solar assisted trike to pull miniature gypsy wagon,need advice on powering

[jimi marshall]

Hi all, me and my friend are about to commence building 2 recumbent solar assisted trikes which will pull mini bowtop trailers to portugal to perform at boom festival in portugal. My main questions at the moment are regarding power and storage.
We will be towing a fair amount of weight and will need electric assistance uphills. Does anyone have an opinion as to whether a 250w geared hub motor could handle an uphill load? or would it most likely burn out? I was considering going for a 500w geared hub motor on 1 wheel and have the chain power on the other side. I guess that way i could just run at half power but be assured the motor could take the strain? Definitely wont be moving very fast so should be cool with the cops. Or do people think maybe a mid mount motor would be better? then i could put it in granny mode on the rear derailleur?
Also battery choice is getting a little overwhelming. Need something light so was thinking li-ion but very expensive,are lifePO4 safer than li-ion? Going to recharge via solar as it will be a 1000 mile journey. Have been warned about charging lithium with solar so need to buy a custom MPPT charge controller to get steady voltage to bats (or use inverter charger but will lose efficiency,would it be much loss)
Aiming at 2 flexible 200w solar panels (light type) so guessing they will give average output of 6/7 amps at 24v in the hotter climates of spain and portugal? Dont need to get there quick and hopefully will only have the motors on for a third of the time, and will be charging whilst riding so guessing this will do the trick? Sleeping for 3 hours in midday sun so bats should catch up then.Can always have a whole day off from time to time to recharge bats.
Please can anyone in the know get back to me with what they would go for in my situation, should have about £800 per bike inc. solar panels to spend on power and storage so not a massive amount. Links to products would be the most helpful.Thanks in advance, jimi.

 

[D8ve]

Crank drive so granny ring gives the most effective power transmission up hills.
250 watt is continuos mode? Difficult area. Some manufacturers are inventive with figures but a 250 watt stamp on motor will save a lot of hassle .
Down hill you need a braked trailer or you risk death. Seriously, weak brakes heavy load and hills means high speed and loss of control.
More money helps too.
Some others will advise on crank kits I think whoosh were ready to do one?

Not to much risk on battery front as most purity good now but your charge circuits need to be good.

Best wishes on your adventure.

 

[Deleted member 4366]

You can fit a hub-motor as chain drive or use it with a 2:1 reduction ratio by fitting it between the crank and the rear sprocket/s. With the derailleur on the motor, you can fit a drive sprocket on the disc side to drive the rear sprocket through a chain. By adjusting the ratio of the two sprockets, you can adjust the final drive to any speed to allow the motor to give better efficiency at a lower speed.

To use the motor as a chain drive, you only need to add a sprocket to the disc side and get a free-wheeling crank from Eclipse or Cyclone.tw.

Have a look at the posts from Kitchenman about two years ago with Stokemonkey in the title. He converted a two-wheel recumbent.

 

[jimi marshall]

Thanks guys

 

[jimi marshall]

Hi i am thinking for going for the following:
Batteries - http://www.ebay.co.uk/itm/321378519778?var=510263732440&ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649 2x per trike
MPPT charge controller to give LI-Ions a stable voltage http://www.midsummerenergy.co.uk/buy/MPPT-solar-regulators/emponi-sol1-MPPT-regulator.html
100w 12v panels (2x if money allows) per trailer
http://www.ebay.co.uk/itm/380687876587?var=650120589657&ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
Still deciding on hub motor.Any comments?

 

[D8ve]

£200 batt £100 mppt charger£200 for solar cell. How much for motor and controller ?
Note £100 gets you the 60 watt solar cell in stead of mppt charger is this the way to go?

Is a cheap electric bike better? And use for parts?
Amazon have several at £500 complete.
eBay can come up with a bargain too.

 

[twinkle]

Greeting Jimi

regards emma

 

[jimi marshall]

Hi,
good point d8ve, but stock electric bikes aren't usually geared up for heavy loads and solar charging. Found this mid drive for £330
http://www.wooshbikes.co.uk/?cdkit Can't view spec so dont know wattage though
or this unbranded model http://www.ebay.co.uk/itm/New-upgraded-36V-250W-Mid-Drive-Brushed-Motor-ELECTRIC-BIKE-KIT-/141255334190
I am a bit stuck now though, charging lifepo4's via solar does look risky and expensive to get the correct charge controller. Got a lot of good links but need uk based suppliers (most in us) as i need parts quickly and duty free.
Has anyone got a link to someone who has a detailed success story of cargo bike solar touring?
Also if i went with the panels charging sla as buffer via regulator feeding inverter to lifep04 36v, would it be possible to charge whilst using the motor?
If a lithium charger draws 260w 6a on mains, am i right in thinking this would be drawing 21.6 amps on a 12v sla (260/12 = 21.6)??

 

[jimi marshall]

Maybe getting a bit confused. 36v at 250 watt = 7 amps approx. So the unbranded mid drive at full wack shouldn't exceed this i guess. Therefore if i can charge a SLA bat with 200w 12v flexi panels with Mppt or pwm regulator and constantly be inverting this (sine wave inverter with good cooling fan) to charge a 36v lifepo4 with a dedicated charger,after inverter losses and charge losses which could be 50%,so call the panels 100w, i would still be putting in about 2.7amp (100/36) minimum i guess which if motors are only used for a third of the time at full whack i should be alright??
Any ideas what minimum ah SLA bat i could use as a float for this without killing it and could i trust the inverters low voltage cutoff,and the lifepo4 chargers overcharge cutoff?

 

[jimi marshall]

oh and do you think the inverter and the charger would be cool with this sort of use, at about 5 hours a day?

 

[D8ve]

The 250 watt is continous rating, some pull over 20 amps.
Yes ready built bikes are not geared up for cargo but.
You are talking of stripping and building you're own setup.
Starting with a cheap working bike is one way to get the stuff you need.
As stock charging while running is not standard( you need a hell of a long extension to do so)
SLA = weight. Better spare lithium batt for swapping as you go.
Whoosh have a good name here. And are UK legal as sold.
Talk to Hattie about your needs.

D8veh and Flecc realy understand the gear. I am still in training on this.

 

[Deleted member 4366]

Maybe getting a bit confused. 36v at 250 watt = 7 amps approx. So the unbranded mid drive at full wack shouldn't exceed this i guess.

You can use any motor as long as it's designated 250w in a catalogue or by the marking on it. There's no limit on current. Voltage can be up to 48v, although there's some confusion about wether that means 48v max or a 48v designated battery. I heard of a SGS test house that refused certification on a 48v battery because it's actual voltage was over that, but it's possible that they're interpretation of the standard was wrong.