A123's? worth the my investment?

So when LOLcano checked into rumble at the rock the weight was 1/2 a pound over, we got ourselves down to weight by turning the armor into swiss cheese. I did not like this but could not find any other way to stop being fat. The only think i can think of now is the battery packs. We are running 2 NIMH AA battery packs 1@12v and the other @24 so a total of 30 little cells. when i checked the A123 specs they were two big to fit two packs in the bot, so if my team were to switch we could only fit one which means we would need to have two voltages coming out of the a123 pack easy enough to do BUT my budget is low so i need to make sure this will work. So heere are my questions

1. Will one 7-8Sub C cell 24v pack weigh less than the 30 little AA nimh cells? I'm pretty sure that it will but just need confirmation

2. Does it seem likely that the discharge rating is high enough to handle the amps drawn by 2 stalled banebot 36mm gearmotor and an axi 4130/20?

3. Will Splitting the pack for aquiring two different voltages ruin the cells? like somthing along the lines of uneven charging or something like that?

4. Is it true that a123 cells charge with in 15 minutes, and if so is that with any charger or for one in particular we have a triton smart charger but i dont know if that will charge the a123s quickly

Any help what so ever woould be greatly appreciated

We've used the K2's and since then A123's in 1 bot. the rest are on lipos.

I'm sure that you will save some weight over your current batteries. I believe 80 grams per cel K2's and maybe 60 and change on the A123's 2250 mah...so add it up

A123's will dump over 100 amps in bursts, so your should be fine with your 36mm bb's and axi

You can add balancing connectors, so if tapping cells for different voltages, you can later balance them.

We made custon polycarb and copper packs. We could check each cel and compare and easily replace a weak cel.
Never had to with 123's but theyh haven't seen a whole lot of action...the K2's melted a few when the students overcharged them

You can rapid charge A 123's we use the astroflight dedicated charger, but remember that battery life will be shortened.

All the specs, including weight, discharge, etc are on the net...google it

3.6 volts fully charged, so a 5 cel pack will read 18 volts, but quickly drop to around 16 under load

they can be charged in like ten minutes
this is the charger we use
triton charger

its said you dont have to balance a123s but i dont see how doing so can hurt

WHen tapping for different voltages, it might be a good idea to be able to check voltages at each cel especially if the pack doesn't charge up to snuff..jmo

Also, remember that he will be using a much larger pack than in your 5 to 6 cel bots.

The atroflight charger is great...but the last 2 we bought were Venoms for around $120 each. It will do everything from NiCads to Lipos, plus the power supply is included along with a truck load of connectors. Unfortunately, no Thunder power balancing connector, so we bought the connector and balancing board ($20) separately

We have had "taps" coming off of our batteries in three instances now, and we haven't had problems with unbalanced cell discharge. We've been using Lipos, so depending on the balancing setup, it might not work out well with A123's. Don't forget that Lipo's are a lot lighter, and cheaper..

Will, i was really leaning towards lipos but your match againt TTAT scared me off towards the Lions and NIMH'S.

jeeves_m_d wrote:

Will, i was really leaning towards lipos but your match againt TTAT scared me off towards the Lions and NIMH'S.

Some small tricks with lipos

Size your pack so as to limit current draw. This can save your esc and motor

its wasnt the batteries that burst into flames his esc caught first from the drum being stuck, the batteries lit after
tons of people use lipos without problems you just have to be a little more cautious
wills experience was really sort of a fluke instance

ok so if i did use LIpos are they legal, i know they are on bots iq but what about NRL. I ask because rumble at the rock seems to be an nrl event so we seem to competing in both leagues this year

Mr sebastioni or a name similar who runs R@R was the ref at the NRL nationals
I dont believe you can use them in the NRL anymore
Last year i think they allowed them but supposidly this year there not
BotsIQ allows them

Ok SOOO if they are not NRL legal im gonna have to go LI-ion

Nothin wrong with A123's....just a bit heavier.

Also, Li ions have some advantages over Lipos...ggogle it

ya, fluffy's flames weren't directly related to lipos.. but if RFL doesn't allow them you'd be ridiculous to use them! I agree, li-ions aren't bad! they're just a little heavier and with different strengths..