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charging SLAs
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timmeh
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Joined: 20 Jul 2004
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Yes the fan was working.

And i could only hold my thumb on it for 2-3 second before i had to take it off.

I solved the problem bye sitting a big 24v mainframe comp fan behind the triton blowing air onto the heatsinks on the back which cooled it down to allmost no heat at all in about 10 seconds Very Happy

So should my triton be getting that hot?
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Post Sun Nov 28, 2004 12:48 pm 
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Glen
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when i borrowed nicks it got damn hot, so i had to stick a 90mm fan behind it so its not unusual.
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Post Sun Nov 28, 2004 12:56 pm 
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Glen
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hey andrew, just checking this is all right before i annihilate my batteries doing something wrong lol

i put a high current charger on the slas until the voltage rises up past 13.9v and then put a regulated charger on it until its finished (cant remember how to tell when its finished :s is it when the voltage drops off again?)

just about to dig out my arlec 4 amper charger.
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Post Wed Dec 22, 2004 7:43 pm 
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Knightrous
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A regulated charger will generally tell you when it is fully charged. We generally just monitor the voltage when using an unregulated charger and just let it get to 14v. Andrew will be home in a few days and will be able to correct anything I've stated incorrectly
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Post Wed Dec 22, 2004 7:57 pm 
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Glen
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i just threw a dodgy SLA on the charger ive got (2.5amp arlec). the starting voltage was 11.7 and when i charged it, it went up to 13.7v, then dropped to 13.4v and quickly rose way up to 14.9v when i shut the charger off because the battery was making some nasty gurgling noises, this happened in about 15 minutes total.

im guessing this isnt whats supposed to happen...?
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Post Fri Dec 24, 2004 8:47 pm 
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Knightrous
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When it starts gurgling, thats your gell starting to gas. turn it off just as it starts this, you might have to monitor the batteries like a hawk.

Give the battery a run in the robot and see how it goes
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Post Fri Dec 24, 2004 8:58 pm 
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marto
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The voltage of the cells usually drops after the battery is fully charged so that would explain why it got to 13.7 and then fell before rising quickly to 14.9. You can buy a regulator for unregulated charger which shuts off the charger when it gets to 13.8. I think jaycar have one no idea how much it is thou.
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Post Fri Dec 24, 2004 9:32 pm 
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andrew



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Location: Castle Hill, Sydney. N.S.W


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i tried that. the kit that jaycar sell for unregulatred chargers dont work and it wasnt me doing anything wrong or whatever,. my grandad helped me build it and he is a retired electrical guru sorta fella.

just not good for what we need.
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Post Fri Dec 24, 2004 10:13 pm 
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Totaly_Recycled
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Hi Glen

Dont let the charger go over 13.8 to 14 volts for longer than a minute or so ..definatly dont leave it on until the battery is gurgling ..lol unles the battery was an old one that wouldnt charge on a regulated charger

Some times a quick gurgle can fix them short term ...also listen to all the advice about charginjg batteries properly for long battery life ....Hitting them up with high current is ok to get a good quick charge but will eventualy shorten the batteries over all life span consideraly.

But i consider that if i get at least a few events out of a $12 sla its still cheaper and less fidly mucking about with nicads and associated chargers ect..
So far we have had a full year out of the 4 origional Doss 7 amp sla's that Jason got for us at the first Robo wars last year and they have been charged and discharged many more times than i ever expected them to last .

Apart from driveing our robots they get used daily extensivily on air compresors mower starter motors in spot lights and for charging remote control nicad packs as well ..so they dont sit on the shelf for long ..

Post Sun Dec 26, 2004 7:03 am 
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colin



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fyi,

Jaycar will be stocking lead-acid chargers. From memory it was hard to find a high current charger at a reasonable price.
three models:
Switchmode Dual Stage Lead-Acid Battery Charger - 12V @ 6A $80
Switchmode Dual Stage Lead-Acid Battery Charger - 12V @ 12A $100
Switchmode Dual Stage Lead-Acid Battery Charger - 24V @ 6A $100

Post Sun Mar 06, 2005 6:52 pm 
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Spockie-Tech
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Also, for anyone looking for a high current supply for their NiCd chargers, in a recent Jaycar Techstore Mailout, they have some mega-bargains on rebuilt high power 12v switchmode supplies..

8.5 amps - $25 - http://www1.jaycar.com.au/productView.asp?ID=JM3121
12.5 amps - $38 - http://www1.jaycar.com.au/productView.asp?ID=JM3110

and a massive 18.5 amps - $55 - this one is in the lfyer, but the weblink doesnt work, so you might have to call the techstore (online shop). Its part number is JM3118

Note these are *12v* supplies. Not 13.8v, so they are not suitable for charging SLA's, but will run a Triton or GWS/Omni/Whatever fine.
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Post Mon Mar 07, 2005 12:18 am 
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Philip
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Is it a good idea to parallel a SLA onto a car battery to charge? Does the engine need to be off to prevent AC noise or would the car's wet lead acid be able to sufficiently filter the voltage? I am thinking of using an AGM battery.

I have a feeling that Brett answered this question before but I have not been able to find the reasponse. Maybe it was on the ABBL forum.
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Post Mon Apr 25, 2005 9:20 am 
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Totaly_Recycled
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Philip dont directly conect a flat sla on to your car battery with out some sort of currrent reduceing resistor in series ...the sudden inrush of several hundred amps of current may cause it to explode..if you want to charge it this way i would advise putting a 20 to 50 watt light bulb in the charge lead until the sla gets up to over 12 volts before conecting it directly to the cars charging circute . The light will glow bright as the sla is takeing the charge and will go out as the voltage in the cells equalise .This is a very rough way of doing it .I would advise geting a good sla charger or modifying a normal car charger .i take the bigest high voltage (40 to 60 volts capactors ) I can find in old computer power sulpies and put them in the cheap charger s this at least filterers a lot of the a/c spikes this wont regulate them though so if you dont have one with voltage control just monitor the charge voltage reguarly with a meter .and take them off at 13.8 volts

Post Mon Apr 25, 2005 9:55 am 
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Spockie-Tech
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Good Advice from Andrew there.. Smile

Keeping an eye on the end-of-charge voltage is very important as he mentioned, because most car alternators are set to put out 14.2 - 14.4v which is fine for a wet-cell, but will cause an SLA to gas when its full, which is a bad thing, since you cant just top up the electrolyte like a wet-cell..

Doing it with the car off will put *some* charge into the SLA, and it will be a nice smooth voltage so its good in that respect, but the car battery voltage will probably only sit around 12.5 - 12.8 volts under load, so you wont get a full charge into your SLA with the car off.. and you will get too much if you dont monitor it with the car running..

Bottom line is, if its a good quality SLA, charging it from your car alternator is a last-resort thing to do if you're desperate to get some power into it in a hurry.. but If your SLA having a long happy life is important to you, its not something I'd reccomend doing.. unless its a cheapy you dont care about.
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Post Mon Apr 25, 2005 10:15 am 
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Spockie-Tech
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While wiring up some battery charger leads, I thought I'd suggest another use for an idea andrew mentioned a post or so back.. a cheap SLA "Charging complete" indicator.

At the last event, a couple of people were plugging their SLA Batteries into my "Super Charger" (as someone called it - a 25amp power supply) to charge them up faster than their own chargers could manage.

Thats fine by me, but even although my charger has current indicator on it, it was also running my Tritons at the time, which made it impossible to tell whether the 10amps on the display was going into the Tritons, or the SLA's that were being charged at the same time, so they couldnt tell if their battery was sufficiently charged yet or not.

If you were to make up a "charging lead" that had a suitably rated light globe in series with one of the leads, then when the battery was drawing current, the globe would glow brightly, and as the SLA charged up and the current dropped off, the globe would dim and eventually go out, showing you the battery had stopped taking power and was (hopefully) full..

Something like a car interior light globe maybe, or perhaps a 6v globe would be better (since its unlikely your battery would be at 0v when you put it on charge). a bit of experimentation might be required to find the right rating of globe, since you dont want it to blow at full charge current, but you want it to go out once the current has fallen off to 100mA or so..

It would be good for people who charge multiple SLA's from a single charger as well, since if each lead had its own globe, you could easily see which batteries were full and which ones werent.

I cant think of any reason why it wouldnt work, and it should be a very cheap and easy indicator to put together a few of. I hope it helps people
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Post Mon May 23, 2005 12:51 am 
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