LiFePO4 House; AGM Engine - how to charge?

[thereefgeek]

Why not keep it simple and just dump the start battery and have one huge 500 ah bank? That’s what we did with our LiFePo install. 500 ah bank, 120 amp Victron charger/inverter, 150 amp Balmar alternator & MC614 voltage regulator, and 375 watts of solar with a Victron MPPT controller. We’re a sailboat and we can stay on the hook at least 3-4 days with out worrying about charging, and most times the solar keeps up with our daily usage. Motoring at 1800 rpm our Balmar can bring the bank back from 25% to 100% in about 2-2.5 hours. Seems to me from reading the pages in this thread that the majority of respondents know very little about boat electrical systems, let alone LiFePo battery technology.

[CatNewBee]

I wold stick to separate start batteries for the engines. You do need redundancy, even a LFP can fail.

[Dockhead]

Originally Posted by CatNewBee

I wold stick to separate start batteries for the engines. You do need redundancy, even a LFP can fail.

Yes, if you dispense with the start batt then any failure in the main power system could prevent engine starting. I guess there are always lithium booster devices, but I have always thought it was much better practice to have completely separate engine (and gen) starting systems which do not touch the main power systems in any way -- separate alternator, separate charger, everything. Being able to start the main engine could be a matter of life and death.

[CatNewBee]

And it is not only about starting an engine.
If your house bank fails you can use the start batteries as buffer to run your navionics, navigation lights and essential systems for a while, recharging by the engine.

[sdj]

You must have a separate start battery, or two, and they must be fully charged at all times. Never at any time do you question any part of your engine start system - or it gets replaced. Engine starts are a given, like breathing air.

[teaguy]

Hello,
I have recently installed lifepo4 (Battle Born) house batteries and kept my AGM start battery. First I disconnected the house batteries from the alternator, protecting the alternator from overheating and installed a Renogy DCDC charger (20 Amp). The Renogy DCDC has to be configured for the battery being charged (in my case lifepo4) but does not care what the source battery is. It works perfectly, allowing the alternator to charge the start battery only and being the source for the DCDC charger. I also disconnected the old shore power charger from the house batteries but kept it connected to the starter battery and installed a dedicated lifepo4 charger. Works well for me.

[Gregr]

Hi


Many thanks for an outstanding thread on your set up. I am looking to do something similar, although my house bank and loads are 24v. I have separate alternators for the 12v starting batteries and the 24v house bank on the engine. The 24v alternator provides 100A @ 24v, so is a useful and significant source of charging the house bank when under motor. My solar bank is much less due to limited roof space, so the alternator is needed. How does your system protect the alternator from the BMS cutoff or overuse when the bank needs charge for sustained periods?

[TaylorO]

I have a remote regulator which is programmed for the lithium batteries. Battleborn sold me a device which is supposed to protect the alternator from the batteries, but consensus with my buddy that helped me with the install was that it was not necessary. The Battleborn techs you get when you call them seem to really know their stuff, so you might check with them.
Cheers,
Taylor

[Gregr]

Hi


Thanks for that, I will contact them

[Federico993]

I am building the Lithium system which will provided by an alternator with the Balmar MC614 but I wonder what is actually the best way to charge the AGM starter battery.
There are many possibilities:
- Balmar Duo Charge
- Sterling BB1230 – 12V 30A Input to 12V Output
- Advices?

[Q Xopa]

If you went with the B2B option you could charge the Start battery from your other battery, house batt being charged by any charging source. Ie alternator, shore charger, solar, wind etc.

[Singularity]

Originally Posted by Federico993

I am building the Lithium system which will provided by an alternator with the Balmar MC614 but I wonder what is actually the best way to charge the AGM starter battery.
There are many possibilities:
- Balmar Duo Charge
- Sterling BB1230 – 12V 30A Input to 12V Output
- Advices?

Toss into the mix the Victron Orion charger. I've been thinking about getting one for this purpose. Specs describe being able to configure this unit to, as applied to your situation, "only charge the AGM from the house when the engine is running" or "old-school on/off switch to charge the AGM from your house whenever you want" (they call engine-detection over-ride).

The documentation implies charging alternator-to-start battery then bleeding the charge/start battery to the house, but I see no reason to go in that order. Otherwise, Bluetooth programmable to suit the battery chemistry of the battery receiving the charge. I'm uncertain if the BT programming allows defining a low-voltage cut-off to protect the house bank (from over-draining the house when you're not looking) but there are other non-BMS means of doing this (including Victron selling a separate discrete LVC device for $100 or so).

https://www.victronenergy.com/upload...R-DE-SV-CZ.pdf

[Federico993]

If you went with the B2B option you could charge the Start battery from your other battery, house batt being charged by any charging source. Ie alternator, shore charger, solar, wind etc.

Thanks for the answer, yes I think a DC to DC charger is the best choice. At first I will have only the alternator feeding the batteries.
What DC to DC to buy?

Quote:
Originally Posted by Federico993 View Post
I am building the Lithium system which will provided by an alternator with the Balmar MC614 but I wonder what is actually the best way to charge the AGM starter battery.
There are many possibilities:
- Balmar Duo Charge
- Sterling BB1230 – 12V 30A Input to 12V Output
- Advices?
Toss into the mix the Victron Orion charger. I've been thinking about getting one for this purpose. Specs describe being able to configure this unit to, as applied to your situation, "only charge the AGM from the house when the engine is running" or "old-school on/off switch to charge the AGM from your house whenever you want" (they call engine-detection over-ride).

The documentation implies charging alternator-to-start battery then bleeding the charge/start battery to the house, but I see no reason to go in that order. Otherwise, Bluetooth programmable to suit the battery chemistry of the battery receiving the charge. I'm uncertain if the BT programming allows defining a low-voltage cut-off to protect the house bank (from over-draining the house when you're not looking) but there are other non-BMS means of doing this (including Victron selling a separate discrete LVC device for $100 or so).

https://www.victronenergy.com/upload...R-DE-SV-CZ.pdf

Thanks for the accurate answer, I was reading about the Victron Orion TR Smart. It seems great, but I found out that it is really hot!
A lot of ppl are wondering if it is normal. You can read HERE.

And it can't be plugged to the VE network, Bluetooth signal is weak

[Singularity]

Originally Posted by Federico993

... I was reading about the Victron Orion TR Smart. It seems great, but I found out that it is really hot!
A lot of ppl are wondering if it is normal. You can read HERE.

And it can't be plugged to the VE network, Bluetooth signal is weak

Good to know.

Not having researched first-hand experience, I'm wondering if the heat issue is 'simply' related to the fact that the unit is advertised to be 89% efficient, such that heat equal to roughly 10% of the charge value is produced (e.g. 40W continuous heat to the heatsink while delivering a 400W charge to the receiving battery).

I assume that people are routinely using them in boats and have used best practices to do so safely (or at least try to).