Saving a "dead" battery

[William_H]

Battery chargers

What we really have is the fact that modern "do it all for you" battery chargers can not cope with a very low voltage deeply discharged battery. However some can. If they can it does not mean they are good at reviving a battery just able to recharge.
The U tube video has a horrible error in it. Connecting a good battery in parallel with a deeply discharged battery is simply going to charge the flat one from the good. The current that flow depends on the resistance of the cables. (pretty heavy in the video so very high current) a real risk of spark and explosion if there is any hydrogen around from charging. If you need to do this trick then use something like a headlight globe 50w in one lead so that current is limited to less than 4 amps. The dead battery will rise in volts at the expense of the good battery but slowly.
Some battery chargers will simply detect an overload if connected to a low voltage battery because current is too high. If it is that simple use a headlight globe again to limit current until the voltage rises high enough in the battery that you can connect the charger direct.
Someone had a charger older than "God's dog" ( I haven't heard that term before). I prefer the old style non auto. provided you have an amp meter and remember to turn it off you can charge batteries fast and safely. The pulsed nature of the current giving more current at end of charge. good luck and be careful olewill

 

[Nicholas123]

What we really have is the fact that modern "do it all for you" battery chargers can not cope with a very low voltage deeply discharged battery. However some can. If they can it does not mean they are good at reviving a battery just able to recharge.
The U tube video has a horrible error in it. Connecting a good battery in parallel with a deeply discharged battery is simply going to charge the flat one from the good. The current that flow depends on the resistance of the cables. (pretty heavy in the video so very high current) a real risk of spark and explosion if there is any hydrogen around from charging. If you need to do this trick then use something like a headlight globe 50w in one lead so that current is limited to less than 4 amps. The dead battery will rise in volts at the expense of the good battery but slowly.
Some battery chargers will simply detect an overload if connected to a low voltage battery because current is too high. If it is that simple use a headlight globe again to limit current until the voltage rises high enough in the battery that you can connect the charger direct.
Someone had a charger older than "God's dog" ( I haven't heard that term before). I prefer the old style non auto. provided you have an amp meter and remember to turn it off you can charge batteries fast and safely. The pulsed nature of the current giving more current at end of charge. good luck and be careful olewill

I'm pretty confused by all this.Could you not just connect the positive on a new charged up battery to the positive of the old battery & the same for the negative then & let the new battery charge up the old if that is the case,then re charge the new as it becomes discharged? As the old ones voltage rises to above 12 volts or whatever the magical figure is then connect it directly to the charger?

 

[kindlebooks]

This sounds amazing to me,does it mean that you can resurrect old batteries that have been dormant in a boat for years?How do you tell if a battery really is beyond hope? & finally how much does this wonder machine cost?
Yours in anticipation

A mate asked me to do the magic on his battery (high voltage and amps for a few seconds etc), but his battery had been left discharged for 3 years. Was reading 3 Volts! Shame because it was a good battery once.

Dead.
Low fluid.

Suspect the plates had shorted.

Some can be saved, others not. A really really low voltage means give up.

 

[TrueBlue]

I'm pretty confused by all this.Could you not just connect the positive on a new charged up battery to the positive of the old battery & the same for the negative then & let the new battery charge up the old if that is the case,then re charge the new as it becomes discharged? As the old ones voltage rises to above 12 volts or whatever the magical figure is then connect it directly to the charger?

The point was not how to deal with the good battery after the process had completed,
but rather that a very high current is likely to pass from the good to the bad, which could:-

• cause a big fat spark when connecting AND disconnecting. Sparks = possibility of a big bang....
• damage the good battery, being not designed to pass currents for any length of time

 

[savageseadog]

This sounds amazing to me,does it mean that you can resurrect old batteries that have been dormant in a boat for years?..............
Yours in anticipation

If Jesus wanted a battery charger he would have chosen one of those

 

[Nicholas123]

The point was not how to deal with the good battery after the process had completed,
but rather that a very high current is likely to pass from the good to the bad, which could:-

• cause a big fat spark when connecting AND disconnecting. Sparks = possibility of a big bang....
• damage the good battery, being not designed to pass currents for any length of time

OK well that makes sense to me except that you would expect those 'experts' who promote that procedure on youtube to know that & maybe it is just a matter of doing it in an airy place so that the breeze blows away any dangerous gasses?

 

[Nicholas123]

If Jesus wanted a battery charger he would have chosen one of those

Please spare me,I am getting visions of Jesus being resurrected by battery charger,this is quite complicated enough already.

 

[Heckler]

This sounds amazing to me,does it mean that you can resurrect old batteries that have been dormant in a boat for years?How do you tell if a battery really is beyond hope? & finally how much does this wonder machine cost?
Yours in anticipation

What happens with cheap chargers is that they are underpowered and under controlled. If you get a dead battery to charge it will probably take loads of amps on start of charge and will knacker the cheap simple charger. So they put an under voltage control iun them, dead battery means it wont start charging, no voltage to activate the charger. Peeps think the battery uis dead. Proper chargers like the lidl one will start charging even if the battery is flat. So peeps think it is a battery reviver when in fact it is only doing what it is supposed to d!
Stu

 

[William_H]

OK well that makes sense to me except that you would expect those 'experts' who promote that procedure on youtube to know that & maybe it is just a matter of doing it in an airy place so that the breeze blows away any dangerous gasses?

Now who is the optimist. The internet is available for anyone to say whatever they like be it right or wrong. Just because he says he is an expert doesn't make him one. He might also be described as a salesman.
Anyway in fairness the procedure is dangerous in proportion to the degree of discharge of the dead battery and I think he just omitted to mention the dangers. Like I said use a resistor (lamp) to gentle the equalisation process. olewill

 

[oldbilbo]

.....The U tube video has a horrible error in it. Connecting a good battery in parallel with a deeply discharged battery is simply going to charge the flat one from the good. The current that flow depends on the resistance of the cables. (pretty heavy in the video so very high current) a real risk of spark and explosion if there is any hydrogen around from charging.....

Am I glad I came back here this morning to read this, thanks!

I have a 'good' battery and a 'duff' one in the boat, and a Lidl charger. I was heading out in the rain with a set of jump leads to connect the two batteries in parallel, then the charger, as per the YouTube vid..... Now I'll do something else entirely.

I have a 'bilge blower' device to fit. P'rhaps I'll start another thread about the merits of these.....

 

[Nicholas123]

If the fault is those super dupa modern battery chargers not kicking in on deeply depleted batteries how about an old trickle charger that I have had for donkeys years? (it just says GP4 on the front & on the back says "Output 12 VOLT 4 AMP RMS.")

 

[Nicholas123]

Now who is the optimist. The internet is available for anyone to say whatever they like be it right or wrong. Just because he says he is an expert doesn't make him one. He might also be described as a salesman.
Anyway in fairness the procedure is dangerous in proportion to the degree of discharge of the dead battery and I think he just omitted to mention the dangers. Like I said use a resistor (lamp) to gentle the equalisation process. olewill

I was confused by talk of wiring in globes so if you could go into a bit more detail I would be grateful (there is a super dupa battery charger on the boat which is in Belgium......it was so super dupa that it might even brew up a cup of tea while you are waiting)

 

[chrishelen]

Batteries are so cheap, and such a vital item when you are out at sea, that I suggest you just buy new ones. I do use older batteries on my caravan, but it is on a site with 240 volt so not a worry!!

It now cost more to fill my car with Diesel than to buy a new battery.

 

[G12]

No they are not wonder machines.


Sometime after that I noticed a Ring Smartcharger in Halfords. I bought it.
I did not know at the time that there was a range with different outputs but I would have chosen the 8 amp one that I had bought any way.

I could have shopped around and saved money but i was in the shop and it sort of said, "buy me."

More recently Ring have launched a Smartcharge + range. I beleive one of those was voted "best buy" by one of the magazines.

None of them would be suitable for permanent installation IMHO. They draw a small but significant current from the battery when not powered up.
If the power is disconnected they default to they lowest output setting when repowered.

Halfords currently have the 12 amp version of the Smartcharge + on their website
http://www.halfords.com/webapp/wcs/..._productId_821951_langId_-1_categoryId_255205

From time to time Lidl have their little one on offer
Aldi often offer something similar

I have the 12 amp Smartcharge+. It does return to whatever settings you left it on if the power gets knocked off. It's on for 8 hours a day on a timer with my dehumidifier. This keeps the batteries topped up and it also pulses them to help get rid of sulphation. Not a bad bit of kit really. I originally bought a 16 amp version and had to send it back as it dies within about 2 hours. Apparently they've had loads sent back with the same issue which is why I bought the 12A version second time around.

 

[William_H]

I was confused by talk of wiring in globes so if you could go into a bit more detail I would be grateful (there is a super dupa battery charger on the boat which is in Belgium......it was so super dupa that it might even brew up a cup of tea while you are waiting)

OK you have a 12v battery showing 3 volts you hard wire it in parallel with a good battery of 12.5 volts.
The current flow is going to depend on the resistance of the jumper leads. Really low if they are used for starting a car. and the internal resistance of the good battery also really low if used for starting an engine. and the voltage difference between the 2 batteries...
The initial current flow will be huge. Sure at several hundred amps charging current the flat battery if not dud will soon rise in voltage and as it does so the current will fall. But it is all very brutal on both batteries. Further if the flat battery has a dud (shorted) cell then it will continue to discharge the good battery cooking the bad one.
If you connect a resistor between the battery positive jumper leads like a 50w car headlamp then the max current that can flow will be 4 amps. This will charge the flat battery up to useful voltage fairly quickly but not at a destructive current.
Likewise if you have a crude charger then fit a resistor or lamp in series with the positive lead to limit the charge current until the flat battery has a better voltage. 10 mins should do it. Then connect as normal.
The crude charger when connected to a flat battery will try to charge at a very high current. This will result in operating an overload switch a fuse or it will just get hot.(this may or may not be OK)
Anyway when charging batteries you need an amp meter and a volt meter and clock just think about what is going on. Relate charge current and time to AH capacity and don't try to charge to quickly. Or just leave it to the inteligence of the charger. (which may be OK) good luck olewill

 

[Nicholas123]

OK you have a 12v battery showing 3 volts you hard wire it in parallel with a good battery of 12.5 volts.
The current flow is going to depend on the resistance of the jumper leads. Really low if they are used for starting a car. and the internal resistance of the good battery also really low if used for starting an engine. and the voltage difference between the 2 batteries...
The initial current flow will be huge. Sure at several hundred amps charging current the flat battery if not dud will soon rise in voltage and as it does so the current will fall. But it is all very brutal on both batteries. Further if the flat battery has a dud (shorted) cell then it will continue to discharge the good battery cooking the bad one.
If you connect a resistor between the battery positive jumper leads like a 50w car headlamp then the max current that can flow will be 4 amps. This will charge the flat battery up to useful voltage fairly quickly but not at a destructive current.
Likewise if you have a crude charger then fit a resistor or lamp in series with the positive lead to limit the charge current until the flat battery has a better voltage. 10 mins should do it. Then connect as normal.
The crude charger when connected to a flat battery will try to charge at a very high current. This will result in operating an overload switch a fuse or it will just get hot.(this may or may not be OK)
Anyway when charging batteries you need an amp meter and a volt meter and clock just think about what is going on. Relate charge current and time to AH capacity and don't try to charge to quickly. Or just leave it to the inteligence of the charger. (which may be OK) good luck olewill

Thanks you have given me something to think about.I am very reluctant to throw away two what look like almost brand new marine batteries that ordinarily would be more than I can afford.

 

[dolphin]

flat battery

thanks for reply

what i have done up to now - connecting directly the charger do not do the job !
the battery keep for more the 24 hours the voltage of about 6.5 V after disconnect

now , i have connected (positive) 2 x 55 W lamps and charger have about 2.5-3.0 A !
will see what will be the result and revert with outcome (the battery is 105 ah)

regards