Slow battery drain

Discussion in 'Technical' started by sinclair1969, Sep 6, 2010.

  1. After running into problems time and again for the past fur months I am convinced that my bike suffers from slow drain or leakage of electricity from the battery. I have changed batteries at six to eight weeks intervals, only to find that I need a new battery again and again. Apart from the cost this is a frustrating experience, because I don't feel safe driving anywhere as I never know when the battery is going to conk out on me next.

    I had a mechanic measure the charge a few weeks ago, he said the charging is normal at over 14 volts with engine running. He does not think it is the regulator, also sometimes known as the "cut-out" but put my problem down to using a too small battery, a 9AH one, whereas a 15 AH battery would be needed. Well I changed from a 9AH to a 13 AH battery, which was an improvement, but now it is dead and the bike won't start.

    My question to the board members is this: Have you ever had a similar problem, and if so, how did you solve it?

    The process of going over the whole wiring system with a tester-meter to find where the power is draining off is a lengthy process, not mentioning a very involved one, with an uncertain outcome in some cases I have heard.

    On another note, I send good wishes to you all and hope you will never run into a problem like the one I am having.

    PS my bike is a 750 Honda Magna.
  2. I finally managed to remover the battery today after getting a set of hexagonal keys. When I checked the fluid level in the battery I discovered that it was half dry and I added a lot of water. I will charge it tomorrow and see what happens after that, but I wonder why the acid and water has gone down so much in such a short time. I hope that adding water regularly will solve this problem, as looking for a short is a major undertaking.
  3. Could it be that your battery is being overcharged. A faulty regulator maybe?
  4. Well you already know one of the problems is that the battery is to small. even your new 13amp one is TO SMALL. get the correct size or in fact if it fits go a little larger (since your bike was made battery tech has come along way) if your are using a battery that is to small then each time you start you are placing a greater load on the battery. also you could be damaging your starter or starter clutch. Happened on my bike the previous Thai owner had been a skinflint and but a minuscule battery on the bike (just like you did) It was always a problem to start for him until in the end it bolloxed up the starter clutch. I had to order the parts from the US.
    Here is a battery supplier.

    measure your battery and bike battery holder then ask them for the biggest battery that will fit. Also David may well be correct overcharging will give the same symptoms.

    Good luck

    just googled. these are the possible battery's for your bike depending on year.
    VF750C-C2 Magna 94-01


    VF750C V45 Magna 82-83


    VF750C V45 Magna 88


    VF750F V45 Interceptor 83-84


    VF750S V45 Sabre 82-83

  5. How much tinkering do you want to do? and how much are you able to do...

    You said the mechanic told you the stator is charging at a constant 14V... do you believe him? or do you want to check youself??? Fitting a volt meter is simple enough... if it is charging at more that 14.4V you have a problem... overcharging heats up the battery and causes the water to evaporate...

    Next is to disconnect just one terminal from the battery, and with your multimeter set to Ampres, put the probes between the terminal and the lead... with everything switched off, the multimeter should read 0mA...

    If it isn't reading 0mA, pull out one fuse at a time until you identify which circuit is draining power...

    Buy a Gel Battery or a Glass Matt Battery instead of a normal wet acid battery... much higher cranking current for the same size battery...

  6. Thanks for good advice to all of you. The 9 AMP battery was put in the bike not by me but by a large big bike garage here in Bangkok. They vouched for this battery as being the best for all Honda´s (a very general statement). I had no reason to disbelieve them. I have all the gauges and meters right here, so I will check the stator charging etc. I re-charged the battery today and now the bike runs like a dream, however that will probably not last until I find the problem. By the way the bike is a 1988 model in great shape. I will look for the other battery types as soon as I know where to look. Al tough I live in Bangkok I know next to nothing about where spares and accessories can be gotten.

    Thanks again.
  7. Thanks for the link, I will visit this supplier soon.
  8. Since I posted on this subject last time, there have been some developments and I have a couple of questions. After I managed to get the correct battery for the Honda Magna, one day I discovered that the battery was dead and so removed it and charged it, as I now have my own battery charger. What struck me is that the battery was almost empty of fluid, I had to fill it up with a lot of water. Then I charged it and used the bike next morning without problems. Then I checked it again and was surprised to find that some of the electrolyte or whatever the fluid is called (the mixture of water and sulphuric acid) had drained off in only three days. So I filled it up with more water, then drove home and removed the battery. It felt very hot to the touch which I think is not a good sign.

    What can this be? Is the alternator shut or do I need to get a new regulator? I know it can be either reason.

    On my second bike, the Honda 1300 X4, a mechanic told me that the regulator was shot and I needed a new one. Does anybody have any idea as to if this is available in Bangkok and what would a normal price be for this item? I suppose regulators are not all that different in price between brands.

    Thanks for your attention.
  9. Most likely, the bike is overcharging, which usually means a problem with the regulator...

    Get the electrics checked if you know someone good... typically, the battery should have 12V or so with everything turned off, and a slightly lower reading with the ignition on, but engine not running... start the engine and you should show 14V or so... it might show 12V until you get to 1500rpm, as sometimes they set it up so you aren't taxing engine power at idle/just off idle...

    The voltage should stay pretty stable at 14V from 1500rpm to whatever you are comfortable flat revving the bike too while you take a readying (5000rpm)... if you are getting more than 14.4V, you probably have a regulator problem...

  10. Thanks a lot for that. I have been waiting for the weekend to come up so I can do the tests in daylight, as I am occupied during weekdays here in Bangkok. BM Stubber has also kindly offered to send me an charging system fault finder, for which I am very grateful. I have a handy multimeter of good quality so I should be all set. I have also been looking for information on the internet and I have seen some people complaining that motorcycle regulators and rectifiers especially from Honda are of poor quality. They seem to get too hot easily and on many bikes they don't have cooling fins, although they are built to handle currents up to 40 Amperes. So some have advised to replace them with Yamaha regulators. I am looking into this problem and thanks for all good advise.
  11. Just replaced the regulator/rectifier on my Suzuki. On the Suzuki forum they recommend using a "Shindengen FH012AA used on the late (06+) Yamaha FJR, 07+ Yamaha R1 among others What makes it better is that is a MOSFET controlled device rather than the crude SCR type that is on most of the Suzuki series and also is a 50A rated device"

    I used one off a late model CBR600RR which is smaller than the FH012AA, but also a MOSFET design. Working well.
  12. If you know what you are looking for , Red Baron has boxes and boxes of used regulator/rectifiers for sale. Takes a while to find the right one, take the old one with you or go by the numbers. They will usually allow a return if it doesn't work. Might not be any better than the old one but I have had good luck with used late model Japanese regs from Red Baron.
  13. Thanks for the responses on this thread and very useful information. I have done some homework here and have found out that bike regulators and rectifiers are often a problem, and also that some guys have gone as far as make their own. That, however needs knowledge about electronics which I don't have and is definitely not for everybody.

    I am a bit ashamed of what happened in case of my Magna V45 but on Saturday I decided to test the regulator using a multimeter I have here. Now comes the bad part but I don't care if somebody will laugh at me, because I deserve that for my stupidity in this case. The Magna has of course two power cables running from the battery, both are black and not easy to distinguish between the earth and positive poles. Well as you have probably guessed by now, I put the battery in the wrong way, and it stayed that way for about twenty seconds. I realized my mistake as smoke started to come from a part of the wiring harness. I was quick removing the cables as you can understand. I used my pickup truck to bring the bike to a good mechanic I know here in Bangkok, who works for a Honda dealership. He is very skilled when it comes to big bikes, as he worked exclusively on them for many years until he changed over to smaller bikes.

    I told him what had happened and to my surprise he said it's no big deal. I was worried that the starter relay switch had been burned out, but that was not the case. The 30 amps main fuse to hot and the plastic partly melted but still the fuse held out, which told me that my mistake had not destroyed anything much, however a wire harness of some eight wires got overheated and had to be replaced. I got a second hand regulator-rectifier for 2500 baht, a bit expensive but genuine for this bike, at another bike shop. The I got a new battery and I will know tomorrow how things have worked out. Some of the fuses in the fusebox were of the wrong amperage also, for example there were 15 amp fuses where there should only be 10 amps.

    This story is a lesson to me to never act rashly when it concerns the electrical system of a bike, and make double sure I am hooking things up the right way.

    Such a beginner's mistake, and I feel very stupid as a result of it.

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