High current battery options?

[PeterW]

A query for the battery specialists?

What is the best solution for a 24V 250W application. No too expensive and not too heavy, 3-5Ah capacity. Minimal overvoltage and minimal sag during usage. From what I read, low capacity SLA's can't normally give that kind of current continuously.How easy would it be to build and charge a big stack of NiMH.

Guess this is one of those 'holy grail' questions!

Cheers for helping

PeterW

 

[CNC Dan]

some LSAs are made for high discharge currents.

Check with batterystation.com. I think kevin can get LSAs that are used in those portable jumpstart packs.

 

[Ginseng]

Your form factor and specific requirements will determine what one can recommend. Can you be more specific? For example, I can get 20 x 4Ah 1/2D cells into a Dorcy handled spotlight to power a 64655HLX or 21 x 1.8Ah 4/5A cells in a Mag 6D. You could also double up the 3AH SLA in the Vector 2MCP spot for 24V. If you cannot be more specific, then at least indicate your desired balance point between size and capacity. Perhaps if you suggest a host then a more useful recommendation can be made.

Wilkey

 

[PeLu]

10A ask for a high drain cell, so SubC cells will be the best option. You will get more out of a 3.5Ah SubC cell than from a 7Ah SLA in this case (just as an example).
Get two 12V RC racing packs.

 

[Ginseng]

Where do you find 3.5Ah sub-Cs? The 3.3Ah GP3300's are the highest I've seen so far.

Wilkey

 

[4sevens]

Call me crazy but I'm a fan of the Rayovac 15 minute AA and AAA's.
(800mah and 2000mah)
Just to charge them, the charger puts 7.5A into them.
Since that much current goes through them charging, then they
should be able to discharge at least as much right?
They much be design for this kind of load. Also, they have to
design it with low internal resistance too.

Shorting the AA through a DMM gives 7.5A.
Shorting the AAA through a DMM gives 7A.

I did a little experiment.
With two DMM at the contacts, one measuring V, the
other I.
I have one AAA here when short through a DMM produces 7A for 30 seconds
and then stays at around 6.5A and 1.18V for about 4 minutes.
It hits 6.0A at 5.00 minutes into the discharge (1.028v)
It hits 5.0A at 8.34 minutes into the discharge (8.44v)
4A 9.16min 0.671v
3A 9.37min 0.501v
2A 9.56min 0.323v
1A 10.35min 0.163v

Hows that from one AAA /ubbthreads/images/graemlins/smile.gif
David

Maybe a graph forthcoming.

 

[ScubaFan]

I'm sure I saw some matched Sanyo 3600mAH subC batteries at the local RC stores. However, some of my friends said that they are not that much better than matched 3300mAH.

 

[PeLu]

The GP 3.3Ah usually can have about 3.5Ah. Anyway, look what your local RC shop has to offer or into ebay.

I have quite good resulty with GP cells for rotary hammers (a pretty high current application).