Over the last couple of nights, I've picked up that my bank voltage has been dropping way too quickly, ie battery monitor states 85% SOC but bank voltage rapidly dropping towards 46V where my alarms are setup to switch over to grid.

I've found the culprit battery. Right at the end of the string on the (+) side, showing a open circuit voltage of around 10V :0

My questions now, are what is my course of action?

For the time being, can I leave the dead battery in place, and just run on grid keeping the batteries in a state of float, or should I rather remove the bank the battery is in from my setup? I suspect the latter.

Tonight I'll disconnect the bank with the bad battery, just in case.

Can I feasibly replace the dead battery with a new one of the same make/type/capacity, considering my current bank is only 6 months old, and SOC has never really gone below 80%.

Just not having much luck with batteries

35 minutes ago, viceroy said:

I've found the culprit battery. Right at the end of the string on the (+) side, showing a open circuit voltage of around 10V :0

@plonkster joking came up with a reason for this some time back. It is interesting that it is a trend that Plonky noticed since my failing battery bank it is also battery No. 1 that is failing (end of the string on the (+) side).

38 minutes ago, viceroy said:

My questions now, are what is my course of action?

Can I feasibly replace the dead battery with a new one of the same make/type/capacity, considering my current bank is only 6 months old, and SOC has never really gone below 80%.

I think one can feasibly replace that battery with a new one. (What about your warranty?). One must realise  that the battery will soon be the chemically the same age as the rest of the string but I think under the circumstances an acceptable compromise.

Contact @Chris-R and order a HA02 to mitigate any further disasters. it is money well spent. I have a HA02 on my failing bank and the HA02 is the fine thread holding the whole bank together preventing wholesale chaos.

Thanks Chris,

Once I've disconnected the bank, let the batteries rest properly and managed to check voltages on all of them I'm going to contact the battery supplier about replacement. I'm hoping they don't try put up too much fuss about it as I have full logs in terms of EmonCMS and PVoutput to show my usage patterns etc.

Funnily enough it was last week that I'd been discussing with SWAMBO about using some xmas bonus moneys to purchase some balancers and upgrade the BMV 700 to a 702.

This just makes me want to bring those plans forward somewhat.

57 minutes ago, viceroy said:

Funnily enough it was last week that I'd been discussing with SWAMBO about using some xmas bonus moneys to purchase some balancers and upgrade the BMV 700 to a 702.

If you buy a HA02 you may be able to postpone the purchase of a 702. In lieu of a 702 get some cheap digital voltmeters and permanently attach them to your batteries. If your batteries are going out of balance you will notice it late absorb when your SOC is 92-97%. Once your HA02 cannot keep your batteries balanced they are poked anyway.

1 hour ago, Chris Hobson said:

I think one can feasibly replace that battery with a new one.

I concur. At 6 months, you can get away with it. The new one will deteriorate a little faster to match the rest. A balancer should sort it out.

If you're getting a BMV... there is a new model out, the 712 :-)

16 hours ago, plonkster said:

I concur. At 6 months, you can get away with it. The new one will deteriorate a little faster to match the rest. A balancer should sort it out.

If you're getting a BMV... there is a new model out, the 712 :-)

Thanks.

I think I can survive without Bluetooth in the monitor

So update, Yesterday, I had switched the system over to grid, and just let the batteries charge up to 100% and float all day.

Yesterday afternoon, I disconnected the bank and let them rest overnight. This morning he overall bank voltage is 52.1V, and checking each individual battery, they're sitting at 13 to 13.1V, even the bad one.

Tonight, I'll add load to the bank and monitor voltages individually on each battery. Just want to make sure it's only the one bad battery. I'm also hoping in the back of my mind that they just needed a bit of a rest and recharge and will all be 100%, but I know I'm kidding myself.

8 minutes ago, viceroy said:

Yesterday afternoon, I disconnected the bank and let them rest overnight. This morning he overall bank voltage is 52.1V, and checking each individual battery, they're sitting at 13 to 13.1V, even the bad one.

My batteries do exactly the same thing but have done their time. My understanding  is that there is a sump where all the little lead flakes collect and that portion of the electrolyte becomes conductive. It can take charge and even hold charge but rapidly fails under discharge.

7 minutes ago, Chris Hobson said:

My batteries do exactly the same thing but have done their time. My understanding  is that there is a sump where all the little lead flakes collect and that portion of the electrolyte becomes conductive. It can take charge and even hold charge but rapidly fails under discharge.

Yeah, pretty sure mine are the same.

1 hour ago, viceroy said:

without Bluetooth

It's pretty handy, but I concur that unless it's competitively priced compared to the non-bt one, I would not spend extra dosh on it.

Being able to update firmware and pull stats with your cell phone is absolutely awesome. My new LFE batteries have bluetooth too (!), I can monitor individual cell voltages and temperature using my phone!

:-)

3 hours ago, plonkster said:

It's pretty handy

It's a very cool feature, but the rest of my system is pretty old school in terms of connectivity.

So I've monitored the individual voltages of each battery, and there are 2 damaged.

Battery 1 in string 1.

Battery 3 in string 2.

From about 90% SOC, the voltages on the 2 batteries rapidly starts dropping till about 85% SOC where they are getting to around 11V each and the inverters get very unhappy and want to switch to grid.

Going away for a week tomorrow, so I'll disconnect the bank completely, and decide what to do when I get back.