Author Topic: eBike charging efficiency  (Read 2346 times)

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dnix71

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eBike charging efficiency
« on: January 19, 2013, 12:10:13 PM »
I made a trip yesterday on my Curry eBike with a Turnigy attached. It reported 140wh used from the pair of 35ah 12v slas I put on the bike to increase it's range. When I got home I plugged in a 4 amp charger. The original 2 amp charger is very slow on the larger batteries and it cuts off the charge at 28.8v. The 4 amp charger cuts off at 29.8v. According to my Kill-A-Watt meter it took 170wh to recharge the batteries. That means I waste about 20% recharging batteries after a trip.

Simen

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Re: eBike charging efficiency
« Reply #1 on: January 19, 2013, 02:30:04 PM »
Tell us....
Does your new charger temperature compensate and your old one doesn't? And was it on the chilly side when you charged with the 4A charger?
That would explain the cutoff difference; at around 10deg. Celsius, a boost charge of 29.8V sounds correct...

Edit;
If it was a while since you charged the batteries before your trip that drew 140Wh, the self-discharge could also explain some of the difference...
Besides; charging FLA's are not 100% efficient... :)

 
« Last Edit: January 19, 2013, 02:34:15 PM by Simen »
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dnix71

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Re: eBike charging efficiency
« Reply #2 on: January 19, 2013, 03:50:30 PM »
It's been overcast all day, but the temps have been around 70F. It rained this morning. I live near Fort Lauderdale. I don't think the charger compensates for anything. I've watched it before and it just humps along until the voltage on the pack hits 29.8 then it abruptly stops and goes to float at about 27.6.

http://www.monsterscooterparts.com/24-volt-4-amp-xlr-charger-coming-data.html This charger. It's made for Currie by Coming Data. It has a full time fan when charging, you can easily tell when it's finished even if you can't see the red/green led. To limit sulfation I don't let the batteries sit before charging them. The batteries were 2 for $70 at Radio Shack one week. They are UB 12350 size.
http://www.batterysharks.com/Universal-Power-UB12350-D5722-p/ub12350_b12-35.htm?gclid=CMKj0-S-9bQCFQGvnQodDjMA-w This battery.

I don't even know who made the batteries. They have a vinyl label that says "Universal Battery" 1-866-892-1122 is the contact number. That goes to Universal Power Group in Carrollton, Texas. http://4components.com/aboutus.aspx They might have been made in Mexico, since there are/were lead acid battery recyclers there.

It's fun having that much battery on a bicycle. I can run 2 watt led light strips and not even notice the drain. If I go back to using it for work transportation, I'll put a 12v power tap back on for a compact air pump. I could run a radio/mp3 player from it but bicycling in south Florida takes too much concentration to want to risk being distracted.

OperaHouse

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Re: eBike charging efficiency
« Reply #3 on: January 20, 2013, 03:59:21 AM »
Off hand the numbers seem reasonable.  The charger also has losses so you should be using the Turnigy to see what is actually going into the battery.   The Turnagy senses current in the negative lead.  You should avoid passing current through the positive leads to prevent voltage loss and excessive heating of the unit.   That allows a very low current normally closed pushbutton to be used in the positive lead to reset the unit.  Since it only measures current in one direction, a reversing switch could be used on the two negative leads.   A two terminal connector like  a non polarized AC plug could also be used on the negative leads to reverse current flow for charging.