Mazda Repair: Cutting out when headlights are on..., gel cells, miata mazda

Question
Hi,

 I have a 1991 Mazda Miata with around 70k on the clock.

 Last night I started the car, allowed it to warm up for a few minutes then turned on the headlights and the engine stalled - this happened numerous times, so I am convinced the stalling was associated with the headlights.  The car had no issue running with the lights on 'side lights' so I proceeded to drive home planning to asssess the situation there.  On the way home the car stalled out on three separate occasions and had trouble restarting - rather, it would start, but would not stay running (it would fire rev once then stall).  No check engine lights came on or any of the warning lights.

 This is the first Miata / Mazda I have owned, and I've only owned it for a couple of months so I'm not familiar with their 'personalities' when it comes to things like this - but it definately seemed to be behaving similarly to an old Ford I once owned that did this when the negative side of the battery terminal was loose (I have checked this an it is not the case this time around).

 Any help or suggestions would be appreciated.

 Nigel...  

Answer
i work on many miata's, i dont really like them cause i cant fit in one!  but i gotta say there probably the best built car there is, i never see many problems with them. ok  to your question, when you turn on the headlights it puts alot a strain on the alternator, so  first place i would look at is the alt output. also load test the battey cause those little gel cells dont last very long.. gotta be one or the other