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Charging with a Battery Tender

Just purchased Battery Tender Plus by Deltran to charge my 2004 Odyssey. The Odyssey manual says to disconnect the battery (positive and negative) from the car before charging the battery. The instructions that came with the Tender are not very clear, but do ask that I look into the battery and car manual.

Does it matter whether I am using a “charger” vs a “Tender” in terms of whether I need to disconnect the battery from the car?

Thanks in advance,


I hope you have a lot of time available. A battery tender is not a very robust charger. It could take a very long to to charge a low battery. Battery tenders are primarily for keeping a charge in the battery during long periods of non-use.

Check the manual for the tender to make sure trying to charge a low battery might damage the tender. I suspect it will be OK, but it may take a week or more to get to full charge.

As for the instructions your Odyssey owner’s manual gave you, I suggest following them. Before you disconnect the battery make sure you have any codes needed when you re-attach the battery. Security systems, especially radios can require you to know the code to reactivate it after disconnecting the battery for any length of time. While I doubt if the tender will damage anything on the car, you don’t want to find out the hard way when you just read that you are not suppose to do it.

Good Luck

 I should add that your battery, if original is not too young to be having problems.

If the charger/tender doesn’t ever raise the battery voltage above 15.5V then you can leave the battery connected to the car. Remember to make/break the last charger connection, negative ground, away from the battery.

You should know that a Battery Tender is not designed to charge a dead battery. It is designed to maintain a good battery in a vehicle that does not get much use, or is being stored. If the battery in your vehicle is the original, it may be time for a new one.

I have a Battery Tender Jr. hooked up to a car in my garage right now. I did not disconnect the battery. I have the RED Tender clamp on the positive battery terminal and the BLACK Tender clamp on the engine block. I’ve been doing it this way for three winters with no problems.

Thanks everyone for your replies. All very helpful.

I will keep checking back here in case anyone else has further thoughts.

I got a sears battery maintainer and never read the directions so don’t try this at home. It has brought dead battery condition in my wifes 03 windstar up to starting power in 20 minutes, after the brake light switch stuck and killed the battery a few times till I got enough wd40 in there to solve the sticky switch, I may not be the most mechanical guy, but I have no clue how that brake switch works.

waterboy, just replace the switch. They are not expensive, and, if you can reach it to hit it with WD40, you can easily replace it. Come on waterboy! You can do it!

Thanks for the inspiration, but that thing has more stuff going on than I can even describe. The first problem was how to get it off, it is bizarre!

Brake pedal is to the left.

I see a couple of flat surfaces. Did you try to see if it unscrews from the mount?

No screws, there is a round metal stud on the back side of the black piece with the M, it seems to pivot on, If I pushed on the black piece the brake lights would go on. The black piece is what I shot full of fluid and all is good.