23-06-2020, 08:19 AM
(This post was last modified: 23-06-2020, 08:23 AM by Mike Watterson.)
They are fine for parallel 1.4V filaments. Better than Zinc, Alkaline or NiCd. Eastern Europe and USSR actually did do B7G D9* valves with a slightly lower filament rating for Ni and Ag based rechargeable systems. But actually the NiMH have a slightly higher average voltage than NiCd, though about the same end point. The end point of 1.0 to 1.1 rather than 0.9V better suits the DK91, DK40, 1L6, DK92, DK96 and locktal/octal mixer/osc as they stop oscillating at 1V when new and 1.1+ as they wear.
Also they keep well left flat, which is the opposite to Lead Acid and Lithium.
Many of the sets in the 1940s using Telefunken low profile Y8 battery valves used NiCd. (DEAC) as did many continental mains/battery sets using those and D4 series and D9 series after the war. I've made replica DEAC packs with a C or D NiMH soldered in. They also act as the regulator for LT when on mains.
Why bother with the expense and awkwardness though unless you are using the set every day? Often they will go flat in a month. The highest capacity ones often faster. A few kinds will hold charge for 6 months. But decent Alkaline cells have a 5 year or more shelf life and about x2 to x3 the running time of a good NiMH.
They are not so good in the long term for 7.5V to 12V LT systems, just on cell life as one can be flat first, radio will still go and cell will be reverse charged. Fine for that if carefully checked, or you use one cell less so that radio stops before any one cell is low. So a LT pack with 9V in it (radios with an RF preamp) might use 6 x C cells, or D Cells rather than the 7 to give closer to a "Fresh" Zinc.
Don't be tempted to use them for HT as obviously the risk of a destroyed cell is x6 higher than an NiMH PP3 pack. The NiMH PP3 and other series NiMH in gear without battery condition monitoring have a much shorter life due to one cell being flat before the others and getting effectively reverse charged.
I use 2032 lithium coins, carbon layer PP3, Alkaline AAA or Alkaline AA in HT packs. The AA work out cheapest. The Alkaline PP3 are not worth the extra cost. I avoid Duracell (poor base seals and overpriced), Energiser (overpriced) and Panasonic (overpriced unless on offer). Varta, Aldi, Lidl are fine as are most random or badge brands. Totally avoid Zinc carbon and Zinc Chloride round cells. They should be banned.
I've not made the PP3 styled (longer) 45V and 67V packs yet for the pocket sized valve radios. Likely I'd use Alkaline button or Lithium coins.
I use paralleled stacks of 2032 (bought at 12c each from China) using 1N4148 diodes) with a wired fuse on each parallel stack to completely fill a 67V B101. I use PP3s for B126. The next size up packs (HT only and combo) I usually use AAA, I do use PP3 in the B114.
I've investigated why Alkaline cells leak. There are two reasons:
1) Poor construction of the bottom seal (Duracell & Polaroid) . Unlike Zinc Carbon and Chloride the case is positive and the -V is a spike attached to the base plate.
2) Compartment or holder that's too tight, or spring is too strong. It breaks the bottom seal with time.
Another issue in older sets, especially valve sets is metal battery holders, typically for D cells (there may be two in parallel). The Alkaline cells often only have a thin film. I add a printed sleeve (sometimes in thin card) to help protect the cell from getting shorted. Some holders also can short to the metal top surrounding the + terminal, so a card or plastic washer is needed.
I've made sockets and plugs from cut up coffee tin. The last one I did was for a PP10 for a transistor Sky Prince. I found that a cheap nail emery board made into two layers duplicates the paxolin and holds the pins. The PP10 fills nicely with D cells in a simple wooden holder.
Also they keep well left flat, which is the opposite to Lead Acid and Lithium.
Many of the sets in the 1940s using Telefunken low profile Y8 battery valves used NiCd. (DEAC) as did many continental mains/battery sets using those and D4 series and D9 series after the war. I've made replica DEAC packs with a C or D NiMH soldered in. They also act as the regulator for LT when on mains.
Why bother with the expense and awkwardness though unless you are using the set every day? Often they will go flat in a month. The highest capacity ones often faster. A few kinds will hold charge for 6 months. But decent Alkaline cells have a 5 year or more shelf life and about x2 to x3 the running time of a good NiMH.
They are not so good in the long term for 7.5V to 12V LT systems, just on cell life as one can be flat first, radio will still go and cell will be reverse charged. Fine for that if carefully checked, or you use one cell less so that radio stops before any one cell is low. So a LT pack with 9V in it (radios with an RF preamp) might use 6 x C cells, or D Cells rather than the 7 to give closer to a "Fresh" Zinc.
Don't be tempted to use them for HT as obviously the risk of a destroyed cell is x6 higher than an NiMH PP3 pack. The NiMH PP3 and other series NiMH in gear without battery condition monitoring have a much shorter life due to one cell being flat before the others and getting effectively reverse charged.
I use 2032 lithium coins, carbon layer PP3, Alkaline AAA or Alkaline AA in HT packs. The AA work out cheapest. The Alkaline PP3 are not worth the extra cost. I avoid Duracell (poor base seals and overpriced), Energiser (overpriced) and Panasonic (overpriced unless on offer). Varta, Aldi, Lidl are fine as are most random or badge brands. Totally avoid Zinc carbon and Zinc Chloride round cells. They should be banned.
I've not made the PP3 styled (longer) 45V and 67V packs yet for the pocket sized valve radios. Likely I'd use Alkaline button or Lithium coins.
I use paralleled stacks of 2032 (bought at 12c each from China) using 1N4148 diodes) with a wired fuse on each parallel stack to completely fill a 67V B101. I use PP3s for B126. The next size up packs (HT only and combo) I usually use AAA, I do use PP3 in the B114.
I've investigated why Alkaline cells leak. There are two reasons:
1) Poor construction of the bottom seal (Duracell & Polaroid) . Unlike Zinc Carbon and Chloride the case is positive and the -V is a spike attached to the base plate.
2) Compartment or holder that's too tight, or spring is too strong. It breaks the bottom seal with time.
Another issue in older sets, especially valve sets is metal battery holders, typically for D cells (there may be two in parallel). The Alkaline cells often only have a thin film. I add a printed sleeve (sometimes in thin card) to help protect the cell from getting shorted. Some holders also can short to the metal top surrounding the + terminal, so a card or plastic washer is needed.
I've made sockets and plugs from cut up coffee tin. The last one I did was for a PP10 for a transistor Sky Prince. I found that a cheap nail emery board made into two layers duplicates the paxolin and holds the pins. The PP10 fills nicely with D cells in a simple wooden holder.
