Have I destroyed a battery?

coopec

coopec

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My stem is 24V (2X 12V AGM batteries.)
I was using the wet/dry vacuum cleaner off the 3000/6000W inverter to suck water out of the bilge.
I should have downloaded the instructions for use because I didn't use a foam filter and as a result the motor got water in it and I had a major electrical short.
I tried to charge the batteries but they wouldn't go over 23.4V. When I checked them individually one was 13.5V and the other was about 10.1V.
Since then I have read when charging 2X AGM batteries in series both batteries must be a similar voltage.
This morning I put the 10.1V battery on charge and it is currently 11.9V,
Do you think:
  • I have damaged the battery and shortened its life?
  • the battery will hold its charge?
(Needless to say I plan to install fuses /circuit breakers now)?
 
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I’m a bit confused about this. Surely the inverter tripped out when the motor shorted? Even if it didn’t trip and the vacuum stopped, you switched it off within a few seconds?

Assuming your house batteries were charged up when you started vacuuming, a few seconds of overload shouldn’t kill them.

I’m wondering whether the one battery wasn’t already on its way out and the load from your high power inverter has been the final straw.
 
john_morris_uk said:
I’m a bit confused about this. Surely the inverter tripped out when the motor shorted? Even if it didn’t trip and the vacuum stopped, you switched it off within a few seconds?

Assuming your house batteries were charged up when you started vacuuming, a few seconds of overload shouldn’t kill them.

I’m wondering whether the one battery wasn’t already on its way out and the load from your high power inverter has been the final straw.
Click to expand...

John
The inverter tripped out OK. All batteries are new.

The vacuum cleaner is 1250W at 240A so it was drawing 50A but on start-up it could have been drawing 150A. The plastic around a terminal on the 1/2/Both battery selector switch melted and a earth wire for the solar panels (8 AWG?) must have got very hot as some of the plastic melted. Why? I'll have to work that out. I'm simplifying the circuit: now the solar panel charge the house batteries only and the inverter works off the house bank only. (The 1/2/Both Battery selector switch was rated at 150A continuous)

Right now I'm laying carpet on the floor panels so sorting the electrical problem out will have to wait. ?
 
looks like you have a series of issues to sort out and none related to the vacuum short (imho)
check all cables/lugs/bolts/nuts. Everything must be tight well crimped and secure.
I'm testing my 304Ah 24V lifepo4 bank at home, when I started charging it at 50A through an old Victron Centaur charger, I noticed the GND terminal on the battery was getting hot (much hotter than the + !) on investigation, the lug was loose, cable corroded/blackened strands. Cut it, pressed a new lug with my new 8ton press, all fine and cool.
Melted terminal could be lug/termination, or simply not good enough to stand the 50A (nothing's going to melt with 3-5sec of 150A tbh!)
so check the lot, leave the second battery on charge for a while, but guess you have a duff bat. Is it the one to the + or the one to the GND?

fwiw, I'd regularly run 90-100A off my 4X6V trojans to run the watermaker. Never had any issues with things falling apart and/or melting! pretty sure others do the same as well.
 
vas said:
looks like you have a series of issues to sort out and none related to the vacuum short (imho)
check all cables/lugs/bolts/nuts. Everything must be tight well crimped and secure.
I'm testing my 304Ah 24V lifepo4 bank at home, when I started charging it at 50A through an old Victron Centaur charger, I noticed the GND terminal on the battery was getting hot (much hotter than the + !) on investigation, the lug was loose, cable corroded/blackened strands. Cut it, pressed a new lug with my new 8ton press, all fine and cool.
Melted terminal could be lug/termination, or simply not good enough to stand the 50A (nothing's going to melt with 3-5sec of 150A tbh!)
so check the lot, leave the second battery on charge for a while, but guess you have a duff bat. Is it the one to the + or the one to the GND?

fwiw, I'd regularly run 90-100A off my 4X6V trojans to run the watermaker. Never had any issues with things falling apart and/or melting! pretty sure others do the same as well.
Click to expand...

Thanks for that.

There's a lot I don't understand about what has happened so I'll have to sit down and work thru it. In the meantime I've ordered a whole lot of appropriate fuses and circuit breakers. I've also decided to install a VSR as it should simplify the circuitry .

The 1/2/both battery selector switch is rated at 150A continuos and 250A intermittent so it should have been able to handle the workload.

Your suggestion to check the cable lugs is excellent as I found one that was loose.

Thanks
 
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coopec said:
Thanks for that.

There's a lot I don't understand about what has happened so I'll have to sit down and work thru it. In the meantime I've ordered a whole lot of appropriate fuses and circuit breakers. I've also decided to install a VSR as it should simplify the circuitry .

The 1/2/both battery selector switch is rated at 150A continuos and 250A intermittent so it should have been able to handle the workload.

Your suggestion to check the cable lugs is excellent as I found one that was loose.

Thanks
Click to expand...

How old is the switch? Contacts do wear with age?
 
coopec said:
Thanks for that.

There's a lot I don't understand about what has happened so I'll have to sit down and work thru it. In the meantime I've ordered a whole lot of appropriate fuses and circuit breakers. I've also decided to install a VSR as it should simplify the circuitry .

The 1/2/both battery selector switch is rated at 150A continuos and 250A intermittent so it should have been able to handle the workload.

Your suggestion to check the cable lugs is excellent as I found one that was loose.

Thanks
Click to expand...
when I work with battery/cabling/inverters/chargers, first I remove my watch, then I touch everything (24V that is!) lightly for temp and check all connections with my IR thermometer under load. A 40-50A load is good enough to make sure all works fine, nothing's loose or arcing.
Was the loose lug/connection on one of the affected terminals? If so, 99% that's the reason. Also check the interconnect to the batteries.
Not sure how a fuse is going to help in your setup, but removing the 1/2/both is a good first move :-)
 
Poey50 said:
How old is the switch? Contacts do wear with age?
Click to expand...
I concur. I recently "fixed my inverter" by replacing the main fuse holder - it's the NH type, and the prongs or blades that hold the legs must've become corroded, increasing the resistance and causing the same "low voltage" message at the inverter as you'd get from knackered batteries or cable of insufficient diameter.

I don't see the startup current as a likely cause, as it will have been so brief. But 50A seems a lot.

I don't see how the shorted vacuum can have anything to do with the knackered batteries - they were probably knackered before and it's just a coincidence that you noticed them at this time.
 
1250W at 240V isnt 50A its only 5A! At start, typical DC motor will draw appx 2.5 times its no load current draw, so no more than 12.5 Amps at start. Your Inverter would easily be able to cope with that, even if the motor stalled.
 
The inverter would never be able to supply enough power at 240v to cause major battery problems by over loading the 24v input circuit. it would just shut down or melt. So I don't reckon the vacuum cleaner did harm to the batteries. Unless it was used for some time discharging the batteries.
Yes the 1,2,both switch may have failed with high current ie got hot, heating terminals so melting wires. Yes far better to go VSR. Replace the 1,2,both switch with robust single pole switches. One for domestic loads one for engine start and one for emergency jump start.
It does seem like one battery has failed . It may be a case for returning under warranty. If that is not practical then recharge it alone on 12v charger and then use it under load (inverter) monitor voltage under load of the bad one. It is fortunate you have an apparently good one to compare. ol'will
 
KompetentKrew said:
I concur. I recently "fixed my inverter" by replacing the main fuse holder - it's the NH type, and the prongs or blades that hold the legs must've become corroded, increasing the resistance and causing the same "low voltage" message at the inverter as you'd get from knackered batteries or cable of insufficient diameter.

I don't see the startup current as a likely cause, as it will have been so brief. But 50A seems a lot.

I don't see how the shorted vacuum can have anything to do with the knackered batteries - they were probably knackered before and it's just a coincidence that you noticed them at this time.
Click to expand...

As I said in comment #10 everything is new
 
mickywillis said:
1250W at 240V isnt 50A its only 5A! At start, typical DC motor will draw appx 2.5 times its no load current draw, so no more than 12.5 Amps at start. Your Inverter would easily be able to cope with that, even if the motor stalled.
Click to expand...

I'm using a household electrical vacuum cleaner which draws 1250W on 240V
My yacht electrical system is 24V so how many amps at 24V??
 
William_H said:
The inverter would never be able to supply enough power at 240v to cause major battery problems by over loading the 24v input circuit. it would just shut down or melt. So I don't reckon the vacuum cleaner did harm to the batteries. Unless it was used for some time discharging the batteries.
Yes the 1,2,both switch may have failed with high current ie got hot, heating terminals so melting wires. Yes far better to go VSR. Replace the 1,2,both switch with robust single pole switches. One for domestic loads one for engine start and one for emergency jump start.
It does seem like one battery has failed . It may be a case for returning under warranty. If that is not practical then recharge it alone on 12v charger and then use it under load (inverter) monitor voltage under load of the bad one. It is fortunate you have an apparently good one to compare. ol'will
Click to expand...

William thanks for your advice.

I've ordered parts I need to do everything properly - fuses for solar output, contact breaker for the inverter (although it has overload protection), Victron MPPT controller, Cyrix VSR , Single pole ON/OFF switches.

I've got the battery on 12V charge again this morning and it is currently around 11.5V.

While waiting for the parts to arrive I'm installing carpet on the floor panels which is heavy going in this heat.

The other thing I've done (which I thought was an absolute masters stroke) was to replace the 240V wet/dry vacuum cleaner with an 18V vacuum cleaner of the same OZITO brand. :D
 
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john_morris_uk said:
If the components really are all new, and your one 12v battery is still showing only 11.5 volts despite being on charge, I’m inclined to think you’ve got a faulty cell in that battery. Is it still under warranty?
Click to expand...

John that's the conclusion I've come to.
And since I believe it happened because of my mistake I wouldn't claim on warranty. (I sleep very well at night!):D
 
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