paul connor Posted January 7, 2009 Share Posted January 7, 2009 Ok. I have two verisons I have been told, who can clear this up?? 24V system. I want to run a 12V radio. Do I?.... tap off one battery 12V. And assume it will charge at the same rate as the other one? Or by an invertor to change the voltage to 12V Some people say tapping off one is fine, others are very sure one battery will discharge and be ruined over time?? I know you can get 24V radios but I have a nice one already.. Quote Link to comment Share on other sites More sharing options...
sirhc Posted January 7, 2009 Share Posted January 7, 2009 Paul, Use a convertor. Plenty on ebay. http://shop.ebay.co.uk/items/?_nkw=24v+to+12v&_sacat=0&_fromfsb=&_trksid=m270.l1313&_odkw=12v+to+24v&_osacat=0 Chris Quote Link to comment Share on other sites More sharing options...
Davie Posted January 7, 2009 Share Posted January 7, 2009 I tap 12v off one battery, but have a 12v solar panel that is connected when the land rover is not in use to top up the battery. No problems so far. Quote Link to comment Share on other sites More sharing options...
paul connor Posted January 7, 2009 Author Share Posted January 7, 2009 I think Invertor is the best Idea too,Any idea what ampage a Cd radio would need? saves me going out "there " in the cold and hunting through boxes to find the bloody thing Quote Link to comment Share on other sites More sharing options...
fv1609 Posted January 7, 2009 Share Posted January 7, 2009 (edited) Ok. I have two verisons I have been told, who can clear this up?? 24V system. I want to run a 12V radio. Do I?.... tap off one battery 12V. And assume it will charge at the same rate as the other one? Or by an invertor to change the voltage to 12V Some people say tapping off one is fine, others are very sure one battery will discharge and be ruined over time?? I know you can get 24V radios but I have a nice one already.. Paul neither is a very good idea. If you tap off 12v this battery will never charge up fully. It is in series with the other battery & when that is charged it will draw no more current so there will be no charge to the lower battery powering your radio. If you use a regulator be mindful that when they are connected they draw a small but significant current even if the radio is not turned on. If you turn off the regulator each time you will loose the backup memories for pre-tuned stations. Some regulators generate hash interference in various parts of the radio spectrum. There are some very expensive regulators that are a bit less greedy at the standing current they draw, but when I last looked into it them they cost more than buying a 24v radio/CD player! Edited January 7, 2009 by fv1609 Quote Link to comment Share on other sites More sharing options...
paul connor Posted January 7, 2009 Author Share Posted January 7, 2009 I am more for the CD player, the radio can be tuned each time if need be. So ill isolate every time not in use etc.. prob fit a battery cut off.. any advice on a good one? Quote Link to comment Share on other sites More sharing options...
Chrisg Posted January 7, 2009 Share Posted January 7, 2009 I am more for the CD player, the radio can be tuned each time if need be. So ill isolate every time not in use etc.. prob fit a battery cut off.. any advice on a good one? Untill you forget Quote Link to comment Share on other sites More sharing options...
paul connor Posted January 7, 2009 Author Share Posted January 7, 2009 what you saying? I'm going mad in my old age! haha... If i fit full battery key cut off I should be ok Quote Link to comment Share on other sites More sharing options...
fv1609 Posted January 7, 2009 Share Posted January 7, 2009 Paul, just wire the regulator into the ignition circuit. Quote Link to comment Share on other sites More sharing options...
Guest catweazle (Banned Member) Posted January 7, 2009 Share Posted January 7, 2009 I run an electric fuel pump on the champ off one battery,i know all the theory but the batteries lasted 3yrs and still ok,i only reckon a battery for that time anyway,They last less when in a vehicle that stands around and gets little use .I would take a chance,i often charge mine seperately anyway. Quote Link to comment Share on other sites More sharing options...
Degsy Posted January 7, 2009 Share Posted January 7, 2009 When truck mfrs finally got into the 20th century and started to fit radios they were 12v with a dropper in the wiring, in those days most drivers used a CB radio as well and usually just tapped off one battery. Whilst I appreciate that they were in regular daily use they would also get lay up periods and I never experienced/ heard of any problems. As I understand it your Land Rover is your daily drive and with a 90 amp alternator I can't see why you should have problems with either method. Quote Link to comment Share on other sites More sharing options...
Tony B Posted January 7, 2009 Share Posted January 7, 2009 A LOOOONG time ago I was working for Godfrey Davis Hire Cars at Heathrow. A brand new X suffick Renault tractor unit with transporter was delivering cars ready for christmas rush. In the general ho ha a Ford Cortina estate got stuck on the transporter. Don the chief mechanic came to the rescue. While he was working underneath, the rest of us giving encouragement a well spocken lady of a certain age came up to us peered at Don who was under the trailer and said 'Excuse Me'. Don looked up and replied 'Not now darling I'm very busy' . 'Oh but it is important replied the gallant soul' Don sighed 'Well what is it?' 'I think you'd like to know, your lorry's on fire'. The driver had fitted a twelve volt radio cassete on a single tap. My advice a proper well fused converter. Quote Link to comment Share on other sites More sharing options...
Adam Elsdon Posted January 7, 2009 Share Posted January 7, 2009 (edited) Paul, i have 24 - 12 volt vehicle convertors 10 Amp i think, might be higher rated i cant remember, collecting dust, as new ex Fire Brigade, i think they are suppressed for radio work, Drop me a PM they be cheap! Edited January 7, 2009 by Adam Elsdon Quote Link to comment Share on other sites More sharing options...
antarmike Posted January 8, 2009 Share Posted January 8, 2009 (edited) Tap each battery and fit a "break before make" double pole changeover switch, so that either battery can run the radio. Each day flick the switch and run off the other battery. (wont stop you losing your tuning) but it balances out the draw from each battery. If you are feeling enthused fit one of those clever little battery backups to the radio or "memory keeper", (as used to keep codes etc, when a battery is removed for servicing, Draper do a cheap one that will do the job, at about £20.) (make sure radio doesn't use Earth return.) This will keep the radio live as the switch is thrown. http://www.totalbatteries.co.uk/sc-Vehicle-Memory-Keepers-I1168.htmlhttp://www.totalbatteries.co.uk/sc-Vehicle-Memory-Keepers-I1168.html Edited January 8, 2009 by antarmike Quote Link to comment Share on other sites More sharing options...
Stormin Posted January 8, 2009 Share Posted January 8, 2009 I was going to suggest manually swapping the batteries occasionally to balance the load on them, but Antar Mikes solution above sounds far more elegant. Quote Link to comment Share on other sites More sharing options...
fv1609 Posted January 9, 2009 Share Posted January 9, 2009 (edited) Paul you will probably get away with tapping 12v off for quite a while. Drivers of commercial vehicles are none to worried about the longer term consequences of doing this. But it will catch up with you eventually when the "lower" battery will let you down. I know I used to do that many years ago & learnt my lesson. If you have a circuit of electrical items in series, the same current has to flow equally through all components. One component cannot demand additional current. Once the "higher" battery ie the untapped one, is charged it will stop drawing current. Therefore no more current can be made to flow into the "lower" battery which is still undercharged. With time any battery denied its full charge regularly will fail to perform properly. The fact that the system could deliver 90 amps doesn't get round this imbalance of needs at all. Trying to get round this imbalance by selectively charging the "lower" battery is terribly difficult, as you have to ensure that both batteries regularly receive a charge to match their needs. Although I say I learnt my lesson. I didn't really, in another vehicle I used a 24v inverter to produce a separate 12v supply to top up the "lower" battery. But inevitably what went in didn't always match what got taken out. Be very wary of using a car radio on the "upper" battery. I have never come across one that didn't have a negative earth to the body of the radio nor indeed one that didn't have the same to the braid on the coaxial cable for the antenna. Unless perhaps if you were thinking of using a "ghetto blaster" where the chassis is hidden in plastic. Even if the whip antenna was connected to earth you could block that with a capacitor just in case the whip feed touched the vehicle chassis. A final thought Paul, you haven't been tapping off 12v in your Pig? I seem to recall lending you are starting handle a few times:-\ Edited January 9, 2009 by fv1609 Quote Link to comment Share on other sites More sharing options...
Mark Posted January 9, 2009 Share Posted January 9, 2009 Another thought is why have a stereo in a military vehicle surely the noise the vehicle makes is music enought ? Quote Link to comment Share on other sites More sharing options...
paul connor Posted January 9, 2009 Author Share Posted January 9, 2009 The pig had one duff battery, I changed for another that was not as duff. but it needed charging up.. ok now:) Quote Link to comment Share on other sites More sharing options...
paul connor Posted January 9, 2009 Author Share Posted January 9, 2009 just sorted new batteries for the landrover.. not cheap but peace of mind, as when i tried to start today was very slow and then would not! so replace.. with the battery killswitch.. where is the best place on a 109 ffr with cab mounted batteries? as by the looks i would have to rewire it? as its the "key" type.. also would it be more logical in the + or - wire? Quote Link to comment Share on other sites More sharing options...
paul connor Posted January 9, 2009 Author Share Posted January 9, 2009 just sorted new batteries for the landrover.. not cheap but peace of mind, as when i tried to start today was very slow and then would not! so replace.. with the battery killswitch.. where is the best place on a 109 ffr with cab mounted batteries? as by the looks i would have to rewire it? as its the "key" type.. also would it be more logical in the + or - wire? Quote Link to comment Share on other sites More sharing options...
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