Lithium charging via large alternator ?

[WotEver]

3 hours ago, ditchcrawler said:

What does it do when the batteries are full?

Afaik it switches off the feed to the lithiums. Therefore it’s advisable to keep at least one LA as a dump load to protect the alternator. 

[MtB]

4 hours ago, WotEver said:

Afaik it switches off the feed to the lithiums. Therefore it’s advisable to keep at least one LA as a dump load to protect the alternator. 

 

Isn't this one of the whole points of the Victron system though? That it doesn't quite do that in order to protect your alternator? Dumps the current into some sort of ballast resistor and ramps down the load rather than switching it off in an instant.

 

Or mebbe I dreamed this....

 

 

[moiuk]

8 hours ago, ditchcrawler said:

What does it do when the batteries are full?

My understanding is that you also need a lead acid battery in the system to dump into when the 10/200 shuts off the charging to the lithium.

[Dr Bob]

7 hours ago, Mike the Boilerman said:

 

Isn't this one of the whole points of the Victron system though? That it doesn't quite do that in order to protect your alternator? Dumps the current into some sort of ballast resistor and ramps down the load rather than switching it off in an instant.

 

Or mebbe I dreamed this....

 

 

I too thought this. The commercial systems don't need a lead acid. Maybe I am also wrong. The 'hybrid' system is just a cop out to allow us DIYers to do it more cheaply.

If you are charging at 14.3V+ then you need something that will ramp down slower at the end once you get into the knee. Far too much to go wrong.

My son's hybrid BMW has been in for a new power control module. Not a good advert for the technology .........i.e. The fast charge and discharge of lithium batteries.

[Alan de Enfield]

5 minutes ago, Dr Bob said:

Not a good advert for the technology .........

Still too early on the curve for me :

 

[Dr Bob]

7 minutes ago, Alan de Enfield said:

Still too early on the curve for me :

 

I agree with you Alan......for a £5K system from Victron.

However for a DIY solution it seems so easy. I spent circa £400 on expensive control systems including auto switching and alarms but in practice I just never get that full. My £1000 Lithiums just cycle between 40% and 80% full and spending 2 or 3 days in one place is not an issue. Last summer we avoided parking under trees so we could get full use of solar. Last night we were totally shaded by trees and went down by 120ahrs. We could easily stay here longer. No drama wotsoever. I just don't bother turning things off anymore. I could have saved 20 ahrs but why? Having not to get to 100% ever is a huge step forward. 

I think it is doable now if you understand batteries and have a bit of cash to invest although the 'affordable' way I posted in another thread would let someone get in for £500. 

Of course, we won't really know the answer for quite a few years, but by then my engine will have a lot less hours on it.

 

[peterboat]

39 minutes ago, Dr Bob said:

I agree with you Alan......for a £5K system from Victron.

However for a DIY solution it seems so easy. I spent circa £400 on expensive control systems including auto switching and alarms but in practice I just never get that full. My £1000 Lithiums just cycle between 40% and 80% full and spending 2 or 3 days in one place is not an issue. Last summer we avoided parking under trees so we could get full use of solar. Last night we were totally shaded by trees and went down by 120ahrs. We could easily stay here longer. No drama wotsoever. I just don't bother turning things off anymore. I could have saved 20 ahrs but why? Having not to get to 100% ever is a huge step forward. 

I think it is doable now if you understand batteries and have a bit of cash to invest although the 'affordable' way I posted in another thread would let someone get in for £500. 

Of course, we won't really know the answer for quite a few years, but by then my engine will have a lot less hours on it.

 

I agree with you Bob I am glad that my system is pure solar with whispergen for emergency only which was very easy to put charging voltage into

[WotEver]

9 hours ago, Mike the Boilerman said:

 

Isn't this one of the whole points of the Victron system though? That it doesn't quite do that in order to protect your alternator? Dumps the current into some sort of ballast resistor and ramps down the load rather than switching it off in an instant.

 

Or mebbe I dreamed this....

That blog that was linked to last week stated that Onboard Energy had installed the mega bucks Victron system and included a dump load LA. Peter doesn’t need one because he has no alternator but others, it seems, do. 

 

I suspect that a cheapo LA battery would be much less expensive than a 1200W resistor. 

[ditchcrawler]

7 minutes ago, WotEver said:

 

 

I suspect that a cheapo LA battery would be much less expensive than a 1200W resistor. 

Immersion heater?

[peterboat]

2 minutes ago, ditchcrawler said:

Immersion heater?

Yup that's where my drive solar is going when I ain't moving works well

[MtB]

10 minutes ago, WotEver said:

That blog that was linked to last week stated that Onboard Energy had installed the mega bucks Victron system and included a dump load LA. Peter doesn’t need one because he has no alternator but others, it seems, do. 

 

I suspect that a cheapo LA battery would be much less expensive than a 1200W resistor. 

 

Curious, as I was under the impression that Victron LiFeP04s were marketed as a 'drop-in' replacement for LA batts so must have ballast resistors built in. 

 

But I admit after seeing the price, I didn't see much point in reading the technical bumph properly. 

 

[WotEver]

7 minutes ago, ditchcrawler said:

Immersion heater?

Except that would require a changeover as opposed to a simple disconnect. I suspect that the spike as the contactor operated would be quite sufficient to kill an alternator at full chat. 

 

 

Edited May 30, 2019 by WotEver
Remove a spell chucker incorrect mod

[MtB]

 

 

2 minutes ago, peterboat said:

Yup that's where my drive solar is going when I ain't moving works well

 

Peter, I think Brian meant an immersion heater as a ballast resistor to keep a load on an alternator when the lithium over-voltage control disconnects them, to save wrecking the alternator. 

 

 

[WotEver]

2 minutes ago, Mike the Boilerman said:

 

Curious, as I was under the impression that Victron LiFeP04s were marketed as a 'drop-in' replacement for LA batts so must have ballast resistors built in. 

 

But I admit after seeing the price, I didn't see much point in reading the technical bumph properly. 

 

Hey I could be wrong. I’m making an assumption based on that blog and we all know what assumptions do. 

[MtB]

1 minute ago, WotEver said:

Except that would require a changeover as opposed to a simple disconnect. I suspect that the spike as the contractor operated would be quite sufficient to kill an alternator at full chat. 

 

Yes I was wondering about how that could be arranged in a foolproof manner. The switch gear would cost way more than the LA batt!

 

 

Expanding on the point though, will a large and near instantaneous step down in alternator output current not risk damaging the alternator in a similar way to a full disconnect?

 

 

[WotEver]

Just now, Mike the Boilerman said:

 

Yes I was wondering about how that could be arranged in a foolproof manner. The switch gear would cost way more than the LA batt!

It would have to know that a disconnect was imminent then fire a 100A (or larger) contactor to parallel the heater, then disconnect the lithiums. A dump battery is much simpler. 

[MtB]

5 minutes ago, WotEver said:

It would have to know that a disconnect was imminent then fire a 100A (or larger) contactor to parallel the heater, then disconnect the lithiums. A dump battery is much simpler. 

 

Yes. And the electronics to do this 100% reliably would actually be quite difficult to design in a fail-safe way I suspect. So the dump batt is the obvious way, but getting this point across to technically illiterate buyers of 'drop-in' lithium replacements for LAs is gonna be like pushing water up hill for Victron or any other firm flogging such products.

 

I can just imagine the ensuing conversations... "Hey Mr boat electrician, I've just paid you £6k to swap my LAs for lithiums, and you've forgotten to do one of them. You trying to SWINDLE ME??" 

 

Edited May 30, 2019 by Mike the Boilerman

[Johny London]

If the Victron system is plug n play - how come Jono spent ages designing the mega elaborate system he has? That is entirely Victron equipment but I don't think it is their off the peg standard schematic/set up (if indeed they have one) and it's prolly a lot more complicated than any home brew solution.

 

Here's a thought - if charging off the alternator is such a difficult proposition, would it be worth running an inverter/charger off of it, then using that to charge the lithiums (with its nice three or 4 stage charging cycle and any protections offered by the charger) then just switching the lithiums back in to run everything once charging has finished?

 

***I thought I'd posted the above a day or so ago - the forum seems to be working oddly for me?***

[MtB]

11 minutes ago, Johny London said:

If the Victron system is plug n play - how come Jono spent ages designing the mega elaborate system he has?

 

If it isn't plug-n-play, where is all the money going? Bare cells don't cost the money Victron charge.

 

Your idea is an interesting one. Should do the trick I reckon, but you would still need a LA battery to connect the alternator and inverter to, for exactly the same reason!

[Johny London]

4 minutes ago, Mike the Boilerman said:

 

 

Your idea is an interesting one. Should do the trick I reckon, but you would still need a LA battery to connect the alternator and inverter to, for exactly the same reason!

Yes and I suppose by the time one has wired an auto switching system and the dump battery as you suggest, it just isn't simple anymore

[ditchcrawler]

I know one boat that uses a VSR to connect a Lead Acid to the Lithiums, the only problem is the voltage does drop enough to disconnect so he has a manual switch. I don't think he has forgotten yet. I don't know if this is the dump for the alternator or whether that is arranged differently. https://oleanna.co.uk/2019/02/27/last-on-the-list-25th-february/

 

[Dr Bob]

8 hours ago, Mike the Boilerman said:

 

If it isn't plug-n-play, where is all the money going? Bare cells don't cost the money Victron charge.

 

Your idea is an interesting one. Should do the trick I reckon, but you would still need a LA battery to connect the alternator and inverter to, for exactly the same reason!

With a DIY system, and a once a day look at SoC in the morning, you can totally avoid overcharging. Here is my SoC graph for the last week. I will only ever get to 95% when I want to ......ie to reset the BMV counter. I can check the SoC is reasonably acurate from the voltage. I only ever charge to 13.5v. I do worry about these systems that charge at 14.3V. If my SoC is too high at the start of the day, then I just isolate the bank.

 

 

[peterboat]

4 hours ago, Dr Bob said:

With a DIY system, and a once a day look at SoC in the morning, you can totally avoid overcharging. Here is my SoC graph for the last week. I will only ever get to 95% when I want to ......ie to reset the BMV counter. I can check the SoC is reasonably acurate from the voltage. I only ever charge to 13.5v. I do worry about these systems that charge at 14.3V. If my SoC is too high at the start of the day, then I just isolate the bank.

 

 

I agree Bob, the art to Lithiums is dont overcharge or undercharge, for a long and happy relationship with them

[Sea Dog]

14 hours ago, peterboat said:

I agree Bob, the art to Lithiums is dont overcharge or undercharge, for a long and happy relationship with them

Sound business advice too Peter!

 

[ditchcrawler]

16 hours ago, peterboat said:

I agree Bob, the art to Lithiums is dont overcharge or undercharge, for a long and happy relationship with them

And I thought one of their selling points is you can do what you like to them and they just keep going