Lithium can really overheat your alternator at low revs unless your BMS is super-smart. Good video.

[ED O'DARAC]

Video shows alternator burning up at low revs
Worth a quick watch.....
I am intrigued by lithium batteries, but they need to be very carefully added. This video shows that Lithium batteries have a lower internal resistance so they demand as much as the alternator can give them. At low engine revs (idling to 1500 Rpm) this results in high charge rates and the alternator can burn out. At higher engine revs, the alternator should cool itself.
A really clever BMS is obviously needed.

Does anyone know which BMS systems out there allow full charge at higher engine revs but restricts it at lower revs??

#stillconcernedformyalternator

 

[Raul]

Why do you think a clever bms is needed? What would it do differently ?

 

[Lenny HB]

Main problem of alternators burning out is when people install Lithium without a B2B.

 

[NicM]

Video shows alternator burning up at low revs
Worth a quick watch.....
I am intrigued by lithium batteries, but they need to be very carefully added. This video shows that Lithium batteries have a lower internal resistance so they demand as much as the alternator can give them. At low engine revs (idling to 1500 Rpm) this results in high charge rates and the alternator can burn out. At higher engine revs, the alternator should cool itself.
A really clever BMS is obviously needed.

Does anyone know which BMS systems out there allow full charge at higher engine revs but restricts it at lower revs??

#stillconcernedformyalternator

Seen the video before, they haven’t quite got it right with the low speed have they? The ratio on an engine is 3:1 so at idle the alternator will be a lot faster than they are saying?

 

[Steve and Denise]

I have just fitted a 300ah lithium and a 30amp B2B from Ablemail the Iveco has a smart alternator and on idle it switches on and off due to lack of voltage, a slight increase in rpm it jumps up to the required voltage and delivers 30 amps constant

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[cmcardle75]

Video shows alternator burning up at low revs
Worth a quick watch.....
I am intrigued by lithium batteries, but they need to be very carefully added. This video shows that Lithium batteries have a lower internal resistance so they demand as much as the alternator can give them. At low engine revs (idling to 1500 Rpm) this results in high charge rates and the alternator can burn out. At higher engine revs, the alternator should cool itself.
A really clever BMS is obviously needed.

Does anyone know which BMS systems out there allow full charge at higher engine revs but restricts it at lower revs??

#stillconcernedformyalternator

It's not about the BMS. It's about the charger. The BMS might have a current limit, but this is likely far in excess of what the alternator needs to be limited to. A "split charge relay" charger is completely dumb and will charge at whatever rate the alternator, cabling and battery combination naturally produces. This could be really quite excessive if you have a empty and, thus, thirsty Lithium battery with thick cabling. Don't be fooled by a split charge relay's current rating. This is just how much it is rated to take. It doesn't actually limit the current to that value. It just gets hotter and might burn out if exceeded by a fair amount.

Using a smart charger (i.e. B2B) the charge current is limited to a certain value (i.e. 30A) which limits (and typically eliminates) the damage that can be done to the alternator.

 

[Jimbohorlicks]

Does a "smart " alternator prevent overheating?

 

[ED O'DARAC]

I have just fitted a 300ah lithium and a 30amp B2B from Ablemail the Iveco has a smart alternator and on idle it switches on and off due to lack of voltage, a slight increase in rpm it jumps up to the required voltage and delivers 30 amps constant

Thanks for this. It looks a good bit of British kit.
I am sure your system is excellent, and part of me is quite envious, however, please permit me two observations?

The BMS you mention is quite pricey at £220 (more than two 100w lead acid batteries). This increases the cost of changeover quite a bit.

Also, it still appears to 'throttle back' the charge to 30A maximum (ten hours driving to recharge your full battery) whereas alternators routinely offer 78-90Amps when the vehicle is driven at normal road speeds.

Aren't we trying to push two systems together, the alternator (designed to recharge lead acid batteries with higher internal resistance than lithium types) and LiFePo4 low internal resistance batteries?
Are these BMS 'Smart' enough yet?

I am sure that many adopters of Lithium batteries are totally thrilled with them, I am just cautious that this mismatch, even when papered over by an expensive BMS, is not yet optimal?

 

[autorouter]

The BMS you mention is quite pricey at £220 (more than two 100w lead acid batteries). This increases the cost of changeover quite a bit.

It's not a Battery Management System (BMS) it's a Battery-to-Battery charger (B2B). It takes whatever power it needs from the alternator, and outputs whatever the battery needs. It happens that the B2B charges the LiFePO4 battery at a fixed constant current (amps) until it reaches a preset voltage, then cuts off.

A B2B is also called a DC-DC charger or DC Booster.

To improve on a constant current B2B, you'd need a temperature sensor and/or rev sensor on the alternator, and a bit of electronics to limit the amps at low revs and/or high temperature. Not difficult, they do it for the output to the battery, but I don't know of any that have implemented it. It would probably need different settings for different models of alternator.

 

[gerry mcg]

The purpose of the B2B is to throttle / limit the alternator charging current, not to boost it.
The chemistry of lead acid batteries meant the charging current was somewhat self limiting, but the low resistance of lithium batteries means they would absorb pretty much all charge that is thrown at them.
The B2B controls the amps going to the battery without the relying on use of a BMS. (Battery management system)
The lithium batteries usually have an on board BMS, but with a B2B, the BMS is a second line to protection, rather than the primary protection
See a screenshot of my B2B (votronic vcc1212-50) throttling the amps as the battery voltage reaches the set lithium charge voltage of 14.4v, the amps supplied by the B2B to the lithium battery tail off from 50A to <5A

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[Raul]

The bms does not have a amp limiting function. It has a max operating rating. Two 100ah batteries with 100a bms inside would make it 200a thirsty battery. That’s why a B2B is needed to limit the charging amps from alternator.

 

[Steve and Denise]

Thanks for this. It looks a good bit of British kit.
I am sure your system is excellent, and part of me is quite envious, however, please permit me two observations?

The BMS you mention is quite pricey at £220 (more than two 100w lead acid batteries). This increases the cost of changeover quite a bit.

Also, it still appears to 'throttle back' the charge to 30A maximum (ten hours driving to recharge your full battery) whereas alternators routinely offer 78-90Amps when the vehicle is driven at normal road speeds.

Aren't we trying to push two systems together, the alternator (designed to recharge lead acid batteries with higher internal resistance than lithium types) and LiFePo4 low internal resistance batteries?
Are these BMS 'Smart' enough yet?

I am sure that many adopters of Lithium batteries are totally thrilled with them, I am just cautious that this mismatch, even when papered over by an expensive BMS, is not yet optimal?

As said this is more to limit the charge to within acceptable current for the cable run if I were to double up on B2B ie 60 amp I would have to increase my 16 mm sq cable, I saw this as an easy way using the exsisting wiring.
Once I have used this setup and see how I get on I may add another 30amp B2B, incidentally with no B2B 27amps charge going in with B2B 30amps charge going in I do have a smart alternator

 

[gerry mcg]

Incidentally with no B2B 27amps charge going in with B2B 30amps charge going in I do have a smart alternator

I believe a good indication as to whether you have a smart alternator (or not) is the presence (or absence) of a Shunt on the -ive terminal of the starter battery.
If you have a Shunt, you have a smart alternator (as it uses the information from the Shunt to control the alternator output.
If there is no Shunt on the negative terminal, you have a standard alternator.

If you have a smart alternator, you are almost guaranteed to have a B2B installed from the factory, but it may be of limited capacity (e.g. 30A) which is not really enough to maximise the benefits of the large lithium battery. E.g. a 60A B2B would charge the battery bank in ½ the time compared to a 30A B2B

Photo of smart alternator shunt
From https://forums.outandaboutlive.co.u...ro-6-Ducatos-and-smart-alternators-/48494/31/

 

[steveh57]

You can also double up the B2B charger as I have. 2 x Victron 12|12 30A in parallel. I have also remote switched one of them so I can control it from the drivers seat, so if I remember, I turn one off when other ancillary loads are high or crawling along for whatever the reason. It never made sense to me to invest in Lithium and not have charging mechanisms that take advantage of the battery characteristics, prolong the life of the Lithium battery, and not place undue stress on existing components.

 

[Steve and Denise]

I believe a good indication as to whether you have a smart alternator (or not) is the presence (or absence) of a Shunt on the -ive terminal of the starter battery.
If you have a Shunt, you have a smart alternator (as it uses the information from the Shunt to control the alternator output.
If there is no Shunt on the negative terminal, you have a standard alternator.

If you have a smart alternator, you are almost guaranteed to have a B2B installed from the factory, but it may be of limited capacity (e.g. 30A) which is not really enough to maximise the benefits of the large lithium battery. E.g. a 60A B2B would charge the battery bank in ½ the time compared to a 30A B2B

Photo of smart alternator shunt
From https://forums.outandaboutlive.co.u...ro-6-Ducatos-and-smart-alternators-/48494/31/
View attachment 564170

Well it’s definitely a smart alternator as I have a shunt on the negative terminal but I can’t find anything that resembles a dc2dc charger Iveco the 16mm sq wire comes from the under the bonnet + terminal and goes straight to the ds470ca at the rear of the van where the batteries are located the 16 mm sq cable is fused at 50amps each end ?

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[Lenny HB]

Well it’s definitely a smart alternator as I have a shunt on the negative terminal but I can’t find anything that resembles a dc2dc charger Iveco the 16mm sq wire comes from the under the bonnet + terminal and goes straight to the ds470ca at the rear of the van where the batteries are located the 16 mm sq cable is fused at 50amps each end ?

Sounds like your next job is fitting a B2B. With the cable running right to the back of the van you will probably need to up the cable to 35mm sq or run another 16 mm sq in parallel.

 

[ED O'DARAC]

You can also double up the B2B charger as I have. 2 x Victron 12|12 30A in parallel. I have also remote switched one of them so I can control it from the drivers seat, so if I remember, I turn one off when other ancillary loads are high or crawling along for whatever the reason. It never made sense to me to invest in Lithium and not have charging mechanisms that take advantage of the battery characteristics, prolong the life of the Lithium battery, and not place undue stress on existing components.

Excellent and illuminating. Thanks for this great tip.

 

[autorouter]

I believe a good indication as to whether you have a smart alternator (or not) is the presence (or absence) of a Shunt on the -ive terminal of the starter battery.

This is true, but some vehicles including Ducato have a latching relay on the negative terminal for battery isolation. It could easily be confused with a shunt (small black box, several wires going to it), so some care is needed.