What is a good charger for titanium 1800 nimh batteries

[mag623]

I have heard the maha mh-c9000 is a good charger but I have 12AA batteries. I have been thinking about this one http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=3039 but it has a charging capacity of only 1000mAh what exactly does that mean?. Any suggestions for a good charger that is relatively cheap and can charge 12AAs quickly?

 

[monkeyboy]

Yes that one will do the job.

Battery capacity is measured in mAh (milliamp hours).

Charging current is measured in mA (milliamps). That is the rate at which it is charged.

You can use these figures to make a rough estimate of the charging time required.

 

[mag623]

Could you please explain to me what this means, "Built in IC to cut off power automatically when battery is fully charge by minus delta V (-16 mV)"

 

[drmaxx]

You don't provide a lot of info about the battery use. Do you have a battery pack? 12 single batteries that need to be recharged for the next use?

The suggested battery charger chages entire battery packs, meaning the batteries need to be in a rack that can be connected to the outlet of the charger.

You might want to have a look at multibay chargers e.g. at batteryjunction.com. Keyword would be single channel charger.

 

[mdocod]

Hello drmaxx,

When cells are wired in series, capacity of the pack remains the same as if it were a single cell, only voltage adds up. When cells are wired parallel, capacity adds up, but voltage remains the same. The 1000mA charging rate would charge a 12x1800mAH series wired NIMH pack in approximately 2 hours, as the pack would still be 1800mAH capacity as a whole.

-Eric

 

[Mr Happy]

Oh, and the "Built in IC to cut off power automatically when battery is fully charge by minus delta V (-16 mV)". Just forget about that - it is most probably not relevant for your application. The chance that the end of charge can be detected by dV is with unbalanced batteries and at this low charge rate tiny.

Further to what mdocod said, the use of minus delta V is most certainly relevant. It is the industry standard method of detecting the end of charge condition in NiMH battery chargers, and all good battery chargers will include such a test.

The recommended charging current to obtain a good end of charge detection is 0.5 to 1.0 times the battery capacity. So if a battery has a 1800 mAh capacity, a charging current between 900 mA and 1800 mA would be ideal, though lower currents can be used.

It is not recommended to do this for average uses, but if you placed twelve 1800 mAh cells in a series pack and charged the pack as a single battery, then the pack capacity would be 1800 mAh and a 1000 mA charging current would be within the ideal range. The pack would take about 2 hours to charge.

As to the question of the original poster, many people here have far more than 12 batteries in their stock, but this does not always mean you need to charge 12 batteries at once. More likely they can be charged in sets of 4 or 8 and rotated through the charger.

 

[drmaxx]

Hello drmaxx,

When cells are wired in series, capacity of the pack remains the same as if it were a single cell, only voltage adds up. When cells are wired parallel, capacity adds up, but voltage remains the same. The 1000mA charging rate would charge a 12x1800mAH series wired NIMH pack in approximately 2 hours, as the pack would still be 1800mAH capacity as a whole.

-Eric

The recommended charging current to obtain a good end of charge detection is 0.5 to 1.0 times the battery capacity. So if a battery has a 1800 mAh capacity, a charging current between 900 mA and 1800 mA would be ideal, though lower currents can be used.

Ooops, it seems that my brain still was missing some caffein this morning. Thanks for spotting this brain f.... of mine.
Both statements were based on a <100 mA current per battery, which is simply dumb. Sorry for that.

 

[mag623]

What's a good way to test each individual battery so I don't get a dud in the pack. I want to do this so the battery with the lesser capacity doesn't bring the others down. Why is it not good to regularly charge these batteries in a pack?

 

[Mr Happy]

What's a good way to test each individual battery so I don't get a dud in the pack. I want to do this so the battery with the lesser capacity doesn't bring the others down. Why is it not good to regularly charge these batteries in a pack?

There are two aspects to successful use of a battery pack. The first is to match the batteries as closely as possible for capacity before assembling them into the pack. The second is to periodically balance the pack to even out any differences an charge state and performance that can build up over time.

For matching batteries there have been some good threads on this forum concerning that topic. You may find them with a search or maybe others have bookmarked them and will follow up here with some links. However, to obtain 12 matched cells you may need to purchase more than 12 and then analyze them and sort them with a tool like the Maha C9000 charger.

To balance packs, you can either take the pack apart and run a break-in cycle on the individual cells with the C9000, or if the pack cannot be disassembled you can run a conditioning process on the whole pack using a suitable pack charger.

The reason it is not good to regularly charge batteries in a pack without periodically balancing it is that the weakest cell well tend to get stressed more during the charge and as a result will get further out of balance. Over time the imbalance will tend to lead to the weaker cells getting damaged.