Bike trip / solar panels

[Lars Wikstrom]

Hi, couple years ago I was planing a trip and had asked questions here, I put the trip on hold to update my house and now the house is finally sold this month. The bike trip is back on!

Things have changed in the last couple of years tech wise since I first asked some questions here and I have a couple more. I have an electric motor that will be running on 36v 13Ah Li-NMC batteries from this company.

http://www.hi-powercycles.com/hpc-elite-37v-13ah-li-nmc-ultra-high-performance-battery

These batteries have a BMS integrated, (built-in management system) that prevents the batteries from being over charged and depleted to far to protect the batteries. This allows solar panels to charge them without chargers, they use 'solar converters'. From what I understand the power flows through the panels and right into the battery and the power requirements need to be adjusted to fit the max or voc of the battery for it to work right, I think?

Here is a 2011youtube video of him explaining it with a 60w solar panel. Jump to 1:20 for the details https://www.youtube.com/watch?v=gbB9MtQp6Nw

Here is the thing I am trying to find out. Their 300w panels are $2400 and are 36v max and 43.3 voc

http://www.hi-powercycles.com/hpc-suncapture-300-folding-solar-panel-and-charger

I found another company that sells this same panel for $1650, but it has a max of 18v and a voc of 21.6v voc. They won't sell the Charge Converters alone and I am wondering if I can buy a 'Boost Converter" to up the voltage from 18v to 36v, or the numbers it needs to be for the cheaper solar panel?

Ebay has this converter that takes 6v-40v in and outputs 8v to 80v.

http://www.ebay.com/itm/Digital-controlled-400W-10A-constant-voltage-constant-current-DC-boost-Converter-/171122662244

I doubt it is going to be this easy to buy the cheaper fold out panels and just boost the voltage to meet the batteries voc.

Thanks for any help.

-Lars

[jflorey2]

These batteries have a BMS integrated, (built-in management system) that prevents the batteries from being over charged and depleted to far to protect the batteries. This allows solar panels to charge them without chargers, they use 'solar converters'.

You can't use BMSes as charge controllers. They will tend to do a very poor job and fail quickly.

One of the Genasun controllers (I think it's called Solarboost) will boost the ~16 volts from a standard 12 volt panel to the 42 volts that your battery will need.

Ebay has this converter that takes 6v-40v in and outputs 8v to 80v.
http://www.ebay.com/itm/Digital-cont...-/171122662244

That's a straight boost converter and will quickly "crash" the panel down to a fairly low voltage. You need something that will work well with the source impedance of the panel.

[Lars Wikstrom]

You can't use BMSes as charge controllers. They will tend to do a very poor job and fail quickly.

One of the Genasun controllers (I think it's called Solarboost) will boost the ~16 volts from a standard 12 volt panel to the 42 volts that your battery will need.


That's a straight boost converter and will quickly "crash" the panel down to a fairly low voltage. You need something that will work well with the source impedance of the panel.

jflorey2, Thanks for the info. I did a search and found this company http://genasun.com/all-products/sola...ost-controller

My question is, will these solar chargers that charge LifePo4 batteries also charge LI-NMC? They are both lithium batteries with a different chemistry if I understand it correctly?

Also I don't understand why a built in BMS, inside the battery, would hinder the charging? I guess I am thinking of the BMS like a faucet. It's open and currents flowing through it, and when it reaches its max charge, or discharge, it closes the valve so to speak to stop charging or draining? Their website claims that their 600w batteries are charged in 2 hours with good sunlight. Are they tricking the consumer or is it something that will just get worse over time charging it this way? from the video they just connect the panel to the battery using a "Lithium Ion Phosphate Charge Converter", which I am guessing is for the LifePo4 batteries.

Thanks again, next month I start to order the parts and start building the touring bike so I am trying to figure out what to get and research as much as I can.

-Lars

[jflorey2]

My question is, will these solar chargers that charge LifePo4 batteries also charge LI-NMC? They are both lithium batteries with a different chemistry if I understand it correctly?

Both Li-ion and LiFePO4 batteries charge the same basic way - via CC/CV charging. That means you first regulate the current (for bulk) then the voltage (to finish.) Li-ion batteries charge at between 4.1 and 4.35 volts; LiFePO4 batteries charge at around 3.6 volts. You will have multiple batteries in a string; string length times charge voltage will determine charge voltage. Most Li-ion 36V packs charge at 42 volts and the Genasun can be ordered for that.

Also I don't understand why a built in BMS, inside the battery, would hinder the charging? I guess I am thinking of the BMS like a faucet. It's open and currents flowing through it, and when it reaches its max charge, or discharge, it closes the valve so to speak to stop charging or draining?

No. BMSes have one primary job - protect the battery from damage. They usually do this by disconnecting the battery under conditions of high voltage, low voltage, or discharge current too high. Some also cut out when charge voltage is too high, and some also balance the battery. They CANNOT be used for terminating charge, since they won't cut out until the battery is already over voltage. It's a last ditch protection against fire, not a charge termination system. You need a separate charge controller, always. (The BMS will not HINDER charge if used with the appropriate charge controller though. You normally don't even notice it's there; it's only during failures that the BMS cuts in to protect the battery.)

Their website claims that their 600w batteries are charged in 2 hours with good sunlight. Are they tricking the consumer . . .

Yes. 600 watts is power, not energy, and does not tell you what the battery capacity is. Also, "good sunlight" tells you nothing about what power they expect from any given panel. So that line basically tells you nothing, You can charge any li-ion or LiFeP04 battery in 2 hours with enough power.

or is it something that will just get worse over time charging it this way? from the video they just connect the panel to the battery using a "Lithium Ion Phosphate Charge Converter", which I am guessing is for the LifePo4 batteries.

OK, then that's the charge controller.

Thanks again, next month I start to order the parts and start building the touring bike so I am trying to figure out what to get and research as much as I can.

My suggestion - build an ebike first (with conventional charger) and get used to it before starting on the solar part. Solar is easy to add later.

[Lars Wikstrom]

Thanks! I have been packing the last couple of days and just getting back to this post.

I am going to call the battery company tomorrow that makes the bike battery. I am wondering if they build / design the BMSes that they would set the limits on them so the BMSes don;t harm the batteries? Most people will ride the bikes till the battery is depleted and if they set those limits to low to harm the battery or to high to also harm on the charge then that would ruin a lot of batteries. I will call and ask them what the cut off voltage is.

Your idea of the bike set up is exactly what I want to do first.

The other solar panel charger for the one on the trailer looks perfect since ti is a 12V input and unto 140w 10A

http://genasun.com/all-products/solar-charge-controllers/for-lithium/gv-10-li-lithium-10a-solar-charge-controller

The semi flexible panel 100w 12v http://www.ebay.com/itm/Semi-Flexibl...-/161669212758

Your solar charger and that panel should work out well together, thanks!

-Lars