3 D cells in series but one drains before the others

[Apothecary]

I think your "new" D batteries have an older little AA cell inside. Tenergy (sold at Amazon) D size Ni-MH cells are 10000mAh. Their head office is in California. I never tried them.

I have 4 Tenergy 10,000 mAh batteries.

I just cycled them yesterday to see their health. One interesting thing I noticed is that on the Discharge Cycle, they dropped voltage pretty quickly. What I mean is that very near the beginning of the Discharge cycle from full charge, they dropped to around 1.15v after only about 15 minutes....and stayed pretty close to that for the remaining hours that it took to go to 0.90v. At around 1.10v it began to accelerate the decline in voltage. So I would estimate that 95% of the discharge cycle was at or below 1.15v.

This is a bit different than most of my NiMh cells. Most of my other NiMh cells are more linear and progress through the voltage drop at a fairly steady pace in keeping with the current drain. I'll have to put them on my MC3000 and log all the discharge data to a CSV file and plot it but I think it will look like I describe.

 

[Nigel Goodwin]

A VERY long time ago, I plotted discharge curves for a number of different batteries, and they are still on-line.



The rapid initial drop is normal, with artapid drop at the end, for both Alkaline and NiCd - NiMh didn't exist back then

 

[Apothecary]

Thanks!

 

[Apothecary]

One note about HarborFreight Thunderbolt batteries.....in the past I've always found them to be pretty good value. But that seems to have changed.

The first pack of D cells I bought recently had two batteries that were a bit low in capacity compared to others I have, so I returned them in exchange for a different pack.
The new pack has two batteries that are WILDLY different capacities.

One of them tested at 3750mAh and the other at 2440mAh. They seem to have little if any quality control on these batteries.
As such....I can no longer recommend them. I'll be buying Tenergy I guess going forward.

 

[Nigel Goodwin]

One note about HarborFreight Thunderbolt batteries.....in the past I've always found them to be pretty good value. But that seems to have changed.

The first pack of D cells I bought recently had two batteries that were a bit low in capacity compared to others I have, so I returned them in exchange for a different pack.
The new pack has two batteries that are WILDLY different capacities.

One of them tested at 3750mAh and the other at 2440mAh. They seem to have little if any quality control on these batteries.
As such....I can no longer recommend them. I'll be buying Tenergy I guess going forward.

Well don't you think 'Thunderbolt' sounds a pretty crappy name for a battery? - usually crappy names means a crappy product.

 

[Apothecary]

Well don't you think 'Thunderbolt' sounds a pretty crappy name for a battery? - usually crappy names means a crappy product.

What was I thinking? Tenergy from now on.

 

[nsaspook]

Well don't you think 'Thunderbolt' sounds a pretty crappy name for a battery? - usually crappy names means a crappy product.

But it's a great name for a car or lube gun..

Thunderbolt Grease-Slapper