Starting changing to Lithium again, Alternator question

[Tombola]

Im starting to switch over to Lithium, b2b, etc on my new Rapido 8094df ducatto base ( there is a free banner 100ah lead battery going spare if anyone wants it)

All the cables look nice and chunky as opposed to the weedy cables on my previous autotrail so I temporarily dropped in my bluetooth 200ah lithium to see what power the alternator would provide and was suprised to see the alternator was throwing in between 30 -39 amps.
The battery was 70% charged, and when revving the engine the input would jump from 30-37-39- even 50 amp ish. I havent added the b2b yet.

Do alternators throw this kind of power to batteries, does it maybe have another charge system inline somehwere which may explain the 50amp fuse and 16mm cable I noticed coming out off the cab battery dissappearing udner the floor ? (not traced it yet) (see pic)

Im quite surprised, and happy enough f Im getting 30 -45 amp before I even ft the b2b, and with it being a euro 6 vehicle, its a smart alternator Im guessing.
Can anyone tell me that yes 30-39 amp from the ducatton Rapido is quite normal before even fitting a b2b.

And what is the silver box above the batteries? can anyone tell
edit: seems the silver box is the air bag sensor

Also depending on how the charge is being sent to the battery do you think I woudl have to disable this system so as not to cause a loop, when fitting my B2B, whichh seems to defeat the object of the B2B.
thanks

 

[SandraL]

Silver box looks like the airbag ecu, will be forward of battery hatch at base of central glove box on the floor.

 

[stevewagner]

Definitely need to disconnect the charging relay. If you have the CBE system you only need to snip the R37 resistor.

 

[Tombola]

Thanks stevewagner I do have cbe

Im in a quandry, the b2b im going to install, is 30 amp ( i may fit 2 to get 60)
but whats the point if the exisiting charge system is throwing in 40-50 amps? according to the bluetooth on my lithium battery?
OR MAYBE, is my lithium pulling too much than it should from the alternator maybe ?...confused?

 

[stevewagner]

I have a 60amp B2B fitted to mine which works well. I’m not sure how long your alternator would put out that amount of current and whether it would reduce down before the hab batteries are fully charged.

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[paddymcc]

I think some motorhomes with smart alternators have a b2b fitted as standard. Could this be the case with yours? The question then is does it have a lithium charging profile?

 

[Raul]

Thanks stevewagner I do have cbe

Im in a quandry, the b2b im going to install, is 30 amp ( i may fit 2 to get 60)
but whats the point if the exisiting charge system is throwing in 40-50 amps? according to the bluetooth on my lithium battery?
OR MAYBE, is my lithium pulling too much than it should from the alternator maybe ?...confused?

The B2B is to limit/ regulate the charge rate, not increase. You can increase by double up the B2B or fit a large one. Lithium are capable to suck more amps than your alternator is capable of. So the B2B limits the charge rate to protect the alternator. With smart alternators a B2B is a must either way, lithium or not.

 

[Tombola]

I have a 60amp B2B fitted to mine which works well. I’m not sure how long your alternator would put out that amount of current and whether it would reduce down before the hab batteries are fully charged.

I dunno, I dont see one in the locker or anywahere, I was just surprised to see getting up toward 50amps going in from the "alternator" alone

I think some motorhomes with smart alternators have a b2b fitted as standard. Could this be the case with yours? The question then is does it have a lithium charging profile?

exactly, Ive looked in all the obvious places and but the the 50amp fuse and 16mm cable coming out of the cab battery does look like it leads to one, but goes right into the cbe.

Possiblt best for me to "dry fit" the b2b and run the engine a while and get out the volt meter and amp clamp

 

[paddymcc]

I think if you have followed the wire accurately ( difficult sometimes) then there isn't a b2b. Not familiar with CBE - do they have different charging profiles like the Schaudt EBL? Did you measure the voltage at the lithium battery to see what the voltage was when on charge from the alternator?

 

[Tombola]

I think if you have followed the wire accurately ( difficult sometimes) then there isn't a b2b. Not familiar with CBE - do they have different charging profiles like the Schaudt EBL? Did you measure the voltage at the lithium battery to see what the voltage was when on charge from the alternator?

the blutooth monitor on the battery said I thnk 14.4-7 going in, Il check again though tomorrow

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[andy63]

The point about snipping the resistor on the cbe board to disable the existing split charge system may be possible but I know that some variants of the cbe set up don't have that resistor ..certainly not as depicted on Internet searches..
My cbe system which employed the two heavy duty external relays that allowed split charging didn't have or need such a resistor..
The battery to battery charger is imo definitely the way to go especially with lithium..as has been said...to protect the alternator and ensure a controlled charge cycle..
Andy

 

[tonyidle]

The B2B is to limit/ regulate the charge rate, not increase. You can increase by double up the B2B or fit a large one. Lithium are capable to suck more amps than your alternator is capable of. So the B2B limits the charge rate to protect the alternator. With smart alternators a B2B is a must either way, lithium or not.

50A is nowhere near exceeding the rated output of the alternator. Why would it need protection? It isn't possible to take more than it can give. It will have a preset voltage limit that, provided the limit is lower than the max required by the battery, will reduce the current drawn as the battery approaches full charge. Where lithium differs from lead acid is a very low internal resistance allowing it to draw a high charge until the BMS says stop. Lead acid charge tapers off as the battery terminal voltage gradually rises. I may of course be missing something .

 

[Tombola]

50A is nowhere near exceeding the rated output of the alternator. Why would it need protection? It isn't possible to take more than it can give. It will have a preset voltage limit that, provided the limit is lower than the max required by the battery, will reduce the current drawn as the battery approaches full charge. Where lithium differs from lead acid is a very low internal resistance allowing it to draw a high charge until the BMS says stop. Lead acid charge tapers off as the battery terminal voltage gradually rises. I may of course be missing something .

Yeah I understand Tony, the one issue though is with smart aletrnators, they dont spin fast enough at low revs to keep cool when the demand from lithium batteries remains high, Thats what Im worried about? Im ready to do the b2b but was surprised and cant understand how / why the battery is getting 50 amps if from where first ?

see this link regrading euro5 alternators and lithium, I dlike to be able to leave it getting the 50amps Im seeing but fear this will be the outcome

 

[the1andonly]

IF you have a CBE300 from 2017 it will have an R37 zero ohm link, removing it or a quick snip (not a vascectomy) disables the std split charger. Have you found a smart alternator yet. R37 bottom left hand corner.

earlier versions do not have this facility. I dont know about smart alternator models. First check if it is a 300 or a 3xx model.
edit i think Rapidos up to 2020 model year did not have a smart alternator

 

[tonyidle]

Yeah I understand Tony, the one issue though is with smart aletrnators, they dont spin fast enough at low revs to keep cool when the demand from lithium batteries remains high, Thats what Im worried about? Im ready to do the b2b but was surprised and cant understand how / why the battery is getting 50 amps if from where first ?

see this link regrading euro5 alternators and lithium, I dlike to be able to leave it getting the 50amps Im seeing but fear this will be the outcome

Im still at a loss to understand 'low rpm'. Alternator belt drives are arranged with a step-up of around 3:1 so the lowest alternator speed will be 3x engine Idle at worst. Say 2500 rpm. Under normal driving conditions it will turn at 8000 to 9000 rpm which should provide adequate cooling. How does it cope on a cold, wet, night with almost every service in the vehicle in use?

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[andy63]

Im still at a loss to understand 'low rpm'. Alternator belt drives are arranged with a step-up of around 3:1 so the lowest alternator speed will be 3x engine Idle at worst. Say 2500 rpm. Under normal driving conditions it will turn at 8000 to 9000 rpm which should provide adequate cooling. How does it cope on a cold, wet, night with almost every service in the vehicle in use?

I sort of get your point but inclined to think that under idle conditions for a sustained period there may be insufficient cooling for the load..
A battery to battery could limit the load if chosen sensibly...all be it at the cost of taking a bit longer to charge the battery..
Another point maybe worth fitting a batt to battery for would be to deal with the
The voltage swing on a smart alternator which is influenced by factors other than the need to keep leisure batteries charged so the start battery is acting as a sort of buffer in the short term ..
Certainly the Stirling units have a timed phase to deal with such circumstances ..

Andy

 

[autorouter]

You can find out if a B2B is fitted by measuring the voltage of the starter and leisure batteries, preferably at the same time, while the engine is running. If they are always the same, then it's a split charge relay. If there's a difference, say 13V starter and 14.5V leisure, then there's a B2B. Note, there are some circumstances where the voltages are about the same with a B2B, but mostly they are different.

A B2B will increase the amps from a smart alternator when it would otherwise stop charging the starter battery. It will control the amps output to a safe level in the rare scenario of a flat lithium leisure battery and a traffic jam in hot weather, that might overheat the alternator. Most of them will also stop charging the lithium battery if the temperature is zero or less.

 

[Tombola]

You can find out if a B2B is fitted by measuring the voltage of the starter and leisure batteries, preferably at the same time, while the engine is running. If they are always the same, then it's a split charge relay. If there's a difference, say 13V starter and 14.5V leisure, then there's a B2B. Note, there are some circumstances where the voltages are about the same with a B2B, but mostly they are different.

A B2B will increase the amps from a smart alternator when it would otherwise stop charging the starter battery. It will control the amps output to a safe level in the rare scenario of a flat lithium leisure battery and a traffic jam in hot weather, that might overheat the alternator. Most of them will also stop charging the lithium battery if the temperature is zero or less.

perfect. just what I was looking for, thanks

 

[cyberyacht]

If it's any help, my 2016 Carthago (Euro 5) alternator pushes around 20A into my lithiums. I haven't fitted a B2B.

 

[andy63]

If it's any help, my 2016 Carthago (Euro 5) alternator pushes around 20A into my lithiums. I haven't fitted a B2B.

Does that change depending on the state of charge of the batteries...or are you saying that's what you always see..it must surley drop when the batteries charge..
And without a battery to battery your lithium are subjected to alternator voltage regardless.. with a battery to battery it would drop to what they would call a float charge...
But if it worksit works and only time will tell how effective it is..
Andy

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[cyberyacht]

About 12A on ticker, rising to 20A when driving. I checked the input on the KS Energy battery app via bluetooth on my phone. Haven't monitored it in any great detail. Battery was at 55% upon leaving home for a day out and 71% upon return.

 

[NicM]

Im still at a loss to understand 'low rpm'. Alternator belt drives are arranged with a step-up of around 3:1 so the lowest alternator speed will be 3x engine Idle at worst. Say 2500 rpm. Under normal driving conditions it will turn at 8000 to 9000 rpm which should provide adequate cooling. How does it cope on a cold, wet, night with almost every service in the vehicle in use?

Well they are trying to sell you something to fix the problem.

 

[tonyidle]

I sort of get your point but inclined to think that under idle conditions for a sustained period there may be insufficient cooling for the load..
A battery to battery could limit the load if chosen sensibly...all be it at the cost of taking a bit longer to charge the battery..
Another point maybe worth fitting a batt to battery for would be to deal with the
The voltage swing on a smart alternator which is influenced by factors other than the need to keep leisure batteries charged so the start battery is acting as a sort of buffer in the short term ..
Certainly the Stirling units have a timed phase to deal with such circumstances ..

Andy

I agree completely that sustained idle is likely to cause alternator overheating. My argument with the video trying to explain the issue was that they appeared to equate engine idling rpm with alternator rpm. I need to understand smart alternators - I've not had one so have never worried too much

 

[Lenny HB]

cant understand how / why the battery is getting 50 amps if from where first ?

Quite normal if the wiring has the correct size cables I've clocked 45 amps into my Gel batteries from the standard split charge system on my Hymer I think the cables are 25mm sq.
Your previous Autotrail would have had pathetically undersized cables which will have severely limited the charge rate.

 

[andy63]

I agree completely that sustained idle is likely to cause alternator overheating. My argument with the video trying to explain the issue was that they appeared to equate engine idling rpm with alternator rpm. I need to understand smart alternators - I've not had one so have never worried too much

not really got much of a clue myself.. I always understood the term smart alternator to mean that the output of the alternator was controlled by the vehicle body control module and engine ecu....and not simply a voltage regulator built into the back of the unit as was the case..so it can respond to pretty well anything that have a mind to programme.... ie engine load, braking , acceleration , state of battery, etc etc
that simple lol
Andy