Topic: Battery Charger (Read 9745 times)

polaris · « **on:** December 31, 2006, 04:26:17 pm »

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

Faraday's Cage · « **Reply #1 on:** December 31, 2006, 04:47:50 pm »

Hi Bernard,

Have a look at this one :-

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.

DickyD · « **Reply #2 on:** December 31, 2006, 04:53:35 pm »

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

Stavros · « **Reply #3 on:** December 31, 2006, 04:58:41 pm »

Ok link works but where are they how the heck do you contact them no e amil add ??????

barriew · « **Reply #4 on:** December 31, 2006, 05:02:00 pm »

They appear to be in Belgium, but no UK stockists listed >:(

Barrie

rats · « **Reply #5 on:** December 31, 2006, 05:14:05 pm »

http://www.modelsport.co.uk/?CallFunction=Category&ManufacturerID=1013&CategoryID=404020

try the above -they stock them

justboatonic · « **Reply #6 on:** December 31, 2006, 05:36:34 pm »

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.

DickyD · « **Reply #7 on:** December 31, 2006, 06:01:07 pm »

Quote from: Stavros on December 31, 2006, 04:58:41 pm

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

polaris · « **Reply #8 on:** December 31, 2006, 06:07:59 pm »

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

Faraday's Cage · « **Reply #9 on:** December 31, 2006, 10:06:19 pm »

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.

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.

Tug-Kenny RIP · « **Reply #10 on:** December 31, 2006, 10:14:42 pm »

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

Faraday's Cage · « **Reply #11 on:** December 31, 2006, 10:30:20 pm »

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.

polaris · « **Reply #12 on:** January 01, 2007, 10:58:21 am »

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!!!

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

Faraday's Cage · « **Reply #13 on:** January 01, 2007, 11:19:30 am »

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.

polaris · « **Reply #14 on:** January 01, 2007, 01:27:30 pm »

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

polaris · « **Reply #15 on:** January 02, 2007, 06:59:52 pm »

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

polaris · « **Reply #16 on:** January 02, 2007, 07:30:49 pm »

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..

Faraday's Cage · « **Reply #17 on:** January 02, 2007, 08:04:26 pm »

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

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.

polaris · « **Reply #18 on:** January 03, 2007, 01:03:28 am »

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

polaris · « **Reply #19 on:** January 03, 2007, 06:48:22 pm »

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

roycv · « **Reply #20 on:** January 04, 2007, 09:51:28 am »

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

Faraday's Cage · « **Reply #21 on:** January 04, 2007, 01:13:48 pm »

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.

polaris · « **Reply #22 on:** January 05, 2007, 11:07:10 am »

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.

wombat · « **Reply #23 on:** January 05, 2007, 11:32:57 am »

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

Tim The Wombat

polaris · « **Reply #24 on:** January 05, 2007, 05:01:30 pm »

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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Author Topic: Battery Charger (Read 9745 times)

Stavros