charging

[johnnyg]

hi everyone , new to your site maybe ill get a bit of usefull advice. i have a 1995 cb 750 f2  the battery does not seem to be holding a charge, so do i buy a new battery or could it be something else, i have bikes for years but never learned about electrics or engine stuff, just the basics , cables , brakes. etc. retired now, so lots of time on my hands, thanks for any advice that comes my way, johnny

[shinyribs]

Check to see if the bike is attempting to charge the battery first.

If you don't already own a voltmeter you can get one from Harbor Freight for cheap. I think they are less than $10 and they work just fine.

Just set the meter to read DC volts and read the voltage at the battery terminals with the key off. Then start the engine and check voltage again. See if it rises any from before.

Chances are your bike will not charge at idle, many don't, so you may have to rev the engine to at least 3,000 rpms to activate the charging system. You're looking for about 13.5-14.5 volts while charging.

If your bike is in fact charging then read your battery voltage again after performing the test and you've turned your key off. See what that voltage is directly after testing, then come back and check it later. Maybe in a few hours or the next day. That will determine whether you are charging at all, or if your battery just isn't holding a charge.

If you read voltage higher than 14.7-15 volts or so, you could have a bad voltage regulator which ,left un-fixed, can really hurt some things and will need to be replaced. On a '95 model such as your I'm pretty sure it will have a combined voltage regulator/rectifier unit. Or R&R as it's commonly called.

Good luck!

[johnnyg]

thanks shinyribs, ill check it first thing tomorrow, the weather  is baltic over here,     : ireland: ill be back with readings, going to be looking for more advice as its the first 750 honda ive had. cheers

[johnnyg]

hi shinyribs  i started the bike after i recharged the battery it read about 12. 5v when i brought it up to 5000  rpm it read 14.6v is this normal do you recon the battery is on the way out. cheers johnny

[sgtslag]

Shiny is dead on:  your battery appears to not be holding a charge; the voltage at 5k RPM is normal.  Check the electrolyte levels in each cell, adding distilled water to the cells, if it is a flooded battery (ONLY add distilled water, no acid!).

Be sure to use a trickle charger, no more than 1.5 Amps output.  If you use a car battery charger, pushing 5+ Amps, it will boil off the electrolyte, damaging the battery by over-charging it.  Adding distilled water to any cell will require the battery to be charged.  A very good motorcycle trickle charger is the Battery Tender Jr.,  This will attempt to charge your battery completely, switching to maintain mode, once the battery is fully charged -- useful for long-term storage, as it adjusts its charge mode (three different modes, microprocessor controlled) to avoid over-charging; exposed plates become damaged (sulfated), leading to failure of the battery.  Hooking up your bike after each ride, will top off the battery's charge, which can extend the life of any type of battery (flooded, gel cell, or AGM), by keeping it at an ideal charge level.

Anyway, try a smart trickle charger to top off the battery, first.  After it is fully charged, disconnect the charger, wait two hours, and then measure your battery's resting voltage again:  if it is less than 12.6 (conventional flooded battery)/12.8 (AGM sealed battery), the battery is going out -- budget for a replacement sooner, rather than later.

For bike electrical stuff, this is the best book I've found so far:  Motorcycle Electrical Systems: Troubleshooting and Repair (Motorbooks Workshop).  The author does a very good job explaining electricity, and the bike's electronics, as far as how to troubleshoot problems (discusses/illustrates how to make/use inexpensive tools needed, as well).  Check your libraries for copies to borrow (ISBN-10: 0760327165; ISBN-13: 978-0760327166).  Cheers!

[johnnyg]

thanks you guys, ill do what you said