A question based on almost no knowledge of Lithium batteries

[rosalan]

At the Lincoln Show I was easily pursueded to move up to a Lithium battery after freezing in the dark last New Year.
I bought a 175Lithiumpro Arctic v2, a 2000w 12v Sunshine Power inverter (PSW) and a Victron IP22 12v 30amp charger. Mainly
by recommendations from Glen at Lithiumpro. All fitted by Sunshine Solar, so it works BUT do I now NEED a battery to battery device?
I had one before but I understand it won't work now. Will I miss it?
Sorry this is so long winded but they all seem to be linked together.

 

[Outdoors Dad]

I moved to lithium a couple of years ago and with advice from here I fitted a B2B charger. I didn't fit a mains charger and disconnected the old unsuitable charger. I would fit one if it was me as your old split charger might not be very lithium friendly.

 

[DBK]

The B2B is for rapid charging. If you have plenty of solar panels then in the summer you may find your battery is fully recharged at the end of the day. However, in winter or bad weather this will be a struggle. This is where the B2B comes into it's own as depending on capacity it might fully recharge the battery after a relatively short drive.

My suggestion would be to use the setup you now have and see how you get on. You should soon discover whether you need a B2B or not.

 

[Guigsy]

I upgraded to lithium and ran for many months without a B2B. I found that the voltage provided direct from the alternator would push up to 20A at the battery. But only when the battery was at a fairly low state of charge. To fully charge the lithium battery, it needed more voltage than the alternator was supplying. So I'd only get a partial charge.

The other issue was the 3-way fridge is wired into the same circuit and consumes about 15A. So there's not a lot left for the battery anyway. Although I didn't find it that limiting. Note that many vans have the fridge circuit on a separate feed, so you may not have this issue.

Later, I upgraded to a 30A Votronic B2B. Mostly because it provided a really simple method to patch it in with virtually no wiring changes. It sits between the cab battery and my Elektroblock. I didn't have to disable anything. But because I'm still passing through the EBL, I'm limited to 30A. If I wanted more, I'd have got a 50A B2B and had to bypass the EBL.

 

[MichaelT]

Just wondering if you already have one which is why Glenn from lithiumpro didn't reccomend one as it would of been a bit more business for him?

We didn't have one on last van just used onboard charger via ebl on gel and solar on lithium profile, never ran out and all worked fine. Have a 50a B2B on new van as its got a smart alternator and more battery power and we use electric for cooking now we don't have an oven.

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[AdrianChen]

If you had one before, where's it gone? I assume you mean a b2b to charge your new lithium from the start battery/alternator when driving?

They do a few important things if you want to charge the battery from the alternator VS a split charge relay.

1) They stop an empty lithium battery from keeping the alternator maxed out for too long, such that it may overheat especially on a large battery. This may not be an issue on your's at 175amp but personally I would prefer it.
2) They limit the current flowing to something the alternator and wiring can handle, which to me is better than undersized wiring limiting the current flow
3) They provide the correct charging profile for a Lithium battery, so it will help prolong it's life.
4) If your van has a Smart alternator, there will be very little output from it, unless your engine battery is low since the smart alternator will only charge when you are braking, or on the overrun when it can put out over 15v - which is too much for a Lithium. The B2B will convert the low voltage output to the correct voltage to charge the Lithium

Lots of folk will tell you they are not needed if you don't have a smart alternator, but personally I do, so I know the cables and currents are safe, and within a reasonable load on the alternator.

 

[autorouter]

All fitted by Sunshine Solar, so it works BUT do I now NEED a battery to battery device?
I had one before but I understand it won't work now. Will I miss it?

Do you know what make/model of B2B was fitted? Maybe post a picture of it if you're not sure. Did they say it definitely won't work, or that it won't be very good? Did they disable it or is it still running?

 

[rosalan]

Do you know what make/model of B2B was fitted? Maybe post a picture of it if you're not sure. Did they say it definitely won't work, or that it won't be very good? Did they disable it or is it still running?

I have been advised that the original ‘built in’ b2b which worked between a wet engine battery and an agm battery and was displayed on the display panel, would not be suitable for use with lithium. To be honest I cannot tell if it does or does not as previously the display only showed b2b on very few occasions. When? I am not sure!

 

[autorouter]

If the inbuilt B2B had only an AGM charging profile then they are right, it wouldn't be suitable for a lithium battery - the voltage would be about 14.8V which is too high. However if the wiring is there already, then it shouldn't be a big deal to swap it for a B2B with the same amps output, that has a lithium profile. But to gain the most benefit you should consider a higher power B2B, maybe 60A or 70A, that would take advantage of lithium's ability to charge faster than the old batteries. That option would need new thicker wires running to it.

Note that the name 'B2B' is a bit misleading - the leisure battery gets charged from the alternator, not the starter battery. The B2B only switches on when the alternator is producing charge, and is already charging the starter battery. The alternator produces extra charge, which is sent through the B2B to the leisure battery.

 

[AdrianChen]

Deleted to avoid causing confusion!

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[Hoovie]

If you had one before, where's it gone? I assume you mean a b2b to charge your new lithium from the start battery/alternator when driving?

They do a few important things if you want to charge the battery from the alternator VS a split charge relay.

1) They stop an empty lithium battery from keeping the alternator maxed out for too long, such that it may overheat especially on a large battery. This may not be an issue on your's at 175amp but personally I would prefer it.
2) They limit the current flowing to something the alternator and wiring can handle, which to me is better than undersized wiring limiting the current flow
3) They provide the correct charging profile for a Lithium battery, so it will help prolong it's life.
4) If your van has a Smart alternator, there will be very little output from it, unless your engine battery is low since the smart alternator will only charge when you are braking, or on the overrun when it can put out over 15v - which is too much for a Lithium. The B2B will convert the low voltage output to the correct voltage to charge the Lithium

Lots of folk will tell you they are not needed if you don't have a smart alternator, but personally I do, so I know the cables and currents are safe, and within a reasonable load on the alternator.

A nice clear summary of the benefits of a B2B I would agree with all these.

I would also add that not all B2B chargers are created equal, especially when talking about vans with Smart Alternators. Many rely on the input voltage being at a certain level to turn them on (even if they have a D+ activation signal as well) and will not reliably work (your point #4 is also applicable to many B2Bs sadly and just last week I had to swap out an NDS B2B that would not turn on 90% of the time (and it was a swap for the original NDS B2B with the same problem). Changed it for a Victron Orion-XS and even then had to disable engine detection (algorithm not great for Euro 6) and lower the lockout voltages for it to work (and also used the D+ line to make sure only active when engine on)

 

[Lenny HB]

Lots of folk will tell you they are not needed if you don't have a smart alternator, but personally I do, so I know the cables and currents are safe, and within a reasonable load on the alternator.

Totally agree I think it's very silly to fit a Lithium without a B2B with the correct charging profile.

Changed it for a Victron Orion-XS and even then had to disable engine detection (algorithm not great for Euro 6) and lower the lockout voltages for it to work (and also used the D+ line to make sure only active when engine on)

The XS is a great bit of kit but the instructions are naff. It took me a while and a bit of playing around to get mine working.
I turned off both engine detection & lockout just use the D+ it works faultlessly.

 

[Hoovie]

Totally agree I think it's very silly to fit a Lithium without a B2B with the correct charging profile.

The XS is a great bit of kit but the instructions are naff. It took me a while and a bit of playing around to get mine working.
I turned off both engine detection & lockout just use the D+ it works faultlessly.

After having similar hassles getting a Orion-Smart TR working with a new van w/Smart alternator, I could hit the ground running when I fitted the XS to another one

I would agree that it will work successfully without the lockout enabled, but I decided to keep that active (but set to a much lower voltage) as a precaution ... In the unlikely - but possible - event where the D+ signal is incorrectly held high without the engine running, if the charger activation was solely based on D+ condition, you could end up draining the starter battery.
Yes, pretty unlikely for sure to have a D+ fault like that, but it is possible.
And if the Alternator was faulty but D+ was still high, this would drain the starter battery as well with that setting (I have just replaced my own Alternator last week as it had zero output. I didn't check the D+ signal as I don't use it on my van, but I think despite the lack of current coming out it was still high?).
So I would suggest maybe re-enabling the voltage lockout but at a more suitable level just as a precaution?
(I also gave the owner screenshots of the relevant Orion-XS manual pages with Victrons defaults - and what I had changed them to to have it actually work for their motorhome )

 

[rosalan]

My original query stated I had little or no knowledge of lithium batteries and the solution seems that it is essential to know advanced electronics and still my favourite guru stumbled. What hope for me?

 

[AdrianChen]

And if the Alternator was faulty but D+ was still high, this would drain the starter battery as well with that setting (I have just replaced my own Alternator last week as it had zero output. I didn't check the D+ signal as I don't use it on my van, but I think despite the lack of current coming out it was still high?).
So I would suggest maybe re-enabling the voltage lockout but at a more suitable level just as a precaution?

On old alternators the D+ signal was generated by a separate diode trio from the main rectifiers diode pack, It was mainly used as the supplier of the field current through an alternators internal regulator, and also turned off the ignition light. Whilst its voltage was the same as the output from the main diode pack, it's amperage was very limited but a D+ terminal was provided on most alts that could be used with relays etc.

So it is quite possible an alternators main output can fail, whilst the D+ still provides an output - as you say it's probably rare....

Having waffled on about that, modern alternators may well be different!

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