Only getting 0.5 mile per charge ever since not being able to charge very low batteries for several

[Cody196]

Hey i am only getting 0.5 mile per charge ever since not being able to charge very low batteries for several days, any idea why this is? My friend lost my original charger last month and i jsut bought the batteries last month too before he lsot the charger, since then the batteries been low for a few days like to the point my bike could barely move. Since then i've been getting such a short range when i used to go like 5 miles per charge. What happened? I have 4x 12v 7ah batteries by firstpower from ebay. SLA batteriez

 

[cbmojo]

Hey i am only getting 0.5 mile per charge ever since not being able to charge very low batteries for several days, any idea why this is? My friend lost my original charger last month and i jsut bought the batteries last month too before he lsot the charger, since then the batteries been low for a few days like to the point my bike could barely move. Since then i've been getting such a short range when i used to go like 5 miles per charge. What happened? I have 4x 12v 7ah batteries by firstpower from ebay. SLA batteriez

Sounds like your batteries are out of balance...let them slow charge for 24 hours to see if they start to balance back out....if you get more ride time after 24 hours then you know it's the balance and repeat the process for 48 hours...

 

[harryS]

SLA batteries probably aren't the best choice for a higher power e-bike. Might run a slow Izip bike, a kids scooter or a wheel chair for a long time, but they don't like high currents, and go bad.

When you run out of power, put a volt meter across each battery while doing a load test, which is holding the wheel off the ground and giving it throttle. It might be that three of them will show 10-12 volts, and the fourth will only be 6 volts. That one would be the bad guy. Probably if you tested it without a load, it would read out 12 volts.

 

[Alex M]

SLA don't usually need balancing.
But they need a certain charging regimen, a 3-stage charging. This is the only thing that can be said with all certainty at the moment. Without further data it is all guessing.

4*12V doesn't tell me anything. Four batts can be wired either in parallel or series, or series-parallel. The result will be output either 12V (unlikely), or 48V, or 24V.

For 12V battery the charger should FIRST bring it to ~14.5V, THEN keep it at this voltage for 30-90 minutes, THEN drop the voltage to ~13.6V and keep it there for at least a few hours. This is how proper 3-stage charger should work. Most automotive chargers are not 3-stage. Yours - don't know.

In any event, measure the voltage on open contacts before charging and 10-12 hours after charging. It sounds like your battery is not charged. Possible reasons: bad battery, bad wiring between those 12V units, bad charger. The chart for State of Charge vs open circuit voltage:

For 24V - double the above numbers, for 48V - quadruple them. The chart is for regular "wet" battery. Sealed AGM batts have slightly higher voltages. Also, there exist hybrids of AGM and gel, with different voltages and different charging regimen. Buying a no-name SLA from unknown Ebay vendor is probably a bad idea.