Lithium Batteries installation

[IanD]

15 minutes ago, Tony1 said:

 

I can say the B2B units get very hot in use, so there's certainly a lot of heat energy wasted, although I've not measured the current going into them, only that coming out- so I cant say for sure. The previous Sterling unit I used seemed to waster at least 15% of the input current as heat.

 

My starter and domestic alternators are rated at 70 amps and 100 amps respectively, but they cant keep that up without overheating.

To keep their temp below 100 degrees, I can't take more than about 30 and 35 amps from them respectively, so the victron units are a pretty good match for their safe current output level.  So I get about 60amps into the lithiums in total.

 

I did also install a third smaller B2B, with 18 amps output. I sometimes use the third B2B when I'm doing a static charge, because when doing that I can keep the revs up at 1300 rpm, which helps cool the alternators.  So flat out I can get almost 80 amps of charge, but I don't always use the third B2B.

Mine is a canaline 38 and it has narrow V belts- not poly V-  and I feel like I might be straining the belts and the crank more I should when I do a 90 minute battery charge at the full 80 amps. So I tend to stick to using two B2Bs for most of the time. 

 

I cant remember the max charge of the lithiums, but its certainly much more than I ever do to them! Even when cruising in high summer, with maybe a further 90 amps of solar coming in for long periods of the day, the charge current is only around 150 amps max. 

Tbh in those high solar months, I tend to leave the B2Bs switched off for most of the time, even when the engine is running, since the solar does everything I need and more.

(Speaking of which, I've had 1100 Wh of solar today, so I feel like we may be starting to get into the period where it gets useful again)

 

 

Are you planning to keep the LA domestic battery or just have LA starter + domestic LFP + B2B? In which case you'd connect both alternators in parallel to the LA (if this works...) and have a bigger B2B for charging the LFP

 

35A continuous out of your 100A domestic alternator sounds pretty poor, most people seem to be OK with maybe 50% current even when charging LFP banks. I'd have thought something like a Victron Orion XS 12V-12V 50A battery charger would do the job nicely -- programmable currents and voltages, maximum efficiency is 98.5%, I expect full-load is less than this but should still be well above 95%. About £300 though, and not out for a couple of months... 😉

 

https://www.victronenergy.com/dc-dc-converters/orion-xs-12-12-50a-dc-dc-battery-charger

https://offgridpower.solutions/shop/victron-energy-smart-buckboost-dc-dc-charger-non-isolated-50a

Edited February 10 by IanD

[Tony1]

1 minute ago, cheesegas said:

They exist already, there's just not much market for them so they're expensive. It's called an alternator regulator and there's not many models to choose from, Arco Zeus, Wakespeed WS500, Mastervolt Alpha, Balmar 618.

 

The decent ones keep an eye on the alternator temperature and RPM, and vary the field current to keep the alternator at a safe temperature and to alter the output voltage by dropping to float etc. Advanced ones like the Wakespeed communicate with a CANbus system and will reduce charging current if something happens like one of three battery BMses goes offline, to avoid exceeding the max charge current of the batteries.

 

Those are the ideal solutions, no doubt about that, but so expensive...

My thinking was that the market could do with having a unit that could be cabled in by an average boater (like an MPPT or a B2B can). 

As magnetman says, the MPPTs seem to be tantalisingly close to being able to do the job...

 

 

[IanD]

2 minutes ago, Tony1 said:

 

Those are the ideal solutions, no doubt about that, but so expensive...

My thinking was that the market could do with having a unit that could be cabled in by an average boater (like an MPPT or a B2B can). 

As magnetman says, the MPPTs seem to be tantalisingly close to being able to do the job...

 

 

MPPTs need the input voltage to be several volts higher than the output, so you can't use then for connecting alternator + 12V LA to 12V LFP.

 

B2Bs do the job required but decent higher-current ones aren't cheap, the 50A Victron one (looks perfect for the job) is about £300... 😞

[David Mack]

9 minutes ago, IanD said:

Are you planning to keep the LA domestic battery or just have LA starter + domestic LFP + B2B? In which case you'd connect both alternators in parallel to the LA (if this works...) and have a bigger B2B for charging the LFP

And if you have solar do you connect it to the LA starter or LFP domestic? If the former then you can't get the combined output of alternator and solar into the LFP due to B2B capacity limit, but the latter doesn't keep the starter battery topped up when the boat is not in use.

[Tony1]

24 minutes ago, IanD said:

 

Are you planning to keep the LA domestic battery or just have LA starter + domestic LFP + B2B? In which case you'd connect both alternators in parallel to the LA (if this works...) and have a bigger B2B for charging the LFP

 

35A continuous out of your 100A domestic alternator sounds pretty poor, most people seem to be OK with maybe 50% current even when charging LFP banks. I'd have thought something like a Victron Orion XS 12V-12V 50A battery charger would do the job nicely -- programmable currents and voltages, maximum efficiency is 98.5%, I expect full-load is less than this but should still be well above 95%. About £300 though, and not out for a couple of months... 😉

 

https://www.victronenergy.com/dc-dc-converters/orion-xs-12-12-50a-dc-dc-battery-charger

https://offgridpower.solutions/shop/victron-energy-smart-buckboost-dc-dc-charger-non-isolated-50a

 

I currently use two LA batteries- one for each alternator. So each LA then 'feeds' into its own B2B unit. 

 

I did try running both alternators through a single LA battery to start with, but one of them runs at about 0.5v higher than the other. What seems to happen is that when they run in parallel to a single LA, the alternator running at the lower voltage fails to operate fully, and only puts out maybe 10-15 amps at best. But when running into separate LAs, they both run properly.

 

I originally tried pulling more current from the domestic alternator but it just got too hot. Revving the engine to 1300 helps to cool the alternators, and I can squeeze out maybe 90 amps safely at 1300 rpm from both alternators, but it feels like I'm asking a lot of the crank and the belts doing that.

So a 50 amp unit wouldn't really help me.

 

I do think that before buying anything, people considering B2Bs need to test out their alternator(s) capability in the worst case scenario for alternator temp (i.e. sucking max current out when running at idle).

If you buy a 50 amp B2B and your alternator can only put out 35 amps like mine, you've wasted your money, because you cant use the 50 amp B2B at all (although some can be set to run at half power, e.g. the Sterlings). 

 

 

8 minutes ago, David Mack said:

And if you have solar do you connect it to the LA starter or LFP domestic? If the former then you can't get the combined output of alternator and solar into the LFP due to B2B capacity limit, but the latter doesn't keep the starter battery topped up when the boat is not in use.

 

In my case the panels are wired directly to the lithiums and not via the LAs, partly for the reason you suggest. 

This does mean that if I only cruise every 4 or 5 days in summer, my LAs are not getting a daily charge because the engine isn't running for several days, but they've been running with that very poor charging regime for well over 2 years, and so far they've lasted fairly well. 

 

Edited February 10 by Tony1

[IanD]

7 minutes ago, Tony1 said:

 

I currently use two LA batteries- one for each alternator. So each LA then 'feeds' into its own B2B unit. 

 

I did try running both alternators through a single LA battery to start with, but one of them runs at about 0.5v higher than the other. What seems to happen is that when they run in parallel to a single LA, the alternator running at the lower voltage fails to operate fully, and only puts out maybe 10-15 amps at best. But when running into separate LAs, they both run properly.

 

I originally tried pulling more current from the domestic alternator but it just got too hot. Revving the engine to 1300 helps to cool the alternators, and I can squeeze out maybe 90 amps safely at 1300 rpm from both alternators, but it feels like I'm asking a lot of the crank and the belts doing that.

So a 50 amp unit wouldn't really help me.

 

I do think that before buying anything, people considering B2Bs need to test out their alternator(s) capability in the worst case scenario for alternator temp (i.e. sucking max current out when running at idle).

Because if you buy a 50 amp B2B and your alternator can only put out 35 amps like mine, you've wasted your money, because cant use the 50 amp B2B at all (although some can be set to run at half power, e.g. the Sterlings). 

 

 

Completely agree -- but then it's usually recommended to run above idle (>1200rpm) for battery charging, it uses less fuel and charges the batteries faster and the alternators don't get so hot, they really don't like their cooling fans turning slowly while putting lots of current out. Some people have also added cooling fans and ducting to blow cold air from outside the engine bay into the alternators to stop them overheating.

Edited February 10 by IanD

[Tony1]

4 minutes ago, IanD said:

 

Completely agree -- but then it's usually recommended to run above idle for battery charging, it uses less fuel and charges the batteries faster and the alternators don't get so hot, they really don't like their cooling fans turning slowly while putting lots of current out. Some people have also added cooling fans and ducting to blow cold air from outside the engine bay into the alternators to stop them overheating.

 

I follow that principle when engine charging- I usually charge at about 1100 rpm or bit more, after a couple of mins at idle to let things warm a little bit. 

The scenario I have in mind is when cruising and you're going past a long line of boats at tickover, or going trough a lock, say- those times when you're engine is at idle for periods of time. Thats the sort of 'worst case' I had in mind when selecting the correct size of B2B to suit your alternator. 

 

Edited February 10 by Tony1

[Col_T]

7 minutes ago, Tony1 said:

people considering B2Bs need to test out their alternator(s) capability in the worst case scenario for alternator temp (i.e. sucking max current out when running at idle).

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?

[magnetman]

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. 

 

 

Edited February 10 by magnetman

[IanD]

8 minutes ago, Tony1 said:

 

I follow that principle when engine charging- I usually charge at about 1100 rpm or bit more, after a couple of mins at idle to let things warm a little bit. 

The scenario I have in mind is when cruising and you're going past a long line of boats at tickover, or going trough a lock, say- those times when you're engine is at idle for periods of time. Thats the sort of 'worst case' I had in mind when selecting the correct size of B2B to suit your alternator. 

 

 

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

 

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

 

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

 

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...

Edited February 10 by IanD

[magnetman]

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. 

[Tony1]

15 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?

 

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 to 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.

Edited February 10 by Tony1

[magnetman]

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. 

[IanD]

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.

So you could set a lower limit for the general case, and turn it up when charging at 1300rpm when moored... 🙂

[Tony1]

4 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...

 

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...

 

My 30 amp victron unit has bluetooth control but it doesnt have current adjustment- its a couple years old so maybe the newer models do that?

 

That new 50 amp model would be absolutely ideal for a new install tbh - you can up the charging current when you do a static charge at higher revs, and lower it for normal cruising. You'd want to be very strict about remembering to change the setting back in each case though, or you'll overheat the alternator. I think £300 is pretty decent for a unit like that, and I'd deffo get that if I didnt already have mine. 

 

[magnetman]

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. 

 

 

[Tony1]

3 minutes ago, magnetman said:

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

 

Maybe more ventilation is needed for these alternators. 

 

I did those tests on a cruiser stern with the engine board off, on a freezing January day with a strong breeze swirling all around both me and the engine.

The ventilation was rather better than I really wanted at the time! 

 

[magnetman]

Cheap and cheerful alternators? 

 

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

 

 

 

[IanD]

1 minute ago, magnetman said:

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

 

 

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...).

[Tony1]

1 minute ago, magnetman said:

Cheap and cheerful alternators? 

 

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

 

 

 

 

Tbh I didnt do that, but I did measure the alternators operating temps when only charging LA batteries (at various current levels), and I dont think they ever got above 55 to 60 degrees in that more normal usage.

So I reckoned 100 degrees was as high as I wanted to go, based on a normal temp of less than 60. 

 

I'm afraid the quality and capability of alternators in lower-end engines is not really ideal for lithium battery charging. Thats why I tread rather carefully when I'm trying to squeeze more current out of them! 

 

[magnetman]

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. 

[IanD]

4 minutes ago, magnetman said:

 

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. 

 

 

But what's the point? Do you have 12V (starter) *and* 24V (domestic) LA batteries as well as a 12V domestic LFP? Do you have 12V and 24V alternators?

 

Why do all this when a B2B (or alternator regulator) is simpler, probably cheaper, and less to change?

 

The simplest (and cheapest?) solution is probably to keep the 12V starter battery and alternator, swap the 12V domestic LA bank for LFP, and add an alternator regulator to the 12V domestic alternator to charge the LFP bank. Alternatively, keep the existing alternators and LA batteries and add a B2B and LFP for domestic power.

Edited February 10 by IanD

[magnetman]

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? 

Edited February 10 by magnetman
fewer not less

[IanD]

1 minute ago, magnetman said:

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. 

 

50A b2b would be £300. 

 

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

 

 

If you've got the space for 4 sets of batteries (12V starter, 2x12V LA, 12V LFP) and think the (surplus?) "free" MPPT will work as a B2B (only in winter?), go ahead, it's your boat.

 

For most people it doesn't seem like a good solution though... 😉

[Alan de Enfield]

56 minutes ago, IanD said:

MPPTs need the input voltage to be several volts higher than the output, so you can't use then for connecting alternator + 12V LA to 12V LFP.

 

MPPT fed by 24v alternator ?