Inverter drained batteries to zero...

[ChrisMX]

I am lOoking at a pv system set up in the folliwing way:

3x3 240w pannels / 72 Vdc
Flexmax 80
48 v batterie array built from Trojan L16GAC (6V 390 Ah @ 20hr), bought new 18 month ago
Outbackpower inverter FX3048T

4 month ago the system was aparently working fine. Then it was disconnected in the following way.

- AC load disconnected
- Controler disconnected from batterie bank
- solar pannels disconnected from controler
- batteries stayed connected to inverter all the time

I tested the system today. Battery bank over all 8 batteries measures 9.6 v, some single batterias show 0 volt.
The pannels read 102 v open circuit.
The controler does not start up as battery voltage is to low, must be minimum 10.5 v acvording to manual.

I suppose the batteries where drained by the idleing inverter over the 4 month without charging them. Obviously the batteries have to be precharged to start the controler again. But what can I expect from the batteries? Are the damaged after discarged so deeply?

I apreciate any input, thanks to everybody jumping in!

Chris, Mexico.

[Paul Land]

Mexico, I guess it was very hot and no trickle charging. Well the good news they didn't freeze. the 1 @ 0v dragged others down.

[Mike90250]

Yep, sad to say, the batteries are likely toast.

Easiest way to try to fix, take at least 2 batteries to a station for recharge, so you get 12V working.
Bring the recharged batteries back to the system to try the long slow process of fixing.
( it may be easier to take all the batteries to a station to get charged over a 3 or 4 day period, it will take a long time with only solar, to see if they will recover)

How to "jump start" the system.
1) You must attend it constantly, plan on an hour to babysit it.

2) disconnect the inverter
3) leave the charge controller connected to the BATTERY as it normally would. Start with 12V of battery, the controller should auto set to 12V system
4) connect the PV panels and let them start charging the batteries.
5) using a high power light bulb (auto headlight or a 250 or 500w worklight, wire the bulb to charge a pair of questionable batteries. The bulb will prevent a dangerous overload. When the sun fades, disconnect the questionable batteries, measure their voltage, and then remeasure them in the morning. If they are better, keep going every day. if they are not, give up on them and start with the next pair of batteries.
Lather , rinse, repeat......

But usually, batteries that have sat dead for a couple days, are totally shot, and are trash.

[PNPmacnab]

Assuming you are out in the middle of nowhere. If you have a long extension cord, you can run a wire to your car battery and charge one. Some other small extension cord you will have to sacrifice for connections. Then the next and just keep going. Assume you have a meter to verify polarity, you can charge a battery backwards. The light bulb trick also works. Charge controllers either switch the positive lead or negative. You need to disconnect both panel wires from the charge controller. These can then be connected to the battery bank with one lead thru a lamp. That should put enough charge to get the controller started again with only a fraction of a full charge. From there you will have to see how well they balance. For sure you have done some damage.

[ChrisMX]

Thank you for the found answers. Actualy the system is not mine, but somebody who did not know messed arround with it. The owner will figure now out what to doo.

Chris.