Lithium batteries cannot just drop in and replace lead batteries can they?

[olley]

Logic is such a spoil sport

 

[Garry - June]

Its very much Horses for Courses...everyone's wants and needs are different...we fulltime in our van which obviously influences a lot of our decisions..

 

[bigtwin]

I don't think so with LA as the voltage across the terminals increases the the charge rate will drop due to increased internal resistance.
With Lithium the voltage stays pretty constant although they are normally charged at 14.2v if the voltage drops to 13.5 they will still suck in 100 amps if they can, so that bit of thin wire is going to get very hot.

They will only suck in 100A if the alternator is capable of delivering 100A. If the system has been designed, and installed, correctly the cable should have been designed to handle the maximum that the alternator can deliver (and the use of terms such as skinny, long thin wire is unhelpful). The lithium is just a load, the cable should be sized for the power source (alternator) delivery capability. This isn’t a lithium issue, this is a bad design issue where cables are inadequately sized and is simply bad practice.

Ian

 

[nickq]

They will only suck in 100A if the alternator is capable of delivering 100A. If the system has been designed, and installed, correctly the cable should have been designed to handle the maximum that the alternator can deliver (and the use of terms such as skinny, long thin wire is unhelpful). The lithium is just a load, the cable should be sized for the power source (alternator) delivery capability. This isn’t a lithium issue, this is a bad design issue where cables are inadequately sized and is simply bad practice.

Ian

I don't think that's quite fair. Cable size will be sized for maximum designed load, not the power source as that is just theoretical. I could have 100A alternator and my load might never exceed 10A for example, the alternator (or any power source for that matter) will never deliver 100A in that situation. Current is drawn from a power source, not delivered by the power source.

I think what you are really saying is that it would be better practice to assume over the life of a van that the load may change due to upgrades etc. In which case the original design specification has changed. Therefore it may be a good practice to overspec the cabling beyond the original design and bringing that in to line with the alternator rating "could" be useful if the future change in load design can still be delievered without changing the alternator. But that is no guarantee either. Would be nice yes, however that will come at extra cost.

But what are you asking here? That the cabling is 150A capable? Pairs of 16mmsq heading all the way to the distribution box and to both batteries? Over-engineering is not good practice, good practice is engineering the entire system to the design requirement specification.

 

[Vansflyer]

I finished this "little project" about a month ago and it is now fully tested after a week away last week.
Originally I tried fitting the Orion units in the garage next to the fuse board and had a short connection to the B1 and B2 terminals. The losses on the cable were significant and despite it being 16mm cable at the fuse box somewhere along the run it dropped to about 12 or 10mm. This is on a Carthago C-Tourer which in theory has chunky "German spec" cables. What was also a surprise is the fridge pulling around 13A when on 12V.
So back to the drawing board and relocated the Orions to nsf locker under the bench seat, close to the new Fogstsr 290ah under the floor and much closer to the cab battery.
52 or 56mm cable (can't remember) to the cab battery and at fuse points / connections changed to 16mm for access into the Orion units. Patched the hab feed into the inverter feed so it minimised the chunky cables going into the battery locker.
All is working well now and as it should giving me around 45A into the hab battery when B2B running (with fridge on 12v) and if sunny the 300w solar adds another 10A + to that.
A couple of points.
I tried the split charge option briefly and it put in about 13A into the hab battery but didn't want to trust the BMS and I had no way of controlling the charge.
Fans are fitted to the Orion units to prevent them getting hot and reducing the charge, one unit has a 3d ducting on and the other two fans blowing straight across the fins to see which method is more efficient. Currently the "straight across the fins" unit seems cooler but neither are throttling back the charge or getting more than about 30c when working.
Whilst on site for 7 days last week without EHU we never dropped below about 90% soc and even on dull days with no engine running we we charged up on solar by early afternoon at the latest and that is with 2 internal fridge fans running 24/7 but that is another story...but we do now have a working fridge at last!
Fogstar 280ah needed that handles cut off to fit in the battery box. Fogstar said not a problem for the warranty if I cut them off.. the dims were wrong on their website and showed battery dims without handles.
Currently setting up "a return to home" profile on the Victron's to get the battery to 70% soc on return trip and no more.

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[DavidCh]

I will say that you could use the Renogy B2B unit which does not require the D+ signal as it works on the voltages. I actually ran the D+ on mine but did not connect it as it ran perfectly well without it.

 

[eddie]

All nicely charging circa 110 amps all connected up with 50mm2 multi strand Copper wire

"Wot voltage drop?"

 

[Lenny HB]

I will say that you could use the Renogy B2B unit which does not require the D+ signal as it works on the voltages. I actually ran the D+ on mine but did not connect it as it ran perfectly well without it.

You can do that with all B2B's but useless if you have solar charging the starter battery. It will create an endless loop, when the starter battery reaches the trigger voltage of the B2B it will turn on and start charging the leisure battery, flattening the starter battery, starter battery gets low the B2B will turn off and the cycle starts again.
Same thing happens when charging from mains but not quite so important.

 

[DavidCh]

You can do that with all B2B's but useless if you have solar charging the starter battery. It will create an endless loop, when the starter battery reaches the trigger voltage of the B2B it will turn on and start charging the leisure battery, flattening the starter battery, starter battery gets low the B2B will turn off and the cycle starts again.
Same thing happens when charging from mains but not quite so important.

Absoolutly correct, except that the Renogy I have is also a solar charger so sorts that out. The only downside is that it is a 50amp B2B and it will use both solar and the alternator and restricts the alternator to 25A if there is anything on the solar. This suits me for normal operation but if I need the full 50A from the alternator I just switch off the solar.

 

[Lenny HB]

Absoolutly correct, except that the Renogy I have is also a solar charger

You didn't say it was a dual one, you said Renogy B2B, they make both types.

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[DavidCh]

You didn't say it was a dual one, you said Renogy B2B, they make both types.

Me bad

 

[bigtwin]

I don't think that's quite fair. Cable size will be sized for maximum designed load, not the power source as that is just theoretical.

Many moons ago (when MHs had rudimentary electrics) perhaps but for how long now have MH users been adding additional batteries? Entirely foreseeable these days.

I could have 100A alternator and my load might never exceed 10A for example, the alternator (or any power source for that matter) will never deliver 100A in that situation.

Indeed, but equally how many users add an additional, or multiple additional, battery(ies) so it’s entirely possible that the capability of the alternator will be taken advantage of.

I think what you are really saying is that it would be better practice to assume over the life of a van that the load may change due to upgrades etc.

Indeed, it’s not unrealistic.

In which case the original design specification has changed. Therefore it may be a good practice to overspec the cabling beyond the original design and bringing that in to line with the alternator rating "could" be useful if the future change in load design can still be delievered without changing the alternator.

Agreed.

But what are you asking here?

I’m not asking for anything but pointing out that many current designs are ill considered.

Over-engineering is not good practice, good practice is engineering the entire system to the design requirement specification.

Is it unreasonable to expect the design, to certain extent, to be (reasonably foreseeably) future proof?

All nicely charging circa 110 amps all connected up with 50mm2 multi strand Copper wire

"Wot voltage drop?"

A properly designed and spec’d system.

Ian

 

[Hoovie]

Just a comment ref B2Bs and votlage sensing ....
As has been said, lots of B2B units are activated via Voltage sensing, and that is becoming the norm for new units I would say.
Lenny HB made the comment about a problem that can occur if you have solar charging the vehicle battery. I would agree with that and extend it to actually being just as important if you ever use a mains charger to top up or do a recondition of your vehicle battery.
I have direct experience of that when I had a Redarc 40A B2B installed and I decided to use a 20A mains charger to charge my vehicle battery as the vehicle had not been used for a while....
Once the vehicle battery got up to a set voltage, the B2B kicked in. 20A into the vehicle battery. 40A B2B. End result was the vehicle battery got a lower than when I first plugged in the mains Charger! Not the desired effect

What I run now is Ablemail AMC B2B chargers which are configured to activate when a sense cable hits a certain voltage. the sense cable is a low current cable so is a true indication of the vehicle battery voltage, rather than the high current cable that will have voltage drop and so the voltage at the B2B input will not be accurate.
I run the Sense cable through a switch which connects to an ignition controlled supply (for automatic operation), a direct supply (in case I want to do control directly (troubleshooting)), or off (if I don't want the B2Bs to come on at all).
I find this setup works very well and allows the B2Bs to operate efficiently, tuned to the alternator output, and avoids them running when not appropriate.
(I actually have different B2Bs set to different voltage thresholds so if the engine is idling, the demand reduces (I think this is better for the alternator) and have selected delays on startup after threshold reached (so the alternator doesn't get a big current demand whack immediately when it starts).

 

[MisterB]

Does anyone remember the Monty Python sketches 'my brain hurts'??

I thought I had it all worked out re fitting a B2B (Sterling 30A, which I have ready to go, or buying a 60A Renogy)
I was also going to have the modification done by Apuljack on my NE237.

But now it seems as though there is an issue if I have solar connected to the vehicle battery (mine is directly connected rather than through the NE237) and then add a B2B ...

 

[Pausim]

Just a comment ref B2Bs and votlage sensing ....
As has been said, lots of B2B units are activated via Voltage sensing, and that is becoming the norm for new units I would say.

I would have thought voltage sensing was dead in the water with all new motorhomes having smart alternators. They need a B2B and voltage sensing will not work properly with smart alternators. If it doesn’t have D+ then I wouldn’t buy it.

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[nickq]

I would have thought voltage sensing was dead in the water with all new motorhomes having smart alternators. They need a B2B and voltage sensing will not work properly with smart alternators. If it doesn’t have D+ then I wouldn’t buy it.

Makes sense, I was also concerened about the solar, especially as once setting the solar regulator to lithium it will hit 14v+ which would surely trigger the B2B.
I believe there are also vibration sensors you can attach to the engine block to create your own D+ equivalent. But I imagine this is even harder to get the wire routed than D+ itself. (at least in an A-class with the letter box bonnet)

Actually the sterling B2B had it's own vibration sensor built in, but I wonder how sensitive it is. It could be good if it kicks in only when you are actually moving, this would probably address what Hoovie is working around with tick-over. Sure you might hit traffic for a while and your fridge could shut off, but probably wouldn't be a major issue unless stationary for ages, in which case stick it on gas. I wonder how it copes with the nice smooth French toll roads

 

[DavidCh]

To state the obvious the D+ is nothing special, its just 12v that is only there when the engine is running. Obvious places would be in the control unit or the 12v supply to the fridge. If you really had to you could just have a switch and remember to turn it on and off.

 

[JockandRita]

Does anyone remember the Monty Python sketches 'my brain hurts'??

I thought I had it all worked out re fitting a B2B (Sterling 30A, which I have ready to go, or buying a 60A Renogy)
I was also going to have the modification done by Apuljack on my NE237.

But now it seems as though there is an issue if I have solar connected to the vehicle battery (mine is directly connected rather than through the NE237) and then add a B2B ...

Dave, I'm with you re "my brain hurts".

I believe that my solar setup is connected directly to the batteries via Votronic MPPT regulators, (2 x), but I chose the ignition sensing D+ for my Sterling 60A B2B. It's all working fine, without depletion of one battery bank by the other.

HTH,

Jock.

 

[Lenny HB]

But I imagine this is even harder to get the wire routed than D+ itself. (at least in an A-class with the letter box bonnet)

You don't need to go anywhere near the engine to get a D+ signal, converters fit a D+ relay box as there is no way the D+ output from the alternator could supply all the items requiring a D+ trigger on a modern van.

 

[nickq]

You don't need to go anywhere near the engine to get a D+ signal, converters fit a D+ relay box as there is no way the D+ output from the alternator could supply all the items requiring a D+ trigger on a modern van.

Yes, identifying it is another issue. I looked where vanbitz suggested but the wiring colours change somewhere. At the back the D+ is all green, in the relay box there is no green at all. All documentation only talks about fuses and doesn't help.

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[funflair]

Dave, I'm with you re "my brain hurts".

I believe that my solar setup is connected directly to the batteries via Votronic MPPT regulators, (2 x), but I chose the ignition sensing D+ for my Sterling 60A B2B. It's all working fine, without depletion of one battery bank by the other.

HTH,

Jock.

Correct Jock your D+ is a proper alternator derived signal not voltage sensing.

EDIT I will add unless somebody has fiddled since I fiddled

 

[MisterB]

Dave, I'm with you re "my brain hurts".

I believe that my solar setup is connected directly to the batteries via Votronic MPPT regulators, (2 x), but I chose the ignition sensing D+ for my Sterling 60A B2B. It's all working fine, without depletion of one battery bank by the other.

HTH,

Jock.

But you had yours installed by someone who knew what they were doing, mine is being done by a right cowboy ... He is ok actually, he gets it all sorted eventually and he says he enjoys messing with things ... though his wife gets fed up with him constantly tinkering ....

 

[JockandRita]

Correct Jock your D+ is a proper alternator derived signal not voltage sensing.

EDIT I will add unless somebody has fiddled since I fiddled

IIRC, I think I extended it from the fridge/freezer connections, through into the garage to the B2B, as close to the battery banks as possible.

Cheers,

Jock.

 

[Pausim]

Yes, identifying it is another issue. I looked where vanbitz suggested but the wiring colours change somewhere. At the back the D+ is all green, in the relay box there is no green at all. All documentation only talks about fuses and doesn't help.

The standard DS300 has a simulated D+ output protected by a 3A fuse. You should be able to pick this up fairly easily.

 

[nickq]

The standard DS300 has a simulated D+ output protected by a 3A fuse. You should be able to pick this up fairly easily. View attachment 762779

From the DS300 yes easy. Getting that wire over to the lesiure battery in my van is just not worth the hastle. I tried to follow the +ve back from the lesiure battery, it went behind the water heater which requires the entire kitchen to be dismantled to get to, then vanished somewhere behind the bathroom wall which would require the entire bathroom sink/wall furniture to be dismantled. Honestly the easiest way would be just drilling throught the floor and going under the van. I honestly don't know what they were thinking when they fit the water heater, I hope I never have to take it out!

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[Lenny HB]

I honestly don't know what they were thinking when they fit the water heater, I hope I never have to take it out!

A Rapido by any chance as they appear to be masters at fitting the heater in inaccessible places & needing to dismantle half the van to get it out.

 

[nickq]

A Rapido by any chance as they appear to be masters at fitting the heater in inaccessible places & needing to dismantle half the van to get it out.

Yep, other than that it is fantastic van. We went through 4 other vans before this and it is by far the best.

 

[autorouter]

To state the obvious the D+ is nothing special, its just 12v that is only there when the engine is running. Obvious places would be in the control unit or the 12v supply to the fridge. If you really had to you could just have a switch and remember to turn it on and off.

Not only that, but also the D+ is actually not necessary. The reason for using the D+ rather than the ignition key turnon signal is related to the split charge relay. The ignition signal turns on and switches the starter motor on. If it turns on the split charge relay, there is a direct metallic connection between the batteries. The leisure battery will attempt to supply a percentage of the starter motor current, which is very high amps, and is not good for leisure batteries or the wiring. The D+ doesn't turn on until the starter motor has finished and the engine is running.

However a B2B isn't a direct metal connection, there's a one-way diode for a start, so there's no reverse current flow towards the starter battery, and that problem goes away. If it's triggered from the ignition switch then, although it's not ideal, it won't cause huge problems.

 

[Pausim]

Not only that, but also the D+ is actually not necessary. The reason for using the D+ rather than the ignition key turnon signal is related to the split charge relay. The ignition signal turns on and switches the starter motor on. If it turns on the split charge relay, there is a direct metallic connection between the batteries. The leisure battery will attempt to supply a percentage of the starter motor current, which is very high amps, and is not good for leisure batteries or the wiring. The D+ doesn't turn on until the starter motor has finished and the engine is running.

However a B2B isn't a direct metal connection, there's a one-way diode for a start, so there's no reverse current flow towards the starter battery, and that problem goes away. If it's triggered from the ignition switch then, although it's not ideal, it won't cause huge problems.

That makes sense but I would have thought that having the B2B go live and put an additional drain on the engine battery at the very time the battery is needed for engine starting is not ideal.

 

[jongood]

Not only that, but also the D+ is actually not necessary. The reason for using the D+ rather than the ignition key turnon signal is related to the split charge relay. The ignition signal turns on and switches the starter motor on. If it turns on the split charge relay, there is a direct metallic connection between the batteries. The leisure battery will attempt to supply a percentage of the starter motor current, which is very high amps, and is not good for leisure batteries or the wiring. The D+ doesn't turn on until the starter motor has finished and the engine is running.

However a B2B isn't a direct metal connection, there's a one-way diode for a start, so there's no reverse current flow towards the starter battery, and that problem goes away. If it's triggered from the ignition switch then, although it's not ideal, it won't cause huge problems.

I'm not great at this stuff but my understanding is the D+ comes off the alternator so will only click into action once the engine has actually fired. So the connection wont be there until the engine has taken the load off the starter motor anyway?

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