I am wanting to build an electric scooter. I hope I can draw 10 A without damaging the battery. Sears has an 80 AH battery for about $160 but very little information.
I hope someone more familiar with deep cycle batteries can spend a moment to help me out.
thanks in advance Robert
10A drawn from an 80AH deep cycle battery will be fine. It won't give you 10 hours running though. As a general rule, the shorter the discharge time the less total energy you get out of it.
That's only 120W though - your scooter doesn't sound as if it is going to scoot.
| I am wanting to build an electric scooter. I hope I can draw 10 A without | damaging the battery. Sears has an 80 AH battery for about $160 but very | little information.
It should would be nice if they would specify the maximum safe discharge rates on all batteries.
Check manufacturer's website for specs. Figures such as the one you're after have dependances such as the time you draw the current. An 80Ah battery might safely provide 800A for a second or two, but not for a minute or two.
On 13 Oct 2006 20:44:42 GMT Andrew Gabriel wrote: | In article , | snipped-for-privacy@ipal.net writes: |> On Thu, 12 Oct 2006 21:54:58 -0600 Robert Miller wrote: |> |>| I am wanting to build an electric scooter. I hope I can draw 10 A without |>| damaging the battery. Sears has an 80 AH battery for about $160 but very |>| little information. |> |> It should would be nice if they would specify the maximum safe discharge |> rates on all batteries. | | Check manufacturer's website for specs. Figures such as the one | you're after have dependances such as the time you draw the current. | An 80Ah battery might safely provide 800A for a second or two, but | not for a minute or two.
I'd like to know what is the safe current I can draw from one of those big deep cycle marine batteries and not damage the battery in any way. This would be for a time frame as long as the battery can provide it, however long that happens to be.
Charging current and voltage would also be nice to know.
Companies like Sears seem to expect all their sales to be replacements for equipment that has already specified a particular battery, and hence they have no "need" to provide technical data.
It's kind of like the specifications for capacitors that I raised a year or so ago ... I can see farads and max voltage, but what about the max amperage? E.g. how fast can I charge and discharge them safely? What figures will let me calculate the heat rise internally, and what is the maximum heat they can handle?
On Fri, 13 Oct 2006 08:57:32 +0100, Palindr?me Gave us:
Nope... Even the little foot scooters have 700 Watt motors on them. (some)
What the average user does is to monitor the battery voltage and disconnect the load at a preset level. I.e say 11v. Then if your use is light the battery charge will last longer than if the draw is high. Rule of thumb for long battery life would be never to discharge it below 80%. There are kits and ready made devices available to do just that. The state of charge is reflected by the voltage at the terminals which is what these devices do. If battery life is not a priority then deep cycle batteries can be run down to
10.5v to provide maximum usage at the cost of replacing it more frequently.| What the average user does is to monitor the battery voltage and disconnect | the load at a preset level. I.e say 11v. Then if your use is light the | battery charge will last longer than if the draw is high. Rule of thumb for | long battery life would be never to discharge it below 80%. There are kits | and ready made devices available to do just that. The state of charge is | reflected by the voltage at the terminals which is what these devices do. If | battery life is not a priority then deep cycle batteries can be run down to | 10.5v to provide maximum usage at the cost of replacing it more frequently.
I'm asking the question at a design level. I want to be able to draw a specific amount of current. How many batteries to I need to parallel?
Suppose I want to make a battery power DC welder using several batteries, each having its own current limiting resistor, with enough of these wired in parallel to supply sufficient current. I want to make the system so robust it cannot be destroyed by a solid fault current (except maybe at the point where the fault exists). I can figure the rating I need for the resistor (bank) once I know the current I'll be expecting from each battery. But I don't want the battery to overheat from too high a current. So I need to know what is the safe maximum current from each battery to choose the resistors (maybe a light bulb bank).
Suppose the answer for some battery is 60 amps. I could put in 12 60 watt bulbs 12 volt in parallel as the current limit for each battery. Then if I want a 300 amp capacity, wire 5 of these setups in parallel.
At the design level, I would want to choose batteries that could meet the load without the need to be paralleled.
If they did have to be, I would expect that identical batteries, from the same manufacturer and having had the same history, would share the load equally enough not to need any individual current equalisation measure. But would ask the manufacturer - they are the experts on their batteries - especially for unusual discharge curves.
If I did have to parallel where I needed to be able to control load share (say between dissimilar batteries or supplies), I would use active switches to vary the average current from each supply - using an inductor to limit the peak current.
At low currents, resistors can be used to effectively turn constant voltage sources into constant current ones, which can then be summed by paralleling them, but this tends to be extremely power-inefficient. Series-connecting constant voltage sources automatically equalises the current drawn from each battery - which is why series-connecting large AH cells is better than parallel connecting large voltage batteries..
On Sat, 14 Oct 2006 19:14:19 +0100 Palindr?me wrote: | snipped-for-privacy@ipal.net wrote: |> On Sat, 14 Oct 2006 16:12:53 +0800 Rheilly Phoull wrote: |> |> | What the average user does is to monitor the battery voltage and disconnect |> | the load at a preset level. I.e say 11v. Then if your use is light the |> | battery charge will last longer than if the draw is high. Rule of thumb for |> | long battery life would be never to discharge it below 80%. There are kits |> | and ready made devices available to do just that. The state of charge is |> | reflected by the voltage at the terminals which is what these devices do. If |> | battery life is not a priority then deep cycle batteries can be run down to |> | 10.5v to provide maximum usage at the cost of replacing it more frequently. |> |> I'm asking the question at a design level. I want to be able to draw a |> specific amount of current. How many batteries to I need to parallel? |> |> Suppose I want to make a battery power DC welder using several batteries, |> each having its own current limiting resistor, with enough of these wired |> in parallel to supply sufficient current. I want to make the system so |> robust it cannot be destroyed by a solid fault current (except maybe at |> the point where the fault exists). I can figure the rating I need for the |> resistor (bank) once I know the current I'll be expecting from each battery. |> But I don't want the battery to overheat from too high a current. So I |> need to know what is the safe maximum current from each battery to choose |> the resistors (maybe a light bulb bank). |> |> Suppose the answer for some battery is 60 amps. I could put in 12 60 watt |> bulbs 12 volt in parallel as the current limit for each battery. Then if |> I want a 300 amp capacity, wire 5 of these setups in parallel. |> | | At the design level, I would want to choose batteries that could meet | the load without the need to be paralleled.
I would up to a point. I'd rather limit the size of the individual ones to the sizes I can lift. I don't want to have to buy a forklift.
| If they did have to be, I would expect that identical batteries, from | the same manufacturer and having had the same history, would share the | load equally enough not to need any individual current equalisation | measure. But would ask the manufacturer - they are the experts on their | batteries - especially for unusual discharge curves.
I would expect the ones that are weaker to have a lower voltage and this push fewer amps through the current limiting resistance. That seems like it would not be a problem.
| If I did have to parallel where I needed to be able to control load | share (say between dissimilar batteries or supplies), I would use active | switches to vary the average current from each supply - using an | inductor to limit the peak current.
I will assume basically identical batteries, all bought new at the same time.
| At low currents, resistors can be used to effectively turn constant | voltage sources into constant current ones, which can then be summed by | paralleling them, but this tends to be extremely power-inefficient. | Series-connecting constant voltage sources automatically equalises the | current drawn from each battery - which is why series-connecting large | AH cells is better than parallel connecting large voltage batteries..
But I want the higher current, not the voltage.
I have thought about what it might take to make current limitation work on DC. Obviously the method most often employed with AC, inductors, is not going to work with DC. I have thought about solid state pulse width switching feeding a capacitor bank is one option. But I'm still faced with potentially high current issues discharging the capacitors if there is a solid short circuit, if they were at full charge. I suspect using smaller capacitance and higher switching frequency is the answer to that, as the short circuit current would then be very brief as the capacitors would be discharged very quickly. And I would need to know things about the capacitors that is not regular knowledge, like their long term and short term safe current rates (charging and discharging).
Have a ever tried to short circuit discharge a big power supply filtering capacitor (instead of a resistor)?
On 14 Oct 2006 22:50:48 GMT, snipped-for-privacy@ipal.net Gave us:
A good study on batteries, and interconnections, etc. are the robot wars college student get involved with.
On Sun, 15 Oct 2006 13:38:45 -0700 JoeBloe wrote: | On 14 Oct 2006 22:50:48 GMT, snipped-for-privacy@ipal.net Gave us: | |>Have a ever | | | A good study on batteries, and interconnections, etc. are the robot | wars college student get involved with.
Ah, now there's an idea. I can vaporize the enemy robot with my 200,000 amp arc.
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