Battery pack charger questions

[sb_pete]

Hey all, so I am thinking of getting a pack charger to take advantage of FM battery holders. Had a few questions:

1. what happened to alin10123? it seems he hasn't posted in quite some time and I know he was selling the packs FM recommends.

2. Who else is still selling the 2-12 cell nimh charger he had? I know Matt K over at battery junction has the other ones for sale, but it is the 2-12 that really caught my attention.

3. Aside from slower charging, are there any disadvantages to this more flexible 2-12 cell charger compared to the other narrower range ones?

4. Totally general question - any harm from frequently "topping up" the cells or pulling them off the charger before fully charged? My understanding is that this is totally ok for Li-Ions (correct me if i'm wrong please), but I have no idea with NiMh cells.

5. That being said, can these chargers be used with a car adapter?

6. What about pack charging li-ions: This one that alin used to sell says it charges between 1-4 cells meaning 3.7-14.8V. Does this mean it can really only handle between one and four cells or can it charge packs of cells in series/parallel within that voltage - say 12 3.7v li-ion cells in a 3p4s pack?

7. What about something like this Hyperion Eos 5i DP which can charge both li-ion and NiMh? Seems like a great charger, but can it run off of a wall outlet or car adaptor or would I have to get something like the next model up at twice the price to do that? Any other suggestions for something like this that can charge both nimh and li-ion packs?

Thanks in advance all
-Pete

 

[jimjones3630]

here is one source

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2488

 

[VidPro]

4. Totally general question - any harm from frequently "topping up" the cells or pulling them off the charger before fully charged? My understanding is that this is totally ok for Li-Ions (correct me if i'm wrong please), but I have no idea with NiMh cells.

ni-mhy can be topped anytime you want if it is a SLOW DUMB charger that stays below the overcharge rate speced for the cell.

they should not be topped, or replaced on a "Fast or Smart" charger endlessly when they are already at a high state. the smart charger terminates based on reaching an overcharge state.

as long as they have fully rested, or have been USED at least SOME, most all smart or dumb chargers wont have any problem at all. the problem comes when putting them back on the charger when they are fully charged .
A "really" smart charger will assess the voltage (or something) on a FULL battery, and not charge it at all, but one should still avoid putting a fully charged battery on a smart or fast charger, as it will have to reach the overcharge state again.

Li-Ion can usually be topped off at anytime, the chargers do not attempt to detect the end of charge based on a voltage drop, instead they stop on a voltage high, which it should never go above.
there are rare possible occurances that a battery that is in a high state, could bypass the cutoff of a really cruddy li-ion charger, but you have to work hard to get it to occur .

on the other hand Li-Ion prefers to be stored at less than a FULL charge, so there is no value in topping it off extensivly. and they dont self discharge very fast either, so generally you dont need/want to piddle with them topping them off all the time, untill you use them.

 

[VidPro]

6. What about pack charging li-ions: This one that alin used to sell says it charges between 1-4 cells meaning 3.7-14.8V. Does this mean it can really only handle between one and four cells or can it charge packs of cells in series/parallel within that voltage - say 12 3.7v li-ion cells in a 3p4s pack?

Li-ion chargers charge based on a voltage high, that thing cant really do anything in series perfectally, because it cant balance out the voltage highs of each cell in a series set. sooo, ummm if you use it as a single cell charger, or Manually balance out the pack , and check and test, and all, potentially it could do the job.

but ya know with flashlights and battery tubes we often have the opertunity to seperate the cells and charge them individually or in parellel, charging UNPROTECTED li-ion cells in series needs multitapping or balancing, or manual attention from knowing user.

Fully seperatly Protected cells will never cause a Bad Problem when charged in series with this stuff, because the voltage highs and lows are protected with the curcuit, but they can still fall out of balance and the least you lose capacity because of the out of balance. at least with protected, you wont get total failure.

simple example:
2x3.6v li-ion cells charged to 8.4v, one is way far out of balance
4.5v + 3.9v = 8.4v
one cell has gone over voltage and will fail or worse cause a problem
the other cell is not yet fully charged.

out of balance occurs over time, is dependant on the cells original quality, matching, and quality of the balancing and protection and all. it usually happens when you forget that it was going to be an issue.

parellel charging is not an issue, series charging is a more difficult thing to do, series parellel charging, is still series.

 

[VidPro]

7. What about something like this Hyperion Eos 5i DP which can charge both li-ion and NiMh? Seems like a great charger, but can it run off of a wall outlet or car adaptor or would I have to get something like the next model up at twice the price to do that? Any other suggestions for something like this that can charge both nimh and li-ion packs

this one you posted, has no specific balacing ability for li-ion, while it might be able to balance out ni-??? things by slow charging at the end to top off the ni-?? things without overcharing, it by itself has no capacity to do that on a series li-ion pack.

a User could potentially use it, and balance by tapping off to balance single cells in the series pack. By using protected cells, or protected packs with single cell protection capacity, it would not be a danger, but on unprotected cells it could be a disaster.

it could still be a power supply (of sorts) for a seperated balancing system, or balancing curcuits, but it and of itself has no capability to fully balance a series li-ion pack , unless the user balanced manually.

if your going to plunk down serious change for a serious charger, for a series pack, find something that fully multitaps the pack, or manually seperate out the cells and balance them.

|--4.2v--|---4.2v---|--4.2v--|---4.2v---|
|--{==]--|--{==]---|--{==]--|---{==]--|

again all these things will work just fine, they will charge a li-ion, but if you want your pack to be peaked out, and full, and balanced, and live a long happy healthy life, the charger will attend to each cell, not blindly assualt a whole pack based on "facts not in evidence".