What battery tender would you buy?

When the winter comes around, I've already decided that I must not drive it so that the road salt will not have its way with the car. Or at least 'more' of its way with the car...

I do plan to drive the car until the fuel tank is almost completely empty before storing it.

Starting it in storage won't be a real practical thing to do. I'd rather not take it out of the garage at all. I could just disconnect the battery, but it will still discharge itself just sitting there. I'd like to keep the battery up so that when the weather is nice, I can get right back to driving.

So the questions are...does anyone here use a battery tender for a similar purpose, and if so, what brand/model would you recommend?

The original "Battery Tender" is impossible to beat and very reasonably priced.I always stored my
toys with a full tank of gas and the correct amount of "Stabil" conditioner.Have never had any problems and the charger only charges when it senses the battery voltage dropping below a safe level!

I've got some cheap ones from Wal-Mart that I use for the boat and the motorcycles. It's their house brand, only has two lights, orange one for charging, and green one for charged. Have had all three over a year and no issues.

I just bought the Ctek one this afternoon. It is supposed to be very good. I'm looking forward to trying out its desulphication feature.

I picked up a 12 volt solar cell panel, and have a plug for the cig lighter on it. I just lay it in the car with it plugged in (outside). I have had it in the car for about 6-8 months, and it is doing a nice job. The car is always ready to start, even after sitting for a month.

Fred Kiehl wrote:

I picked up a 12 volt solar cell panel, and have a plug for the cig lighter on it. I just lay it in the car with it plugged in (outside). I have had it in the car for about 6-8 months, and it is doing a nice job. The car is always ready to start, even after sitting for a month.

We have those on the deer feeders at the ranch. Neat toys!

I use the Battery Tender Jr for my Impala SS as its kept on a garage and some times does not get driven for weeks.. It always starts...

http://www.walmart.com/ip/Schumacher-SpeedCharge-12-Amp-Battery-Charger/13005744

Charged a DEAD (4volt) battery enough to start in about 15 minutes. Smart enough to leave on for the winter without killing the battery.

Battery Tender - CTEK - DURACELL (Yup I said Duracell http://www.duracelldirect.com/part_804-0027-07.aspx )

are they top three out there on the market

Also been using a 14 inch solar panel on my buick.Car always starts and this charger shuts itself off to protect the battery from overcharging.This is the first solar charger that can keep a
Optima battery at its peak charge level!

A battery maintainer is best for long term storage, especially for an AGM or gell cell, but also for LA batteries. Chargers tend to overcharge because they have relatively constant current output but somewhat variable voltage. Trickle chargers do the same thing, just slower.

Maintainers have circuitry to monitor the battery condition and adjust the voltage output as required. The voltage control is the key element in preventing long term sulphation.

Small solar panels plugged straight into the lighter socket are chargers, however since they don't do much at night they are less likely to overcharge/sulphate a large battery. Almost by accident, the nightly pause allows voltages to stabilize. As Flasheroo aludes, some larger solar chargers have maintenance circuitry either built-in or available as an in-line accessory. I'm not aware that any have a desulphation function (high voltage or high frequency), but they could be out there.

The ideal voltage differs from on technology to another and is also temperature dependent. I did not know this until I connected an Opti-mate III to my motorcycle AGM battery over the winter and found the capacity greatly reduced in the spring. Opti-mate advertised the charger as suitable for both LA and AGM batteries. What they did was to split the difference between the two, maintaining a voltage that was actually too high for a Gell, still too high for an AGM and too low for a LA. It maintained that voltage even through the -40° temperatures we experience here in the winter.

The difference is not much at first glance. At room temperature (eg: 70°F) typical maintenance voltages are 13.4 V for a gell, 13.5 V for AGM and 13.9 V for LA. This charger put out 14.6v as I recall. So at room temperature, this approach is probably fine and those in moderate climates would not have a problem. However, the value should be reduced by 0.023v/°C so in midwinter, the charger was over-voltage for my poor AGM by almost 1.5 volts. That same Opti-mate has a "desulphation" mode where it applies a short burst of over 20v to "break down" any crystals if the initial resistance is too high, but I saw no evidence that it helped to recover a sulphated battery even after repeated attempts. I have since replaced that maintainer with a West Bend unit that is temperature compensated and it seems to do a much better job on the AGM battery in winter.

I have not had any appreciable success with any desulphation technique. I've tried chemical additives, I've tried desulphation chargers and I've tried an electronic desulphator. The latter seems to prevent further sulphation but I find no evidence that it is capable of reversing sulphation, even over months of use. But my sample size is small: this far I have only tried it on a LA motorcycle battery and a deep-cycle marine LA battery. Connected for 6 months, I measured the results with a carbon-pile load tester but saw little or no restoration of the battery capacity. OTOH, I saw no further deterioration either, which I would have expected.

So when looking for a battery maintainer, I'd look for one with a performance curve designed for the technology to which it will be applied. "Universal" chargers should have an actual switch or software program rather than rely on averaging or trying to detect the battery technology electronically. And in cool (or hot) climates, it should be temperature compensated. IMHO, those that trigger a short high-voltage desulphation cycle based on initial resistance are probably selling snake oil, but those that use a high-frequency pulse during all charge phases may actually be of some limited benefit.

I use a desulphator and a small solar panel to maintain the LA starter battery for our backup generator. The combination seems to work well.

Anybody remember what we were talking about?

Flasheroo wrote:

Anybody remember what we were talking about?

Battery tenders.

While the suggestion is neat and would certainly have its uses for other vehicles in my "fleet", the solar panel isn't terribly practical for a car that will be living in a garage with one window far away from it. I could make an extension cable, though it is likely to be a trip hazard.

I'll bet you think I'm joking when I say "fleet" as well.

I'll have to stick with the line powered battery tender options, and it's looking like either the Battery Tender branded unit or the Wal-Mart option (which I think I've seen before) will be the directions I take.

81X11 wrote:

Fred Kiehl wrote:

I picked up a 12 volt solar cell panel, and have a plug for the cig lighter on it. I just lay it in the car with it plugged in (outside). I have had it in the car for about 6-8 months, and it is doing a nice job. The car is always ready to start, even after sitting for a month.

We have those on the deer feeders at the ranch. Neat toys!

You have a RANCH and you FEED the deer and have NOT invited your fellow wagon geeks hunting? Who are you anyway!???!