Model Boat Mayhem
Technical, Techniques, Hints, and Tips => Batteries & Chargers => Topic started by: polaris on December 31, 2006, 04:26:17 pm
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Dear All,
May I ask some advice please.
Is there such a thing as a battery charger that is 12v and mains input, that will charge/discharge 6v/12v gell cell AND Nimh 7, 8, 9v - 3 to 5ah batteries in both cases?
Regards, Bernard2
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Hi Bernard,
Have a look at this one :-
http://www.bmi-models.com/site/index.php?i=3496 (http://www.bmi-models.com/site/index.php?i=3496)
Ive had one of these from santa for christmas.
It should be capable of doing what you want although, I doubt if it will charge a 12 volt gel cell from a 12 volt source as you normally have to put a bit more voltage in than comes out at the other end. Ive cycled a couple of packs of 8.4v 3700 Nimh without any problem. Still to try my gell cells.
Regards, Terry.
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Beat me to it. Just the people I was going to suggest.
The Boss bought me one for Christmas but I haven't used it yet.
Happy New Year Richard ;)
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Ok link works but where are they how the heck do you contact them no e amil add ??????
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They appear to be in Belgium, but no UK stockists listed >:(
Barrie
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http://www.modelsport.co.uk/?CallFunction=Category&ManufacturerID=1013&CategoryID=404020
try the above -they stock them
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Re the BMI charger. I have one of these and its a good piece of kit.
I think it can charge up to 14 1.2v cells at once. However, its a pulse charger not a linear charge and as such, lot of the lads who run Nimh batteries say to avoid pulse chargers as these are not the best for these type of batteries. A pulse charger also takes longer to charge a 7.2v 3700 mAh pack than a linear charger will. Typically, this is around 50 minutes per pack.
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Ok link works but where are they how the heck do you contact them no e amil add ??????
Hi mine came from Westbournes they stock them
Richard ;)
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Dear All,
Thankyou very much for the replies and info..
Terry, could you let us know how you get on with the gel cells please.
Happy New Year To All,
Regards, Bernard2
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Hi Bernard2,
Ive just topped up a couple of gel cells, both 12 volt, on the BMI charger previously mentioned and Im amazed at some of the results.
First battery was 12v 7ah and charged using mains supply through the charger.
Charge current climbed towards 1.5 amps and once voltage reached 14.70 volts then charging current gradually reduced while the voltage remained stable at 14.70 volts. This is the charateristic of a typical gel cel charger.
Once charging got down to 250ma then charger alarmed to indicate end of charge and charging ceased. This took about 45 mins.
Second test was carried out using a 12 volt 7.0 ah gel cell as the supply to the charger which was charging a 12 volt 3ah gel cell. Supply battery voltage was measured at 12.79 volts whilst charging voltage was measured at - wait for it - 14.70 volts. :o
As I didnt believe what I was seeing I took some voltage measurements with a multi meter and confirmed my initial findings.
See photo. Multimeter voltage is taken from supply battery. Charger voltage is shown on display - bottom right.
Therefore my previous statement that you cant charge a 12 volt battery from a 12 volt supply doesnt apply with this charger.
I cant explain reason for results I got other than it maybe to do with the pulse effect as described in a previous post in this thread.
Hope that this will be of some help. It certainly has opened my eyes as been from an electrical background it just isnt logical.
Beam me up quickly !!! ;) Oh, and a happy new year to everyone.
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Hi Faradays Cage
Have you tried the measuring with an Analogue meter ie an AVO.
Methinks the digital meter is a slow reaction to change.
Cheers...Ken
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Hi Ken,
I havent got a proper AVO but test rechecked with a test bench anologue meter with same results.
Only difference was that I was using a 12v 3ah gell cell for supply and charging a 12v 7ah gell cel.
Supply voltage was 11.85 volts and output went 15 volts then settled to just under 15 volts.
Strange but true.
By the way, congratulations on becoming a captain.
Happy new Year.
Terry.
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Dear Terry,
Thankyou for the info., very interesting! Though having a bit of 'gnrl. knowledge' I am no expert, but I did think you were right in not expecting a 12v input to charge a 12v battery. This is good news! A 12v 600Ah vehicle source should run things with no problem at all!
I know I will probably be expecting the impossible now, but do you think the charging of two 12v (say 4Ah) gel cell batteries using this 12v. input is out of the question??? - we seem to have overcome one impossibility so why not another!!! ;D I should imagine by the sounds of it that this charger is capable of charging two NiMh 8.4v 3Ah at the same time?
Regards, Bernard2
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Hi Bernard2,
I personally wouldnt recommend charging more than one pack / gell cell at a time as it appears that the charger uses a microprosser to sense when battery / pack is charged. Therefore if more than one pack / battery is charged at the same time then I doubt whether the sensing circuity of the charger would cope unless the packs are perfectly matched and it could all end in tears. :'(
It would be a shame to write off the charger especially as they arent cheap to buy.
Terry.
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Dear Terry,
Sensible thinking, and you are quite right I'm sure. Thankyou for all the info., very helpful. Unfortunately I will when the time comes need two chargers, since the vessel will be using 2 x 12v OR 2 x 6v gel cells though I haven't made my mind up yet - much depends on the person who's helping me with the elecs. etc.. Mind you, it could be a question of getting four batteries rather than two chargers for two batteries.... four batteries would not need me to take chargers out with me. This scenario has been 'proven' now with the other vessels , so in retrospect I should stick to this 'system' now. I will get one of these 'new' chargers though, as I do need a discharger... so important I feel to keep batteries in 'good health'.
Thankyou again for your help.
Regards, Bernard2
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Dear All,
Don't rely on ModelSport supplying tech. info. over the phone because they seemingly can't, futhermore, if you want such they only refer you to the mfrs.. It is impossible to get an email adds. from their Website since they seemingly don't have one... and they don't seem keen to supply it openly (definitely not from the Webiste), so the only alternative is to order direct, so, 'you pay's your money and take's your chance' (with a Co. not easy to get tech info. from). I will however order the charger as-is, do this as an experiment for all, and will let you know what happens! 11 CCJ's taken out last year (all successful), and hopefully this exercise won't be the first of this year!
Regards, Bernard2
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The initial order didn't quite go according to plan, and I advised my Card Co. of the circs., however, the second try seems to have worked, and so they have my money! I am sure I will get the product, but it is as well everybody is aware that I do! Will advise when recd..
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Hi Bernard2,
I got my BMI charger from Modelsport without any problems except no instructions with charger. Downloaded them from BMI site.
http://www.bmi-models.com (http://www.bmi-models.com)
Look under downloads and the model no is 2141. It will then download as a pdf file. Only 1st 7 pages are relevant as all other pages are in different languages.
Terry.
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Dear Terry,
Thankyou for your Post.
I hear what you say, but if their service is not what it should be as distributers (and my initial experience is sadly very poor), it is only right and proper that they are told so directly. Rest assured, that, I will, if necessary, make sure they will know this be the case. I have no truck whatsoever with incompetent &/or amateur dealers, they are best dispenced with, and it is to all our advantage they are dealt with accordingly. I hope this will not be the case in this circumstance.
If this Supply Company wishes to respond???
Regards to All, Bernard2
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Dear All,
I feel I was unfair to this Co. yesterday, and write to correct this. Yesterday was an horrendous day one way and another, and I should have 'engaged brain before operating keyboard'! After having to do battle with some others during the day, I wasn't in a very good mood at all... however, we all get these days from time to time. It was a pity the person I spoke to wasn't a touch more obliging, if so, I wouldn't have been so 'grumpy', but, after looking at the Invoice, if ordering via their website there is no postal charge - which is certainly a very good service/consideration. I did say politely could I do the order over the phone 'there and then' to save having to go back onto the Site and have to go through the 'rigmerole', but they wouldn't do it. I must say I can't quite see what the difference is really, since I would have paid with the same Bank Card. However, rules is rules I suppose.
Anyway, today being a much kinder day, and me being 'non explosive' as a result(!), I did feel the need to put the 'record straight'. I am certain this product is excellent, and I look forward to receiving it.
Regards to All, Bernard2
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Hi all, going back to the point about getting a higher output voltage than the source voltage.
I seem to remember in my dim and distant past that there were such things as voltage doubler circuits. Perhaps that or a more sophisticated version of this circuit is in use?
regards Roy
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Hi Roy,
Thats the conclusion I came too also. Cant think of any other way it could be done. No doubt someone with a little more knowkedge will prove me wrong.
Terry.
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Considering all the help offered, I felt it only right I try and investigate this matter. The Univ. based electronics R/D engineer I knew well in the past has moved recently to another Univ., so someone is going to try and track him down for me. However, after speaking to another friend (a Physicist specialising in electrics, magnetics, and 'radio waves'- and seemingly many other highly complex similar things), he told me to say that whilst he is not an electronics engineer, and his opinion is to be treated as a guide, he feels that to achieve what this eqpt. is doing regarding input voltage to output achievement, that a capacitor is being utilised to give a controlled pulse charge - the amp. factor being controlled by the electronics of the eqpt.. He pointed out one can double, treble, quadruple etc., any current with the right electronics/hardware, but he doesn't feel that this is the case here - after I gave him the spec. of the eqpt.. So, Terry, I think you hit the nail on the head in the first place with saying Pulse Charging. I hope this snippet of info. might be of use.
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Voltage increase is a relatively simple thing to do using switching power supplies - you are not bound to multiples of the input voltage. Indeed using capacitive voltage doublers you get a very inefficient conversion.
The principle of the switching supply depend on how you implement it - but basically you store energy in an inductor by feeding it with current and transfer it to a capacitor to get it as a voltage. A diode is used to control the flow of current. The way it is implemented
Designing these things is an art in itself - I certainly wouldn't want to try it, though you can find texts on the subject.
This gives an overview for anyone who is interested:
http://us.st.com/stonline/books/pdf/docs/3721.pdf (http://us.st.com/stonline/books/pdf/docs/3721.pdf)
Tim The Wombat
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Dear Tim,
Though knowing very little about all this, during my telecon this am. with my friend Dr.H., he was generous (as always with info.), to supply a brief lecture on the relevance and processes of stepping up voltages from one voltage/amp. source or another to others. I heard all he said of course, but most of it went in one ear and out of the other quite quickly since it was highly technical, but I did my best to put the bare bones of things in my prev. Post. I recognise bit's of what you say in what he said, but he seemed to put importance on this 'pulse' matter that Terry mentioned, since it seems to overcome/simplify certain other 'things'. Anyway, this matter is way over my head, and, as long as it charges/discharges my batteries, I don't particularly mind how it does it as long as it does it!!! - though it is interesting of course to know how it does it all the same! - if you get my drift!
Regards, Bernard2
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Bernard,
I have sent you a PM but in case you dont receive :-
except no instructions with charger. Downloaded them from BMI site.
http://www.bmi-models.com
Look under downloads and the model no is 2141. It will then download as a pdf file. Only 1st 7 pages are relevant as all other pages are in different languages.
Any probs, let me know.
Terry.
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Bernard,
PM on its way re:- setting up the BMI charger.
Good luck, Terry.
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(Dear Terry, Thankyou again for all your helpful advice. Regards, Bernard2)
Just to let everybody know: the charger arrived on Jan.4 (well packed and sent 'old' Reg.Del.), so a very prompt and efficient service indeed. It is certainly a nice compact and tidy piece of eqpt., and it does come with all the batt. connection leads that one commonly needs - which was a pleasant surprise as I had to make leads for the other two chargers I have (diff. make). The only slight 'irritant' is it doesn't come with an Instruction Booklet, however, as Terry pointed out, this is easy to get from the Mfrs. website. I can understand this as printing is certainly expensive these days (with even medium quan. runs), and to save this cost enables eqpt. cost to be kept as low as poss., however, it would have been handy if the Mfr. had put a note on the box or a slip of paper inside to say how to get the Instructs.. So, all in all, it is a very nice piece of eqpt. and I am very pleased (& grateful), to have been guided to it.
Regards, Bernard2
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Bernard,
Hows the charger going ?
Need any more help with nicads, Ni-mh's
Terry.
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Dear Terry,
Thankyou for asking. There is something I would like to ask as as it happens please.
I don't have the Instructs. with me here so can't quote, but they mention a procedure of charging with varying cell numbers in relation to partic batts. (single cell, dual, etc., etc). At present, my predominant batts. are Sakura 8.4v NiMh 3000 MAH batts., these have two long cells and a small one across the bottom of the 'pack'. I also have two GP NiCd, but these are two long cells only in the 'pack'. So, do I need any special procedure in relation to the cell arrangement of my batts., or do I just proceed as you have already advised?
Thanks again.
Regards, Bernard2
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Polaris
Sounds very much like your GP packs are 6 cells apiece i.e. 7.2 volts. If they aren't labelled then charge a pack up, connect a suitable load (e.g. a motor or 12v car bulb) and check the voltage across the load. A fully-charged 6 cell pack will show about 8 volts, whereas a 7 cell pack - nominally 8.4v - will be nearer 10v.
Looks like a sound piece of kit, that charger.
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Are you sure about the number of cells.
Normally an 8.4v batt. would consist of 7 cells@ 1.2v.
Infact Nicd batteries are made up of 1.2v cells i.e. 6v = 5 cells
7.2v= 6 cells
8.4v= 7 cells
9.6v= 8 cells
12v = 10 cells
Richard ;)
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Dear LeatherJacket & Richard,
I think you have answered my question. I must be honest, I didn't realise that these relatively large batts. were constructed in as many cells.
Leatherjacket, yes, it is an excellent charger. My knowledge of the intricacies of it is yet to be gained though! However, with your and Richards' knowledge you would find it easy to operate.
I must admit I didn't realise that these what look like blocks of 'single' cells were in fact so multiple.
Thankyou for your replies.
Regards, Bernard2
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Hi Bernard2,
Just to confirm what others are saying. Your sakura packs will be made up of 7 cells and GP packs 6 cells.
Each cell is approx. 1.2 volts hence the voltages youve got on your packs. Charged packs will show a higher voltage until load applied and voltage has stabilised. Discharged packs should be somewhere around 1.0 volt per cell or slightly less.
With your BMI charger you can monitor charge voltage on the display but this will be considerably higher than a normal standing voltage.
The charging voltage is regulated by the cells themselves and its only when using discharge function when to need to know number of cells as the charger will discharge to approx. 1.0 volt per cell before changing over to charge mode.
Regards, Terry.
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Dear Terry,
Thankyou for the info.
Regards, Bernard2
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Dear All,
I would like to let members know, that the charger that Faraday'sCage advised me of at the beginning of this Heading is certainly very good indeed.
With Terry's very helpful guidance, and working through the instructions, it is an excellent and very versatile piece of eqpt.. People who are well into electronics/electrics will find it relatively straight forward to operate, however, it is a piece of eqpt. for the initiated rather than those who are not familiar with relatively high-tech instruments. I fit the latter category, but, after help, was able quite quickly to master the basics to get me on my way.
I can also recommend Model Sport as the supplier for this eqpt. - v.prompt and well packed.
I hope this info. might be of use.
Regards, Bernard2