Problem charging makita batteries 18v li-ion - Makita Tools 18V 1/2" Lxt Lithium - Ion Hammer Driver - Drill Kit - BHP451

Unfortunately, Makita’s li-ion battery packs have a design flaw. After having the same problem with my two batteries, I took it apart and saw the problem immediately. You see each battery pack has ten li-ion battery cells and a circuit board with a memory chip witch holds the charging history of the battery pack. But that memory chip constantly draws power from 2 of the 10 batteries. The current it draws is very small but if you consider it over 8 month or more, the power drain becomes very significant. You end up with a battery pack with 8 still fully charged battery cells and 2 drained battery cells. When you put this battery pack in the charger, it detects weak battery cells, assumes they are defective and refuses to charge. To avoid this problem you should charge your battery pack often, even if you haven't used it, every two months should be ok.
I suspect that Makita doesn’t make these battery packs, they make power tools, good ones too. Buy Makita should definitely have a few words with their supplier before they become a liability!

Welcome to the trials and tribulations of cordless power tools. Essentially they're not meant for intermittent (ie handyman) use. Li-Ion batteries, unlike Nicads have no memory effect and can be regularly topped up, but are designed to run no less than 40% charged and hence the circuitry to prevent that. The reason for that 40% base charge is well appreciated by Toyota with its Prius hybrid, which allows their $4500 battery pack to last 10 years plus unlike a full plug-in which would see such a fully drained to fully charged battery last only around 3 years. With that 40% lower level threshold you can appreciate why cordless Li-Ion batteries need 3Ah ratings instead of commonly 2Ah for professional Nicads. The best bang for buck batteries are still Nicads PROVIDING they're charged and discharged fully on a regular rotation basis AND they are rejuvenated every 30-50 charges by a special forming charger to prevent crystallisation, which occurs rapidly if left in a discharged state. NiCad and NiMH batteries run down at 1% a day standing, so you can see the problem after say 3 months idle. That's why Sanyo developed their Eneloop pre-charged AA and AAA batteries that hold 90% of their charge after 6 months and 85% after 12 months. Ever reached for the digital camera after a few months with standard rechargeables and wondered why it won't go? Not a problem with those special lattice chemistry Eneloops, which makes you wonder if their technology will transfer to cordless power tools any time soon. My advice? Tradeys stick to Nicads with manual refresh chargers like Hilti has and Homies to power cords. If you use AAs and AAAs a lot, then Sanyo Eneloop it is, with a MAHA Powerex smart charger for the requisite 'rejuvenation' cycle periodically.(most chargers on the market are dumb chargers) Forget all the other ignorance and sales pitches out there with current battery technology. Oh and another tip for the Tradyeys. Stop mucking around with 18V cordless driver drill brands because you think 18V tools are for 'real men'. My research and site experience with many failing clutches shows they are often overpowered for their typical 35-45Nm clutches, whereas Hilti's range is rated at 70Nm. You wants to play you gots to pay!

What is the battery or charger not doing correctly?

Its definatly the battery. i just bought a new set because one of the batteries wouldn't charge-it was fine right up to the moment the charger refused. I plugged this into the brand new charger and it refuses to charge it as well. Do you think it has a memory and counts how many charges its has then stops when it thinks you've had enough use out of it or is out of date irregardless if it works or not (just like the hp inkjet cartridges)?

Do you have to charge the batterys over night before use?

My batteries show as fully charged after only 1-2 minutes on charge but don't even last 1 minute in use

IF all cells are ok, Replace the battery management board. £3 ebay.
If you plug battery in and flashing red and green then the board is programmed to block further charging.
Whether you zap it to bring the voltage up or not

Problems with long inactive batteries can *(sometimes) be safe analized by service who have
Battery Analyzers

To fix "bad" Makita batteries that won't charge: Put them in the charger FIRST and then plug the charger in.

Ite seems to be the batterys that dont come from makitta. dont buy the after market batterys, its so easy for the companys to blame you for there poor product..