Odyssey TPPL AGM
We have this old battery, which turns out to be seven years and two months old. For good brands like Lifeline and Odyssey we count on an 8 year lifespan, so when I noticed weakness during engine start, I had assumed the battery was nearing its end of life and I started building the Lithium Titanate Oxide LTO battery to replace it with.
This week we took out the Odyssey battery and replaced it with the LTO battery and took the Odyssey to the workshop for evaluation. Now that I have the electronic load, I can do battery tests so let’s do that!
I start with fully charging it at 14.7V until the current was less than 2A. After that I did the first capacity test at the 20 hour discharge rate, which is 5A for this 100Ah battery. The termination voltage for this test is 10.02V under load. The results are in the photo below:
the test lasted 17:53:17, and came out to 89.4Ah (1061Wh so about 1kWh) so that’s 10.6Ah short. End of life for these batteries is considered to be at 80% and here we’re almost at 90%. So I decide to do a recharge and test again because with aging batteries, a full cycle or two will rejuvenate them a bit. For charging I use my Volteq 3030 power supply set to 14.7V and 20A. So it starts at 20A CC (Constant Current) until the voltage reaches 14.7V at which time it changes to CV mode to keep it at 14.7V while the current reduces until it’s below 2A when I terminate the charging. This is the same as the bulk and absorption phases of smart battery chargers.
After that we repeat the capacity test and here are the results:
As expected the capacity has improved a bit to almost 91Ah meaning we have less than 10% degradation. This battery can go back in service! That’s good news because together with the LTO battery we will have our redundancy and ample time to design a version 2 of our LTO battery!
These tests show that buying a too brand battery makes a lot of sense and in the end is probably a better deal financially as well. We have car batteries that don’t last two years even when sitting in an air conditioned garage half the time and here’s an Odyssey after 7 years in a hot tropical engine room and it’s still good to go!
So why did I notice weakness? We hardly use our 12V system because we try to use the engine as little as possible. This means it’s almost never charged by the alternator, meaning we have a Victron Smart Orion DC-DC charger as the primary charge source. For now, I suspect that the Orion, after switching from absorption to float phase, simply never goes back to absorption as long as the voltage doesn’t drop too much. I believe the Victron Multiplus will periodically switch to absorption again to prevent this problem. This simply means our battery wasn’t fully charged plus it was lazy by never being cycled.
