How to treat a new Li-Ion battery pack...?

Zerogee

Zerogee

Clencher's Bogleman
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Well, having taken the plunge and ordered an Ansmann 4-cell 14.8 volt 5000mAh Li-Ion pack from CPC/Farnell, it has just arrived by UPS courier, along with a compatible "smart" mains charger. First thing to work out is the best way to connect the two together, since the charger comes with a nice selection of jack and co-axial plugs for various sockets, but the battery pack terminates simply in red and black wires....

Once I've got that bit figured out, what should I do with the battery pack - should I put it straight on charge, or it it likely to have been shipped in a pre-charged state?
I have NO prior experience with Li-Ion/Li-Po batteries at all, so any constructive advice (preferably in simple terms!) would be useful!

:)

Jon.
 
The short (pun intended!) answer is 'very carefully'.

When connecting up the battery leads be very careful not to create a short (i.e. join the two wires together) anything from a spark to a large flash could occur and furthermore the battery could get knackered. The battery is short circuit protected but I still wouldn't depend on that. Make sure one of the battery connection wire is completely shielded while working on the other. Don't cut them both through at the same time.

Probably the battery is about half charged. I wouldn't charge it until it is installed in your engine. Hopefully you will be able to get a charging socket that will connect with one of the plugs that came with the charger.
 
Thanks for the help, Cliff! Yes, I will be VERY careful when attaching a plug to the battery pack - as you say, one lead at a time! The flying leads from the pack each come with a short length of protective heatshrink covering the exposed wire end, so I will only strip that off one lead at a time - I'm going to connect each to a pre-attached lead coming off the plug socket I'm using, so that at no point will I be trying to work with the two bare lead ends in close proximity!

Just one more question at this point, which you or someone else who knows their batteries (Ross?) may be able to answer - the English instructions on the Ansmann charger are reasonably clear, but there is one "big warning" thing that I don't understand - the sheet says :
"Charge only Li-ION or Li-Po batteries with an end of charge voltage of 4.2C per cell. It is forbidden (sic) to charge Li-ION or Li-Po batteries with an end charge voltage of 4.1C per cell. These batteries could be damaged or even explode"

When they say "4.2C", do they mean 4.2 VOLTS, which for a 4-cell pack would match the maximum output of the charger (16.8 volts)? I don't really understand this "C" bit that they keep talking about, except that I'm sure it's not referring to the speed of light in a vacuum..... ;)

Thanks in advance!

Jon.
 
Further to the post above, what exactly do they mean by "end of charge voltage" - and where would you find this stated for a given battery pack....?

Thanks,

Jon.
 
They say "voltage", but write C. That must be a mis-print. What does the original German look like? I bet it says V or Volts there.

During charging the voltage rises in an almost linear fashion. It falls similarly during discharge.

All Li batteries have an end of charge voltage. When each cell during charging reaches this voltage the charger will stop charging it. Any more and ... well, they spell it out.

Similarly, there is also an end of discharge voltage. You must never discharge it below that or the battery will take damage.

There is also a storage level, according to my charger's docs. It even has a storage mode, where the target voltage is somewhere in between the two end of charge voltages and the charger will either charge or discharge the cells to arrive at the storage charge. If the battery is not used for a longer period then it should be at that level.

where would you find this stated for a given battery pack....?
Click to expand...

If you didn't get a printed sheet with the battery stating this then I would look on Ansmann's web site.
 
Going with the above bit about 'very carefully', I would expect that with a battery and a compatible intelligent charger (from a high end technical supplier) then it should be a case of plug in and charge.

The intelligent charger will be able to discern the level of pre-charge (if any) and compensate in the charging rate.

The other bit is to treat it like your lappy, and you will get the longest life out of the battery if you fully discharge every time.

How to achieve that? Well, one way is to wire the head light up to the battery and not through the ECU; that way, you can leave the loco switched on at the end of a running session until it discharges (if you don't need to test anything tomorrow, that is).
 
Zerogee said:
- and where would you find this stated for a given battery pack....?
Click to expand...

It is in the spec sheet for the battery: http://www.farnell.com/datasheets/1865330.pdf

I agree they are talking about voltage. Most Li-Ion cells have a nominal voltage of 3.7 volts, but at maximum charge they can have a voltage of 4.2 volts. 3.7*4 = 14.8, and 4.2*4 = 16.8 which is entirely consistent with your battery pack and charger.

Confusingly there IS a C rating that can be used to either help specify the maximum continuous current that can be drawn from a battery, or the maximum current that can be used to charge it.
 
Rhinochugger said:
... and you will get the longest life out of the battery if you fully discharge every time.
Click to expand...

This is a complex area but I'm not sure that is true anymore that a full discharge is required every time with modern Li-Ion batteries.

Certainly it is wrong to store batteries completely discharged. Their life will be extended if they are charged up to about half way, as Peter has already said (and why batteries as delivered will usually be charged up a little but not to the max).

If batteries are left completely drained then the risk is that they will self discharge too much, past the minimum charge level, and they will not then be able to be charged at all.

Most Li-Po chargers have a 'storage' option for about a half a full balance change. Unfortunately I don't think Jon's charger will have that feature. What I do in such cases is to do a full charge and then discharge to what I think is about half way.
 
Rhinochugger said:
The other bit is to treat it like your lappy, and you will get the longest life out of the battery if you fully discharge every time.

How to achieve that? Well, one way is to wire the head light up to the battery and not through the ECU; that way, you can leave the loco switched on at the end of a running session until it discharges (if you don't need to test anything tomorrow, that is).
Click to expand...

NO NO NO.
This bad advice. Do not discharge Li below 3.0 V/cell. If you do you will almost certainly completely ruin the battery.

This is why all 'loads' must have an undervoltage cuttoff so that when the volts get down to 3.0V/cell, the load is disconnected.
Comparing it to a laptop battery is erroneous - the laptop has a circuit to detect the min voltage and turn it off.
There is a difference between completely flattening a battery (as per the headlight above) and discharging it to a safe low level.
 
Thanks, Cliff and all....

I got the pdf data sheet for the battery pack (from the CPC website) and that makes some stuff a bit clearer. Looks like the compatibility will be fine (as I would have hoped, but you just never know). One thing is that this battery pack has the maximum discharge current is limited to 4 Amps by the protection board in the pack; this would make it unsuitable for very high power applications (it wouldn't be much use to the R/C flight or car fraternities) but I reckon will make it ideal for what I want, which is sensible speeds on a twin-motor loco!
The only awkward thing is making sure the polarity is right for the output from the charger, because it has all those interchangeable plug heads that fit into a round two-pin connector on the lead, and these can be reversed to change the polarity of the output plug - I'm going to have to check this VERY carefully with a multimeter once I've figured out which head to use, then check it again two or three times.... ;)

More on progress tomorrow, if I get time to do much with it (work is VERY busy at the moment....) :)

Jon.
 
Not sure of the charger model that you have Jon but my 'smart' one detects if there is a wrong polarity and gives a message on the screen to say so.
 
Hi Mike, it is supposedly a "smart" charger but doesn't have fancy stuff like a screen! It's this one, same branding as the battery pack and from the same supplier, thus should be fully compatible:
http://cpc.farnell.com/ansmann/9c94131-01/charger-li-ion-14-8v-1-2a/dp/BT06054?in_merch=New Products

The tricky bit is that you can plug any of the connector "tips" on either way round, but there is no actual indication of which way they SHOULD be.... the charger (and battery) may very well be reverse-polarity protected, but I can't see anywhere that this is explicitly stated and I don't want to take any chances..... ;)

Jon.
 
Hmmm, just had a thought.... as it's a "smart" charger, if I simply put a multimeter across the output to check the polarity, will it actually HAVE any output to read? Or will it only output something when it detects a battery pack connected to it?

So many questions, so little time to actually try anything out... ;)

Jon.
 
Hi Jon
I have just checked the spec for the charger that you received.
If it is the one that comes with a whole load of little jacks that have two pins that plug into socket on the wire from the charger, then there should be a 'plus' sign on one side of the little socket from the charger to indicate the positive pin.
 
beavercreek said:
Hi Jon
I have just checked the spec for the charger that you received.
If it is the one that comes with a whole load of little jacks that have two pins that plug into socket on the wire from the charger, then there should be a 'plus' sign on one side of the little socket from the charger to indicate the positive pin.
Click to expand...

Hi Mike, yes, I've checked the tech spec sheet for it too - but it's still unclear.... there is a "+" symbol on one side of the socket (but unhelpfully, midway between both pins, rather than indicating one specific pin), and also on each of the interchangeable tips - but that still doesn't tell me, when the tip is put into the socket, which way round the polarity is on the tip - the case of the "hollow plug" power connectors, is the centre pin "+" and the outer sheath "-", or vice-versa?
Will just have to give it a go with the meter, I guess.....

Jon.

Edit: OK, an update.... according to the meter, when the "+" symbols are aligned on the socket and tip then the inner part of the hollow plug is "+", and the outer sheath is the "-"..... it would have been useful if they'd actually specified this somewhere, or is this an industry standard default which I "should know anyway".....?
 
Yeah, the spec sheet is not that informative about polarity but I was also going on an old charger (not lithium) that I have, that has the 'two pin' arrangement for various sized plug jacks. It has the 'plus' sign on one side of the socket, but conveniently, it is by one of the pins

You should get the result with the multimeter but if not, just give the charger a small load to feed and it should then give a reading.
 
Re centre pin positive:
Mostly, yes.. BUT if in doubt check with a meter.

It appears it is a 'rule' proved by its' exceptions!
 
PhilP said:
Re centre pin positive:
Mostly, yes.. BUT if in doubt check with a meter.

It appears it is a 'rule' proved by its' exceptions!
Click to expand...

Thanks Phil, yes, I'd thought that sort of thing might be the case, otherwise the plug tips would be "mechanically polarised" rather than reversible..... well, with the red meter probe in the centre hole and the black one on the outer sheath I get a positive voltage reading off the charger, reversing the probes gives me a negative voltage.... so I guess that confirms that the centre of the plug is the positive and the outer the negative!
It would all have been a damn sight easier if they'd simply stated that in the leaflet..... ;)

Now an UTTERLY stupid question, but the more I overthink this the more I begin to doubt even the most blindingly obvious things.... the positive output of the charger DOES go to the positive (red wire) of the battery pack, doesn't it? ::)

Jon.
 
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