| Forum Home | ||||
| PC World Chat | ||||
| Thread ID: 93280 | 2008-09-10 10:17:00 | Question 12vdc battery charger | prefect (6291) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 704243 | 2008-09-10 10:17:00 | I want to put a battery charger in my camper van so that when 230vac is plugged in the battery charger would automaticaly charge the house battery. Occasionaly people next site have generator or power which I can swop with my homemade rum. A few years ago I started car with battery charger on and connected to 230vac and it smoked the charger. I spoke to an auto sparky and he said it a reverse current thingy happens and burns out the charger. My question is will the charger get smoked when the engine is started with no repeat no 230vac connected? If answer is yes can I fit a diode thingy to prevent smoking the charger? My auto sparky said he didnt know. I dont want to spend mega bucks on a special camper charger if a super cheap auto 25 buck one will do the job, only need a couple of amps overnight. Last trip the playstation3 and tv on inverter and lights, water pump etc the house battery died and I connected the start battery so the kids could finish their games. Next morning no juice for start but luckily ground sloped for crash start. Appreciate any help |
prefect (6291) | ||
| 704244 | 2008-09-10 10:39:00 | ctek. they make you have have wired up to the mains plug so when you plug the caravan lead in (240v) it starts charging straight away. i think ambulances etc use them so they charge up the batteries while they sit at the station. how are you charging the house batteries off the the vechile batteries? just wondering if it would be better to wire the charger to the vechile battery first and when that is charged up enough it then charges house battery. |
tweak'e (69) | ||
| 704245 | 2008-09-10 11:03:00 | The house battery is normaly charged by a solar panel but I have a battery connector switch which can connect the house battery to the start batteries. The solar panel smacks in 6 amps so I dont really need to connect the house/start batteries even when travelling. The solar panel is stink at night although can about 50 miliamps from a full moon. My question is what will happen to the charger if the engine is started but with no 230vac connected. I dont want to go down the ctek charger route it would probaly cost more than the crummy CFcamper van is worth. |
prefect (6291) | ||
| 704246 | 2008-09-10 22:57:00 | Hi At a guess, I'm not sure your sparky was totally correct. If your battery was already low then you started the engine then this may have tried to draw heavy curent from the charger. This would smoke the charger as you found out. The second possiblity is if the alternator was producing more voltage after the engine was started then this would indeed give a reverse voltage situation. A simple diode would fix this possibility but the first still remains. There is no free lunch, a diode would drop the charger's output by 0.7 volts. Not such a big deal but with such currents it is a factor. Seems to me a more common sense approach would be to prevent this happening in the first place automatically. This will also fix your current, (pun intended!!), problem. Simply wire a relay into the chargers output. The relay coil is wired to earth and the alternator light output. Now when you start the engine the battery charger output is isolated regardless of 240 volt input. Simple!! Not a good idea to drive off with a 240v lead attached though!! Similar circuits should be used to isolate the car/house batteries and the solar cell. Forget the manual switch, do it automatically. It is rather hard to understand electrical wiring using words so if you would like me to draw a diagram, drop me an email via this forum. BURNZEE |
Burnzee (6950) | ||
| 704247 | 2008-09-11 00:34:00 | Burnzee I am not worried about starting the motor with the battery charger plugged in to 230 vac and turned on ie 230 vac to the charger. I know whats going to happen. Maybe in first post I didnt make claear I want to know if the charger will get damaged with the 230 vac not connected What I would like to know will the battery charger get smoked with the 230 vac power not connected repeat not connected. I am quite happy with relays etc but I dont know if a battery charger will get smoked if the engine is started and and the 230 vac is not connected or turned on Thanks for reply |
prefect (6291) | ||
| 704248 | 2008-09-11 01:57:00 | Hi The problem one has about answering your question is there is not a simple yes/no answer. It depends on the individual circuit of the battery charger but a diode in series should be able to protect against this as stated above. A good test is to simply connect your charger to the battery without 240 vac and see if there is no spark. Don't start the engine. Remember common sense around pertrol etc. If you have a multimeter, see if any current is flowing into the charger. If yes to either one, put a diode in series with the charger's output. Repeat test. Once no current is flowing into the charger then it's ok to start the engine. Most modern chargers should be ok, but test to be sure. Now consider this, you have a solar panel already charging the battery. Now you want to place another charger across it. The solar panel will already have a diode fitted but will this protect it against reverse bias (a reverse current thingy), if the charger is on a night or when the solar cell is producing very little voltage? You will have to install a switch to isolate them. If you did what I suggested earlier using relays then this would cease to be a problem. Hope this helps BURNZEE |
Burnzee (6950) | ||
| 704249 | 2008-09-11 02:58:00 | :waughh: :waughh: | R2x1 (4628) | ||
| 704250 | 2008-09-11 04:33:00 | Thanks for reply. I shouldnt have mentioned solar panel because it and house battery and its circuits are self contained ie the sun smacks in 6 amps plus. It just has a switch to connect to starter batteries for emergencys only needed to use ity once. As far as my circuit goes for the charger pos come out of chargerto ampmeter out of the amp meter to the start battery. Earth wire of battery charger is earthed to body. It works well plug in 20 vac the 230 vac is hardwired into the the charger and the amp meter shows about an amp going into the start batteries 1 amp about right because the batteries are charged up. I am just too scared to hit the start button I want to know if there will be a damaging reverse current to the charger ( with 230 vac off). I will/wont push the start button and try it if someone can give me a yes/no. |
prefect (6291) | ||
| 704251 | 2008-09-11 05:29:00 | what type was the old charger ? the old unregulated ones might have a problem but modern electronic ones are short protected . however some don't like running off poor AC (ie some generators or inverters) a decent charger should still be able to handle being connected full time . i can't say for sure, i know the ctek ones come highly recommended but i would guess a cheaper one would do . what i don't know is the effect of alternator noise will have on it . its a case of try it and see . or you could wire a relay up so it disconnects the charger when ever the ignition is turned on . out of interest is your solar panel PWM regulated ? |
tweak'e (69) | ||
| 704252 | 2008-09-11 05:45:00 | It's a very bad idea to use a "cheap" battery charger on your very expensive deep cycle house battery. It's not a very good idea to put one on your start battery either. There's no excuse for a charger without voltage regulation these days. If you've got solar panels in the system too, I'd talk to someone who knows about such systems, not a local sparky. ;) A clever regulator might get upset if it gets reverse current (perhaps through the substrate diodes of MOSfet switches). |
Graham L (2) | ||
| 1 2 | |||||