I can't open the other thread, so here's what I found out...

Formula used battery chargers made by Pro Mariner for some period of time in the 1990's (they use a different manufacturer today). I called Pro Mariner tech support, and found out that the chargers that were being used at that point in time were fixed output chargers, and are not suited to AGP batteries like Optima. He also said they are not the best for lead acid batteries, either; however, their current models have variable charging modes that greatly extends battery life and will work for either lead acid or AGP batteries. Older chargers with fixed output will overcharge batteries and significantly reduce the life of the battery.

They will exchange these older chargers for new ones at 50% of list price, or $290 for a 30 amp version which should be sufficient for most twin engine installations. I'm not sure if it's worth it to me to spend the money, but just thought I'd share the info....

BTW, if you take them up on the exchange offer, you don't have to physically send the old charger in (it weighs > 40 lbs)...just have to supply the serial #.

Do you know what battery charger formula is using now .

New boats are getting units from Charles Instruments which supposedly support the Optima batteries.....

That's very interesting. Wonder if that charger brand is what's in my '89 311. I'll have to check.

Actually, as I think about it. I think my charger is a Guest brand.

Mine is a Charles C-Charger on an older SR357. Charles is first company and the charger they put on my boat is UPTOWN. One thing Optima told me is NOT to exceed 20 amp charge rate and have a cahrger that will trickle down as charge builds up.

I'm still dumping the Optima's--gonna use Trojan Battery's.

I'm giving up on the Optimas for now. By the time I upgrade the charger to support them and spend the $$$$ for the Optimas it would be ~$600... I found a great looking marine battery at Auto Zone for $69 with a 3 yr warranty, so that's my solution. I can spend the $450 in savings on gas!