I have 200Ah 12V battery feeding 3000W Multiplus II inverter. I know it's a bit underrated but I'm drawing max 1C. Max consumption is when water heater kicks in for couple of minutes at a time taking 2 kW plus ~400W of other constant usage. Six months ago battery would shut down when charge level was at 5-7% (don't remember voltage). Now shut down happens as early as at 15% charge level (12.9V before the 2kW load). So I'm wondering if I'm putting too much load to battery and it's starting to wear out?
Lifepo4 battery getting tired after 6 months?
- Thread starter pekka8
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RV10flyer
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Considering that most of our setups rarely exceed .2C, you definitely need more battery capacity. What brand and grade cells?
Texas-Mark
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What are you basing the % SOC on? Voltage or an actual SOC meter? Perhaps the battery is never fully charging.
Do you have BMS access on the battery? Wouldn't surprise me if your cells are out of balance (if your SoC readings are correct that is).
Battery is this one (PDF): https://www.suomenakut.fi/storage/p...-TB12200_37eb50f171eaa10ba8aacdd46101e852.pdf
That's all info I have on it. Battery monitor is Victron BMV-712 Smart. One thing came to mind: it has been cloudy here so battery hasn't had a 100% charge for a couple of weeks. Is it possible that battery monitor is getting out of sync? Or cells out of balance?
That's all info I have on it. Battery monitor is Victron BMV-712 Smart. One thing came to mind: it has been cloudy here so battery hasn't had a 100% charge for a couple of weeks. Is it possible that battery monitor is getting out of sync? Or cells out of balance?
Texas-Mark
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Not sure about that monitor's "correction factor", but there will always be some losses between current out and current in (ie. it take 1.1Ah in to replace 1.0Ah out). So any meter that does have some sort of correction will eventually get out of sync if only counting out and in. Usually that error gets reset after the meter hits 100% (i.e. it just stays there until the battery is actually full). So multiple consecutive incomplete 100% charges can indeed cause the meter to get out of sync.
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Yes and yes. With a bit of luck we should get some sunny weather in a week or so: try to charge it fully, giving it time to balance the cells (assuming the BMS has that capability) or reset the state of charge at least.
Shutdowns continue even after fully charging the battery. This week got two while battery was between 40% and 65% charge (~13V). So something else is going on. Maybe water heater is just too much so I'll test if moving it to wall power helps.
Quattrohead
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Yes highly likely. The cells need to get over the balance voltage so that they can be balanced out and topped off plus the BMS will then reset to 100%
Quattrohead
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And this is what happens when you don't read to the bottom of the thread before replying LOL
Tomthumb62
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Do you have a clamp meter? If so, measure DC current (amps) between the battery and inverter when the water heater is heating. If you are drawing more than 200A, then you may be getting battery shutdown because the BMS is only rated for 200A. The Multiplus you have, 3000VA, can pull more than 200A, about a max of 252A. The 3000VA MP also has a surge capability of 5500W = approximately 462A. These Victron devices generally have real-world surge abilities, such as 5-30 seconds (I couldn't find the specs for the Multiplus-II 3000VA), which would be more than long enough to trip the BMS in your battery (battery specs for over-discharge current: 255A±5A，delay time 30s±5s).
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