Gearhead Jim

My old Sears "Automatic 'Sensor" Battery Charger" has a switch to select Conventional or Maintenance Free battery type.
The manual says ""Maintenance free batteries require higher voltage to effect full charge."

Really?

FWIW, I've been using it for 25 years, no problems.
It goes into a "maintainer" mode when the battery is fully charged- charge drops to 0 for a while until battery bleeds off, then it goes back to low charge rate for a short time.

C7Joy

Don't know the answer but no reason to change what has worked for you!

mack morrow jr

Maintenance free and deep cycle marine type batteries do require more power to charge which is why you usually have different settings for the different type batteries you charge. Regardless of whether you have the various settings even a manual setting will charge but take a longer time. I have a Harley motorcycle 1.25 mv plugged up to the Vette right now. I usually use my 10 AMP to bring it up to full charge which takes about an hour. The 1.5mv would take about 6-8 hours to do the same thing.

saplumr

I really don't know but it's possible a 25 year old charger is not up the current battery technology. My large charger has switches for 6v -12v-regular automatic - deep cycle automatic - 2amp -15amp - 150amp. For years I used it as a trickle charger but lost confidence in it and now use a Battery Tender.

jpee

I understand what you are saying, but I have always been under the impression that, given the choice its better to charge the battery at a slow rate as opposed to a FAST charge... I "Think" charging for 6 hr at 1.25 is preferred to 1 hr at 10...

I could be wrong...I'll try to research it or maybe someone here knows off the top of his head...

RedVette84

Are you using it to charge a dead battery or maintain a charge?

Vette5.5

Think I'd upgrade to a more modern charger such as Ctek or Deltran, which have very sophisticated electronic anti sulphation circuitry. Batteries seem to last forever on these. I use a Ctek 3300 on just about everything. Has the higher voltage setting for Optima style batteries and lower current motorcycle setting for small batteries. Have other older charger's, but the 3300's truely connect and forget. Actually have two of them.

Gearhead Jim

All of our cars, including the Corvette, get driven enough that I've never used any kind of tender and always gotten good life from the battery. I use the charger only to top-off the battery if I've been doing work on the car that tends to run it down.

I started the thread only to learn more about the batteries, no issues with the charger.

VET4LES

I also have an old Sears charger. Sounds like it's similar to yours. I only use the 2 amp setting and it shuts off when charged and starts again when necessary. Since I only drive six miles a day (three to work and five hours later three home) I put it on for a few hours on the weekend. Never had an issue with my 2005 battery. I'm on my second one now, Optima Red Top.

RnLi

I'm not real sure about this, BUT someone here, or on another forum, indicated the no maintenance batteries require a special charge (higher voltage?) for a specified time to assist in removing sulfating on the plates, that occurs more on the "sealed" battery (no place for the "gassing" to go).

Could be wrong, however.

AORoads

I agree w. this, John. BUT, as you say, it could be old methodology not meant for today's batts. Trouble is, today's batts. aren't all that different.

Gearhead Jim

That would go along with the quote from my charger instructions.

But there must be some way for pressure to equalize, otherwise the battery could explode or leak when you go up in the mountains.

Someone else claimed the only difference with a maintenance free battery was that the level of electrolyte was higher, so the inevitable loss over time would not uncover the tops of the plates. Beginning to sound like that may not be true.

RnLi

Well, I can't answer a lot about that. I've never really checked.

I know GM has a lot of batteries mounted in areas of no ventalation....under back seats, in trunks and "hatches". And these batteries, for the most part, have some type of vent tube on them....at least on the OEM's and a few replacement aftermarkets...that exit under the vehicle.