Looking to set up a solar charging station for E-bike batteries

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I have a friend that owns a bike rental place. They have been given a grant to electrify their cargo bikes and to build a solar charging station for e-bike batteries. This includes the batteries from their rental fleet e-bikes which will be commercial type batteries. Because the grant is for only so much money I am trying to keep the components of the build to a minimum. Can I go direct from a solar controller to the bike batteries or from a storage battery to the bike batteries or do i need to add an inverter to charge the bike batteries?

 

[john61ct]

Endless-Sphere is a better forum for this topic.

There are good solar controllers that output 48V range, usually PWM and boosting voltage from the panel output.

Better to look for MPPT for efficiency, buck converting down to 48V battery storage.

48V is a good "system backbone" voltage.

Ideally the bikes use that for their packs, cargo bikes need a lot more current handling for high torque rather than voltage for top speed

high amp controllers are large and cost more, ideally FOC type

efficiency (Wh per mile) will require specific Kv / winding count in the motors.

Build the battery packs to be easily swapped, and the BMS easily swapped out from the pack as well, leaving the balance leads accessible for balancers, balancing chargers, monitors testers etc

LFP for longevity and safety, not the usual 3.6-3.7V high density fire-prone chemistries usually used for eBike packs.

Charging direct from the SC into the bike packs will be ideal for both cost and efficiency, check out Victron's line.

If needed for time-shifting, then use a large 48V LFP storage bank as "mothership"

use DC-DC converters, or proper DC-DC chargers to get up to the correct spec'd charging voltage between the source mothership bank and the target ebike packs. An inverter to use an AC-DC charger is very inefficient and a waste of money.

Charles Sterling makes top notch DCDC units, but not sure about 48V. Victron is also excellent.

For LFP, a 48V pack is 16S, 53V at rest isolated is 100% Full, 55V is a good charge setpoint for longevity, 51V is 50% SoC at rest "nominal" 50V is a good cutoff for longevity and 48V is "drop dead 0%" do not allow any lower.

Do not let LI packs sit at high SoC% for long

Storage voltage when not actively being cycled should be isolated, no BMS if long-term, cool temps and at between 51 and 52V no higher.

 

[john61ct]

Obviously if you decide on 48V as your standard, you would not order packs at a different voltage.

There are very few commercial pack builders that make a decent product at all, much less the IMO essential specs I outlined.

If you want good quality you purchase a big lot of the desired cells from a trusted vendor, most likely self-importing from China

and then either spot-weld the packs yourself or commission a trusted pack builder to do it for you, ideally a local.

Otherwise you spend many thousands on crap that dies and needs to be replaced in a year or two.

Lots of scammers out there, but the "honest" big companies are the worst rip-offs.

Do NOT accept bikes or conversion kits that require proprietary parts you want to be able to maintain and repair / upgrade yourself.

Test a variety of single units before placing a big order.

In most cases ignore any verbiage about warrantees, usually useless.

 

[Photobug]

If you build custom DC to DC charging. What happens when next batch of bicycles use a different battery ?
I suggest using using an inverter to supply the mainspower charger thats intended for the specific bicycle.

Charging lithium batteries is not rocket science, but its not something should be trusted to an average bicycle renter.
Let the automatic controls of the intended charging system do its thing.
The user and their Landlord/Insurance Co. will be happier.

This is not for public (renter) use this is for use in their shop only. I think you are right though it may require an inverter. When I went in to show my friends my home build solar charger I was explaining the components. I was explaining how the solar power goes from the Solar Panel to the MMPT to Battery to Inverter to Power Brick to Bike Battery. While it may not be possible, it sure would be nice to cut out as many moving parts as possible.

 

[Photobug]

Obviously if you decide on 48V as your standard, you would not order packs at a different voltage.

There are very few commercial pack builders that make a decent product at all, much less the IMO essential specs I outlined.

If you want good quality you purchase a big lot of the desired cells from a trusted vendor, most likely self-importing from China

and then either spot-weld the packs yourself or commission a trusted pack builder to do it for you, ideally a local.

Otherwise you spend many thousands on crap that dies and needs to be replaced in a year or two.

Lots of scammers out there, but the "honest" big companies are the worst rip-offs.

Do NOT accept bikes or conversion kits that require proprietary parts you want to be able to maintain and repair / upgrade yourself.

Test a variety of single units before placing a big order.

In most cases ignore any verbiage about warrantees, usually useless.

I am still learning the bike part of this. This shop has a retail component but is mostly in the bike rental business. Except for the new cargo bikes they are electrifying they have high end bikes with either Shimano or Bosch batteries. I am having them reach out to the manufacturers or suppliers they get their stuff from to see if the companies have a DC to DC solution.

The new cargo bikes willl be used only for short deliveries in town and they have been using them a few years without any electricity so the motor will be used mostly to help accelerate from stops.

 

[Alloy]

If you build custom DC to DC charging. What happens when next batch of bicycles use a different battery ?
I suggest using using an inverter to supply the mainspower charger thats intended for the specific bicycle.

Charging lithium batteries is not rocket science, but its not something should be trusted to an average bicycle renter.
Let the automatic controls of the intended charging system do its thing.
The user and their Landlord/Insurance Co. will be happier.

Seeing some of the DIY Lithium setups is frightening. If a system that's to last 10+ years doesn't catch fire in 6 month it is deemed to be fullproof so people copy it repeating the same mistakes.

 

[Photobug]

Seeing some of the DIY Lithium setups is frightening. If a system that's to last 10+ years doesn't catch fire in 6 month it is deemed to be fullproof so people copy it repeating the same mistakes.

Just to clarify this is not the plan here to "build our own lithium battery pack". Every bike battery pack is commercially made. Any battery we will be using to store the power during the day till the bike batteries can get charged will be a commercially made battery.

Have you seen a DIY system you think was well made and safe?