Another Lithium battery thread

[nicknorman]

57 minutes ago, dmr said:

Reply to various post above....

We have the 100amp Iskra alternator which is a smaller frame than the 175. We've run this for about 5 years now with only one replacement (slip rings worn out) so it is able to run flat out for longish periods, but I am amazed it does this, it runs much too hot and smells quite bad some days.

 

I've put a fair bit of thought into alternator controllers over the last few years but not got motivated enough to make anything myself, my feeling is that all this relay-disconnect stuff is Not the way to go, and a well thought out Arduino (or equivalent) bespoke alternator controller Is the way to go (with the inbult regulator removed). I really like my Adverc but its all done in hardware, with a bit of processor power and knowledge it should be possible to make a really good controller.

 

..............Dave 

My head is full of PIC microcontroller and C at the moment - project to do with gliding, but the power of a decent midrange PIC (in my case, the 16F18326) is astounding for under £2 and with a free IDE/C compiler. More peripherals than you can shake a stick at, 32MHz internal clock giving 8MHz instruction speed, 28K programme flash ROM, 2K RAM and 256 bytes data EEPROM and all for about 3mA supply current and zero external components. Also using the free RS Designspark PCB design software

 

Although of course interfacing all that with the real world can be the tricky bit!

 

But ultimately a variable mark space ratio (PWM) control of field current in response to alternator output voltage and current is all that we are talking about. How hard can it be?

[Dr Bob]

3 minutes ago, nicknorman said:

But ultimately a variable mark space ratio (PWM) control of field current in response to alternator output voltage and current is all that we are talking about. How hard can it be?

I can do a wicked Haggis sandwich but this looks a tad more complex.

Are there any commercially available controllers that can do the job, Adverc, Sterling, Balmar etc? The WS500 is not yet commercially available....(coming soon).

[Tom and Bex]

It's good that more people are looking at lithiums now, they've certainly simplified our charging regime over winter, and dramatically reduced engine running time to an average of about an hour a day. I think the benefits to heavy power users or those living of grid should be clear now. 

 

To pick up on a few points raised above, the handling of alternator charging is definitely one of the more tricky areas to handle. I'm really glad we went for the controller we did, and we did manage to get a 3rd generation one ready made up and just mounted it in a cheap box. A shame if it's now going to be commercialised, but I guess that was inevitable at some point - no doubt at very significant cost increase!

 

I'm not sure of any currently available commercial alternator controllers that have the same features, particularly the monitoring of current. I guess that will change in the future as best practices with lithium batteries filter down, the trouble is we are such a tiny fraction of the market, it's not worth it for most companies. Balmar have a controller that is claimed suitable for lithiums, and I believe Mastervolt do as well? Not really looked into them much though after I chose the arduino route. 

 

As to disconnect devices, I went down the separate charge and load bus route, so needed 2 heavy duty disconnects. I considered using relays or contactors, but decided even with energy saving circuits, I did not want to put up with the continuous drain having the coils energised. I opted for the BEP 701-md motorised battery switch for the load side, which was quite easy to install and wire to BMS, and probably one of the simpler options. For the charge disconnect, I used the TE BDS-A 190A latching relay. This relay is used on some Ford's as a battery disconnect (possibly transits?) so can be obtained 2nd hand. The big problem using latching relays is the control of them, they require a brief pulse to switch on or off, but most control systems, BMS etc just have a steady output,  either on or off so you need to use an interface circuit with them. 

 

An alternative way to terminate charge, could be to use alarm outputs on a battery monitor such as Victron BMV 701. This could be set at whatever end point you choose, based on current, voltage, or SOC. Personally, having had these batteries now for 4 months, I would set it to re-synchronise to 100% at 14.0v, tail current 6%, and take this as 100% charged and turn off charge sources at this point. 

 

Another alternative charge control method could be use of an adjustable voltage sensing relay or board, and set this to cut charging when voltage reaches say 14.0v. This is what we do with our alternator controller to get additional bulk charge from engine alternator - standard split charge relay that opens when 14.0v is reached. We find this consistently occurs around 80ish%, and is usually when we stop charging. Every 4-6 weeks (or when out cruising) we do a full charge to synchronise BMV to 100%, but notice very little drift. Trouble with this is the exact point could vary depending on current (e.g. due to engine speed) and you sacrifice some useable capacity. Having said that, ours usually operate in the 30-80% range.

 

Hope this answers some of your questions @Dr Bob and good luck with your installation. 

Edited January 6, 2019 by Tom and Bex

[dmr]

33 minutes ago, nicknorman said:

My head is full of PIC microcontroller and C at the moment - project to do with gliding, but the power of a decent midrange PIC (in my case, the 16F18326) is astounding for under £2 and with a free IDE/C compiler. More peripherals than you can shake a stick at, 32MHz internal clock giving 8MHz instruction speed, 28K programme flash ROM, 2K RAM and 256 bytes data EEPROM and all for about 3mA supply current and zero external components. Also using the free RS Designspark PCB design software

 

Although of course interfacing all that with the real world can be the tricky bit!

 

But ultimately a variable mark space ratio (PWM) control of field current in response to alternator output voltage and current is all that we are talking about. How hard can it be?

I think its not as trivial as that, after all its a feedback system so you have all that control theory stuff to make sure its stable, and its a sort of sampled data system too rather than straight analog which might complicate it a bit. The other factor is that the alternator output voltage is fluctuating and the desire is to control the mean voltage but putting a big smoother (dominant pole?) in the feedback loop will make the system extra prone to big voltage spikes when loads are switched off.

Then again Adverc do it all with a couple of transistors!

Trouble with developing power electronics is that the mistakes are more dramatic and expensive. ?

 

I had a little play with the designspark stuff a couple of years ago but have decided that as a full time CCing liveaboard that I'm going to stick to software, it takes up less space than electronics.

 

.............Dave

[nicknorman]

28 minutes ago, dmr said:

I think its not as trivial as that, after all its a feedback system so you have all that control theory stuff to make sure its stable, and its a sort of sampled data system too rather than straight analog which might complicate it a bit. The other factor is that the alternator output voltage is fluctuating and the desire is to control the mean voltage but putting a big smoother (dominant pole?) in the feedback loop will make the system extra prone to big voltage spikes when loads are switched off.

Then again Adverc do it all with a couple of transistors!

Trouble with developing power electronics is that the mistakes are more dramatic and expensive. ?

 

I had a little play with the designspark stuff a couple of years ago but have decided that as a full time CCing liveaboard that I'm going to stick to software, it takes up less space than electronics.

 

.............Dave

Well I did do control theory at uni, though I’m sure I’ve forgotten most of it! And sampled data digital filtering etc. These days people seem to use PID (proportional, integral, differential) control systems which is fairly easy to implement in software, harder in hardware. PID seems to get over the compromise between needing high gain to get good transient response and get over the “droop”, and low gain to ensure stability. There are models on the Internet you can fiddle with.

 

The great thing about digital is that it doesn’t have to be a linear system (ie doesn't have to mimic what you could do with analogue electronics)

 

It’s a shame that the source code is no longer on the Arduino VSR chappy’s website (if it ever was), it would be interesting to see how he did it.

Edited January 7, 2019 by nicknorman

[dmr]

5 minutes ago, nicknorman said:

Well I did do control theory at uni, though I’m sure I’ve forgotten most of it! And sampled data digital filtering etc. These days people seem to use PID (proportional, integral, differential) control systems which is fairly easy to implement in software, harder in hardware. PID seems to get over the compromise between needing high gain to get good transient response and get over the “droop”, and low gain to ensure stability. There are models on the Internet you can fiddle with.

 

It’s a shame that the source code is no longer on the Arduino VSR chappy’s website (if it ever was), it would be interesting to see how he did it.

I don't think its a recent "these days" thing. I believe control theory was developed with mechanical systems trying to aim the big guns on a warship despite the ship rolling in the sea, probably WW1 stuff though I'm not sure of that. The "D" term comes from trying to handle the inertia of the rotating gun turret.

 

This might all be b*ll*cks but its a good story!

 

...............Dave

[nicknorman]

Just now, dmr said:

I don't think its a recent "these days" thing. I believe control theory was developed with mechanical systems trying to aim the big guns on a warship despite the ship rolling in the sea, probably WW1 stuff though I'm not sure of that. The "D" term comes from trying to handle the inertia of the rotating gun turret.

 

This might all be b*ll*cks but its a good story!

 

...............Dave

You are probably right. I said that because PID wasn’t something we covered at Uni (1977) so I though it might be a fairly new concept. We only did PD. These days PID is everywhere.

[Tom and Bex]

13 minutes ago, nicknorman said:

It’s a shame that the source code is no longer on the Arduino VSR chappy’s website (if it ever was), it would be interesting to see how he did it.

I have a copy that he emailed me if you want it?

[nicknorman]

Anyway, if you are sampling fast enough you would look at the peaks to react to short term changes, and the average to get the rectified voltage to settle at the right value. Simples (!).

1 minute ago, Tom and Bex said:

I have a copy that he emailed me if you want it?

Yes please! PM sending momentarily...

Edited January 7, 2019 by nicknorman

[peterboat]

13 hours ago, Dr Bob said:

Peter, have you got a link to JohnV's system? He's the only one of the bunch that I've not read their stories. Interested in how he solves his alternator charging problem.

John has 4 LifePo4s and 4 LAs they are similar in capacity [138ah] He has a 24 volt system so they are configured for that, his alternator never puts out more than 27.6v so he has no control system on it other than  the cheap amazon board and a disconnect relay, he can turn off the alternator remotely. He also has 1KW of solar which is set at 27.6v Last year we did a lot of cruising and suffered no issues, if the regulator in the alternator was to fail the board would register over voltage and disconnect the relay sorting the issue out. Like me John is a livaboard so we work the system constantly

[dmr]

10 hours ago, nicknorman said:

Anyway, if you are sampling fast enough you would look at the peaks to react to short term changes, and the average to get the rectified voltage to settle at the right value. Simples (!).

Yes please! PM sending momentarily...

Im only half reading this thread (tut tut) are we talking about an arduino based alternator controller here, or more of a battery switch off thing? If its an alternator controller is there a circuit diagram available as well as the code?????

 

...............Dave

[Dr Bob]

1 hour ago, peterboat said:

John has 4 LifePo4s and 4 LAs they are similar in capacity [138ah] He has a 24 volt system so they are configured for that, his alternator never puts out more than 27.6v so he has no control system on it other than  the cheap amazon board and a disconnect relay, he can turn off the alternator remotely. He also has 1KW of solar which is set at 27.6v Last year we did a lot of cruising and suffered no issues, if the regulator in the alternator was to fail the board would register over voltage and disconnect the relay sorting the issue out. Like me John is a livaboard so we work the system constantly

Thanks Peter. Interested in you comment on turning off the alternator. Do you know how John is doing this? For me I would be happy to manually switch of the alternator but not sure how to do this. I have it in my mind that once the alternator is going, it doesnt need a 12v supply so you cant turn it off, but I do know the alternator doesnt work if the plug on the wiring harness comes apart (before it is started up)! Is there a clever way to turn it off?

[Dr Bob]

11 hours ago, Tom and Bex said:

It's good that more people are looking at lithiums now, they've certainly simplified our charging regime over winter, and dramatically reduced engine running time to an average of about an hour a day. I think the benefits to heavy power users or those living of grid should be clear now. 

 

To pick up on a few points raised above, the handling of alternator charging is definitely one of the more tricky areas to handle. I'm really glad we went for the controller we did, and we did manage to get a 3rd generation one ready made up and just mounted it in a cheap box. A shame if it's now going to be commercialised, but I guess that was inevitable at some point - no doubt at very significant cost increase!

 

I'm not sure of any currently available commercial alternator controllers that have the same features, particularly the monitoring of current. I guess that will change in the future as best practices with lithium batteries filter down, the trouble is we are such a tiny fraction of the market, it's not worth it for most companies. Balmar have a controller that is claimed suitable for lithiums, and I believe Mastervolt do as well? Not really looked into them much though after I chose the arduino route. 

 

As to disconnect devices, I went down the separate charge and load bus route, so needed 2 heavy duty disconnects. I considered using relays or contactors, but decided even with energy saving circuits, I did not want to put up with the continuous drain having the coils energised. I opted for the BEP 701-md motorised battery switch for the load side, which was quite easy to install and wire to BMS, and probably one of the simpler options. For the charge disconnect, I used the TE BDS-A 190A latching relay. This relay is used on some Ford's as a battery disconnect (possibly transits?) so can be obtained 2nd hand. The big problem using latching relays is the control of them, they require a brief pulse to switch on or off, but most control systems, BMS etc just have a steady output,  either on or off so you need to use an interface circuit with them. 

 

An alternative way to terminate charge, could be to use alarm outputs on a battery monitor such as Victron BMV 701. This could be set at whatever end point you choose, based on current, voltage, or SOC. Personally, having had these batteries now for 4 months, I would set it to re-synchronise to 100% at 14.0v, tail current 6%, and take this as 100% charged and turn off charge sources at this point. 

 

Another alternative charge control method could be use of an adjustable voltage sensing relay or board, and set this to cut charging when voltage reaches say 14.0v. This is what we do with our alternator controller to get additional bulk charge from engine alternator - standard split charge relay that opens when 14.0v is reached. We find this consistently occurs around 80ish%, and is usually when we stop charging. Every 4-6 weeks (or when out cruising) we do a full charge to synchronise BMV to 100%, but notice very little drift. Trouble with this is the exact point could vary depending on current (e.g. due to engine speed) and you sacrifice some useable capacity. Having said that, ours usually operate in the 30-80% range.

 

Hope this answers some of your questions @Dr Bob and good luck with your installation. 

Thanks for the detailed response.

I will have a look at Balmar and Mastervolt and do a bit more digging on when the WS500 is likely to be commercially available (the site says 'comings soon').

Thanks for the detail on the disconnects.

You say

"This is what we do with our alternator controller to get additional bulk charge from engine alternator - standard split charge relay that opens when 14.0v is reached."

Does this mean that if the alternator gets to 14.0v it is only 80% charged on your system? If so I probably would not need additional alternator regulation. Also if right, how do you then get it up to 100% every 4-6 weeks to synchronise the BMV? Do you increase the volatage on the alternator regulator?

Sorry for all the questions!

 

[Robbo]

Not really been following the thread, but this BMS looks interesting that may be of interest to us here as it basically looks like you can just use your own sourced cells.

http://www.rec-bms.com

 

Here's a overview of someone who's installed; 

 

Edited January 7, 2019 by Robbo

[peterboat]

44 minutes ago, Dr Bob said:

Thanks Peter. Interested in you comment on turning off the alternator. Do you know how John is doing this? For me I would be happy to manually switch of the alternator but not sure how to do this. I have it in my mind that once the alternator is going, it doesnt need a 12v supply so you cant turn it off, but I do know the alternator doesnt work if the plug on the wiring harness comes apart (before it is started up)! Is there a clever way to turn it off?

I will ask him Bob, but not all alternators are self exciting so if thats the case I would suspect he turns off the 12v to it

[nicknorman]

52 minutes ago, Dr Bob said:

Thanks Peter. Interested in you comment on turning off the alternator. Do you know how John is doing this? For me I would be happy to manually switch of the alternator but not sure how to do this. I have it in my mind that once the alternator is going, it doesnt need a 12v supply so you cant turn it off, but I do know the alternator doesnt work if the plug on the wiring harness comes apart (before it is started up)! Is there a clever way to turn it off?

Generally I think you have to insert a switch between the regulator and the alternator rotor (slip ring connection). This probably does require taking the regulator off the back of the alternator to gain access, but you would have to do the same thing to connect an external regulator eg the Arduino one we have been talking about.

1 hour ago, dmr said:

Im only half reading this thread (tut tut) are we talking about an arduino based alternator controller here, or more of a battery switch off thing? If its an alternator controller is there a circuit diagram available as well as the code?????

 

...............Dave

Alternator controller. It was open source but now that the chap has sold it commercially it is no longer on the website. T&B has offered me the source code of which he has a copy, I’ll see if he also has a schematic...

[Dr Bob]

30 minutes ago, peterboat said:

I will ask him Bob, but not all alternators are self exciting so if thats the case I would suspect he turns off the 12v to it

Thanks Peter. Look forward to finding out.

 

22 minutes ago, nicknorman said:

Generally I think you have to insert a switch between the regulator and the alternator rotor (slip ring connection). This probably does require taking the regulator off the back of the alternator to gain access, but you would have to do the same thing to connect an external regulator eg the Arduino one we have been talking about.

Alternator controller. It was open source but now that the chap has sold it commercially it is no longer on the website. T&B has offered me the source code of which he has a copy, I’ll see if he also has a schematic...

Nick,

I am not on the boat at the moment (its being painted). Its the bog standard 90A alternator on a 2002 Beta 43 engine....not sure of the make. I can post a pic but it wont be for a couple of weeks. What type of switch is needed ...not sure of how much current is involved in that circuit.....and will it just be a case of snipping the wire and bringing it back to the remote switch? Is this straightforward or do I need expert help. I am ok on 12v electrics and have been known to use a soldering iron but never touched an alternator.

[dmr]

47 minutes ago, nicknorman said:

Generally I think you have to insert a switch between the regulator and the alternator rotor (slip ring connection). This probably does require taking the regulator off the back of the alternator to gain access, but you would have to do the same thing to connect an external regulator eg the Arduino one we have been talking about.

Alternator controller. It was open source but now that the chap has sold it commercially it is no longer on the website. T&B has offered me the source code of which he has a copy, I’ll see if he also has a schematic...

Yes please, a micro-controller based alternator controller is on my list of possible interesting projects, assuming the supply of work projects dries up at some stage to allow me to get on with the hobbies ?

 

...............Dave

[roland elsdon]

Just been talking to our neighbour in his new 5th wheeler trailer. Subject of batteries came up.. yep it’s got 4 lithium’s. they are charged by the solar array on the roof.

it’s never been on mains  yet and the battery alarm goes off when the battery is at 90% capacity.

ok it’s summer in south Australia, so lots of solar. 

the system is set up for free camping,  so lights water pump  full size fridge inverter tv etc.

 

so the obvious question does it charge off the tow car.

no. There is an inverter in the tow car, that can if needed be used to run the battery charger in the van, if the solar is insufficient.

the car is a 3.2 litre diesel with uprated alternator to run the inverter. The inverter in the car will also run the air con if needed.

 

simple..

[Dr Bob]

2 hours ago, Robbo said:

Not really been following the thread, but this BMS looks interesting that may be of interest to us here as it basically looks like you can just use your own sourced cells.

http://www.rec-bms.com

 

Here's a overview of someone who's installed; 

 

That looks interesting and ideal if you were creating your own set up from single cells. Looks like about £500 (including the monitor thingy) though! Certainly seems to do most of what the BMS needs to do. Must read through the rest of his blogs. Thanks for posting.

[nicknorman]

1 hour ago, Dr Bob said:

Thanks Peter. Look forward to finding out.

 

Nick,

I am not on the boat at the moment (its being painted). Its the bog standard 90A alternator on a 2002 Beta 43 engine....not sure of the make. I can post a pic but it wont be for a couple of weeks. What type of switch is needed ...not sure of how much current is involved in that circuit.....and will it just be a case of snipping the wire and bringing it back to the remote switch? Is this straightforward or do I need expert help. I am ok on 12v electrics and have been known to use a soldering iron but never touched an alternator.

I would guess at around 5A max. Whilst I am quite familiar with the theory, I have never actually taken the regulator off an alternator. However as you say, it is just a matter of snipping the wire, taking the ends out to a switch and making sure the joins are well protected. How hard can it be?

 

Maybe one of the alternator experts will be along at some point to verify what I’m saying!

 

Anyway, fitting a switch to cut of the alternator isn’t the best way to deal with things. After you have switched off the alternator field current, any current required by the boat (lights, fridge etc) will come from the batteries which will slowly discharge. And the alternator warning light will be on, along with the audio alarm. So that would have to be dealt with as well.

[dmr]

Apologies if I have not fully grasped what the question is.

 

You can't turn an alternator off by switching off the "ignition light" feed as once the alternator is running it provides its own drive to the field winding.....this iswhy the alternator light goes out!!!!  

You can likely prevent an alternator from starting up by switching off the ign feed, but I would not risk my life, or even a set of lithiums, on this.

 

You could switch off an alternator by switching off the field current but this would involve changes within the alternator which might be fairly easy or very difficult depending upon the alternator. Fitting an external alternator controller (like an Adverc) and disabling the internal regulator would make switching off the alternator a whole lot easier.

(Advec used as an example here, Adverc would be a bad idea with lithiums, Sterling device might be ok).

 

Nicks point is interesting, once alternator is turned off then if you are running the engine (cruising!!!) then its silly to be running off the batteries, need a system to make enough volts to run the loads but not charge the batteries...this is essentially what a float mode is trying to do but not sure how that works with lithiums.

 

..............Dave

 

[Dr Bob]

45 minutes ago, nicknorman said:

25 minutes ago, dmr said:

Nicks point is interesting, once alternator is turned off then if you are running the engine (cruising!!!) then its silly to be running off the batteries, need a system to make enough volts to run the loads but not charge the batteries...this is essentially what a float mode is trying to do but not sure how that works with lithiums.

Anyway, fitting a switch to cut of the alternator isn’t the best way to deal with things. After you have switched off the alternator field current, any current required by the boat (lights, fridge etc) will come from the batteries which will slowly discharge. And the alternator warning light will be on, along with the audio alarm. So that would have to be dealt with as well.

Now that is a good point. Ok, switching off the alternator is not a good idea.

[nicknorman]

19 minutes ago, dmr said:

 

Nicks point is interesting, once alternator is turned off then if you are running the engine (cruising!!!) then its silly to be running off the batteries, need a system to make enough volts to run the loads but not charge the batteries...this is essentially what a float mode is trying to do but not sure how that works with lithiums.

 

..............Dave

 

Exactly. Hence the need for a smart alternator controller that turns the voltage down to a point where no more current flows into the batteries. Lithiums have the advantage of a well defined voltage rise at full charge, although for maximum life charging to around 80% SoC is recommended. 13.8v is a good limiting figure to avoid going above 80% or so. And there is no significant temperature coefficient.

[Dr Bob]

15 minutes ago, nicknorman said:

Exactly. Hence the need for a smart alternator controller that turns the voltage down to a point where no more current flows into the batteries. Lithiums have the advantage of a well defined voltage rise at full charge, although for maximum life charging to around 80% SoC is recommended. 13.8v is a good limiting figure to avoid going above 80% or so. And there is no significant temperature coefficient.

...and then we are back to finding a commercially available charge controller. Looks like Balmar do one but big bucks. I've emailed the guy about to launch the WS100.

I am thinking my Sterling AtoB is going to charge at a max of 14.0V (on the lowest voltage setting) but not sure how long it would hold there in Absorption. Rather than switch off the alternator, it has suddenly occured to me that I dont need to do that. I could just have a manual switch to isolate the lithium bank from the charge sources if it was getting near to 100% as per the automatic disconnect switch in the event of over voltage. Interested to hear back from Tom and Bex if their 14.0V charge took them much above  80%.

Interesting looking at Sterling's site for their LiFePo batteries.  The bumff quoted the following:

Max charge V=14.8V, Recommended =14.6V, Float V=13.8V

Pardon!!!!

14.6V charge and a 13.8V float?? Surely not?

https://www.sp-shop.co.uk/Sterling-Power-12V-120Ah-Lithium-Iron-Phosphate-Battery-with-BMS-PN-LD12120.html