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16 May 2010, 10:46 (Ref:2691395) | #1 | ||
Rookie
Join Date: Aug 2009
Posts: 64
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Trickle Charging a Red Top Racing Battery
I've been looking at trickle chargers for the redtop 25 battery in my car and most I've come across mention beig trickle chargers for 12v lead acid batteries but make no mention of dry cell or gel batteries.
Is there a difference? My mate bought a package for his car with a racing battery and specific trickle charger, which promptly cooked the battery anyways blistering the casing. There's a solar cell unit in Maplin that looks ideal for keeping the battery topped up (cheap and doesn't need plugged in to mains) but I dont want to risk frying the battery! |
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16 May 2010, 11:40 (Ref:2691436) | #2 | ||
Racer
Join Date: Nov 2009
Posts: 202
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The problem with charging a gell/absorbed mat battery (Varley red top, oddercy etc) is that the gell cools a lot slower than a liquid asid battery, and gasses cannot ecxape if overheating happens.
So long as you keep the charging rate below 7amps then you will be fine. Prefrably around the 5 amp mark. Some of the automatic motobike chargers are good for this. Halfords do some good auto chargers. Just ensure it is set to 'bike' and 'sealed' battery type. If you have a master circuit shut down on the car make sure this is ON when charging, otherwise it will cook as you friend had happen. Regards, SD |
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16 May 2010, 15:22 (Ref:2691599) | #3 | |
Veteran
Join Date: Jul 2005
Posts: 1,981
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Red Top and batteries of similar construction can of course accept huge currents when re-charging from an alternator after cranking. But alternators are voltage regulated devices, which MOST ordinary battery chargers aren't. The ouput from a correctly functioning alternator should be between 13.6 and 14.4 volts - and no more.
If you stick a volt meter across the output leads of a regular battery charger in fast charge mode when they are not connected to a battery you will get upwards of 15 volts. When you hook the leads up to your Red Top the current drawn will cause that voltage to fall due to internal resistances in the charger - such as the transformer. As the battery charges it will draw less and less current - and the voltage across the terminals will rise. When the charge voltage gets to a critical level - lets say 14.4 volts - then the battery will start to be damaged. The 'special' chargers are voltage regulated to I think 13.4 - 13.6 volts 'float' voltage. The float voltage is lower than the charge voltage, which is varied during the charging process by the internal electronics to keep the charging current constant at typically 2 amps even if the battery is 90% discharged. Because they have a regulated float voltage these chargers can be left connected indefinitely without causing any damage, even when the battery is fully charged. So, going back to the use of a 'regular' charger: they are fine to use as long as they are disconnected when the voltage across the battery terminals reaches 14.4 volts. If you leave it connected any longer then this voltage will rise and the battery will begin to suffer damage. As most people do not stand over their batteries with a volt meter during the charging process, then the chances of disconnecting the battery at the right time are slim, so the safest thing to do is use the correct charger. I have re-charged Red Tops with a regular charger - either on fast charge for an hour or so or a whole day on trickle charge - but only when I have been in a position to make regular voltage checks. But if I am leaving a charger connected overnight or longer then I use the proper charger. |
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16 May 2010, 15:40 (Ref:2691612) | #4 | ||
Race Official
Veteran
Join Date: May 2003
Posts: 11,141
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My eight year old RedTop never looses any charge if everything is off (kill switch) and when I do need to recharge it, normally after lots of cranking and a non start, I use a normal charger with no problems.
I have used one of the Maplin ones, a 1.5 w whereas the one you are talking about is the £7.99 1w version although it shouldn't make any difference and it works well and has caused no problems so far. |
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17 May 2010, 07:35 (Ref:2692268) | #5 | ||
Veteran
Join Date: Nov 2006
Posts: 9,391
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Believe it or not my Anglia has been in the race box since November 2008 and it started up under its own power a couple of weeks ago.
This has a couple of Varley red tops that have always been charged with a maintenance charger (up to that November)that can be left on indefinitely. |
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