Do I need a B2B or can alternator cope?

[Lenny HB]

If your set up can only give out 18 or 20a then no danger of the battery pulling 100 or 200 is there? And unless you're on the M25 its unlikely you'll be sitting idling for long?

All depends on the wiring, I've had Gel batteries charging at 45 amps on a Hymer.

 

[dunnah01]

Last thing you want to do with a modern diesel unless you like very expensive repair bills.

But it's a bullet proof 2009 non dpf 3.0l lump so not a problem tbh

 

[Lenny HB]

But it's a bullet proof 2009 non dpf 3.0l lump so not a problem tbh

Still has a CAT, and modern diesels never get up to operating temperature on tickover from cold so can lead to glazed bores and other problems, not worth the risk.

 

[MichaelT]

All depends on the wiring, I've had Gel batteries charging at 45 amps on a Hymer.

Yes but not 100 or 200a. A 50a B2B is surely putting more stress on the alternator than a 20a system?

 

[Lenny HB]

Yes but not 100 or 200a. A 50a B2B is surely putting more stress on the alternator than a 20a system?

Unless you have a B2B it's only limited by the wiring and a lot of alternators charge at 14.7 - 15 v which is too high for lithium.

I really don't understand why people spend a fortune on Lithium then bitch about spending a bit on changing them properly, it's going to be a lot more expensive if you bu**er them.
Why not treat them properly and get the best out of them.

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[MichaelT]

Unless you have a B2B it's only limited by the wiring and a lot of alternators charge at 14.7 - 15 v which is too high for lithium.

I really don't understand why people spend a fortune on Lithium then bitch about spending a bit on changing them properly, it's going to be a lot more expensive if you bu**er them.
Why not treat them properly and get the best out of them.

Well we ran ours for 3 years and battery is still going strong no damage. May not be optimum but I doubt I'll ever get to the 5000 cycles as so far it's about 30 per year. B2B is 600 odd quid if you can't fit yourself and 400 if you can so about the price of a lithium at today's prices.

Still not said if a 50a B2B puts more stress on an alternator than 20a?

 

[OldAgeTravellers]

Well we ran ours for 3 years and battery is still going strong no damage. May not be optimum but I doubt I'll ever get to the 5000 cycles as so far it's about 30 per year. B2B is 600 odd quid if you can't fit yourself and 400 if you can so about the price of a lithium at today's prices.

Still not said if a 50a B2B puts more stress on an alternator than 20a?

You are a bit out of date with prices. A Victron XS is about £250, cheaper for Fun members from Offgrid Power Solutions.

 

[StillGoing]

B2B is 600 odd quid if you can't fit yourself and 400 if you can so about the price of a lithium at today's prices.

I spent nothing like £400 to fit a Victron XS 50A. I’ve just looked online and you can get one for about £256.

 

[mitzimad]

weve got a 11o amp lithium running from a split charger its over 4 years old no problems

 

[AdrianChen]

Still not said if a 50a B2B puts more stress on an alternator than 20a?

In our case the limiting factor would be the wiring, so the 50amp b2b output is reduced to suit rather than allowing the cables (and the bundle it is in) getting hot, but not sure why you in your case were only getting 20amps (net charge or after any drain from fridge etc?). In those circumstances I'm guessing the wiring resistance and voltage drop was protecting the alternator, that's one way to do it, not one I'd recommend to a friend without understanding their setup though.

I opted to set the b2b output to a level that's OK with the cable sizes until I get round to changing it, and all is kept well within the capacity of the alternator, which I understood to be 30-40% of the alternator output. My only concern was if our 460AH battery empty might take long enough to recharge to let the heat build much more than with a smaller battery.....

So for me the relevant detail is the capacity of all the components in the circuit/system including alternator capacity and spec vs my capacity for risk taking, which is low!

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[Tombola]

I think I may remove my smoke detector and carbon monoxide, I mean after all, whats the chances. Slim right and will save me a few more quid.

then again I should really do it right.

 

[Bessy765]

We have 700 watts of solar 2 x 100 Transporter Lithium and a Victron 12/2000/80 inverter/charger heavy duty cabling 150 amp alternator. Burstner IEXO 736 Fiat 2300 150 Comformatic. Professional installation warranted for 5 years batteries for 10. No B2B fitted as installer stated not required an easily pulll 80 amps plus when driving, the only advice if stationary running the engine just to charge the batteries no more than 15 mins. Voltage is around 14.4 when charging as batteries get nearly full the amps drop down. Over four years 24,000 miles no problems.

 

[MichaelT]

You are a bit out of date with prices. A Victron XS is about £250, cheaper for Fun members from Offgrid Power Solutions.

Plus cables, fuses etc.

 

[MichaelT]

In our case the limiting factor would be the wiring, so the 50amp b2b output is reduced to suit rather than allowing the cables (and the bundle it is in) getting hot, but not sure why you in your case were only getting 20amps (net charge or after any drain from fridge etc?). In those circumstances I'm guessing the wiring resistance and voltage drop was protecting the alternator, that's one way to do it, not one I'd recommend to a friend without understanding their setup though.

I opted to set the b2b output to a level that's OK with the cable sizes until I get round to changing it, and all is kept well within the capacity of the alternator, which I understood to be 30-40% of the alternator output. My only concern was if our 460AH battery empty might take long enough to recharge to let the heat build much more than with a smaller battery.....

So for me the relevant detail is the capacity of all the components in the circuit/system including alternator capacity and spec vs my capacity for risk taking, which is low!

That was without B2B on our old van.

 

[AdrianChen]

That was without B2B on our old van.

Yes, but if the alternator can supply more and the battery at the right charge voltage would accept more what is limiting the charge to 20amps? Cables, relay, or some other device?

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[SteveandSueJ]

I wish I knew what my alternator did output. Can't see it. 3ltr 2009 comformatic on fiat Ducato in case anyone knows... Thx.

 

[Lenny HB]

I wish I knew what my alternator did output. Can't see it. 3ltr 2009 comformatic on fiat Ducato in case anyone knows... Thx.

It's down to what the convert pecs when they buy the chassis could be anything from 90 to 180 amps only way to check is to get the part number on the alternator.

 

[MichaelT]

Yes, but if the alternator can supply more and the battery at the right charge voltage would accept more what is limiting the charge to 20amps? Cables, relay, or some other device?

I'm guessing the EBL/split charger, whatever Dethleffs fitted. I took the view that I would see how it went, if we were not able to charge or ran out I'd fit a B2B but it all worked well as a drop in changing solar to lithium profile (did bulk if charging) and EBL to gel, rarely hook up and it worked fine. As I said not optimum but saved few hundreds.

 

[wfdTamar]

You can get a Votronic 30 Amp B2B for about £120, maybe £150 with the wiring (DIY).

Or get a 110Ah lead carbon gel (or two if you can fit them). 750 cycles at 80% discharge.

 

[Tude]

You should always fit a B2B with Lithium not only does it give the correct charge profile for the battery it also protects the alternator.

Some CBE chargers have an automatic desulphation phase if yours has t's not suitable for Lithium.
Also if using EHU for more than the odd few night it is best to fit a mains charger with a Lithium profile.

Absolutely spot that n Lenny

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[Cliff Bryant]

I'm guessing the EBL/split charger, whatever Dethleffs fitted. I took the view that I would see how it went, if we were not able to charge or ran out I'd fit a B2B but it all worked well as a drop in changing solar to lithium profile (did bulk if charging) and EBL to gel, rarely hook up and it worked fine. As I said not optimum but saved few hundreds.

How can a split charge relay limit the current? It merely connects the alternator to the habs battery. A B2B is an essential item to protect the alternator, the wiring and possibly the battery (if lithium).

There are lots of anecdotal comments like "I ran if for x years" or "well it worked for me" but if you look at the usage case there is usually a luck factor involved. EG the habs battery was only 15% discharged. It is a fact that a lithium can be charged at 1C and so if nearly flat it is capable of taking typically 100A from the alternator unless limited by the wiring (which was designed for a Pb battery with a 0.2C max charge). Proper engineering requires proper solutions. You also have to factor in the lower voltage from a smart alternator. A decent B2B capable of supplying 30A output will recharge a 100Ah flat battery in 3.5 hours and will do so regardless of the alternator voltage. It will also limit the maximum current the alternator must supply and protect the wiring. If the battery is only down to say 80% it will charge in less than one hour.

I have a B2B, a charger with a proper lithium profile and a 75V/15A MPPT solar regulator. It was easy to fit and it all just works without any risk of damage. Moreover I can easily remove it all when I sell the van and move it to a new vehicle if I so desire.

 

[MichaelT]

How can a split charge relay limit the current? It merely connects the alternator to the habs battery. A B2B is an essential item to protect the alternator, the wiring and possibly the battery (if lithium).

There are lots of anecdotal comments like "I ran if for x years" or "well it worked for me" but if you look at the usage case there is usually a luck factor involved. EG the habs battery was only 15% discharged. It is a fact that a lithium can be charged at 1C and so if nearly flat it is capable of taking typically 100A from the alternator unless limited by the wiring (which was designed for a Pb battery with a 0.2C max charge). Proper engineering requires proper solutions. You also have to factor in the lower voltage from a smart alternator. A decent B2B capable of supplying 30A output will recharge a 100Ah flat battery in 3.5 hours and will do so regardless of the alternator voltage. It will also limit the maximum current the alternator must supply and protect the wiring. If the battery is only down to say 80% it will charge in less than one hour.

I have a B2B, a charger with a proper lithium profile and a 75V/15A MPPT solar regulator. It was easy to fit and it all just works without any risk of damage. Moreover I can easily remove it all when I sell the van and move it to a new vehicle if I so desire.

Well all I can say is I didn't have a B2B and it worked so work that out

 

[Cliff Bryant]

Well all I can say is I didn't have a B2B and it worked miting.

Well all I can say is you may well have a fire one day.

Well all I can say is I didn't have a B2B and it worked so work that out

Go on to Google and watch the video showing an alternator connected directly to a lithium battery and watch the ensuing fire. Then tell your insurance company about your "just worked" set up.

All I can say is it's dangerous to mess with things you don't understand and a lithium battery is a very different chemistry from a Pb battery.

 

[Lenny HB]

Well all I can say is I didn't have a B2B and it worked so work that out

You was lucky IMO not worth the risk.

 

[MichaelT]

Well all I can say is you may well have a fire one day.

Go on to Google and watch the video showing an alternator connected directly to a lithium battery and watch the ensuing fire. Then tell your insurance company about your "just worked" set up.

All I can say is it's dangerous to mess with things you don't understand and a lithium battery is a very different chemistry from a Pb battery.

That was static and not moving, other videos showing its perfectly OK with no issues.

And as I said 18 amps v 50amps from B2B what's putting more strain on the alternator?

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[Cliff Bryant]

That was static and not moving, other videos showing its perfectly OK with no issues.

And as I said 18 amps v 50amps from B2B what's putting more strain

That was static and not moving, other videos showing its perfectly OK with no issues.

And as I said 18 amps v 50amps from B2B what's putting more strain on the alternator?

Have you connected a fully discharged lithium and then measured the current? How does the system correctly charge the lithium battery in the two modes required (current then voltage)? What limits the maximum voltage from the alternator to that allowed for the lithium chemistry? How does the system cope if the alternator is smart and the output voltage is reduced?
Static or moving makes no difference to any of the above.
There is no 'strain' applied to an alternator, it is called a load. As long as the load is within parameters the alternator will supply current.
Without a suitable B2B you will charge a lithium in a haphazard manner and risk the issues I have highlighted.
As I said before the two battery chemistry's are quite different and charging systems must be designed accordingly for safe and long lived operation.
A suitable B2B and charger costs very little compared to a vehicle why would you not do the job properly?

 

[Lenny HB]

That was static and not moving, other videos showing its perfectly OK with no issues.

And as I said 18 amps v 50amps from B2B what's putting more strain on the alternator?

Must have been your wiring been very small, as I said on a Hymer I've had 44 amps into Gels from the split charge relay.
As I've said it's just not worth the risk why not do the job propery.

 

[MichaelT]

Have you connected a fully discharged lithium and then measured the current? How does the system correctly charge the lithium battery in the two modes required (current then voltage)? What limits the maximum voltage from the alternator to that allowed for the lithium chemistry? How does the system cope if the alternator is smart and the output voltage is reduced?
Static or moving makes no difference to any of the above.
There is no 'strain' applied to an alternator, it is called a load. As long as the load is within parameters the alternator will supply current.
Without a suitable B2B you will charge a lithium in a haphazard manner and risk the issues I have highlighted.
As I said before the two battery chemistry's are quite different and charging systems must be designed accordingly for safe and long lived operation.
A suitable B2B and charger costs very little compared to a vehicle why would you not do the job properly?

It wasn't s smart alternator if you read it!

 

[MichaelT]

Must have been your wiring been very small, as I said on a Hymer I've had 44 amps into Gels from the split charge relay.
As I've said it's just not worth the risk why not do the job propery.

It was a proper job worked fine and saved me 500.

 

[ivorantony]

You can get the horse to the trough, But you cannot make it drink

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