Minimum needed to convert to lithium?

[wildebus]

Whats the total cost of that lot then fitted.

well that's the downside! (and add in cables, plus the solar panels themselves ...)

 

[barryd]

well that's the downside!

And?

 

[wildebus]

And?

every install is different and takes different time and different amounts of kit.
Victron stuff in that picture? £2,000?

 

[barryd]

every install is different and takes different time and different amounts of kit.
Victron stuff in that picture? £2,000?

So add in say £1000-£1500 for the batteries and you are looking at £3k+ fitted? More than I imagined but presumably depending on the van and its age you might not need all of it?

 

[Fisherman]

W

So add in say £1000-£1500 for the batteries and you are looking at £3k+ fitted? More than I imagined but presumably depending on the van and its age you might not need all of it?

you will get 100ah lithiums with Bluetooth BMS and heaters for £389 now Barry from Alpha less your 7.5% discount on here. I paid £525 for mine from Alpha 18 months ago but they are cheaper now. Mine are the Polarmax low temperature models. This allows them to be charged below 5c as they have heaters.

So with discount that’s £720 for 2 100ah with blutooth BMS and heaters.

 

[trevskoda]

What is it that folks require all the power, surly a loo light and main cab light is alls required to read the benno at night.

 

[GeoffL]

What is it that folks require all the power, surly a loo light and main cab light is alls required to read the benno at night.

Depends. I use 12v for telly, lights, ventilation, charging laptop, mobiles, etc. I probably take about 30Ah a day out of the system, which is something my 200W solar can replace for much of the year. However, lead/acid has a 'slopey' discharge curve and the original fluorescent lights don't work properly once the battery gets to half charge. OK, I've bought LED units but haven't got round to fitting them yet. LiFePO4 has a much flatter discharge curve and has a slightly higher voltage, so better suited to my needs. IOW, it isn't all about how much power but also about quality of that power.

 

[Fisherman]

Depends. I use 12v for telly, lights, ventilation, charging laptop, mobiles, etc. I probably take about 30Ah a day out of the system, which is something my 200W solar can replace for much of the year. However, lead/acid has a 'slopey' discharge curve and the original fluorescent lights don't work properly once the battery gets to half charge. OK, I've bought LED units but haven't got round to fitting them yet. LiFePO4 has a much flatter discharge curve and has a slightly higher voltage, so better suited to my needs. IOW, it isn't all about how much power but also about quality of that power.

Trev is still trying to get his tongue out of his cheek Geoff.
Agree totally with your post Geoff.

 

[Robmac]

IOW, it isn't all about how much power but also about quality of that power.

Took me a minute Geoff - I Often Wonder? guessed it wouldn't be Isle of Wight.

 

[Nabsim]

What is it that folks require all the power, surly a loo light and main cab light is alls required to read the benno at night.

For me it was a no brainer Trev. I bought 3 of the Bosch Powerframe battery that were supposed to be the dogs danglies 6 years ago and killed them in 12 months. That was £360 in 12 months. I bought 2 x 100Ah lifepo4 and I am still using them with no degradation. They have paid for themselves more than twice over going off my first set lol

 

[trevskoda]

For me it was a no brainer Trev. I bought 3 of the Bosch Powerframe battery that were supposed to be the dogs danglies 6 years ago and killed them in 12 months. That was £360 in 12 months. I bought 2 x 100Ah lifepo4 and I am still using them with no degradation. They have paid for themselves more than twice over going off my first set lol

Yes things move fast, years back powerframe was the dogs dangly bits, old hat now, im now working on a fusion newclear power pack.

 

[Robmac]

Yes things move fast, years back powerframe was the dogs dangly bits, old hat now, im now working on a fusion newclear power pack.

Gawd help us.

If it ain't the Russki's it's Trev!

 

[Fisherman]

Yes things move fast, years back powerframe was the dogs dangly bits, old hat now, im now working on a fusion newclear power pack.

Thank god I don’t live anywhere near you Trev.

 

[merl]

You original split-charge system on a 2001 van *may* charge the Lithium better than a newer van oddly enough as it is probably just a straight relay. But with that you run the risk of exceeding its current capability as the old Lead Batteries mainly and the cabling to a degree used will essentially have been the charge bottleneck. Once you swap lead for Lithium, it will take all it can get, so you may find you are overloading the cable and blowing the fuse repeatedly, or overstressing the vehicle alternator.

I originally had the same view about 'drop in lithium' causing higher alternator charge current than lead, I've even posted so previously but when you think about it, in theory , the reverse will happen and for the vast majority of the charge cycle (except for the first few percent) the current will be lower with lithium than lead acid.
Current = Volts ÷ Resistance.
The volts in this circuit is the voltage difference between the alternator and the battery.
The voltage at the alternator doesn't change and neither does the wiring resistance (there is a slight difference in internal resistance of the two chemistries but it pales into insignificance when compared to the wiring resistance so can basically be ignored)
So the single factor governing charge current is the battery voltage and as you know you provided me with lithium charge graph showing lithium extensively charges at a slightly higher voltage than lead acid....so the current MUST therefore be lower surely?
A little counter intuitive but it does explain the stories of drop in lithium charging very poorly and no stories of burned out relays, fuses and wiring.
Whadaya reckon?

 

[GeoffL]

I originally had the same view about 'drop in lithium' causing higher alternator charge current than lead, I've even posted so previously but when you think about it, in theory , the reverse will happen and for the vast majority of the charge cycle (except for the first few percent) the current will be lower with lithium than lead acid.
Current = Volts ÷ Resistance.
The volts in this circuit is the voltage difference between the alternator and the battery.
The voltage at the alternator doesn't change and neither does the wiring resistance (there is a slight difference in internal resistance of the two chemistries but it pales into insignificance when compared to the wiring resistance so can basically be ignored)
So the single factor governing charge current is the battery voltage and as you know you provided me with lithium charge graph showing lithium extensively charges at a slightly higher voltage than lead acid....so the current MUST therefore be lower surely?
A little counter intuitive but it does explain the stories of drop in lithium charging very poorly and no stories of burned out relays, fuses and wiring.
Whadaya reckon?

AFAICT, and working from first principles:
V=RI (Ohms Law). Thus the current, I, is proportional to the inverse of the resistance R and directly proportional to voltage V. Now the internal resistance of a typical lead/acid battery is about 10 to 30 mΩ while the internal resistance of a typical LiFePO4 battery is between 1 to 5 mΩ. So even if the voltage difference between alternator output and LFP battery terminals is only half that for lead/acid, the current will still be much higher because of the lower resistance.

 

[merl]

AFAICT, and working from first principles:
V=RI (Ohms Law). Thus the current, I, is proportional to the inverse of the resistance R and directly proportional to voltage V. Now the internal resistance of a typical lead/acid battery is about 10 to 30 mΩ while the internal resistance of a typical LiFePO4 battery is between 1 to 5 mΩ. So even if the voltage difference between alternator output and LFP battery terminals is only half that for lead/acid, the current will still be much higher because of the lower resistance.

Thing is though Geoff, it's not just the battery internal resistance that needs to be taken into consideration.
Wiring resistance (both positive and negative) in the whole of the charge circuit, that includes quite a few metres of cable, relays, circuit board tracks fuses etc, Add it all up and you're looking at way more than either of the batteries, maybe 100-200mohms depending on cable gauge and length of run.
Battery resistance will have little effect compared to wiring resistance, it's wiring that basically controls the charge current, with either lead or LFP.

 

[wildebus]

I originally had the same view about 'drop in lithium' causing higher alternator charge current than lead, I've even posted so previously but when you think about it, in theory , the reverse will happen and for the vast majority of the charge cycle (except for the first few percent) the current will be lower with lithium than lead acid.
Current = Volts ÷ Resistance.
The volts in this circuit is the voltage difference between the alternator and the battery.
The voltage at the alternator doesn't change and neither does the wiring resistance (there is a slight difference in internal resistance of the two chemistries but it pales into insignificance when compared to the wiring resistance so can basically be ignored)
So the single factor governing charge current is the battery voltage and as you know you provided me with lithium charge graph showing lithium extensively charges at a slightly higher voltage than lead acid....so the current MUST therefore be lower surely?
A little counter intuitive but it does explain the stories of drop in lithium charging very poorly and no stories of burned out relays, fuses and wiring.
Whadaya reckon?

Nah, don't agree.
You look at a graph of the current when charging lithium and you see maximum current for the duration until it is full.
You see the same graph for lead and it is quite different once lead has reached a certain level of charge (and that level is fairly low). Those graphs that are published showing this are accurate and i see the same thing for real in my van (and I can switch between lead and lithium at any time to evaluate this).

As far as having wiring as the controlling factor, no thanks.

 

[GeoffL]

Thing is though Geoff, it's not just the battery internal resistance that needs to be taken into consideration.
Wiring resistance (both positive and negative) in the whole of the charge circuit, that includes quite a few metres of cable, relays, circuit board tracks fuses etc, Add it all up and you're looking at way more than either of the batteries, maybe 100-200mohms depending on cable gauge and length of run.
Battery resistance will have little effect compared to wiring resistance, it's wiring that basically controls the charge current, with either lead or LFP.

In any series arrangement, current is limited by the device that will pass the smallest current. As an analogy, consider a water pipe with an orifice plate. Without the orifice plate, the pipe can pass a lot of water; with the orifice plate, the flow rate is restricted by the orifice plate. Now in our alternator charging system we have four components (OK, five including the chassis for earth return):

• the alternator;
• the split-charge relay;
• the wiring; and
• the battery.

The wiring is rarely the limiting factor, which means that it's either going to be the relay, the alternator or the battery. Most alternators fitted are capable of much more than they typically supply, and so are also rarely the limiting factor. Split charge relays are usually designed to offer as little resistance as possible and so are also unlikely to be the limiting factor.

This leaves the battery. Now lead/acid batteries have a relatively high 'reverse' internal resistance -- IOW (in other words - not Isle of Wight, Rob!) while the battery presents little resistance when supplying current, it has a relatively high resistance to current in the opposite direction; IOW it acts a bit like a diode! On the other hand, the resistance of a LiFePO4 battery to a charging current is much less. It still might be the limiting factor, but the current limit will be considerably higher than it is with lead/acid -- unless, that is, it has current limiting built into its BMS. Of course, you could arrange things so that the wiring is the 'orifice plate', but the voltage drop across, and hence the energy dissipated by, the wiring will be relatively large, which could lead to the wiring overheating with potentially disastrous consequence. Even if the BMS has current limiting, you have a single point of failure that could cost you your motorhome! At least, that's AFAICT!

Some might question why I posted the OP if I could work out all the above: Simply, I hadn't thought it through and this thread has prodded me in the right direction; and so my thanks to all. Secondly, even if I'd worked out all the above, people (like David) who handle this stuff professionally, might know a thing or two that I'd completely missed (e.g. is there a current limiter that can be fitted in series to allow using the alternator to supply the same order of charging current as it does to a lead/acid battery). My thanks to all.

 

[merl]

Nah, don't agree.
You look at a graph of the current when charging lithium and you see maximum current for the duration until it is full.
You see the same graph for lead and it is quite different once lead has reached a certain level of charge (and that level is fairly low). Those graphs that are published showing this are accurate and i see the same thing for real in my van (and I can switch between lead and lithium at any time to evaluate this).

As far as having wiring as the controlling factor, no thanks.

I understand what you're saying WRT using a B2B and you're right of course but I was considering what would happen with a straight swap to lithium with no modifications to the existing charge circuit, ie drop in lithium.
Yep, the current is flatter for longer with Li but the available voltage from the alternator is essentially boosted by the B2B in order to enable this. Drop in doesn't have the same advantage and your left with I=V over R and I can't see how the current can possibly go up when the voltage differential goes down.

 

[Nabsim]

The USA Sprinter site guys are using alternator charging for lifepo4 a lot more now but there isn't anything standard in the kit they use. Bigger/multiple alternators and a limit on current for first few seconds. For most over her a B2B is a much easier option I think