Dear Jeff,

In May last year, I purchased a 3KVA 24 volts inverter (Victron model) from a local distributor along with 4 units of 12 volts 200AH wet batteries connected 2 in parallel to meet the 24 volts required by the inverter. However less than 2 months into the use of the system 2 batteries failed and the supplier replaced then with 2 new batteries of the same make. A short while later (about 2 months again) 2 batteries failed again. The supplier advised that I should replace the batteries with dry cell deep cycle batteries which cost about twice the former units which I did. Now just about 8 months into the use of these deep cycle batteries, the run time provided by these batteries have dropped from about 24 hours to less than 4 hours.

I have contacted the supplier and at first he said the inverter needed servicing which he then carried out but the run time has remained the same. He now says the batteries may have failed since according to him the unit is operating efficiently. My problem now is that I am weary about investing in new batteries which are expensive since they might fail again.

What do you think might be the problem and is there a way I can tell what happened to the batteries.

Regards

Eme Iheanacho

Eme:

You have not provided enough information for me to help. For example, is this inverter being used as a backup power system and only draws down the batteries during a power outage. Is this an off-grid system and the inverter is re-charging the batteries using a generator?

Here are a few points without knowing how this is being used. It sounds like the inverter is over-charging or under-charging the batteries. Have the charger set-points been adjusted for the batteries you have? If I had this many failures in less than 2 months as you describe, I would be packing this equipment up and sending it back for a refund. I would NOT switch to gel or AGM sealed batteries. If you are destroying wet cells this fast, you will really destroy a sealed battery as they are even more sensitive to improper charging.

Good luck,

Jeff Yago

Dear Jeff,

Thank you for your response. The inverter is being used solely as a back up power system when there is a power outage. I also have a generator. I had it before the inverter and now use it to run heavier loads or when the outage has lasted for very long.

And I wish I had packed the inverter up and returned it then but I felt that maybe the batteries were faulty.

Regards

Eme

Eme:

Even though I did not have all the information about your system when I made my first comment, I feel like my suggestions are still true after reading your followup information. In standby mode where a grid-connected inverter is only being used as backup several times a year during a brief power outage, there is very little battery charging going on and the inverter should only be providing a small “maintain” charge to offset any standby losses in the batteries. Wet cell batteries may not be the best choice for this type of application as you will need to simulate a power outage every few months to force the batteries to go through a discharge and re-charge cycle to keep the electrolyte mixed. Wet cell batteries are very forgiving of poor charging performance and when over-charged they usually just need more watering. However, if you switch to sealed gel or AGM batteries which are better for stand-by applications before you solve this charging problem, you will just destroy more expensive batteries because they cannot be re-filled once they are dried out by over-charging.

Either you have a very good-quality inverter that has the wrong charging set-points programmed in, or you have a very defective inverter that is over-charging the batteries and I would not keep buying more batteries until you are sure which is true. I am really surprised your dealer is suggesting more batteries when there is clearly a problem with the charging.

Good Luck,

Jeff Yago

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