The Battery tender website advises owners anytime you are charging a battery there are risks involved and you should check on the state of your battery and Battery Tender's operation regularily. They state things can sometimes go wrong, that batteries do fail and chargers can sometimes fail but they don't tell you how to check on it or what to use.

Slightly long story with history and description of issues follows which helps sets the stage for the question at the end:

This is the second battery I lost while being connected to a Battery Tender Junior. I have a C4 and C5 both of which are garage queens; neither is driven much but both have Battery Tender juniors connected. Both also now have new Delco 7-Year Professional Series batteries and I just lost one of the new batteries after losing the original in the C5 a couple years earlier. Some history and background.

The C5 is a convertible I bought new which has only 2000 miles and is now on its second battery. About a year after I bought it the battery was too low to start the car one time so after checking in here at the forum for advice I bought the Battery Tender. I picked the Junior because of its lower 750ma rating so as to avoid higher charging rates; I realize this was "atom smashing" but it's what I did. None-the-less the Junior should have been more than enough to maintain that battery. When I first connected it the red indicator light stayed lit for two days before switching over to green but it stayed green after that for another two years. Then one day I tried to start it and had a low battery again. The original battery had removeable vent covers on top so I was able pry them off to check the electrolyte level and the battery was completely dry! I filled it back up with distilled water and the battery did recharge but I thought it prudent to replace the battery so I bought a new 7-Year Delco and a new Battery Tender Junior also.

Shortly after that I finished my C4 project car and installed a new 7-Year Professional Series battery in that one also. I connected the first Battery Tender Junior to this one and thought all was OK but with-in a year I lost the new battery, no start... dead. The new batteries are glued and sealed with no access provided for checking the water level so we are done with this one I guess. One thing I did notice is I don't have a true green light anymore on that Junior as the LED indicator lights up more of a yellow-green. More yellow than green. I suspected it was just a defective LED and decided to go ahead and use it but it might actually be a failure of the electronics. Had I been sharp enough to connect an ammeter and a voltmeter in each circuit to measure charging rate I could have monitored the Battery Tender's operation as it switched modes and might have been warned of an over charging condition or output from the Battery Tender Junior that was too high.

Comments?

Do you know of anyone who offers a slick little voltmeter/ ammeter hookup to compliment a Battery Tender connection to help an owner keep a more informed eye on things?

 

I've seen three Battery Tenders, Jr and regular, overcharge batteries. They were defective at purchase, usually, but one became defective after some use. Even the ones that aren't actually defective do, in my opinion, overcharge the battery before they go into float mode or whatever you call it. I admit I don't know much about batteries and electronics, but I see no need for a "float" charger to take a battery up to 14 volts before it kicks off. Why don't they take the battery up to 12.8-13 volts, no more, then hold it about there?

I no longer trust these chargers. I still use one (a Jr) on my C5 because the fifth-generation Corvette quickly drains a battery even if there is nothing wrong with the car, but I only hook it up every 10 days or so, then disconnect it when the green light starts flashing(before the solid green light appears). If I had any money, I'd try a Ctek. Anyone know to what level they take a battery under charge?

 

Check out their faq section...
http://batterytender.com/resources/f...sked-questions

Specifically...
How is the BATTERY TENDER PLUS charge different than a trickle charger?

QUOTE:
"The Battery Tender Plus battery charger delivers 1.25 amperes during bulk charge mode, holds the battery charge voltage constant at 14.4 VDC during absorption charge mode until the battery charge current drops to 0.1 amperes at which time it then automatically switches to a float charge mode. During float charge mode, the output voltage of the Battery Tender Plus battery charger is 13.2 VDC, which is well below the gassing voltage of a lead acid battery. This keeps the battery topped off, while minimizing any detrimental effects to do gassing. The Battery Tender Plus battery charger is able to perform these complex switching functions because its electronic circuitry is controlled by an on board microprocessor.

Although they often appear to be a better economic choice for the typical consumer, trickle chargers do not have the advantage of sophisticated electronic control. Therefore, as they allow the value of charge current to trickle down to what appears to be safe levels, the output voltage of the charger rises well above 15 VDC, sometimes even going higher that 16 VDC depending on the charger type and the battery that is connected to it. Either voltage is well above the gassing voltage of a lead acid battery. If the battery remains connected to this high level of voltage for an extended period of time, even less than 1 day, extreme damage can be done to the battery. What appears to be a cost savings for the charger may actually cost several times the charger price in replacement batteries."

From CTEK...
http://www.ctek.com/EN-US/consumer/mus-3300.aspx

QUOTE:

"Model MULTI US 3300
Input voltage 100–120VAC, 50–60Hz
Output voltage 14.4V/0.8A, 14.4V/3.3A, 14.7V/3.3A
Charging current 3.3A
Ripple 50mV rms, 0.13A
Ambient Temperature -20°C to +50°C, output power is reduced automatically at higher temperatures.
Cooling
Charger Type Four step, fully automatic switch mode with pulse maintenance.
Batteries 12V lead-acid batteries (Wet, MF, AGM, Calcium/Calcium and GEL)
Battery size 1.2 -120Ah
Dimensions (L x W x H) 165x61x38mm
Insulation IP 65
Weight 0.5kg"

 

I left a Ctek one one of my batteries all last winter and it was still full when I checked it. It's back in storage with the charge on it again. I'll try to stop by and check the battery levels again. I actually abused that poor battery by letting it go dead once and almost dead a second time yet it was starting the car fine in the summer. I had expected it would be garbage last spring.

The manual says they change from charging to maintain mode at 12.9V and that the maintain mode gives a pulse to the battery every time the voltage drops. So, this doesn't tell you exactly what they do but they maintain with voltage pulses instead of a constant voltage.

Peter

 

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I leave mine connected with the hood open all winter, every time I walk in/out of the garage I can see the status LED.

 

I will probably get something like the item pictured below which reads DC amps. This way I can keep an eye on the Battery Tender to be sure it's not overcharging. Also have to get a new $150 Delco Professional series battery to replace the one the defective Battery Tender killed.

 

Yup, continuing to use something that has failed you more than once sounds like a great plan.

Peter

 

I never leave any charger on for longer than 24 hours (and that is only if the battery requires a full charge). Have seen too many damaged batteries due to over or undercharging. Note that I was a project engineer in the Ni-Cad, Ni-Mh, and sealed lead acid battery charging industry.

My 2 battery trickle / maintenance chargers are small (.75 to 1 amp) float type chargers hooked to a common clock timer that charges each vehicle (C5 and a C1) for 30 minutes per day. This is sufficient to maintain the battery charge, and prevent the very common overcharge and subsequent damage that is so prevalent with these types of chargers. I really think the charger manufacturers are in cahoots with the battery makers!

I have been using this method for many years (on several various vehicles), and my batteries always last past the typical 7 year life. Last battery I replaced was in the 62 Vette last year, and it was purchased new in 1999 just after I bought the Vette. I replaced the battery last spring due to a small acid seep at one of the connections, but it was still holding a good charge.

Even with the C5 memory drain, the .75 amp for 30 minutes is more than sufficient to maintain it's battery charge (this putting approx. .3 amphour back in the battery, which far exceeds the C5 electronic memory drain). The C1 has a separate security system (which has more parasitic drain), so it gets the 1 amp rate charge for 30 minutes.

Don't trust that the float chargers "set" points match all the different various battery chemistry variations available for our vehicles.

Plasticman

 

I was using two Tenders. I wish I had kept the suspect Battery Tender for testing in order to understand how it failed but it was tossed out and will be replaced. Getting DMMs (voltmeter and ammeter) to monitor charging rate and to see if they go into float mode is because I no longer have confidence in them. If one failed it is possible another will fail at some point. Don't forget... it worked fine for a few years before it took out the first battery. I didn't suspect the Battery Tender then because the battery was four years old.

I posted a Battery Tender thread here a couple of years ago when the first battery went away and the first question repeated many times was "how old is the battery?" Everybody advised, just get a new battery... that my problem was probably a bad four year old original battery.

So this then is the purpose of this thread, to raise awareness of possible Battery Tender failure. All we have to go on with a Battery Tender is a little LED on the front that changes colors to tell us it is working OK. Other than that we don't know what they are really doing. Maybe there are othes out there with Battery Tenders connected doing the same thing and the owners don't know.

I like Plasticman's timer suggestion! It is the only fail-safe suggestion I have received so far. Thank you Plasticman!!

 

Well, I'll say this, I also keep my bike on a tender all winter and that battery is 6+ years old now-I'm amazed how long this battery has lasted on the tender-I may just toss the battery next year just because of it's age.

 

I have also had problems with the Battery Tender Plus. Bought one about a year after buying my 02 vert (new). One day leaving the dentist office my battery blew up (didn't suspect this to be anything but my foot raising the clutch pedal before the motor cranked and off the interlock switch under the clutch pedal). I'm trying to convince myself this is what happened because the battery imploded before the motor cranked (didn't break the case but no current to the car anywhere). Also, can't blame this on the Tender (but the original battery was only three years old). Bought a new AC Delco battery and about 2 1/2 years into its life I noticed the LED on the front of the Tender was either not on or when it was on was a weird color. I could still hear the hum of the Tender so I was hoping it was still working. Well about 4 months later the second battery died (didn't have problems cranking over that period but sometimes it would crank slowly). I bought a new AC Premium 7 year battery this time because the distributer said they were made by a different company than the previous batteries and much more reliable. With no confidence in the Tender I haven't used it since replacing the second battery. But since I don't drive the car much I just ordered another one. Glad you started this post. I like the idea Plasticman is recommending and will use this on my new Tender.

 

I checked my boat battery with the Ctek on it. The voltage was right at 13.1V when it switched from the charge to the maintain mode.


Good to read. I've seen more than 1 thread about those chargers failing and I'd personally never own one. I wouldn't buy another as a replacement either if I were you. Don't keep supporting a company whose products has already cost you 2 batteries.

Peter

Peter

 

I agree. Like many things with electronics and integrated circuits these days reliability is not as dependable as it should be. Here we have a $50 item that seems like a great convenience because it was supposed to solve a problem for folks who have modern computer equipped cars that are not driven often enough to maintain battery charge but it might fail after a while and kill the battery it was designed to protect. I wonder how many other Corvette owners who have these things really know what their Battery Tender is putting out? Plasticman has it right, forget about Battery Tenders and just get a trickle charger on a timer.

One great feature of the Internet is word about poor product design can quickly spread and if they don't improve their product there will be a heavy price to pay in lost Battery Tender sales.

 

And yet people continue to buy Corvettes.

I don't think the small % of negative comments about the BATTERY TENDER by DELTRAN will sway me away from it. It's pretty obvious that people with positive comments post less than those with negative comments (about any product).

If the time ever comes that my eight year old BATTERY TENDER PLUS fails my five year old OPTIMA red top battery, I'll reconsider my options. It's my second BATTERY TENDER PLUS since '95. The first one served me well with three different vehicles. I gave it to the buyer of the last car. He's still using it.

 

Obviously we know some of them are still working OK. Looks like you are still happy with your's and one of my two 'Tenders seems to still be working OK as far as I know (or guess since I have not hooked any meters up to it yet to confirm that). What I am saying is it appears there is some risk in simply plugging up a Battery Tender to an expensive new battery and walking away feeling confident and content but oblivious to what it is doing. All you have to go on is a little light emitting diode on the unit.

Text below is copied from the Battery Tender website. They state you should check the battery and Battery Tender regularily but they don't explain further to advise you what to do or how to do it. An ammeter and a voltmeter is the only way you can know what your charging rate is and to know for sure whether everything is OK or if you are in trouble.

In theory, you can leave the Battery Tender Plus battery charger connected to a battery forever. Like they say, “Just plug it in and forget about it!” Practically speaking, it is a good idea to check on the battery at least once a week. Strange things can happen. Sometimes a battery can have a weak cell that won’t show up until the worst possible time. Of course, that time is usually when the battery is connected to a charger. If something goes wrong, then you have to deal with the question of the chicken and the egg. Which came first? Did the battery fail because it was connected to the charger or did the charger fail because it was connected to the battery?

No matter how good a product is, anything can break. With a battery and a charger connected together, it’s a much better idea to be proactive and anticipate problems, however unlikely they may be. In more than 99.9% of cases, nothing will go wrong. That still leaves about 0.1% where something might. Learn to respect electricity. A little common sense can go a long way.

 

My new Delco Professional Series battery arrived today and I have another new Battery Tender on order from Corvette Central which should be here in a couple of days. I plan to do as Plasticman suggested and connect it to a timer and just use it in the "absorption charge" mode for 30 minutes each day since trusting earlier Battery Tenders to "float" killed two of my expensive $150 each Delco lead-calcium batteries. Plasticman's arithmetic suggests the on-board computer current drain can easily be offset with 30 minutes at 750 MA daily so it appears we don't really need to risk whether these things will actually work or fail. With a timer it becomes a moot point.

 

I do check mine everyday. It's positioned on one of the uprights of my four post lift making it almost impossible to miss. That's just common sense to me. Green LED on, unit working, battery charged according to the instrument cluster.

I see it as no different than regularly watching the gauges on the instrument cluster. People who don't do due diligence have no cause to complain, but they usually do.

Like I said, if my BATTERY TENDER PLUS ever fails, I'll look at other options. From my experience with the product, I have no reason to doubt the engineering behind it. And the highly touted European CTEK uses LED lights as well. It's just wrapped in a more high tech package.

 

Ah, so you've had both apart and examined the circuits and the code operating them and you know they're the same except for the packaging? They're likely of a similar circuit topology and similar charging philosophy but I doubt they're identical inside and I doubt the controllers are programmed to charge and maintain exactly the same.

I couldn't tell you which one is better but I haven't run across stories of the Ctek's killing batteries like the stories of the BT+'s killing batteries. Not sure it means anything, could just be more BT+'s in the world and that means more failures.

Peter

 

Except the cluster gauges won't tell you what the 'Tender's charging rate is. Without extra gauges connected properly to read volts and amps (or milliamps) you have no choice but to place your trust in the LED on the 'Tender and hope for the best. AND... we're not talking about charging a battery, we're talking about leaving it connected and turned on indefinately and hoping it preserves the battery for years instead of ruining it which others have said happened to them also.

The reason for the LED (idiot light) is economy. They could have easily built-in an inexpensive digital multimeter which would have made it far better without question but it probably would have added $10 or so to the price which might have cost them some sales to a cheaper competitor. Battery Tender even admits their units can fail and recommends checking the progress once a week (and again this requires meters) but they don't tell you that. You have to either ask for advice from someone who knows or figure it out on your own. The Sears Craftsman multimeter pictured in post #7 will easily do the job however, it's an additional device to complicate the hook-up and because it only has one display you have to switch between volts and amps and read them separately. It does have a convenient inductive pick-up for amps and volts will read through the test leads. I was hoping someone here knew of some slick little device with two displays that will read volts and amps concurrently but I guess a multimeter will have to suffice and we'll just have to use the switch.

I don't think we can always depend on that happening and the LED might not be reliable. Someone earlier stated their LED lit up a weird color shortly before it killed the battery and that describes how my Tender failed as well. LED was green for a couple years and appeared to be operating normally before the failure

We all know how reliable those are.