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Battery Charging - Question

I recently built an electric wagon.  I started out with 10AH batteries (2 - 12V batteries) and that proved to be too limited a running time so I upped the batteries to 35AH (2 - 12V batteries).  Everything runs great, but I think I have run into a problem.  


I have a 2A charger, which obviously is going to take a long time to charge these batteries.  When I plugged the charger into the new (and should be charged) batteries, it lit green but when I then plugged the connected charger into the wall, it lit red and stay that way for 5 hours before I pulled the plug.  I am using the SPD-24500B controller.  First question, any thoughts on why the recharger never lit green?  The batteries are new and I only have about 20 minutes of use on the batteries.


Second question, I am considering getting a better charger (7A) but I am concerned that the SPD-24500B controller might not handle the current output from the charger - will this be an issue?  Third question, if this is an issue, can I just alligator clip the charger to the batteries and bypass the controller to charge the batteries?   


Last and unrelated question, my throttle (THR-73) has a green connector for the battery meter.  What connector do I attach this to on the SPD-24500B controller? 

New batteries typically have not been charged since they left the factory and will take a while to charge for the first time. I would expect that the battery charger light will turn to green if it is left charging the battery pack for a longer period of time. It is recommended by most battery manufacturers to charge new batteries for 10-12 hours with a standard size battery charger, so with a battery charger that has 60% less output than standard I would charge the batteries for 24-30 hours for the first charge. During the initial charge of the battery pack the charger should be left on the battery pack after its light turns green to trickle charge the new batteries to condition them for the first time.


The SPD-24500B controller is rated for battery chargers up to 3 Amps. The wires between the controller and its battery charger port plug are not heavy enough to put more than 3 Amps through. When using a charger over 3 Amps the charger port should be wired directly to the battery pack.


You could use alligator clips to recharge the batteries however I do not recommend alligator clips due to the possibility of accidentally connecting the battery charger in reverse polarity to the battery pack and damaging the charger. I highly recommend using a charger port which is permanently wired to the battery pack to avoid making any battery charger to battery pack connection mistakes.


The green battery meter wire of the THR-73 throttle should be connected to the red wire of the SPD-24500B controller's Power Light connector.


Please let us know if we missed any of your questions, or if you have any further questions.

Thank you for the prompt answers!  This has been a fun project.  I just wish the 35AH batteries were not so heavy!

batteries charged battery indicator reads dead. Less that a month old.

I assume that as well as the battery meter reading dead, the vehicle no longer runs or runs very slow. If this is the case then that points towards one or more of the batteries in the pack having failed, or the connectors or wiring between the battery pack and controller has come loose or failed, or the battery charger, charger port, or wiring and connectors between the charger port and controller has come loose or has failed.

I would start diagnosis with testing the Voltage of:
  • The charger port, to make sure it making contact with the battery pack.
  • The charger, to make sure it is working.
  • The battery pack, to make sure it actually has low Voltage and the meter is not malfunctioning.


These tests will tell you a lot about the condition of these parts. If the battery pack Voltage tests low then I would individually test each battery in the pack to see if one of them has a low Voltage compared to the others. Then I would load test the individual batteries to see if one of them is defective.


I would start with these tests. If the problem is still not solved after performing these tests then please let me know and we will take it from there. Please let me know if you have any questions.

That help`s but it run`s like it is fully charged , yes I did get a voltage meter that read 20 22  . haven`t ran it for at least a week, but I will check everything U said, and that I Thank U very much for getting back with. me.

At 20.22 Volts a 24 Volt battery meter will read that the battery pack is low on power or dead. A 24 Volt battery pack should charge up to 27.6 Volts, or somewhere close to that. Most 24 Volt speed controllers shut down when the battery pack reaches 21 or 22 Volts in order not to over discharge the battery pack and damage it. If the speed controller is running the motor and the battery pack Voltage is reading 20.22 Volts that is unusual however controller shut off levels can very by a Volt or two so it might be just about ready to shut down at that Voltage but has not yet.

If the battery pack is only charging up to 20.22 Volts then that will eventually damage the batteries from keeping them undercharged, so I would look into the battery charger or the batteries as possibly not working properly.

THANK YOU,THANK YOU, THANK YOU, It was a loose wire, in tight now, your are the best. and I'm going back outside to ride, thank you again your the best.

       P.S. It`s still fully charged, seeeeyaaaaaaaaaaaa.

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