Erratic speed/low batteries - related?

I have resumed resurrecting my 2005 E4 after healing from an elbow injury. I had a code 81 and replaced the speed sensor months ago. Now i know I have a couple of weak batteries that will charge but discharge in a less than a mile to under 10 volts output. The speed display works up to about 11 mph and then no fruther ans often drops. My gps sais I am getting up to 22 MPH. My question is can low main battery voltage - just measured at 69.5 cause the speedo to act wacky or do I possibly have a defective new sensor?
A second question is I have been unable to get my delta q charger to reprogram from gel to flooded batteries and this is likely affecting the charge. If I buy batteries I will go with gel to avoid the reprogramming gremlin that has plagued me. Any recommendations?.
Thanks in advance for your suggestions.

Bite the bullet and get the new batteries and report back.

I took me 3 years before I could program a DQ


[quote=OLD HOUSEBOATER;30669]Bite the bullet and get the new batteries and report back.

I took me 3 years before I could program a DQ


You are right Rodney. Might as well eliminate a sure issue to see if it effects other things.
Deka 8G31 is the one? any other recommendations? Best pricing?

Perfect battery pick.


new gels are in and this is a very peppy gem now. But I dont know how peppy as the speedometer still does the same thing. Now i occasionally get a clunk when almost stopped like the regen brake system is a bit confused.The speedo goes to about 5-7mph and occasionally flashes a higher number for a split second, Sometimes displays code 81 on/off. Acting like a loose connection or a bad sensor (new sensor as the old one was totally bad).I have checked continuity from the motor side of the sensor plug to the controller connector and have continuity in each wire…
Any suggestions before I replace the speed sensor again?

pull the 23 pin plug and spray with Deoxit.

As long as your doing it treat all the connectors on the Power Distribution Center


check the accelerator…see pg 14 under electrical in repair manual

will do. thanks

Well the E4 is running great with new gel batteries and the defective new speed sensor replaced. The replacement sensor was wacky the entire time. Thanks to all for your help and encouragement.