battery murderer

[John V]

And you think that some people on this forum bash batteries.....

 

A second hand generator (nice one about, 10Kva barely run in) delivered to the boatyard.

The battery was flat so they attached a temporary one to check it ran and then took the (totally flat !!!) one and put in on charge (at some enormous initial current from a big simple charger)

The next morning I got a panic call

When they put the re-charged battery on the generator, the lead to the alternator started to smoke !!!

Guess what they had done

[WotEver]

Did it kill the alternator?

[John V]

amazingly it survived....though what it has done to its long time survival I don't know and I only had a crap meter with me so it does need the charging volts checking properly

[WotEver]

If the nice new battery (with the correct polarity) starts getting warm you won't need a meter

[John V]

[Sir Nibble]

Interestingly, I have found that totally discharging a battery and running it through a few reverse charges often shifts sulphation.

[RLWP]

Well, that answers a question I had the other day. You can charge a lead acid battery backwards

 

Richard

[WotEver]

Well, that answers a question I had the other day. You can charge a lead acid battery backwards

 

Richard

It doesn't work very well though.

[John V]

and goodness only knows what it does to it's life expectancy

 

(If Sir Nib's has tried it maybe he would let us know) sound a rather drastic cure though !!!

Edited January 25, 2016 by John V

[Sir Nibble]

It's no big deal at all. Just run the battery right, right down so it won't light a test lamp then pop it on a charger. It will show a few amps of short circuit current so you just wait for that to reduce and bring the charger in gently. It's not in any way harmful in my experience and sometimes it delivers spectacular results.

Charging a battery backwards requires that

a/ You really know what you're doing

or

b/ You really have no idea what you're doing.

[WotEver]

Charging a battery backwards requires that

a/ You really know what you're doing

or

b/ You really have no idea what you're doing.

As with so many things in life... bringing up kids, getting drunk, driving in France...

[John V]

Well spectacular results certainly described the scenes of panic at the boatyard when I walked over there

 

It must be 50 years or more since I came across anyone else doing it (I was just pleased I worked out what they had done wrong so quickly....lots of brownie points!)

 

Well, they certainly didn't bring the charge current in gently, their idea is that BIG battery chargers on MAX are best, irrespective, of the size of the poor little battery.

I don't bother commenting anymore, I've got used to seeing the battery man's delivery van

[KevMc]

OK .. I'm going to be the one that asks .... what had they done ?

[RLWP]

OK .. I'm going to be the one that asks .... what had they done ?

 

Connected the charger the wrong way round

 

Richard

[Sir Nibble]

Charged the battery back to front so that when it was reconnected it short circuited through the alternator rectifier.

[KevMc]

I'm guessing it is a simple mistake to make if you aren't aware of the risk

[Sir Nibble]

Well yes, in the same way that driving on the wrong side of the road is understandable if you don't know the risks. If you don't know that it's important to connect a charger the right way round and how to identify which way that is then you really don't know how to use the equipment properly and safely and should leave it alone.

[KevMc]

Well yes, in the same way that driving on the wrong side of the road is understandable if you don't know the risks. If you don't know that it's important to connect a charger the right way round and how to identify which way that is then you really don't know how to use the equipment properly and safely and should leave it alone.

 

After a number of close shaves I realized it is usually cheaper and often safer in the long run to get someone to do the job properly first time

[Loafer]

Useful to know all that. I never knew you could charge a battery backwards, but it does make sense.

[cuthound]

At the dawn of my career, I vaguely recall working on a power system which used "counter emf cells".

 

These were connected the opposite way around to most of the cells in the battery, presumably to reduce the voltage, although there must have been easier ways of doing this. I remember these cells gassing vigorously and requiring frequent top ups with deionised water.

[MtB]

Useful to know all that. I never knew you could charge a battery backwards, but it does make sense.

 

Are both the plates in a lead acid cell the same then? The cell is physically symmetrical?

 

I always imagined the plates were different.

[Loafer]

 

Are both the plates in a lead acid cell the same then? The cell is physically symmetrical?

 

I always imagined the plates were different.

 

They certainly end up different. When fully charged though, they're pretty similar. Or it's the other way round! All that might be *****hit!

[cuthound]

The batteries I have seen (large open cells, opened faulty SLA's and cells with clear cases) all had symetrical plates, made me of pure lead, or dosed with either calcium or antimony, with the active material held in pockets in the plates.

 

When discharged both plates are a grey colour. When charged to positive plate turns to a brown colour. Sulphated plates are a lighter brown or even grey in colour and feel gritty to touch.

 

Edited to add the last para.

Edited January 25, 2016 by cuthound

[Neil Smith]

I assume you then flatten it again then charge it the correct way round and all is back to normal.

 

Neil

[Sir Nibble]

Both plates are lead. When charged the +ve plate is chemically changed to lead peroxide and the negative to something called "spongy" lead. Batteries are manufactured in a fully charged state (dry charged). If you discharge the battery both plates turn to lead and sulphate is deposited. So a discharged battery is symmetrical and can be charged either way. There will be other materials in the plates to better suit them to their role but really any old bits of lead tossed in acid is a cell.

I assume you then flatten it again then charge it the correct way round and all is back to normal.

 

Neil

Hopefully yes.