PanasonicCordless Telephone Battery (HHR-P104A)

We use this on our land line phone.

A battery is a device that converts chemical energy directly to electrical energy. It consists of a number of voltaic cells; each voltaic cell consists of two half-cells connected in series by a conductive electrolyte containing anions and cations. One half-cell includes electrolyte and the electrode to which anions (negatively charged ions) migrate, i.e., the anode or negative electrode; the other half-cell includes electrolyte and the electrode to which cations (positively charged ions) migrate, i.e., the cathode or positive electrode. In the redox reaction that powers the battery, cations are reduced (electrons are added) at the cathode, while anions are oxidized (electrons are removed) at the anode. The electrodes do not touch each other but are electrically connected by the electrolyte. Some cells use two half-cells with different electrolytes. A separator between half-cells allows ions to flow, but prevents mixing of the electrolytes.Each half-cell has an electromotive force (or emf), determined by its ability to drive electric current from the interior to the exterior of the cell. The net emf of the cell is the difference between the emfs of its half-cells, as first recognized by Volta. Therefore, if the electrodes have emfs and , then the net emf is ; in other words, the net emf is the difference between the reduction potentials of the half-reactions.The electrical driving force or across the terminals of a cell is known as the terminal voltage (difference) and is measured in volts. The terminal voltage of a cell that is neither charging nor discharging is called the open-circuit voltage and equals the emf of the cell. Because of internal resistance, the terminal voltage of a cell that is discharging is smaller in magnitude than the open-circuit voltage and the terminal voltage of a cell that is charging exceeds the open-circuit voltage. An ideal cell has negligible internal resistance, so it would maintain a constant terminal voltage of until exhausted, then dropping to zero. If such a cell maintained 1.5 volts and stored a charge of one coulomb then on complete discharge it would perform 1.5 joule of work. In actual cells, the internal resistance increases under discharge, and the open circuit voltage also decreases under discharge. If the voltage and resistance are plotted against time, the resulting graphs typically are a curve; the shape of the curve varies according to the chemistry and internal arrangement employed.As stated above, the voltage developed across a cell's terminals depends on the energy release of the chemical reactions of its electrodes and electrolyte. Alkaline and zinc-carbon cells have different chemistries but approximately the same emf of 1.5 volts; likewise NiCd and NiMH cells have different chemistries, but approximately the same emf of 1.2 volts. On the other hand the high electrochemical potential changes in the reactions of lithium compounds give lithium cells emfs of 3 volts or more.And it fits perfectly into my old cordless phone.

I have a Panasonic telephone set of 3. Two of the satellites were misplaced when my wife, new to the country decided to completely rearrange my house. When I finally found them, they wouldn't hold a charge for long, and did not recognize the base. When deciding to fix problem, I went to an Office Depot where they sold similar phones, and they had batteries for over $20. and the clerk suggested that I charge the phones in the base, and that would probably reconnect them. I went home and took the battery out of one of the phones, and then to Amazon where I found the batteries for less than half of what the Office supply store was charging. I matched up the numbers, found the picture on the package to be an exact match for the removed battery, and ordered two batteries. When they promptly arrived I was a little alarmed to see that the batteries did not match the colors; instead of the olive green and black on the website, they were orange and black,but the numbers were correct. When I started charging the batteries in the phones with some of the time charging in the base unit to pair them, they were very warm to the touch.I have a VOIP Ooma Teleo set-up at home, and once the charging of the satellite phones was complete, there was a couple of missteps, not sounding quite right, but then both working properly. The phone that was left in the base unit still has the original battery, but it has never been completely discharged and left alone depleted. The phones with the new batteries, despite the color difference from what wasadvertised, are now cool to the touch, and working. So I have high hopes that this resolves the problem. I have had the Panasonic phones for about seven years now, they are 5.8 GHZ. I have the Ooma VOIP for a little over two years, also acquired through Amazon, and I like it very much, especially the $3.75/mo. phone bill.Update July 9, 2015.Still have the original battery in the phone by the base unit. And the phones with the batteries bought through Amazon are still working very well. So I think that as long as you don't leave the phones out of the charging units for very long (as in lost), they work even if they don't match OEM colors. No problems. Revising rating to 5 stars.

For the difference in price, you may want to get the oem battery. This one fits the GIGARANGE series of phones. Here's what I've found- shelf life is about 3 yrs. OEM BAT seem to last longer between charges. Here's one weird thing: when using factory nimh bat. you get a warning beep tone in your ear before phone shuts off. When the oem batteries are new, you get maybe a 3 min. warning. With old stock oem or with the aftermarket batteries, you usually get no warning. The aftermarket bat. can be quite irritating when they die suddenly and you drop a call in progress.I have also run into state oem bat. If you get one, buy from Amazon direct, not a marketplace vendor. Amazon will do the right thing and exchange a poor battery. When you get battery, charge it immediately for 24 hrs. BEFORE USING.Then use the phone heavily and run the battery down all the way before recharge. Factory batteries are nimh, not nicads, and they should not develop a memory effect problem.