Question about my battery tender and optima

[Zedyone_kenobi]

Okay folks, I recently purchased the 60 amp alternator upgrade from MSA and the install was simplicity itself. I am very happy, but to make the job complete I also bought a Deltran Battery tender Jr 12v model. I have heard nothing but great reviews so I decided my red top optima deserved it. Now here is where it gets weird. I have left it on the car for a solid 24 hours now and it is still glowing red meaning it has never reached the 80% charged level it should and go green.

So I picked up my voltmeter and started to do some fiddling.

Hooked up to the battery tender, I get about 12.3 volts going to it or so after 24 hours. Unplug the battery and it stay around 12.4 volts.

Start the car with my new shiny alternator, and I send a constant 14.2 volts to the battery, which is good. Alternator should put that kind of juice out. My old 40 amp alternator/regulator combo that was stock with the car only put out 12.2 volts.

What gets me is no matter how much I charge my battery, it never gets above 12.4 or the 12.2 range. IF left for a long time without driving or charging it will often read less than 12 volts, 11.4 was the lowest.

Now my recollection is that a fully charged battery should have in the neighborhood of 13.XX volts..

I have been thinking my optima is old and may be on it last legs.

Any comments?

[MikeW]

I have a stock alternator, a < 6 month old Optima red top, and a battery tender Jr. I haven't even cranked the car in at least a month. The tender had been on it that whole time and had a solid green light. The battery read 13.05 volts with the tender in place and continued to read 13.05 when I took the tender off. When I put the tender back on it started flashing green and the voltage jumped up to 14.5. Presumably it thinks it needs to charge a bit but hopefully with change its mind soon.

How old is your Optima? The actually have some good tech tip videos (specifically #3) that may help you recover yours.

[Zedyone_kenobi]

How hot did your tender get. Mine is hot to the touch. Not so hot you cannot leave your hand on it, but pretty darn warm.

[MikeW]

I don't recall the tender ever being warm at all but I'll verify when I get home. I disconnected the positive charger clamp from the battery to measure just the battery voltage instead of unplugging the charger itself so I didn't actually touch the charger.

[sblake01]

My battery tender gets warm to the touch pretty much in the way Stephen describes. I'm not using it on an Optima but it reads around 13.15-13.18 when the steady green comes on.

[Zedyone_kenobi]

That is what I was expecting, but after 24 hours of charging, the red light is still solid and it never gets above 12.4. I may have to look into grabbing a replacement battery just to see if I can get it to charge to 13.XX

[Shade133]

what is this battery tender device? is it something that is charged up when the car is running and then when the car shuts off it puts a trickle charge on your battery to keep it full charge over long periods of time of sitting?

im interested

[MikeW]

what is this battery tender device? is it something that is charged up when the car is running

No

and then when the car shuts off it puts a trickle charge on your battery to keep it full charge over long periods of time of sitting?

im interested

Yes. Unlike a normal "trickle charger" which charges a battery at 2 or 6 amps for a few hours a battery "tender" charges at milliamp levels and is designed to be left on the car for an extended time. It has circuitry to only charge as needed.

This is the model being discussed:

http://batterytender.com/

[Shade133]

awesome thank you.

[Zedyone_kenobi]

I think what I will do is hook it up all weekend and see if it will get me to 13 volts. After 24 hours, the battery was not warm at all, so I am not really worried I am hurting the battery or that it has a short.

[MikeW]

Mine is warm to the touch (115 degrees F) even when in 'float mode' (solid green light) so presumably it's normal to be warm. If yours is still trying to charge I wouldn't not be surprised if it's even warmer.

[mlc240z]

Something similar happened with mine.

Left it on for a couple of days and it still wouldn't green light. Battery was NOT drained. Thought I got a bad unit.

Put my regular battery charger on overnight to 'top off' the battery. Reattached the tender the next night, and it went to green and haven't had a problem since. Multiple re-attachments over past 3 months.

From what I read, if the battery is below a certain level (I think 80% ??) of charge the electronics basically turn the Tender off. It's not designed to be a 'battery charger', just a maintainer. Once it detects that the battery is above its baseline charge it will operate normally.

I have a Battery Tender Plus.

Don't know if this applies to all models/brands.

Edited July 24, 2010 by mlc240z