I have a small voltmeter that I will be fitting to the 3d printed case I am making for the LiPo…I don’t trust myself to keep checking the voltage from the 818s menu system while in use.
Use a battery alarm as designed for radio control use - it is connected to the charging/balancing connector. You can set the threshold voltage for each cell and the alarm would wake the dead (mine went off in the bedroom at 0300 - her indoors was less than amused 
)
4 Likes
This is a lot more than I paid but that was years back. As Barry suggests, VERY loud.
73,
Rod
2 Likes
That is for 10 Rod, 83p each 
73
Tim
G4YTD
1 Like
Hi,
just in case anybody was curious about that kind of battery (motorbike batt) I will add some info here.
I was intrigued by such batteries and bought one myself about two years ago:
Info was vague and imprecise, as the vendors are not experts of battery chemistry.
The labels in the part are itself confusing; it says Lithium Ion.
One could think it is a LiIon but it is not; after some research I confirmed this part is LiFePO4, 4S model.
In the advert they announced it as of a 7 Ah batt, but after a charge from low voltage level it was fully loaded with about 2500 mAmp, that it fact matched well with its weight.
A real 7 Ah batt should weight more than double.
In addition, the robust and massive package adds redundant weight, because in the end it is designed for the environment of a motorbike.
So, what? It works well, and although it is not (too) expensive, it is better to use a LiPo for the FT818, as others suggested. I used a 3S Lipo 2200 mAH and works perfect for several years up in the mountains.
The battery I bought still works fine and I use it every now and then but when it becomes old I won’t mind saying goodbye without buying another one.
73 de Ignacio
Ps:
Batt dimensions: 15 x 8 x 9,5 cm
Weight about 550 gram
The battery alarm is a great tip, I had not realised that such devices existed. I have just ordered one.
Also good to see the feedback on the motorcycle battery