The grinders are absolute pants, not enough power, if you lean on them at all they just cut out. You have to be very delicate when using them, maybe ok for very light work but as an alternative to a corded grinder - forget it! 
As for the batteries - the 2ah ones are useless in the grinder. I bought 4 2ah ones when they were on offer, intending to gut them & use the cells in other tools. It takes all 4 to keep the grinder running as you only get a few minutes run time from each one.
If you want a good cordless grinder I can recommend the 18v LXT Makita variable speed one. Every bit as good as a corded one plus it has an electronic governer, so whatever speed you select it maintains that no matter how hard you lean.
You can buy the bare unit for around £100 so if you have the batteries already it makes sense. It runs ok on the 3ah battery but the 5ah are a lot better.

As for the batteries - the 2ah ones are useless in the grinder. I bought 4 2ah ones when they were on offer, intending to gut them & use the cells in other tools. It takes all 4 to keep the grinder running as you only get a few minutes run time from each one.

If you want a good cordless grinder I can recommend the 18v LXT Makita variable speed one. Every bit as good as a corded one plus it has an electronic governer, so whatever speed you select it maintains that no matter how hard you lean.
