Yb125 battery wont charge

Sometimes new batteries are still bad, it sounds like the battery wont take a charge, go get your new battery tested and go from there.

Could be a bad battery, and or alternator, if the alternator does not charge the battery when the vehicle is running your battery will drain causing no start.

what kind of car do you have. it sounds like you blown the main fuse or have a dead starter

As long as the alternator seems fine, I wouldn't worry about it. The problem will probably go away after awhile...HA HA, THIS IS A JOKE, from your statement that alternator seems fine. No rudeness or judgemental attitude intended.
Do you have a friend or know someone who has a voltmeter? It would take two minutes to put a voltmeter on the battery while the car is running, and it would tell you if the alternator is working as it should. If the voltmeter says over 13 volts (typically about 13.5 volts, up to 14.5 volts) then the alternator is good, and the problem likely is poor, corroded, or loose battery connections, or the battery may be too old to take a full charge, or may have a dead cell.
If the voltmeter says less than 13 volts (when car is running), then the alternator belt may be too loose, or you may have a loose connection on the alternator, or there may be a blown alternator fuse in the power distribution center near the battery, or the alternator is just too weak or malfunctioning and needs replacing.
Good luck, harlock6, I hope you find the problem. You can buy a perfectly good voltmeter just about anywhere for less than $20. Even the older analog type (with the sweep needle) would work for testing your alternator enough to know if it's working or not. More thorough tests of the alternator's actual amperage output could be performed (like a load test) with more expensive testing equipment, but you just need a voltmeter to check if the alternator is working or not.

you need take old alternator with you to auto parts stores they can match up your alternator give you the correct AMP TYPE, your alternator amps is stamped on the out side alternator housing, the auto parts store can look up right amp alternator for your vechicle.when you say dont matter yes it does if you get wrong type alternator, your battery wont have good charge causing alternator fail early and battery fail early.

System working well and charging the battery, then that means most likely the battery has one or more bad cells and can't HOLD a charge. It may seem fine but it's not what it seems. Good Luck

Remove the batteries .. Every Chair is different .. but if the batteries aren't charging it's probably that they were left uncharged for a time and they dropped down enough that the charger dosn't recognize them .. If they drop down below around 6 volts the charger won't charge them ... I have taken batteries out and charged them individualy with a car charger .. but they never come back .. at best half life.

the battery wont stay charged? if youre putting in a fully charged battery and your car runs, but then the battery slowly dies, the problem will be your alternator. the alternator is what maintains a car batteries charge. try replacing the alternator. hope this helps.

may have a loose connect in wiring or failin alternator--get vehicle scanned and obtain a haynes manual from the parts place

Ihave a ranger older but similar 2010@gmail let me think about it your heat dosn;t have anything to do with with the charging system pier .j i;ll get back to you and by the the way good question