Thread: Do alternators die suddenly or they sometimes fade away?

What F4 describes matches my experience over Christmas. I had the Engel running for a week in the car and I took the car for a run (30 mins or so) to top the battery up. It appeared to do the trick but it soon drained again. The power in the frist battery got so low the Engel stopped working and the voltage meter read 7.5 volts! Not good, especially for a poor old 5 year old battery. I'm going to check the charge again in a couple of days because the car won't be running.

I might arrange to re-wire the accessories plugs off the main and get a dual battery kit that isolates with ignition off - but this simple method I have has worked for me.

Originally Posted by F4Phantom

...................................To protect your batteries you can buy a megapulse which I have seen some good anecdotal results from but have no scientific evidence to show they work. The theory is that it pulses the plates with electricity from the battery itself. This vibration shakes and keeps the sulphur build up off the plates and keeps them operating for many times a batteries normal working life and can bring old batteries back to top condition.

A common 'killer' of lead acid batterys is sulphation. This is where insolubile lead sulphate builds up on the plates of the battery. This is particularly common on batterys that are on 'float'. Floating is when a battery/charger/load are all connected together providing a low or constant supply of power. Emergency standby batterys are a good example.
The build up of insoluble lead sulphate on the plates decreases the batterys effectiveness in two ways. 1/. by decreasing the effective surface area of the batterys plates thereby decreasing maximum available current and 2/. by weakening the electrolyte with the removal of the 'sulphate'. A typical sulphated battery will appear fully charged but has low specific gravity and reduced capacity.
One way of fixing this is to rapidly charge/discharge the battery and basically 'shock' it into recovery. Special gear is needed to do this and it can be quite dangerous if not done properly, though results can be achieved quickly.
A less scary though time consuming method is to use a 'megapulse' type charger. These work by charging a capacitor (essentially a small battery), and then reversing its connection in series with the charging supply and then applying the combined voltage accross the battery. This gives multiple short duration pulses of say 24 volts to the battery. Over a period of time this can be very effective in breaking down insoluble lead sulphate and rejuvinating a sulphated battery.
Don't know if leaving it connected all the time is a good thing or not. Last I looked Jaycar had a Mark 2 model for around $120.

Deano

Originally Posted by JamesH

Thanks everyone.

That was useful. I think Ill wait patiently for my batteries and alternator to clag themselves before replacing them. Will be going outback in July probably maybe before then I will have another think. Peace of mind purchase of new batteries is one thing but new alternator?

Have the alternator overhauled rather than risk it failing whilst outback and rather than getting a new alternator. Brushes, slip-rings and bearings have a limited life but are usually a lot cheaper to replace than a whole new alternator.

I had the Engel running for a week in the car and I took the car for a run (30 mins or so)

You ran the Engel for a WEEK without starting the car? That is about 300 AHs!! What sort of batteries do you have???

You will only have put a surface charge into your batteries in the 30 minutes time, and if you switched to BOTH manually, the high battery would have equalised with the low battery. Now I am only guessing on your battery capacity but if you have an N70ZZ as the aux and an N70 as teh main then they would have a total of about 105 -120AH.( so I am darned if I know how you could run an Engel for a week unless you are in freezing conditions)
If they are lead acid wet batteries they will not take a high charge for long and after 30 minutes you would be lucky to have charged them 1/4-1/3 of full charge as the alternator at best would push say 15AH in whereas the Engel will have used probably 100AH in that period. ( This is probably not the correct way to express it , but will suffice for example )

You would have to run the car for AT LEAST 6 hours or so to fully charge the batteries.
BUT I have never been able to run my Engel for more than 2.5-3 days on my 95AH AGM, and I think you may have forgotten some driving in between.
Regard sPhilip A

Originally Posted by PhilipA

You ran the Engel for a WEEK without starting the car? That is about 300 AHs!! What sort of batteries do you have???


You would have to run the car for AT LEAST 6 hours or so to fully charge the batteries.
BUT I have never been able to run my Engel for more than 2.5-3 days on my 95AH AGM, and I think you may have forgotten some driving in between.
Regard sPhilip A

Sorry Phil I wasn't clear, I ran the Engel for a week but took it for a 30 minute drive somewhere in the middle of that. Also for a couple of shorter ten minute runs. I only have two batteries that I got from the RAC callout dude, I'm sure they are nothing special. The dude said they were good heavy duty batteries they recommend for 4wds, both crankers.

Each time I took it for a run I joined the batteries, and I joined them prior to starting, I doubt it would have turned over on one alone. Before I switched off I isolated them again. They both got a three hour charge driving home.

Anyway, I see now I've been mean and cruel to my poor old batteries and shame on me to suggest that they're under performing.

I used to keep them both joined all the time unless camping and running the fridge but I read here once that a clagged battery will take the goo one out with it so now I default to isolated and join them on weekends to give the second a bit of a charge.

anyone know where you can get MM overhaul parts???? ...ie bearings, brushes, diodes etc,

I found them impossible to find in Australia so I ordered some from Paddock in UK AFAIR.

I was able to rebuild my MM 65amp, and it worked, but I lost confidence in it seeing it failed at 80Kk. I replaced with a Bosch 85amp , but my RRC is a V belt so much easier.
I would suggest that if you are running 2 batteries flat , your alternator will soon die as they are designed to replace starting charge and run accessories, NOT to recharge flat batteries.

AFAIR there are threads on better alternators, so I suggest you do a search.
Regards Philip A
AND maybe buy a second battery electronic controller ,as it will give the alternator an easier time.

I've noticed that on the bigger boats, marine altenators are tending to have in-built battery-charging circuitry.. That is, proper regulation of the charge-current to properly and fully charge the start and aux batteries, not just dump lotsa amps in to replace the starting load.

Maybe space or co$t does'nt warrant them being used on motor vehicles...yet.

The alternate (no pun intended) is to run an inverter to 240v, which feeds a 'proper' charger to feed you AUX battery whilst travelling to/from your camp.

A bit long-winded, though it would preserve the AUX battery's life and capacity. - Especially regarding sulphation.

James in Gosnells

The EH, 95 Vogue SE...with only one, middle-aged battery......