Smegnoguk Posted April 7, 2003 Share Posted April 7, 2003 We are always told that it is necessary to disconnect the battery before charging. Is this really necessary? Can I damage anything by not disconnecting the battery? 🤔 Link to comment Share on other sites More sharing options...
V7 SLR Posted April 7, 2003 Share Posted April 7, 2003 I regularly put mine on charge and have never disconnected anything. So far, no problems except nearly blowing my house up because my last battery was knackered and started to boil over the 2 days I left it on charge.... yes, 2 days... I forgot about it until all I could smell was bad eggs. One spark and we might have been history. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Smegnoguk Posted April 7, 2003 Author Share Posted April 7, 2003 Whoops! I put it on on Saturday! Better get home smartly tonight. Many thanks! Link to comment Share on other sites More sharing options...
Chris W Posted April 7, 2003 Share Posted April 7, 2003 You can calculate the time required to charge a battery from its present state to full charge as follows. (You can obtain the state of charge using a hydrometer or measuring open-circuit voltage). So let's make up some figures...... Say, present state of charge = 50% Charging current = 2 amps (fairly typical for an average charger) Battery capacity = 30 AH (AH = ampere-hours, eg: the typical Caterham Banner battery) Charging is about 70% efficient ie: 30% of what you put in is wasted as heat and chemical processes. Therfore we need to put in 15AH if the charge is at 50% to start. So at a 2 amp charge rate this should take 7.5 hours. But at a 70% efficiency we actually need to charge it for 7.5/0.7 = 11 hours. By analogy a totally flat battery will take just under one day max to charge. If you leave it charging significantly beyond this, you will start to overheat the battery and boil off the water with damaging consequences. It's not quite so critical actually, as your charger will not continue to deliver 2A once the battery voltage starts to rise, but leaving the battery charger on for a couple of days can cause real problems, especially if your charger charges at a higher initial rate than 2A. There are plenty of 4A, 6A and 8Amp chargers on the market. You don't need to disconnect the battery nor remove the caps to charge it. After all, the alternator will charge it with a very high current if necessary (up to 30A) and it's still connected to everything then. Of course the alternator is under electronic control and knows when to reduce the current and/or stop charging. A trickle charger will be charging at maybe 150mA - 200mA initially falling electronically, as the battery voltage rises, to a few tens of mA, so can be left permanently connected. Chris  1.8K SV 140hp see it here Link to comment Share on other sites More sharing options...
V7 SLR Posted April 7, 2003 Share Posted April 7, 2003 I've just ordered a battery conditioner device (Race Technology's). Does this come under the "trickle charger" type that can be left on permanently? Each winter I take V7 apart only to find the battery is knackered when I return the car to working order. I've ordered this conditioner to try to avoid this in future. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
tomroche Posted April 7, 2003 Share Posted April 7, 2003 I have used one of these "intelligent" chargers on all my vehicles (2 motorcycles and two cars) for the past 3 years and can confirm that it "does what it says on the box" !! All my vehicles are fitted with a "standard" connector (I use 1/4inch jack plus and sockets) to enable easy connection - the connector is also useful for powering intercoms, GPS dvices etc ! Tom Link to comment Share on other sites More sharing options...
Chris W Posted April 7, 2003 Share Posted April 7, 2003 V7 The only real way of answering your question is to say that if the conditioner instructions say it can be left on permanently - then it can. But make sure it does say this on the box. I use a conditioner all the time. No battery should be left uncharged for more than a month - it will kill it - hence your previous winter experience. rgds Chris 1.8K SV 140hp see it here Link to comment Share on other sites More sharing options...
Ian B Posted April 7, 2003 Share Posted April 7, 2003 I use 1/4inch jack plus and sockets Be careful of these, they can provide the connected device with a reverse polarity voltage whilst being plugged in/out A lot of 12v devices have diode polarity protection but its safer not to 'test' it each time its connected. Better to use a Cigarette light socket, and you can then use other 'standard' devices as well.  Ian - MI 5EVN - Slightly Vider 😬 Link to comment Share on other sites More sharing options...
Chris W Posted April 7, 2003 Share Posted April 7, 2003 I agree with Ian's concerns on using 1/4" plugs as power sockets. For my trickle charger, I use Maplin battery connectors (part no. JG04E male @ £1.99 & JG05F female @ £1.49). Safe and durable. I wired the female part into the car and made a cover out of a piece of heatshrink which just slides on and off. I lopped the crock clips off the end of the conditioner and soldered the male connector on to the end instead. Really quick and easy to connect up the trickle charger when the car is garaged. Chris 1.8K SV 140hp see it here Link to comment Share on other sites More sharing options...
Smegnoguk Posted April 7, 2003 Author Share Posted April 7, 2003 Hmm. I like the sound of the cigarette lighter socket (not that I smoke). Would I simply connect the charger up to a cigarette lighter plug? Link to comment Share on other sites More sharing options...
Chris W Posted April 7, 2003 Share Posted April 7, 2003 Yes but make sure you put a fuse in line with the socket. If you're gonna use it as a cigarette lighter too, put a 15A fuse in line..... and of course ensure it is wired to a permanent 12v, ie: not switched by the ignition. The disadvantage of the cigarette lighter socket if you only want to use it for charging is that you will have to cut a relatively large hole in the dash which is more difficult than just connecting a flying lead with an appropriate plug under the dash. Chris 1.8K SV 140hp see it here Edited by - Chris W on 7 Apr 2003 17:01:43 Link to comment Share on other sites More sharing options...
Ian B Posted April 7, 2003 Share Posted April 7, 2003 I've fixed a twin cigarette lighter socket to the bulkhead under the dash above the passenger footwell (with the sockets facing downwards). Its fed via an in line fuse directly from the battery (fuse near the battery for best protection). I used a surface mounting twin socket as it had two fixing lugs to make the job easy - not so I could light 2 cigarettes at once  I bought an £18.99 trickle charger/conditioner from Halfrauds (that can be left connected indefinitely), cut off the croc clips from the end of its lead and fitted a Cigarette plug.  I simply plug the charger into the cigarette socket when I put the car in the garage, no need to remove the bonnet and no dangling wires/connectors etc.  Cigarette plugs and sockets can probably be got from Halfauds or Maplin - Maplin now do this single flush panel mount here if you want to drill a big hole  Ian - MI 5EVN - Slightly Vider 😬 Edited by - Ian B on 7 Apr 2003 17:47:31 Link to comment Share on other sites More sharing options...
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