DC to DC Charger for Lithiums - Sterling or Victron or ??

[Richard10002]

Some will know that I fitted a Lithium Battery bank last December and decided to charge only from solar and generator, thus avoiding the complications of charging from the alternator when the engine is running.

 

The almost failure of my 240V Sterling charger, and lack of sun, has prompted me to look at alternatives, one of which was to have a second 240V charger.

 

However, it seems that charging Lithiums from the alternator has moved on a bit, and DC to DC or Battery to Battery chargers seem to do the job.

 

As I have never seen more than about 35A from my alternator, (I think it's a 55A job), it seems that either the Victron Orion Smart 12V/12V 30A, or the Sterling 30A equivalent will do the job. I'm leaning towards the Victron for its bluetooth capability, its flexibility with settings, (and the fact that I may have reached the end of my tether with Sterling  ).

 

Are there any other brands worth considering?

 

and

 

If I bought the Sterling 12V/12V 60A version, could this increase the Amps from battery to battery, or would it just supply whatever the alternator supplies, or would it not run?

 

and

 

The Victron comes in Isolated and Non Isolated versions. The Non Isolated is for uses where both battery banks have a common negative, which I am sure I, and most of our boats, have. Is there any benefit to getting the isolated version?

 

Any other thoughts and ideas - particularly with respect to Lithiums.

 

[Jen-in-Wellies]

Have you seen this thread on another Victron piece of kit the Victron BMS 12/200? Also seems to be a way of doing this, but may only work with Victron lithium batts.

 

37 minutes ago, Richard10002 said:

The Victron comes in Isolated and Non Isolated versions. The Non Isolated is for uses where both battery banks have a common negative, which I am sure I, and most of our boats, have. Is there any benefit to getting the isolated version?

If you have a shunt for current measurement in one, or other battery bank, then the isolated version would be better I think. Otherwise, non-isolated negatives.

Jen

[Richard10002]

27 minutes ago, Jen-in-Wellies said:

Have you seen this thread on another Victron piece of kit the Victron BMS 12/200? Also seems to be a way of doing this, but may only work with Victron lithium batts.

I'm struggling to understand how this works, so am a bit wary  It also seems to have a battery control wire which may, or may not, be restricted to Victron Batteries?

 

I understand, and like, the idea of charging from battery to battery, and can visualise how I would connect it all up, so that's probably the way for me to go.

27 minutes ago, Jen-in-Wellies said:

 

If you have a shunt for current measurement in one, or other battery bank, then the isolated version would be better I think. Otherwise, non-isolated negatives.

Jen

Shunts on both banks.... and it seems that you cant be wrong with the isolated version, whereas you can with the non isolated.

[Just Robin]

I'm equally a bit confused around Lithium charging with the V BMS 12/200.

 

A lot of the issues of solar and alternator charging are exactly the same in the RV / van culture. Same problems, minus the water. But the solution offered in all the RV installs seems to focus on DC-DC B-to-B chargers. 

 

Here, and in videos around Lithium charging on boats, I see a lot more focus on building something different - adjusting or replacing the alternator regulator controllers, or paralleling banks of both SLA and Lithium as a single hybrid bank, or other solutions.  This BMS 12/200 solution (seen used in Journey with Jono vids too) seems to be Victron's newest way. But why aren't I seeing mention of it for RV uses? Only for boating uses. Maybe just hasn't broken into that market yet. 

 

In my "when I have enough money to retire" dreams I would have been planning to use DC-DC B-to-B as the way to charge Lithiums. It seems the simplest thing, as it totally isolates "13.xV Lithium charging" away from "alternators designed for 14.4V SLA". Paralleling multiple small DC-DC even allows for switching one or other charger off to give control over slow charging (on a long day's cruising or nearing the top of the charge) vs fast charging (when needing to run diesel for an hour in winter for a quick boost) 

 

The BMS 12/200 is using a fuse as a simple resistor shunt to measure current flow, and behind the scenes it is somehow adjusting the massive amount of current it is allowing the batteries to pull from the alternator.  What logic or magic is happening behind the scenes inside thay BMS 12/200 is all hidden behind the victron curtain of mystery.  It's not clear whether it is reducing charge being pushed when near to the top of capacity, or reducing charge demand while the engine is first warming up. But on the other hand, it seems to be Victron's main focus now for A-to-B Lithium charging, so I guess that's a good sign that it will replace the DC-DC converters for that purpose and hopefully get some good victron support. It's not truly A-to-B - as it still needs what they term an 'alternator protect' battery - a sacrificial SLA battery to dump load into whenever it shuts off charging - which I guess still makes it a B-to-B.  It can also handle upto 200A, which makes it suitable for large alternators quickly charging large Lithium banks - whereas DC-DC converters will cost a lot more Amp for Amp. A 50A Victron DC-DC is quite an expense compared to a 200A Victron BMS 12/200. But then, once you've committed to Victron charging, I guess you're committed to overpaying for victron batteries.  DC-DC solutions will support non-victron banks more easily.  There are opportunities to save costs on Lithiums, but perhaps saving costs in one place creates more cost/complexity in others. 

 

I would put some time into finding out more details about the BMS 12/200 before making any decisions on DC-DC converters. 

 

[nicknorman]

8 hours ago, Just Robin said:

I'm equally a bit confused around Lithium charging with the V BMS 12/200.

 

A lot of the issues of solar and alternator charging are exactly the same in the RV / van culture. Same problems, minus the water. But the solution offered in all the RV installs seems to focus on DC-DC B-to-B chargers. 

 

Here, and in videos around Lithium charging on boats, I see a lot more focus on building something different - adjusting or replacing the alternator regulator controllers, or paralleling banks of both SLA and Lithium as a single hybrid bank, or other solutions.  This BMS 12/200 solution (seen used in Journey with Jono vids too) seems to be Victron's newest way. But why aren't I seeing mention of it for RV uses? Only for boating uses. Maybe just hasn't broken into that market yet. 

 

In my "when I have enough money to retire" dreams I would have been planning to use DC-DC B-to-B as the way to charge Lithiums. It seems the simplest thing, as it totally isolates "13.xV Lithium charging" away from "alternators designed for 14.4V SLA". Paralleling multiple small DC-DC even allows for switching one or other charger off to give control over slow charging (on a long day's cruising or nearing the top of the charge) vs fast charging (when needing to run diesel for an hour in winter for a quick boost) 

 

The BMS 12/200 is using a fuse as a simple resistor shunt to measure current flow, and behind the scenes it is somehow adjusting the massive amount of current it is allowing the batteries to pull from the alternator.  What logic or magic is happening behind the scenes inside thay BMS 12/200 is all hidden behind the victron curtain of mystery.  It's not clear whether it is reducing charge being pushed when near to the top of capacity, or reducing charge demand while the engine is first warming up. But on the other hand, it seems to be Victron's main focus now for A-to-B Lithium charging, so I guess that's a good sign that it will replace the DC-DC converters for that purpose and hopefully get some good victron support. It's not truly A-to-B - as it still needs what they term an 'alternator protect' battery - a sacrificial SLA battery to dump load into whenever it shuts off charging - which I guess still makes it a B-to-B.  It can also handle upto 200A, which makes it suitable for large alternators quickly charging large Lithium banks - whereas DC-DC converters will cost a lot more Amp for Amp. A 50A Victron DC-DC is quite an expense compared to a 200A Victron BMS 12/200. But then, once you've committed to Victron charging, I guess you're committed to overpaying for victron batteries.  DC-DC solutions will support non-victron banks more easily.  There are opportunities to save costs on Lithiums, but perhaps saving costs in one place creates more cost/complexity in others. 

 

I would put some time into finding out more details about the BMS 12/200 before making any decisions on DC-DC converters. 

 

Couple of thoughts arise:

Firstly the reason why the difference between RV and boat systems is that the alternator on an RV is a complicated thing controlled by the vehicle’s ECU, for the purposes of regenerative braking etc. Not easily tampered with. Whereas the boat alternator is reminiscent of the technology fitted to vehicles on the 1970s and is thus easily hacked.

 

Secondly I suspect that whilst a B2B is a boost Buck regulator (capable off stepping up or down voltage and current) the BMS 12/200 is either straight through or step down only. Thus making it a bit simpler.

 

That said, exactly what the behaviour of the BMS is, is a mystery to me and worth investigating for sure. But IMO it is better to generate the voltage you want (via an alternator controller) than to generate the voltage you don’t want and then change it via a B2B.