FLYCT

I've got a car that's been sitting for the last 6 weeks or so with only some short periods of engine run. The initial Battery voltage at rest was measured at 12.0 volts. A resting voltage of 12.0 volts equates to about a 25% SOC, State Of Charge. A battery at 100% SOC normally will read about 12.6 v resting and fully discharged it will read about 11.3 volts.

Resting voltage is taken after the battery stabilizes at least 30 minutes after being removed from a charger.

After 12 hours the charger output voltage was up to 12.3 v and now after 24 hours it is up to 12.6 v and climbing with the charger connected, not resting. I measured the charger current at 630 ma, (0.63a) The Charger has not gone into float mode. It probably will take another day for the Battery Tender JR to go into float mode at this rate. This rate is very safe.

Our batteries have a rating of about 100 amp hours. At 60% of rating they are essentially fully discharged. Doing some basic math a fully discharged battery would take about 80 hours to reach full charge at 0.75 amp(750 ma) charge rate. 60ah / 0.75a = 80 hours to fully charge or 3.3 days. A healthy 25% charged battery should take about 2 1/2 days to fully charge with a Battery Tender JR.

JR

EDIT: I found a nice Excel Spread Sheet showing State of Charge for a 12 volt battery at different temperatures http://jgdarden.com/batteryfaq/SoC.xls

JR

williakz

Very helpful, Fly. Thanks

wchain

I'm assuming you guys are doing the battery tender on you ls460 because you're like me, and your 460 is a weekend driver/garage queen?

FLYCT

I started using some sort of smart battery maintainers on private aircraft and motorcycles. Batteries were not lasting and replacement became expensive, not to mention inconvenient when plane wouldn't start.

I usually kept an airport car parked at airports we frequented. Where power was available I kept a Battery Tender JR connected and where there was no power available I used a solar charger. The solar chargers I used were the ones that Volkswagen used to keep batteries topped off while they were being shipped to the US. http://www.beneteau235.com/vw_solar_panel_f235.htm

Today I use battery tenders regularly on any of our cars when it's expected to be parked for more than 2 days or so.

Batteries will self discharge about 1% a day on their own. Add the 50 ma of parasitic drain from newer car electronics and it's not unusual for a battery to be dead in as little as 30 days with the car parked. Allowing lead acid batteries to discharge causes sulfication which can lead to dead cells and early failure.

JR

wchain

Point well taken.

I have a company car, so the other 4 cars never get driven. I have a tender jr on the 78 Land Cruiser, but I just bought 3 more tender Jr for the other cars. Ironically the mustang was dead yesterday morning. The V1 was left plugged in for two weeks.

BTW, what kind of planes do you fly?

FLYCT

My wife and I both have been private pilots since the late 70's. We've owned and flown several different aircraft over the years. Our last plane was a Cessna 182RG. The plane we had the most fun with was an aerobatic Citabria. Citabria is AIRBATIC spelled backwards.

Currently we are without a plane since we sold the 182RG last summer.

JR

FLYCT

UPDATE;

Finally, After a full 3 days the charger went into absorption mode with green flashing light. Measured battery voltage is 14.2 vdc.

Supposedly the battery is now at 80-85% charged. The absorption mode maintains steady voltage and current should decrease slowly until either the battery reaches optimal charge threshold or the absorption timer times out. Then the charger should go into float mode where voltage should maintained in the 13.5 or so range.

I'll report back when it goes into float mode with readings.

UPDATE 2;
After several hours I finally got a SOLID GREN LIGHT = Float mode
Measured Float voltage = 13.04 vdc

JR

Lexus4me

I went purchased a battery ender plus because my battery went out. The car has been sitting there for 3 weeks and I keep going in and out of the cars doing some cleaning and LED mods. When I see the security red blinker stop blinking on both door is when I realized the battery might be completely out.

I notice when the car engine is not on and I turn on the parking light to test the LEDs, the car will have a one time sound coming from the engine bay. Is that sound relating to power been used when the engine is off?

I though maybe the battery tender plus might take at lease a day to get solid green, but seems like it become solid green within two hour. Orange light of off, just solid green. Hope I don't have a dead battery.

Haven't turn on the engine yet because my grill and engine covers are still on the floor.

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2007 LS460

Lexus4me

something is draining the power or the battery is not holding much charge because next morning I see the security red blinker stop blinking again. I am thinking to pull out the battery to get it tested. I read our car can keeps memory for certain period of time and I am not sure my battery was out for how long.


Is it safe to use the battery tender plus as a power source to the car while I removed the battery to get it test at the store? because sometime they say come back next day for the test result.

derpie

I think you would need a dedicated power supply to do that the charger wouldn't have enough amperage to power your car.

jmcraney

You will likely get some opinions from others that differ from mine but maybe this will get the discussion going.

I don't think you should be concerned about keeping power on the car while the battery is removed and in my view I think that it is risky to power the car from a source, other than the battery, and a risk not worth taking just to preserve the radio presets and the TPMS benchmarks.

A battery can only be properly tested when it is fully charged and getting to a full charge can take many hours for a battery that is fully discharged, thus the "come back tomorrow" at the battery store.

If your battery is defective, or near the end of its life, as indicated by testing then a new battery will likely solve your problem.

If your battery tests "good" then let us know as there is another cause to consider.