[BobNovas]

Well, it's been said before, but I'll say it again. Don't put a battery charger on a car battery and leave it. I almost but didn't do that - I put a Sears 2-10-50 Amp battery charger on my wife's car battery, which was only just starting her car, on the 2A setting. It charged the battery for a couple of hours, but then stopped charging. So I pushed it to the 10A setting. Then I thought better of it and measured the battery voltage with the battery under charge.

2A setting - 13.8V
10A setting - 15.8V (Not a good thing!)

Had I left the charger on in the 10A position for any length of time, I dare say I would have boiled away the battery juice.

I fired up my trusty battery maintainer, and it has the battery at 13.3V and is still slowly charging it up. So that's most certainly the right way to do it.

[matt de maria]

That's why for late model cars with dead batteries it is safer to disconnect the battery from the car. The battery chargers voltages will go up to 20v. This will fry ecu's.

[Mackliet]

I just purchased a 12 v 1.25 amp Battery Tender. As I recall, the documentation says it will charge the battery up to 12 v and then monitor the battery for a one volt drop, at which time it charges it back to 12. It also states that a minimum of 3v is required before it will charge.

Do your cautions apply to this type of charger?

Thanks and Happy Holidays to all.

[cstreit]

Doesn't your charger have an auto-detection/trickle sensor?

[scott]

in all of my machines, hold for the lawn tractor. The battery chargr is looking a little dusty these days...

[Vicegrip]

Bob. your charger is working right and 15.8 V is not harmfull to the system. Wet cell batts have restance and it takes overvoltage to overcome this. Your alt will do the same thing. Did the 2 amp setting stop when the batt was charged?

(Caution, opinion zone)
Get an automatic charger. They are inexpensive and you can get them with maintainer settings as well. Charge on auto and then swich to maintain. Maintain is not the same as trickel! It comes on only after a voltage drop and stops when charged. Trickel chargers are bad voodoo. They WILL dry out a batt with time. Maintainer is the way to go on long term parked cars

Get a portable jump start setup. They are also cheap and will protect your cars brain when jump starting. If you get a low bat charge jump and drive. If you have a dead batt let the auto charger do the work and save the alt.

[RoninLB]

trivia

the routine wet cell is best recharged at low amps to prevent caking the sulfer to the plates.

the lowest CCA necessary for your car, for same sized battery, will have thicker plates than high CCA batteries leading to longer battery life.

it's always best to disconncet battery from car for charging.

jump starts may cause a current surge when disconnecting the "jump". there are methods to help prevent this, thou not guaranteed.

I've found that Optima needs high amps, to start the recharging, for a minute.. no hard book info on this.

recharging by driving loads your alternator. If not necessary don't do it. The alternator will not completely recharge the battery like a charger will.

use distilled water when necessary. Tap water will have alum, iron, mag, etc which coats the plates.

a marine battery ground lug will have wing nut to attach a new cable. I prefer this vs a switch. A sw has a voltage drop as a matter of the sw design. The marine lug leaves a direct cable to lug attachment. The wing nut is a quick spin to remove the cable. Also in case of fire the battery should be quickly disconnected First.. Disconnecting the ground does not leave residual current in the system from coils, supressors, etc.

[Vicegrip]

Good points. There are some other things to think of as well.

Lower CCA per total battery volume might not mean thicker plates but more space between anode and cathode plates thus less likely to short out when plating occurs. This would make them last longer but this might be somewhat counteracted by having deeper discharges and recharge cycles.

Many marine batteries are made quite differently than automotive batteries with regards to how the unit charges and discharges. They also tend to be heaver for a given rating. You can use a non marine battery and still have a quick disconnect. There are nicely made bolt on connectors that have a knob/bolt setup that mechanically disconnects the line but do not induce any significant voltage drop. Marine post and bolt type stick up exposed and things love to short out on them.

Ask Dave (not Dirk) Decker about shorting out batteries and the resulting fires. I was told that a battery short during a gas tank removal started a fire that burned up a bunch of his stuff including mutiple 4 cam motors a 356 and a 550.

[RoninLB]

Originally Posted by Kurt Mickelwait

Lower CCA per total battery volume might not mean thicker plates but more space between anode and cathode plates thus less likely to short out when plating occurs.

You can use a non marine battery and still have a quick disconnect. Marine post and bolt type stick up exposed and things love to short out on them.

much bs from battery mfg's. Who knows? I was told by an Interstate rep that their labeled "marine" is same as auto. There are specific mfg's I trust for true marine batteries.

The lower CCA thicker plated was book info.

I probably wasn't very clear on the disconnect. I was refering to the marine ground lug only. The wing nut stands up about 1/2". I use the Optima Red Top auto. I keep extra wing nuts close. It's a pia when cold fingers drop them.

Any sw, like the commonly used battery disconnect sw, has a voltage drop. Any connector has about 1/4-1/2 the drop of a sw, asuming a good sw and a good connection.

gratefully we didn't get involved in deep cycle batteries or manually regulated car alternator regulators.. lol

[Vicegrip]

Did not mean to sound like a pissing match and I am no expert. Just a slow day at the shop.
All I was pointing out is that marine post with bolt connectors are more likely to short out when installed in a car battery location that was designed for a car battery. There is a post and bolt on both terminals of a marine battery and unless you cut off the + bolt it sticks up unprotected well beyond the height of a normal automotive post. Marine batteries are normally mounted inside a plastic box or inside a purpose built battery compartment. The box or compartment encloses the exposed battery terminals. In the case of a pre 90s 911 the battery is sitting on the front trunk floor next to the spare tire. Under the golf clubs, swap meet finds and tools and only covered by some felt trim carpet. Automotive batteries often come with + terminal covers that cover the connector when installed and many have the posts recessed to be flush with the top of the battery.

The disconnect I was referring to is NOT the common knife switch type. It uses an insulated bolt to connect two conductive plates together and has a large conductive surface area.