LFP maintaining during low load

[sailorboy1]

Those results suck

[Chotu]

Originally Posted by sailorboy1

Those results suck

I’m pretty indifferent to them. I don’t think they are good or bad.

I think I just left the inverter connected and it had a ghost or phantom load.

I don’t think the outback has one of those, does it?

[donradcliffe]

One of the boats I deliver was left at the dock with no charging sources for 18 months. The parasitic loads brought 2 of the 3 batteries down to the LVC, while the third went to the low low cutoff. Its a Mastervolt system and it was a real PITA to get the third battery back on line, but a recent report says all three are happy. The boat manager is now checking things every month.

[wholybee]

Originally Posted by sailorboy1

Today is an example the problem with this whole thread thinking, it is overcast. If it went on a few days while I was gone starting at 60% SOC would be an issue.

As most of you know, California got alot of rain this year. As luck would have it, I was out of town for 2 weeks during this time and unable to check on my boat, which I normally do once or twice a week. I do not have a shore charger, only solar. I had my charge voltage set to 13.3 ish, I don't exactly remember what. I got back to find the battery at LVD. Interestingly, it got enough sun each day to run the bilge pump if necessary (it usually is after a few days of rain) and to keep the refrigerator cold. There was something over 20 LVEs recorded in the BMS. It took about 10 days of rain before the first disconnect.

The battery is still fine, still has more than labeled capacity. It doesn't hurt the battery to run it down to LVC if cut-off voltage is set correctly. Nonetheless, I don't have the charge voltage set so low anymore. I now charge(while in "storage") to 13.8V, with no absorption time. I am no longer in the tropics, so heat isn't much a factor, and 13.8V is not quite 100%, and certainly not in the voltage range where life would be significantly affected. I have some systems running on the boat, so even in "storage" I use about 30Ah per 24hrs. So, it is also cycling a bit, and not staying at 13.8V.

[s/v Jedi]

When you are gone, there is no draw so 60% SOC is fine for at least a year or two.

Yes, disconnect the battery. Know the phantom load from the BMS… if you can’t shut it off.

[Fuss]

Originally Posted by s/v Jedi

When you are gone, there is no draw so 60% SOC is fine for at least a year or two.

Yes, disconnect the battery. Know the phantom load from the BMS… if you can’t shut it off.

What would be a good way to shut a BMS off, we don't want to start undoing things but would pulling a blade fuse work? For example on the negative sense wire, or put a switch on this wire?


I seem to remember I started a thread on this a while back but there was not a very good response.

[fxykty]

Originally Posted by Fuss

What would be a good way to shut a BMS off, we don't want to start undoing things but would pulling a blade fuse work? For example on the negative sense wire, or put a switch on this wire?


I seem to remember I started a thread on this a while back but there was not a very good response.

What does the manual for your BMS say?

Our external BMS has an on/off button on the unit and to completely remove power we can pull the fuses on its positive voltage sense wires.

[Fuss]

Originally Posted by fxykty

What does the manual for your BMS say?

Our external BMS has an on/off button on the unit and to completely remove power we can pull the fuses on its positive voltage sense wires.

I'm not sure, but probably does not mention this as the bluetooth on button or charging the battery activates the BMS from sleep mode.



I imagine that we do not want to remove 4 , 8 , 16 fuses, times however many batteries we have.


But for my BMS disconnecting the black negative sense wire should deactivate it. Of course I have not tried this and somehow someone else here must have considered this in the past?

[s/v Jedi]

Pull the balance leads plug out… or the fuses

[Statistical]

Originally Posted by Fuss

I'm not sure, but probably does not mention this as the bluetooth on button or charging the battery activates the BMS from sleep mode.



I imagine that we do not want to remove 4 , 8 , 16 fuses, times however many batteries we have.


But for my BMS disconnecting the black negative sense wire should deactivate it. Of course I have not tried this and somehow someone else here must have considered this in the past?

You could always install a switch.

If this is a custom battery in a custom enclosure and you have a battery disconnect switch you could use a double pole switch with a secondary low amperage contact for disconnecting the BMS power as well. Now the cells are just isolated cells in a box.

Blue Sea makes a battery switch with alternator field disconnect (9004) which would work. Connect battery to primary lugs and the bms power through the secondary contacts (F1 & F2).

[CaptainRivet]

Originally Posted by Fuss

What would be a good way to shut a BMS off, we don't want to start undoing things but would pulling a blade fuse work? For example on the negative sense wire, or put a switch on this wire?


I seem to remember I started a thread on this a while back but there was not a very good response.

if your install is correct just pull your main battery bank fuse and BMS should be off as well.

[CaptainRivet]

Originally Posted by Fuss

I'm not sure, but probably does not mention this as the bluetooth on button or charging the battery activates the BMS from sleep mode.



I imagine that we do not want to remove 4 , 8 , 16 fuses, times however many batteries we have.


But for my BMS disconnecting the black negative sense wire should deactivate it. Of course I have not tried this and somehow someone else here must have considered this in the past?

well you should have one main battery bank fuse that disconnects all your batteries (paralled or in series) where they are connected together.

[s/v Jedi]

Originally Posted by CaptainRivet

if your install is correct just pull your main battery bank fuse and BMS should be off as well.

The balance leads are not after the main fuse, they are from each individual cell.

[Fuss]

Originally Posted by s/v Jedi

The balance leads are not after the main fuse, they are from each individual cell.

Yes, why do we always get so much confusion, I mean, isn’t this obvious that the balance leads are in no way connected to the concept of a main fuse for the battery…as long as we keep having to defend at these levels…..dear oh dear!

[sailorboy1]

Originally Posted by Fuss

Yes, why do we always get so much confusion, I mean, isn’t this obvious that the balance leads are in no way connected to the concept of a main fuse for the battery…as long as we keep having to defend at these levels…..dear oh dear!

As the OP I wouldn't worry. Only people still posting are reading this by now in order to wage their private battle. This stuff isn't on topic at all.