KastarBattery Replacement for Panasonic N4HKGMA00001 Cordless Phone Battery and Panasonic P-P511, HHR-P511, Type 24 Rechargeable Battery

I have two Panasonic cordless phones that are probably 12 years old by now. As I recall, the original packaging said the phone was good for 5 days between charges. After a few years, the batteries display "memory" problems, and die after 2 or 3 days, or an hour or so of talking. This is my third or fourth replacement battery. As I recall, the last one, from Walmart, cost about $18 and lasted perhaps 3 years. It also was too large for the space in the phone. I had to use a screwdriver to force it out when replacing it with this one.This one seems sized like the original equipment, and just fits in snugly. After a quick test, I conclude that it will live for at least 3 days and seems fully functional. I know of no way to test the tendency of a battery to develop "memory" problems short of using it for a few years, but at theis price, I can afford to replace it more often and still be ahead.

My phone works now. I have a Panasonic KX-TG2770 phone system. I was expecting Ni-CD batteries, and got NiMH batteries. Not sure how that happened. I was under the impression that NiMH batteries were better than Ni-CD, and had considered NiMH when buying, but decided to go with Ni-CD I was replacing. From the little bit of research I did you have to be careful that the charger works with NiMH batteries. I wasn't positive my charger would be compatible, but I had seen other battery ads that indicated it would be, so I decided to try them rather than return them. The price was better for these than the NiMH batteries I looked at, and I'm happy with the preformance. No fires yet.

Ordered 4. All are the synergy 900 mAh version. Now, the 900 mAh is about the original capacity, the Energizer ER-P511 was 850 mAh. I just wanted to try an 1800 mAh for the longer talk time (if any). Gotta drop the rating for the picture and the description, otherwise it would be a 5 star. (interestingly enough, at the time of this review, the Synergy product received is $1 more per battery from the same seller, so there's that).Good deal on a replacement if you want the original capacity, the price is right. These are nice NiMH replacements. Especially with free Prime shipping. Decent wrapping around the cells, looks to be well made (as well as the original batteries) They work fine. Same size and shape as the original. Shipping was very fast.Have not had them long enough to know how long the cells will last, but that depends on a lot of factors.

I like that it fits and it works. As to life & longevity (same thing), it is much too early to tell. Catch me in 5 or 10 years and I'll let you know. The previous battery (a different manufacturer) lasted at least that long.

I purchased three of these for my Panasonic cordless phones. I installed two in phones immediately upon receipt, because the old batteries wouldn't hold a charge. They worked perfectly. The price I paid for three batteries was the same price I paid for one battery at a local retail store.Battery Update: These batteries have a serious flaw. They lack the ability to stop charging when fully charged. If you leave the phone on the charger, like I used to with the Panasonic batteries. they apparently overcharge, and the battery fails. You are supposed to remove the phone from the charger, once the battery is fully charged. I found that I could purchase a complete new cordless Panasonic system for the same price as I would pay for three new replacement batteries for the old phones.

Update: shortly after purchasing this battery, I received a email from the seller. I replied with my issue. They sent me another battery. It also arrived quickly. This one took 10 hrs to charge 50%. Upon checking it the next day, it was 100% charged. This seems to be an excessive amount of time to charge a battery like this. I do not know yet how long it will last. If I was doing it again, I would buy a different battery. One thing I noticed now was that this is a Nicad battery and not a nickel-metal hydride. I will read the ads closer next time-------------------------The original review:The battery arrived quickly but it was defective and would not charge. Now I need to return it and order one from someone else. I will not try another one of these but will switch to a different brand.

(UPDATED)The battery is around 10 months old now and only holds a charge for 15 to 20 minutes. I can't figure out how to file on the 3-year warranty either, and it really isn't worth the hassle for less than $10.I purchased a replacement battery several years ago from a national electronics retailer. It cost about 5 times the price of this one. I put it in my phone and the phone responded in the same manner as the original battery had, so I assumed it was the phone. However, this one was such an affordable price that I decided to give it a try. I put it in, let it charge, and it is working perfectly! I use this phone 5-7 hours a day for my work and it holds a charge perfectly and hardly has any drain after a full day's use. Would highly recommend. Great product. Great price. Better than what I bought in the store for a much more expensive price!

Great battery, for still the best wireless phone ever made. I put these in a couple handsets I had stored away as they kept cutting out. But it was not the handset, it was those cheap batteries. Works fine with this battery. All-IN