Battery series/parallel question

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chris1968
Posts: 5
Joined: Wed Aug 29, 2012 8:59 pm

Battery series/parallel question

Postby chris1968 » Fri Sep 07, 2012 8:14 pm

Trying to improve range on 48v scooter.

The controller and Hub motor are rated at 48v, been told that they can take the extra voltage if over volted with another battery of the same type in series. This will improve performance I believe.

Is it possible to keep the 4 12v 24ah batteries in series, and connect one additional battery of the same type in parallel to one of the batteries to keep the voltage at 48v but increase the AH?.

Really sorry if this is a dumb question.

Thanks in advance

Chris

jonathan jewkes
Posts: 67
Joined: Sun Jul 15, 2007 8:14 pm
Location: Bristol

Re: Battery series/parallel question

Postby jonathan jewkes » Sat Sep 08, 2012 6:51 pm

Adding one battery in parallel to only one of the existing four will not help. The remaining 3 will run flat almost as quickly as they do at present. True, the parallel pair will by then only be half discharged but they won't be able to push a useful amount of current through the 3 flat batteries (or if they do, you could be at risk of cell reversal, which will damage them).

Adding one battery in series (to make 60v) would improve performance (ie speed and acceleration). But if you went easy on the throttle (or if possible reduced the controller max current setting) to keep performance at its original level, then you should improve range. This is because with the higher voltage you need less current to get the same power, and so your 24Ah will last longer. You will need to check that both your motor and your controller can cope with this higher voltage.

You could improve range by replacing all 4 batteries with ones of greater Ah. But they would be larger, so may not physically fit onto your scooter.

Assuming that your batteries are lead-acid, then really the best way to improve range would be to replace them with Lithium Ion ones. But that will cost ££. There are other posts on this forum by people who have done this successfully.
Jonathan Jewkes
Daily EV user for 10years - an enthusiast and also a realist

chris1968
Posts: 5
Joined: Wed Aug 29, 2012 8:59 pm

Re: Battery series/parallel question

Postby chris1968 » Sun Sep 09, 2012 10:35 am

Thanks for the reply.

Added a spare 5th battery wired in series yesterday, it did improve performance, not yet tested for range, but as you say gentle on the throttle will help.

Just trying to get more out of it for as little as possible at this moment in time, might aswell use the existing batteries until they die.

Ultimately lithium would be the answer, I was just woundering if the AH could have been improved by the parallellel addition, new to this, thanks for your explanation, helps with the learning curve.

Chris

chris1968
Posts: 5
Joined: Wed Aug 29, 2012 8:59 pm

Re: Battery series/parallel question

Postby chris1968 » Sun Sep 16, 2012 10:50 pm

Hi

Just for info really. Test rode with extra battery fitted, now 60v, 22 mile test run, much better performance, mixed terrain, a few hills, a few down hills and a lot of straights thrown in.

Performance started to drop off round about the 17 mile mark, slowing on hills but still ok on straights. 16 and a bit stone (solid muscle)test pilot, a lighter pilot would have even better increased performance.

This was the indicator that the batteries where probably at their discharge limit as the battery meter now unreliable as for 48v system, so still showing full due to the extra voltage from the 5th battery.

Going to keep it at 60v, got a new 60v charger on way, tested a -15v zener diode wired before the battery meter to reduce what the battery meter sees by 15v, full charge showing 64v then showing 50v through zener, hopefully this will enable battery meter to be usable again with true-ish voltage, but not yet tested this fully yet.

Big thanks to the forum, big thanks to zenid and his scoota blog, this project was just the start of the learning curve for future projects.

Chris

chris1968
Posts: 5
Joined: Wed Aug 29, 2012 8:59 pm

Re: Battery series/parallel question

Postby chris1968 » Sat Sep 22, 2012 11:03 pm

The zener didn't quite work out.

When the throttle was applied, lights turned on or indicators for example, any extra load applied saw the battery meter LED's dip to half lights, sometimes right down to the red.

OK, this may be down to sizing of the zener and a smaller zener may work better, the performance was still the same and the lights dipping has no effect on this but, it would be nice to have a battery level meter that works. Will prob try the lead from the 4th battery next.

Also with the new 60v battery charger, which is now charging the batteries up to nearly 70v, which is above the controllers threshold which means lights need to be left on for 20 mins before the bike will work is a bit of a pain but without replacing the controller is something I'll have to live with I guess.


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