36 Volt Solar Voltage regulator

Positive discussion on ebikes and pedal assist bicycles

36 Volt Solar Voltage regulator

Postby Joeblake » Wed Mar 14, 2012 1:19 pm

I was at a meeting of the local sustainability group over the weekend and I was approached by a lady who had an e-bike and she wanted to know whether she could have some photovoltaic panels added on to give her a "constant solar charge" capability such as I have on my (24 volt) trikes, which haven't drawn power from the local grid in over 2 years. Sadly I had to tell her that it was not going to be possible since her machine had a 36 volt system, and whilst it was not difficult to construct a 36 volt PV array, the problem was that to prevent damage to the batteries, there would need to be a 36 volt regulator to disconnect the PV array from the battery when it was fully charged.

I did a bit of 'net surfing this morning and it seems that 36 volt regulators are extremely rare, in fact almost non-existent as far as my searching went. However, in the way that sometimes happens when surfing around I came across this page

http://www.crystel.com/Solar/Tractor/active.html

where the author gives brief instructions on how to convert a Solarex SC-18 regulator to handle 36 volts.

A word on regulators.

Elec-Trak tractors require 36 volts to operate. From a solar standpoint this can be a bit problematic, since most solar systems are either 12 volt, 24 volt, or 48 volt systems. Thus there aren't many regulators out there for 36 volts.

By chance I found a 36 volt model from a company called thelastplaceyoulooked.com. They apparently bought a lot of solar equipment from Australia, and in Australia they use 36 volt systems much in the way we use 48 volt systems here in the states. The Solarex SC-18 controller fit the bill perfectly: It could be configured for 36 volt operation by changing a solder-pad setting, and it was a two stage charger to boot.

Changing it to 36 volts is not a completely simple task. In order to do this you not only need to know how to solder, you need to know how to *remove* solder, since you will take the solder off the 12 volt pad while putting a new solder joint on the 36 volt pad.

Once the regulator was installed, I ran a 25 foot extension cord (outdoor rated) out to the tractor. I terminated it with a 20amp Hubbell twist lock connector, which plugs into the Elec-Trak's option power supply.

As soon as the tractor was plugged in, the charge light came on, and the tractor began to accept a charge. In checking with my Ammeter, I noted that the tractor was pulling almost the same amount of current that would be pulled from the panels in a direct short to ground, indicating that the system was functioning at maximum performance. Initial charging rates were up to 4 amp/hours.

Further, I found a local (Perth) link to a place which sells this item ($20).

http://www.gumtree.com.au/s-ad/perth-re ... /351281406

If the lady with the 36 volt bike contacts me again (I gave her my card) I'll suggest this to her, and maybe see if I can tinker something together.

Otherwise, I'm putting this up for those who have 36 volt systems and are wishing to build an "on-board" PV battery charging system. If you do attempt this yourself and it works, please post it up here, and I'll do the same.

Joe
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Many people feel their lifestyle has a high price, but they're quite cool with that .. as long as somebody ELSE pays the price.
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by BNA » Tue Mar 20, 2012 3:24 pm

BNA
 

Re: 36 Volt Solar Voltage regulator

Postby rcmkII » Tue Mar 20, 2012 3:24 pm

My bike runs at 36v and I often tow a trailer behind it. My goal is to assemble a 36v panel for the trailer so I can extend my range in daytime, without adding a whole lot of weight. (E.g. avoid carrying a second set of batteries)

This sounds like the right kind of voltage regulator, and I have no problem with soldering or de-soldering. The only problem is that the item just disappeared off Gumtree and I can't find anything on ebay either.

I've made a note of the item and will keep an eye out though. Appreciate the info.
Riding and writing my way to health and happiness.
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36 Volt Solar Voltage regulator

Postby Riggsbie » Tue Mar 20, 2012 4:01 pm

Good find !


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