Dont know when battery is charging.

Sometimes, this is a result of a battery that is too cold (below freezing-warm it up). Sometimes it can be too hot (discharged under heavy stress-let it cool down). Sometimes there may be insufficient voltage, I have had problems in older houses, get closer to the electrical panel to plug in, or you may have to wait until you get home. Red flashing may mean https://www.youtube.com/watch?v=8rZqYmPsZycthe charger or battery is to hot and must cool down before it will charge. The charger will not charge a battery if the lights are flashing. Solid Red light means it is charging and solid green light means it is charged. Plug the charger in first before putting the battery on the charger. If the charger has been dropped or hit the floor the coil inside could have broke loose and damaged the charger requiring it to be replaced. Below is an unconventional way to charge the battery if the charger is no good. BE CAREFUL
how to charge broken makita BL1830 Li ion battery

Based on experience I can tell you that it is is generally the temperature/cutoff/individual cell monitoring sensor in charger that dont allow the batteries to take a charge. Once the same condition is detected 3 times by the same charger it considers the batteries to be bad and refuses to accept it. I have 2 batteries that wont charge on one charger but works perfectly fine when i charge it on my other Makita charger so basically there is no problem with my batteries.
I would suggest first you check the voltage of your drained battery by a test multimeter. For 18volt battery if it is close to 18volts 1-2 volts less is just fine! Then there is no issue with your battery. Makita chargers are very expensive hitech which is useless in my opinion the lipo chargers (used in rc hobby) example skyrc are better quality cheaper and does a better job and you can easily charge your makita battery with it as well but this is only recommended if you decide not to go with Makita charger any more. Some basic information about multi chargers for Li-ion battery to follow the safety is make sure you use the right connectors with correct polarity. For 18v volts max voltage should not exceed more than 20.50 and the allowable charge current is 2.7amps also ensuring that batteries dont heatup.

The DC18RC are most likely to charged the BL1830 battery, which is the most popular of 18V Makita power tools. It is a Li-ion battery.

And the DC18RC battery charger has two volt 110 Volt and 240 Volt.

The 240 Volt DC18RC charger can replace model DC18RA & DC18SD because of its improved performance and full compatibility with Makita's NEW 'Star' labelled batteries that communicate between the tool, battery & charger. And, it is a fast charger.

It can charge a Makita BL1830 Battery in approx 22 minutes.

But, I do not recommend to convert a makita charger model DC18RC at 110 volt to 240 volts.

The reason is as below:

1. This will void product warranty ! If you follow this mod, you do it on your own risk !

2. There are several comments that described
same model # but with different design and components.
Please beware that this mod might not work on your charger
or worst, will damage it.
Only perform this mod if you know your way around with electronics !

If both lights on the charger are flashing it is indicating you have a bad battery and the charger will not charge the battery. The charger has circuitry that tests the battery and if it 'thinks' the battery is defective it will not attempt to charge it. The only way to verify whether it's the battery or charger is to try charging your battery on another charger or try charging another battery on your charger. Most of the time it's a bad battery.

according to the schematic I saw yes you can and I think that you will be pleased with its performance, their operator manual even lists the weight of tool with this battery. Makita has a 1 year limited warranty on the Li-Ion battery that you might want to consider if you have the receipt.

depending on the saw you bought, (or other tool) some come with what is called a "rapid charger" and some come with a small "trickle" charger. most cordless tool batteries take about 1 to 1 1/2 hour to charge (from empty) using a rapid type, the trickle charger will take up to 8 hours to charge a battery. if you want fast, but the rapid charger, and usuallly when you buy one you can get a free battery with the deal.

If both lights are flashing it means the battery is defective so it won't charge it. By defective it could mean the battery is just worn out or there may be a short in the battery. If the battery is under warranty you can get it replaced at a Makita Service Center, if not you have to buy a new battery.

Return to store for replacement.

The two are not compatable. The battery chargers are also not compatable. The main difference between the two batteries is the Amp Hours. The 1815 is only 1.5 Amp Hours and the 1830 is 3.0 Amp Hours. The slide pattern for the batteries are different respectfully. You will need a DC18SA battery charger to charge the 1830 batts.

As long as the charger voltage and the battery voltage match (7 volts) there should be no problem. A fast charger just runs more current thru the battery (per unit time) than a not-so-fast charger. If you notice the battery getting really hot when it's charging (like too hot to touch), stop using it.