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Car batteries not keeping up - differing advice

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Car batteries not keeping up - differing advice

Old 21st Jun 2020, 02:59
  #41 (permalink)  
 
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True story - I bought a new battery for my Mazda from Riley's Garage in Maun, Botswana. The following year I was driving down to Gaborone and filled up with fuel in the same place. Paid the cashier and turned the ignition key. Nothing - not even a solenoid click, the battery had completely died with no warning. I rifled through the glove compartment for my receipts and found that it was the last day of the guarantee! The mechanic fitted a new one and I was on my way in half an hour. It picked a perfect time to quit, just before a 1000 kilometre trip through mainly nowhere.
What were the odds of that...

Last edited by stevef; 21st Jun 2020 at 07:53.
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Old 21st Jun 2020, 03:08
  #42 (permalink)  
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That's funny, in an amazing kind of way.

I was struggling home with a glow worm for a headlight on an old Matchless 350. Miserable dark back then, and no other cars to latch on to. Suddenly it failed completely. I pulled up outside some old metal barns imagining being there until daybreak. A bloke came running out, I don't know how he'd seen me, but he was shouting, That's my old bike!!!! He fiddled with the headlight switch on the headlight, and gave it a smart thump. Lights better than ever before.

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Old 21st Jun 2020, 03:15
  #43 (permalink)  
 
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On the subject of disconnecting negative first (or connecting it last):
As was mentioned, it had to do with lead acid batteries leaking hydrogen in some situations. Since the first disconnection (or last connection) makes a sudden change in circuit current, a spark is likely. So why negative?
AFAIK, this advice assumes that the negative connection is made away from the battery itself - not right at the negative pole of the battery. And this assumes the most common car electric setup with the car body connected to the negative terminal. Is the hypothetical hydrogen gas concentration higher at the negative end? I don't know. I figure that if the battery is that bad, it is bubbling inside and leaking through the weakest seals, wherever they may be.

I used to ignore this advice, with all them modern batteries having far more sophisticated chemistries, seals, and all. And then, one day, wife calls that her car doesn't start. Barely cranking, then not cranking. Yes... I forgot to replace the battery on schedule and city driving is hard on this thing. I drove over to give her a boost. I don't remember what I connected first. But I do remember that the last connection I made was from my battery directly to her battery terminal - a big lead alloy post. Ie. to the battery that was dead. 0.0 Volts. There was a flash (spark) and loud pop. Scared the crap out of me. Investigation showed a rather large pit (missing metal) in her battery's terminal. With my brains finally out of neutral, I figured that my car's good battery gave it its best "cold cranking amps" and melted / vaporized a bit of wife's battery.
On the 2nd attempt, I did the last connection to car's body. At that point I had it set up to be negative. Just a spark and life could go on. (*)
But the sight of that missing metal on the battery post will stay with me forever. Nothing to do with hydrogen, in this case.

(*) Actually, and eventually, it turned out to be an alternator problem, but by then the battery was quite damaged by the low charge state.
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Old 21st Jun 2020, 04:09
  #44 (permalink)  
 
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Can recommend the small solar panel type as long as it is regulated.
What do you mean by regulated ? I have a small one, but how will I know if it is "regulated" ? I have been reluctant to use it for a long period in case it actually discharges the battery at night ? i.e does the battery try to "feed" the panel ?

If you just disconnect the battery don't you lose a lot of "information", radio codes etc. ?
I'm aware that I will lose radio control, and have made a note of the required code to re-establish it, but will it also screw up the ignition circuit ? I can live without a radio for awhile, but if leaving a car unattended in a remote spot away from home, with the battery disconnected, I at least need to be able to start it to get home again, when I then have time to re-code the radio.

Any answers ?
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Old 21st Jun 2020, 06:46
  #45 (permalink)  
 
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I used to use a small "smart" charger to keep my aeroplane battery topped up when it was in the hangar. Seemed to work very well, as it did as outlined in a few posts above, and only give the battery charge when it needed it, making sure that it didn't self-discharge, but also making sure that it was never over-charged, either. I think it cost what seemed to be a lot for the size of the thing, around £50, but it did do a very good job. The one I used to have could only charge at around 1 amp, IIRC, but was designed to be left connected for months on end, just keeping the battery topped up. It came with a car cigarette lighter type adapter, so could be used to keep a car topped up if stored, by just running the lead inside the car and plugging it in to the socket in a car.
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Old 21st Jun 2020, 06:59
  #46 (permalink)  
 
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My Honda Insight's Nickel Metal Hydride main batteries went kaput, twice. (Expensive at 2,000 GBP a set.) When I asked Honda about leaving it undriven for three months at a time, they suggested this would not be a wise thing to do. They refused however to look after my car for me while I was away. Eventually I trained one of their more friendly staff to come round and 'borrow' it for the occasional weekend with free petrol thrown in.
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Old 21st Jun 2020, 07:01
  #47 (permalink)  
 
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Originally Posted by ExSp33db1rd View Post
What do you mean by regulated ? I have a small one, but how will I know if it is "regulated" ? I have been reluctant to use it for a long period in case it actually discharges the battery at night ? i.e does the battery try to "feed" the panel ?



I'm aware that I will lose radio control, and have made a note of the required code to re-establish it, but will it also screw up the ignition circuit ? I can live without a radio for awhile, but if leaving a car unattended in a remote spot away from home, with the battery disconnected, I at least need to be able to start it to get home again, when I then have time to re-code the radio.

Any answers ?
A small panel does not need to be regulated, a rule of thumb we use on boats is <2W/50AH does not need regulating. In fact, I would not worry about a small 5W panel on a typical 75-100AH car battery. It will rarely charge at full power and self discharge overnight will help. All solar panels that I know of (or can imagine) have diodes to prevent discharge through the panel.

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Old 21st Jun 2020, 07:53
  #48 (permalink)  
 
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For older Toyotas: if you need the radio's PIN after a flat battery, try the last three digits of the car's VIN. That should work if no one's changed the radio or the PIN.
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Old 21st Jun 2020, 07:55
  #49 (permalink)  

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Originally Posted by NutLoose View Post
Err..... you remove the earth first because it is earthed already so if you touch anything it does not matter... if you remove the positive first and touch an earth in doing so, you will short the battery out risking an explosion, possibly fry some of your electronics and weld the spanner to the car.
Exactly. If the spanner used to undo the “positive” terminal earths out there will be a lot of sparks...and worse!
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Old 21st Jun 2020, 08:10
  #50 (permalink)  

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Originally Posted by VP959 View Post
It came with a car cigarette lighter type adapter, so could be used to keep a car topped up if stored, by just running the lead inside the car and plugging it in to the socket in a car.
😉 Using the cigarette outlet to charge its own battery, patented yet?
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Old 21st Jun 2020, 08:12
  #51 (permalink)  

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My BMW 330’s battery died on me late one night, miles from home. There was enough power to turn on the engine lights, but the starter motor wouldn’t even engage.

Getting the car home was a nightmare (RAC were totally useless - they were not going to get to me before 05:30 the next day and eventually my wife got out of bed and drove 30 miles with my jump leads, bless her).

I bought a new Bosch battery (quite expensive, on those cars they are commercial vehicle size). A week later the car refused to start again because of low battery power and I had to get to it via the ski access between the rear seats, as others have said because the boot wouldn’t open. Turned out to be the car central computer had failed and it’s cooling fans were running continually till the battery drained. BMW charge £2300 for a replacement CCC!

Turned out the original battery was fine. I keep it as an auxiliary battery. I didn’t keep the BMW.

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Old 21st Jun 2020, 08:31
  #52 (permalink)  
 
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Originally Posted by VP959 View Post
It came with a car cigarette lighter type adapter, so could be used to keep a car topped up if stored, by just running the lead inside the car and plugging it in to the socket in a car.
😉 Using the cigarette outlet to charge its own battery, patented yet?
This will assume that the cigarette lighter outlet is "live" (connected to the battery at all times). That's not the case with our vehicles - the outlet only becomes "alive" when the ignition switch goes to the 'accessories' position or further to the engine run detent.
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Old 21st Jun 2020, 08:59
  #53 (permalink)  
 
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Originally Posted by FullOppositeRudder View Post
This will assume that the cigarette lighter outlet is "live" (connected to the battery at all times). That's not the case with our vehicles - the outlet only becomes "alive" when the ignition switch goes to the 'accessories' position or further to the engine run detent.

Good point. It's years since I've plugged anything into one of those outlets, but I remember that my old Mitsubishi Shogun had one in the boot area that was always live, as I used it to run a tyre compressor a few times. It probably varies a bit from one manufacturer to another, perhaps.

The Mitsubishi also came with mains connector on the front bumper to allow the car to be plugged in and pre-heated, ready for a nice easy warm start the following morning. Seemed like luxury, getting into a warm car on a cold morning.
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Old 21st Jun 2020, 09:20
  #54 (permalink)  
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My Holden Caprice had a button in the glove box that opened the boot, never checked but I assumed it was universal?

The law according to Varta: Safety: Always remove the negative cable first, then the positive cable. When you connect the battery, connect the positive end first. So the order is: Remove black, remove red, attach red, attach black.
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Old 21st Jun 2020, 09:25
  #55 (permalink)  
 
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As for radio re-coding, later models do not need it as the car talks to it and checks if it is the correct one, well my Audi does.

As we are talking Cigarette lighters, correct, a lot are often powered off when the keys are removed. Though I do not know if that is the same for Loose Rivets as he has a
Cigar lighter
Posh git


..

Last edited by NutLoose; 21st Jun 2020 at 09:40.
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Old 21st Jun 2020, 09:32
  #56 (permalink)  

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Radio? Only posh folks can afford a car with a radio....🤣
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Old 21st Jun 2020, 09:37
  #57 (permalink)  
 
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Originally Posted by ShyTorque View Post
Radio? Only posh folks can afford a car with a radio....🤣
Is that the same as a wireless?
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Old 21st Jun 2020, 09:42
  #58 (permalink)  
 
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Yes, and if you buy a Merc, you also get a cardigan, slippers and a pipe in the boot.


sorry thread slip...
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Old 21st Jun 2020, 10:05
  #59 (permalink)  
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Bloody hell, more electrical and computing power in a modern car designed to go shopping down the road than there was to get Apollo 11 to the moon and back. And that's without using electricity as a motive force.

I remember the first person in my circle of friends to get a car with electric windows - a Montego. Four of us went to France in it and when we came to the first peage, the front passenger window - mine, the one we were going to use to pay the lovely mademoiselle - point blank refused to work, I had to get out. Next opportunity, Ian and I dismantled the door trim and discovered a loose connection which intermittently gave trouble until we could get some tape and bind it into submission. Been suspicious of too much gadgetry ever since...
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Old 21st Jun 2020, 10:11
  #60 (permalink)  
 
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My bug bear with batteries during lockdown is that although the car battery is fine and car starts ok etc the Dash Cam re sets it's date and time if car is not used for 2 days. I use the Aux socket that only has power when car running and the internal battery in the 'cam dies
yes I know I could get kits for connecting the 'cam to a live fuse. ...but I can't be arsed.
now a dab hand at re setting the date and time. Could do it blindfolded...
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