36 volt eBike build

[wagoneer]

I picked up a beater 36 volt bike. Power pack was stolen so the previous owner just gave up and sold it for 80 bucks. In the process of building a power pack with 3 small agm (sealed lead acid batteries) I bought for 65 bucks and want to be able to charge them with solar. I realize most chargers are 12 volt and will not handle 36 volts aside buying a very expensive 36 volt charger do any of you brainiacs have a cheap idea?

 

[wagoneer]

I picked up a beater 36 volt bike. Power pack was stolen so the previous owner just gave up and sold it for 80 bucks. In the process of building a power pack with 3 small agm (sealed lead acid batteries) I bought for 65 bucks and want to be able to charge them with solar. I realize most chargers are 12 volt and will not handle 36 volts aside buying a very expensive 36 volt charger do any of you brainiacs have a cheap idea?

I thought about getting 3 cheap dashboard panels with cig plugs and using alligator clips.

 

[blars]

You could put the batteries in parrallel to charge and series to use, either a pain each time or a complicated switch. Inverter to AC charger would work, but inefficent. DC-DC converters for that application arn't readily avaialble AFAIK.

 

[wagoneer]

http://www.ebay.com/itm/141648450127?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT
would this work and hey thanks for the help

 

[offroad]

2 amps at 36 volts. Is it regulated? If your batteries are dead will the charger try to push more than 2 amps? Causing thermal overload and blowing internal fuse of charger? Please do a lot of reading on this before attempting.

 

[VJG1977]

This looks like a good 36v charger.

http://www.amazon 36V+Battery+Charger

A search on Amazon for 36v battery charger pulled up many from $12 to $300.

 

[ccbreder]

The charger for my e-bike 36 volt, 10 amp hr, LiFePo4 battery is 2 amp output.

 

[IGBT]

I wonder if you could use the battery and charger from one of the new style cordless power tools, like a leaf blower?

I see them on Amazon for about $100, some with a 40V 4AH Lithium battery, charger, and the power tool.  The cool thing would be to make it quick swap or have the option to put several in parallel.   160WH is probably about all you are getting from the AGM anyway, right?

 

[Varmint]

Aside from the obvious AC-powered solutions, you could get three 12-volt solar panels and use them in series. Under load, they'd put out about 40 volts. I'd use 10 watt panels, or up to 20 watt units if you want quick charge capacity. However, you really should use 10% of your battery's rated capacity as your guide. Hence, a 12v 7AH battery would use 400-700mA charging for 10-12 hours. A 10AH battery would be charged with 1 amp for 10-12 hours. This is a general rule of thumb. You could exceed that charge rate by charging for less time in direct proportion to this general rule.

If you already have solar panels with a 12V setup, I'd use what you have and charge that way (quick charge). An old trick for limiting the charge current is to put a 12v light bulb inline with your positive charge lead. This will limit your charge current to whatever the light bulb uses. In addition, when the light dims dramatically, you'll know you've reached full charge, or nearly so. A digital voltmeter will verify this. Full charge on any AGM/gell cell is about 14.4 volts, and verified by the label on the batteries.

Always check the manufacturer's own specs for the batteries you use, and do what THEY say. The above advice is only a general rule of thumb. There is NO reason to use any particular battery charger or method to get the right charge rate.

 

[wagoneer]

that may well be THE solution, thank you for your thoughts.

 

[wagoneer]

http://www.ebay.com/itm/131026090120?_trksid=p2057872.m2749.l2649&ssPageName=STRK:MEBIDX:IT

Just pulled the trigger on these and will wire them in series.

 

[Varmint]

I should point out that, if you use three panels in series, you should also use three light bulbs in series, and they should be of the proper wattage. That is, if using three 12v/7ah batteries in series, each light bulb should be pulling about 700mah each for a 10-12hr charge, and if you increase the wattage/ah rating of the bulbs, you'll get proportionally quicker charge rates. Also, you can add a switch to change from quick charge to slow/trickle charge by adding another set of light bulbs for this purpose.

Again, always use the recommended charge rate, as spelled out by the manufacturer. While the voltage and current you use may or may not seem important, the final voltage of your fully charged battery is EVERYTHING if you intend it to last. Equally important is NOT leaving it on charge for extended periods of time. My dad can't get this through his head, and he leaves everything on charge all the time, then wonders why everything can't hold a charge anymore. If the battery gets hot, you're over-charging it. After doing this repeatedly, you'll ruin it's ability to hold charge.