I have and still use a DX4S radio. I would like to get a new battery for it but the stock battery, SPMB2400LPTX, looks to be discontinued or out of stock. Is there another one that fits? I have looked and GenAce and Protek but don't see anything sized for a DX4S.

Yeah, that original pack’s a pain to find now. I ran into the same issue and ended up using a 2S 7.4V LiPo that fit the tray, just had to make sure it had the right plug or use an adapter. As long as the size is close and the voltage matches, it’ll work fine.

You can also just throw in AA rechargeables with a battery holder as a backup, which bit old school but gets the job done. Just check your dimensions before ordering anything new.

You can always cut off the connector with some wire from the old battery and solder it to the new one.

I know but I didn't want to do that in case I ever wanted to go back to the OEM pack. Plus, it's been bugging me for a long time that the connector was not specified. You can find pigtails from various vendors but the the actuall connector is usually called something generic like Spektrum/JR Tx connector. I figured it had to be an actual connector. After considerable digging, I have identified the connector. It a JST EH (not XH or PH). Here is a link to the connector on the JST site
https://www.jst.com/products/crimp-s.../eh-connector/

The Actual part number for the plug housing is
EHR-2
but them you also need pins and a crimper
The part is listed on Digikey but they don't have stock.
https://www.digikey.com/en/products/...c/EHR-2/527224

All you really need to make a pack is a pigtail. I found these on Amazon

Amazon

Amazon

Radicalrc also sells the pigtail but doesn't tell you the connector is JST EH
https://www.radicalrc.com/item/2-Pol...m-White-100494

I bought both and they both fit.
To make a battery pack, I decided to use Li Ion 14500. The 14500 is the same size as a regular AA. So four will fit. However, the Li Ion battery is about twice the votage of an standard AA so I wired them in 2P2S: two pairs of batteries in parallel with the pairs in series. This gives a 2S pack, 8.2V fully charged. Various places sell 14500 batteries but a lot of them seemed low in capacity. Most are around 800mAh. A pair in parallel would have a capacity of 1600mAh. That is probably fine but the OEM pack has a capacity of 2400mAh. So I looked around more. There was one on Amazon listed as 2500mAh

Amazon

Amazon

but the reviews all said the capacity was a gross exaggeration. In the end, I bought these that are listed as 1500mAh,
https://www.18650batterystore.com/pr...mah-3a-battery
so a 2S pack built as 2S2P would have a capacity of 3000mAh. Not sure how true that is without testing them which I will probably do just to know one way or the other. Here is a photo of the final pack connected to the DX4S. I also added a 2S balance plug.


battery pack with 14500 Li Ion batteries in 2S2P, JST EH power connector and standard 2S balance plug

Are those the Vapcell 1000mAh?

I bought these 1000mAh cells which are capable of a continuous discharge current of 10A and use them as a 2S receiver pack. And they are 1000mAh!

sorry, I meant to post the link for the batteries I bought
https://www.18650batterystore.com/pr...mah-3a-battery
They are marked at 1500. I am doing a run-down test on them now.

I did a discharge test at 1 amp. I charged to 4.2 volts per cell and set the discharge cutoff to 3V per cell. In the 2S 2P configuration, with a stated capacity of 1500aMh per battery, the total capacity should be 3000mAh. I got 2945mAh. At a lower current or going down to 2.9V/cell, it probably would have gone a bit over 3000. So I would say those batteries are fairly specified.