I agree if your serious about preserving your LIPO get a balance charger they are not expensive and will allow you to charge/discharge to a storage voltage

https://www.ebay.co.uk/itm/New-iMAX-B6-AC-Lipo-NiMH-Polymer-RC-Battery-Balance-Charger-Discharger-UK-Plug/172401169819?epid=503854605&hash=item2823e9159b:g:ERIAAOSwh9hZ7xsO

Hi Les
Thank you.
There are three LEDS which change from red to green when fully charged. I can see no mention of setting a half charge. Haverlock was right in thinking each cell was charged by the balance lead so you will be protected from overcharging.
The solution is to buy a battery checker theirs is DYN4071 and I have one in my collection.
Using the checker involves plugging the battery via the balance lead into the balancer and each cell voltage is displayed sequentially. So you charge for half your normal length of time and check the voltage of each cell is about 3.7 to 3.8v.
Bit clunky but would work.
A better solution would be to invest in a balancer charger which will automatically charge to full voltage or the storage charge.
There are several available some with mains power supplies and others needing a DC power source.
Have a look at
https://www.componentshop.co.uk/catalogsearch/result/?q=balance+charger
I have a Giant Power G6AC but they all work just as well.
Please ask if you need more info

Hi Dave. Here is the section in the manual regarding the battery.

I could guess as well as you, Doug, but the answer lies in the manual.
Sorry Doug, I meant Haverlock. Apologies
Dave

is it possible that the charger is working via the balance lead and charging each cell independently?

HI Les
My mistake in asking you to upload the manual. I should have said upload pics. Can you photo and up load the relevant section, please?

The battery charging section is within the main user manual for this little Proboat Recoil 17.

Hi Les
Can you upload the instruction manual?

The storage charge is normally set by your charger and the balance lead on the battery is used by the charger to set each cell to the storage voltage.

If there is only one LED then I suspect this is after all cells have reached the set charge value.

Hopefully the charger manual will help