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Another Lithium battery thread


Dr Bob

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3 hours ago, MoominPapa said:

 

I'll try and put something down this evening.

 

On question 3), what are the outputs you're trying to combine. Active high or active low voltages, volt-free contacts, contact closures to ground?. Also what sort of signal does the BEP switch want?

 

MP.

 

 

1 hour ago, Dr Bob said:

I will have a few devices that have alarm and relay functions ie the BMV 712.  Each has a +ve and -ve connection to activate an external relay. For a normal relay, connect the coil to the connections with a 12v supply and when the alarm goes off the circuit closes so energises the coil. Can I parallel two or three 'activation' devices to just one relay?

I've ordered the BEP switch so I will work out what connection it wants when it arrives. The diagram on the info sheet on the net is not much help.

So... to ground then, yes?

 

If so, yes you can parallel them. 

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A lot of new posts since I last looked! If I miss anything anyone wanted a specific reply to give me a nudge. 

On 01/02/2019 at 10:51, Dr Bob said:

I am getting very confused with all of these 'good for LifePo'  claims!

 The bumf on this charger says for LifePo bulk charging to 14.6v and a float of 14.4V. WTF!!!!!!!

How can you trust this info!

 You need to take charger profiles labelled as LiFePo4 with a pinch of salt. Most have way to high voltages. I think this is because they are designed to interface with a proprietary system with built in bms. Alternatively they just want you to keep replacing their expensive batteries on a regular basis? Ideally you need equipment with fully customisable voltage settings for charging LiFePo4. 

 

On 01/02/2019 at 10:57, Dr Bob said:

looking for an MPPT that can cope with 40A max.

I use the Tracer MPPT with display. This has customisable settings for voltage and absorption time etc. Just remember if charging from solar (or any other source), to disable temperature compensation (some solar controllers and other charge sources still have this even if no external temp sensor fitted).

 

On 01/02/2019 at 12:39, Dr Bob said:

I am relying only on one temperature audible alarm and disconnect though

I don't think temperature is as big an issue as some make it out to be. Providing you are not pushing at the very extreme limit of charging, it is highly unlikely they will even get warm let alone hot. If on the boat in freezing temps then unlikely the batteries will be at or below freezing, and if away unlikely they will receive much if any charge in freezing conditions - it would have to be a prolonged freezing spell to get much below freezing inside the boat. 

 

On 01/02/2019 at 12:39, Dr Bob said:

plan is to maximise charging via the solar and isolate from the alternator (manually) when the engine is running. I will therefore change the Solar input from the MPPTs to the Lithium side of the manual isolation switch. In the morning I will turn the manual isolation switch off so the Lithiums are only charged by the solar.

By doing this you lose one of the big advantages of lithiums which is fast charging from the alternator. What about a voltage sensitive switch as linked to earlier, set to disconnect from alternator at 14.0v?

 

Also may be worth having a switch to manually disconnect solar if lithiums are fairly well charged and you're leaving the boat for a while. 

 

On 01/02/2019 at 12:39, Dr Bob said:

Both the Aus unit and the BMV 712 have relay outputs (I assume they just close a circuit?). I am thinking of using the BEP 701 mn motorised switch as it seems easy to wire

The BMV just has a standard relay that closes in alarm state (can be set to open if you change settings but uses more power). The Aus unit has solid state relays built in (one for high and one for low voltage) that from memory are closed in normal operation but open in fault conditions. These can be wired together to give one output. 

 

BEP 701 motorised switch just needs a permanent -ve, and a switched -ve to turn on and off. When switch wire is connected to -ve switch turns on, and when disconnected switch turns off. 

 

On 01/02/2019 at 12:39, Dr Bob said:

but how would I wire in one of these latching relays?

This is slightly more tricky! I've used one of these for high voltage disconnect (charge bus). There is a circuit here but having tried to build it, I was only able to get one output working correctly (probably made an error somewhere). In the end went for the simpler but more expensive option - the Rec BMS bistable relay driver, available here and here. Was surprised not to be able to find anything else commercially. 

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49 minutes ago, Tom and Bex said:

There is a circuit here but having tried to build it, I was only able to get one output working correctly (probably made an error somewhere)

Have you seen the note that Q2 is shown with C & E transposed?

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1 hour ago, Tom and Bex said:

?

By doing this you lose one of the big advantages of lithiums which is fast charging from the alternator. What about a voltage sensitive switch as linked to earlier, set to disconnect from alternator at 14.0v?

 

 

Tom, thanks for all the comments. On board with all of them.

On the alternator, yes it would be straightfoward to cut the feed at 14.0V but I am more worried about the  high duty on the alternator and it get too hot. I will try it and keep a close eye on voltage and temperature.

 

1 hour ago, Tom and Bex said:

?

The BMV just has a standard relay that closes in alarm state (can be set to open if you change settings but uses more power). The Aus unit has solid state relays built in (one for high and one for low voltage) that from memory are closed in normal operation but open in fault conditions. These can be wired together to give one output. 

 

BEP 701 motorised switch just needs a permanent -ve, and a switched -ve to turn on and off. When switch wire is connected to -ve switch turns on, and when disconnected switch turns off. 

 

This is slightly more tricky! I've used one of these for high voltage disconnect (charge bus). There is a circuit here but having tried to build it, I was only able to get one output working correctly (probably made an error somewhere). In the end went for the simpler but more expensive option - the Rec BMS bistable relay driver, available here and here. Was surprised not to be able to find anything else commercially. 

I will understand better when I get the BEP 701 on Thursday...I hope.?

Ok, the diy circuits for latching will be beyond me but the commercial one looks interesting. Did you get one of those to manage your Tyco relay? I am thinking of adding an extra auto disconnect  to be contolled on overvoltage of the full Li bank (from the BMV 712) so I have separate ways of disconnecting.

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On 01/02/2019 at 12:57, WotEver said:

 Automate everything is my advice.

This! The less user intervention required the better. 

 

On 02/02/2019 at 14:53, Dr Bob said:

A few questions:

1) Can I activate the auto disconnect (the BEP motorised switch) via two relay sources...ie the green dotted lines on the diagram (and maybe a 3rd relay source if I fit a temperature control board)?

Yes, although you may have to reverse the relay operation in the BMV. 

 

On 02/02/2019 at 14:53, Dr Bob said:

2) Could I use a Tyco latching relay (below) instead of the BEP motorised switch without a complicated circuit if it doesnt need to auto reset, ie in the event of an emergency disconnect, I want to manually reset it. Can someone come up with a circuit I could use for this?

See my earlier reply for control options, although if only wanting disconnect, MP might come up with simpler circuit. 

 

On 02/02/2019 at 14:53, Dr Bob said:

3) The idea of piggybacking the Li's onto the LA circuit (in the first post in this thread) looks good to protect charging devices in the event of emergency disconnect. Is there though an issue on reconnection if the LA bank is at low SOC (it shouldnt be...... but if it is?). Would too much current flow from the Li bank to the LA bank?

Can't see this being a big problem. Lithiums would only be at 13.5v or so, so not sure how much current would actually flow. Certainly won't damage the lithiums. 

 

One issue I can see with your diagram is the BMV (1) is wired to monitor the total system. This will work well for seeing voltage and amps in the whole system, but will be virtually impossible to set up for meaningful SOC readings due to the completely different characteristics of the two banks. 

 

7 hours ago, rusty69 said:

What are the main safety concerns with these batteries compared to LA. What are their failure mode, are they likely to catch fire and set light to my bed. Are there any insurance company issues installing a home brew lithium power source?  Are they likely to be covered in the boat safety scheme in the future?

As already stated, LiFePo4 is a very safe technology, and unlike the lithium batteries found on mobile devices, are not likely to spontaneously burst into flames if overcharged! The worst that might happen is they might swell a bit, and if significantly overcharged, might vent some electrolyte. 

 

LA batteries have their own safety issues, and pose a possible explosion risk if overcharged and the hydrogen gets ignited. 

 

As to bss, the usual battery precautions and requirements apply. With lithiums it's important to protect the terminals by using insulated cover or other means. They generally have more exposed terminals, and more delicate wiring (monitoring, bms etc). They can produce many times more current than LA's in event of short circuit (e.g. dropped tools etc), and for longer!

 

6 hours ago, Dr Bob said:

Another issue on boats is the physical strength of the batteries. On a NB, the demand is not high but I can see 'fragile' Lithiums on a lumpy water boat getting exposed to lots of vibration and bangs

I'm sure I read somewhere (although can't remember where!) that at least one cell manufacturer recommended a max cell size of 200ah for marine use as larger cells were more at risk of structural failure due to vibration. 

 

4 hours ago, MoominPapa said:

 

On question 3), what are the outputs you're trying to combine. Active high or active low voltages, volt-free contacts, contact closures to ground?. Also what sort of signal does the BEP switch want?

The BEP switch needs a switched -ve. input -ve = switch on, input open = switch off. 

2 hours ago, Dr Bob said:

I will have a few devices that have alarm and relay functions ie the BMV 712.  Each has a +ve and -ve connection to activate an external relay. For a normal relay, connect the coil to the connections with a 12v supply and when the alarm goes off the circuit closes so energises the coil. Can I parallel two or three 'activation' devices to just one relay?

I've ordered the BEP switch so I will work out what connection it wants when it arrives.

I think the problem may come from the fact the BMV has relay contacts that are NO unless in alarm state, whereas the Aus BMS has solid state relays that are NC unless fault detected. 

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50 minutes ago, WotEver said:

Have you seen the note that Q2 is shown with C & E transposed?

Yes, couldn't get it to work at all at first, but after a couple email exchanges he noticed the mistake! I ran out of time to trace the other fault so went with the commercial option in the end. Sure it was to do with my circuit building though?

 

17 minutes ago, Dr Bob said:

Did you get one of those to manage your Tyco relay?

 Yes, that's the one I went for in the end. 

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44 minutes ago, Tom and Bex said:

This! The less user intervention required the better. 

 

Yes, although you may have to reverse the relay operation in the BMV. 

 

See my earlier reply for control options, although if only wanting disconnect, MP might come up with simpler circuit. 

 

Can't see this being a big problem. Lithiums would only be at 13.5v or so, so not sure how much current would actually flow. Certainly won't damage the lithiums. 

 

One issue I can see with your diagram is the BMV (1) is wired to monitor the total system. This will work well for seeing voltage and amps in the whole system, but will be virtually impossible to set up for meaningful SOC readings due to the completely different characteristics of the two banks. 

 

As already stated, LiFePo4 is a very safe technology, and unlike the lithium batteries found on mobile devices, are not likely to spontaneously burst into flames if overcharged! The worst that might happen is they might swell a bit, and if significantly overcharged, might vent some electrolyte. 

 

LA batteries have their own safety issues, and pose a possible explosion risk if overcharged and the hydrogen gets ignited. 

 

As to bss, the usual battery precautions and requirements apply. With lithiums it's important to protect the terminals by using insulated cover or other means. They generally have more exposed terminals, and more delicate wiring (monitoring, bms etc). They can produce many times more current than LA's in event of short circuit (e.g. dropped tools etc), and for longer!

 

I'm sure I read somewhere (although can't remember where!) that at least one cell manufacturer recommended a max cell size of 200ah for marine use as larger cells were more at risk of structural failure due to vibration. 

 

The BEP switch needs a switched -ve. input -ve = switch on, input open = switch off. 

I think the problem may come from the fact the BMV has relay contacts that are NO unless in alarm state, whereas the Aus BMS has solid state relays that are NC unless fault detected. 

I am so glad my charging is by solar so is easy to control, my drive batteries have a control board which also controls charging by disconnect relay and undercharge which gives me some added protection from destroying the batteries. My Valence batteries were originally designed for a minisub, so are marine compliant for insurance, how important that is in a widebeam I have no idea.

I am at the moment having fun and games making the whole thing safe with the terminals, its a wood lined metal box with wood lid at the moment and covers on everything else, fingers crossed the BSS agrees

Edited by peterboat
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2 hours ago, Tom and Bex said:

A lot of new posts since I last looked! If I miss anything anyone wanted a specific reply to give me a nudge. 

 You need to take charger profiles labelled as LiFePo4 with a pinch of salt. Most have way to high voltages. I think this is because they are designed to interface with a proprietary system with built in bms. Alternatively they just want you to keep replacing their expensive batteries on a regular basis? Ideally you need equipment with fully customisable voltage settings for charging LiFePo4. 

 

I use the Tracer MPPT with display. This has customisable settings for voltage and absorption time etc. Just remember if charging from solar (or any other source), to disable temperature compensation (some solar controllers and other charge sources still have this even if no external temp sensor fitted).

 

I don't think temperature is as big an issue as some make it out to be. Providing you are not pushing at the very extreme limit of charging, it is highly unlikely they will even get warm let alone hot. If on the boat in freezing temps then unlikely the batteries will be at or below freezing, and if away unlikely they will receive much if any charge in freezing conditions - it would have to be a prolonged freezing spell to get much below freezing inside the boat. 

 

 

I have Ctec battery charger for the domestic 24volt bank, it charges up to 27.2 then drops 26.8 as yet through this winter it has been no problem in conjunction with the solar which will take it up to 27.6. I have noticed that this cold weekend with me not on the boat, and the fridge freezer turned up high that solar was struggling to charge my batteries at very cold temps. As soon as the heating was fired up the hot pipes running through the battery box sorted charging out. The drive batteries will have warm air from the motor ducted through them to keep them warmer to help them out. James tries to keep his at 20 degrees c to help them perform to their best, says it makes a difference

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2 hours ago, Dr Bob said:

Tom, thanks for all the comments. On board with all of them.

On the alternator, yes it would be straightfoward to cut the feed at 14.0V but I am more worried about the  high duty on the alternator and it get too hot. I will try it and keep a close eye on voltage and temperature.

 

I will understand better when I get the BEP 701 on Thursday...I hope.?

Ok, the diy circuits for latching will be beyond me but the commercial one looks interesting. Did you get one of those to manage your Tyco relay? I am thinking of adding an extra auto disconnect  to be contolled on overvoltage of the full Li bank (from the BMV 712) so I have separate ways of disconnecting.

If the circuit Tom linked to is beyond you, then my design is likely to be also. It does the same sort of thing, but uses CMOS logic ICs rather than discrete transistors.

 

MP.

 

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Under bed operations complete, and battery covers all in place. The wires are the USB cable to the Arduino, and a remote reset switch, as it's necessary to be able to reset the processor to upload new code.

 

Second photo is after the usual junk has been returned to the under-bed space :)

 

Third photo is control panel. The new BMS interface is the dial on the right.

 

MP.

 

 

 

 

 

IMG_20190204_141822633.jpg

IMG_20190204_144721691.jpg

IMG_20190201_170540284.jpg

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  • 2 weeks later...

An update.

 

The first time I charged the battery,  it was obvious that is was well out of balance. The supplier kind-of implied that it had been balanced, and the cell voltages were all close, so I believed him. Resting cell voltages don't tell you anything much. What happened was that the first time I fully charged the battery, one cell (the one with most charge) hit full first, climbed the "hockey stick" portion of the charge-voltage curve and tripped cell over-voltage well before the whole battery charge-termination conditions were reached. This is a very good illustration of why cell-level voltage monitoring is necessary.

 

I considered breaking down the installation, connecting all 12 cells in parallel and doing  a balancing charge, but that seemed like a whole lot of work, and lots of risky wiring with possibility of shorts. Instead, I took advantage of the fact that the system makes comprehensive logs, so it was easy to see which cells were out a balance and by how much. I added a BMS function to allow me to tell it to remove x Ah from cell y, using the built-in balancing system. This is quite slow: it can only balance by about 3Ah per day, so it's taken some time. I adopted the approach of charging the battery once per day. Noting what cells started to rise first as SOC approached 100%, and telling the BMS to balance those whilst we ran the boat from the bank for the rest of the day. Next morning I charged again and repeated the process. After two iterations, the charge started ending with the correct charge termination conditions (voltage > 13,9, current < C/20) rather than cell over voltage, but it's taken almost a week to get the balance right. 

 

Fortunately, this morning it was correct, as we've left out winter mooring today, so no longer have the mains power that I was using to do this routine.

 

The software continues to need tweaking, Almost every case where action is taken when a voltage or current crosses a threshold has needed to be re-coded to check that the  threshold is crossed for a minimum time, typically a few seconds to a minute. Otherwise noise can cause the odd rogue reading to trip a state-change long before it should happen.

 

I also noted today that once the charge is terminated, when the engine is stopped and restarted, charge starts again and another few Ah gets put in before the charge termination conditions are reached again. I've coded something which waits until the battery has been discharged at least 10Ah from full before allowing recharge, to avoid this.

 

We're now using the battery for real, so we'll see how it goes. First indications are good: The charge efficiency is indistinguishable from 100% given the accuracy of my current measurement and integration. It's extraordinary to watch the charge current pegged to the maximum the alternator can provide until the SOC is beyond 99%.

 

Main lesson is that, if using the bare cells, you really do need per-cell voltage monitoring, and most likely also at least an alarm for cell overvoltage or undervoltage, Lack of balance can easily lead to one cell getting overcharged even if the whole battery is still well inside the 14v cut-off.

 

MP.

 

 

 

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8 hours ago, MoominPapa said:

I considered breaking down the installation, connecting all 12 cells in parallel and doing  a balancing charge, but that seemed like a whole lot of work, and lots of risky wiring with possibility of shorts. Instead, I took advantage of the fact that the system makes comprehensive logs, so it was easy to see which cells were out a balance and by how much. I added a BMS function to allow me to tell it to remove x Ah from cell y, using the built-in balancing system. This is quite slow: it can only balance by about 3Ah per day, so it's taken some time. I adopted the approach of charging the battery once per day. Noting what cells started to rise first as SOC approached 100%, and telling the BMS to balance those whilst we ran the boat from the bank for the rest of the day. Next morning I charged again and repeated the process. After two iterations, the charge started ending with the correct charge termination conditions (voltage > 13,9, current < C/20) rather than cell over voltage, but it's taken almost a week to get the balance right.

 

MP.

 

 

 

Great info MP.

You were balancing by about 3Ahr per day. From the previous figs you gave me (ie a high cell voltage of 3.65V with the other 3 cells at 3.4V) what do you think the total inbalance was that you had to correct ....in Ahrs? When I get mine, I was going to try and do it manually with a 10A load to speed things up. Using my limited ohms law experience, I calculate that using a 300 milliohm wire wound resistor across the 3.3V battery terminals will give me around 10A load (30W). Maybe even double this up with 2* 600 milliohm resistors (that's the right way round isnt it?) to get a bit more power.

You were worried about connecting them up in parallel. Isnt this just a matter of changing the copper bus bar connectors and having one cell voltage wire - or was the layout such that you needed to make up lots of jumper wires? I'll be getting the same layout of batteries as you. From reading all the articles, its looks like even if you connect all in parallel, it still takes hours/days to bring them together. I know T&B did it this way.

Keep us posted.

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1 hour ago, Dr Bob said:

Great info MP.

You were balancing by about 3Ahr per day. From the previous figs you gave me (ie a high cell voltage of 3.65V with the other 3 cells at 3.4V) what do you think the total inbalance was that you had to correct ....in Ahrs? When I get mine, I was going to try and do it manually with a 10A load to speed things up. Using my limited ohms law experience, I calculate that using a 300 milliohm wire wound resistor across the 3.3V battery terminals will give me around 10A load (30W). Maybe even double this up with 2* 600 milliohm resistors (that's the right way round isnt it?) to get a bit more power.

You were worried about connecting them up in parallel. Isnt this just a matter of changing the copper bus bar connectors and having one cell voltage wire - or was the layout such that you needed to make up lots of jumper wires? I'll be getting the same layout of batteries as you. From reading all the articles, its looks like even if you connect all in parallel, it still takes hours/days to bring them together. I know T&B did it this way.

Keep us posted.

 

My estimate of imbalance was as based more on time. I looked in the logs at when the high cell started the fast "hockey stick" voltage climb at the end of charging, relative to the others. For the first  couple of charges, this only gave a lower bound, as the other cells didn't start to climb at all. Once I had it sufficiently in balance that I could see the other cells starting to climb before the charge ended, I could look at the time difference between when the first high one started to go up, and when the others did, Multiply that by the charge current, and that gives you the number of Ah to remove from the high cell. My guesstimate came out at around 20, but that's pretty rough. As I was iterating and testing, that's not a problem. I have the formerly high cell the same as another two now, I think that the the fourth is still down a bit, so could probably do with taking a bit more off the top three to balance them to that. As I don't intend to visit the highly-discharged region, where the single low cell will hit the low voltage first, I'm not too bothered about that.

 

The worry about connecting in parallel was precisely the jumper wire thing. For 3P4s, the cells are blocked together with three in one direction and three in the other, so you can't just link them all with straps, and anyway I didn't have any extra straps. I have a load of battery jumper cables from the old installation, but the idea of trying to bolt those on without losing control of any free ends was a bit scary.

 

Your ohms law looks right, but note that a 300m-ohm 30W resistor is quite a beast, and may not be easy to acquire.

 

Just connecting in parallel either takes a very long time, or doesn't work at all, depending on who you believe. You need to charge them in parallel, and for that you need a voltage adjustable, stabiliised, current limited power supply. I did buy such a thing for this project, and in hindsight I should have used it before I installed the cells.

 

MP

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10 hours ago, MoominPapa said:

An update.

 

The first time I charged the battery,  it was obvious that is was well out of balance. The supplier kind-of implied that it had been balanced, and the cell voltages were all close, so I believed him. Resting cell voltages don't tell you anything much. What happened was that the first time I fully charged the battery, one cell (the one with most charge) hit full first, climbed the "hockey stick" portion of the charge-voltage curve and tripped cell over-voltage well before the whole battery charge-termination conditions were reached. This is a very good illustration of why cell-level voltage monitoring is necessary.

 

I considered breaking down the installation, connecting all 12 cells in parallel and doing  a balancing charge, but that seemed like a whole lot of work, and lots of risky wiring with possibility of shorts. Instead, I took advantage of the fact that the system makes comprehensive logs, so it was easy to see which cells were out a balance and by how much. I added a BMS function to allow me to tell it to remove x Ah from cell y, using the built-in balancing system. This is quite slow: it can only balance by about 3Ah per day, so it's taken some time. I adopted the approach of charging the battery once per day. Noting what cells started to rise first as SOC approached 100%, and telling the BMS to balance those whilst we ran the boat from the bank for the rest of the day. Next morning I charged again and repeated the process. After two iterations, the charge started ending with the correct charge termination conditions (voltage > 13,9, current < C/20) rather than cell over voltage, but it's taken almost a week to get the balance right. 

 

Fortunately, this morning it was correct, as we've left out winter mooring today, so no longer have the mains power that I was using to do this routine.

 

The software continues to need tweaking, Almost every case where action is taken when a voltage or current crosses a threshold has needed to be re-coded to check that the  threshold is crossed for a minimum time, typically a few seconds to a minute. Otherwise noise can cause the odd rogue reading to trip a state-change long before it should happen.

 

I also noted today that once the charge is terminated, when the engine is stopped and restarted, charge starts again and another few Ah gets put in before the charge termination conditions are reached again. I've coded something which waits until the battery has been discharged at least 10Ah from full before allowing recharge, to avoid this.

 

We're now using the battery for real, so we'll see how it goes. First indications are good: The charge efficiency is indistinguishable from 100% given the accuracy of my current measurement and integration. It's extraordinary to watch the charge current pegged to the maximum the alternator can provide until the SOC is beyond 99%.

 

Main lesson is that, if using the bare cells, you really do need per-cell voltage monitoring, and most likely also at least an alarm for cell overvoltage or undervoltage, Lack of balance can easily lead to one cell getting overcharged even if the whole battery is still well inside the 14v cut-off.

 

MP.

 

 

 

You are always supposed to individually charge the batteries, then put them in parallel, charge them again after 24 hours, then connect into series if that is how you are going to use them. I have mentioned this in the past, and its what I did with my drive batteries all ten off them

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Yes, my cells were not as well balanced as the supplier suggested they might be. It's certainly interesting just how quickly and how high the voltage can rise on an unbalanced cell, yet still easily remain within max overall voltage. Mine are still not quite as perfectly balanced as I might like, but perfectly ok to use, and haven't varied in use. Need to keep a close eye on cell voltages during initial charge though as when hitting the knee it can rise surprisingly quickly!

 

I balanced mine initially by connecting cells in parallel, and charging until voltage was around 3.6v. I probably should have taken them a little higher, as a couple needed a further top up after installation. Both the initially parallel charge, and subsequent individual top up was performed manually using a standard sterling 12v charger, but with voltages very closely monitored - as discussed towards the end off this article in method 2: charging and balancing cells on board.

 

Definitely worth spending the extra time to get the balancie correct, particularly if you don't have active balancing as part of the BMS. This stage requires patience and concentration if doing it manually, and can't be rushed!

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  • 2 weeks later...

I picked up my 12 Thundersky cells today and they are now on the boat. Set up in a 3P 4S configuration and Jeremy said he put them all in parrallel and charged them to 3.5V so maybe they are reasonably balanced.

I now need to scope out where they are going and where to put all the gubbins that I need.

Likely to start installation in a few weeks (need a few more bits) and have it all finished by mid March.

I'll keep you posted.

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10 hours ago, Dr Bob said:

I picked up my 12 Thundersky cells today and they are now on the boat. Set up in a 3P 4S configuration and Jeremy said he put them all in parrallel and charged them to 3.5V so maybe they are reasonably balanced.

I now need to scope out where they are going and where to put all the gubbins that I need.

Likely to start installation in a few weeks (need a few more bits) and have it all finished by mid March.

I'll keep you posted.

If Jeremy didn't discharge them after the balancing charge, it might be worth hooking up a couple of big light bulbs across the bank now, for a few hours, rather than storing them at 100% SOC 'till you get around to the installation.

 

We've left shore power behind, so we're living off our new bank. First impressions are very favourable.

 

MP.

 

 

 

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8 minutes ago, MoominPapa said:

If Jeremy didn't discharge them after the balancing charge, it might be worth hooking up a couple of big light bulbs across the bank now, for a few hours, rather than storing them at 100% SOC 'till you get around to the installation.

 

We've left shore power behind, so we're living off our new bank. First impressions are very favourable.

 

MP.

 

 

 

Yes, I will try and sort that today. He only took them to 3.5V so now they are sitting at 3.32V. I would guess therefore they are at <95% SoC but I will put a load on them today/tomorrow to take them down a bit more.

I'll keep you posted.

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well lads, that was quite a read. Impressive work from the sounds of it. Having mortally wounded my 6 T-105s within 3.5 years and the cost of like for like replacement looking like ~ £900, lithium is a definite consideration. Especially as I'm a CC so never-ever have shoreline.

 

Cheers to all the contributors for an excellent on topic thread.

 

Now I need to try and make sense of it all and draft up a circuit diagram & shopping list 

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2 hours ago, sirweste said:

well lads, that was quite a read. Impressive work from the sounds of it. Having mortally wounded my 6 T-105s within 3.5 years and the cost of like for like replacement looking like ~ £900, lithium is a definite consideration. Especially as I'm a CC so never-ever have shoreline.

 

Cheers to all the contributors for an excellent on topic thread.

 

Now I need to try and make sense of it all and draft up a circuit diagram & shopping list 

I now have all the bits together and will start intallation on the weekend.

I spent £1000 on the batteries and around £750 on the bits I needed for the install.

Batteries are 480Ahr (when new) 3P 4S, as per MP's system. You could reduce the £1000 by 33% if you went for 320Ahrs ie 2P 4S, as T&B have got........assuming Jeremy doesnt put his prices up (which he may do with all this boaty interest!)

The install bits,  I have gone a bit over the top and it could be done a lot cheaper. I bought an extra BMV 712 (plus temp probe) for £220 and a BEP motorised switch for £150. You could probably replace those two with £100 by going for cheaper components. The cabling cost nearly £100. I have left my current LA circuits in place so had to buy all new stuff. If replacing the LA's that will save money on cabling, meters etc. I'm sure you could get a system in place for £1200 total if going for 320Ahrs.

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2 hours ago, MoominPapa said:

Just starting day three moored under the trees at Market Harborough (so no solar to speak of)  No engine running either. Will be no sweat staying 'till tomorrow.

 

I like these batteries.

 

MP.

 

You could make some pocket money installing these

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My immediate plan is to get into a marina (eeerrrghhhh) for a few weeks and slam the T-105s with many equalise cycles. But when that doesn't revive them (like MPs current situation I used to be able to go 2 days before doing a recharge) I'll be popping my plans up on here.

Thanks again for a great thread

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