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Mecer 5kva inverter battery drain


Azz_TJ
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Hi everyone, I have a Mecer 5kva inverter connected with 4 batteries. This was installed in 2019. It used to last though out load shedding and once even lasted 18 hours. However since Jan 2020, it lasts about 45 mins and dies. We’ve had electricians come out and test the batteries and they’ve said they fine and still have full power. But they say we need to replace the batteries with lithium batteries which will cost about R35k.

We already spent R30k on the inverter and really don’t want to pay another 30k. 
 

I know nothing about inverters but why would the batteries drain so fast all of a sudden? Is there maybe something that’s causing them to drain fast? Only lights, TV, WiFi and our alarm system is connected to the inverter so it’s not like we powering fridges and the geyser on it.

If someone is able to assist me or maybe there’s a setting I need to change on the inverter please do let me know? If you need more information I’ll try provide as much as possible 

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12 hours ago, Azz_TJ said:

We’ve had electricians come out and test the batteries and they’ve said they fine and still have full power. But they say we need to replace the batteries with lithium batteries which will cost about R35k.

If the battery is fine, why do you have to replace it with lithium?

12 hours ago, Azz_TJ said:

Is there maybe something that’s causing them to drain fast?

Sadly, there are so many ways that a lead acid battery can lose capacity. The big one is over-discharging.

First, I'd check that you aren't a victim of the premature float bugs. These will cause your battery not to fully charge, which reduces energy available for the next discharge cycle, but also contributes to lowering the capacity and therefore useful life of the battery.

Does your battery voltage rise to the absorb voltage (probably 56.4 V) and stay there for at least an hour? Check especially in cloudy conditions. On a perfectly sunny day it will probably charge the battery properly, but when a cloud reduces panel output when the battery voltage is near the float voltage (often 54.0 V), it can incorrectly decide that the battery is full, and terminate the charge at that point. All Axpert models, unless they have patched firmware, have this bug.

The charge bugs

Can I upgrade my firmware?

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1 hour ago, Coulomb said:

If the battery is fine, why do you have to replace it with lithium?

Sadly, there are so many ways that a lead acid battery can lose capacity. The big one is over-discharging.

First, I'd check that you aren't a victim of the premature float bugs. These will cause your battery not to fully charge, which reduces energy available for the next discharge cycle, but also contributes to lowering the capacity and therefore useful life of the battery.

Does your battery voltage rise to the absorb voltage (probably 56.4 V) and stay there for at least an hour? Check especially in cloudy conditions. On a perfectly sunny day it will probably charge the battery properly, but when a cloud reduces panel output when the battery voltage is near the float voltage (often 54.0 V), it can incorrectly decide that the battery is full, and terminate the charge at that point. All Axpert models, unless they have patched firmware, have this bug.

The charge bugs

Can I upgrade my firmware?

Sorry I should’ve mentioned, I’m not using solar panels. The batteries are charged using electricity from Eskom. Would that be another factor to consider?

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18 hours ago, Azz_TJ said:

, I’m not using solar panels. The batteries are charged using electricity from Eskom. Would that be another factor to consider?

Oh. Yes, definitely a factor. With sensible settings, the premature charge bug never shows with utility charging. So that can't be the problem.

So you need to find out if you have an unexpected load, or if the battery isn't getting fully charged for some reason, or if your battery just has low capacity. One easy check is whether the battery modules have about the same voltage, especially at low state of charge, but also at high state of charge. It could be that one or two modules is low in charge, and charging them separately with a car battery charger might restore a lot of the missing performance.

Long term, some sort of balancer device might be worthwhile, but obviously only if you can restore the performance. 

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5 hours ago, Coulomb said:

Oh. Yes, definitely a factor. With sensible settings, the premature charge bug never shows with utility charging. So that can't be the problem.

So you need to find out if you have an unexpected load, or if the battery isn't getting fully charged for some reason, or if your battery just has low capacity. One easy check is whether the battery modules have about the same voltage, especially at low state of charge, but also at high state of charge. It could be that one or two modules is low in charge, and charging them separately with a car battery charger might restore a lot of the missing performance.

Long term, some sort of balancer device might be worthwhile, but obviously only if you can restore the performance. 

Thank you for this! Will definitely look into everything you’ve mentioned 

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