Hi! I'm the new owner of SR3 1351 and 1372, 2021 SR3XX 1500's. Have had a chance to do a shakedown run on both cars and both have been a delight (cars came from member David F and are in great shape and really well sorted). But both cars have had issues starting despite relatively new batteries and constant time on a Battery Tender trickle charger putting out 1 amp. Was at a test day last week at VIR and 1351 was really struggling, refusing to keep running after a start, showing surprisingly low voltage. Dropped a new battery in and all was well. So I've been researching how to keep these batteries healthy.
Short story is I learned that the Odyssey batteries are unusual. Most lead acid batteries call for a charge at 0.1C, so no more than 1.2amp for the Odyssey PC545. But when you look up the technical info for the Odyssey, it calls for no LESS than 0.4C, so 4.8 amps (tech manual says "In order to achieve the full design cycle life of ODYSSEY batteries in cyclic applications the charge current must be a minimum of 40% of the battery’s 10-hour rating" which is 4.8 amps for the PC545 and crazy high for a typical powersport battery). They state that only after being fully charged can you run a trickle charger. Others might already know this but was a surprise to me.
So my hypothesis is that I drained the battery down screwing around with the new-to-me cars, and then tried to trickle charge them at 1.0 amp, and the Odyssey did not like that. Will run new main batteries in both cars and only charge them with a 10amp charger and see if that keep them alive. I'm also thinking I'll run an external power supply while messing with the cars, which is standard procedure with most race cars I've encountered. Hopefully will keep these batteries from being a frequent consumable.
G'day Brett,
Thanks for the info. I hadn't understood that either.
In terms of other things that you could do to help... I saw a photo of Leon Morell's engine bay on Facebook the other day when he had the engine out being swapped over... I noticed he had an aluminium heat shield formed around the front (and maybe top?) of the battery box. I imagine there is 1 or 2 inches clearance between the aluminium heat shielding and the battery itself.
I was thinking of dong the same myself the next time I get some spare time.
This isn't the best photo but I found another one of his that does show it in the bottom right hand corner... I note also that he has the same heat shield stuff in front of the rectifier on the top of the bulkhead as well...
Yeah, I was pretty surprised when I saw the main battery location on the SR3XX— would think the radiant heat from the headers is wicked. I like the idea of that heat shielding and will likely do something. I did a session this summer where ambient was 103+ and logging showed Air Intake Temps were almost 110 degrees F. Personally I felt like I was melting and can only imagine what the temps were for that battery.
