EEVBlog #35 - Battery Chargers

[Mike04082015]

This one ended rather abruptly with the comment that there was no way to get 1,000 recharges out of the batteries using this.  I think you were relating it to the 4C charging rate.  Am I to assume that a high rate of charge damages NiCad and NMH batteries?  Sounds about right.

Which leads me to ask: How does one find a charger that will use a slower charge.  I'm not sure I've ever seen that as a published figure in these products.  Certainly no manufacturer will advertize: "This charger takes twice forever to recharge your batteries!"  Yet that is probably exactly what is desired, in most cases.

Any thoughts?

[retiredcaps]

Which leads me to ask: How does one find a charger that will use a slower charge.

Most of the higher end models will have an user programmable charge rate from 200mA to 2A.  Some examples.

http://www.mahaenergy.com/mh-c9000/

http://www.lacrossetechnology.com/900/

edit: I have the Sanyo NC-MQN06U.  It defaults to 300mA for 2/4 AA and 150mA for 2/4 AAA.

http://www.candlepowerforums.com/vb/showthread.php?218747-An-informal-look-at-the-Sanyo-NC-MQN06U-%96-charging-in-pairs

[GeezerWhiz]

I like the Turnigy Accucell 6 at $23 from HobbyLobby(dot com)  Dave has done a teardown of this charger (EEVblog #397).  It takes 10 to 17 VDC in (as in car) and outputs up to 6 amps.  It charges lead acid, NiCad, Nimh, and three flavors of Lithium batts.  Of course, any chg. current you want, any terminate voltage you want (including "storage" ones), and batt. cycling.  It charges up to 6 cells in series, with charge balance for each cell. You can even calibrate its voltage sensing to your tastes.  'Will even sense batt. temperature for safety terminate, and you can set a time terminate too.  Be forewarned that the user interface documentation is super nerdy. 

[HKJ]

Which leads me to ask: How does one find a charger that will use a slower charge.  I'm not sure I've ever seen that as a published figure in these products.  Certainly no manufacturer will advertize: "This charger takes twice forever to recharge your batteries!"  Yet that is probably exactly what is desired, in most cases.

Look at the specified charge time, you can usual find that somewhere.
But there are other problems:
Chargers that terminates on time, not when battery is full.
Chargers that has a high trickle charge.
Chargers that get very hot.
Chargers that charges cells in series, not individual.
Chargers with huge peak currents.


I have reviewed some chargers here: http://www.lygte-info.dk/info/indexBatteriesAndChargers%20UK.html
It is mostly LiIon chargers, but there are some NiMH and I will be adding more.
 

[DanielS]

Chargers that charges cells in series, not individual.

Most chargers do series since it is simpler, more efficient and as long as the cells are reasonably well matched, a simple shunt should be enough to bleed off excess charge when cell voltages do not match. In battery packs, you often do not have access to individual cells and have to rely on the integrated charge balancing circuitry, if any.

[HKJ]

Chargers that charges cells in series, not individual.

Most chargers do series since it is simpler, more efficient and as long as the cells are reasonably well matched, a simple shunt should be enough to bleed off excess charge when cell voltages do not match. In battery packs, you often do not have access to individual cells and have to rely on the integrated charge balancing circuitry, if any.

Only the bad chargers and battery pack chargers.
With battery pack you do expect the batteries to be in balance and it is usual not a big deal.
With loose cells it is a bad idea and with NiMH you cannot use a shut to balance the cells. Only way to balance cells is to give them a serious overcharge, this might be fine for old NiCd cells, but for modern NiMH LSD cells it is a bad idea.