Good day all I have a mecer sol-i-ax 5kva  with a leoch 48v lithium battery what's happening is when it reaches 100%soc on the battery the inverter is kicking in and out pv charge  and the inverter is making a clicking sound when doing so , and on  some days (sunny) total disconnect from Pv charge and supply utilities from battery power only , my previous inverter (no name Brand) displayed 08 code bus voltage too high using the same battery could there be something wrong with the battery ? 

 

Maybe the battery is disconnecting from the DC bus to prevent overcharging. The fact that you got an error message related to a high voltage confirms this to some extent: When a BMS disconnects the battery from the DC bus, the voltage often spikes up (on Victron setups it usually spikes to around 65V, but I've seen higher).

This sort of thing is actually dangerous to Voltronic inverters. Earlier models had capacitors on the DC bus rated to 63V. Later models are rated 85V. Such disconnection events can stress the inverter quite a bit when it was not designed for it.

As I said earlier, don't expect to get support for this battery. It was not sold to the public, and due to the high number of stolen units most installers will refuse to touch it.

18 hours ago, plonkster said:

Maybe the battery is disconnecting from the DC bus to prevent overcharging.

I'm starting to think that a lot of the "dips" problem are exactly this. People are using crazy high absorb/bulk voltages, and Axperts are prone to overshoot their voltage targets, so the BMSs may be disconnecting. When they do, the battery voltage seen by the inverter would plummet. By the time the BMS has reconnected, it may be that the inverter has detected quite a large battery voltage drop. This is a trigger to go from float stage to bulk stage. Axperts are a little unusual in that to do this, they first go to "no charge" state for some 15 seconds, then take a few seconds to check that the PV input is present and stable, then stay at something like 1 A (battery-side) charge for 15 seconds, then slooowly ramp up the charge current over perhaps another 15-30 seconds. The result is that there can be a minute or so of no or very low PV charge current. This can overshoot the target battery voltage on that initial ramp, even though it's so slow, so the whole process could repeat. I believe that this happens with utility charging as well as with PV charging.

Sometimes, installations use 3S of solar panels where 2S would be better, and this can cause additional delay because with little to no charge current, the panel voltage goes up; once it gets close to 145 V, there is little power that the solar charge controller will take, so it takes a while for the panel voltage to decrease below 130 V where full power is allowed. That's for SCCs with the 145 V max PV limit; I suspect that something similar may happen with a long string of panels approaching the 450 V or 500 V limit of other models.