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Old 10-25-07, 04:35 PM   #1
thebeatcatcher
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opinions on my battery/bulb selection

I have an old vista lite and the SLA battery isn't cutting it anymore. I am thinking about replacing the bulb with a 6V 10W spot halogen powered by this new battery.

I figured about 1.5 hours of runtime, and I need at least 1hr.

Did I do the math correctly? Is this an adequate battery choice?
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Old 10-25-07, 08:48 PM   #2
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You may have done the math correctly, but the energy rating is dependent on the amp draw. I have a 2800 battery pack, if I recall correctly, and it lasts for ~90 minutes and then dies QUICKLY, probably not the best thing for the battery...

If you only need one hour you may be OK, but I would figure on about 3000 mAh or so to maximize battery life... I like the 18500 series Lithium batteries, or some of the polymer packs.
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Old 10-25-07, 10:28 PM   #3
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Originally Posted by thebeatcatcher View Post
I have an old vista lite and the SLA battery isn't cutting it anymore. I am thinking about replacing the bulb with a 6V 10W spot halogen powered by this new battery.

I figured about 1.5 hours of runtime, and I need at least 1hr.

Did I do the math correctly? Is this an adequate battery choice?
Your math is almost right. You do need to take into account the voltage of the battery to get the current draw. For your light, that would be

10W/7.2V = 1.38 amps

For a 2.2 Ah battery that should give you 1.6 hrs, theoretically. However that's the max you can get. YMWV. But I'd suggest that you spend $3 more and get this battery. The 3.3 Ah rating will give you 2.39 hours. You can always change the connector.

If you really want light, get the 3.3 Ah battery and a 15W bulb. Same run time as the 2.2 Ah battery but a whole bunch more light.
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Old 10-26-07, 10:42 AM   #4
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Thanks for the info, I'll definitely go with the "bigger" battery.

Question about jacks/plugs/connectors. I will need to change the jack on the cord that plugs into the battery pack, with which I am comfortable. However, do I need to worry about polarity? Are halogen bulbs polarized or can I connect either wire coming from the bulb to the red or black? (The polarity IS important for the battery/charger connection correct?)

Thanks!
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Old 10-26-07, 12:05 PM   #5
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Thanks for the info, I'll definitely go with the "bigger" battery.

Question about jacks/plugs/connectors. I will need to change the jack on the cord that plugs into the battery pack, with which I am comfortable. However, do I need to worry about polarity? Are halogen bulbs polarized or can I connect either wire coming from the bulb to the red or black? (The polarity IS important for the battery/charger connection correct?)

Thanks!
Your leads to the light are probably polarized too...most are. It shouldn't make a difference on the lamp end. You are right about the charger connection. A local hobby shop that carries RC cars should have the connectors. Or look for Dean's Ultra Connector or Anderson Power Poles.
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Old 10-28-07, 04:48 PM   #6
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charger

Here is a pic of the old charger for the old SLA battery:


If I were to get this battery (thanks for the recommendation) could I use the old charger? The output voltage seems like it matches (7.5V), but it also says 300mA on the output. So does that mean it would take 11hrs to charge a 3300mAh battery?!?

Just curious to see if I can use this transformer/charger w/o having to buy a new one.

(also, in reference to my earlier question about polarity, I just saw the diagram on the transformer, now I know for sure which wire is which)
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Old 10-28-07, 09:14 PM   #7
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Originally Posted by thebeatcatcher View Post
Here is a pic of the old charger for the old SLA battery:


If I were to get this battery (thanks for the recommendation) could I use the old charger? The output voltage seems like it matches (7.5V), but it also says 300mA on the output. So does that mean it would take 11hrs to charge a 3300mAh battery?!?

Just curious to see if I can use this transformer/charger w/o having to buy a new one.

(also, in reference to my earlier question about polarity, I just saw the diagram on the transformer, now I know for sure which wire is which)
For a Ni chemistry battery, it's better to have a charger that will measure the change in voltage and the change in temperature. NiMH batteries spike in temp at the end of charge. That can quickly kill the battery. This charger would fill the need.
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Old 10-29-07, 05:09 PM   #8
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For a Ni chemistry battery, it's better to have a charger that will measure the change in voltage and the change in temperature. NiMH batteries spike in temp at the end of charge. That can quickly kill the battery. This charger would fill the need.
cool, thanks.
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