D Lithium rechgeable 3.7v 7500mah-Feeler...

[DocD]

hi, here the email from the company

Dear Phil

Thanks for your call today. Following our conversation,
Please note that both cells are fitted with “K2” protection as standard.
Also please note the INR34600 cell has passed UN transportation testing, not undergoing as suggested in our data sheet.
I confirm that the unit price of either cell type for a quantity of 50 off is £30 ex works. I also attach our Terms and Conditions for your information.

The cells would be shipped in Class 9 boxes of 25 by surface transport. Our estimated costs for shipping are:

50 cells to Guildford £26.24
25 cells to Guildford £26.24
25 cells to US (NY) £275 , air transport. For sea transport a similar price, if not higher as sea freight is set up for larger quantities generally.
Transport companies tell me there is a minimum price due to the hazardous goods documentation and customs charges, but as the quantities rise the surface transport will become more economical and the air less so .
The figure quoted would be almost exactly the same for 250 cells as for 25 cells, due to the minimum charges

If you wish to proceed, please send an order and we will respond with a pro-forma invoice for you up-front payment (since you are a new customer).

As you can see they can go by air this works out if 25 batteries at £11.00 /50 batteries £6.50 and so on.
I think this is the way to send this battery as getting caught by US custom is a very bad idea and the fines only upto $50.000 dollars

nominal voltage:3.55v
rated capacity:7.5ah
height:60.1mm +/- 0.2mm
diameter:33.9mm +/- 0.1mm
weight:143g
discharge temp range:-40c to +70c
charge temp range:0c to 50c
max continuous discharge current:10A
end of discharge voltage:2.5v
end of charge voltage:4.2v +/- 0.05v
VERY IMPORTANT
the battery has an internal fuse at 12amps if this cell shorted out,or chargeing input amps is over 1.75 amps YOU can kill this cell
this internal fuse is a one shot deal it will not reset because it a safety fuse
this is why plasaman battery died

more info from CEO, pluse amps up to 18amps 3 second pluse and will hold up to 14amps

cheers DocD


cheers DocD

 

[plasmaman]

Don't forget the VAT Phil when you are doing your sums....

 

[DocD]

Good point there, as there going over sea then no vat on the USA batteries just to ask how did you kill that cell of your's? cheers DocD

 

[SilverFox]

Hello DocD,

If this is correct...

VERY IMPORTANT
the battery has an internal fuse at 12amps if this cell shorted out,or chargeing input amps is over 1.75 amps YOU can kill this cell
this internal fuse is a one shot deal it will not reset because it a safety fuse

cheers DocD

You should add an alert that people should be very careful when choosing the charging current.

If I were to charge a cell like this on a hobby charger, I would set the charger to 5 amps and go from there. The 1.75 amp restriction on charge rate makes charging setup very important.

Also, it is a somewhat normal practice to parallel cells for charging. When hooking cells in parallel, you can exceed the 1.75 amp restriction during the surge current if the voltages of the cells are a little different.

Perhaps you can check on this again and make sure this is the correct limit on charging current.

Tom

 

[DocD]

Hi silverfox, comany say 1.75 max charging amps for 1 cell as these cells are mainly use in battery packs with RC type protection set up for muilt cell but as we know most are square and we need round.
but i think this has been talk about on page 4 by lux luthor and jimmy m but maybe not in the same way?
but i will check will the company about the max charge rate with 2,3,4,5,6 cell in parallel but this may take a little time to get a answer
cheers Docd

 

[DocD]

Hi, i have PM all that showed a interest all the way back in 2007 up till 2009,
here's hoping some still have some cash a need for these cells
Will let all know soon on the numbers.
cheers DocD

 

[DeLighted]

I'd be interested in 5.



Thanks, Kent :wave:

 

[DocD]

The answer from the ceo on sliverfox post below

"You should add an alert that people should be very careful when choosing the charging current.

If I were to charge a cell like this on a hobby charger, I would set the charger to 5 amps and go from there. The 1.75 amp restriction on charge rate makes charging setup very important.

Also, it is a somewhat normal practice to parallel cells for charging. When hooking cells in parallel, you can exceed the 1.75 amp restriction during the surge current if the voltages of the cells are a little different.

Perhaps you can check on this again and make sure this is the correct limit on charging current."

CEO anwser
when chargeing in parallel the charging amps is per cell
1 cell =1.75
2 cells=3.50
3 cells =5.25
and so on.
the discharge amps is the same
1 cell =12amps
2cells =24amps
3 cells = 36amps
and so on.

When chargeing or place in two cell together for chargeing, balance voltage between cell is a must, but he is getting back to me after the teck guy check this out
But in there normal use for these cell they are built in a battery pack and are never disconected after they are assemble so chargeing surge is not an issue.
the internal fuse is a thermal type and help to discharge the voltage from the cell when a over voltage happens this is the reason why max chargeing amps is 1.75 as it's the max it can handle with the control from the protection circuit.

Please note this info is from the CEO of the company.

I hope this helps silverfox cheers DocD

 

[SilverFox]

Hello DocD,

In that case, make sure you warn everyone that the maximum charge current is 1.75 amps. Or, if you parallel cells, multiples of 1.75 amps. And be sure to warn about paralleling cells of unequal voltages.

Tom

Upon thinking on this a little more, I am not sure they are on the same page that we are on. They may only be able to handle 1.75 amps through their balance circuits, and are listing that as a maximum charge rate. It seems to me that if a cell can be discharged at 12 amps, it could handle a 0.7C charge rate. Does anyone have any of these cells? If so, what charge rate was used to charge them and how well did it work out?

At any rate, the bottom line is that you have to go with what they say, so be sure to warn about the maximum charge rate.

 

[spencer]

If the cells are protected, wouldn't the protection circuit kick in before this fuse blew? Or is the protection in these cells only for overcharge/discharge?

 

[DocD]

As with all things, what i am learn is this

1 A high discharge li-ion d cell is not yet possable, no?, it's just no one has made it yet.

2 If it could be made, it's not going to be in this chemistry there are better ones.

3 The market is limited to small numbers and even smaller number of uses.

4 Other chemistry are now available with better discharge rate but not the same voltage and are safe, meaning it will not go bang or burn your house down.

5 The bigger the cell gets it's going to hit limits,i mean to say for the greater power stored is off set against discharge rate befor thermal runaway happens and we all know what that means.

6 The protection gives two things to this battery total safety and overcharge, this cuts in at 4.35 volts and 1.75amps just do-not exceed this rule or you risk blowing that fuse, stop at 4.19 volts you just have to follow the instructions

At this time it's the most bang for a lot of bucks and you still have to follow the rules or better just to give the cost of the cell to the homeless.
There is a super discharge cell in the pipe line, but less power and it's going to be years befor we see it in the open market, but we have it other types of battery for heavy use.

i've charged the three cell with a BC6 at 1.5 amps stoping at 4.19 volts and this is all i need, i'll have an AW soft start and a 12v 75watt osram i'll see how this work out at the weekend
cheers DocD

 

[plasmaman]

Hello DocD,

In that case, make sure you warn everyone that the maximum charge current is 1.75 amps. Or, if you parallel cells, multiples of 1.75 amps. And be sure to warn about paralleling cells of unequal voltages.

Tom

Upon thinking on this a little more, I am not sure they are on the same page that we are on. They may only be able to handle 1.75 amps through their balance circuits, and are listing that as a maximum charge rate. It seems to me that if a cell can be discharged at 12 amps, it could handle a 0.7C charge rate. Does anyone have any of these cells? If so, what charge rate was used to charge them and how well did it work out?

At any rate, the bottom line is that you have to go with what they say, so be sure to warn about the maximum charge rate.

I already have these cells. I only charge them individually, and never at more than 1amp. I have never had an issue (other than the fuse I blew on one, but that was me being particularly careless working on a metal bench - duh)

 

[SilverFox]

Hello Plasmaman,

I am just trying to understand how they manage to have different circuit paths for charging and discharging. If both paths are the same, then charging at 5 amps would not be a problem. What they are indicating is that the current follows a different path during charging, and I am just trying to understand how they do that...

Tom

 

[Morelite]

Maybe a diode on each path but in opposite polarity.

 

[DocD]

hi sliverfox your right, the battery does act in both ways when the overcharge comes into play
the company say the chargeing is pluse on and off in time segments, and in the off time draws power from the cell to discharge it and when this is done back on to the chargeing side of this closes allowing the cell to charge
the fuse/circuit is thermal base and must covert excess voltage and amps into small amount of heat not enough the blow this fuse or raise the temp any were near danger levels, chargeing at say 5 amps the circuit may not protect the cell as the internal temp raised and blows the fuse befor the big bang happens, but this is how i understand it works?
cheers DocD

 

[petrev]

Hi

PDF Datasheets

K2 Protection Circuit
http://www.mediafire.com/file/nk2zymenmm0/AGM-v3enhanced_k2.pdf

Cell Data for similar cell (34600-5.2Ah)
http://www.mediafire.com/file/kmttezj00mn/AGM-v3ICR34600.pdf

Data graph shows charging at C/3

K2 datasheet suggests to me that circuit acts as charger/discharger to dissipate overcharge current and that is the limiting factor for damage - may not be an issue with a correctly calibrated and acting charger that is cutting off below the set overcharge protection level ?

Cheers
Pete

 

[SilverFox]

Hello DocD and Pete,

OK, now this is making sense...

In order to enhance safety, the IEC has added a "continuous charge" criteria to the safety tests done on Li-Ion battery packs.

The way that I read this is that when the cell reaches the overcharge detection voltage, the protection circuit will kick in and bleed the voltage down to the release voltage. It can only dissipate a certain amount of current. If that current is exceeded, the fuse blows and the cell no longer works.

The safest way to insure that maximum current is not exceeded is to simply limit the charge rate to the maximum dissipation rate. This way, if your charger malfunctions and does not terminate, you limit the damage. This also allows for the use of less sophisticated chargers.

The next question is if the protection circuit is always activated, or if it only becomes activated during an overcharge condition?

If my charger uses the CC/CV algorithm, and never exceeds 4.200 volts at any time during the charge, I don't think any current flows through the protection circuit safety fuse, so there should be no restriction on the charge current, up to the normal maximum of a 1C rate.

This brings up a specific question...

If the cell voltage is 3.60 volts, and the charging rate is 7.5 amps, will the protection circuit fuse blow?

I don't have the answer to this question, but I would think that there would be no problem. The charge current limit only should kick in when the protection circuit is activated. As I mentioned earlier, with a 7.5 Ah cell I wouldn't think twice about charging it at 5 amps. However, my charger does not exceed 4.200 volts at any time during the charge, so it is my thought that the protection circuit would never be activated.

Tom

 

[petrev]

Hello DocD and Pete,

OK, now this is making sense...

In order to enhance safety, the IEC has added a "continuous charge" criteria to the safety tests done on Li-Ion battery packs.

The way that I read this is that when the cell reaches the overcharge detection voltage, the protection circuit will kick in and bleed the voltage down to the release voltage. It can only dissipate a certain amount of current. If that current is exceeded, the fuse blows and the cell no longer works.

The safest way to insure that maximum current is not exceeded is to simply limit the charge rate to the maximum dissipation rate. This way, if your charger malfunctions and does not terminate, you limit the damage. This also allows for the use of less sophisticated chargers.

The next question is if the protection circuit is always activated, or if it only becomes activated during an overcharge condition?

If my charger uses the CC/CV algorithm, and never exceeds 4.200 volts at any time during the charge, I don't think any current flows through the protection circuit safety fuse, so there should be no restriction on the charge current, up to the normal maximum of a 1C rate.

This brings up a specific question...

If the cell voltage is 3.60 volts, and the charging rate is 7.5 amps, will the protection circuit fuse blow?

I don't have the answer to this question, but I would think that there would be no problem. The charge current limit only should kick in when the protection circuit is activated. As I mentioned earlier, with a 7.5 Ah cell I wouldn't think twice about charging it at 5 amps. However, my charger does not exceed 4.200 volts at any time during the charge, so it is my thought that the protection circuit would never be activated.

Tom

Hi Tom

That's my reading of the specs but a definitive answer should be obtained from AGM Tech with a carefully framed question ? or a cell could be (possibly) sacrificed to the normal 1C max charge rate under test conditions ! ! ! Potentially expensive test though . . .

There may be other factors such as cell warming during charge in these rather larger cells ! ! !

Cheers
Pete

 

[DocD]

hi been back on the phone with AGM and the ceo said the following on the questions
1 K2 only becomes actvie when a cell voltage or charging voltage is great then 4.35 volt at this time any charging amps over 1.75amps will cause the fuse to blow.
2 you can charge the cell at 3amps or 5amps, its the charging voltage that is most important allowing this to go over 4.35volts when charging and the fuse will blow
3 the charger input voltage IS NOT the same as cell voltage, the terminal cell voltage is 4.19 volt and but the voltage from the charger must NOT exceed 4.35 volts if this possable, you can charge the cell at 3 amps, 5 amps
5 if your charger voltage must never be above 4.35 volt
so in summary
input charge volts must not be over 4.35v at any time during the charging cycle
choose the charging voltage for this cell at 4.2v nice and safe and its below the K2 activate voltage at 4.35v
Cell voltage hot of the charger should be 4.2 volt max.
i hope this help and once again silverfox is right in his thinking
cheers DocD

 

[SilverFox]

Hello DocD,

Thanks for clearing that up.

Please ignore any alerts and warnings that I talked about earlier.

Tom