Cheap LiFePO4 BMS?

[nicknorman]

Not sure how interested folk are in my tinkering so reading this is optional! I got my mk2 BMS boards back from china several weeks ago but have been preoccupied with the alternator regulator. Finally got around to building the board and modifying the software to suit. I had a cheapo tiny oled graphic display (128 x 64) that has been sitting around for year or so - seemed really difficult to "drive" it without using someone else's software libraries, something i hate doing as they are usualy crap and full of bloatware to make them "transportable". Anyway having spent at least a day staring the data sheet (writting in Chinglish) I finally got it sussed and made the display display some stuff. Just uses about 5 mA and quite readable in fairly strong light so I like it!

 

Anyway, video of the board in action. Apart from the temperature (which is coming from the probe connected at the top of the board, the second page on the display is the parameters received over CANBUS from the Mastershunt but of course no boat for the time being. I do know that bit works as it worked on the mk1 board. Matchstick for size reference. The tiny square chip is the one I unsoldered from the old board (they are £8!) and it was a right struggle to re-solder it to the new board - bad enough with a new chip without pre-existing bits of solder on it! Hence it looks a bit messy. But at least I know the chip is fairly robust in terms of its ability to withstand repeated heating to 230C!

 

The trouble is that with all this progress, at some point I'm going to have to get some proper Lithium batteries - perhaps our Trojans will die soon!

 

 

 

 

Edited May 2, 2020 by nicknorman

[peterboat]

26 minutes ago, nicknorman said:

Not sure how interested folk are in my tinkering so reading this is optional! I got my mk2 BMS boards back from china several weeks ago but have been preoccupied with the alternator regulator. Finally got around to building the board and modifying the software to suit. I had a cheapo tiny oled graphic display (128 x 64) that has been sitting around for year or so - seemed really difficult to "drive" it without using someone else's software libraries, something i hate doing as they are usualy crap and full of bloatware to make them "transportable". Anyway having spent at least a day staring the data sheet (writting in Chinglish) I finally got it sussed and made the display display some stuff. Just uses about 5 mA and quite readable in fairly strong light so I like it!

 

Anyway, video of the board in action. Apart from the temperature (which is coming from the probe connected at the top of the board, the second page on the display is the parameters received over CANBUS from the Mastershunt but of course no boat for the time being. I do know that bit works as it worked on the mk1 board. Matchstick for size reference. The tiny square chip is the one I unsoldered from the old board (they are £8!) and it was a right struggle to re-solder it to the new board - bad enough with a new chip without pre-existing bits of solder on it! Hence it looks a bit messy. But at least I know the chip is fairly robust in terms of its ability to withstand repeated heating to 230C!

 

The trouble is that with all this progress, at some point I'm going to have to get some proper Lithium batteries - perhaps our Trojans will die soon!

 

 

 

 

For people with engines it's good stuff, and that's the majority on here 

[Dr Bob]

37 minutes ago, nicknorman said:

Not sure how interested folk are in my tinkering so reading this is optional! I got my mk2 BMS boards back from china several weeks ago but have been preoccupied with the alternator regulator. Finally got around to building the board and modifying the software to suit. I had a cheapo tiny oled graphic display (128 x 64) that has been sitting around for year or so - seemed really difficult to "drive" it without using someone else's software libraries, something i hate doing as they are usualy crap and full of bloatware to make them "transportable". Anyway having spent at least a day staring the data sheet (writting in Chinglish) I finally got it sussed and made the display display some stuff. Just uses about 5 mA and quite readable in fairly strong light so I like it!

 

Anyway, video of the board in action. Apart from the temperature (which is coming from the probe connected at the top of the board, the second page on the display is the parameters received over CANBUS from the Mastershunt but of course no boat for the time being. I do know that bit works as it worked on the mk1 board. Matchstick for size reference. The tiny square chip is the one I unsoldered from the old board (they are £8!) and it was a right struggle to re-solder it to the new board - bad enough with a new chip without pre-existing bits of solder on it! Hence it looks a bit messy. But at least I know the chip is fairly robust in terms of its ability to withstand repeated heating to 230C!

 

The trouble is that with all this progress, at some point I'm going to have to get some proper Lithium batteries - perhaps our Trojans will die soon!

 

 

 

 

 

 I will review in a weeks time. Too busy on the virtual BCN challenge.

10 minutes ago, peterboat said:

For people with engines it's good stuff, and that's the majority on here 

Oi, you're meant to be getting the bote ready for tomorrow!

Don't get distracted!

[WotEver]

5 hours ago, nicknorman said:

The tiny square chip is the one I unsoldered from the old board (they are £8!)...

Spoken like a true Scot

5 hours ago, nicknorman said:

Just uses about 5 mA and quite readable in fairly strong light so I like it!

It looks great. I likee too. 

What’s the push button for? I can’t remember if you told us. 

[MoominPapa]

8 hours ago, nicknorman said:

I had a cheapo tiny oled graphic display (128 x 64) that has been sitting around for year or so - seemed really difficult to "drive" it without using someone else's software libraries, something i hate doing as they are usualy crap and full of bloatware to make them "transportable".

One tip on the OLED displays: If you leave them on and displaying the same information 24/7 they do burn in. I ended up implementing a screen saver which shows only the most important information (% Soc) and moves it slowly around the whole display area.

 

MP.

 

[nicknorman]

4 hours ago, WotEver said:

Spoken like a true Scot

It looks great. I likee too. 

What’s the push button for? I can’t remember if you told us. 

It doesn’t do anything yet, I just added it as “available infrastructure” a bit like the LEDs as I had spare IO.  But I think it will probably be short press to bring the display on for a few minutes, long press to reset the tripped emergency disconnect relay - that is, if I decide to just have the one relay. If I decide to have 2 relays (one for charge, one for load) then the reconnect buttons will have to be elsewhere.

[nicknorman]

2 hours ago, MoominPapa said:

One tip on the OLED displays: If you leave them on and displaying the same information 24/7 they do burn in. I ended up implementing a screen saver which shows only the most important information (% Soc) and moves it slowly around the whole display area.

 

MP.

 

Thanks for the tip. I don’t plan to have the display on all the time as this device is intended to be “transparent, in the background” using minimum static current, and I already have a means to display SoC (the Masterview showing Mastershunt data), and I want to keep current drain to a minimum.

 

I do have a slight quandary though, if I use the MS SoC as the primary means to measure and display SoC, and dont routinely take it to fully charged, as we know it will drift off. If I implement the Moomin algorithm to merge integrated current and voltage derived SoC, there seems no means to back-feed that to the Mastershunt. One can do a lot of stuff over CANBUS but not alter the MS SoC, other than by resetting the whole thing and starting from scratch. Shame!

[jetzi]

So, due to the lockdown, I still don't have any of my kit. By the time I get it all set up I fear we might be past summer and then I'll need to charge via alternator. So I have been using the time to think about the alternator charging problem.

 

I know this has been discussed at length already, but I think it's a really crucial topic to get right so I'm just going to dump my thoughts here and if I'm horribly wrong hopefully someone will stop me.

 

For backup I'm still certainly planning on having the BMS or BMV (or both) automatically isolate the (alternator + LA dump) from the (lithiums + MPPT + domestic load) when the state of charge exceeds say 85%.

 

However I don't believe this would be enough by itself, because I think while my big juicy lifepo4 bank is being charged, my piddly little 70A alternator, which heats up quite a bit when charging LAs, is likely to get exceedingly hot (even if I do hook up an extra fan).

 

At a bare minimum I want to have overtemp shutoff for the alternator, and if I'm going to go that far I may as well add an overvoltage shutoff. The easiest way I can think of to do this is to use an Arduino (versions of which can be powered by up to 20V - though 7-12V is recommended on those models), with a 25V max voltage sensor like this and a temperature sensor like this. The voltage sensor would be across the alternator out and the engine block negative - this voltage should be the voltage of the whole battery/alternator system. The arduino would drive a relay like this which in turn would turn off the field current in the alternator (though I have no idea yet where to begin finding the wires that control it).

 

Then it's just a matter of programming the arduino to flip off the relay & field current at say 85 degrees / 14.5V and flip it on at say 75 degrees / 14.3V and hopefully the alternator can then look after itself.

 

I guess first prize would be to regulate the alternator voltage down to a 13.8V float, when the voltage reaches 14.5V. This would then allow you to use the power from your alternator while your engine is running, even if your batteries are full. Apart from the fact that I don't know how voltage regulators work, I don't see how they could work. Because surely without disconnecting the batteries and alternator, the voltage across the alternator and across the battery will be the same, since they are the same circuit? With 80% charged LiFePOs the voltage is likely to still be in the 14.4V range - the regulator won't be able to regulate the alternator lower than the battery voltage, surely.

[nicknorman]

2 hours ago, ivan&alice said:

So, due to the lockdown, I still don't have any of my kit. By the time I get it all set up I fear we might be past summer and then I'll need to charge via alternator. So I have been using the time to think about the alternator charging problem.

 

I know this has been discussed at length already, but I think it's a really crucial topic to get right so I'm just going to dump my thoughts here and if I'm horribly wrong hopefully someone will stop me.

 

For backup I'm still certainly planning on having the BMS or BMV (or both) automatically isolate the (alternator + LA dump) from the (lithiums + MPPT + domestic load) when the state of charge exceeds say 85%.

 

However I don't believe this would be enough by itself, because I think while my big juicy lifepo4 bank is being charged, my piddly little 70A alternator, which heats up quite a bit when charging LAs, is likely to get exceedingly hot (even if I do hook up an extra fan).

 

At a bare minimum I want to have overtemp shutoff for the alternator, and if I'm going to go that far I may as well add an overvoltage shutoff. The easiest way I can think of to do this is to use an Arduino (versions of which can be powered by up to 20V - though 7-12V is recommended on those models), with a 25V max voltage sensor like this and a temperature sensor like this. The voltage sensor would be across the alternator out and the engine block negative - this voltage should be the voltage of the whole battery/alternator system. The arduino would drive a relay like this which in turn would turn off the field current in the alternator (though I have no idea yet where to begin finding the wires that control it).

 

Then it's just a matter of programming the arduino to flip off the relay & field current at say 85 degrees / 14.5V and flip it on at say 75 degrees / 14.3V and hopefully the alternator can then look after itself.

 

I guess first prize would be to regulate the alternator voltage down to a 13.8V float, when the voltage reaches 14.5V. This would then allow you to use the power from your alternator while your engine is running, even if your batteries are full. Apart from the fact that I don't know how voltage regulators work, I don't see how they could work. Because surely without disconnecting the batteries and alternator, the voltage across the alternator and across the battery will be the same, since they are the same circuit? With 80% charged LiFePOs the voltage is likely to still be in the 14.4V range - the regulator won't be able to regulate the alternator lower than the battery voltage, surely.

Yes you could simply open a relay when the temperature exceeds whatever. However the relay you specify is only rated at 2A, I think the maximum field current is likely to be more than that. And more importantly, there is a lot of inductance in a field / rotor winding. The property of inductance is to preserve current so if you try to suddenly stop the current, it will fight back by generating a large voltage across the relay contacts which will rapidly burn out the relay. At the least, you need a freewheel diode to allow the field current to subside naturally.

 

As to your point about switching to 13.5v from 14.5v and how that could work, bear in mind that whilst the battery voltage might be 14.5 under charge, as soon as you stop charging, the battery voltage will fall to something around 13.6 or less. Its just the way batteries are! OK it will take a few seconds for that to happen and in the mean time an alternator trying to regulate to 13.5v will stop producing output. But after a few seconds things will stabilise and the alternator will produce whatever current is needed (according to the boat's loads) to maintain 13.5 without putting any more into the batteries. In other words a regulator set to a lower voltage than that present on the batteries simply stops outputting any current and bides its time until the system voltage falls to the regulated voltage. It doesn't try to force the voltage down.

 

Last point is that if you use a BMV type AH counter and never take the batteries up to 100%, it will gradually drift off so that when it says 80%, the batteries might actually be at 60, 70, 80, 90, 100% or whatever. AH counting meters that aren't resynchronised by taking to 100% have an inevitable and cumulative error.

[jetzi]

3 minutes ago, nicknorman said:

As to your point about switching to 13.5v from 14.5v and how that could work, bear in mind that whilst the battery voltage might be 14.5 under charge, as soon as you stop charging, the battery voltage will fall to something around 13.6 or less. Its just the way batteries are!

Ah thanks, this is the bit that I was missing. So when a LiFePO battery is at 80% charge, the 14.4 odd volts (I realise this will vary a bit from battery to battery) figure refers to the voltage under charge, not the voltage at rest?

 

Couls a secondary regulator be installed after and external to the alternator, which could regulate the alternator's 14V down to 13.something. Then when the battery is full, it simply turns on the extra step down in voltage. When the battery is charging, it bypasses it?

 

 

[nicknorman]

14 minutes ago, ivan&alice said:

Ah thanks, this is the bit that I was missing. So when a LiFePO battery is at 80% charge, the 14.4 odd volts (I realise this will vary a bit from battery to battery) figure refers to the voltage under charge, not the voltage at rest?

 

Couls a secondary regulator be installed after and external to the alternator, which could regulate the alternator's 14V down to 13.something. Then when the battery is full, it simply turns on the extra step down in voltage. When the battery is charging, it bypasses it?

 

 

Yes, the resting  voltage at 80% SoC will be around 13.3v. Regarding your second para, yes this is what sterling’s BtoB does, but at a cost. It’s what Dr Bob uses.

[jetzi]

Ah I see - thanks. The cost is the loss in power from the inefficient extra step down I suppose. I believe it is a moot point for me anyway since my 70A alternator won't drive one of those.

[Dre]

32 minutes ago, ivan&alice said:

Ah I see - thanks. The cost is the loss in power from the inefficient extra step down I suppose. I believe it is a moot point for me anyway since my 70A alternator won't drive one of those.

Why won't it? 

[BEngo]

I have been investigating something similar for an A127.  A typical alternator field current seems to be  up to 5A, so the relay has to switch that.

 

The A127 regulator is easy to dismantle.  Remove 3 screws holding it to the case and out it comes. The yellow wire to the small spade terminal is the incoming field power from the field diodes. Separate the metal part of the regulator from the plastic part and you will find 3 tiny wires connecting the two parts.  One is connected to the yellow wire.  The other two are connected to the brushes, one of which is also connected to the metal part and so, via the securing screws, to the alternator casing.

The easiest control route appears to be to switch the power to the regulator and leave it in circuit.  As recommended by Moomin Papa, swapping the standard reg for a tractor regulator allows you to control of the regulated voltage through varying a resistance in the extra lead.. No doubt an Arduino might enable you to use a relay switch between a higher charge voltage and a lower float voltage.

 

  I was looking at current limiting the alternator, to keep it cool rather than to keep heating it up and cooling it off.  That requires high side switching  in the field circuit, because of the one brush to case connection and is unsuitable for a relay because it will switch too often. I have not yet figured out how to do solid state switching efficiently. I understand a Darlington will get a bit hot, wasting amps and the right sort of mosfet is doing my  head in. What is a charge pump?

I also don't want to end up with a  complicated circuit board to make as my idea of a soldering iron is my 125W Solon, or a blowlamp for bigger jobs.  So I am still thinking.

 

Looking at individual LiFePO4 cells with an arduino also seems to be complicated, but is  soluble to sensible accuracy with a plethora of rail to rail op amps.  Measuring 1,2,3 and 4 cell voltages and doing arithmetic to get individual cells is OK in theory, but the achievable accuracy is not good using the arduino AtoD converter.

 

N

Edited May 10, 2020 by BEngo

[nicknorman]

3 hours ago, BEngo said:

I have been investigating something similar for an A127.  A typical alternator field current seems to be  up to 5A, so the relay has to switch that. You can work it out by measuring the resistance of the field coil (rotor), and then dividing that into the maximum expected voltage, say 14.4v or whatever. Even though it is a whirly round coil thing, the current is limited by the resistance not the inductance. My Iskra 175A alternator takes up to about 4.1A at 14.4v

 

The A127 regulator is easy to dismantle.  Remove 3 screws holding it to the case and out it comes. The yellow wire to the small spade terminal is the incoming field power from the field diodes. Separate the metal part of the regulator from the plastic part and you will find 3 tiny wires connecting the two parts.  One is connected to the yellow wire.  The other two are connected to the brushes, one of which is also connected to the metal part and so, via the securing screws, to the alternator casing.

The easiest control route appears to be to switch the power to the regulator and leave it in circuit. However you shouldn't just interupt the field current - it will fight back by generating 100s or 1000s of volts. That is how ignition coils work! You need a freewheel diode so that the current can continue for a short while and subside at its leisure. As recommended by Moomin Papa, swapping the standard reg for a tractor regulator allows you to control of the regulated voltage through varying a resistance in the extra lead.. No doubt an Arduino might enable you to use a relay switch between a higher charge voltage and a lower float voltage.

 

  I was looking at current limiting the alternator, to keep it cool rather than to keep heating it up and cooling it off.  That requires high side switching  in the field circuit, because of the one brush to case connection and is unsuitable for a relay because it will switch too often. I have not yet figured out how to do solid state switching efficiently. I understand a Darlington will get a bit hot, wasting amps and the right sort of mosfet is doing my  head in. Yes a darlington drops voltage by definition, like a diode does, and hence dissipates lots of power. A MOSFET is better modelled by a small resistance (in the milliohms range). What is a charge pump? The trouble with high side switching using a MOSFET is that it needs a gate votage several volts higher than the thing you are switching in order to turn it on fully. So if you are switching say 14.4v you would need perhaps 17.5v or so gate voltage to turn it on fully, and that is for a "logic level" MOSFET. Some types require even more voltage on the gate. Hence you get high side MOSFET drivers incorporating a charge pump. A charge pump is a system of capacitors and electronic switches that creates a higher voltage from a lower one, typilcally at pretty low power (but quite adequate for switching a mosfet, whose gate is effectively "open circuit" once it is switched). Just think of it as translating your logic 0 or 1 from the Arduino into a voltage suitable for driving a high side mosfet.

The chip I'm using (AR6000) also does high side switching with a (built in) MOSFET and thus also has built in charge pump.

 

I also don't want to end up with a  complicated circuit board to make as my idea of a soldering iron is my 125W Solon, or a blowlamp for bigger jobs.  Good luck with that!  So I am still thinking.

 

Looking at individual LiFePO4 cells with an arduino also seems to be complicated, but is  soluble to sensible accuracy with a plethora of rail to rail op amps.  Measuring 1,2,3 and 4 cell voltages and doing arithmetic to get individual cells is OK in theory, but the achievable accuracy is not good using the arduino AtoD converter.

 

N

All these issues are why I settled on the design I did - fairly high tech. If there were an easy solution, everyone would be doing it!

Comments in red above:

 

Bit more detail on a charge pump: imagine you connecting a capacitor across 0v and 5v of your arduino board. Now disconnect both ends of the capacitor and connect the end that was at 0v, to the battery+ terminal say at 14.4v. What is the voltage on the other end of the capacitor relative to 0v? Answer 14.4+5 = 19.4v you have just "pumped" the charge up from 5v to 19.4v. Now replace your fingers with some electronic switchery that can connect and disconnnect the terminals of the capacitor, alternating rapidly between the 0v, 5v and the 14.4v and you have a charge pump. Maybe add a storage capacitor to the 14.4v to store the charge whilst the "mobile" capacitor is connected to the 0v, 5v, switch fast, and how you have a nice steady 19.4v that can be applied to the gate of the high-side MOSFET to switch it on.

Edited May 10, 2020 by nicknorman

[BEngo]

Nick, Thank you for the explanation of a  charge pump. I have a circuit for one somewhere, as part of the details of the controller that Tom and Bex use.  I may now be able to make sense of that.  Overall that controller did/does everything most folks wanted or needed,  including  talk to CANBUS,  but it went commercial at high cost and even if I found or created a board drawing there is no prospect of me trying out SMD assembly.

I hoped the regulator info might be helpful to Ivan and Alice though.

N

[nicknorman]

11 minutes ago, BEngo said:

Nick, Thank you for the explanation of a  charge pump. I have a circuit for one somewhere, as part of the details of the controller that Tom and Bex use.  I may now be able to make sense of that.  Overall that controller did/does everything most folks wanted or needed,  including  talk to CANBUS,  but it went commercial at high cost and even if I found or created a board drawing there is no prospect of me trying out SMD assembly.

I hoped the regulator info might be helpful to Ivan and Alice though.

N

SMD assembly is easier than you might think, you just need solder paste and a temperature controlled hot air rework gun (£35 from eBay). And a steady hand to place the components with tweezers and some magnifying goggle things! The only thing I’ve struggled with is the tiny 48 pin square chip with leads at 0.5mm pitch (LQFP package).

[redwing]

8 hours ago, ivan&alice said:

Ah I see - thanks. The cost is the loss in power from the inefficient extra step down I suppose. I believe it is a moot point for me anyway since my 70A alternator won't drive one of those.

7 hours ago, Dre said:

Why won't it? 

I think Dr Bob has an 120a A to B and not a B to B 

 

Dre how are you getting on with yours ?

Haven't started my install yet.

 

Ivan, Sterling do a 30amp B to B. Battleborn do something called a Battery Isolation Manager https://battlebornbatteries.com/shop/lifepo4-battery-isolation-manager/ . No Idea if it would be useful.

They also have some info on B to B https://battlebornbatteries.com/sterling-pro-batt-ultra-battery-battery-charger/

 

 

Edited May 10, 2020 by redwing
eta Battleborn info

[Dre]

2 hours ago, redwing said:

Dre how are you getting on with yours ?

Haven't started my install yet.

Hey, I received the cells yesterday... YAY! 

 

UPS, all individually wrapped and boxed and all perfectly matched in voltage. And they are tiny!! That whole thing is 400mm by 180 by 180 at about 24kg (replacing 5x 110ah acid lumps of  350x190x180 @ 23kg.... EACH) 

 

 

That's 300ah on a dinette TABLE! ?

 

All I've DONE so far is checked the individual voltages which all match to two decimal points. Connected up into one bank of 12v with the supplied copper busbars (not the thickest copper but they gave me 16 of them so I doubled up on the series connections) Terminated and connected the balance and BMS leads and tested the Bluetooth app. App is great and has more parameters that I care for which all seem to work OK. Bluetooth worked straight away. BMS is 120A so I'm planning to add a second one as I would like at least a safely usable 150a for when I need it (my inverter is 2kva)

BTW the BMS came with those cables already  soldered on the board all I had to do is crimp some lugs on. Cables are 6mm each so you get a nice 18sqmm on each side. 

 

Can't wait to cut into my system and install this pretty little thing! 

 

Will keep you posted 

 

???

[peterboat]

8 minutes ago, Dre said:

Hey, I received the cells yesterday... YAY! 

 

UPS, all individually wrapped and boxed and all perfectly matched in voltage. And they are tiny!! That whole thing is 400mm by 180 by 180 at about 24kg (replacing 5x 110ah acid lumps of  350x190x180 @ 23kg.... EACH) 

 

 

That's 300ah on a dinette TABLE! ?

 

All I've DONE so far is checked the individual voltages which all match to two decimal points. Connected up into one bank of 12v with the supplied copper busbars (not the thickest copper but they gave me 16 of them so I doubled up on the series connections) Terminated and connected the balance and BMS leads and tested the Bluetooth app. App is great and has more parameters that I care for which all seem to work OK. Bluetooth worked straight away. BMS is 120A so I'm planning to add a second one as I would like at least a safely usable 150a for when I need it (my inverter is 2kva)

BTW the BMS came with those cables already  soldered on the board all I had to do is crimp some lugs on. Cables are 6mm each so you get a nice 18sqmm on each side. 

 

Can't wait to cut into my system and install this pretty little thing! 

 

Will keep you posted 

 

???

I was the same when I got mine over 2 years ago, now they just work and live under the steps into the boat! They work and work well I am know something better is just around the corner but for us these batteries are just so good 

[nicknorman]

15 minutes ago, Dre said:

Hey, I received the cells yesterday... YAY! 

 

UPS, all individually wrapped and boxed and all perfectly matched in voltage. And they are tiny!! That whole thing is 400mm by 180 by 180 at about 24kg (replacing 5x 110ah acid lumps of  350x190x180 @ 23kg.... EACH) 

 

 

That's 300ah on a dinette TABLE! ?

 

All I've DONE so far is checked the individual voltages which all match to two decimal points. Connected up into one bank of 12v with the supplied copper busbars (not the thickest copper but they gave me 16 of them so I doubled up on the series connections) Terminated and connected the balance and BMS leads and tested the Bluetooth app. App is great and has more parameters that I care for which all seem to work OK. Bluetooth worked straight away. BMS is 120A so I'm planning to add a second one as I would like at least a safely usable 150a for when I need it (my inverter is 2kva)

BTW the BMS came with those cables already  soldered on the board all I had to do is crimp some lugs on. Cables are 6mm each so you get a nice 18sqmm on each side. 

 

Can't wait to cut into my system and install this pretty little thing! 

 

Will keep you posted 

 

???

Looks great! Could you remind me where they are from, price etc (if you don’t mind). Was the BMS a separate thing?

[Dre]

1 minute ago, peterboat said:

I was the same when I got mine over 2 years ago, now they just work and live under the steps into the boat! They work and work well I am know something better is just around the corner but for us these batteries are just so good 

Great to hear that. That's exactly what my plan is... Bit of fun researching and setting up and then forgetting about it! But I would also like to show that lithiums are easy and cheap! 

[peterboat]

1 minute ago, Dre said:

Great to hear that. That's exactly what my plan is... Bit of fun researching and setting up and then forgetting about it! But I would also like to show that lithiums are easy and cheap! 

Exactly and in the long run they will more than likely be the last batteries you ever buy! Making them very cheap 

[Dre]

9 minutes ago, nicknorman said:

Looks great! Could you remind me where they are from, price etc (if you don’t mind). Was the BMS a separate thing?

 

12 minutes ago, nicknorman said:

Looks great! Could you remind me where they are from, price etc (if you don’t mind). Was the BMS a separate thing?

Sorry I thjnk that link didn't work. 

It's post #773 on page 31 

I put the links for most bits 

[nicknorman]

20 minutes ago, Dre said:

 

Sorry I thjnk that link didn't work. 

It's post #773 on page 31 

I put the links for most bits 

Thanks, got it! Did you get stung for any unexpected import duties etc?