to plug or unplug?

[ehoepner]

Originally Posted by Wayne Collins

A fully charged lead acid battery will not discharge as long as it is disconnected, and clean and dry on top. Nor will it freeze.

A fully charged battery will discharge in about two months. Fact of life for a lead acid batteries. If there is dirt on top of the battery the discharge will be less than two months.

[Glenn Baglo]

From Trojan battery site:
1. What is the shelf life of my battery?
The limiting factor of battery’s shelf life is the rate of self-discharge which itself is temperature dependent. VRLA batteries will self-discharge less than 3% per month at 77º F (25º C). Flooded batteries will self-discharge up to 15% per month at 77º F (25º C). VRLA batteries should not be stored for more than 6 months at 77º F (25º C) without recharged. The specific gravity or voltage of flooded batteries should be monitored every 4 – 6 weeks and should be given a boost charge when they are at 70% stat of charge (SOC). When batteries are taken out of long storage, it is recommended to recharge before use.

[John in Santa Cruz]

a handy alternative is a 'solar battery tender' of 10-15 watts. I keep one on my diesel truck that I only drive once or twice a month. it came with an SAE pigtail you can permanently connect to the battery, then just plug the panel in, and put it somewhere where it will get suffficient sunshine. mine is the 15W model, it outputs as much power as my classic Battery Tender Jr, about 1.25 amps, and has a smart test-bulk-absorb-maintenance charge cycle controller.

[Alben]

I did an experiment last year when I put my camper in storage last year. I disconnected my fully charged battery November 1st. I left it sit, never charged it, but measured the battery voltage with a multimeter every month. Come May 1st, I took the last voltage measurement, 12.45 Volts, which is a state of charge of about 80%. So in six months it only self-discharged 20%. The freeze point of a 12V lead acid battery at 12.45 volts, 2.075 volts per cell, specific gravity 1.225, freeze point -40F (-40C).

My findings correlate to information found on the web that a lead acid battery has a self-discharge rate of 40% per year, and low storage temps actually increase the battery life and slows the self discharge rate.

If your battery is self-discharging faster than that, then the battery is probably due for a replacement.

[computerspook]

OK I generally run my vent on low. Seems to keep the inside dryer. So I kind of need power. I have already replaced the horrible converter that came with my scamp with one that has a lot more power and also is a 13.8 volt unit not a 15 volt like the one I had was. So it is easy on the battery. But if I am not camping, about once a month I unplug and let the battery discharge some and then replug. Seem to be good battery life.

[tom w]

for my trailer I got a timer to plug the cord. I set it for 2 hours at night it keeps the battery charged

[computerspook]

Originally Posted by tom w

for my trailer I got a timer to plug the cord. I set it for 2 hours at night it keeps the battery charged

Never thought of that. Will have to look into that. Thanks

[gordon2]

Originally Posted by tom w

for my trailer I got a timer to plug the cord. I set it for 2 hours at night it keeps the battery charged

I'm using this one. Its out of stock but there are many others like it.
It allows on/off on a daily, multi-day and weekly schedule. For example you could set it to run your camper and charger for 8 hours once a week.

I'm using it on my Scamp this month to power the camper at night, which has Christmas lights around it plugged into the exterior outlet on the camper.

[snuffy2]

I as most humans are creatures of habit. Disconnecting the + side first is a dangerous habit to start, also bad advice to give if the person recieving the advice really has no mechanical/electrical knowledge.