Battery charging question

[xwyokid]

My first battery wall charger went dead on the second use. Minelab sent me another one. Yesterday I started the charging process for a completely dead battery(left the GT on for almost 2 days, by mistake). Manual says 12-14 hrs.for a dead battery. We 've had company all week and not thinking I started the charging too late in the day to complete the charging process before I went to bed. Not knowing if I could leave it plugged in all night I pulled the plug. So...Is there any harm in interupting the charging and then starting again??

 

[Critterhunter]

Nope, no harm. Just do the math. Since the pack was dead due to leaving the machine on, it makes the math pretty solid. Capacity of pack (1000ma, right?) divided by output it says on wall transformer (isn't it 100ma?). If that's the case, 10 hours to charge a completely dead pack, but I'd add a few hours to that as the charging process isn't very efficient and so in reality takes longer. Now just figure how long you had it charging before you disconnected it and then do the math to figure how many more hours for full charge.

Still not sure because I don't use the stock charger or pack for that matter (I use a 3 cell lipo and my own charger)...Does the light go out on the pack for the GT when it's reached peak, or does it just get dimmer when it's peaked? If anybody can clear that up it'll be good to post in the battery sticky for people, as I see that question pop up a lot on here.

And also, those newer wall transformers for the GT have a red light on them, right? Does it stay on all the time then? I would figure it does and doesn't say turn off when the pack is charged or something. I doubt that, since it's just a simple DC wall transformer.

I'm not sure but I think perhaps the charging "circuit" inside the rechargeable GT pack is little more than a diode and a thermistor. The diode prevents the pack from draining should the wall transformer be unplugged from the wall but left plugged into the pack (diodes only let electricity flow one way), and the thermister just opens if the pack gets too hot (reached full charge and is over charging). Not sure if the GT's charging "circuit" is just that, but I at least know Kered said that was all it was on I think the Sovereign XS packs and I think at least some of the Excalibur stock packs. By using a thermister it's a quick/dirty way to turn off the charge when peaked due to the pack getting warm. Only problem with that is that it will cool down and close again, then charge, get hot, and then open again. That's not very good for a pack, and also thermistors will give out and never re-connect after too many cycles like that. That's why I say do the math and don't trust the stock "charger" at least used with some of the older Sovereigns and Excals, if indeed the GT/Elite packs do have a more sophisticated shut off when the pack is peaked? I really should open my rechargeable pack and see just what kind of circuit is in there. Never paid much attention to it.

If somebody can fill in any of these questions it would be great info to post in the battery sticky.

 

[seabee1972]

Just got My GT wed. tried to charge them but would not work. minelab is sending a new battery and charger. I charge it with my RC charger worked great . I just used the clips on the battery make sure you get the + and - right . only had to charge for about a hour. I think I will always use this method

 

[xwyokid]

Nope, no harm. Just do the math. Since the pack was dead due to leaving the machine on, it makes the math pretty solid. Capacity of pack (1000ma, right?) divided by output it says on wall transformer (isn't it 100ma?). If that's the case, 10 hours to charge a completely dead pack, but I'd add a few hours to that as the charging process isn't very efficient and so in reality takes longer. Now just figure how long you had it charging before you disconnected it and then do the math to figure how many more hours for full charge.

Still not sure because I don't use the stock charger or pack for that matter (I use a 3 cell lipo and my own charger)...Does the light go out on the pack for the GT when it's reached peak, or does it just get dimmer when it's peaked? If anybody can clear that up it'll be good to post in the battery sticky for people, as I see that question pop up a lot on here.

And also, those newer wall transformers for the GT have a red light on them, right? Does it stay on all the time then? I would figure it does and doesn't say turn off when the pack is charged or something. I doubt that, since it's just a simple DC wall transformer.

I'm not sure but I think perhaps the charging "circuit" inside the rechargeable GT pack is little more than a diode and a thermistor. The diode prevents the pack from draining should the wall transformer be unplugged from the wall but left plugged into the pack (diodes only let electricity flow one way), and the thermister just opens if the pack gets too hot (reached full charge and is over charging). Not sure if the GT's charging "circuit" is just that, but I at least know Kered said that was all it was on I think the Sovereign XS packs and I think at least some of the Excalibur stock packs. By using a thermister it's a quick/dirty way to turn off the charge when peaked due to the pack getting warm. Only problem with that is that it will cool down and close again, then charge, get hot, and then open again. That's not very good for a pack, and also thermistors will give out and never re-connect after too many cycles like that. That's why I say do the math and don't trust the stock "charger" at least used with some of the older Sovereigns and Excals, if indeed the GT/Elite packs do have a more sophisticated shut off when the pack is peaked? I really should open my rechargeable pack and see just what kind of circuit is in there. Never paid much attention to it.

If somebody can fill in any of these questions it would be great info to post in the battery sticky.

The wall transformer does have a red light. So far the light on the pack is still bright green. Will see if it changes color. I have 2 hours to go until I reach the 12 hour total mark.

 

[Critterhunter]

Yep, when I do charge the stock pack I use my own aftermarket charger. I'll charge it at about 300 to 500ma, which means about two hours or so on a dead pack, give or take depending on how dead it is. That's not pushing nimhs. Many charge at 1C (1 amp on a 1000ma pack) for a 1 hour charge, but to me that's pushing it and over time could lead to less capacity. A sure way to tell if you are pushing a pack is to feel it way into the charging. If it's getting warm or hot you are pushing things. Just like you, I found out I can't charge through the normal charge plug on the pack so I charge via the two main battery leads. There is a link in the battery sticky where I walk people through the way to charge it, and which terminals are what polarity, but most good chargers will tell you if you have it hitched up backwards anyway.

 

[Critterhunter]

Let us know if the green light goes out on the pack when charged or only dims, as I've heard both. That would be good info to post in the battery sticky. Also, the math may say X amount of hours to charge but often it takes an hour to maybe three or so longer due to wasted energy during the process of charging.

 

[xwyokid]

Well, it's been charging for a total of 14 hrs. The light is still as bright as when I started. It's almost 8:30 PM my time. I plan on watcing the Olympics until 11PM. At that time I will pull the plug.

 

[Critterhunter]

If you have a volt meter you can check the status of the charge. Put it on both main battery leads. Note the voltage and write it on a piece of paper. Come back an hour later. Is it the same voltage or lower? Then it's done charging. If it's higher though it's still charging. Write down the number and check again in an hour. The voltage will drop and then stay the same when a nimh or nicad peaks. There are normal little dips in the voltage during charging but that doesn't mean it's done, so you have to come back an hour or so later and see if it's risen anymore. That's how smart chargers know a pack is peaked. They use a thing called the m/v threshold setting. Set too low the pack will false terminate. Set too high and it will never see the voltage drop to indicate the pack is done. For nimhs I normaly set mine at about 5 or 7 m/v. For nicads like 12 or 14, because Nicads drop farther in voltage when peaked than nimhs do. That's why it's dangerous to charge a nimh in a nicad charger, as the charger might never see the peak termination and overcharge the pack. Same deal with the reverse. Putting a nicad in a nimh charger the pack might false peak due to higher dips when charging. The wall transformers for the Sovereign/Xcal shouldn't matter for this, because they are just putting out a steady DC current. Only if the pack has a charging circuit in it would it be important to only use the right replacement type (nimh or nicad) to re-build a pack, and I'm still not sure if the GT/elite pack really has a charging circuit in the pack or just a simple thermister and diode to break the connection when the pack gets hot. I really should open it up and see what's in there. I'm pretty sure at least some packs on older Sovereigns and Excals only had this in them if anything, as I think Kered mentioned that with his XS and Excal. In those cases he was able to charge through the normal charging plug on the pack but had to limit the charge rate (amps) in order to not overheat the pack.

 

[xwyokid]

Well, I don't have a voltmeter to do the test Crittehunter suggested. Maybe I'll run down to Harbor Freight after awhile. After 14 hrs. 15 mins. of charging, the light on the charger is still on and the light on the pack is still as bright as when I started. Oh well.

 

[Critterhunter]

Yea, those multimeters (some) are dirt cheap at harbor tool and freight. Sometimes they even send out a coupon in their ads to get the one for free if you come in.

Just a note...of course when checking the voltage don't unhitch the wall transformer. You need to read the voltage while it's hooked up and charging. Just check via the two main battery leads. The charging point wouldn't work anyway due to it not allowing you to see the pack voltage due to a few components behind that plug.

 

[robby4570]

I have an old Elite, but it uses the same "mains" (wall) power supply which has a RED light that stays on 100% of the time when plugged into the wall whether it's plugged into the battery pack or not. While charging, the GREEN light on the pack wil gradually dim until some point aroud 10 to 12 hours in at which it goes out entirely. I have used the MD for nearly 18 hours on-time with my pack charged in this manner and still had juice to spare.

 

[Critterhunter]

Thanks for that info. So the light probably dims then when it's near charged and is cutting back on the juice perhaps inside the pack where the little circuit is, and then goes completely out when fully charged. Anybody else confirm this, as it's good info to post in the battery sticky once we solidify it as proof positive as to what to expect. That question gets asked a lot so I think it's worth posting in the sticky to head off future questions on that topic.

 

[Critterhunter]

According to the manual for the GT the green light only dims when it's done charging.

Also, on some nimh or nicad packs the stock cheap charger for devices won't recognize or charge the battery if it's completely dead, but with most good aftermarket chargers (such as the cheap $20 Accucel 6) they will recognize and bring a pack back to life that seems dead otherwise when plugged into the stock charger. I've recovered many cordless drill packs that their stock charger didn't recognize or refused to charge that way.

 

[imalookin2]

I have two GT's and both are the same with regards to the lights. You can charge it forever and the green light on the battery will not go out. Mine may dim a bit when charged but not much. I just charge overnight and unplug in the morning. Both chargers are the standard 15 volt 100mA and they have a red light that stays on when plugged in a working outlet, even if the battery is disconnected. That light just tells you the outlet is good. The part number is 0302-0016 for the charger. Be careful using external chargers and battery clips. I saw someone wrote got a full charge in an hour. Slow charging is much better for the battery. Fast charging heats up the cells and may lead to early replacement. My experience is those chargers burn out and get really hot when they do. I had one go bad (got really hot) so I unplug when I leave the house.

 

[xwyokid]

Right or wrong this is what I did to keep the charger cool. I directed a small, (8") fan at the charger and the battery and both items remained just warm to the touch during the charging process.

 

[Critterhunter]

Thanks for the green light info on the pack.

Charging at 1C (1 hour is not really pushing most nimhs or nicads much at all these days)...I do do that with nimh or nicad packs when in a hurry here and there but don't make it an every day thing. Feel the pack. Is it hot? Then you are pushing it. For the GT pack something like 300 to say 500ma (2 hours on a dead pack) isn't really pushing the pack. Charging say a 1000ma pack at 1amp (1C) isn't going to shorten the life unless you are doing that every single charge, and even then most modern cells are easily able to handle that. Still, to be sure I'm being easy on my packs for longest life possible I tend to shoot for say 1/2C or less or so just to be sure the pack is being treated real well. Some even charge at say 2C and still report long life out of modern nimhs or nicads, and some in RC charge at much higher rates than that, like 5C...But they are using cells they know are built to take that kind of punishment.

The wall transformer for the Excal or GT isn't putting out such little amps to be easy on the battery. It's more for the fact that cheap wall transformers like that can't put out too much current. Charging at 100ma is well BEYOND the lowest level needed to be easy on modern nimhs or nicads. Pointless in fact. Once you get down to about 1/2 capacity in amp charging rate (about 500ma for a 1000ma pack) you are well into the safe zone as far as being easy on a pack and are not going to see longer life by doing 100ma amp rates on 1000ma cells like this.

And, it's also so that if the pack doesn't have a charging circuit in it (say Excals or older Sovereigns before the Elite, and the GT/Elite packs MIGHT not cut off the current when full but I still haven't confirmed that yet) to cut off the current when the pack is peaked (meaning no way for it to tell it's charged and shut down) it won't fry the pack by still putting out a higher amp charge rate.
By using a amp rate that is well down into the trickle level you aren't over juicing the pack with a higher charge rate once peaked if the charging process has no way to know when to shut down. It's a cheap way to supply you with a "charger" that is nothing more than a wall transformer, without needing to add circuits to monitor and shut off the current when peaked. By keeping the amp rate so low they eliminate the need for being able to tell when to shut it down.

For instance, Nicads like to be put on a trickle charge like the low current output of the stock wall transformer after they have peaked to maintain them ready for action at any time. It doesn't hurt them to sit on a trickle charger all the time so long as the current is very low like that. But all I've read about nimhs says they don't like to be trickle charged after they are peaked. For that reason old Nicad chargers often would charge at a high amp rate and then switch to a trickle charge when the pack peaked, so it was sitting there ready for action at all times.

But chargers that have nimh ability as well will often give you the ability to turn off the trickle after the peak, as that can lead to shorter battery life over time with a nimh being trickle fed for days on end after a peak. For example, many nicad chargers will charge at say 500ma and then when the pack has peaked switch to say 100ma to maintain the pack while it sits for days ready for use. The ones that can do nimhs give you the option to shut off that trickel charger after the pack has peaked. That's why I say if your Sovereign or Elite doesn't have a charge circuit cutting off the current after it's peaked (I still don't know but plan to check it out on mine to finally nail that down) and you are using nimhs in it don't let it sit on that wall transformer for hours or days longer after it's peaked. Bad for the battery, and I still don't like doing that with nicads either.

 

[imalookin2]

WOW. That is long. Just charge the battery for 12 hours and unplug. The stock charger works fine and is simple. I stick with what works that is why I use a GT.

Thanks for the green light info on the pack.

Charging at 1C (1 hour is not really pushing most nimhs or nicads much at all these days)...I do do that with nimh or nicad packs when in a hurry here and there but don't make it an every day thing. Feel the pack. Is it hot? Then you are pushing it. For the GT pack something like 300 to say 500ma (2 hours on a dead pack) isn't really pushing the pack. Charging say a 1000ma pack at 1amp (1C) isn't going to shorten the life unless you are doing that every single charge, and even then most modern cells are easily able to handle that. Still, to be sure I'm being easy on my packs for longest life possible I tend to shoot for say 1/2C or less or so just to be sure the pack is being treated real well. Some even charge at say 2C and still report long life out of modern nimhs or nicads, and some in RC charge at much higher rates than that, like 5C...But they are using cells they know are built to take that kind of punishment.

The wall transformer for the Excal or GT isn't putting out such little amps to be easy on the battery. It's more for the fact that cheap wall transformers like that can't put out too much current. Charging at 100ma is well BEYOND the lowest level needed to be easy on modern nimhs or nicads. Pointless in fact. Once you get down to about 1/2 capacity in amp charging rate (about 500ma for a 1000ma pack) you are well into the safe zone as far as being easy on a pack and are not going to see longer life by doing 100ma amp rates on 1000ma cells like this.

And, it's also so that if the pack doesn't have a charging circuit in it (say Excals or older Sovereigns before the Elite, and the GT/Elite packs MIGHT not cut off the current when full but I still haven't confirmed that yet) to cut off the current when the pack is peaked (meaning no way for it to tell it's charged and shut down) it won't fry the pack by still putting out a higher amp charge rate.
By using a amp rate that is well down into the trickle level you aren't over juicing the pack with a higher charge rate once peaked if the charging process has no way to know when to shut down. It's a cheap way to supply you with a "charger" that is nothing more than a wall transformer, without needing to add circuits to monitor and shut off the current when peaked. By keeping the amp rate so low they eliminate the need for being able to tell when to shut it down.

For instance, Nicads like to be put on a trickle charge like the low current output of the stock wall transformer after they have peaked to maintain them ready for action at any time. It doesn't hurt them to sit on a trickle charger all the time so long as the current is very low like that. But all I've read about nimhs says they don't like to be trickle charged after they are peaked. For that reason old Nicad chargers often would charge at a high amp rate and then switch to a trickle charge when the pack peaked, so it was sitting there ready for action at all times.

But chargers that have nimh ability as well will often give you the ability to turn off the trickle after the peak, as that can lead to shorter battery life over time with a nimh being trickle fed for days on end after a peak. For example, many nicad chargers will charge at say 500ma and then when the pack has peaked switch to say 100ma to maintain the pack while it sits for days ready for use. The ones that can do nimhs give you the option to shut off that trickel charger after the pack has peaked. That's why I say if your Sovereign or Elite doesn't have a charge circuit cutting off the current after it's peaked (I still don't know but plan to check it out on mine to finally nail that down) and you are using nimhs in it don't let it sit on that wall transformer for hours or days longer after it's peaked. Bad for the battery, and I still don't like doing that with nicads either.

 

[Rick(ND)]

I too agree to stick with the factory charger made for the Minelabs as they work great for most of us. I have a older Sun Ray SR 12 charger that is not made anymore, but wish they did as it would discharge a battery to a safe level and then recharge to a safe level and go to a pulse trickle charge to condition a battery, or it would just charge the battery. I tried others and ruin a lot of batteries and even blew up a 9 volt battery as it was charging too fast. I also have one special made for my 2600 MhA battery which recommends 10 hours of charging and it too goes to a pulse trickle charge when fully charged, so they too recommend the charging is no more than 10% of the capacity the way it looks as i told them I wanted to charge 8 -AA 2600 Mha at a time with it..

Just thinking I still can recharge some of the nicads made for the XS back in 1996 with the Sun Ray charger as I just did for one of the locals that still have the factory battery yet. I have charging cradles or stations for the GT and the Explorer pack too I use on my Sun Ray SR 12 charger and never had a problem charging yet, but it is at around 400 Mha.