Question regarding charging an EV Warrior electric bike

Your a lucky dude finding a free electric bike, its sickening how people dont attempt to fix things these days, we really do live in a disposable product society

Im going to assume the batteries are lead acid. Sorry but theyre probably gone, if a lead acid battery is left discharged for any significant amount of time they will just die or lose a significant amount of capacity. This is due to sulfation of the lead plates, sometimes with flooded batterys that have the feature of being able to add water you can reverse this procedure, but with new sealed batterys im afraid to do this because you will lose water. You usually just force a charge into them an "equalizing" charge i believe its called you hook the battery up to a ~15 volt power supply and leave it for 2 to 3 hours very stressful on the battery but a stressed battery is better on a dead battery. In my opinion with a voltage of less than one volt for god knows how long these batterys are long gone. As for the charger you cant really say being that theres no output without a battery, these batterys are probably just confusing it.

I hope this helps I know the lead acid chemistry pretty thoroughly if theyre nicd or nimh or li ion i cant really help you that much.

also i wish somebody would reply to my post its a couple posts down from this one.

and good luck with your bike im currently in the process of building one

I see, so the charger knows what to do based up what it is connected to.

Thank you. Would you know of a good source for batteries for this?

-Jim

i usually buy batterys from here your gonna have to measure your old ones and find one similar in size. If you want a really good battery that can handle deep discharges the hawker enersys odyssey is your battery, but they cost about 100 bucks a piece, the generic sealed lead acids should serve you well. But charge them as soon as you get home, the less you discharge them and the less time they spent discharged are the two major factors in how long they last, and resistance to damage from being in a discharged state is the difference between a quality battery and a crap battery.Ball park figures is that you should get low hundreds of cycles from high discharges(100-300 cycles 80% discharge) and high hundreds to low thousands with low discharges(800-1200 cycles 20% discharge). I think the best compromise is around 40% discharge to get the most total power. Note that car batterys are a different beast and will not tolerate at all being completely discharged going to 100% discharge will kill them in about 20 cycles they are designed solely for low duration high amp output( just a tidbit of info that doesnt really apply).

And for the battery charger thats a guess of mine, automatic battery chargers do monitor the battery voltage and react accordingly. What the charger does when no battery is hooked up is dependent on the programing, im sure a fraction of a volt is "no battery connected" as far as the charger is concerned.

good luck with your bike

i sat down and thought about the charger and came up with one of three possibilitys. One is that the charger checks the voltage before hand and assumes that there is no battery connected because the battery voltage is a fraction of a volt. Two is that the charger doesnt determine if there is a battery connected it just turns on. If the battery is really badly sulfated it will have a high resistance so the voltage goes up, all the way up until the charger is tricked into thinking the battery is charged and it shuts off.

You would need an oscilloscope to see if this is happening, or if you happened to have two other leadacids lying around you could test the charger, possibly you could use a high wattage resistor, it would have to be some serious wattage though, and the charger would have to not be checking if a battery is connected.

Third possibility is the charger is fried.

Remove the batteries. Wire them in parallel and charge using a "dumb" charger. You might be lucky.

Normally i would agree with you 100% but with the batteries being at a fraction of a volt for probably a long long time i really doubt it. But yeah miracles do happen its worth trying it. But be aware the process of reviving a sulfated battery does let off quite a bit of hydrogen from the water your "boiling" off, keep the window open.

Correct me if I'm wrong, but is not each of the batteries 12v? Could I not just pull them out and hook them individually to my car charger?

-Jim

leeps wrote:

On Mon, 24 Jul 2006 08:17:37 -0700, jtpryan top-posted:

Well, from the sound of things, you pretty much have nothing to lose. :-)

Give it a shot, but do it outdoors. ;-)

Good Luck! Rich (and typically bottom-posting is considered polite here.)

Im not sure of the no load voltage on a car battery charger. The high impedance of a sulfated battery will make it appear as if its nearly an open circuit for the battery charger. If you have a 'dumb' charger by all means hook it up, check the voltage. It should be ~ 15 volts leave it for about 2 hours.

Joe

My bet is that the charger is fine and the batteries are shot. Your idea of putting the batteries on the car charger individually is great. Make sure that the plates inside the batteries (if they are wet cells) are covered by the electrolyte before doing that. If they are not covered, add distilled water (available at the supermarket) to bring the level up.

To test your charger, this might work: connect 2 9 volt batteries in series with 4 1.5 volt batteries. Connect that assembly, which produces 24 volts, to your charger through a 10 ohm resistor. Measure the voltage drop across the resistor. By observing polarity, you can tell whether the charger is trying to charge the battery or the battery is trying to "charge the charger". If the charger is trying to charge, it is working, at least partially. You don't want to leave it set up that way for long - just long enough to see if the charger tries to charge your assembly.

Ed