Hello from New Zealand

[yeosteve]

Hi everybody,

I'm a newbie at solar/charging/batteries etc.
I'm looking for help to spec up a solar system to charge up my e-bike overnight while I'm campervanning around. Actually 2 bikes. Which is the best forum to ask for help like that?

[Mike90250]

Hi everybody,

I'm a newbie at solar/charging/batteries etc.
I'm looking for help to spec up a solar system to charge up my e-bike overnight while I'm campervanning around. Actually 2 bikes. Which is the best forum to ask for help like that?

This may be a shock, but solar chargers only work in Daylight, Adding enough solar to your bike, to charge while you ride, gets awkward very rapidly,

[DrLumen]

yeosteve, welcome!

Just to make sure I understand you correctly, you want to be able to charge batteries during the day using solar panels and then use that battery power to charge your e-bikes at night correct?

I can't help as I know nothing about battery backup systems. Just to throw this out for fodder, how about having 2 pairs of batteries for the bikes with one set charging during the day while the other pair are used in the bikes?

Or, perhaps use your current chargers directly from a solar inverter - again using 2 pairs of bike batteries. In the latter, you would just need enough solar panels and an inverter to meet the specs for the pairs of bike chargers based on an estimate of the amount of sun (hours) available.

These may be expensive options based on the cost of bike batteries but you could be buying different batteries to charge so it may just be a break even type situation. Seems like there would be some loss going from battery to battery as well. This is also assuming you come home every night.

There are people here that can help. Some people may have a bit of tunnel vision and are deep in the technical before all the facts are known.

[AzRoute66]

It would help to know as much as possible about e-bike batteries (and e-bikes for that matter). What is the charge profile in terms of power and time? What are the characteristics in terms of chemistry, volts, and amp-hours? How many battery sets might you use in a full day? Finally, have you seen other systems for battery charging, if so what elements of that were things you liked and what were things that were less than satisfactory?

[yeosteve]

I'll reply to all at once, and thank you for your responses so far.
1) Duh. Of course I realise that solar only works in daylight. My idea is that we take off on our bikes all day and return to the campervan/car./tent/whatever each night, plug in the bikes to recharge, then repeat the next day.

2) Yes, there would be losses between charging one set of battteries, then another, but bike batteries are going to change a lot and I don't want to ownb extra sets of batteries for the current bikes when the next bikes will haver different ones. The new Bulls bikes have 750 watt-hour batteries.

3) W get 80 - 120k range with the exisitng battery which is more than enough for an old fella.

Did I mention that i'm not building my own bikes or charging system. I'm hoping to be able to find off the shelf solution that will lete me use the chargers that came with my bike

http://www.bullsebikes.com/product/e-stream-evo-fs-3-27-5-3/

Inpur 240V 50Hz 2.0 amo
Output 42V 4A

The battery is 37V 650 watt-hour.

I'm hoping someone can simply tell me I need solar panels x big, which regulator, a battery y big and an inverter that does this, that and the other. I would really like to use the equipment that came with the bike as much as possible, and simply (!) set up a system that will store the solar power during the day for overnight use. I don't need to store 3 days worth for times when there's no sunlight because I'm unlikely to go biking when the weather is crap anyway.

[Mike90250]

> The battery is 37V 650 watt-hour.
Lets call that 18 Ah @ 37V

A typical wally-world deep cycle battery is 12V 85Ah or 1020watt hours - So one battery will be deeply (more than 50%) discharged with a loss-free transfer of power.
A quick guess gives me that 3 deep cycle batteries would be needed to recharge both bikes overnight, without damaging the Lead Acid deep cycle battery
Instead of 3 parallel 12V batteries,
I would suggest 4 golf cart batteries 6v, 200ah (model GC2) wired 2 series, 2 parallel, to provide 12V @ 400ah (4800 wh).
It will provide a longer life (less deep of discharge) of the lead acid batteries. You can get them in Sealed AGM versions, $300 ea or Flooded $100 ea.
You will need an efficient inverter to not waste power. There are several 12V, Pure Sinewave, sub 500w inverters on the market, but they are close to $300

Solar Charging the Lead Acid battery bank.
Assume 4 usable hours of sunlight (10am - 2pm) outside those hours, harvest falls off rapidly. Your chargers and inverters will have roughly consumed 2,300 watt hours overnight
and about 20% more will need to be harvested into the lead acid bank (2,800 watt hours in 4 hours) gives 700 watts per hour. PV panels generally produce 80% of nameplate power in good conditions (cool, full direct sun, proper aim) So having 840 watts or more , of Solar panels would do it. And a 70A solar Charge Controller

Options:
Wire and configure the 4 GC2 batteries into 24V and only need a 40A charge controller, but 24V systems limit the choices of inverters

[yeosteve]

Wow. Thanks, Mike, that's exactly the sot of info I needed. That will give me a fun week or two of researching and learning.

[AzRoute66]

I would focus on the inverter search. Being able to go to 24V with the batteries is very attractive unless you have other 12V stuff you want to 'throw on'.

I went to the website and saw the bike/battery, but I don't see any info on the charger. Could you provide a link to that? It is just a curiosity, don't spend a lot of time on it.

[yeosteve]

I would focus on the inverter search. Being able to go to 24V with the batteries is very attractive unless you have other 12V stuff you want to 'throw on'.

I went to the website and saw the bike/battery, but I don't see any info on the charger. Could you provide a link to that? It is just a curiosity, don't spend a lot of time on it.

https://akkuplus.de/mediafiles/Daten...20150715-1.pdf It seems to be a mix of German and English. I also found

https://akkuplus.de/Tischladegeraet-...olt-40A-Li-Ion

which, after Google Chrome translated it, has a better description

[AzRoute66]

Thanks, the second link was exactly what I wanted. It appears to be a constant current/constant voltage charger with a qualification stage to get it up to 25V before it starts in earnest. I like Mike's numbers, but again out of curiosity only, approximately how long does it usually take to bring a well discharged battery pack up to full charge?

[yeosteve]

Thanks, the second link was exactly what I wanted. It appears to be a constant current/constant voltage charger with a qualification stage to get it up to 25V before it starts in earnest. I like Mike's numbers, but again out of curiosity only, approximately how long does it usually take to bring a well discharged battery pack up to full charge?

About 4.5 hours from completely discharged.

[AzRoute66]

Nice system. Mike's numbers seem a little bit beefy, but not wastefully so. I'd add that if you have to choose between something a skosh under or something over, you shouldn't automatically go over. His template on how the numbers were derived will be helpful in making a good decision.