GeoffL
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FWIW, I've recently upgraded to a hybrid system and recognise some of the troubles described in this thread. In my case, it's a Victron SmartSolar 75/15 with a Polarmax 100Ah LFP in parallel with a 110Ah FLA and I have 2 x 100W panels in series (so full sun in this country gives OC voltage greater than 40V). The thread I started is at https://wildcamping.co.uk/threads/lifepo4-issue.100992/.
If you're having the same issue, it could be an unfortunate combination of a smart BMS and smart MPPT! I suspect that what's happening to me is that cloud or shade temporarily reduces the available solar power, which causes the charge current to drop below a threshold, which causes the BMS to switch to standby mode [i.e. stop accepting charge], which causes the MPPT to switch to float! From that point, the MPPT needs to send a higher charge current than float provides to 'wake up' the BMS to resume accepting charge. However, the BMS is shut down and the FLA only needs float voltage... so the LFP won't get more than a short charge window even though there's 'room for a lot more energy'!
I've got a work around -- but with a huge caveat: the Victron app tells me I might damage my battery via overcharging by doing this... So you do the following only at your own risk!
I've done this, making a rough calculation of how long it should take to reach 100% SOC and then set an alarm on my phone to remind me to revert the absorption time setting back to "Adaptive" once the LFP is charged. It's a PITA, but the only way I've thought of this far to get a decent charge into the LFP.
If you're having the same issue, it could be an unfortunate combination of a smart BMS and smart MPPT! I suspect that what's happening to me is that cloud or shade temporarily reduces the available solar power, which causes the charge current to drop below a threshold, which causes the BMS to switch to standby mode [i.e. stop accepting charge], which causes the MPPT to switch to float! From that point, the MPPT needs to send a higher charge current than float provides to 'wake up' the BMS to resume accepting charge. However, the BMS is shut down and the FLA only needs float voltage... so the LFP won't get more than a short charge window even though there's 'room for a lot more energy'!
I've got a work around -- but with a huge caveat: the Victron app tells me I might damage my battery via overcharging by doing this... So you do the following only at your own risk!
I've done this, making a rough calculation of how long it should take to reach 100% SOC and then set an alarm on my phone to remind me to revert the absorption time setting back to "Adaptive" once the LFP is charged. It's a PITA, but the only way I've thought of this far to get a decent charge into the LFP.