03-16-2019, 02:45 PM
Just came across an elsewhere forum post that is relevant. Unpublished results of a capacity test on a 300AH battery bank after 4 years of mobile use in a light truck converted for RV use. I am not going to copy and post because of IP issues and lack of peer review. This info is from a person, who enjoys a good technical reputation, who likes Winston batteries and Victron.
Headline info is that after 4 years of use, the capacity of his 300 Ah has been measured at 290 Ah. Two comments - no capacity test was done at installation so the baseline 300 is what the writing on the battery says is the manufactured capacity. Second comment, very low charge rate over days brought the batteries to full charge.
My 50 Ah (nominal) cells came with factory final test data that said they were all around the 52/53 Ah capacity leaving the factory. Using my cells as an example, 300 plated number as a nominal capacity to 290 tested capacity cannot be considered as hard data.
Winston info say 100% charge is to 14.4 at 0.3C. The batteries tested for the forum report were in use and increased in SOC each day until full charge was reached. SOC was established by using a watt meter not voltage. The battery user has decided that for his purposes, 14.2 is the level he considers full charge. Argue the difference between Winston info and the battery user's ideas if you choose, I'm only telling you what the capacity test used at the top end. What is interesting to me is that the rested voltage after 10 hours of his fully charged battery was 13.3 Volts. Rested voltage at the start of testing was 12.5 Volts. Again interesting to me because I decided on my low end voltage is/will be 11.8 Volts. I decided on 11.8 because 11.8 is well into the steep downward trend of any discharge curve I can get my hands on but is still some safe level above disaster voltage levels. Almost ready to bring my low end up a bit but because I rotate my two batteries regularly, neither has reached the low voltage cutoff and I mostly consider the low voltage cutoff as a safety feature, not an operational feature.
One standout comment in the capacity report was that there was a big disconnect between a SOC determined by a watt meter and SOC determined by battery terminal voltage, around the 80% SOC point.
So a couple of things remain fuzzy for me. An exact comparison of capacity, at installation to now, has not been done. Some loss of capacity has been measured but exactly how much is fuzzy. Manufacturer's data on what final charge voltage level to be obtained is more of a suggestion than an exact rule. My personal use of 14.1 as a top voltage charge level is close enough for me. A rested terminal voltage of 13.2 is fuzzy enough for me. Lastly, any SOC based on voltage is a bit fuzzy, especially around the 80% SOC. A cheap watt meter around the $30 mark is good enough and is a lot cheaper than a Victron device. I would like a Victron, just saying that I have other uses for the money, ATM.
Headline info is that after 4 years of use, the capacity of his 300 Ah has been measured at 290 Ah. Two comments - no capacity test was done at installation so the baseline 300 is what the writing on the battery says is the manufactured capacity. Second comment, very low charge rate over days brought the batteries to full charge.
My 50 Ah (nominal) cells came with factory final test data that said they were all around the 52/53 Ah capacity leaving the factory. Using my cells as an example, 300 plated number as a nominal capacity to 290 tested capacity cannot be considered as hard data.
Winston info say 100% charge is to 14.4 at 0.3C. The batteries tested for the forum report were in use and increased in SOC each day until full charge was reached. SOC was established by using a watt meter not voltage. The battery user has decided that for his purposes, 14.2 is the level he considers full charge. Argue the difference between Winston info and the battery user's ideas if you choose, I'm only telling you what the capacity test used at the top end. What is interesting to me is that the rested voltage after 10 hours of his fully charged battery was 13.3 Volts. Rested voltage at the start of testing was 12.5 Volts. Again interesting to me because I decided on my low end voltage is/will be 11.8 Volts. I decided on 11.8 because 11.8 is well into the steep downward trend of any discharge curve I can get my hands on but is still some safe level above disaster voltage levels. Almost ready to bring my low end up a bit but because I rotate my two batteries regularly, neither has reached the low voltage cutoff and I mostly consider the low voltage cutoff as a safety feature, not an operational feature.
One standout comment in the capacity report was that there was a big disconnect between a SOC determined by a watt meter and SOC determined by battery terminal voltage, around the 80% SOC point.
So a couple of things remain fuzzy for me. An exact comparison of capacity, at installation to now, has not been done. Some loss of capacity has been measured but exactly how much is fuzzy. Manufacturer's data on what final charge voltage level to be obtained is more of a suggestion than an exact rule. My personal use of 14.1 as a top voltage charge level is close enough for me. A rested terminal voltage of 13.2 is fuzzy enough for me. Lastly, any SOC based on voltage is a bit fuzzy, especially around the 80% SOC. A cheap watt meter around the $30 mark is good enough and is a lot cheaper than a Victron device. I would like a Victron, just saying that I have other uses for the money, ATM.
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