1970s Battery maintainer use and connection.

[J.C.]

Hey Guys,

I've got a '79 Coupe DeVille Phaeton.  Need some advice...

1.  In my car, is the battery's negative post grounded to the chassis, rather than the positive post?

Also, I just bought a Duralast 800 mAh Battery Maintainer.  The instructions say to first attach the positive clip to the battery's positive terminal, then to "connect [the] negative clip to [the] vehicle chassis or engine block...," and then, finally, to connect the whole set-up to a wall outlet.  So...

2.  Why not just connect the negative clip to the negative terminal?

3.  And if I do connect the negative clip to something other than the negative terminal, then what, EXACTLY, should I connect it to?  There's a lot of metal in that engine bay!

I'm not new to classic cars but I am a novice with the mechanical aspects...  Any info would be greatly appreciated, thanks!

J.C. 

[Big Fins]

#1) Yes.

#2) You can with no issues. The main reasoning is in case there is a small connection spark any build up gasses within the battery will not explode. If the charger isn't plugged in, there should be no spark.

#3) Connect it to the top adjusting bolt on the alternator adjustment arm, or anywhere in the engine that is metal.

[J. Russo]

I have an additional question. When charging with the battery in the car, do you maintain the battery with the battery caps on or off?

[James Landi]

Leave the caps on... that charger is designed to maintain the battery at full capacity, and not charge it to the point that there's any significant bubbling and out gassing of potentially explosive electrolyte, --- it's less than one amp... and these "maintainers  " do a good job of  extending the life of your battery as well as giving your starter and ignition a healthy supply of amperage when you're ready to start your cold  engine. And yes, as Big Fins states... keep sparks away from batteries.. especially in enclosed spaces.   

[J. Gomez]

One main reason the instructions on your charger states to connect the negative side to any metal surface and "NOT" directly to the negative side at the battery is to tailor to newer cars electronics. New cars have a battery sensor in line with the negative cable at the battery terminal, so you "DO NOT" want to connect any charging/booster directly to it as it could damage the sensor.

On older/classics/antique cars w/out the massive electronic gizmos you can connect the charger either directly or indirectly on the negative battery post, as Big Fins states above.

As for your last topic, since your battery maintainer is rated at 800mAh just to keep the battery top-off and it will/should turn-off once the battery reaches the required voltage, there is need to remove the caps off while using the maintainer. You can lose them off if you want for venting however they should remain in the hole to protect from any particles to get inside.

Good luck..! 

[Big Fins]

One main reason the instructions on your charger states to connect the negative side to any metal surface and "NOT" directly to the negative side at the battery is to tailor to newer cars electronics. New cars have a battery sensor in line with the negative cable at the battery terminal, so you "DO NOT" want to connect any charging/booster directly to it as it could damage the sensor.

Cool! I learned something new with that one. Thanks Jose'.

[J.C.]

#1) Yes.

#2) You can with no issues. The main reasoning is in case there is a small connection spark any build up gasses within the battery will not explode. If the charger isn't plugged in, there should be no spark.

#3) Connect it to the top adjusting bolt on the alternator adjustment arm, or anywhere in the engine that is metal.

Thanks for the response!

[J.C.]

One main reason the instructions on your charger states to connect the negative side to any metal surface and "NOT" directly to the negative side at the battery is to tailor to newer cars electronics. New cars have a battery sensor in line with the negative cable at the battery terminal, so you "DO NOT" want to connect any charging/booster directly to it as it could damage the sensor.

On older/classics/antique cars w/out the massive electronic gizmos you can connect the charger either directly or indirectly on the negative battery post, as Big Fins states above.

As for your last topic, since your battery maintainer is rated at 800mAh just to keep the battery top-off and it will/should turn-off once the battery reaches the required voltage, there is need to remove the caps off while using the maintainer. You can lose them off if you want for venting however they should remain in the hole to protect from any particles to get inside.

Thanks so much for your response!  I'm going out to hook it up right now!
J.C.

[J. Gomez]

Cool! I learned something new with that one. Thanks Jose'.

@Big Fins,

  Just wait until the next gen electronics features with AI for new cars, you won't be able to change the wiper blades without the special DNA sample detector.      

[bcroe]

The instuctions on order of connecting things are generally
related to avoiding damage in case of an error.  For example
connecting a replacement battery, rec is connect the + terminal
first.  That is so if your wrench happens to contact ground, no
big shorting sparks will occur because the - is not connected yet. 

Then connecting the - terminal, it goes to ground anyway, so
nothing happens if it contacts a ground. 

I have been unhappy with (cheap) clip leads, which corrode, can
come off, and are easily connected wrong.  The clip corrosion
problem I reduced by covering the connection end of them with
solder, before rust eats thru the thin copper coating. 

I have equipped all my engine starting batteries with a plug in
system.  This eliminates errors and clips coming off.  Besides
maintainers, the same connections can be used for things like
a timing light.  My choice was the EC3 connector system, used
on models.  It is cheap, compact, polarized, uses decent contact
material, and capable of plenty of current.  I make up a cable set
like this, which contains a fusable link at the + power connection. 
I also equip a mating conn with a single pin for use as a dust cap
when the maintainer is removed, a pigtale keeps it close. 

These connectors have some tiny markings, but I have drawn out
the standard use on everything here. 

My opinion, the actual battery is about the lowest impedance point
available for the purpose of absorbing any transients.  So short wiring
to it is a good place to connect some things.  Bruce Roe

[jwwseville60]

NOCO genius chargers are worth every penny.

https://no.co/brands/noco-genius

[Lexi]

Have not used that brand, but good to know. I have used Battery Tender Plus, for about 12 or 13 years and never a problem. Would also put forward that recomendation. Clay/Lexi

[Big Fins]

I have a few Battery Tender Plus units too. I also use the .75 amp small Battery Tender for the yard tractors. I'm getting 4 years out of lawn and garden batteries.

[Lexi]

I have a few Battery Tender Plus units too. I also use the .75 amp small Battery Tender for the yard tractors. I'm getting 4 years out of lawn and garden batteries.

My 12 or 13 year experience with the Battery Tender Plus unit, includes constant service during the 5 - 6 month winter down time, yearly. So, the unit currently hooked up to my car is about 13 years old. That said, I had a battery expert tell me that every once and a while, especially prior to parking my car for the season, to put at least a 10 amp charger on her for a minimum of one hour or more, to knock off sulfation that may have formed on the plates, prior to trickle charge maintanence for the winter. This advice applied to wet cell batteries. Back in the day, Cadillac even advised regular charging to keep the battery as fresh as possible. These batteries were not as adept at keeping a charge like the newer ones, but seems like the same rule still applies. I believe these charging units can also extend battery life by lowering the freezing point of the electrolyte, thus further safeguarding your battery from freezing during winter lay up. Still, a good idea to regularly check on them during this time. Clay/Lexi

[Big Fins]

Freezing is one thing I'm glad I don't have to deal with. Use of a deep cycle battery I would think would be best for shock charging. There is enough space at the floor of the battery for the shedded material to collect before shorting that particular cell out.

[Lexi]

Yes, good point. Need room for the garbage sulfate to collect. This battery expert also told me that back in the day the wet cell "flooded" batteries were built using lead antimony plates, not the calcium lead plates of today. Hope I got that right. He also said the newer batteries have less out gassing and last longer without a maintainence or booster charge. That said, even he still suggested a heavier charge at least every 3 months to maintain a newer flooded style battery. Surprisingly, he did not recommend hooking up one of those "rejuventating" chargers. A regular, heavy duty charger should be all you need, was his opinion. This guy actually rebuilds batteries, (or did), and was a wealth of information. Clay/Lexi

[Gene Beaird]

I have a few Battery Tender Plus units too. I also use the .75 amp small Battery Tender for the yard tractors. I'm getting 4 years out of lawn and garden batteries.

+1 for the Battery. Tender brand.  We have several, some single, double and 4-bank tenders in our shop.  Most are connected directly to the battery.   While using them, we usually get >10 years service out of the batteries.  EVERYTHING we have, though, is either AGM, or LiFePO.  Flooded-acid batteries are not welcome on our property!   

The race car has a plug-in setup much like Bruce noted above, only using the factory Battery Tender extensions.  The actual connection to the cable is at the door, where the end of the wires going to the battery are zip-tied to the roll bar.  The battery for this car is where the passenger back seat used to be.  We connect the Tender to our '12 Caprice via the jumper lugs under the hood since the battery is in the trunk and all our 110V outlets in the garage are across the back wall. 

A habit I developed early on, that has served me well, is to blow on the top of the battery before hooking up the negative jumper cable or charger lead.  That'll dissipate any lingering hydrogen gas enough to prevent any explosions.   

[Jeff Rosansky CLC #28373]

I have Battery Tenders on our 55 and 70.
They are hard wired. On the 55, I connect positive to the regulator post that goes to the battery, and negative to a close ground. For the 70, I just have it connected to the bolt on the battery cable connection. I have the pigtail sticking out of the grill and just plug them in.
MY dad's 79 has those stupid side terminals and we haven't found a good place to hard mount the positive, so he just clips it on the battery.