Adding batteries to system

This has been done many times, it's often called "buddy pairs." That's putting pairs of batteries together in parallel, and then putting these buddy pairs in series. Some racers have even done triplets.

Rum Runner said:

I bought a 72 volt system with six deep cycle batteries. At 30 miles per day per day round trip it looks like I will need more amp hours to use this vehicle.
I was planning to add to the system. Six batteries in series and six in parallel to extend the range. Would this be ok, or will I need to change the motor and controller?
If you know a link where this issue has been addressed, please let me know.

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Thanks for the response. I will look that up.

Rum Runner said:

I bought a 72 volt system with six deep cycle batteries. At 30 miles per day per day round trip it looks like I will need more amp hours to use this vehicle.
I was planning to add to the system. Six batteries in series and six in parallel to extend the range. Would this be ok, or will I need to change the motor and controller?
If you know a link where this issue has been addressed, please let me know.

Click to expand...

What vehicle are you using this system on, what motor/controller ?

Roy

The motor is L91-4003 Advanced Motor.
The controller 1209Curtis.
Going into a 95 Ranger, regular cab, standard Transmission, no clutch.
The Batteries are 12volt deep cycle with 125 AH

Just make sure that all the batteries are of the same type and capacity if possible. Should be no other significant issue.
72 volts is a rather low voltage for a small truck though.

Putting these batteries all in series would give you the ability to drive hiway speed however, you would need at minimum a different controller and charger. (unless you charged in two groups of 6).

Charging the parallel pack will work fine... it will just take longer.

I have a 72 volt charger. You think I will need a different controller?

Rum Runner said:

I have a 72 volt charger. You think I will need a different controller?

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No, if you hook them in "buddy pairs" (2 parallel x 6 series), as you suggested, your charger will work fine and your controller will work fine. Your string will still be 72 volts but your Ah rating will double. A 72 volt system with that truck will dictate some pretty high current requirements (if your controller can handle it... I don't know it's rating) which means you need to verify your battery conductor cable. What size cable do you plan to use?

I was referring to the possibility of hooking them all in series. This would make the string 144 volts which would exceed the voltage limit of your controller and also not match your charger. It would however (with the right controller) allow much higher speeds. Granted you would have to advance the brush timing on your motor .... or limit voltage to motor somewhat, depending on the controller you would change to (some offer this feature).

The motor is only 72 volt.
I am using Size 2, 600 Volt welding cable.

Rum Runner said:

The motor is only 72 volt.
I am using Size 2, 600 Volt welding cable.

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My motor was made for 36-48 volts. My battery pack is 192 volts. I limit the voltage to 160. You may run your motor to a higher voltage than 72. You need to determine if the brushes are advanced or not. My brushes are advanced 13 degrees. This helps to prevent brush arcing. Look at the alignment of the each brush as compared to the field winding centre lines. (mount screws) Other members including "Major" can help you with identifying your motor capabilities with more detail. Post specific questions in the Motor section of this site.

As for your cable, I would suggest evaluating the use of 4/0 welding cable.

Thanks for the info. I will look into bumping up the voltage.

Will also check on the other cable.