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billaylward asked

Alternator replacement with lead acid starter and Lithium house

I am planning to replace my Volvo standard alternator (which has a built in regulator) with a Balmar model and an external regulator. My current set up is shown in the first diagram. This works, but has the disadvantage that the lithium charging is limited to the output of the DC-DC converter.

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Is there any reason why I cannot re-arrange the components to use the DC-DC converter to charge the starter battery instead (see second diagram)? My reasoning is the output of the DC-DC converter is more than adequate to replace the entry used for starting.

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Lithium Batteryalternator
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2 Answers
Stefanie (Victron Energy Staff) avatar image
Stefanie (Victron Energy Staff) answered ·

Hi @bill.aylward@mac.com

That's perfectly fine. I have a similar setup on my boat where the Balmar charges the lithium bank first and the Orion takes care of the starter battery.

Ensure that the BMS can turn off the Balmar controller (MC-614, MC-818 or WS500) in the event of a charge interruption. Here's how I did it (outdated because I changed a lot in the meantime, but the basics are still the same): https://www.sailingtakumoe.de/2020/08/03/balmar-hochleistungslichtmaschine-mit-victron-smartlithium-128-lifepo4/

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billaylward avatar image billaylward commented ·

Thanks Stefanie and I just read your article which was very helpful indeed.

I have Victron Superpacks with no acccess to the BMS, so how would you advise that I deal with a charge interruption?

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Stefanie (Victron Energy Staff) avatar image Stefanie (Victron Energy Staff) ♦♦ billaylward commented ·

Well, that changes things then. Without a charge disconnect, it could be unsafe for the alternator/regulator if the battery disconnects.

So the first option would be the safer method (your first picture) and then maybe put another (or more) Orion in parallel instead.

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billaylward avatar image billaylward Stefanie (Victron Energy Staff) ♦♦ commented ·

OK - that sounds like it might be the safest option. However, I'm just wondering whether for method 2, one of these solutions would work?

1. Power the Balmar regulator from the house battery (so it shuts down at the same time as the charge interruption)

2. Insert a protection device (like the Sterling Power Alternator Protection Unit)

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Trevor Bird avatar image
Trevor Bird answered ·

if you only have one house battery you may be concerned that the internal BMS may disconnect and cause an alternator problem. If you have a couple of internal BMS batteries in the house bank it would be pretty unusual to have all of them disconnect simultaneously. In fact provided you have the correct charging parameters set in the Balmar external regulalor it would be most unlikely for that to happen. Having said that, you may employ the Sterling protection unit which really looks electrically like a high powered zener diode. If the voltage spikes, it conducts to quench the implulse thus protecting the alternator diodes.

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billaylward avatar image billaylward commented ·
I have two house batteries (Victron Superpack 200Ah) each of which has a maximum current above which the BNS will disconnect it. Although it is yet to happen, my concern is that a current spike from the windlass could cause at least one of them to shut down, and then the current demand for the other would instantly double, leading it to shut down too.
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