Backup Battery Bank Troubleshooting

[colin87]

Calling on anyone with some knowledge regarding electricity, batteries etc

I was given a battery backup system, 2000W inverter with built in charger, and two 12v 160ah batteries.

I suspect at least one of the batteries is probably dead. How do I go about testing if the batteries, the charger, or both are at fault, by hopefully spending as little as possible.

I have beers for those who are willing to come and assist, these things weight 70kgs each.

Shot

 

[Beachless]

What kind of tools do you have?
Multimeter battery tester, decent charger?

 

[colin87]

Nothing...thats why I need a cheap option,or convince someone in the area to help. I dont mind getting a multi meter and charger,as long as it would actually be usefull on not end up buying something I cant use

 

[bruce_the_loon]

First, what make/model is the inverter/charger unit. Need to know if it is 12V or 24V.

A car battery charger would prove useful, but not essential.

To check the system, you'll need a multimeter that has DC volts in the 10-40V range. With the meter in DC volts mode, minimum of 20V range selector. Measure each battery voltage. If you get no reading on one of them, that one is buggered. If you get readings between 11V and 14V, the battery should be okay. Below 11V, there might be cell damage. Below 9.5V, you probably have a unrecoverable battery.

If the voltages are below 12.4V, the batteries need charging. If you have access to a car battery charger, you can try and charge them one at a time to see if you can bring them up. A dying battery won't take charge easily and if it goes get to 12.4V, won't hold it for very long under load.

Depending on whether the charger is 12V or 24V, you'll need to rig the batteries in parallel (for 12V) or series (for 24V). Parallel means hooking the positive terminals together and to the positive charger cable, and the negative terminals together and to the negative charger cable. Series means connecting one battery's positive terminal to the other's negative terminal and the positive charger cable to the unconnected positive terminal on the 2nd battery and the negative charger cable to the 1st battery's unconnected negative terminal.

You can check whether the charger is putting out voltage by putting the meter into a suitable range for the 12V or 24V input voltage and probe the charger connection terminals while you have AC feeding into the charger. You should see 12V to 15V if it's a 12V unit, or 24V to 30V for a 24V unit.

 

[Beachless]

I would first check the water levels and top up with distilled water if needed then charge each battery separately on a good qaulity charger and finally test the battery.

If you dont find anyone willing to help you can always take them to a trustworthy battery center and ask them to test them.

 

[bruce_the_loon]

You can get cheap meters from Midas, anything that has a 30V range will do.

Actually, any car battery supplier can test the batteries for you if you can get them there.

 

[mmacleod]

The willard guy in main road strand is decent, if I were you I'd just take them there. They will usually do a basic test/overnight revival for free and advise you further based on the result.

 

[colin87]

@bruce_the_loon

Thanks for the detailed reply. Let me try and cover everything.

The model I have is a Wellsee Ws-p2000w, getting the exact model is proving to be pain. Father-in-law imported a bunch of stuff, this was all extras they had. It is a UPS, with built in charger, solar and wind charger inputs, and then the inverter itself of course.

I have the two batteries in series, as they are 12V each, and the inverter is 24v.

The UPS has an LCD, so I can see whats going on, obviously, it may be bull****ting me, but I'm pretty sure the UPS unit is not faulty. I can see the variable power coming in, and the solid 220v going. I can see the current battery level, and when the unit is charging the batteries.

There are two cables coming from the UPS, positive to positive of battery 2, and negative to negative of battery 1. 1 and 2 connected via positive and negative in series.

Seems step 1, get a multimeter

 

[colin87]

They are sealed units. As they weight 70kgs per battery, I would hopefully get to do some home testing first

 

[colin87]

The willard guy in main road strand is decent, if I were you I'd just take them there. They will usually do a basic test/overnight revival for free and advise you further based on the result.

Thanks for that, will maybe give them a call tomorrow, listen to what they have to say. Like I said, lugging these things around is horrible

 

[dunkyd]

Slowly we squeeze the info out of you......

 

[dunkyd]

Ps. Let the batteries stand for 30 minutes after charging before testing them.

 

[bruce_the_loon]

You can get a rough idea of whether the charger is working by disconnecting the charger from the batteries and using a couple of car brake or indicator light bulbs as a meter. For the batteries, a single bulb will light up brightly if the battery is good. Dim or no light will be a bad sign. To test the charger, you'll need two bulbs in series across the cables. Be careful, sparks can be painful if you short the terminals by accident.

24V at 160AH with a 2000W inverter should give you about 2 hours at full load before the unit shuts off. If you can see the battery voltage levels through the UPS, you should see a steady drop from the starting voltage towards 22V where it should shut down. You can estimate roughly how good the batteries are from that rate.

 

[colin87]

Ok cool.Im a bit scared of testing thr charger part like that,going to try and test the batteries first though,then the charger.

If I get a multimeter,is there a safe way to test the charger?As stated,the same cables both charges and drains the battery,well is suppose to anyhow.

 

[bruce_the_loon]

Testing the charging voltage is safe, the meter presents a high enough resistance across the two probes that you won't get a short when you contact the terminals with the probes. To make sure you are reading the charging supply, disconnect the batteries from the charger.

Testing the charging current is more difficult. Most meters don't have a high enough current range to be placed inline with the cables, you'd have to put the meter between one of the charging leads and the terminal it is connected to in order to get a proper current reading. A meter not rated for 100A will blow if you do that. There are formulas around to calculate the charging current from reading the voltage over a period of time. That's how the Willard meters that the battery shops use to check your car battery work.

 

[The_Traveller]

You need a proper battery analyzer for this.

I've seen tests where batteries with the highest voltage were the ones that needed replacement. So don't be fooled by thinking if you see good voltage range then all is good.

 

[colin87]

Just an update. Taking my system to someone in the area who knows his ****, and runs a big battery backup system. He will look at the equipment and check which part(s) are at fault.