# Rechargeable batteries (AA, AAA), specifically about chargers

#### mikeymikec

##### Lifer
The charger on the left is one I bought more recently when I decided to make a concerted effort to use rechargeables wherever possible. One selling point was that it could charge irregular numbers of batteries rather than the one on the right insisting on pairs (and can only do a pair of AAAs at a time). My question is about the power capabilities of these two chargers and I guess about NiMH in general. I'm guessing by the fact that neither charger mentions a total battery capacity like my AA/AAA's do (e.g. 1100mA or 2800mA), that the figures these chargers mention are about charging rate rather than a total capacity battery they can charge? Would I also be correct in thinking that the charger on the right is better suited to AAs than the one on the left, ie. it can charge them faster?

#### Paperdoc

##### Golden Member
Yes, the charger on the right can push higher currents into batteries to charge them faster. As far as the number of batteries in a group being charged, I'd guess that the one on the right is wired always to charge two identical batteries in series (or two pairs for a total of four), whereas the one on the left is wired so that all charging slots are in parallel. BUT that may well mean that if you charge TWO AA batteries, they must share the 500 mA charging rate, so each will be charged at a rate of 250 mA, which is only 1/4 the rate of the charger on the right. Big difference in rates, there.

You seem to have misunderstood the specs for QUANTITY of charge. Amperes is the RATE of current flowing into the battery to charge it. The total QUANTITY of charge pushed into the battery is that rate times the time of operation, usually spec'd as mAH - in words, milliAmp - Hours. You'll never find that on a charger, but you will find that on a battery to specify its maximum stored charge quantity. For example, if you use a charger that actually pushes 500 mA charging rate into a nearly-dead battery with a 1100 mAH capacity, it will take 2.2 hours to charge it fully. Actually, it will take longer, because when the battery is nearly full, the charging rate will be reduced to less than 500 mA rate. If the charger you use is only capable of 250 mA, then it will take twice as long.

VirtualLarry

#### mindless1

##### Diamond Member
Whether a faster charger is better depends on its method and accuracy in measuring charge state and terminating the faster (if not only) charging mode, then if any, what the lower aka trickle charge mode does too.

The specs not on the labels are more important, for example whether either is a Delta -V terminating charger and if so, does it then trickle charge indefinitely or time-out after some period. If it does not time out then it will cook the cells slowly. Sometimes the specs can just be "up to" numbers, that don't really indicate what they're doing at any particular point in charging any particular cell capacity. Probably semi-close and possibly comparable between two models from same brand, but how close they stick to the #s depends on how they are regulated and the charge scheme used, whether constant current.

If neither is Delta -V terminating, they might use a timer circuit then overcharge or undercharge the cells depending on the charge state when inserted and their rated (vs real remaining) capacity. I doubt either lack both the Delta -V and a timer shutdown feature, because that would make them terrible, but it's not impossible.

It is gentler on batteries to charge them slower, but for the most reliable Delta -V voltage detection, the charge rate must be above a certain % of their capacity. That can vary by cell design but a rough ballpark is around 25% of the capacity so for a 2000mAh rated cell, 500mAh charge rate, BUT, depending on the charger design, it may put less current through a battery with a higher internal resistance.

If you have more specs that might help, or otherwise the thing to do is measure what they're doing. If they lack an LCD display or provide inadequate info on it, the way to do that is insert a double sided thin piece of copper clad PCB material (in series with the battery contact against the charger contact), with multimeter probe connectors soldered to both sides, so you can measure with a multimeter during the process, what the current is doing, except in order to measure the current the meter will insert a little more resistance to pull the #'s down a bit.

Even if they are using Delta -V, that does not guarantee they work well to fully charge the cells. Many cheap chargers do poorly at this, stopping rapid charge closer to 90% capacity but displaying a "done" green LED or whatever.

It's really easy to state "get a better charger", but in the long run that may be the best route to take if you start using rechargeable batteries a lot, especially if you'd like to run some LED flashlights that take 18650 cells, to get a full featured charger capable of Li-Ion in addition to NiMH.

On a related note, a couple of good forum resources for chargers are https://budgetlightforum.com/forum/batteries/chargers & https://www.candlepowerforums.com/vb/forumdisplay.php?9-Flashlight-Electronics-Batteries-Included

As far as using what you have, the only way to know for sure is measure, log what they're doing, graph it and compare, but Delta -V is the big one, most important feature if you don't want to babysit and check voltage every single time you charge.

Sometimes, more often with a major brand (generics may scrub the IC markings off their counterfeit chips), you can open them and identify the charge controller IC then look up its feature set on the datasheet.

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#### shortylickens

##### No Lifer
OK so I figured out something a while back that I guess I should share here:

A higher powered charger does not ALWAYS charge batteries faster. You would have to plug in both at the same time and conduct tests yourself to see which one is better. And I bet you get bored and walk away before you find out for sure.

mikeymikec

#### mikeymikec

##### Lifer
OK so I figured out something a while back that I guess I should share here:

A higher powered charger does not ALWAYS charge batteries faster. You would have to plug in both at the same time and conduct tests yourself to see which one is better. And I bet you get bored and walk away before you find out for sure.
The one on the left takes ages to charge AA's, so I can easily see that happening I just need a reason to charge 4x AA now!

#### aigomorla

##### Cases and Cooling Mod PC Gaming Mod Elite Member
Super Moderator
A higher powered charger does not ALWAYS charge batteries faster.
Couldnt this also be affected by battery quality and life, as well as how low your discharge was when starting?

But honestly i like to slow charge everything. Which is always why i have plenty of spares.

Also im very happy with that company Bonai... they make acceptable stuff.
Its simular to Tenrgy which is my favorate all time tho.
Oh i won't touch EBL anymore, they went to the gutter, although the EBL lithium rechargeable' s are OK so far from my usage.

Also may want to consider AAA / AA lithiums.
They hold a 1.5v charge longer, although they are more expensive, but works better in stuff which is more voltage sensitive.

#### mindless1

##### Diamond Member
^ From the youtube videos I've seen about those 1.5V rechargeable lithium AA cells (I don't mean only EBL, multiple brands were tested), they seem to droop a lot in voltage with a load, don't actually stay near 1.5V unless the load is very light.

#### aigomorla

##### Cases and Cooling Mod PC Gaming Mod Elite Member
Super Moderator
^ From the youtube videos I've seen about those 1.5V rechargeable lithium AA cells (I don't mean only EBL, multiple brands were tested), they seem to droop a lot in voltage with a load, don't actually stay near 1.5V unless the load is very light.
how heavy of an Amperage did it require?

i can try to test.

#### mindless1

##### Diamond Member
^ The greater the load, the more the droop. Here's a Project Farm video I was thinking of that tested at 250mA, but a general YT search may provide more info.

I've had good results with the Tenergy Centura LSD AA NiMH, but wouldn't touch the EBL or Tenergy regular/non-LSD NiMH AA's... then again I don't buy any non-LSD AA's no matter the brand.

Here's about as much charger info and testing as you're going to find on a single site, besides the two flashlight oriented forums I already mentioned in post #3.