An affordable way to fit Lithium Batteries?

[Dr Bob]

1 minute ago, WotEver said:

Nope, I’ll go take a look at the crimping one now... I bet I agree with him

I'm sure you will!!

 

........but I followed MPs lead and got one of those £40 jobbies from fleabay and it seemed to do the business on 50mm cable. It's working today. Then again it's not a lumpy water boat going crash, bang etc for hours on end. In that case maybe you do need better

[Dr Bob]

Ok, just a update on how my system is getting on.

A few weeks back on a different thread (which I now cannot find), we were discussing the potential to overcharge my Li's with the 500W of solar if I was near to 100% on the Li's and the sun was shining. The lack of sun early June made test this difficult

In the last 2 weeks however, I have been 'pushing' my system to try and get to 100% SoC via the alternator and Solar. Today I have given up. With the solar mppt set at 14.2V Absorption and 13.6V float, as soon as I get over 80% ish SoC ie around 100Ahrs short of full, the mppt is going into float. At that state of charge and putting in 20A from the solar the charge voltage is around 13.7V so the mppt decides it has had enough absorption and reduces the current. Today I am seeing around 5A going in to the batteries and as I am now 70Ahrs short of full, the solar will never get it to 100%.

Exactly the same is happening with the alternator and its Sterling AtoB controller. As the charge voltage gets to 13.7V (80% SoC ish), it seems to be cutting back the charge current to 20A so unless I was doing a 10 hour day, I dont think I would get near to full. Below 80% the batteries are taking full whack. My system therefore seems 'perfect' in the charge devices throttling back on getting full therefore never exposing me to overcharging. In the nine weeks we have been out and about, it has never got to the autodisconnect. There is the auto disconnect function if the overall voltage, the cell voltage or the temperature go over set limits.

[Dr Bob]

6 hours ago, cuthound said:

Whilst you are correct that a lead acid will sulphate most quickly if fully discharged and left in that state, sulphation starts immediately the battery begins to discharge.

 

The longer the sulphate is left before recharging, the harder it becomes to remove, and only high charging voltages will remove the last of it, and then only if it has not had the opportunity to fully harden.

 

I suspect that your lead acid battery will gradually sulphate over a period of a year or two if not regularly fully charged.

Cuthound

I have been struggling to find info on the web about charging/discharge when full and particularly references around steric hinderance/ depletion of ions around the active sites/diffusion. I wonder in your experience if you have seen anything that could give us a clue to the 'end of charge' data?

Obviously at the end of a charge cycle (where the batteries were down at 50% SoC at the start), the last 1% of charge is going to go in very slowly ......as per my long chemistry orientated post above. What though happens on a full battery, discharged to 99% SoC but then recharged?

I have been faffing round with my system today trying to get more oooomph out of the the MPPT and saw the following:

I have 2 separate BMVs on the Li and LA banks. There was a load of around 12A ....from the fridge compressor, the Inverter, numerous charging laptops and the TV. The sun was putting in circa 9A to 15A (cloudy, sunny, cloudy sunny etc), so the BMV on the Li bank was reading -3A one second and up to +3A the next. The LA BMV was reading up to 1A more out and 1 amp more as the current swung one way then the other. Now maybe the meters are wrong but I would guess not. The inverter is wired between the 2 banks maybe a 1/3 towards the LA's and 2/3 from the Li's. It seems to me therefore that the power is coming from the LA's when the draw exceeds the solar input and then goes back in just as quick when the solar inceases. Turn the solar and the draw off and both banks equalise in seconds. This was all done with the solar giving 13.6V.

I also isolated the Li bank to check the LA was truly full and yes, in seconds the solar current had dropped and only 0.1A going into the LA's. Repeated at solar up to 14.1v and got the same.

If you go back to my 'chemistry' post and consider what voltage is needed to get a site to do the 'charge' reaction (ie lead sulphate to lead/lead peroxide), it may be you have a graph that starts at 13.0V ish for the '100' sites and rises to 14.5V for the '50' sites. Not a clue what the shape of that curve/ine would look like. The key question for me is what voltage is needed to get the '80' (ie the 80% SoC sites) to move from lead sulphate to lead/lead peroxide). My guess is the first 20% of sites to react on discharge are going to be relatively easy to turn back based on what I have seen.

[WotEver]

54 minutes ago, Dr Bob said:

I'm sure you will!!

 

........but I followed MPs lead and got one of those £40 jobbies from fleabay and it seemed to do the business on 50mm cable. It's working today.

Yup, I use exactly the same tool. It appears to do a great job. Having read the article I certainly agree with his points in principle but as I don’t make a living out of wiring boats I wouldn’t consider spending the sort of money he does on tools. As he writes, find a crimp and tool combination that works and then stick to it. 

 

And for heaven’s sake don't solder the crimps. 

[cuthound]

11 minutes ago, Dr Bob said:

Cuthound

I have been struggling to find info on the web about charging/discharge when full and particularly references around steric hinderance/ depletion of ions around the active sites/diffusion. I wonder in your experience if you have seen anything that could give us a clue to the 'end of charge' data?

Obviously at the end of a charge cycle (where the batteries were down at 50% SoC at the start), the last 1% of charge is going to go in very slowly ......as per my long chemistry orientated post above. What though happens on a full battery, discharged to 99% SoC but then recharged?

I have been faffing round with my system today trying to get more oooomph out of the the MPPT and saw the following:

I have 2 separate BMVs on the Li and LA banks. There was a load of around 12A ....from the fridge compressor, the Inverter, numerous charging laptops and the TV. The sun was putting in circa 9A to 15A (cloudy, sunny, cloudy sunny etc), so the BMV on the Li bank was reading -3A one second and up to +3A the next. The LA BMV was reading up to 1A more out and 1 amp more as the current swung one way then the other. Now maybe the meters are wrong but I would guess not. The inverter is wired between the 2 banks maybe a 1/3 towards the LA's and 2/3 from the Li's. It seems to me therefore that the power is coming from the LA's when the draw exceeds the solar input and then goes back in just as quick when the solar inceases. Turn the solar and the draw off and both banks equalise in seconds. This was all done with the solar giving 13.6V.

I also isolated the Li bank to check the LA was truly full and yes, in seconds the solar current had dropped and only 0.1A going into the LA's. Repeated at solar up to 14.1v and got the same.

If you go back to my 'chemistry' post and consider what voltage is needed to get a site to do the 'charge' reaction (ie lead sulphate to lead/lead peroxide), it may be you have a graph that starts at 13.0V ish for the '100' sites and rises to 14.5V for the '50' sites. Not a clue what the shape of that curve/ine would look like. The key question for me is what voltage is needed to get the '80' (ie the 80% SoC sites) to move from lead sulphate to lead/lead peroxide). My guess is the first 20% of sites to react on discharge are going to be relatively easy to turn back based on what I have seen.

 

The lead acid batteries I have experience of were always kept on float charge, so that they were ready to supply load in the event of a mains failure.

 

With regard to end of charge info, temperature corrected specific gravity, tail current and resting voltage are the only indicators that I am aware of.

 

I was responsible for about 6,300 telephone exchanges. The batteries in the smaller more remote sites lasted about a third less time than those in towns. This was because the smaller sites have their electricity supply disputed more frequently, often for only a minute or so, because the HV breakers from the rural overhead supplies trip when the cables are struck by lightning and automatically re-close to restore supply. The urban sites were fed from underground electrical supplies, which weren't affected by lightning strikes. Hence the rural batteries would discharge from 100% SoC to maybe 98% SoC before recharging at float voltage.

 

The shorter life of the batteries in rural sites was due to the plates sulphating during these short discharges and not being fully "desulphated" by the float voltage.

 

The reason why you are finding it difficult to find definitive info on what exactly happens during charging & discharging at a molecular level, is because batteries are considered to be a "black art", and do not always behave in the manner science says they should!

 

[nicknorman]

49 minutes ago, Dr Bob said:

Cuthound

I have been struggling to find info on the web about charging/discharge when full and particularly references around steric hinderance/ depletion of ions around the active sites/diffusion. I wonder in your experience if you have seen anything that could give us a clue to the 'end of charge' data?

Obviously at the end of a charge cycle (where the batteries were down at 50% SoC at the start), the last 1% of charge is going to go in very slowly ......as per my long chemistry orientated post above. What though happens on a full battery, discharged to 99% SoC but then recharged?

I have been faffing round with my system today trying to get more oooomph out of the the MPPT and saw the following:

I have 2 separate BMVs on the Li and LA banks. There was a load of around 12A ....from the fridge compressor, the Inverter, numerous charging laptops and the TV. The sun was putting in circa 9A to 15A (cloudy, sunny, cloudy sunny etc), so the BMV on the Li bank was reading -3A one second and up to +3A the next. The LA BMV was reading up to 1A more out and 1 amp more as the current swung one way then the other. Now maybe the meters are wrong but I would guess not. The inverter is wired between the 2 banks maybe a 1/3 towards the LA's and 2/3 from the Li's. It seems to me therefore that the power is coming from the LA's when the draw exceeds the solar input and then goes back in just as quick when the solar inceases. Turn the solar and the draw off and both banks equalise in seconds. This was all done with the solar giving 13.6V.

I also isolated the Li bank to check the LA was truly full and yes, in seconds the solar current had dropped and only 0.1A going into the LA's. Repeated at solar up to 14.1v and got the same.

If you go back to my 'chemistry' post and consider what voltage is needed to get a site to do the 'charge' reaction (ie lead sulphate to lead/lead peroxide), it may be you have a graph that starts at 13.0V ish for the '100' sites and rises to 14.5V for the '50' sites. Not a clue what the shape of that curve/ine would look like. The key question for me is what voltage is needed to get the '80' (ie the 80% SoC sites) to move from lead sulphate to lead/lead peroxide). My guess is the first 20% of sites to react on discharge are going to be relatively easy to turn back based on what I have seen.

I think what you are saying is that if you start with a fully charged LA, take out 1% out fairly quickly and straight away recharge, that 1% goes in very quickly? If so I’d agree. This is because (in layman’s terms) the chemicals reacting (both ways) are on the surface of the plates and thus highly accessible.

 

However in your case if I understand correctly, you end up significantly discharging the LAs over many hours. In which case a prolonged charge at a voltage more than 13.1 - 13.8 is required to fully charge and ward off sulphation. Because of course, some of the chemical reaction has migrated deep into the plates and is thus relatively inaccessible.

[peterboat]

43 minutes ago, nicknorman said:

I think what you are saying is that if you start with a fully charged LA, take out 1% out fairly quickly and straight away recharge, that 1% goes in very quickly? If so I’d agree. This is because (in layman’s terms) the chemicals reacting (both ways) are on the surface of the plates and thus highly accessible.

 

However in your case if I understand correctly, you end up significantly discharging the LAs over many hours. In which case a prolonged charge at a voltage more than 13.1 - 13.8 is required to fully charge and ward off sulphation. Because of course, some of the chemical reaction has migrated deep into the plates and is thus relatively inaccessible.

He does his absorption is set at 14.2 volts and float at 13.6 volts, he does say that it goes into float early, mine today was fully charged when I came back to the boat and was showing 13.4 volts with nothing going in or out [toilet fan draw to small to measure?] when the fridge/freezer comes on it immediately shows 2.4 amps coming in, which stops when the fridge stops 

[WotEver]

1 hour ago, cuthound said:

The reason why you are finding it difficult to find definitive info on what exactly happens during charging & discharging at a molecular level, is because batteries are considered to be a "black art", and do not always behave in the manner science says they should!

To quote Gibbo...

”The start and end reactions [when charging] are known with intimate detail. The intermediaries not even close”

 

Other questions such as “How can a 12V LA battery ever have a voltage above 12.25?” Or “How can a 12V LA battery have a voltage as low as 2V?” can’t be answered either. 

 

 

Edited July 1, 2019 by WotEver
Added “12V”

[Dr Bob]

3 hours ago, nicknorman said:

I think what you are saying is that if you start with a fully charged LA, take out 1% out fairly quickly and straight away recharge, that 1% goes in very quickly? If so I’d agree. This is because (in layman’s terms) the chemicals reacting (both ways) are on the surface of the plates and thus highly accessible.

 

However in your case if I understand correctly, you end up significantly discharging the LAs over many hours. In which case a prolonged charge at a voltage more than 13.1 - 13.8 is required to fully charge and ward off sulphation. Because of course, some of the chemical reaction has migrated deep into the plates and is thus relatively inaccessible.

Yes, fully agree.

The unanswered question is what voltage is required half way between the fully charged and significantly discharged states where there is just a bit of steric hinderance/diffusion issues?

Cuthound's experience is very useful and helps, but are our recent battery design different?

Do peeps who keep their batteries on charge in marinas - with loads on - suffer sulphation with chargers that sit at 13.1V and then boost to 13.7V a few times a week (ie like my VIctron IP22 Bluesmart)?

3 hours ago, peterboat said:

He does his absorption is set at 14.2 volts and float at 13.6 volts, he does say that it goes into float early, mine today was fully charged when I came back to the boat and was showing 13.4 volts with nothing going in or out [toilet fan draw to small to measure?] when the fridge/freezer comes on it immediately shows 2.4 amps coming in, which stops when the fridge stops 

Peter, the mppt absorbtion is today set to 14.2V but I never see anything like that. Voltage increases from 13.2V up to 13.7V max and then goes into float, the same as yours.

[nicknorman]

Re marina based folk, our charger is set to  13.3v float, with the weekly boost of 14.5v. So we don’t get sulphation.

 

If and when we ever go Li, I will look into a smart alternator regulator of the home-made kind. One can get alternator regulator chips with a LIN interface quite cheaply (under £10). The LIN interface is normally used by a car’s ECU to send the  the desired regulating voltage (etc) to the alternator regulator and to receive back status information. One could fairly easily make up a micro controller (Arduino etc if you must!) to monitor battery voltage and charge current, and to lower the charge voltage to a safe float value once the Lis approach whatever maximum SoC one desires. Thus no need for any LAs.

[MtB]

1 hour ago, nicknorman said:

One could fairly easily make up a micro controller (Arduino etc if you must!) to monitor battery voltage and charge current, and to lower the charge voltage to a safe float value once the Lis approach whatever maximum SoC one desires. Thus no need for any LAs.

 

Provided you trust it to ALWAYS work and NEVER go wrong? 

 

 

[Dr Bob]

1 hour ago, nicknorman said:

Re marina based folk, our charger is set to  13.3v float, with the weekly boost of 14.5v. So we don’t get sulphation.

 

If and when we ever go Li, I will look into a smart alternator regulator of the home-made kind. One can get alternator regulator chips with a LIN interface quite cheaply (under £10). The LIN interface is normally used by a car’s ECU to send the  the desired regulating voltage (etc) to the alternator regulator and to receive back status information. One could fairly easily make up a micro controller (Arduino etc if you must!) to monitor battery voltage and charge current, and to lower the charge voltage to a safe float value once the Lis approach whatever maximum SoC one desires. Thus no need for any LAs.

Nick,

You are of course right that removing the dump LA is a good way to do it....as that's how all the EV's do it. The problem I see is that not only do you need to know your batteries, you also need a high level of electronics skills to build, integrate and programme such a system. A few of you out there have those skills ...and MP's system is built around a DIY BMS.... but there's not many of you. It would be good if the alternator controller can be put together easily.....and I'll be first in the queue for you to build me one.

A question for you though if you go that route. How do you see your charging regimes going? Are you going to do it Victron style (or EV car style)....ie charge at high voltage as fast as possible then let the system back off the alternator input when you approach the knee......or are you going to do it at canal boat pace and charge relatively slowly, ending the charge at 80% full to avoid all these problems of cell balancing. (What's cell balancing?) Even the slow charge rate cuts your engine running by a huge amount. For me the optimum is to bang as much power in via the alternator until I get to 13.7V and then stop....without burning out the alternator. Still a lot of discussion needed on that. Can you link your system to back off the alternator on high temperature and set that temperature?

For those out there without Nick's skills of advanced electronics, I would offer 3 reasons why having a hybrid LA/Li solution is more suited to most advanced muppets (like me).

1. As Mike says, what happens if the electronics go wrong? If you rely on your black box to back off the charge currents, it had better work. All the time. The hybrid system has far fewer 'what can go wrongs'.

2. If you were like me and had never crimped a 50mm cable in your life, the thought of taking all those LA's out of circuit and putting in new wiring etc was just a step too far. I couldnt even get near my LA's to check acid levels, let alone get in there to refit the whole thing. Just adding a set of Li's in parallel and wiring into the existing system so I knew if I did anything wrong, I could just turn a switch and be back using the existing LA's was the back up I needed. I really didnt have any experience of wiring up high capacity 12V batteries before I started.

3. One issue that we never seem to talk about is what if one cell goes wrong. They do on LA's. Here it is easy, just disconnect the bad cell and replace at your leisure. With my 3P, 4S system (480Ahrs @12V) I have 12 cells. If one goes bad it could be a major issue to take it out of circuit. The 'marine how to guy' raises this issue although he was more worried about how you do this in a lumpy water boat in a force 8. The Li battery pack is 'bolted' together as it is necessary to physically constrain them. It is not a simple job just to take one cell out. Being able to just turn a switch and go back to the LA's is a big advantage. Until I have proven to myself that Li's are the ultimate solution, I like the idea of LA's as a back up. Maybe by next year I will be happy to ditch them. The chance of an Li cell failing due to mechanical problems is far less likely on a nb compared to a lumpy water boat.......but I suppose it could happen.

[MtB]

24 minutes ago, Dr Bob said:

With my 3P, 4S system (480Ahrs @12V) I have 12 cells. If one goes bad it could be a major issue to take it out of circuit. The 'marine how to guy' raises this issue although he was more worried about how you do this in a lumpy water boat in a force 8.

 

A related issue is what if a cell fails on the 'multi-cell' type of Li battery which comprise hundreds of little cells arranged in series/parallel grids to make a 12v battery? E.G. the Valence, Relion, (and possibly Victron?) brands? Maybe the whole battery is goosed but I think Peterboat says not.

 

Maybe they just go open circuit of failure, but does anyone know what exactly happens when a Li cell fails? ISTR they quite like overheating and possibly catching fire in which case I guess they just go open circuit. 

 

[Dr Bob]

It doesn't look like they are easy to set on fire according to the video on the marine how to link.

Ours have been sitting at 20 Deg C for the last few days.

Max was 22C last weekend.

Edited July 2, 2019 by Dr Bob

[MtB]

5 minutes ago, Dr Bob said:

It doesn't look like they are easy to set on fire according to the video on the marine how to link.

Ours have been sitting at 20 Deg C for the last few days.

Max was 22C last weekend.

 

The rapid rise in temperature and catching alight occurs on reaching 101%+ SoC, reputedly.

 

Could you trying this please and let the board know what happens? 

 

Much obliged....

 

 

[Dr Bob]

5 minutes ago, Mike the Boilerman said:

 

The rapid rise in temperature and catching alight occurs on reaching 101%+ SoC, reputedly.

 

Could you trying this please and let the board know what happens? 

 

Much obliged....

 

 

Nah, can't do. My alternator and mppt turn to float at 80% so never get near 100%.

[MtB]

1 minute ago, Dr Bob said:

Nah, can't do. My alternator and mppt turn to float at 80% so never get near 100%.

 

There are ways around this non-problem, you muppet!!

 

 

 

[Dr Bob]

2 minutes ago, Mike the Boilerman said:

 

There are ways around this non-problem, you muppet!!

 

 

 

Oi!!!!

I'm an advanced Muppet.

[peterboat]

1 hour ago, Mike the Boilerman said:

 

A related issue is what if a cell fails on the 'multi-cell' type of Li battery which comprise hundreds of little cells arranged in series/parallel grids to make a 12v battery? E.G. the Valence, Relion, (and possibly Victron?) brands? Maybe the whole battery is goosed but I think Peterboat says not.

 

Maybe they just go open circuit of failure, but does anyone know what exactly happens when a Li cell fails? ISTR they quite like overheating and possibly catching fire in which case I guess they just go open circuit. 

 

LifePo4s dont catch fire fingers crossed,From my point of view and James who has taken apart these batteries he hasnt seen failed cells in normal use.

However one of his customers cooked a pile of them! and he really cooked them they were beyond repair, when James stripped one some cells were still ok, I cant remember what the guy did but it was on a house based system and he put some parameters in wrong seems to ring a bell, but I could be wrong, anyway they didnt catch fire

30 minutes ago, Dr Bob said:

Nah, can't do. My alternator and mppt turn to float at 80% so never get near 100%.

 

28 minutes ago, Mike the Boilerman said:

 

There are ways around this non-problem, you muppet!!

 

 

 

So basically all your reserve systems arnt needed as the alternator does it anyway? ???

[nicknorman]

5 hours ago, Dr Bob said:

Nick,

You are of course right that removing the dump LA is a good way to do it....as that's how all the EV's do it. The problem I see is that not only do you need to know your batteries, you also need a high level of electronics skills to build, integrate and programme such a system. A few of you out there have those skills ...and MP's system is built around a DIY BMS.... but there's not many of you. It would be good if the alternator controller can be put together easily.....and I'll be first in the queue for you to build me one.

A question for you though if you go that route. How do you see your charging regimes going? Are you going to do it Victron style (or EV car style)....ie charge at high voltage as fast as possible then let the system back off the alternator input when you approach the knee......or are you going to do it at canal boat pace and charge relatively slowly, ending the charge at 80% full to avoid all these problems of cell balancing. (What's cell balancing?) Even the slow charge rate cuts your engine running by a huge amount. For me the optimum is to bang as much power in via the alternator until I get to 13.7V and then stop....without burning out the alternator. Still a lot of discussion needed on that. Can you link your system to back off the alternator on high temperature and set that temperature?

For those out there without Nick's skills of advanced electronics, I would offer 3 reasons why having a hybrid LA/Li solution is more suited to most advanced muppets (like me).

1. As Mike says, what happens if the electronics go wrong? If you rely on your black box to back off the charge currents, it had better work. All the time. The hybrid system has far fewer 'what can go wrongs'.

2. If you were like me and had never crimped a 50mm cable in your life, the thought of taking all those LA's out of circuit and putting in new wiring etc was just a step too far. I couldnt even get near my LA's to check acid levels, let alone get in there to refit the whole thing. Just adding a set of Li's in parallel and wiring into the existing system so I knew if I did anything wrong, I could just turn a switch and be back using the existing LA's was the back up I needed. I really didnt have any experience of wiring up high capacity 12V batteries before I started.

3. One issue that we never seem to talk about is what if one cell goes wrong. They do on LA's. Here it is easy, just disconnect the bad cell and replace at your leisure. With my 3P, 4S system (480Ahrs @12V) I have 12 cells. If one goes bad it could be a major issue to take it out of circuit. The 'marine how to guy' raises this issue although he was more worried about how you do this in a lumpy water boat in a force 8. The Li battery pack is 'bolted' together as it is necessary to physically constrain them. It is not a simple job just to take one cell out. Being able to just turn a switch and go back to the LA's is a big advantage. Until I have proven to myself that Li's are the ultimate solution, I like the idea of LA's as a back up. Maybe by next year I will be happy to ditch them. The chance of an Li cell failing due to mechanical problems is far less likely on a nb compared to a lumpy water boat.......but I suppose it could happen.

Obviously once you can control the charge voltage and the algorithm has access to battery voltage (including individual cell voltage) and charge/discharge current you can decide how you want to do it. I would imagine having a switch with 3 settings: 1). Charge fully. 2) Charge to 80%, 3 Charge to 50%. 

 

1) For use when it was expected to be moored up for a couple of days, 2) For everyday use and 3) for when leaving the boat in the marina etc.

 

As to your point about “what if it went wrong? Then that is what the high and low “emergency” disconnects are for. What happens when you alternator or solar regulator develops a fault? Same thing.

 

There can be a feeling that something designed and built by someone you know must be less reliable than something you buy in a shop, but that is not necessarily rational.

Edited July 2, 2019 by nicknorman

[MtB]

5 minutes ago, nicknorman said:

As to your point about “what if it went wrong? Then that is what the high and low “emergency” disconnects are for. What happens when you alternator or solar regulator develops a fault? Same thing.

 

 

But then you are back to wrecking the alternator, avoidance of which was the whole point of keeping a LA batt in parallel.

 

:headbang:

 

 

[nicknorman]

11 minutes ago, Mike the Boilerman said:

 

But then you are back to wrecking the alternator, avoidance of which was the whole point of keeping a LA batt in parallel.

 

:headbang:

 

 

No, at that point the alternator is already faulty (in Dr Bob’s case). In my case if my equipment has failed it serves me right! Anyway, it would just be the diode pack to replace, not a big deal.

 

in case you’re not getting the point, the emergency high disconnect would only operate after the failure of some other equipment, to protect the batteries. If necessary at the expense of the alternator diodes, which are a lot cheaper than a Li battery pack!  

Edited July 2, 2019 by nicknorman

[nicknorman]

Actually, on that subject I’m wondering if one could have a high power zener diode(s) that would briefly dissipate the excess  transient power from the alternator following an emergency disconnect.

[Dr Bob]

58 minutes ago, nicknorman said:

 In my case if my equipment has failed it serves me right! Anyway, it would just be the diode pack to replace, not a big deal.

 

 

In your system, you are using a newly designed electronic circuit to back power off charge sources. That can go wrong. You then have an emergency disconnect, but what is it disconnecting? If you disconnect the charge sources then you can fry the diode pack etc.

In the 'dump battery' system, you do not have the newly designed electronic pack to go wrong, as the charge sources are shutting down themsleves automatically, and if you do get to the emergency disconnect position then you protect all charge sources via the dump load.

In the simple world of canal boats where fast charging is not really needed, why complicate things. If you want to push the alternator hard then yes, some better source of alternator control is required but that is beyond the skills of most of us........but even moderate alternator charging reduces engine hours significantly. You really dont need to go over 80% charged and it sounds like battery life is enhanced by staying between 20 and 80%.

 

[nicknorman]

13 minutes ago, Dr Bob said:

In your system, you are using a newly designed electronic circuit to back power off charge sources. That can go wrong. You then have an emergency disconnect, but what is it disconnecting? If you disconnect the charge sources then you can fry the diode pack etc.

In the 'dump battery' system, you do not have the newly designed electronic pack to go wrong, as the charge sources are shutting down themsleves automatically, and if you do get to the emergency disconnect position then you protect all charge sources via the dump load.

In the simple world of canal boats where fast charging is not really needed, why complicate things. If you want to push the alternator hard then yes, some better source of alternator control is required but that is beyond the skills of most of us........but even moderate alternator charging reduces engine hours significantly. You really dont need to go over 80% charged and it sounds like battery life is enhanced by staying between 20 and 80%.

 

The “low tech is best” argument was presented each time technical progress was in the offing. From the invention of the weaving machine onwards. Why have light bulbs, especially LED ones with electronics inside, when a candle is perfectly capable of providing light? Far less to go wrong.

 

Anyway I can accept that the compromises you have chosen work well for you and I am not criticising you for it. But as a technical solution I don’t feel it is optimised, and optimising it wouldn’t be that difficult (for me).

 

Just on the 80% charged thing which is bandied about a lot, are there any actual figures for this? I’m thinking that whilst one might want to routinely charge to 80%, on occasion (when planning to moor up for a few days) it would be useful to be able to get to 100%. I can’t imagine that this would have anything but the very slightest effect on battery life.

 

Oh and for us with the Iskra 175A alternator, I wouldn’t like that to have unfettered access to Li batteries - overheating issues plus load on engine and drive belt when near idle.

Edited July 2, 2019 by nicknorman