Lithium batteries

[Porcupine]

Just now, MtB said:

 

Excellent. Also read the battery primer I just linked to, it is full of solid gold advice. Go through it a small step at a time and post questions about anything you can't or don't understand.

 

I just have. Really useful. Thanks. 

[MtB]

1 minute ago, Porcupine said:

I just have. Really useful. Thanks. 

 

What?!!!

 

I ws expecting it to take you a week or two to fully digest and understand!! 

[Porcupine]

7 minutes ago, MtB said:

 

What?!!!

 

I ws expecting it to take you a week or two to fully digest and understand!! 

Not all of it! But I’ve got a day off work and I like reading. 

[Gybe Ho]

26 minutes ago, Porcupine said:

I think it’s the batteries too. I’ll try the battery check - what will it tell me? 

1. The test will tell us if extended engine charging times will help with your problem in the short term.
2. A post charge resting battery voltage provides a reference point for subsequent tests.
3. The fridge is a hefty consumer of electricity and gives us some idea how much strength is left in your batteries when they are delivering electricity.
4. The battery voltage after one hour of early evening usage with lights, TV, laptop ad the fridge gives us some idea of residual battery capacity. A 7pm to 11pm assessment period would be better.

The main problem you face is finding an expert at this time of year who can visit and sort you out because such an expert will be busy fielding calls from boaters in a similar predicament.

 

 

36 minutes ago, Porcupine said:

Not all of it! But I’ve got a day off work and I like reading. 

 

Since you have a day off work, is there a switch near your solar controller that can disconnect the solar panels? It will be a mechanical clunky switch.

 

If there is one you could start that test earlier. 

[Tony Brooks]

1 hour ago, MtB said:

 

We should have picked up on this before. When there is a bank of batteries in parallel, one going down drags all the others down too so your comment that one battery had failed should have been asked about and unpacked earlier. It is much more likely that all three batteries are failing together, quite possibly from undercharging.

 

 

 

Did you see that the OP said that the voltage just after dark and again in the morning while it was dark was more or less the same - 12.6V? Therefore, unless he took the morning reading in daylight when solar was producing, we should be able to rule out any shorting cells. Shorting cells is the normal single battery in a bank failure. It may well be a case of a loss of capacity across the whole bank, but then 12.6V in the morning does not exactly shout loss of capacity. I agree the charging regime needs looking at and an 8-hour plus engine charge may either solve the problem for now, or give further symptoms.

[Porcupine]

2 minutes ago, Tony Brooks said:

 

Did you see that the OP said that the voltage just after dark and again in the morning while it was dark was more or less the same - 12.6V? Therefore, unless he took the morning reading in daylight when solar was producing, we should be able to rule out any shorting cells. Shorting cells is the normal single battery in a bank failure. It may well be a case of a loss of capacity across the whole bank, but then 12.6V in the morning does not exactly shout loss of capacity. I agree the charging regime needs looking at and an 8-hour plus engine charge may either solve the problem for now, or give further symptoms.

I will try and give the engine a long run and give the batteries a really good charge. Thanks, 

[Tony Brooks]

Just now, Porcupine said:

I will try and give the engine a long run and give the batteries a really good charge. Thanks, 

 

Check the batteries every so often for local hot spots on the top and also for nasty smells. Both will indicate shorting cells.

 

While you are at it look at the ends of the batteries, if any have bowed out a bit then that tells you they are sulphated.

[Porcupine]

1 minute ago, Tony Brooks said:

 

Check the batteries every so often for local hot spots on the top and also for nasty smells. Both will indicate shorting cells.

 

While you are at it look at the ends of the batteries, if any have bowed out a bit then that tells you they are sulphated.

Great, I’ll keep an eye out for those symptoms. 

[blackrose]

I didn't want to start a new thread so thought I'd post my question on the back of this one:

 

My two Fogstar drift lithium batteries are due to be delivered mid-January, but someone at my mooring who fitted his about 8 months ago told me that Fogstar told him to charge each battery independently and fully before installing them.

 

I don't really understand this. Is it something to do with balancing lithiums which I also keep hearing about? I don't really understand that either. If I fit two lithium batteries in parallel haven't I effectively created one bigger battery? Why would they need charging independently or balancing?

[magnetman]

They are supplied in a partly discharged state. I think it is to do with safety. Less energy to be released. Like with cars on transporters which have very low fuel levels. 

 

So you need to charge it to 100% when you first get it. 

 

 

I think the transport charge level is something like 30% but not sure. 

 

 

[Russ T]

Or maybe less of a voltage gradient so reduced sparking. 

8 minutes ago, blackrose said:

I didn't want to start a new thread so thought I'd post my question on the back of this one:

 

My two Fogstar drift lithium batteries are due to be delivered mid-January, but someone at my mooring who fitted his about 8 months ago told me that Fogstar told him to charge each battery independently and fully before installing them.

 

I don't really understand this. Is it something to do with balancing lithiums which I also keep hearing about? I don't really understand that either. If I fit two lithium batteries in parallel haven't I effectively created one bigger battery? Why would they need charging independently or balancing?

The batteries should already be balanced before they are shipped, so should not be of any concern. The BMS has probably got a balancing ability built in too.

[magnetman]

Top balance ? It could be to set the SoC meter which might have drifted during storage due to the BMS pulling small currents continuously. 

[IanD]

8 minutes ago, Rod Stewart said:

Or maybe less of a voltage gradient so reduced sparking. 

The batteries should already be balanced before they are shipped, so should not be of any concern. The BMS has probably got a balancing ability built in too.

Connecting two LFP batteries together which are at different voltages can lead to high currents due to low series resistance. They should both be charged to the *same* voltage before doing this -- it doesn't really matter what that voltage is. If the voltages are already very close (within 10mV?) then they can be connected together straight away.

 

They should then be charged up to 100% SoC (14.4V for Fogstar?) and kept there for at least 30mins (check Fogstar recommendation) to allow them to top balance and to reset the SoC counter. Then STOP CHARGING.

 

Or you could do this first -- separately for each -- and then connect them together, which is what seems to have been suggested.

Edited December 31, 2024 by IanD

[magnetman]

Also does Fogstar charge all the blocks they make or are they just assembling cells shipping from China into boxes. The individual cells will certainly not be shipped charged. 

[dmr]

2 minutes ago, Rod Stewart said:

Or maybe less of a voltage gradient so reduced sparking. 

The batteries should already be balanced before they are shipped, so should not be of any concern. The BMS has probably got a balancing ability built in too.

 

I think the issue is battary balance rather than cell balance, can you be sure that the two batteries have the same state of charge before you connect them in parallel?  don't want a huge current flow. I have thought about initially connecting two batteries vis a low value resistor (0.1ohm?) for a few hours.  What do the experts (and others 😀) think?

[Russ T]

Just now, magnetman said:

Top balance ? It could be to set the SoC meter which might have drifted during storage due to the BMS pulling small currents continuously. 

The individual cells should be top balanced when the batteries are assembled. That is what I did to mine anyway.

[magnetman]

But they might all be at a very closely matched voltage. Within 10mV I think is the recommendation. 

 

 

[Russ T]

Just now, dmr said:

 

I think the issue is battary balance rather than cell balance, can you be sure that the two batteries have the same state of charge before you connect them in parallel?  don't want a huge current flow. I have thought about initially connecting two batteries vis a low value resistor (0.1ohm?) for a few hours.  What do the experts (and others 😀) think?

I certainly use the resistor method when connecting a big inverter. I'm no expert though, so refrain from commenting.

[magnetman]

Just now, Rod Stewart said:

The individual cells should be top balanced when the batteries are assembled. That is what I did to mine anyway.

Yes but do Fogstar do that or arrr they constructing battery blocks from partly charged very well matched cells...

 

[Russ T]

Just now, magnetman said:

Yes but do Fogstar do that or arrr they constructing battery blocks from partly charged very well matched cells...

 

I can't imagine they are shipped unbalanced. That would cause no end of problems.

[magnetman]

Whether they then charge them fully then partly discharge them for stirage and/or transport seems an interesting question.

 

I think they would not need to do that. 

 

 

Just now, Rod Stewart said:

I can't imagine they are shipped unbalanced. That would cause no end of problems.

The customer is advised to fully charge on receipt of the product. Fully charging will cause the balancing circuit to operate .. Maybe that is why the advice exists 

1 minute ago, Rod Stewart said:

 unbalanced. 

They would not be unbalanced if they were properly matched cells. 

 

 

[Russ T]

1 minute ago, magnetman said:

The customer is advised to fully charge on receipt of the product. Fully charging will cause the balancing circuit to operate .. Maybe that is why the advice exists 

Yes, possibly, but hopefully they have already been balanced at assembly like what I previously said.I spent days balancing mine with an external power supply.

[magnetman]

 

It seems to be a considerable time saving if you don't need to individually charge and discharge every single battery block you are selling. Let the customer do it. 

 

 

Just now, Rod Stewart said:

Yes, possibly, but hopefully they have already been balanced at assembly like what I previously said.I spent days balancing mine with an external power supply.

Were yours well matched when you got them? Its possible that the EVE geysers are selling properly matched cells whereas it you get yellow ones they might have widely differing voltages. 

 

 

[IanD]

2 minutes ago, Rod Stewart said:

I can't imagine they are shipped unbalanced. That would cause no end of problems.

If you're building a large number of batteries, it's easy to use cells from one manufacturing/shipping batch, and -- if you can be bothered -- sort them into sets with matched voltages before assembing the pack. It's unlikely they'd then bother fully charging them to 100% SoC and balancing them, and then discharging then back to ~50% SoC for shipping (which is how they say they're shipped) -- too much time/effort/cost.

[Russ T]

1 minute ago, IanD said:

If you're building a large number of batteries, it's easy to use cells from one manufacturing/shipping batch, and -- if you can be bothered -- sort them into sets with matched voltages before assembing the pack. It's unlikely they'd then bother fully charging them to 100% SoC and balancing them, and then discharging then back to ~50% SoC for shipping (which is how they say they're shipped) -- too much time/effort/cost.

Oh. I'm quite surprised by that. When I was looking into it, I spent many days reading and actually balancing my cells. At the time I was under the impression that leaving the BMS to try and balance them would simply not work, and that all cells matched by production batch, resistance and voltage whilst preferable is not a substitute for top balancing. Perhaps things have changed?