roadfrog

Fair enough. We all have our varied comfort levels.

jmcraney

I think you have provided some very good advice. Although leaving a "battery tender" connected is pretty low risk stuff, it is a risk not worth taking. New batteries are commodities and a good one can be had for less than $200 so extending the normal 4 year life for a few months by using a supplemental charger just doesn't provide much of a payoff. The warranty is the same whether you shorten the life by letting it sit idle for extended periods or keep it top-charged and make it last forever. Unless it is an emergency vehicle just disconnecting one terminal, if you are a DYIer, is a better choice.

The risk with supplemental chargers range from failure of the charger, which is low, to failure of the chargers power source from power line transformers caused by storms, electrical and wind, automobile accidents and all manner of things, that might propagate into your car's electrical system via the "tender" and damage it, all very unlikely but not a risk worth taking. There's just not much to be gained and not worth giving it much thought in most situations.

I think that leaving the battery connected, without a supplemental charger, while the car is idle for extended periods would be Ok. If the car starts, drive it for a while to recharge the battery and then have the battery's "state-of-charge" measured and if it is in a normal range then you are all set for a while. If the car will not start after being idle for extended period then fully charge the battery with a charger, measure the state-of-charge, and if it is in a normal range you will be set. Any time the state-of-charge is low after the battery is fully charged then it is time for a replacement. State-of-charge can be easily measured with an inexpensive voltmeter. You can also determine the state-of-charge using an inexpensive hydrometer that is available from auto parts stores.

roadfrog

My only concern with a drained battery is when it sits outside in freezing temps and the battery has drained. That will permanently destroy the battery. The better option would be removing the battery and placing it in a warm garage etc.

jmcraney

You guys in the "Far North" use heater blankets on your batteries? You have much different considerations than us folks way down here. Using a battery heater seems like a low risk approach if your climate involves extremely low temperatures.

swfla

iTrader: (1)

I'm in FL and had spent most of my working life around big boats/yachts that have multiple lead acid batteries on board. Besides starting and running the engines they are necessary to run automatic bilge pumps that operate on a float switch 12v. There is a battery charger on board that has the capability of putting out 20-50 amps typically and as little as 0 amps as the batteries require. The boat is plugged into shore power. Many of the boats are gasoline powered with the fuel tanks located in the engine compartment along with the batteries and the charger. The charger does have technology to prevent sparking which could cause an explosion if gas or battery fumes were to build up. Point is everything is plugged in 24/7 365 days a year. Even when the boat is operating, if equipped with an a/c generator, the battery charger is on. Is this a fair comparison? I'll leave it to you...

johnnyreb

^^THIS! I have a Battery Tender on my 911 & i've Never had a Problem with it getting Hot, like RF said this is what they're FOR! I can't believe you Don't come back at all during the whole 6 months (i know i couldn't go that long without driving my Babies, Lol)! Why do you Not just drive it to Florida, after all it IS a Lexus (just the Best Road Trip Car Made) & it'd be Nice to Cruise around Fla. in Luxury!

roadfrog

LOL. The OP's weather is far more severe than ours here in the Pacific Northwest (near Vancouver and Seattle. We rarely see snow let alone freezing temps...though it does happen. The "Far North" is at least a four day drive from here.

johnnyreb

IF you Don't want to go thru all these things, the Easiest thing would be to let one of your Friends or Neighbors just check on Everything for you & crank your car from time to time & maybe drive it to the mailbox & back! Do any of you Not have ANYBODY you live next to you can Trust? This must be the First time you've did this, IF NOT what did you do the times Before?

jmcraney

I am not sure what comparison you are making. Unless this is a submarine you are talking about, I would think that the batteries are for starting the engines, (not running the engines) and providing a limited backup power source for the bilge pumps in case the engine driven generators fail and the boat is away from shore based backup or the engines are off and the shore based power source becomes unavailable. Most cars are equipped with engine-driven generators, like most boats, that power all the cars electronics while the car is running and recharge the battery to a maximum state-of-charge to restore the battery for the charge that was used to start the car. When the car's engine is not running the car's battery can provide a reliable source to operate the car's accessories for a limited time and keep the car's alarm system available for a very long time. I suppose that if you wanted to camp in the car you could connect a battery charger to the car's battery and connect the charger to an AC power source and do most anything in the car, sort of the equivalent of a shore connection for a boat. In both cases the batteries provide a high current/limited duration source for electric starter motors.

swfla

iTrader: (1)

I took the long way around to make the point that batteries (under much more hazardous conditions) can be hooked to a charge maintainer for long periods and nothing bad happens.

jmcraney

I am not trying to be a wise guy and this is not sarcasm.

How many and what sort of problems do you think you would have had if you did not use a battery tender, other than extending your battery's life and how many months do you think you extended its life. Keep in mind that the battery tender will not prevent battery failures that are caused by latent manufacturing defects and poor maintenance that allows the cell plates to become exposed to the air.

jmcraney

I think the point you are making, perhaps inadvertently, is that it is a risk worth taking, in the case of the bilge pumps.

roadfrog

Everything comes with risk. In this case, it's one in a million. Which is precisely what insurance is for.

jmcraney

I try not to take risk in which the risk/reward ratio does not support the risk. Insurances underwriters have deductibles that shift that ratio to be in their favor.

DJWLDW

Johnnyreb

The DW has only driven the LS 4 or 5 times by her self in 10 months. Can you imagine the rash of $%^& I would catch if I left the keys with a neighbor and said go ahead and take her for spin every now and then while I am gone. I have almost 48 years invested in this marriage plus 17 years in hot pursuit so that is not likely to happen.

Dennis