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Cheap LiFePO4 BMS?

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58 minutes ago, Dr Bob said:

Let me know how you get on researching the Balmar regulator and how easy it is to fit to your alternator. What alternator have you got and what sort of volatges/currents do you get out of it with your LAs?

 

One thing I have found very useful was to have the Rasp Pi installed and working to monitor the power prior to the Li's as it gives you a good way to look at the data. If you are looking at doing it, you have plenty of time while your mull over the Li issues. :)

 

When I put my Li's on, my initial view in March when I got the batteries was to only charge the Li's via solar and see how the alternator would work the the Li's - being prepared to just disconnect them manually after an hour if I couldnt control the termination voltage etc. This was as we moved towards summer and our normal boating ....ie 2-3 hours a day of cruising. I was thinking as we got to winter when moored up most of the time, I would be running the engine for an hour or two a day to heat the water and therefore I could manage any 'overcharging'. I wasnt really aware at that time of the potential to destroy the alternator with high current/temperature. For us, 'winter mode' is very different to 'summer mode' and once I have put a bilge blower on to blow cold air from the bottom of the engine bay onto the alternator then it should be ok to run the AtoB on a higher setting and get 60A-70A out for an hour without getting over 95°C. I'll report back once I have fitted it next week.

This is my alternator. According to that post I found a sticker on the regulator which led me to believe it was used in a Renault Clio. Thinking about it now though, perhaps that was just the regulator? I get 90 amps from it quickly reducing to 60ish before slowing down.

 

regarding the alternator temperature, where do you measure it? And with what, a turkey probe?

2 minutes ago, Detling said:

overdo it and the fuse effect will provide a rapid disconnect for you.

This just gets better and better!

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1 hour ago, WotEver said:

The spec might tell you, but probably not. I’d suggest that there are more N-type Alts around than P-type as standard. All it means is that the regulator is in the +ve feed to the field (‘P’) as opposed to in the -ve connection (‘N’). 
 

Some alternators are simple to convert from N to P, some aren’t. Obviously, some come as standard as P-type. Best to speak to your friendly alternator specialist. 

 

Hmm I may know one, coincidentally in Nuneaton, but that's miles away at the moment ?

 

 

16 minutes ago, PeterF said:

I just noticed they only do P type, some external regulators can be bought in both flavours, my alternator is P type. I have the 614 regulator, faff to program but very flexible. You could argue that it may not need the BMV to dhut it down as it has a proper float setting, so use that to limit the charge and then use the BMV as overcharge protection isolating ignition to the Balmar.

 

According to the installation notes of a Sterling Alternator Regulator left to me by the previous owner, my alternator is a Negative type.

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59 minutes ago, BEngo said:

Strikes me ths best way to charge LI standing alone would  be  to find a modern ECU linked alternator and control its output via its LlN interface.  The alternator is then "Standard" so is easily replaced if the magic smoke escapes.

That of  course requires an understanding of LIN and something to emulate the ECU and decide what voltage and/or current to demand from the alternator. Another raspberry job?

Any one know owt about LIN?

N

Absolutely agree and I’ve been thinking about this. I’m not sure I’d find a LIN interfaces alternator of a similar size to ours (175A) as I’d imagine car alternators are a lot smaller, and lorry ones tend to be 24V. So I’ve been looking at the NXP AR6000 regulator chip. About £8 in one off quantities. Then control it via a PIC with a LIN interface chip. Hardware dirt cheap but of course software to be developed. Probably not that hard! The PIC could also be used to measure alternator temperature. And I’ve been thinking  about a cheap and cheerful way to measure both the alternator current and battery current using Hall effect sensors. No very accurate, but high accuracy not required.

 

PIC could reduce regulated voltage and or max field current in response to alternator temperature. And once the combination of battery current and voltage indicates the desired state of charge, it would reduce the regulated voltage to 13.3 or whatever  so as to stop charging the battery whilst still supplying any boat loads.

 

One think I’m not sure about is what the maximum field current of such an alternator would be (Iskra 175A jobbie) as the max current through the AR6000 is 12A. Is there a rule of thumb for max field current vs alternator output?

 

Microchip does a LIN bus analyser for about £60 which would help develop the communications software. I’ve never used LIN before but how hard can it be, especially with just 1 slave and non-time-critical control.

 

I’m on the cusp of ordering the chip and analyser, trouble is I have a lot else going on at the moment so it will have to wait! It does look like there would be a market for an integrated system that monitors things and controls the alternator. But of course, some hardware mods required to the alternator to remove the existing regulator and take the field and phase wires out to an external circuit.

Edited by nicknorman

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4 minutes ago, nicknorman said:

Absolutely agree and I’ve been thinking about this. I’m not sure I’d find a LIN interfaces alternator of a similar size to ours (175A) as I’d imagine car alternators are a lot smaller, and lorry ones tend to be 24V. So I’ve been looking at the NXP AR6000 regulator chip. About £8 in one off quantities. Then control it via a PIC with a LIN interface chip. Hardware dirt cheap but of course software to be developed. Probably not that hard! The PIC could also be used to measure alternator temperature. And I’ve been thinking  about a cheap and cheerful way to measure both the alternator current and battery current using Hall effect sensors. No very accurate, but high accuracy not required.

 

PIC could reduce regulated voltage and or max field current in response to alternator temperature. And once the combination of battery current and voltage indicates the desired state of charge, it would reduce the regulated voltage to 13.3 or whatever  so as to stop charging the battery whilst still supplying any boat loads.

 

One think I’m not sure about is what the maximum field current of such an alternator would be (Iskra 175A jobbie) as the max current through the AR6000 is 12A. Is there a rule of thumb for max field current vs alternator output?

Put me down for one of the first units.:)

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5 minutes ago, Dr Bob said:

Put me down for one of the first units.:)

Yes, could be a while though! Life is too busy!

4 hours ago, Mike the Boilerman said:

Is not there not a problem with paralleling multiple small cells? 

 

As the cells each probably degrade/lose capacity/fail at slightly different rates, would you not end up persistently passing too many coulombs through the faster degrading ones and accelerating the degradation? And vice versa on discharge? Or do the better cells take up the strain and give the poorer ones an easier time?

 

No I don’t think so. This is surely how the valence batteries are constructed - lots of small cells in parallel (and then in series).  I think each cell would accept/deliver current in proportion to its capacity. So the degraded ones would take and deliver less current, just as would happen with LAs in parallel.

As I mentioned, the cell voltages in a parallel group must be identical, so there is no risk of one cell being over/under charged and that being masked by the other cells in parallel.

Edited by nicknorman
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24 minutes ago, eid said:

regarding the alternator temperature, where do you measure it? And with what, a turkey probe?

 

I use my infrequent red thermometer. Lift the buffalo board and point it at the alternator.

I measure the temp on the top half way between the pulley and the back and then again by shining it on the back face where the diode pack is (or where I think it is!). Top temp I try to keep below 95°C and the back face seems to not go above 75°C. Not a clue how accurate the IR thermometer is but the top of the engine is around 75°C when hot. I've got zero air circulation in the engine bay at the moment.

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2 minutes ago, Dr Bob said:

I use my infrequent red thermometer. Lift the buffalo board and point it at the alternator.

I measure the temp on the top half way between the pulley and the back and then again by shining it on the back face where the diode pack is (or where I think it is!). Top temp I try to keep below 95°C and the back face seems to not go above 75°C. Not a clue how accurate the IR thermometer is but the top of the engine is around 75°C when hot. I've got zero air circulation in the engine bay at the moment.

Yikes!

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6 hours ago, Richard10002 said:

Hi Peter,

 

The stuff I have seen suggests that the internal BMS stuff balances the cells at the end of an absorption period, which suggests that you have to charge them to the highest voltage every now and then in order to make this happen. Seems to make sense.

 

However, you then mention a "master BMS" which I havent heard you talk about before. Is this the Valence BMS that Lithiumwerks say these batteries need, or a different BMS?

 

BTW: Are your Valences the green ones, or the black ones that we are seeing for sale?

Black batteries Richard, the batteries passively balance, I have watched it on numerous occasions, its what happens with closely matched cells, there are 400 hundred cells in every battery if I remember rightly, which is why they cost so much dosh in comparison to other batteries?

There are two types of master BMSs around low voltage and high voltage they have to be programmed in to work, and they wont sell you one!! However a nice chap in NI who used to be on the speak EV forum told me they self balanced he repaired Smith electric vans for a living so knew the score, also the geek from the USA said the same, so in practice they are right they do self balance as every user of them knows and their are a lot of them, we stick to the 20-80% mantra because it makes sense and enjoy cheap s/h LifePo4 batteries I like you over thought the problem in the beginning but now just ignore the batteries as I know they stay in balance easy for me to say I know

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Just catching up on the past few days of messages.

I'd advise at least having a panel voltage meter with 3 decimal places of precision. Over time you develop a "feel" for the state of charge based upon the voltage.

In our system, we had no bms or cell level monitoring.

In the early days, we didn't know what limits to work to, and had very little instrumentation, no ammeters etc...

 

The measured voltage predominantly depends on two things; state of charge and load/charging current. When the batteries are in a rested state I.e. Very little load/charging current for a couple of hours or so, the voltage is a very accurate indicator of state of charge. For us, 13.330V fully charged 13.200V middle ish. 13.100V middle to low, 13.000V we try to avoid going too much lower than this.

At either end of the charge curve, you notice the voltage fluctuates much more.

For the first few months after installation, we kept the voltage around the 13.2V region. As we later installed the various safety systems, we became a little more adventurous, and carefully explored the upper and lower ends of the characteristic.

 

While charging, the measured voltage will be higher than the resting voltage, and will depend on the charging current and state of charge. Annoyingly, charging current depends to a certain extent on alternator RPM.

During the middle three quarters of the capacity curve, the voltage doesn't change a great deal as the batteries are charged. For example if the alternator is kicking out 80A, at about 50% SOC we might see ~13.6xxV for well over an hour. This is where the extra decimal places on the meter really help. The numbers will slowly be counting up as the batteries charge e.g. 13.614 ... 13.615 etc... You get a good feel for the rate of charge.

When approaching about 80% (what we call full), the voltage starts to rise quite rapidly. The last decimal place becomes a bit irrelevant at this point because of the speed the voltage is moving. At somewhere between 13.9 and 14.0V, we cut the alternator field and charging stops.

The battery voltage rapidly drops to say 13.4xxV. It then takes an hour or so, depending on load current, for the voltage to settle out at the resting voltage value.

 

When choosing a voltage to cut the alternator off at, we were initially very over cautious. The problem with setting it too low e.g.13.7V is that the dependence of charge current on engine RPM means that while traveling, revving the engine might cause the current to ramp up momentarily. This causes the measured voltage to increase, and hence lead to premature tripping.

 

As we got more accustomed, and understood what was happening, the trip threshold was gradually increased. We're now quite happy with a value around 13.95V. Providing the alternator is supplying sufficient current, the voltage does not remain at this high value for any significant length of time. Once the voltage has passed about 13.7V, it really does start to rise quite quickly, accelerating as it goes. The alternator cut off threshold is then tripped cleanly and is far less susceptible to premature triggering.

 

This strategy gives a clean cut off at a consistent state of charge.

 

It would be nice to either control the alternator current to a set value, or compensate for its variation using a software battery model.

 

To summarise; the measured voltage is mainly determined by the battery, which is predominantly dependant on state of charge and load / charging current.

With LA batteries, the alternator is required to regulate the voltage while the battery absorbs the energy.

 

In my opinion an alternator voltage regulator is not needed for lithium unless you wish to either fully charge the batteries to 100% using CI/CV mode, or wish to regulate alternator temperature/engine load, or if the alternator current rating is too high for the capacity of the battery pack.

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On 31/10/2019 at 00:25, Richard10002 said:

I can't see that it's been mentioned yet, but it looks like that bms requires a minimum of 7 cells connected to it? Fine for 24v system but not 12v. Not liked any closer at it though. 

 

On 03/11/2019 at 16:43, eid said:

Why can't he use an isolator switch connected to a Victron BMV to cut the charge at 13.9V like you did?

One of the biggest individual component costs is the actual remote isolator itself (either motorised switch, or bi-stable relay and control circuit). 

 

On 03/11/2019 at 20:48, Richard10002 said:

If LiFePo4 batteries survive for the number of cycles predicted, they are actually incredibly cheap.

 

Completely agree, particularly if putting the system together yourself. 

 

On 03/11/2019 at 20:50, MoominPapa said:

The point is that if you charge to a cut-off voltage of (say) 14.0v and then terminate the charge, then your battery will have a lower SoC at termination if you have 100A alternator than if you have a 50A alternator. 

 

 

The equation of a set-point voltage with a limit SoC is _very_ approximate.

 

MP. 

But does it actually matter that much if they are 80% or 90% charged when you hit the voltage set-point? It also depends how discharged they are before charging commences. 

 

On our system, they seem to hit 14.0v anywhere between 80-95% charged. Actual value depends on how discharged they were, engine speed, and if charging from one or both alternators. When charging from just engine start battery alternator, which only puts out 30-40a, they would hit nearly 95% if starting from low soc. That was the point voltage had climbed to 14.0v, by which time current had dropped to 25a or so.

 

From my observation of charging at varying currents ranging from 100a down to 30a, I still believe charging to a set voltage of 14.0v will not overcharge them, and will give a finishing charge of around 80-90% - more than adequate for most users. 

 

On 03/11/2019 at 20:53, eid said:

 

And this doesn't take into account the endless hours running an engine to charge LA to 1% tail current. This alone makes it worth it for me.

And this was one of the main driving factors for us. We're not really high power consumers, but still managed to kill a set of LA's in just over 12 months. I do find us using more power now we don't have to think about conserving batteries as much though. 

 

On 03/11/2019 at 21:05, Richard10002 said:

Agreed... I did that sum earlier today, and figured a saving of about £300 a year in petrol for the genny, assuming 6 months of genny running, and 6 months of solar.

 

 

It's pretty much a no brainer assuming that we can avoid destroying the batteries. Given that I have killed 4 sets of LA batteries in 8 years, I'm a bit wary of doing the same to Lithiums :( 

You might find your solar gives more than 6 months. One of the big surprises for us was just how much better our solar was with lithiums. 

 

We've managed over 12 months and not managed to kill our lithiums yet! Our last set of LA's were down to under 50% capacity after just 12 months. 

 

16 hours ago, PeterF said:

I do not know the answer to that. What I do know is with Balmar regulator you could set the voltage down to 13.9V and set a float at 13.2. You would need to disable the voltage regulator in the alternator to go that low. The Balmar regulator also monitors the alternator temperature and reduces field (and hence charge) current if it gets too hot. You can also limit the maximum field current to effectively derate the alternator output. You can install a relay on the ignition line to the Balmar regulator driven by the BMV to turn the alternator field current off when the BMV requests rather than needing a dump battery. However, this is getting well away from the cheap BMS idea, but if I was specifying a full Victron type system, this is how I would handle the alternator, rather than using an LA dump battery.

Very similar to our setup. Unfortunately the regulator we paid around $80 for has now gone commercial and retails for around $500! Main difference is ours also monitors current, so intelligently switches to float based on voltage and tail current. Also monitors current in float mode to keep it as close to 0a as possible instead of relying on a fixed float voltage. Not sure what we'd do if ours ever packs up!

 

16 hours ago, eid said:

Not cheap at £320 but it seems to deal with all of the problems raised in an alternator based lithium install. With this, some used cells, and the necessary isolators/BMS I'd still consider this a cheap system when compared to Victrons offering.

 

As above, thiis is very similar to what we use. Does require alternator modification though. Very easy to DIY on an a127 alternator, not sure on others though.

 

16 hours ago, Dr Bob said:

Before I got my Li's, I looked at the Balmar regulator but was put off by the number of wires needed to be required ....and not a clue how to interface it to my 90A Beta 43 bog standard alternator.

 

Not really that many wires needed. Very easy mod on a127 alternator!

 

10 hours ago, Mike the Boilerman said:

Is not there not a problem with paralleling multiple small cells? 

 

As the cells each probably degrade/lose capacity/fail at slightly different rates, would you not end up persistently passing too many coulombs through the faster degrading ones and accelerating the degradation? And vice versa on discharge? Or do the better cells take up the strain and give the poorer ones an easier time?

Multiple small cells in parallel are considered better for high current applications. That's why all major ev manufacturers use this setup. Multiple C discharge rates are possible like this. 

 

8 hours ago, eid said:

Regarding Balmar regulators:

 

 

My alternator has a regulator fitted to it which I would think is internal. Peter mentioned earlier that I may have to remove this (I guess this turns mine into an "externally regulated alternator").

 

However, how do I know if it is "P-type"?

Most alternators fitted to canal boats will have internal regulators. Some are easy to modify. Basically to disable internal regulation you need to connect directly onto the brushes, and remove any other connection to brushes. (Technically only the regulated brush, the other can remain connected to ground or +12v).

 

 

 

Regarding the Valence batteries currently on Ebay, I'm seriously considering getting one of the higher cycle ones and putting it in our camper. Not sure if 1500 cycles is a bit high though, and even then I'd have trouble justifying the £250!

 

@peterboat what do you think? And does the internal bms create any problems with self discharge if not in use?

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54 minutes ago, Craig Shelley said:

Just catching up on the past few days of messages.

I'd advise at least having a panel voltage meter with 3 decimal places of precision. Over time you develop a "feel" for the state of charge based upon the voltage.

In our system, we had no bms or cell level monitoring.

In the early days, we didn't know what limits to work to, and had very little instrumentation, no ammeters etc...

 

The measured voltage predominantly depends on two things; state of charge and load/charging current. When the batteries are in a rested state I.e. Very little load/charging current for a couple of hours or so, the voltage is a very accurate indicator of state of charge. For us, 13.330V fully charged 13.200V middle ish. 13.100V middle to low, 13.000V we try to avoid going too much lower than this.

At either end of the charge curve, you notice the voltage fluctuates much more.

For the first few months after installation, we kept the voltage around the 13.2V region. As we later installed the various safety systems, we became a little more adventurous, and carefully explored the upper and lower ends of the characteristic.

 

While charging, the measured voltage will be higher than the resting voltage, and will depend on the charging current and state of charge. Annoyingly, charging current depends to a certain extent on alternator RPM.

During the middle three quarters of the capacity curve, the voltage doesn't change a great deal as the batteries are charged. For example if the alternator is kicking out 80A, at about 50% SOC we might see ~13.6xxV for well over an hour. This is where the extra decimal places on the meter really help. The numbers will slowly be counting up as the batteries charge e.g. 13.614 ... 13.615 etc... You get a good feel for the rate of charge.

When approaching about 80% (what we call full), the voltage starts to rise quite rapidly. The last decimal place becomes a bit irrelevant at this point because of the speed the voltage is moving. At somewhere between 13.9 and 14.0V, we cut the alternator field and charging stops.

The battery voltage rapidly drops to say 13.4xxV. It then takes an hour or so, depending on load current, for the voltage to settle out at the resting voltage value.

 

When choosing a voltage to cut the alternator off at, we were initially very over cautious. The problem with setting it too low e.g.13.7V is that the dependence of charge current on engine RPM means that while traveling, revving the engine might cause the current to ramp up momentarily. This causes the measured voltage to increase, and hence lead to premature tripping.

 

As we got more accustomed, and understood what was happening, the trip threshold was gradually increased. We're now quite happy with a value around 13.95V. Providing the alternator is supplying sufficient current, the voltage does not remain at this high value for any significant length of time. Once the voltage has passed about 13.7V, it really does start to rise quite quickly, accelerating as it goes. The alternator cut off threshold is then tripped cleanly and is far less susceptible to premature triggering.

 

This strategy gives a clean cut off at a consistent state of charge.

 

It would be nice to either control the alternator current to a set value, or compensate for its variation using a software battery model.

 

To summarise; the measured voltage is mainly determined by the battery, which is predominantly dependant on state of charge and load / charging current.

With LA batteries, the alternator is required to regulate the voltage while the battery absorbs the energy.

 

In my opinion an alternator voltage regulator is not needed for lithium unless you wish to either fully charge the batteries to 100% using CI/CV mode, or wish to regulate alternator temperature/engine load, or if the alternator current rating is too high for the capacity of the battery pack.

Which fits very well with my observations, that just having a set voltage cutoff for alternator charging would work very well. Like you, we were quite cautious with voltage settings initially, but increased both alternator and solar voltage to 14.0v based on observation and experience.

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7 hours ago, Tom and Bex said:

 

But does it actually matter that much if they are 80% or 90% charged when you hit the voltage set-point? It also depends how discharged they are before charging commences. 

 

 

Depends if the error is systematic or random. If you're using charge termination to synchronise an Ah based SoC indicator, than it adds a large source of error to that. My last cycle between full charges was 13 days, and included trips down to 10% charge. When the charge terminated after recharging, the SoC was still accurate to within 3%. Adding 10% potential error to that would be a big deal. The absolute  SoC doesn't matter, but repeatability does: I want to be able to go down to less than 10% and be confident of not getting a low-voltage cutoff cause the last charge ended 10% before it should have.

 

MP.

 

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These last three posts are incredibly helpful, especially Craig's suggestion of getting a volt meter reading to three decimal places. 

 

I'm currently using the display on my Smartgauge which despite displaying two decimal places, only has a resolution of one decimal place. The second digit is always zero! 

 

Which volt meter are you using please, Craig? A brief search of ebay reveals nothing that measures to three decimal places. 

 

 

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2 minutes ago, Mike the Boilerman said:

 

These last three posts are incredibly helpful, especially Craig's suggestion of getting a volt meter reading to three decimal places. 

 

I'm currently using the display on my Smartgauge which despite displaying two decimal places, only has a resolution of one decimal place. The second digit is always zero! 

 

Which volt meter are you using please, Craig? A brief search of ebay reveals nothing that measures to three decimal places. 

 

 

Use a cell monitoring meter. Only £25. Two places for the overal bank voltage and 3 places for the individual cells.

 

 

Paper 2 Fig 5.jpg

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8 hours ago, Craig Shelley said:

The measured voltage predominantly depends on two things; state of charge and load/charging current. When the batteries are in a rested state I.e. Very little load/charging current for a couple of hours or so, the voltage is a very accurate indicator of state of charge. For us, 13.330V fully charged 13.200V middle ish. 13.100V middle to low, 13.000V we try to avoid going too much lower than this.

 

It is great to see this sort of data as it does help others understand what is going on.

I have produced the graph below before ....for our system.... which shows the behaviour of our voltage vs Ahrs. It is a good straight line from 13.3V down to 12.85V  from high to low SoC but is a steeper line than Craig has. Each system will be different so important to work out what the voltage relationship to amphrs in/out is for your system. It is very accurate for our system.

For my graph, once below 12.8V, the graph flattens out as power starts to be taken from my LA bank so it is pointless trying to infer stuff below 12.8V. My bottom limit is 12.7V for the LiFePO4s although I am not sure what SoC that is as I am not really sure of the capacity of the bank. It has a nameplate capacity of 480Ars but I reckon it might be 20-25% below that. I am not in  the bottom knee at 12.7V so likely the total capacity is >350Ahrs.

 

Note, the graph was drawn from a data dump of all voltage/Ahr readings (800 of them) where the current  was = 0 ie at rest. The problem was, when the charge current is removed during charging, the current drops to 0 but the voltage is slightly high for 5-10 mins - hence the points under the red area are too high....ignore those. This is data from early summer. 5 months later it is still spot on.

Screen Shot 2019-11-05 at 10.04.03.png

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8 hours ago, Tom and Bex said:

I can't see that it's been mentioned yet, but it looks like that bms requires a minimum of 7 cells connected to it? Fine for 24v system but not 12v. Not liked any closer at it though. 

 

One of the biggest individual component costs is the actual remote isolator itself (either motorised switch, or bi-stable relay and control circuit). 

 

Completely agree, particularly if putting the system together yourself. 

 

But does it actually matter that much if they are 80% or 90% charged when you hit the voltage set-point? It also depends how discharged they are before charging commences. 

 

On our system, they seem to hit 14.0v anywhere between 80-95% charged. Actual value depends on how discharged they were, engine speed, and if charging from one or both alternators. When charging from just engine start battery alternator, which only puts out 30-40a, they would hit nearly 95% if starting from low soc. That was the point voltage had climbed to 14.0v, by which time current had dropped to 25a or so.

 

From my observation of charging at varying currents ranging from 100a down to 30a, I still believe charging to a set voltage of 14.0v will not overcharge them, and will give a finishing charge of around 80-90% - more than adequate for most users. 

 

And this was one of the main driving factors for us. We're not really high power consumers, but still managed to kill a set of LA's in just over 12 months. I do find us using more power now we don't have to think about conserving batteries as much though. 

 

You might find your solar gives more than 6 months. One of the big surprises for us was just how much better our solar was with lithiums. 

 

We've managed over 12 months and not managed to kill our lithiums yet! Our last set of LA's were down to under 50% capacity after just 12 months. 

 

Very similar to our setup. Unfortunately the regulator we paid around $80 for has now gone commercial and retails for around $500! Main difference is ours also monitors current, so intelligently switches to float based on voltage and tail current. Also monitors current in float mode to keep it as close to 0a as possible instead of relying on a fixed float voltage. Not sure what we'd do if ours ever packs up!

 

As above, thiis is very similar to what we use. Does require alternator modification though. Very easy to DIY on an a127 alternator, not sure on others though.

 

Not really that many wires needed. Very easy mod on a127 alternator!

 

Multiple small cells in parallel are considered better for high current applications. That's why all major ev manufacturers use this setup. Multiple C discharge rates are possible like this. 

 

Most alternators fitted to canal boats will have internal regulators. Some are easy to modify. Basically to disable internal regulation you need to connect directly onto the brushes, and remove any other connection to brushes. (Technically only the regulated brush, the other can remain connected to ground or +12v).

 

 

 

Regarding the Valence batteries currently on Ebay, I'm seriously considering getting one of the higher cycle ones and putting it in our camper. Not sure if 1500 cycles is a bit high though, and even then I'd have trouble justifying the £250!

 

@peterboat what do you think? And does the internal bms create any problems with self discharge if not in use?

No problems really they can go months between charges as I have found out.

I think my solar charging gets rid of a lot of problems, it allows me to charge up a real 13.8 volts, I can see the amps going down as it finishes until it shows no amps going in, float is at 13.6 volts so as soon as the fridge kicks in it starts charging again, I also have a 12 volt computer fan running constantly at a very small drain on the toilet.

I think we become relaxed with these batteries as time goes on, something which people with LAs dont understand, as they only see expensive problems, whereas we just see them as a simple solution to charging quickly and cheaply?

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3 hours ago, peterboat said:

I think we become relaxed with these batteries as time goes on, something which people with LAs dont understand, as they only see expensive problems, whereas we just see them as a simple solution to charging quickly and cheaply?

The problem that some of us have is with anecdotal ‘evidence’ as opposed to factual explanations. For instance, you float your batteries at 13.6V. That would eventually overcharge them but you have a small fan and the occasional fridge cycle that prevents that from happening. 
 

Most users of the Valence batteries ‘believe’ that the internal BMS keeps the cells balanced. But does it? Where is that documented?

 

I don’t believe anyone doubts your experience with these batteries but we’d like better explanations than ‘it just works’. We’d like to understand why. 

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3 minutes ago, WotEver said:

The problem that some of us have is with anecdotal ‘evidence’ as opposed to factual explanations. For instance, you float your batteries at 13.6V. That would eventually overcharge them but you have a small fan and the occasional fridge cycle that prevents that from happening. 
 

Most users of the Valence batteries ‘believe’ that the internal BMS keeps the cells balanced. But does it? Where is that documented?

 

I don’t believe anyone doubts your experience with these batteries but we’d like better explanations than ‘it just works’. We’d like to understand why. 

That's the problem with LiFePO4s. They just work. Once you have had them for 6 months you forget about them. ?

 

Peter, why not do a screen grab of one or two of your batteries to show it is balanced?

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1 hour ago, WotEver said:

The problem that some of us have is with anecdotal ‘evidence’ as opposed to factual explanations. For instance, you float your batteries at 13.6V. That would eventually overcharge them but you have a small fan and the occasional fridge cycle that prevents that from happening. 
 

Most users of the Valence batteries ‘believe’ that the internal BMS keeps the cells balanced. But does it? Where is that documented?

 

I don’t believe anyone doubts your experience with these batteries but we’d like better explanations than ‘it just works’. We’d like to understand why. 

Tony it cant overcharge it because no amps are going in, and thats on the Midnite controller and the NASA gauge, they both drop to zero and when the batteries go down to 13.6 volts its starts charging again. As for the internal BMS its live the flashing light says it is, on the 36 volt version I have disconnected the BMS  and the reconnected it and it has reset itself to a green flashing light  which is good, when I connect the puter I see balanced cells which is good and thats either on a charge cycle or discharge cycle, I have had a master HV BMS in my hand its not a big bit of kit and it plugs into the end of the string of batteries, so maybe it just terminates charging to that string of batteries lets them self balance then finishes of the cycle? the answer is I dont know, but whilst my batteries remain balanced and so do other users I think we can safely say the internal BMS does something.

As for Valence they tell you nowt, as far as they are concerned they dont want second life batteries out there, the only reason I have my 36 volt ones is that they wanted to charge the bus company to dispose of them. So they sold them to James and I, we bought 60 of them between us, and they are now onto their second life driving my boat and his

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1 hour ago, Dr Bob said:

That's the problem with LiFePO4s. They just work. Once you have had them for 6 months you forget about them. ?

 

Peter, why not do a screen grab of one or two of your batteries to show it is balanced?

I have before I put on a video  of it on charge and discharge, if I have time before I go to Egypt I will, do you want that Article by the way? I go on 2 weeks holiday from Monday

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18 minutes ago, peterboat said:

As for the internal BMS its live the flashing light says it is, on the 36 volt version I have disconnected the BMS  and the reconnected it and it has reset itself to a green flashing light  which is good

Where are these lights? On the batteries or on something external?

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20 minutes ago, WotEver said:

Where are these lights? On the batteries or on something external?

On the batteries when they are charged they flash green every 20 seconds, when they are discharged below a certain voltage they flash red every 5 seconds, when they are nearly flat they go solid red, and when they are connected to the puter they flash green every five seconds. having striped down a 36 volt battery I can say that the BMS is attached to the cells, I have three 36 volt batteries that are flashing red I hope to make two good ones from them

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On 03/11/2019 at 21:05, Richard10002 said:

Agreed... I did that sum earlier today, and figured a saving of about £300 a year in petrol for the genny, assuming 6 months of genny running, and 6 months of solar.

 

So I should save my £1500 in 5 years on fuel alone.

 

It's pretty much a no brainer assuming that we can avoid destroying the batteries. Given that I have killed 4 sets of LA batteries in 8 years, I'm a bit wary of doing the same to Lithiums :( 

Not realy? I am on my eighth boat as I buy one that suits my lifestyle at any given time. Sticking several hundred pounds into batteries and associated paraphanalia only makes sense if you are deffo not selling for several years so you are partly locking yourself into something uneccesarily. If I change boats I would not be paying extra money out for someones battery choice just like I wouldnt give extra if the tanks happened to be full of diesel, another consumable.

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