Intermittent battery drain

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Charlieepie
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Intermittent battery drain

Post by Charlieepie »

Hello,

Me again! After all the small bits she’s had done on the bodywork, the boot is now watertight and I no longer dread the rain for leaks.

However - I’ve got an intermittent battery issue where it’s draining and I wondered if anyone had had something similar?

History -
- Bought the car beginning of August 2021. No issues until October.
- In late October we had a really bad storm. Went from starting fine one day to totally dead the next - not even any lights on the dashboard.
- Had it checked out and garage advised me alternator had taken a soaking due to its placing in the engine bay but after being dried out it seems to work ok.
- Car was ok for a couple of weeks, tried to start it mid November - flat!
- Went into garage and they found an issue with my central locking where it was constantly locking and unlocking the passenger door and draining the battery.
- Was ok for a week or so then same again - fine one day, completely dead the next. It had snowed on her overnight this time!
- had new battery after that as suspected it had suffered from being constantly drained and recharged and the cold snow had finally killed it.
- this seemed to work for 2 weeks or so, then I tried to drive her Boxing Day after a couple of days of rain. Dead.
- she’s been in the garage again since, and they’ve tested everything that could be drawing the battery and come to the conclusion it’s intermittent (they couldn’t find a fault at the time).

So, it seems to correlate with periods of when she’s parked up in bad weather - mostly rain, snow once. I’m talking less than 24 hours sometimes though, so I can’t even just try to drive her more often to keep the battery alive.

Is there anything obvious on the electrical side that has known issues with water getting in, other than the alternator?

Currently my only working theory is my alternator has a partial fault where it drains my battery when it gets wet. However I don’t have any other telltale signs of a dodgy alternator - no dim lights/radio issues when driving, and she’s done 4 hours up the motorway no problem on the previous nearly knackered battery.
I suggested this to the garage and they agreed it could be an alternator fault but they wouldn’t recommend replacing it as it would happen again, which I don’t think I agree with - it did 21 years prior to my ownership without this issue and it will have definitely been rained on in that time.

My next step is to try a relatively simple fix of jump starting her this week one day after work, taking her for a spin to charge the battery, and then covering the engine bay with rubber mats to keep any rain out (as recommended by someone on here!).
If this actually works, then it’s an easy win, but if it doesn’t I’d like a better solution than jump starting after every time it rains. At the moment she’s been sat with a flat battery for over a week because I haven’t had the time to do the jump start / long drive.



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Re: Intermittent battery drain

Post by nick »

Mine does it after about 2 weeks. I think the alarm system is ofter to blame. One of these small starter battery packs can be useful, about £50 I think
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Re: Intermittent battery drain

Post by Synz »

Mine also does this and it's not even in the rain. My battery is fairly new and I have a brand new alternator but still if I leave it in the garage for 2-3 weeks without the trickle charge it dies. Perhaps the alarm.

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Re: Intermittent battery drain

Post by Charlieepie »

I wish mine lasted for 2-3 weeks instead of 24 hours! I drive it (weather and now battery life permitting!) every 2-3 days as I like to switch it out with my other car.
My battery is about 2 months old so it’s definitely got an issue somewhere. I also thought about the alarm system, but I don’t think that little red flashing light on the dash would drain me in a day.

So is that essentially a trickle charger you just leave in place? Is the idea to just plop it on, leave it in there with the battery and let it do it’s magic? Does it charge itself when the battery charges off the alternator?
My only worry really is she lives outside not in a garage and a mini battery charger doesn’t sound like a thing I want to take a soaking in bad weather!
Then again, neither is the alternator 😅
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Re: Intermittent battery drain

Post by jeff »

not sure what you mean by
Does it charge itself when the battery charges off the alternator
but i suspect you are assuming its powered internal which is incorrect, it is connected to the mains

i have one of these https://www.ctek.com/uk/battery-charger ... mxs-5-0-uk

i fitted the eyelet lead supplied directly to the battery and routed it past the spare wheel, then simple as plugging the charger in and lowering the bonnet with the charger tucked inside and plugging it into the my outside mains socket
they also do a 2.5 meter extension lead and Jimi has this as he mounted his unit to the garage wall then just ran the lead into the car

also, worth getting the battery checked, i have had a "new" batteries that have failed within 6 months and had similar issues to yourself
new battery from Halfords fixed the rapid discharge rate
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Re: Intermittent battery drain

Post by jimi »

Try removing the boot light lamp, the MK2 bootlight switch is known to go out of adjustment. Its quite possible a faulty alternator can flatten battery quickly, but not normally intermittently, dampness could have that effect. Quite expensive to just feplace it on the chance it may be the problem. You could get your alternator checked & refurbished by an auto electrican, would be cheaper.
Battery going flat in 3 to 4 weeks isn't unusual, alarms, clock and headunit memory will do that. Thats why I keep a battery maintainer (CTEK) plugged in most of the time.
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Re: Intermittent battery drain

Post by S81933 »

Following on from Jimi, I know, to my cost, that leaving a door not quite shut will drain my battery. Seems strange, all it's got on is the door courtesy light and the interior light, which should both be low wattage, but maybe there's something else still active if the doors are not fully shut.

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Re: Intermittent battery drain

Post by Charlieepie »

Ah I should have said, my boot lamp is already disconnected. I had 3 separate leaks into the boot which I think have now been sorted but waiting on some really heavy rain to prove it before putting the liner back in.
Agreed RE alternator being expensive to just replace but I’m at a loss to what else might be the issue and having to jump start every time it rains is a pain in the bum. I also wouldn’t expect intermittent issues from it but I’m sure it’s rain related as it’s done 2 weeks with no issues when it’s been dry and then died in less than 12 hours in bad weather. I don’t appear to have any obvious leaks where water could get into any other electrics either

I’ve been triple checking doors are closed properly since having the issues, I also have switched the internal light to not come on when the doors are open for that reason (the drivers door is a nightmare for not closing to on the first attempt).

Jeff yes I was thinking it was internally powered not mains powered, I wrote some not very articulate sentences first thing this morning I see… Those chargers then look more like something I’d plug in if I wasn’t going to drive it for a couple of weeks, not necessarily great for connecting up and disconnecting every couple of days.

I was going to try jump starting and charging her up today but it’s pouring with rain so it might be a weekend job now. Annoying as my other car is going back into the garage tomorrow. January is not my month!
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Re: Intermittent battery drain

Post by jimi »

How are you charging the battery after its gone flat ?
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Re: Intermittent battery drain

Post by jeff »

still convinced its a battery issue

https://mr2oc.co.uk/forum/41/168882.html
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Re: Intermittent battery drain

Post by Charlieepie »

jimi - it’s only gone flat once (well, twice now) since battery replacement, and that time the garage jump started it to recover it (they are only 100m down the road) and then charged it - assuming with a trickle charger.

I was planning on just jump starting it and letting the alternator do the work, but I know it’s not healthy to let the battery drain and constantly recharge.
If it was a week or two between drains then I’d just periodically hook it up to a smart charger if I was leaving it for a period of time but every 1-3 days isn’t manageable!
Probably looking at the weekend to get it sorted now too, she hasn’t been driven for 2 weeks at this point

Jeff, I’m hesitant to whack a new battery in it because the new one went flat after 2 weeks of installation, what are the chances of a battery THAT bad actually being fitted? It was replaced mid-December and then failed to start again Boxing Day after the first bout of rain since replacement. And It’s the same symptom as the old battery except the old battery held it’s charge for even less time!
Also looking at that thread it looks like the battery capacity there was wrong which mine isn’t? Or are you thinking I’ve had a cheap or slightly faulty battery put in which just can’t cope with the slight drain everyone’s MR2 seems to have…

It’s driving me mad, I just want to drive her :(
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Re: Intermittent battery drain

Post by Shotgun »

I got sick of regularly having to charge my battery so I fitted a simple isolator switch.
( as was fitted to my horsebox)
Its mounted next to the battery (in the front) and has a simple plastic control which can be removed for security.
Only £9 .....
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Re: Intermittent battery drain

Post by jimi »

Charlieepie wrote: 27/01/22 17:12 jimi - it’s only gone flat once (well, twice now) since battery replacement, and that time the garage jump started it to recover it (they are only 100m down the road) and then charged it - assuming with a trickle charger.

I was planning on just jump starting it and letting the alternator do the work, but I know it’s not healthy to let the battery drain and constantly recharge.
If the battery is flat then your better putting on a charger overnight. The alternator is not designed to charge a flat battery, it will charge it, but to fully charge it you'd need to do a long run (50 miles or more) without using lights, wipers hearer etc.
I'd get your new battery checked by an auto electrician, even a new battery could go faulty, it happened to me about this time in 2020.
Bought a new Yuasa battery for my MK1, about 3 weeks later the car wouldn't start, checked the battery and it was down to 9v, tried charging it overnight and it came up to 13.9v fitted back in the car and it started fine, next day it was back down to 9v. Normally if a 12v lead acid battery does that it's goosed. Contacted the supplier and he sent me a replacement, it's still going strong today :th:
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Re: Intermittent battery drain

Post by jimi »

In these sort of cases fitting an battery isolator is the equivalent of taping a leaking hose, it will stop the leak but doesn't fix the problem. Also means you lose your clock & head unit settings and you have no alarm while the battery is isolated. As a temporary measure it's fair enough, but long term I'd identify and fix the problem.
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