Johnny...Thank you indeed for very detailed, accurate and simple instructions, it's most welcome. I stripped mini and spitfire engines as a teen but this is different ballgame And it's the small details that really help.

final question :) I recall a Bentley tech telling me: before I remove a battery to bridge it with a booster pack to maintain all the codes . This seems counter to the guidance to remove both negatives (start batt 1st, then main) before any battery removal . I have a booster pack for "just in case". Should I use it or not ?

NO !!! :eek: . hilarious

got it !
Could I use booster to start car in a situation when both battery failed ?

That would be up to you, I might or might not depending on the situation of where it was at, what I would probably do is disconnect the negatives and place the hand held high power jumper box on one of the batteries to charge it up for say 20-30 minutes, then reconnect and start, I have done this in the past on my A8L at 5 AM and 18 degrees leaving the Casino, and it worked, but I would never use a A/C powered charger in start mode to start the vehicle, but either way the proper jumping procedure is to hook the positive (+) to the right side starter battery (+) post, and the negative (-) to the left side house battery (-) post.

I removed and replaced the main battery, I'll write it up later.
4 questions:

1) when I replaced the main left yesterday( Disconnecting right negative first, then disconnect main negative, then replace , and reverse procedure to reconnect), car did "not" start with normal clockwise key but all the regular electrics lights etc were working fine. However Car did start when I turned key ccw then cw to start. In other words the new main battery powered the lights but prevented the car starting until I flipped to right side battery. I ran engine for 20 minutes. I switched car off then back on with normal CW key...bingo...it worked. Question : would you expect a new main battery to work 1st time or is it perhaps normal to require a ccw flip to right side battery ?
2) main battery had been sat in my house with no charger for 4 weeks. I bought it from interstate battery store. Do the battery stores keep batteries ,when in inventory, on trickle ?
3) could 4 weeks post purchase be the cause it lost power to start car
4) when I charge one of the batteries overnight by removing the negative do I have to remove both batteries negatives even though I'm only charging one battery ?

charging overnight
 

Apologies for duplication. The guidance on this thread is to remove the negative before overnight charge (not trickle charge where it's ok to leave connected ) . My question is do I have to remove both negatives from right and left batteries in order to charge 1 battery or can I just remove the negative of the battery I wish to charge and leave the other one connected ?

To be on the safe side why not just remove both the +/- from the battery you wish to charge, depending on which one we are talking about as we all know the right hand is way easier, I am not saying that it is totally necessary, but is what I would do, or if you are using a low amperage charger say a 2 amp, then you would really not need to disconnect anything, BUT do NOT leave a 10 AMP hooked up over night as that can lead to cooking the battery, as 10 amps normally charges in 3 to 5 hours, and although some say that they are automatic, I have seen where the charger keeps charging on and off once it has reached full charge, some six years or more ago when my dad put his "automatic" 10/2 amp charger set on 10 AMP on his boat batteries and forgot for a few days..... well they were toast when he went to the basement to check on them, some cells were dry and other were boiling away, and he said they were very hot, we re-filled them, but they were shot, and only one season old.


I myself would feel fine leaving the charger in 2 AMP mode over night with all hooked up, I know first hand while working on my build that when I have it set to 2 AMP and say lights on, dash lit up, or radio playing, all is fine, BUT put it on 10 AMP and you can hear it in the stereo and see it in the lights, maybe it's time for a new charger, it is Century 87102 and over 20 years old.....:o


But back to you charging, don't forget 10 AMPS is 3-5 hour to charge, 2 AMPS anywhere from 2-12 hours or more depending on the amount of discharge, also a slow clean charge is always better then a high power fast charge, JMO.


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Thanks Johnny. I live nyc and I have to be sneaky to connect a charger. I drive car infrequently so was planning on a 10 amp charge once a week and thanks..3 to 5 hours max . That said, I'm not inclined to remove the positive on the main every week so my question remains: when charging the left side main on 10amp (negative disconnected but positive connected ) should I also disconnect negative on the right side even though I'm not charging the right side ?

You should be fine with just the one negative of the battery you are charging disconnected, what I do NOT like is the 10 AMP charging of either once a week, that IS a sure way to kill the batteries by charge discharge every week, I remember reading that you did not drive the vehicle for three weeks at a time or so, at that point if you are not allowed to have a tender hooked up in your parking facility you would be better off disconnecting both negative terminals and saving your batteries life spans, or have a sincere conversation with whom ever you need to as to allow for the tender hookup, even at a monthly fee for the small amount of electricity used, if your batteries go dead you don't even have security alarm, and I thought you were in Texas.... :)

I can't leave a tender on permanently, they are strict with the rules at the garage where I Park. I can hook up a tender overnight once a week or so as their staff won't notice it. I'll try to drive a bit more but given it might sit for 2 weeks and I can't leave a tender on permanently what's my best plan during the 2 week period of no driving.

also I'm reluctant to disconnect both negatives and leave the car

I have never seen a store charge batteries on the shelf for sale. It is easily possible your new battery was less than fully charged. I always charge new batteries before I install them.


BTW, you may already be aware of this but if not...batteries have a sticker somewhere that shows what month and year they were made. When buying a battery off the shelf always get one that is less than 4 months old. Some of the battery's life is used up sitting on the shelf.

I have replaced both batteries and all is well. I wish to maintain them properly. I drive the car once every 2 weeks.

Question 1) Johnny Hotspur posted it was ok to overnight charge on 2 amp with battery terminals still connected. Given I cant leave the charger permanently connected what should I do during the two weeks of no driving ?...should I do a 2amp overnight charge once per week ? (you had mentioned that a 10amp charge once per week is bad practice)

Question 2) I just bought a CTEK 7002. It has a charging current of "7 Amp max". It does not allow me to select "2 amp" or any other specific amps. Its a smart charger so I guess it determines automatically what the battery needs. Question: can I use this charger "without" disconnecting the negative terminal ? In other words, if this charger is starting out at 7amps does this amp level require the Negative Terminal to be disconnected. [of note: CTEK sells the cigarette lighter connector so the implication is this is a convenient connector that does not involve the negative terminal being removed.]

Response in RED.


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CTEK - The Smartest Battery Chargers in the World - YouTube

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https://smartercharger.com/wp-conten...US-7002_us.pdf


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thank you. My garage will not allow chargers. Im guessing other garages are the same plus I now live in the same building as my garage which helps with drive frequency. When you read the danger warnings on the charger itself then its not surprising the dont allow it.

So whats the best plan for me, I realize my situation is not ideal. I do understand the point you made about the CTEK and that its designed for constant use but I'm thinking is there a next best plan. I can charge overnight once maybe twice a week but no more. So should I charge once or twice a week overnight ? or is this doing more damage than leaving it alone.

I've been in NYC 4 years and driving habit has been the same, I forced my self to drive every 2 weeks, in between drives there was no charger and the car worked just fine for 4 years with my 2 weekly drive method. ( typically less than 50 miles unfortunately) . Admittedly, you can tell when starting the car after 2 weeks that the battery is struggling - but it always started until recently when the main left just gave up. It could even have been the original 2005 battery. I bought car in 2010 and have not changed the battery till last week. So I'm ok with replacing the battery every 5 years, my question remains is there any form of charge overnight that will help and not hinder the situation ?