Charging e-bike batteries

[Malish]

So, I may be showing my ignorance, how do I measure % storage: do I just have to rely on the number of LEDs showing on my bike battery (3 greens and a red)? I know my handlebar display is distinctly non-linear. Is there a voltage range equating to 30-100% charged for 36V & 48V systems

 

[dunedin]

The more I think about this, and the OPs requirement of using two eBikes from a boat on the west coast of Scotland - primarily living on anchor rather than on pontoons - then I think the really important practical question is not how big is the battery chargers but ………
………….. how big is your dinghy?

We have a 2.7m dinghy, on davits so ready to go. But taking two bikes ashore, plus two people, is quite tricky in practice. We can stack two bikes on the dinghy seat in their bags, carefully tying in one at at time. But then little or no space for two people let alone the usual bags of food, waterproof etc. And realistically, except in perfect weather (sunny and no wind) the bikes will get salty wet one way or the other in the dinghy. Fine for our cheap bikes, but perhaps less so for expensive eBikes.
I would strongly recommend doing a few trips ashore by dinghy to see how you get on before committing to expensive charging options.

After a few goes, we now tend to use the bikes primarily from pontoon locations - Tayvallich, Ardfern, Mallaig, Lochmaddy, Tarbert (Harris), Stornoway etc. Also sometimes use a pontoon briefly for loading/ unloading - eg Gigha, Eriskay etc. But now would need to be an exceptional cycle trip to be bothered to take two bikes ashore in the dinghy.

As before, solar is near mandatory for other reasons, and works well in long Scottish days for keeping fridge etc going.