From a friend:

"The battery pack on my Pro 6 HID 18 watt has finally died after 3 years.
The
burn time just kept getting shorter and it dropped to under 60 minutes, too
short.

The OEM replacement packs are over $120. Dealer cost is around $70 +
freight.
I decided I would buy the batteries and build a new pack with the plugs,
wires, bulkhead, etc., off the old one.

I went to the local Batteries Plus Store and located 2 each replacement
batteries. These are 3.30 amp hour rated batteries, that is better than the
stock
batteries 3.0 amp hour rating. The units were 21.95 each or 44 bucks approx.
for the batteries.

The guy at the counter tells me I cannot have them till Monday, because they
do not have a tech to reassemble my battery pack working on Sunday.
I asked the cost of this service and the clerk told me there is no charge
for
this service.

I came back Monday and my battery pack was ready. The burn test was over 140
minutes. Dove it this weekend and it is perfect.

They will do this for any size battery pack, pro6, pro14, etc. They will
also
build you a NiMH pack if you want it, and sell you the correct charger.

Helluva deal.