magnetman

February 11

The Victron 50A B2B does look good to be fair as it seems to allow user settings for charge profile and current.

Quite attractive. Easy enough to have an alarm for alternator case temperature.

February 11

17 minutes ago, cheesegas said:

This would make it possible to severely damage the battery by trying to start the engine when the battery is discharged and the BMS is about to do a discharge disconnect. It’s also the most likely time that someone’s going to start the engine - leisure battery low, need to run engine to charge batteries.

The timer would work for a lead battery but not lithium, and it would still be a bad solution. Say you’ve worked out that you need to put in 100ah with your 100a alternator, which works out to 1hr. Then, you go inside, switch the inverter on, charge your laptop and put on the washing machine…this all takes say 20ah so you end up with only 80ah in the battery. And if you were to start the engine in summer at 3pm to cruise, you’d need to check that the alternator is off or else you’d be holding the lithium battery at full charge which isn’t good for it.

A better solution which is what myself and a couple others do on here is to use the relay output on a Victron BMV to disable the alternator at 100%. This is better but not great - without a float voltage, if you were to draw high power with the batteries full and alt off, it goes into a loop of short charge, short discharge and repeat.

LTO is an interesting option. I have been experimenting with 6S LTO modules and they don't seem to be bothered about much. I've had one of them down to about 4v (no BMS) and it charged up normally cells are still within 3mV of each other.

Also the top voltage is 16.8v. Mid range maintenance voltage between 14 and 15v.

Not done any alternator testing its just been solar so far but I will be doing some experiments.

Also excellent for engine starting I use a 40Ah module charged to 15.2v to start the Perkins P4 its does it happily.

They are generally rather expensive batteries but if one were to have a multi cycle charge discharge regime the battery banks can be smaller.

I have marked the module which went right down (lights left on) and interesting to see if it suffered at all. It appears not.

LTO have very high cycle life and also huge C rating. 10C is easy.

i took apart a Suzuki Swift mild hybrid battery. It has a 3Ah 5S LTO battery which is nominal 12v 3Ah. Tiny. The battery has a 150A fuse despite being so small. This is used in the car to add power while moving from a standstill then recharged. I believe the in/out rate is probably something like 20C in use which would mean it was supplying nearly 1HP for a short time.

It might be more. The 150A fuse was interesting.

Yes 6S is a bit high for normal 12v loads but easy to put a buck converter on lights and pumps circuit. Inverters cut out at over 15v which is about 85% charged so a happy battery.

LTO ocv soc graph . So roughly 40-90% is 2.2-2.5v which for a 6S would be 13.2-15v. Not too terrible. Space above for safety.

February 11

24 minutes ago, cheesegas said:

The issue with a lithium starter battery is that most BMSs are rated for 100-200 amps, whereas the starter motor can draw 300+ amps. You'd need either a contactor based BMS, or massive FETs to pass the current. It's fairly common in the cafe racer motorcycle scene as their starter motors draw a lot less current.

Most alternators we see on boats at the moment are based on car designs, which have no need to adapt to lithium batteries - it's only marine-specific models like Balmars etc which have lithium compatible regulators, and those are expensive external ones. You'd usually see Balmars on dual engined cruisers with a big house battery bank. I think the market is very small for an alternator with an internal lithium regulator so it'll be many years before one comes out.

There are however some large non-automotive alternators aimed at the modified car market with massive audio systems - they're built very well to withstand heavy loads at a low engine speed so it would be good to see them adapted for marine use. Some even have remote rectifiers and regulators to keep the heat in the case down. Again though, not cheap as the market is pretty small!

It would be very easy to have two negative terminals. One attached to the BMS for loads which may discharge the battery while unattended and the other one for heavy discharge such as starter motor and connected directly to the terminals.

I have a battery like this.40A BMS or connect direct. It was home made by someone who is an EV industry professional. Seems an interesting approach I think.

5 minutes ago, Alan de Enfield said:

Why not ?

If a small market wants (needs) something they have to pay the design, set up and low volume production costs amortised over a small number of customers.

Yes that is basic economics but if lithium batteries become universal then it seems demand would go up.

Is it not plausible just to have say a 65A alternator which will charge a LFP battery and switch itself off after a certain amount of time? If one knew how many Ah one wanted would it not make sense to put a timer onto the regulator.

February 11

I wonder how many others use lithium batteries for starting the engines.

Alternators do need to adapt to lithium batteries at some stage and it should not mean a regulator costing hundreds of pounds.

February 10

Is there any reason why the MPPT would object to a voltage which was not jumping around? Presumably with solar panels with no shade and a sunny day this would be quite a common outcome.

February 10

I have endless room in my head for batteries.

I suppose people do have space constraints which is why the drop in thing exists in the first place.

One day these problems will be solved when infernal combustion engines are banned.

1 minute ago, Alan de Enfield said:

MPPT fed by 24v alternator ?

See above

33 minutes ago, magnetman said:

Maybe A 24v alternator, 2 LA batteries to make a 24v bank and the MPPT repurposed for winter to charge the LFP batteries via alternator-LA battery-MPPT.

In summer the solar does the job and the other alternator is still 12 volts.

33 minutes ago, IanD said:

I'm not sure using an MPPT controller as a B2B is a good idea, the nature of the beast is different -- an MPPT controller is expecting to have solar panels on the input, and to adapt the input current and voltage to maximise output power from the panels. Not sure how this will react when the input side is an LA battery being charged by an alternator, maybe it'll just provide maximum output current all the time...

Its an interesting question.

i wonder if it is good for the makers (lets say Victron) to keep these two products separate in order to shift more blue items in flash boxes. They might be electronically very similar. I don't know but have difficulty working out why the output from an alternator through a battery would be so different from a solar panel.

February 10

24v Alternator 55A is £150 (prestolite lucas a127)

Couple of cheap lead acid batteries £150.

I already have a 50A MPPT which is surplus in winter. In summer the vast majority of the electric is dealt with by solar panels.

50A b2b would be £300.

It costs the same. I think the 24v alternator might be better for thermal management as there are fewer amps coming out of it.

Which would mean one could eke out more power with less risk of overheating.

I expect a good alternator controller solves these problems but how much do they cost?

February 10

Just now, IanD said:

You seem to be trying to make a silk purse out of a sow's ear -- if you're going to start replacing alternators and adding a B2B, it's probably cheaper (and better!) to add an alternator regulator like the Wakespeed which can also sense alternator temperature and cut back current at low rpm and lots of other things.

If you're starting from scratch then 24V makes a lot of sense, but changing to this adds even more cost (lights, pumps etc...).

The Boat domestic system is run by a 12 (13) volt LFP bank.

The only 24 volt parts would be the alternator and the small Lead battery bank. This would be routed via the MPPT (might not work) to the LFP battery bank which would be 12/13v.

I was proposing repurposing a high current MPPT for winter when their is naff all solar.

Making silk purses from sows ears seems quite a wise move to me in a number of different ways.

February 10

Cheap and cheerful alternators?

Also did you check the operating temperature range of the alternators?

February 10

8 minutes ago, IanD said:

If you're worried about that case, B2Bs like the Victron have programmable current limits (phone app via Bluetooth, dead easy to adjust).

But the engine needs a 12V start battery, and has a 12V alternator...

The system I was referring to has dual alternators. The starter would be 12v.

February 10

One of those cheap single induction hobs would be good because they have power settings from 300w to 2kw selectable.

1 minute ago, Tony1 said:

I wish I could give you a proper answer!

What I did was to cut various lengths of cable, and did a bit of trial and error till I had a set of different cable lengths that would limit the output current from the alternators 30 amps, 35 amps, 40 amps, and 45 amps, and I think 50 amps.

I wired those in and ran the engine at idle, and used one of those thermometers that you point at things to measure the alternator temp (measuring the hottest spot, as the temp does vary around the casing).

In my case I found that if the alternator was putting out more than 35 amps at idle it would get hotter than 100 degrees, so I bought the B2Bs with that limitation in mind.

I did also measure how the alternators behaved at 1300 rpm, and found that I could suck more current from them at that speed, but you can only guarantee doing that rpm when sat on a mooring doing a 'static' charge.

Maybe more ventilation is needed for these alternators.

February 10

6 minutes ago, Col_T said:

Genuine question - how would one do that test??

The only way I can think of is to run down the LA bank to 20-30% of capacity and then start recharging at tick over. Any better ideas?

If you have a big inverter and heavy load like an immersion heater which the inverter can run you could test the alternator that way. IR thermometer to hand.

February 10

Maybe A 24v alternator, 2 LA batteries to make a 24v bank and the MPPT repurposed for winter to charge the LFP batteries via alternator-LA battery-MPPT.

In summer the solar does the job and the other alternator is still 12 volts.

February 10

30 amps seems quite a low charge rate.

Is it also the point at which Victron B2B hardware gets a lot more expensive?

I do idly wonder if my 50A Victron MPPT for the solar panels could be repurposed and used as a B2B in winter if I wanted to charge batteries using the main engine.

Sun is predictable due to seasonal changes so there would be a certain point where whipping out the 50A and replacing with a 20A MPPT (observing input voltage) could make some sense.

Don't know if it would work and I think perhaps there is a problem with voltage needing to be higher than the battery. Maybe Victron have already thought of that and designed it out of their products.

Been here before I seem to recall.

24v alternator is the thing.

February 10

It would be fun if a court had to decide what 'drop in' means.

They might come to the conclusion it just means two items the same shape.

'Drop in replacement'

Not 'drop in alternative'.

February 10

2 fires can be a solution for this.

Lots of narrow Boats have two fires.

February 10

I seem to recall there are the remains of a miniature railway there for the gasworks.

February 9

Have they sold that many ?

Warranty claims seem to not include burnt alternators.

Also, as I have been saying all along, these things are great for solar panel use.

I'm not remotely anti lithium batteries but I do question the drop in status. I guess a lot of these are sold to motorhome owners who are probably just a wee bit conservative and tie up their vans in nice safe camp sites with 6A mains supplies so they can charge their batteries up.

February 9

I know what it is supposed to mean but in reality most people can't 'drop' one of these in to replace an existing Lead battery. It won't work.

Well I suppose it is possible/probable that more people have shore power than don't but in that situation one would not be looking to maximise battery efficiency anyway.

Presumably if it all gets regulated at some stage then terms like 'drop in' won't cut the mustard.

They might even turn into 'drop out' when the arrangement is rejected on safety grounds.

February 9

Yes but what does 'drop in' actually mean?

It appears to be a meaningless term when it comes to batteries. A marketing term made up by someone at some stage.

Was it Mr Sterling ?

February 9

13 minutes ago, MtB said:

My own view is until someone designs a BMS to go inside a 'drop-in' that addresses 1) and 2)*, calling them drop-ins is misleading and will eventually attract the interest of Trading Standards. Or should anyway.

Drop In is definitely an interesting but of terminology. Obviously this is referring to the size of the battery blocks as provided and it is convenient to supply LFP battery blocks which have the same 'form factor' as normal '110 leisure' type Lead batteries.

But...

If one were to take the term 'drop in' literally it implies that the battery blocks may be released from a height. In some cases this could be quite handy as getting down into the engine 'ole is arduous.

I think the suppliers probably ought to have specs for how high one can drop the battery in from. Is it one metre or two?

Perhaps 'drop in' is referring to a casual medical facility.

February 9

Just now, IanD said:

But only when the boat is moving, you couldn't use it for charging when moored. Unless the run the prop while moored, like you're not supposed to... 😉

I have never run a main engine while moored in 30 yars of living on Boats. Always had a generator for charging when not moving.

I disagree with using the main engine for this but when the Boat is moving taking advantage of the power available seems wise.

More than half of that 30 yars was without shorepower although I admit one of the Boats has had the umbillical for a while. I hate it.

and from beginning of April to coincide with the anniversary both Boats will again be off grid and free to roam.

Yaay!

February 9

59 minutes ago, MtB said:

One of those £3,500 Travel Powers you mean?

Oh maybe not then. Perhaps an inverter running off the AGM bank charged by the 175A Iskra alrernator powering a lithium specific charger.

At the end of the day the issue is with inappropriate rotating electrics so perhaps this is where things need to change.

I sometimes wonder about a permanent magnet alternator with a magnetic clutch.

The best one would be running from the propshaft then you could pull some real power off it.

February 9

Maybe a job for a travelpower instead of the second alternator and a mains powered lithium battery charger.

The standard 12v alternator seems to be the weak link.

If it was done via a travelpower then the main domestic battery could be 48v with converters for small 12v consumers. I wouldn't be surprised if a lot of consumers on modern craft are mains powered via inverters.

48v is nice.

February 9

1 hour ago, nicknorman said:

Very true. For example in the certification of airliners carrying hundreds of passengers at 35,000’, the certification requirement is not that the wings can never unexpectedly fall off

Something similar happens with ships

53 minutes ago, IanD said:

If any of the drop-in LFP suppliers do start supplying batteries where they're confident enough in their BMS/protection to allow them to be used in parallel with LA then this could all change and hybrid systems can be allowed and certified, so long as it's checked that the LFP batteries are "parallel LA approved" by the manufacturer an inspector can sign this off.

The Lifebatteries geyser is already doing this. The webshite looks pretty amateur so I don't know if it is a genuine player but he thinks it works.

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