Inverters and charging your eMTB

Ocsid

Esteemed Pedelecer
Aug 2, 2017
449
269
81
Hampshire
I agree the vehicle's battery is not going to be done any favours with the charge currents the alternators can punch out, but the alternators are sized for the high current draws of the kit the vehicle has, ie seat heating, lighting etc.
Even a 400 Watt output inverter is going to take over 33 Amp before its losses are considered. This load ought to be available from the reserves the alternator gives above the demands of the vehicle's battery.
The wiring alternator to the inverter will need to be very carefully considered, even for such a modest one as 400Watts.

As said earlier, it was a onetime dream, but the challenges simply made chasing it too much for me.
I have a bike battery that actually has achieved over 100 miles, on the terrain I take on these days, and my age now leads to about 20 mile rides.
A battery of that capability gives 4 days riding before becoming critical. The consequences are recharging during a camping break are not what I originally assumed I would face. Therefore, that and grabbing a opportunity to boost a bit over lunch, serves my needs without developing an on board recharge facility.

If I knew more about charging my bike battery I would explore making a bespoke DC to DC converter to clamp on the vehicle's alternator. Back in 2015 when doing my bike purchase investigations, Bosch did a DC input charger, but at an eye watering price [£140 ?? if I recall]. I doubt if I would have paid it, but in the end did not go Bosch anyway.

It would be interesting to know of others here who have cracked in "car" recharging of bike batteries, in a worth the effort way?
 

cyclebuddy

Esteemed Pedelecer
Nov 2, 2016
1,639
770
Beds & Norfolk
The wiring alternator to the inverter will need to be very carefully considered, even for such a modest one as 400Watts.
You can run many small inverters directly off the cigarette lighter/accessory socket up to 10A/120 watts - sufficient for most ebike chargers. My 400-watt Pure Sine came with two sets of leads to either plug into the accessory socket (120w) or directly to the vehicle battery (400w). It works perfectly well either way for bike battery charging.
It would be interesting to know of others here who have cracked in "car" recharging of bike batteries, in a worth the effort way?
Companies like Powatechnic make direct DC-DC ebike chargers (about £40), which will be more efficient than using an inverter, but it doesn't escape the fact you're still taking a lot of juice out of your starter/leisure battery which is hard to replenish off-grid.

Car inverter use at 5.24, Van install at 11.53.
 

seagaf

Just Joined
Jun 17, 2020
2
0
You can run many small inverters directly off the cigarette lighter/accessory socket up to 10A/120 watts - sufficient for most ebike chargers. My 400-watt Pure Sine came with two sets of leads to either plug into the accessory socket (120w) or directly to the vehicle battery (400w). It works perfectly well either way for bike battery charging.
Companies like Powatechnic make direct DC-DC ebike chargers (about £40), which will be more efficient than using an inverter, but it doesn't escape the fact you're still taking a lot of juice out of your starter/leisure battery which is hard to replenish off-grid.

Car inverter use at 5.24, Van install at 11.53.
I have a Fazua drive unit and this looks to be a credible option. Can be used from the alternator while driving in most cars or from the leisure batteries/ solar panel in a camper.

12V Car Charger BMZ Li-Ion 42V 2A plug Rosenberger

Stepping DC up from 12v to 42v is a lot more efficient than inverting from 12v DC to 240v AC and then transforming back to 42v DC.

I have a 225ah leisure battery, so assuming the charger draws 10a for 5 hours to do a full charge that's 50ah which seems reasonable. I think my 175w solar panels or alternator split charge setup could replenish that and still keep the beer fridge cold. Or worse case scenario 80% charge in 2 hours for just 20ah.
 

cyclebuddy

Esteemed Pedelecer
Nov 2, 2016
1,639
770
Beds & Norfolk
I have a 225ah leisure battery, so assuming the charger draws 10a for 5 hours to do a full charge that's 50ah which seems reasonable. I think my 175w solar panels or alternator split charge setup could replenish that and still keep the beer fridge cold.
Maybe so. But the few others I have met who regularly go "off grid" go with (at least) two e-bike batteries. Your Fazua battery is only 250Wh - most here are using 400, 500, 625, or even 700Wh batteries.