Battery can't go the distance? :P

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Rorzzer
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Battery can't go the distance? :P

hey all, im pretty new to the whole forum thing so feel free to laugh at my mistakes.

my problem: i have a 500W 36V brushless motor and the original controller i was supplied with (they came in a kit). and i have just purchased (about 3 months ago) 3x CSB 12V 15AH "Electric Vehicle Model" batteries (obviously equalling 36V), i am using the charger i had with my previous batteries that were 12AH (all other specs the same). ok so details established, my batteries are lucky to last an hour and a half. when charged they are up around 39V and when under load the voltage drop is next to nothing (like from 39.4V to 39.2V), so internal resistance isnt a problem (initially) and they seem to be charging just fine, i cant understand where my problem is here and i think i might cry :P so much money spent for more run time and i have less :(.

someone please help with any information you can provide at all. thanks in advance.

mf70
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Re: Battery can't go the distance? :P

So, how much run time were you getting from the 12AH batteries?

Actually, changing from 12AH to 15AH might not make very much difference. Enabled by larger batteries, It could be easy to run more at full throttle, putting you deeper into Peukert's grip.

That 12AH (or 15AH) was measured at a "20 hour" rate, with about 25 Watts consumption for 20 hours.

Mark

Rorzzer
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Re: Battery can't go the distance? :P

well the old 12AH batteries i had weren't particularly good quality and weren't AGM and i would get at least 2-3 hours of use out of it on an electric bike, i now have the kit on a drift trike (which is lighter than the original bike and would had less friction overall) and with these new CSB AGM batteries i get just over an hour. thanks heaps for the quick reply by the way. if you need any more information or number just ask.

mf70
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Re: Battery can't go the distance? :P

You can set up your own capacity test with a Kill-a-Watt power meter, a 110V inverter, and a test load such as a light bulb. I posted a link expanding on this. If you set it up for about 250 Watts, it would approximate the average usage of your 500 W motor.

Mark

Rorzzer
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Re: Battery can't go the distance? :P

hi sorry to be a pain but in Australia everything is 220-240V, and i have a 350W 220V inverter if you could please rephrase your reply with these values that would be amazing thanks.

mf70
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Re: Battery can't go the distance? :P

Um, it doesn't make any difference. You have four 12V batteries, right? The inverter uses that 12V input to generate your line voltage. There are some extra loads imposed by running the inverter itself, but there are also some significant advantages: chiefly, that they will shut off at a consistent voltage, protecting the battery. Even without a Kill-a-Watt, by timing the run time, you will learn the capacity of the system at that drain rate.

If you draw 250Watts from your inverter, you will be drawing about the average load of your motor. On a rethink, that would be true if you made all four batteries in parallel into the inverter. That would give you a quick overview of the battery health.

Of more concern, however, is the individual battery health. To test each individual battery, I would run ~ 1/4 of the load, or 60Watts off the inverter, making separate capacity measurements of each battery. You may very well have one dud battery. In a series string, a single dud battery will bring down the pack.

Mark

Rorzzer
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Re: Battery can't go the distance? :P

i have 3 batteries and you mentioned running them in parallel, how is that possible without shorting them out?

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