Configuring Lead Acid/Lithium with two engine alternators

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simonkirk asked Feb 22, '23

Configuring Lead Acid/Lithium with two engine alternators

Hi

I am looking to upgrade my boat service battery bank to Lithium. System is currently Lead Acid 12V, with an 80A starter battery and 3 x 115Ah service bank (345Ah), each charged by dedicated 80A and 120A engine alternators respectively (Volvo Penta D2-50).

I wish to upgrade the service batteries to 3 x Pylontech RT12100G31 Lithium - supported by Victron battery compatibility (I hope!) - and keep the starter battery as lead acid.

I am looking at using the Multiplus charger and associated monitoring kit, so would like to use Victon where possible.

I have been looking at the Orion Tr-Smart DC-DC Charger, but this demands that the charge goes through the starter battery en-route to the lithium, which would make the secondary 120Ah alternator redundant.

Does anyone have advise on the following:

How to keep the systems independent in terms of alternator charging, but also be able to fall back on the lithium house bank to start engine should the starter battery fail?
Select and configure Victron products to provide a suitable external alternator regulator and BMS capability dedicated to the Lithium
Can I combine the output of both alternators as input to the starter battery->Orion Tr-Smart DC-DC Charger,->Lithium?

Many Thanks

Simon

Lithium Battery

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ingo21 commented · Feb 23, 2023 at 12:04 PM

i have a similar system. 2x80ah lead acid starter batteries for the engine completely separate from my 24v 250ah lifepo housesystem. i run it like this since 6 years on my boat. like you mentioned the only issue could be to start the engine when the starter battery fails, this i why i got 2 starter batteries with a separator selector switch. so i can start on either one or both off the batteries. which is rather common in the boatworld.

i your case since you run both systems with 12v, if your starterbattery is empty, a simple jumper-cable from your lithium battery to your starter battery could do it too.

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Answer 1 · 2023-02-23T14:44:03Z

djsmiley answered · Feb 23, 2023 at 02:44 PM

I would check the option of a different alternator charge controller. A DCDC is only 30A, and thats going to take a while with a big battery bank.
Especially when you have a dedicated alternator for the household part its much more effective to use this to its full capacity, allowing you to charge with 100-120A.
Have a look at eg a Wakespeed WS-500. That one is also supported by Victron.
https://www.victronenergy.com/media/pg/Cerbo_GX/en/wakespeed-ws500-support.html
https://www.wakespeed.com/product/ws500-advanced-alternator-regulator/

You can add a small DCDC for the starter battery to keep that one topped up as well.

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ingo21 commented · Feb 23, 2023 at 04:43 PM

very nice alternator charge controller. bit pricey.

being able to integrate it into a victron system is very nice.

Not like the old Balmar or ProReg controllers.

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