Looking for a better power source

Hi, As my robot has evolved I've progressively added a few extra components to the system, although they're quite power hungry
(200-300mA). My current battery is a 12v 1.2Ah Yuasa sealed lead acid type (9.5cm x 4.5cm x 5cm).
Without going to the absolute extreme, although I am prepared to pay a fair amount more that I did for the original, what possibilities are there for a more powerful supply - Sill at 12v and as closer size as possible to my current battery.
(Max. current drain with all systems on and motors stalled is around 1.5A)
Thanks
Mark
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Check out Baran Harper for secuirty alarm system batteries. I am not sure how small they go but I buy a 12V, 7A unit sealed for about $20 Canuck
He is west of Toronto Canada
http://www.baran-harper.com /

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Motorcycle batteries might be worth considering. Especially for small, kickstart bikes, which use quite small batteries. They're pretty rugged in terms of acceleration and vibration, too. Worth phoning a supplier about, anyway.
Eg: DR-Z400 battery is 6.5Ah, 150mm x 65mm x 93mm, 2.3kg. http://www.yuasabatteries.com/battery.asp?bID ฑ60&vID944
They get a bit smaller than that, too.
-----sharks
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starting batteries aren't good with deep cycling. they are rugged though.
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dont connect in parallel two different batteries, only two same and new.
Best regards, Refik Hadzialic

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Motor cycle batteries are not sealed cells and they are liquid with a coiled vent tube. The gasses are corosive to metal and PCB parts.
Security system batteris are sealed (I think Gel cells) and emit no gasses unless overloaded or overcharged.

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Most modern motor cycle batteries (like to one I provided the link to) are sealed, gel-cell type units, for exactly that reason. There's generally a 'breather tube' on the old batteries, but it always cracks, leading to substantial chassis damage from the gases if not replaced.
(also, when the bike falls over you've got enough to worry about ...)
-----sharks
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sure
How do you determine what kind of discharge rate you can get from a battery like this? I see 85 cold cranking amps, but I'm guessing that would be very short term. It also says "Amps: 0.7". Would that be the continuous amps it can deliver?
Thanks, Bob
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That'd be it's initial charge rate, I reckon. The documents on the Yuasa site seem to agree with this. It's probably the rate that the Ah rating is measured at, too.
Bike batteries are pretty happy with large continuous currents ... I've used the 14Ah one in mine as a 100W halogen 'torch', and the voltage barely drops under that load. There's a guide to discharge rates in the "Yuasa Technical Manual" <http://www.yuasabatteries.com/pdfs/TechMan.pdf
-----sharks
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I have an idea you could try. Batteries have to be recharged after they drop below a useful potential, even though they have a lot of energy still left in them at that point. If you used a switching regulator, you could keep a usable potential on your power bus until the battery is completely discharged, squeezing quite a bit more energy out of them before they need recharging.
I expect this approach could damage certain types of batteries, however - you'd have to look up which types are suitable.
Just a thought.
Tom

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You could take 10 NiMH cells with a Sub-C size (thats a cylinder 42mm long by 22mm diameter). 1.2V per cell, 3000mAh is available, and even 3300mAh.
Solder them in the following setup against each other (top view): OOOOO OOOOO (don't forget the isolation between thecells ;-) ) And the total size will be about 11cm x 4.2cm x 4.4cm Total Rating: 12V, 3000mAh
-- Bye, Ray
http://home.hccnet.nl/raymond.van.elst / Mobile robot, walker and I-Cybie
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I'm powering my new robot with 11 AA NiMH cells, which gives me 13.2 VDC @ 1.85 Ah capacity. Very light. IMHO, NiMH is the only way to go for a small robot. I bought some nice aluminum battery holders from Digi-key (www.digikey.com). I will charge them with a simple LM317 circuit at a rate of C/10 (approx 185 mA). You can get AA NiMH cells off of ebay for about $1 apiece.
BRW
wrote:

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anyone have a lead on sprockets
i need two pair.
one side is a .590 inch dia shaft, 1 inch long. the other side is a 3/4 inch shaft, any length, but shorter is better. i'm not committed to any particular chain pitch or type. i may need as much as 2/1 ratio.
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Is there really more than one manufacturer? :o)
You need a dealer for Martin Sprocket & Gear, Inc. products
http://www.martinsprocket.com /
If you can open out a pilot bore yourself then they are dirt cheap, but do check the price of your chosen chain before buying sprockets because some chains are more reasonably priced than others.
I like chain, it may be a bit noisy but if you don't need huge rpm it will happily carry monstrous loads with low losses
best regards
Robin G Hewitt
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thanks, i'll check that out.
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