personally I prefer my bike without the weight of motors and batteries
I can enjoy both variations.
Off Road where you are not limited to the 200w - 250w AU road rule. The weight of the motor + battery is lost in the roundings in the power to weight ratio. 3.5kg motor, 2kg battery total 5.5kg - 2500w
The (rider + bike 75kg+10kg- 85kg- 250w) (rider+bike+ebike gear 95.5kg - 2500w+ 250w = 2750w) 6% more weight over 10 times the power.
This assumes you have have placed that 5.5kg on the bike in a way that doesn't upset the handling of the bike to much.
Don't get me wrong .I got myself a reasonable mountain bike not long ago and I have a lot of fun on that without a motor and plan to keep it that way.
The way I charge my ebikes from PV when I am at the house or away from the house is by using a RC model charger. They run are inexpensive ($30 - $50 ) and run on 12v DC input. They have settings for all kinds of battery chemistry from PB to nicad, lifpo4, and various lithium chemistries over a wide voltage range (use two chargers for higher voltage packs) They also balance the cells and offer all the monitoring and protection during charge you could ask for.The one charge can more or less charge everything.
What I do to charge in the bush is use a small 20AH lipo4 12v battery as a buffer battery (just takes the load when clouds pass over) My solar panel out in the sun charging the buffer battery and the RC model chargers run from the 12v battery.
If I have my ute then I just use the anderson connection at the back for a 12v supply and there is a 200AH agm in the tray. PV on the canopy of the ute charges the 200 Ah agm and continues to charge it while I am out riding. With my Imiev I just charge from the 12v lighter socket and the DC/DC converter keeps the 12v power flowing to the socket from the 16kwh traction pack.
At home I use a 40A 240v- 12vDC power supply that runs off the mains in my garage. Mains power is provided from off grid solar system.
Offgrid 2008, Selectronic PS1 6kw/48v inverter, x 2 Midnite solar classic 150 MPPT, 3960w NE PV 24 x 165w BP panels, 4200w NW PV 21 x 200w DAQO PV, 16x400ah lithium.