Printable View
I'm looking for some weight details of SLA batteries. My drivetrain is 24V so I'm looking to make up the voltage with a pair of SLA's at 12 V each. Does anyone have any big SLA's of this voltage they could give me a rough weight on?
I've read somewhere that there's a minimum weight for heavies which I'm struggling with a bit, so filling it full of batteries should help haha. Also, if anyone knows the weight I'd appreciate details on that too lol.
I think 2 hawkers are around 10kg the pair. You are better to run a paid of 12v batteries to give the 24v. If you are looking to add weight just add tons of packs, a bot with 4 SLA's (2 for each motor) would run for a pretty long time
That's awesome thanks. Do you know if they're literally sealed for life, if I need to fill them up with water, if I'm still allowed to use these batteries and where I can get a charger from them? Have had the mad idea of using a car battery charger to charge them?
I've had half a heavy built for 12 months but couldn't work out how to mount half of it and now it's clicked, so am frantically get finished for the Northern Tour later in the year lol.
That's what I used before and worked fine. They are sealed units with acid (Hence the name lead ACID battery)
There is no rules that they you can't use them, not commonly used now as they are quite old tech and not the most efficient in power delivery but still make a HW run
Hi
5.72Kg each I just weighed one, so 11.44Kg. I have only just stopped using SLA batteries in my robots. They proved reliable and cheep, I used an ordinary car battery charger to recharge at shows for years they worked fine. these are the 16Ah type.
That's great thank you! Will go and have a look at what maplin have on the way home tonight :D
Don't bother with maplins. Get them off the internet. Look at component shop or something.
Just had a look at component shop and they do 20Ahr 12V batteries and £10 chargers! Gonna get some of them ordered when I get home! Can you lie batteries on their side in the robot, I presume you can?
Does any one know the minimum weight for a heavy? Is it 60kg?
Woha, some pointers.
For the robots we need Sealed Lead Acid batteries, but not with liquid filling. Gelcells (were the acid is an very thick ooze) or AGM Cells (glassmatt fiber as retainer for the acid) are mandatory, since the start of Robot Wars.Quote:
Do you know if they're literally sealed for life, if I need to fill them up with water
7.8
The following battery types can be used without any specific precautions although care must be taken when
any battery particularly during charging:
Pb (Sealed Lead Acid, SLA), non-spillable gel type. (e.g. Yuasa, Hawker)
Imagine a liquid acid battery springing a leak during a fight. I don't want to clean up that mess.
Weight of SLA batteries. A 7 to 9 ah SLA battery (PBQ was our favorite brand, cheap and dependable) weights around 2.8 kg.
Hawkers come in so many flavers it's difficult to give a weight, but the cheaper genesis (rebranded Yuasha) sets are about the same. The High End pure lead technologies are a tad lighter for watts stored. But the pricetag gets high fast.
Weight of a heavyweight
2.1 Weight classification
Heavyweight: 55kgs to 100kgs [220lbs]
Ok Mario that's great. So to sum up, batteries must be gel cell to prevent leaks and general all round catastrophe, and I'm ok as long as I can be 55kg - 60kg + :-)
I won't let anything less than ~80kg in my arena with a big flipper and then I would be watching carefully.
Yes please let us know what you are getting as the batteries have to comply with the rules. the spec should say they are the gel type.
OK I will post before I buy anything, it will be a few weeks off. And point taken Alan, I will rethink and get it to 100kg ish. How do people weigh their heavies?
on your bathroom scales, or on the kitchen scales bit at a time, or at an event you can still compete if its a bit over in w/b anyway.
a quick google search
http://www.ebay.co.uk/itm/CSB-EVX-12...ht_3540wt_1153
That's great thanks terry. How many amp-hours do people get through in a fight? I only have 24V 10A wheel chair motors so can't see me using that much lol.
Typically 2.5 - 3Ah per fight, but that is with Bosch 750s
Oh ok that's cool. So if someone had a couple of 22ahr batteries cabled to give 44ahr in theory you'd get through a whole even without recharging?
Has anyone tried something like 5000ahr NIMH packs in a heavy?
You will find that current delivery is more the issue, rather than the capacity, hence the reason for paralleling up packs.
Mike used NiMh packs in Pressure, they are not quite as good as Nicads in terms of current delivery (in general). Stick with SLAs to start with unless you feel confident (and have the money) for A123 or Lipo batteries. Also think you will struggle to find 44Ah SLAs. I would suggest buying two sets of smaller 10-16Ah batteries, then put all of them in the robot to boost the weight.
3ah in 3 minutes means a continue draw of 60amps. But fights ain't a continous draw, it's peakload after peakload.
And sla's are very inefficient in that kind application.
That's why a robot that blows up 9ah sla batteries in about every fight can perfectly work fine on 5000mAh 30c LiPo.
Also the reason why "historical" 12 to 17ah sla of normal quality was used in heavies on tv.
I know where my money goes to.
Ok I understand. I knew you all would know if it was doable, and I understand now why you all have a load of smaller packs making up the voltage as opposed to a single huge battery.
I had wondered this, in particular with John Bell's Titan. When we were fighting at Doncaster we were wandering about looking at the heavies, and Titan has rows and rows of tiny SLA's along the back corners. I now can guess that this is because of the huge LEM?PERM? he has on the axe and the amount of current it must suddenly pull from the batteries upon firing.
The bank of smaller batteries gives more "surface area" to pull current from.
This is why I like being on here, I have a read through most days but there's so much collective knowledge it's frightening. I've literally built robots so far based on asking questions like this.
Titan uses LiFEPO4 packs, since John moved away from Nicads. Bullfrog also uses those packs, and we on average get 2Ah to 2,5Ah tops out of them in one fight. Recharging takes less than 15 minutes, so last event we did 2 fights per show with ease.
Little thing about titan, only 2 of those packs are for drive, the rest is the weapon :)
More packs for the weapon now, it's up to 40v
Ok following on from this I'm ready to get cooking with wiring!
Are these suitable
http://www.componentshop.co.uk/12v-9...d-battery.html
And will this charger charge them ok?
http://www.componentshop.co.uk/4000m...ries-3313.html
They are a suitable type, but you will probably struggle to get any major current draw out of them, might be pushing it close on capacity as well. I would go more for this size http://www.componentshop.co.uk/12v-2...d-battery.html that's the most common size used.
That's fab thanks, gonna order them now. Does the charger look alright? Obviously I spose the beefier the charger the faster it'll charge.
That charger says it will take 12 hours to charge the batteries Alan suggests.
I assume you will get 2 chargers?
Just ordered the 9ahr batteries and charger as in the original post. I'm only running wheel chair motors so think I'll be alright with those. If they drain really quick I will buy bigger packs, but only have £50 on batteries and charger at the minute.
It was mostly just to know if they were the right chemistry. If I move on to Mags or something similar in the future I'm well aware I will need more battery capacity.
no you wont need more capacity, if you upgrade to mags then you will need batteries that will be able to charge faster and deliver a higher current when required, a123's or lipo would be best, nicd still available and cheaper but most are moving away from that chemistry now. i run 2 mags and have 30v with 9.2 amps and have between 40 - 60% remaining after fights.
Ok that's great. Going through the specs of motors and pilfering details of people's heavy specs, I'd wondered if I'd get away with it with just a lowly pair of 10A wheelchair motors lol. The theory says that with my 9.something AHR batteries I'd be able to run for an hour or so. I know that's never gonna happen in reality but the numbers feel like they give me breathing room.
You will find with the SLA type of batteries the amp/hour number doesn't strictly apply, I ran SLA 16Ah with Bosch 750w motors and found the batteries were going flat in the last minute of a fight. if the batteries were left to "rest" they would recover and when charging the charger would only put in about 6 Amp/hour. It's to do with this type of battery chemistry.
In your case I doubt the motors are more than 250w so the batteries you have ordered should be fine. my advice is to make sure the gear ratio is quite low. so you have the chance of pushing other robots about the arena (just not that fast) I think it's good to try to make a budget heavy at the beginning that is what Saint was!
My advice if it is not going to have an active weapon, go for something the crowed would love, give it a face, a character or some other facet that would connect with the audience Like Kettlebot!
Looking forward to see what you come up with. :)
Thank you for the words of encouragement. The robot is just a basic cheap heavy just for some fun.
The robot is like a thwack bot but not to just sit and spin, to sort of drive all over and bounce about a bit like Stinger used to. We've gone with this as we know we don't really need any shove for it and are likely to get thrown all over. I got a bit bored with the feathers so thought I'd have a go at a heavy.
The wheel chair motors are about 21:1. I know this as I spun the motor and counted the times till the wheel did one full revolution haha I'm not very scientific! Before I dismantled the wheel chair I gave it some stick up and down the drive way and was really quite impressed at the torque they had flinging me about lol. I've taken the brakes out, regreased everything and got new inner tubes and tyres from the mobility shop so they've had an informal refurb :)
This is a rough sketch I did to show John n Dad the basics in my head lol.
http://i174.photobucket.com/albums/w...pscf8374c8.jpg