Monitoring lithium batteries

[Dr Bob]

16 minutes ago, peterboat said:

Tony you are wrong, I am on many sites dealing with this, some of the off grid livers do exactly what we are doing to protect and make sure the batteries have long lives, We are no problems the batteries are staying in balance if I boil a kettle the amps going back into the batteries goes up and then back down, James uses an Outback John uses a Tracer and I use a Midnite solar controller all are doing the job and we have no problems. Charging these batteries to the max shortens their life, doing what we do extends them. General Motors with its Ampera does something similar on its charging regime to protect the batteries. People on Navitron do the same, this is real people doing it for real, and I would rather copy them than some of the tripe that is on some forums, from people that have never even seen one of our batteries, never mind used one

Ok, nearly there now. Peter, can you answer the previous question I asked on the 50 mins? Is it always 50 mins despite the starting SoC of the lithiums? Does it automatically come on again once the voltage drops back below a set value?

 

14 minutes ago, peterboat said:

Exactly this Tony, as we speak I am looking at my BM2 it is showing 13.4 volts [I have just boiled a kettle] its shows 15 amps going into the batteries which given the day is correct, if it stays like this at the end of the day it will read 13.6 volts and 0 amps going in [unless the fridge kicks in

Later I have to drain down my heat exchanger it hold 140 litres of pink antifreeze deep joy?

Now I am confused again. Has the bank dropped in SoC so the voltage is less than 13.4V so the solar is now charging? If so why isnt it at 13.8V?..........or is the 13.4V just because its very cloudy today?

5 minutes ago, WotEver said:

So, because it is a low-current source, it’s currently voltage limiting to keep maximum power output and then switching off on voltage, exactly as I described earlier. Once the voltage reaches 13.8V it will switch off. 

So it has nothing to do with 50 minutes, that’s simply how long it’s taking to raise the voltage to 13.8V. 

Posts crossed.

Now that does make sense. I understand the low-current source. So, can that then be extended to an alternator or a battery charger (rather than solar) and would it work if you are getting 30A plus in from solar?

 

[WotEver]

4 minutes ago, Dr Bob said:

can that then be extended to an alternator or a battery charger (rather than solar) and would it work if you are getting 30A plus in from solar?

Not safely, no, not without integrating the monitoring of a BMS, for the reasons already explained. 

 

There is a reason that Victron and Mastervolt have developed integrated systems and why certain suppliers will not sell to DIYers. 

[Dr Bob]

43 minutes ago, WotEver said:

 

I think you’ll find that he says that HVC and LVC shouldn’t be used to switch off the charge source. They are last-resort settings. Certainly the BMS and charger should talk to each other and decide when to stop charging. Once again we’re back to a ‘system’ such as Victron’s solution. 

 

 

I fully understand this point and it is obviously one way to go. What about the DIY solution? The American does say that the charging device should be making the decisions, if I have read it correctly. It is interesting Peter and others are using charging devices not designed by the BMS manufacture (I think that is the case?). I think you have answered this in your previous posts by saying it is via low current sources.

I think I have got to where I need to be for now........ Thanks all for the inputs.

[TheBiscuits]

9 minutes ago, WotEver said:

why certain suppliers will not sell to DIYers. 

... including the manufacturers of @peterboat's batteries, Valence. They refused to sell him the external BMS unit for his secondhand batteries.

 

[smileypete]

This guy has gone for lithiums on his narrowboat:

 

https://www.youtube.com/channel/UC8bkF-v3-Foi9ps9h1D06hA

 

 

Quick summary: Much faster recharge times, efficiency, no sulphation or stratification in return for.... boatloads of cash.

 

ETA: Seems Jono was mentioned in passing at the beginning, his channel is well worth a look.

 

For those who fully understand FLA with good DIY abilities, the 'two bank' solution of FLAs might overcome the typical problems?

 

Also for lithiums maybe a 'powerwall' that's recharged by genny or travelpower is another way forward?

Edited August 10, 2018 by smileypete

[MtB]

56 minutes ago, smileypete said:

 

For those who fully understand FLA with good DIY abilities, the 'two bank' solution of FLAs might overcome the typical problems?

 

Also for lithiums maybe a 'powerwall' that's recharged by genny or travelpower is another way forward?

 

What is the 'two bank solution' exactly, please Pete? When I floated my idea of using a pair of banks here it was comprehensively demolished by several posters.

 

A 13kWhr Powerwall is £5,500 approx. Translated into 13v that is 1,038 AH of capacity. That is about half the price of conventional lithium batteries. This seems well worth investigating further.  

 

[cuthound]

11 hours ago, Mike the Boilerman said:

 

What is the 'two bank solution' exactly, please Pete? When I floated my idea of using a pair of banks here it was comprehensively demolished by several posters.

 

A 13kWhr Powerwall is £5,500 approx. Translated into 13v that is 1,038 AH of capacity. That is about half the price of conventional lithium batteries. This seems well worth investigating further.  

 

 

My understanding of the two bank system is where on set of batteries is discharged to load whilst the other set is being charged.

 

I worked on such a system at the dawn of my career. Keeps the electrons moving and thus prevents sulphation as the battery is either being charged or discharged.

 

Ideally requires change-over switches, which if to be done under load, will be sprung edge knife switches to minimise and arcs during switching.

Edited August 11, 2018 by cuthound
Missing worm

[smileypete]

1 hour ago, cuthound said:

 

My understanding of the two bank system is where on set of batteries is discharged to load whilst the other set is being charged.

 

I worked on such a system at the dawn of my career. Keeps the electrons moving and thus prevents sulphation as the battery is either being charged or discharged.

 

Ideally requires change-over switches, which if to be done under load, will be sprung edge knife switches to minimise and arcs during switching.

Yeah that's pretty much it, use one bank and charge to 85-95%, then really juice the out of use bank by charging to 100% and doing a bit of EQ. After that, just switch usage to the fully charged bank and repeat.

 

Drawbacks are needing extra space for batts, an extra bank (though a tired existing bank should do) and the biggie, it's far toooo much faffing around for most people.

 

For those with very good DIY eleccy skills, cheap(er) second user lithiums look to be a viable option when they turn up.

[TheBiscuits]

13 hours ago, Mike the Boilerman said:

A 13kWhr Powerwall is £5,500 approx. Translated into 13v that is 1,038 AH of capacity. That is about half the price of conventional lithium batteries. This seems well worth investigating further.  

Plus up to £2,800 for installation, must not be used where there is risk of flooding and the off-grid and failover backup extras are not available for use in the UK (presumably 'cos they are American electric not the proper stuff).

 

The other thing with them is you can't charge one off 12/24V so you would need a travelpower or a generator to charge it.  You might be able to charge them with a hefty inverter, but it depends how much juice they can draw when charging - it might be a lot - so you would need a 12/24V bank as well as the Powerwall.

 

I'd like one too - one self contained box with 13KWh of Lithium batteries and an inverter built in, and a heating/cooling system to extend the useable temperature range to -20C ~ 50C ( 0C ~ 30C ideal range).

 

[peterboat]

14 minutes ago, TheBiscuits said:

Plus up to £2,800 for installation, must not be used where there is risk of flooding and the off-grid and failover backup extras are not available for use in the UK (presumably 'cos they are American electric not the proper stuff).

 

The other thing with them is you can't charge one off 12/24V so you would need a travelpower or a generator to charge it.  You might be able to charge them with a hefty inverter, but it depends how much juice they can draw when charging - it might be a lot - so you would need a 12/24V bank as well as the Powerwall.

 

I'd like one too - one self contained box with 13KWh of Lithium batteries and an inverter built in, and a heating/cooling system to extend the useable temperature range to -20C ~ 50C ( 0C ~ 30C ideal range).

 

Or just buy secondhand Lifepo4s for £320 like I did and use them like I do

[TheBiscuits]

11 minutes ago, peterboat said:

Or just buy secondhand Lifepo4s for £320 like I did and use them like I do

How many did you buy Peter?  I can't remember.

[MtB]

Or just buy the Powerwall and take it to bits to get the brand new lithium cells out, for not a lot more than Pete paid for his second hand ones.

[peterboat]

4 minutes ago, TheBiscuits said:

How many did you buy Peter?  I can't remember.

14, 4 for domestic, and 10 for electric drive, I have everything for the electric drive so I will be doing it in late Sept

2 minutes ago, Mike the Boilerman said:

Or just buy the Powerwall and take it to bits to get the brand new lithium cells out, for not a lot more than Pete paid for his second hand ones.

Its to much like hard work, and my batteries were all low cycles which I checked on the puter

[TheBiscuits]

Just now, peterboat said:

14, 4 for domestic, and 10 for electric drive, I have everything for the electric drive so I will be doing it in late Sept

Your batteries:

14 x £320 = £4480.  14 x 110 Ah = 1540 Ah.  £4480 / 1540 Ah = £2.91 / Ah

 

Powerwall: (including control hardware)

£5970 / 1038 Ah = £5.75 / Ah

 

But don't forget that that the powerwall includes a (proper!) charger and BMS, and an inverter.  I just don't think Tesla will sell you one as a standalone.

 

 

 

 

[peterboat]

16 minutes ago, TheBiscuits said:

Your batteries:

14 x £320 = £4480.  14 x 110 Ah = 1540 Ah.  £4480 / 1540 Ah = £2.91 / Ah

 

Powerwall: (including control hardware)

£5970 / 1038 Ah = £5.75 / Ah

 

But don't forget that that the powerwall includes a (proper!) charger and BMS, and an inverter.  I just don't think Tesla will sell you one as a standalone.

 

 

 

 

My batteries are 138ah and each one has a BMS the inverter I have and the solar panels and MPPT controllers as well. I have no way of charging at 240 volts so my system is tailored to my needs ie 24 volt system domestic and a 60 volt system for drive.

[TheBiscuits]

Just now, peterboat said:

My batteries are 138ah and each one has a BMS the inverter I have and the solar panels and MPPT controllers as well. I have no way of charging at 240 volts so my system is tailored to my needs ie 24 volt system domestic and a 60 volt system for drive.

Your batteries:

14 x £320 = £4480.  14 x 138 Ah = 1932 Ah.  £4480 / 1932 Ah = £2.32 / Ah

 

So about half the price per Ah at 13V.  I agree that your system is great for you, and very good value for what it is, but it wouldn't do for everyone.  Keep us updated though - I am very interested in how it works out for you.

[Dr Bob]

On 09/08/2018 at 09:24, peterboat said:

My charger [midnite] is designed for the job I have a over voltage cut off if something goes wrong, James/John/me never charge to 100% yet the batteries remain balanced James has over a year of this with no issues. as Tony says if my charger only goes to 13.8 volts and its timed for 50 mins then goes to 13.6 volts it cant over charge, I know because its what I see everyday

Having spent a bit of time looking through Jono's videos of the Victron lithium kit, I am once again confused. I am sure I heard the victron kit is operating between 50 and  100% SoC on the 3 LiFePo4's Jono has. Everything I have read points to having  a strategy of operating beween say 25 and 75% as the batteries are not as happy when near 100%. Also the Victron combi and solar controller are set at 14.2V which is much higher than I had expected from Peter's charging voltage.

The victron system is also using a float charge which seems daft given they could be up at 100% charge.

 

[peterboat]

3 minutes ago, TheBiscuits said:

Your batteries:

14 x £320 = £4480.  14 x 138 Ah = 1932 Ah.  £4480 / 1932 Ah = £2.32 / Ah

 

So about half the price per Ah at 13V.  I agree that your system is great for you, and very good value for what it is, but it wouldn't do for everyone.  Keep us updated though - I am very interested in how it works out for you.

You are right the domestic side is working fine at the moment 13.3 volts is the lowest I see [BM2 connected to half the bank I already had it] the rest I still installing

2 minutes ago, Dr Bob said:

Having spent a bit of time looking through Jono's videos of the Victron lithium kit, I am once again confused. I am sure I heard the victron kit is operating between 50 and  100% SoC on the 3 LiFePo4's Jono has. Everything I have read points to having  a strategy of operating beween say 25 and 75% as the batteries are not as happy when near 100%. Also the Victron combi and solar controller are set at 14.2V which is much higher than I had expected from Peter's charging voltage.

The victron system is also using a float charge which seems daft given they could be up at 100% charge.

 

When I met Jono at West Stockworth he was operating at a similar voltage to us to prolong battery life [he is younger than me?] so wants the maximum amount of cycles from the batteries

[WotEver]

I’ve just come across some charging numbers from Relion which confirm the preceding posts...

 

If charging with a constant current source, the current should be between 0.5C and 1C but should not exceed 100A. Keep charging until the voltage reaches your desired SoC voltage (eg 14.4V). 

 

If charging with a two-stage charger (Think Bulk & Absorption) then the 1st stage should be as above, and the constant voltage part your desired SoC level (eg 14.4V) and stop charging as soon as the charge current drops to 0.05C. 

 

[Detling]

2 hours ago, WotEver said:

I’ve just come across some charging numbers from Relion which confirm the preceding posts...

 

If charging with a constant current source, the current should be between 0.5C and 1C but should not exceed 100A. Keep charging until the voltage reaches your desired SoC voltage (eg 14.4V). 

 

If charging with a two-stage charger (Think Bulk & Absorption) then the 1st stage should be as above, and the constant voltage part your desired SoC level (eg 14.4V) and stop charging as soon as the charge current drops to 0.05C. 

 

So the charger has to monitor current as well as voltage, so it can stop charging at 0.05C it also has to monitor battery temperature to reduce charging if the batteries are cold.  This could be built into a solar or mains charger but how do you get an alternator to do it. Maybe we will have to get alternator chargers with dump loads to allow the batteries to be disconnected without killing the alternator.

[peterboat]

1 hour ago, Detling said:

So the charger has to monitor current as well as voltage, so it can stop charging at 0.05C it also has to monitor battery temperature to reduce charging if the batteries are cold.  This could be built into a solar or mains charger but how do you get an alternator to do it. Maybe we will have to get alternator chargers with dump loads to allow the batteries to be disconnected without killing the alternator.

My midnite controller does this I dont charge from the alternator as in the near future I wont have an engine to do it. In the future my whispergen will do the domestic bank and this has an adjustable charging regime, Its a backup if the sun doesnt shine or its bitter cold. The domestic bank lives in the rear cabin next to the central heating pipes so being cold isnt an issue for me for the batteries. The drive batteries will live on the swim in insulated boxes to keep them warm and dry, the whispergen and the electric drive motor are both close so they might help keep them warm as well when in use. However I will only be traveling in winter if the sun is shinning so charging them shouldnt be an issue then either. Our adopted charging voltages are because charging to higher voltages can cause cell inbalence and does reduce battery life so its pointless for us three, and in practice doesnt make one iota of difference to us three that are using valence batteries.

[WotEver]

9 hours ago, Detling said:

Maybe we will have to get alternator chargers with dump loads to allow the batteries to be disconnected without killing the alternator.

That’s exactly what Jono has done. He’s paralleled up a LA battery to act as a dump load when the BMA switches off the Lithiums. With the current being low towards the end of the charge it’s possible that the alternator would survive but it’s better to be safe than sorry. 

[Robbo]

16 minutes ago, WotEver said:

That’s exactly what Jono has done. He’s paralleled up a LA battery to act as a dump load when the BMA switches off the Lithiums. With the current being low towards the end of the charge it’s possible that the alternator would survive but it’s better to be safe than sorry. 

He is using a BMS12/200 to control the alternator current to the LFP’s.   The alternator is still connected to the starter battery. The BMS12/200 also acts as a charge relay to combine both battery banks when charging. 

 

This BMS can also be added to be just a alternator current controller when combined with the other BMS Victron offer if required.  I believe this is how Jono has it setup.

Edited August 14, 2018 by Robbo

[Detling]

10 hours ago, peterboat said:

 The drive batteries will live on the swim in insulated boxes to keep them warm and dry,

Remember insulation just slows down heat transfer it does not provide heat, it also slows down the warming up heat coming in. Could you include a small loop of central heating pipe which provides a few watts of heat it only needs to keep the batteries above 0 degrees so a metre of 10mm copper pipe would probably do with insulated feed and return pipes they can all be micro bore as you don't need a massive flow rate..

[MtB]

As usually seems to happen when lithium batteries are discussed, this thread contains more heat than light (for me at least).