DC2DC charger: Before/After Argo FET

[CaptainRivet]

Hi all,

Helping a buddy installing his Lithium batteries.
He has a lead starter and Optima bowtruster and gel house, charge by alternator is split via an Victron Argo FET between the 3 banks. Lead starter will be deleted. He keeps the Gel house as this can also start the engine (hybrid gel, so new starter and backup house) and add lithium house. So the Argo FET will be connected to the gel (starter and backup house) and the Optima bowtruster battery.

To charge the LFP and limit the current a Victron DC2DC Orion Smart charger is used.
Where do I connect the DC2DC, before the Argo FET or after to the gel battery? I would connect it to the Gel. But the alternator doesn‘t see the starter gel as ArgoFet is in between, so I expect the DC2DC cannot work properly. Is this a problem…never had a setup like this?
He wanna have the DC2DC.

I told him the DC2DC is actually not needed as he has a 115A Mitzi alternator which has its own internal temp regulator, so it won‘t overheat, as it’s throttling down on its own. Directly Connected to the Argo FET as the gel house before and when the BMS is switching charge off (via a relay) the alternator will still see the ArgoFet with 2 other lead, so no problem. Main charge source is solar, alternator just has to work properly.

[lmxr]

> Where do I connect the DC2DC, before the Argo FET or after to the gel battery? I

FYI we have a slightly different setup and put the DC2DC (Victron Orion 9 12/12) on the alternator B+ output and it seems to work well. However, the DC2DC charges the lead starter and not the lithium house bank. The diode charge distributor splits to the house bank and the starter (we have a current limiting regulator on our 115 A Mitsubishi alternator).
When the BMS does not signal that the alternator should be charging, the alternator output drops to 12 V, sufficiently high to charge the starter via the DC2DC and sufficiently low to avoid much current to the house bank.

[CaptainRivet]

Originally Posted by lmxr

> Where do I connect the DC2DC, before the Argo FET or after to the gel battery? I

FYI we have a slightly different setup and put the DC2DC (Victron Orion 9 12/12) on the alternator B+ output and it seems to work well. However, the DC2DC charges the lead starter and not the lithium house bank. The diode charge distributor splits to the house bank and the starter (we have a current limiting regulator on our 115 A Mitsubishi alternator).
When the BMS does not signal that the alternator should be charging, the alternator output drops to 12 V, sufficiently high to charge the starter via the DC2DC and sufficiently low to avoid much current to the house bank.

Thank you for the answer
That sounds like an interesting solution too.
Could you please post more info on you current limiting regulator. Eg. Did you buy it, if yes where or is it DIY (somewhere an instruction how to)? How is the current limiting achieved? Do you need to modify the alternator, if yes how?

Problem with the Mitzi is if you disable the internal regulator and convert to external regulator you also loose it’s Temperatur sensing which is a) internal (much better then an externally mounted sensor) and b)on the conservative side and really protects it well and c) if you have a newer Volvo engine the D+ Connection is lost too which creates other problems eg you don‘t get Startup current via D+ and if alternator is new it won‘t start producing current.

[lmxr]

Originally Posted by CaptainRivet

Thank you for the answer
That sounds like an interesting solution too.
Could you please post more info on you current limiting regulator. Eg. Did you buy it, if yes where or is it DIY (somewhere an instruction how to)?

DIY based on the VSR project (what later became the WS 500).

Originally Posted by CaptainRivet

How is the current limiting achieved?

The regulator adjust the field voltage to maximize output current while respecting upper values for temperature, voltage and current. Output current is measured using a shunt immediately after the B+. Temperature sensing is done using two temperature probes, one on the front and one on the rear. The front one tends to be the hottest and is close to the actual stator wire temperature (about 5 °C difference). Current is also limited to only slightly above maximum sustained current, this leads to lower temperature differences accros the alternator.

Originally Posted by CaptainRivet

Do you need to modify the alternator, if yes how?

Yes. I modified it by isolating the F- brush wire from the brush contact (only had to slide out the black plastic cover, I did not open the casing). Internal regulator, diodes etc. were all left in place.

Originally Posted by CaptainRivet

Problem with the Mitzi is if you disable the internal regulator and convert to external regulator you also loose it’s Temperatur sensing which is a) internal (much better then an externally mounted sensor) and b)on the conservative side and really protects it well and c) if you have a newer Volvo engine the D+ Connection is lost too which creates other problems eg you don‘t get Startup current via D+ and if alternator is new it won‘t start producing current.

a) I've not had the opportunity to bench test and to evaluate in-depth the internal regulator's temperature sensing and reduction strategies. What I do know from my limited tests is that the regulator temperature can be considerably lower (I measured > 20 °C using a thermocouple) than the stator coil. I guess because the air first passes the regulator and only thereafter the casing close to the stator coils. So I've my doubts about how it can deliver good overheating protection without (?) a good measurement of the stator temperature.

b) I've my doubts about this, similar to noted above.

c) We kept the D+ connection. I think the alternator doesn't start with it disconnected, not sure though.

[CaptainRivet]

@lmxr: do you have a Plan, Description, how to of your DIY regulator please?
Interesting you get to the field wire without opening it up. So interrupting this wire via a relay would shut the alternator off via BMS?

To b) yes it’s not mounted on stator but it’s inside the case where the airflow is given, so from where it measures they can well adapt to the real internal temps. Eric from nordkyn Design told me it’s very conservative and he really tested this alternator when he was developing their VSC200 Modul for the Mitzi 115A. He also sent me the datasheet.

[lmxr]

Originally Posted by CaptainRivet

@lmxr: do you have a Plan, Description, how to of your DIY regulator please?

The circuit was based on the open-source VSR Alternator Regulator (VSR Alternator Regulator). The site has links to the schematics and firmware. There's a group discussing the development of the open-source VSR: https://groups.google.com/g/smart-alt.

Originally Posted by CaptainRivet

Interesting you get to the field wire without opening it up. So interrupting this wire via a relay would shut the alternator off via BMS?

Have not tried this but ought to work indeed.