Cheap LiFePO4 BMS?

[jetzi]

9 hours ago, nicknorman said:

I suspect you may find that with Li batteries at a low SoC and presuming you have decent low resistance cabling, that your alternators can produce their rated outputs. Which is probably not what you want from a overheating perspective!

Yes! This is what I'm getting at - the rated output is irrelevant. I need to know what current my alternators can practically sustain without getting too hot and while the engine is idling. If my alternator is 90A but starts getting very hot at 60A (for any reason), a 60A B2B is going to be too much, at least without adding more moving parts like blowers.

 

I don't know my alternators' rated outputs in any case. I do know that my large alternator has produced 50A under as much load as I could put on it at the time (I didn't have solar so it was a fairly pure experiment). To get a better number I really need to load it up in isolation, disconnecting it from the rest of the system. The other alternator I've never messed with and don't in truth even know where the wires go. I asked Beta who says that one is only 40A, but I have documentation saying it's 60A, so really I have no idea.

 

2 hours ago, Dr Bob said:

I think you will find this bit [manually avoiding overcharging] very easy. As the Li bank is likely most of the time to be between 20 and 80%, one glance at the BMV to see how many amphrs out(or when you get more experience just the voltage and current out ) each morning and a look out the window at the sun and you can decide if you isolate the Li's from the alternator for the day or how may hours you will run the engine for the day. 

If this is the case, then the BMS controlled relay shutoff + load dump plan, which most here only wish to employ as an emergency backup, should be adequate to prevent overcharging. Since the solar is all automatic anyway, the problem really only comes in when charging from the alternator.

 

When I'm moored up, this charging is a manual process anyway - so I look at my state of charge periodically and if it's looking too low, I run the engine for a bit. I'm used to doing this with the LA already, and since the Li's are

 

So really the only problem comes in when I'm cruising - if I go on a 7-8 hour cruise then this could indeed overcharge my Li's. In this situation I have four lines of overcharge defence:

1. keeping an eye the SoC and manually switch off the alternator charging relay (not under load to preserve relay life). If I'm about to go on a cruise I'll check my SoC and if it's more than 70% or so, I'd turn off charging before I cast off. If I forget to do this:
2. the BMS will turn off the relay at 80% (under load, but with load dump protection for the alternator, a LA battery in circuit). If this relay has burned out in an "on" position:
3. the BMS will turn off a second relay on the negative, isolating both load and charge. If this relay has burned out in an "on" position, or if the BMS has failed in a horrible way:
4. I have a redundant monitor - the ISDT BG-8S - sounding overcharge alarms.

At this point I'd still have around 15% buffer in the lithiums before I get to 100% and there is potential for damage. If relays/BMS are not working and neither Alice nor I hear the alarms, nor check the SoC in time, and continue cruising, then all bets are off. Sure - this is a layer of safety fewer than most of you, but it's still four layers of safety.

 

I'm going to be doing (1) anyway, so adding in a B2B or a DIY alternator controller is inserting an extra layer of safety between 1 and 2. To me really this step is more about protecting the alternator from overheat than the Li's from overcharge.

1 hour ago, redwing said:

Ivan, Sterling do have some 60a refurbs @ £200, And there are some new @ 240 on ebay

 

They also have the half power function that Dre mentioned the other day. Would be good to hear how he is getting on

Ooh, thanks for the tip - I actually see they have some updated "old stock" 60A ones for only 150 GBP! https://www.ebay.co.uk/itm/324071660031
Apparently they have been updated to the same functionality but more research needed. Not sure if they have the "half power" functionality - if they do, then this would be ideal for me I think.

 

And now for something completely different...

I'm shopping around for a temperature gun for my alternator. As with most gadgets there is a huge range in price. Can anyone recommend a reliable but cheap model?

Edited May 16, 2020 by ivan&alice

[Dr Bob]

5 minutes ago, ivan&alice said:

 

So really the only problem comes in when I'm cruising - if I go on a 7-8 hour cruise then this could indeed overcharge my Li's. In this situation I have four lines of overcharge defence:

1. keeping an eye the SoC and manually switch off the alternator charging relay (not under load to preserve relay life). If I'm about to go on a cruise I'll check my SoC and if it's more than 70% or so, I'd turn off charging before I cast off. If I forget to do this:
2. the BMS will turn off the relay at 80% (under load, but with load dump protection for the alternator, a LA battery in circuit). If this relay has burned out in an "on" position:
3. the BMS will turn off a second relay on the negative, isolating both load and charge. If this relay has burned out in an "on" position, or if the BMS has failed in a horrible way:
4. I have a redundant monitor - the ISDT BG-8S - sounding overcharge alarms.

At this point I'd still have around 15% buffer in the lithiums before I get to 100% and there is potential for damage. If relays/BMS are not working and neither Alice nor I hear the alarms, nor check the SoC in time, and continue cruising, then all bets are off. Sure - this is a layer of safety fewer than most of you, but it's still four layers of safety.

 

 

Agreed.

Just keep an eye on alternator temp using a cheapo model from screwfix. I got a Titan one from there for £35 a few years back. They dont sell them anymore but it looks like

https://www.screwfix.com/p/magnusson-im23-infrared-non-contact-digital-thermometer/1352x

is similar. You dont need it to be that accurate. Calibrate by pointing at a pan of boiling water and seeing how far off 100°C it is. You can then easily 'guess' the alternator temp when it is up at those sort of temps. You can also at a glance tell what your solid fuel stove is doing.

The more expenisve models that can be used to check body temp will be selling for max price but that accuracy is not needed.

[redwing]

9 minutes ago, ivan&alice said:

I'm going to be doing (1) anyway, so adding in a B2B or a DIY alternator controller is inserting an extra layer of safety between 1 and 2. To me really this step is more about protecting the alternator from overheat than the Li's from overcharge.

Ooh, thanks for the tip - I actually see they have some updated "old stock" 60A ones for only 150 GBP! https://www.ebay.co.uk/itm/324071660031
Apparently they have been updated to the same functionality but more research needed. Not sure if they have the "half power" functionality - if they do, then this would be ideal for me I think.

 

And now for something completely different...

I'm shopping around for a temperature gun for my alternator. As with most gadgets there is a huge range in price. Can anyone recommend a reliable but cheap model?

I think that listing is wrong. It says it is a BB1230 but mentions 60amps in the listing. They have put the price up twice in the last month for both the 30a and the 60a

[Dr Bob]

6 minutes ago, redwing said:

I think that listing is wrong. It says it is a BB1230 but mentions 60amps in the listing. They have put the price up twice in the last month for both the 30a and the 60a

Yes, I checked the link and it was for the 30A ones. I may be after 2* 60A units. I may call them on Monday to see what they have.

[redwing]

9 minutes ago, Dr Bob said:

Yes, I checked the link and it was for the 30A ones. I may be after 2* 60A units. I may call them on Monday to see what they have.

Just looked on their website and they're a tenner cheaper. Don't know about postage though. https://sterling-power.com/collections/clearance/products/bb1260-battery-to-battery-charger-6-months-warranty?variant=32686254470

 

Their ebay listing says they have 5 left.

[Dr Bob]

6 minutes ago, redwing said:

Just looked on their website and they're a tenner cheaper. Don't know about postage though. https://sterling-power.com/collections/clearance/products/bb1260-battery-to-battery-charger-6-months-warranty?variant=32686254470

 

Their ebay listing says they have 5 left.

Thanks for the link

[redwing]

10 minutes ago, Dr Bob said:

Thanks for the link

The price has gone up in just a few weeks from £150 to 190/200 for the 60a version.  Might be worth asking if they'll do you a deal for 2. According to the ebay listing they have sold over 100 of the 60a refurb version alone. Does beg the question why they had so many used units

[jetzi]

29 minutes ago, redwing said:

Does beg the question why they had so many used units

That also raised me eyebrow. Worth calling and asking, maybe there's a good explanation.

[jetzi]

1 hour ago, Dr Bob said:

Agreed.

Just keep an eye on alternator temp using a cheapo model from screwfix. I got a Titan one from there for £35 a few years back. They dont sell them anymore but it looks like

https://www.screwfix.com/p/magnusson-im23-infrared-non-contact-digital-thermometer/1352x

is similar. You dont need it to be that accurate. Calibrate by pointing at a pan of boiling water and seeing how far off 100°C it is. You can then easily 'guess' the alternator temp when it is up at those sort of temps. You can also at a glance tell what your solid fuel stove is doing.

The more expenisve models that can be used to check body temp will be selling for max price but that accuracy is not needed.

I think it's important to separate the lithium overcharge problem from the alternator overheat problem, even though they might have the same solution (shutting down the alternator field).

 

I feel that the overcharge problem is mostly catered for with the manual eyekeeping + BMS, but this does nothing for alternator temperature. Perhaps an idrea is to permanently mount a digital probe type thermometer to the alternator, with a display next to all other instruments, so the temperature can at least be monitored without having to go into the engine bay. A simple buzzer could be added that sounds at a set temperature - maybe this should be my first arduino project to wet my feet on the DIY controller thing.

[Dr Bob]

47 minutes ago, ivan&alice said:

I Perhaps an idrea is to permanently mount a digital probe type thermometer to the alternator, with a display next to all other instruments, so the temperature can at least be monitored without having to go into the engine bay. A simple buzzer could be added that sounds at a set temperature - maybe this should be my first arduino project to wet my feet on the DIY controller thing.

Can you do one for me while you are at it? ?

Hang about, can you buy and off the shelf one?

[peterboat]

5 hours ago, ivan&alice said:

I think it's important to separate the lithium overcharge problem from the alternator overheat problem, even though they might have the same solution (shutting down the alternator field).

 

I feel that the overcharge problem is mostly catered for with the manual eyekeeping + BMS, but this does nothing for alternator temperature. Perhaps an idrea is to permanently mount a digital probe type thermometer to the alternator, with a display next to all other instruments, so the temperature can at least be monitored without having to go into the engine bay. A simple buzzer could be added that sounds at a set temperature - maybe this should be my first arduino project to wet my feet on the DIY controller thing.

Forced cooling is a great way of keeping your alternator cool,  jag XK8 this week showed how important, the scoop had been removed by another garage alternator frazzled! New alternator and scoop fitted customer looked at bill and produced old one from boot! Garage didn't think it needed it! Shame really, for him and the other garage ?

[BEngo]

Dunno 'bout you fellers wi"t big canals oop North but us down yer dozzent go fast enough for a scoop. ( On the alternator.  Beer is altogether a different thing).

N

[peterboat]

17 minutes ago, BEngo said:

Dunno 'bout you fellers wi"t big canals oop North but us down yer dozzent go fast enough for a scoop. ( On the alternator.  Beer is altogether a different thing).

N

Problem is alternators need to be spinning fast for the fans to work, dusnt appen on boat boat engines so they work hard at low revs an get red ot lad, then thi give up ghost 

[nicknorman]

1 hour ago, BEngo said:

Dunno 'bout you fellers wi"t big canals oop North but us down yer dozzent go fast enough for a scoop. ( On the alternator.  Beer is altogether a different thing).

N

What we need are water-cooled alternators eg http://www.iskra-agv.cz/us/pdf/alternators_liquid_cooled.pdf

 

I expect they would work quite well with beer as the coolant, but you would have to drink it fairly quickly to ensure an adequate throughput.

Edited May 16, 2020 by nicknorman

[BEngo]

2 hours ago, nicknorman said:

What we need are water-cooled alternators eg http://www.iskra-agv.cz/us/pdf/alternators_liquid_cooled.pdf

 

I expect they would work quite well with beer as the coolant, but you would have to drink it fairly quickly to ensure an adequate throughput.

So each morning you could look at he SoC indicator and estimate the necessary dimensions of "a few scoops".  Then, after sufficient scooping one could tie up for an  evening beer/ wine/ creme de menthe frappe of  choice.

[jetzi]

I tested my small alternator to try to find out if/how I can use it in my lithium charging system - can anyone help me make sense of these results?

 

The positive of my small alternator is connected to the positive of my starter motor, which is connected to my starter battery positive. When I disconnected the alternator positive and turned the ignition to "on", I saw for the first time ever my battery light illuminate! I had no idea the battery light even worked, not sure what it's trying to tell me.

 

I started the engine. With nothing attached, the voltage of the small alternator is 14.32V.

 

I created a test load consisting of a 600W 12V immersion heater (theoretically 50A) element stuck down the spout of a stovetop kettle, with 6mm^2 wires, terminating in lugs to fit my alternator and battery. I tested the test rig on my domestic battery - it got very hot very quickly.

 

I connected the test load between the small alternator (the only connection on it) and battery negative. I ran the engine and measured the voltage - it showed 40mV and < 1A current, which suggests that it was putting out nothing; the element did not seem to get hot. I thought perhaps there was a bad connection. I touched the original alternator connection to the positive of the alternator/test load, a little spark and the engine audibly started labouring - I believe this was the other alternator kicking in on the test load - so I removed it immediately. At least I know the connection was sound. But weird that I see nothing from the alternator alone?!

 

Beta says the alternator is 40A. I figured it would put out as much as it could to a maximum of 50A. But is it possible that my test rig just overloaded it - should I try to find something less juicy to use?

 

--

 

Given that I know my other alternator raises the voltage to 14.63V, I think I can at least conclude from this test that the two alternators are incompatible - so I wouldn't be able to combine the two outputs into one B2B. So that's a disappointing but useful result, anyway. So my choices are 1) forget the small alternator, get a 30A B2B for the large alternator. 2) forget the B2B, start with no alternator control (relying on BMS and manual effort to not overcharge, and a heat gun to prevent overheat), and develop an arduino controller to replace the manual effort at my leisure.

 

I'm leaning towards option 2, I'll start out with 1) temperature monitoring, then 2) temperature cutoff of alternator field, then 3) voltage cutoff of alternator field, then 4) I'll consider using it to switch on a "float" regulator instead of cutting the field.

 

23 hours ago, Dr Bob said:

Can you do one for me while you are at it? ?

Hang about, can you buy and off the shelf one?

I'd certainly be happy to, if I get it right, and if you're prepared to wait the months it will take me to actually get there! It's the least I could do for all the advice you've kindly offered. One may be able to buy something off the shelf to do just the first monitoring stage, but I want to DIY it so I can extend it to stage 2-4 eventually, and I think we've well established that doesn't exist, at least not without going into triple digits GBP!

[nicknorman]

If your small alternator only has the one wire going to the battery, plus of course ground through the case, then it is probably a 6 diode machine that needs battery power to get it going (ie to send some current through the stator to create a magnetic field).

 

Since you had disconnected that source of initial power, and put a low resistance load on the alternator, there is no way the alternator could get going. All you saw was a tiny bit of output from the residual magnetism. When you touched the battery wire on, this supplied power to excite the alternator and get it going.

 

I’m not sure if the alternator would have continued to work having touched the wire and disconnected it again, it would depend on whether the load was much greater than the alternator could supply, alternator rpm etc. The best thing to do would be to leave the starter battery connected and measure both the current into the load and any current flowing in or out of the battery, using a clamp meter etc. Do you have one?
 

For the reasons above I also think you measurement of unloaded alternator voltage is probably false as the alternator probably wasn’t working properly. Again, leave the starter battery connected and wait for the voltage to stabilise after starting the engine and it putting the starter current back in (just a couple of minutes, probably) to properly measure the regulated voltage. The way you did it, at best you are measuring a voltage with a large amount of ripple on it, and that is likely to confuse a digital meter.

Edited May 17, 2020 by nicknorman

[jetzi]

20 minutes ago, nicknorman said:

If your small alternator only has the one wire going to the battery, plus of course ground through the case, then it is probably a 6 diode machine that needs battery power to get it going (ie to send some current through the stator to create a magnetic field).

The small alternator has 2 other connections, apart from the positive output - one that has two wires on it, a brown and a green/yellow, and the other has a brown with a black stripe on it. There is a third, disconnected wire (a blue one with a black stripe) nearby that looks as if it might have been connected to the alternator at some point. I did consider that it might need excitation.

 

Since these wires disappear into the 11-port battery terminal block I think they are supposed to be for things like the battery light (which illuminated when i disconnected the main positive off the alternator) and an RPM counter (not fitted).

 

29 minutes ago, nicknorman said:

The best thing to do would be to leave the starter battery connected and measure both the current into the load and any current flowing in or out of the battery, using a clamp meter etc. Do you have one?

Yes, I'm using my UNI-T clamp meter to do all these measurements. I have previously tried to measure the output of the alternator without disconnecting anything, and didn't get any current reading. Perhaps this is because the other alternator's higher voltage dominated the circuit?

 

32 minutes ago, nicknorman said:

For the reasons above I also think you measurement of unloaded alternator voltage is probably false as the alternator probably wasn’t working properly. Again, leave the starter battery connected and wait for the voltage to stabilise after starting the engine and it putting the starter current back in (just a couple of minutes, probably) to properly measure the regulated voltage. The way you did it, at best you are measuring a voltage with a large amount of ripple on it, and that is likely to confuse a digital meter.

The problem with leaving the alternator connected is that I'll see either the 13.8V odd from my solar (with engine off) or 14.6V odd from my large alternator. Should I disconnect the large alternator while I do these measurements? I'd rather not disconnect the solar because that's a whole thing - cover the panels, disconnect the solar, disconnect the battery, do the test, reconnect the battery, reconnect the solar, uncover the panels. I do have a voltage sensitive split charge relay, I'm not sure if that isolates the circuit into parts.

 

Just to note the voltage of the unconnected alternator was a very stable 14.32V, so it didn't seem like it was rippling. .

 

Here's a picture of the small alternator, you can see the two connections at the back and the blue/black wire dangling in the foreground.

 

[WotEver]

11 minutes ago, ivan&alice said:

The problem with leaving the alternator connected is that I'll see either the 13.8V odd from my solar (with engine off) or 14.6V odd from my large alternator. Should I disconnect the large alternator while I do these measurements?

Yes. And if you cover the solar you don’t need to disconnect it - it’ll have no output. 

[nicknorman]

I think somewhere earlier you said that you’d disconnected the wire from the small alternator and that it was the only wire, hence my comments, which in the light of the picture with lots or wires, are no longer relevant!

 

How about you simply disconnect the VSR so the two battery banks are not connected when under charge? Would that isolate the solar from the engine battery too?  You would easily be able to tell having disconnected the VSR, because the battery voltages would drift apart.

Edited May 17, 2020 by nicknorman

[jetzi]

I had figured it would be easier to test the voltage of the alternator in complete isolation, but since the alternator might be misbehaving under isolation I took the advice and tested it while hooked up to its starter battery.

 

2 hours ago, WotEver said:

Yes. And if you cover the solar you don’t need to disconnect it - it’ll have no output. 

I left the solar attached to my domestic so decided to risk not covering it, the risk being that I make a mistake and I leave the MPPT connected without a battery. I've been very careful not to do this as I hear is a big no no.

 

1 hour ago, nicknorman said:

How about you simply disconnect the VSR so the two battery banks are not connected when under charge? Would that isolate the solar from the engine battery too?  

Yes, the solar is attached on the domestic side. With the VSR and large alternator disconnected, that isolates the small alternator, starter battery and starter motor together.

After this disconnection, the voltage rapidly drifted to 13.0V on the starter vs 14V on the domestic (due to the solar input), so I'm sure they are isolated.

 

I started the engine, voltage dipped to 11.4ish when cranking and then climbed back up to 13.0V once it started (not the 14ish I'd expect from an alternator). When I crank I can see the starter motor drawing > 40A. After the engine starts, I read no current through the small alternator positive (well it reads 1A but I think this is noise).

 

I am leaving it for half an hour to dissipate any surface charge and then I'll check again.

 

[nicknorman]

2 minutes ago, ivan&alice said:

I had figured it would be easier to test the voltage of the alternator in complete isolation, but since the alternator might be misbehaving under isolation I took the advice and tested it while hooked up to its starter battery.

 

I left the solar attached to my domestic so decided to risk not covering it, the risk being that I make a mistake and I leave the MPPT connected without a battery. I've been very careful not to do this as I hear is a big no no.

 

Yes, the solar is attached on the domestic side. With the VSR and large alternator disconnected, that isolates the small alternator, starter battery and starter motor together.

After this disconnection, the voltage rapidly drifted to 13.0V on the starter vs 14V on the domestic (due to the solar input), so I'm sure they are isolated.

 

I started the engine, voltage dipped to 11.4ish when cranking and then climbed back up to 13.0V once it started (not the 14ish I'd expect from an alternator). When I crank I can see the starter motor drawing > 40A. After the engine starts, I read no current through the small alternator positive (well it reads 1A but I think this is noise).

 

I am leaving it for half an hour to dissipate any surface charge and then I'll check again.

 

Sounds a bit like the small alternator isn’t working. It could have been faulty for a long time, masked by the other sources of charge and the VSR.

 

If it is working “slightly” ie getting the voltage up to 13v or whatever, it could be that most of the diodes are blown just leaving a pair to rectify one phase.

 

You mentioned the warning light earlier, is the warning light for the small alternator still illuminating when the ignition switched on and goes off when engine starts?

[jetzi]

4 minutes ago, nicknorman said:

Sounds a bit like the small alternator isn’t working. It could have been faulty for a long time, masked by the other sources of charge and the VSR.

 

If it is working “slightly” ie getting the voltage up to 13v or whatever, it could be that most of the diodes are blown just leaving a pair to rectify one phase.

 

You mentioned the warning light earlier, is the warning light for the small alternator still illuminating when the ignition switched on and goes off when engine starts?

It seems quite likely that the small alternator isn't working. To be completely honest I didn't even know it existed for the first few months I owned the boat. The boat didn't come with domestic batteries (the previous owner had lithiums that he took with him) so I dropped in a 110AH to tide me over, adding the VSR to charge it from the same source as the start battery - which I presumed to be only the large alternator.

 

The warning light has never illuminated before. It illuminates only when the small alternator is disconnected and the ignition is on, and it stays on regardless of whether the engine is running.

 

--

I retested the voltage, it was at 12.86V whether engine was on or off and not showing any current. That sounds like the alternator isn't doing anything, right? And if Beta is correct and it's only 40A, might not be worth trying to fix. They mentioned that there are alternator upgrades available - perhaps it would be worth replacing this one with the largest that will fit in its place.

[WotEver]

40 minutes ago, ivan&alice said:

I retested the voltage, it was at 12.86V whether engine was on or off and not showing any current. That sounds like the alternator isn't doing anything, right?

Right.

[nicknorman]

1 hour ago, ivan&alice said:

It seems quite likely that the small alternator isn't working. To be completely honest I didn't even know it existed for the first few months I owned the boat. The boat didn't come with domestic batteries (the previous owner had lithiums that he took with him) so I dropped in a 110AH to tide me over, adding the VSR to charge it from the same source as the start battery - which I presumed to be only the large alternator.

 

The warning light has never illuminated before. It illuminates only when the small alternator is disconnected and the ignition is on, and it stays on regardless of whether the engine is running.

 

--

I retested the voltage, it was at 12.86V whether engine was on or off and not showing any current. That sounds like the alternator isn't doing anything, right? And if Beta is correct and it's only 40A, might not be worth trying to fix. They mentioned that there are alternator upgrades available - perhaps it would be worth replacing this one with the largest that will fit in its place.

Yes. The technical term is “knackered”.

 

I think the recent Betas tend to have 45A engine battery alternators, so you probably can’t go up much. Still, 50% is 22.5A which will make a difference. But the cheapest solution would be to get it overhauled and get yourself 50% of 40A, ie 20A extra for you Li battery charging.

 

Presumably it is on the same belt that drives the water pump, so you need something there to keep the water pump spinning, which would mean you can’t run the engine with that alternator away at the repair shop.

Edited May 17, 2020 by nicknorman