Omega Owners Forum
Chat Area => General Discussion Area => Topic started by: Taxi_Driver on 19 August 2007, 17:58:42
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Charge a 12v lead acid battery (90 or 110AH).....from the omega? And no fitting it as main battery isnt an option.
I could use a 150w invertor connected to a battery charger and all slung in the boot......where the battery will be. But seems a unefficient to me. Ive had a search on the interwebby to see if theres a 12v-12v charger/lead thingy but carnt find anything :-/
Any ideas?
Cheers
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Caravan split charge relay
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Caravan split charge relay
How does that work Martin? Does it limit current? Coz i did think of connecting it to the omega 12v.....but a flat 90-110AH battery is going to want to take a lot of current initially.... :-/
Did think of just connecting it to rear ciggie lighter.......but think it will just pop the 10amp fuse
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Caravan split charge relay
How does that work Martin? Does it limit current? Coz i did think of connecting it to the omega 12v.....but a flat 90-110AH battery is going to want to take a lot of current initially.... :-/
Did think of just connecting it to rear ciggie lighter.......but think it will just pop the 10amp fuse
HUmm made a mistake - still need charging kit as well!
However check this site
http://www.towsure.com/product/562-Fridge/Battery_Combination_Relay
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Could try this http://www.tradingdirect.co.uk/gadgets_easy_start.asp and cut the plug off of one end and put croc clips on.
lee
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Could try this http://www.tradingdirect.co.uk/gadgets_easy_start.asp and cut the plug off of one end and put croc clips on.
lee
Don't mention crocodile clips, you'll give Tunnie a stiffy ::) ;D
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One way would be to tap into a suitable fused power source, the cig lighter is fused at 10A, and stick a resistor in series to limit the charging current. For example a 1R resistor would limit the max charge to 12-14A, but as your battery is unlikely to be totally flat then it wouldn't pass that much. One rated at 10W would be suitable, and Maplins sell them for £0.40. This has the dissadvantage that charging will take a while, say if the battery is up at 10V and the supply is 14V, then max charge is only 4A, so could take a while to fully charge. If the battery will not be below say 6V, you could decrease the resistor to 0.5R (put 2 in parallel). Mind you the cr
ap, sorry thin leads they tend to use on cig lighters leads probably couldn't pass 10A without melting, so you could probably just connect it directly to the battery without any problems. And as a bonus the charging leads would get nice and warm. ;D
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Depends if the battery is going to be permanently mounted to the car or if it's just a temporary arrangement and also how quick you need it to charge. In addition, if there's going to be load on it during charging. For a permanent installation I would run a decent, thick cable from the car battery through a fuse to the rear of the car, with a caravan split charge relay or similar to enable charge to the second battery when the car battery volts rise.
You want to drop as few volts in this cable as possible because if there's too much drop the battery won't reach a fully charged state. If you need to draw load from the battery during charging it might be wise to take this from the end of this cable at the front of the car to minimise voltage drop at the battery end.
For a temporary set up, something to plug into the cigar lighter may do the job, depending on the voltage at that socket with the other loads in the car drawing current. You might find the lighter socket delivers insufficient voltage (less than 13.8 and the battery won't reach full charge) to charge the battery. You may well find that the resistance in the circuit is enough to prevent the current getting excessive, since the battery "looks" like a voltage source of up to 12.5v with an internal resistance. This means that you're only dropping a volt or so across the resistance of the circuit instead of the full 12 volts - unless you start with a totally flat battery, of course.
If it's a temporary lashup and you've got an inverter and a battery charger handy it might be the easiest solution. At least you know the charge to the battery will be under control.
Kevin
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Wouldn't the alt be overloaded with charging a 90-110Ah battery...?
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Wouldn't the alt be overloaded with charging a 90-110Ah battery...?
The capacity of the battery doesn't really come into it. The alternator should current limit at a safe level so the more battery capacity you connect across it the longer it would take to charge it. Furthermore, if you use a caravan charging relay you'll only switch in the second battery when the main vehicle battery has fully charged and the alternator is powering the loads on the car with capacity to spare.
Kevin
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Wouldn't the alt be overloaded with charging a 90-110Ah battery...?
The capacity of the battery doesn't really come into it. The alternator should current limit at a safe level so the more battery capacity you connect across it the longer it would take to charge it. Furthermore, if you use a caravan charging relay you'll only switch in the second battery when the main vehicle battery has fully charged and the alternator is powering the loads on the car with capacity to spare.
Kevin
Okkky dokkky Kevin... I guess that's why we need you on this forum ;D
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The capacity of the battery doesn't really come into it.
.. within reason, of course. If you set off at the start of every journey with a completely flat 110 ah battery in the boot I think the alternator would get the hump, but it's more down to how much charge you're going to be taking out of the battery than its capacity, and that depends on the application.
Kevin
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Depends if the battery is going to be permanently mounted to the car or if it's just a temporary arrangement and also how quick you need it to charge. In addition, if there's going to be load on it during charging. For a permanent installation I would run a decent, thick cable from the car battery through a fuse to the rear of the car, with a caravan split charge relay or similar to enable charge to the second battery when the car battery volts rise.
You want to drop as few volts in this cable as possible because if there's too much drop the battery won't reach a fully charged state. If you need to draw load from the battery during charging it might be wise to take this from the end of this cable at the front of the car to minimise voltage drop at the battery end.
For a temporary set up, something to plug into the cigar lighter may do the job, depending on the voltage at that socket with the other loads in the car drawing current. You might find the lighter socket delivers insufficient voltage (less than 13.8 and the battery won't reach full charge) to charge the battery. You may well find that the resistance in the circuit is enough to prevent the current getting excessive, since the battery "looks" like a voltage source of up to 12.5v with an internal resistance. This means that you're only dropping a volt or so across the resistance of the circuit instead of the full 12 volts - unless you start with a totally flat battery, of course.
If it's a temporary lashup and you've got an inverter and a battery charger handy it might be the easiest solution. At least you know the charge to the battery will be under control.
Kevin
Thanks for the ideas guys :y
The battery wont be totally flat.....it will only be charging in the boot.....and will be temp...Probably lowest voltage it will be drained to will be about 10v.
So probably will go the invertor and battery charger route.......however my battery charger says it draws max 150W, so will have to use 150W invertor to be on the safe side......tho 150W invertor will draw between 10-13 amps if on max load by the charger and the voltage at the rear ciggie socket.....so the rear ciggie lighter socket maybe out if it keeps popping the fuse for it (10A) Will have to try it.....and if it does, run fused wires from the car battery :y
Also need to get a decent charge into the battery after about 1hr or so of charging.
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Charge a 12v lead acid battery (90 or 110AH).....from the omega? And no fitting it as main battery isnt an option.
I could use a 150w invertor connected to a battery charger and all slung in the boot......where the battery will be. But seems a unefficient to me. Ive had a search on the interwebby to see if theres a 12v-12v charger/lead thingy but carnt find anything :-/
Any ideas?
Cheers
The question is.........WHY? :-?
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Charge a 12v lead acid battery (90 or 110AH).....from the omega? And no fitting it as main battery isnt an option.
I could use a 150w invertor connected to a battery charger and all slung in the boot......where the battery will be. But seems a unefficient to me. Ive had a search on the interwebby to see if theres a 12v-12v charger/lead thingy but carnt find anything :-/
Any ideas?
Cheers
The question is.........WHY? :-?
I was wondering when someone was gonna ask ;D
Coz now that im a tent owner.....i was thinking of visiting a site, the week following the nealry in Wales meet.....that doesnt have electric hookup for the tent pitches.....and i wanted to take a portable TV....a 110AH lesiure battery should run it for 5-6hours possibly longer :y
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I'd hope a 110 ah battery would run it for a whole week! If it's a 12v powered TV rather than a mains set on an inverter it should only take 1 or 2 amps at 12 volts.
Kevin
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It may be worth asking the site if they have battery charging facility on site some do then you would not need to worry about charging from the car. I would say a split charge relay would be your best option as per the caravan
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Good point. Or take your battery charger along and ask them if you can plug it in somewhere to charge it up.
I'd be surprised if a 110ah battery didn't last you the whole holiday though.
Kevin
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It won't last long if it's running a colour tv.
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I'd hope a 110 ah battery would run it for a whole week! If it's a 12v powered TV rather than a mains set on an inverter it should only take 1 or 2 amps at 12 volts.
Kevin
It mains powered.....and takes about 50W + 5W for the invertor which is about 4.5amps at 12v, obviously as the battery voltage starts to drop then the curent will increase.....im not quite sure how long a 110ah will last bearing in mind the invertor shuts down when the battery voltage gets to 10v.
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I am making a 12V lead for my TV
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I am making a 12V lead for my TV
I presume a 12v to mains ?
If so and its just for a portable tv.......you can buy 75w inverters off fleabay for around £5-£6 +postage
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Ahh, OK. A mains TV running from an inverter is a different proposition. Much more thirsty.
Kevin
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I am making a 12V lead for my TV
I presume a 12v to mains ?
If so and its just for a portable tv.......you can buy 75w inverters off fleabay for around £5-£6 +postage
Caravan TV uses an external power supply so unplug that and plug in lead
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It won't last long if it's running a colour tv.
I tested the idea on a ropey 47ah car battery that carnt hold its charge for long......it powered the tv from the inverter for 2.5hrs.....thats where i came up with 5-6hrs or poss longer with a 110ah leisure battery :y
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If you only want to run a 12v tv try this http://www.machinemart.co.uk/shop/product/details/jump-start-900/path/battery-chargers-engine-starters-2
i have one that i use for camping and it will run 2 portable dvd players for 4 hours plus recharge my camcorder (using 300w inverter) a couple of times and run a 12v light all night without being recharged. ( and it still has enough power to jump a car )..
plus it comes with a mains and car charger so you can keep it charged at all times.
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If you only want to run a 12v tv try this http://www.machinemart.co.uk/shop/product/details/jump-start-900/path/battery-chargers-engine-starters-2
i have one that i use for camping and it will run 2 portable dvd players for 4 hours plus recharge my camcorder (using 300w inverter) a couple of times and run a 12v light all night without being recharged. ( and it still has enough power to jump a car )..
plus it comes with a mains and car charger so you can keep it charged at all times.
Thanks for the info :y but my portable tv is mains powered and im looking at about 55w continous consumption....which i doubt that device would be capable of for very long :(
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It may be worth asking the site if they have battery charging facility on site some do then you would not need to worry about charging from the car. I would say a split charge relay would be your best option as per the caravan
Ive looked into this :y
Split charge relays (from web sites ive looked at) seem to agree that the main feed cable to the battery should be about 40amp and fused at 30amp....which is sound advice.....which would be ok on normal car batteries.....but this will be a leisure battery (110ah) and recomended charge rate is "bench charge at 7amp" which i assume to be max charge current....if so....using a split charge relay isnt the way to go unless you can limit the current.....my mains bat charger....which i think maybe the way to go using an inverter max charges at 7amps on high setting :y