid battery will always off-gas a bit of hydrogen gas during charging and the normal installations provide a vent for this.

The battery Tender Junior comes with a polarized plug and cable that can be connected to the battery. If you are describing a situation where the battery is in a tongue box or similar installation outside the hull, and you don't want to add new wiring through the hull, you could probably use the cigarette-lighter plug-set as this charger is limited to 3/4 amp.

These sockets would generally handle 10 amps or more when powering a lighter. However, many of the corresponding male plugs I have seen don't have the spring strength and contact area to provide a firm connection, so I would not try to run that amperage without evaluating the connection to see that it can carry the current without overheating.

It seems you could also tap into existing wiring inside the hull to connect the charger's battery-side cable. That would allow you to use the polarized bullet plug set. But, as connections are weak points in circuits, a direct connection to the battery as Dave notes below would be preferable.

https://www.batterytender.com/Batter...nior-12V-0-75A

[Dave Fish]

I agree with Civilguy but prefer to directly connect the battery maintainer. We have a similar setup with our Campster, no converter, just solar. Our battery is also in a box on the tongue. Since the Campster is stored in the carport, solar doesn't work well for maintaining the battery.

I have a battery maintainer wired direct with a disconnect plug. When we travel, just disconnect and go. The umbilical cord that stays attached to the battery is about 12" and has a weather cap. I have the same setup for my lawnmower battery.

They also have a similar solar setup that I found for about $25 US at a local auto parts store.

Whatever you do, get a smart charger that won't kill the battery.

[jokra]

Be very careful maintaining your battery through the cigarette lighter! I tried doing this with a small flat solar panel sitting on the dash in the van and the battery installed under the hood in the van. One time in winter, I tried this for a month and came out and found a dead battery which would not charge anymore. I suspected the solar panel charger but after several discussions with the distributer, he convinced me that the solar was working using clamps supplied connected correctly. If you rely on the battery power, use a meter telling you that it is working as you intend.

[Mike_L]

In my experience, a cigarette lighter receptacle is a direct connection to the vehicle/trailer battery. I've seen them with up to a 30 amp capacity. These connections may not be fused. They are often used as a power source from a vehicle, a trailer, an RV, a power bank etc. In the absence of booster cables I used "lamp cord" fitted with a cigarette lighter sized fittings on each end to charge a vehicle battery from another running vehicle using the cigarette lighter sockets on both vehicles. I have no use for an inverter in the back country so the one that came with my unit is still somewhere in a box. I have no idea how an inverter would figure into this situation?

[John in Santa Cruz]

the 'lighter' sockets in an RV are *NOT* meant for actual lighters, and are typically fused around 15A and not speced to carry any more power than that.

if I had an old camper that didn't have a power converter, I'd be seriously considering installing one... even my early 80s tent trailer had one.

[ehoepner]

NAPA sells a battery charger/maintainer that has a cigarette lighter plug. Have been using it on an emergency vehicle for more that a year.

[John in Santa Cruz]

Originally Posted by ehoepner

NAPA sells a battery charger/maintainer that has a cigarette lighter plug. Have been using it on an emergency vehicle for more that a year.

of course, those only work on vehicles where the sockets are powered when the car is off. all my european cars (1980s VWs, 80s/90s Volvos, Mercedes from the 90s), the outlets went off with the ignition, but on my ford f250 they are always hot.

[LarryB.]

Originally Posted by Alex T

We live on BC's wet coast and don't have a garage to do this in. Best way for us to keep the battery dry while maintaining it would be to keep it in the storage box ....

Why not just bring the battery indoors and put it on a charger?

Since space is limited at home, I have to keep my Casita in a storage facility which does not provide an electrical hook-up. A couple of months after I got my new-to-me Casita, I had a lesson-learned: the hard-wired propane detector had effectively depleted and killed the battery.

After replacing the battery, I acquired and installed an anderson disconnect using 6 guage wire & connectors on the battery side for use inbetween trips. Also, during the winter, I remove the battery from the Casita and put it on a trickle charger in my basement.

[jjtotten]

Originally Posted by Alex T

Hi All,

I've read a bunch about charging and maintaining batteries on the forum, but haven't been able to find any information on maintaining the battery from the inside of the trailer, via the cigarette lighter plug on the inside of the trailer. Does anyone do this?

We're new owners of a 1973 Trillium 1300, which has a group 27 12V (no converter / inverter). While I've read on other sites that this can be done (in a car, etc.) and a few battery maintainers come with the male cigarette lighter plug (I'm sure there's a more technical term for those plugs, is there any risk to the internal wiring by using it for this, rather than connecting directly to the battery?

We live on BC's wet coast and don't have a garage to do this in. Best way for us to keep the battery dry while maintaining it would be to keep it in the storage box and charge from inside the trailer, rather than exposing the battery and connecting the maintainer directly to it (and as the battery will off-gas I've read it's not a good idea to put the battery in the trailer to do this either). Thanks in advance!!

Although mine is a motor home I have been charging my coach battery through my cigarette lighter on the dash for years. I have a multi stage charger which has always worked.

[Alex T]

Hi all - thanks for the tips! As I couldn’t find one that had both the DC (cigarette lighter) connector and temperature compensation (wasn’t sure how important that was but figured since I’ll be doing it sometime near freezing, in our carport, it wouldn’t hurt), we got a battery tender plus.
While most maintainers are less than 2 amps, I figure why risk overloading the interior DC wiring, or having a bad connection.
Civil guys, the battery box on the tongue is one of those cheap plastic covers, so some air movement (but keeps it mostly dry).
With a solar maintainer, as one of you commented, it makes sense that if you don’t have enough light it’ll deplete your battery, so we weren’t considering that for maintainence.
Thanks again all!

[Mike_L]

Happy camping!