"Cheap" LiFePO4 drop-in update

[HeinSdL]

Originally Posted by rwidman

By all accounts, your setup and alternator charging is incorrect and will result in reduced performance and shortened life.

The simplest way of adding Lithium batteries to a boat and keeping an AGM or flooded cell starting battery is to have the alternator and shorepower charger hooked up solely to that AGM or flooded cell battery and to charge the lithium house bank with a lithium battery rated DC to DC charger connected from the AGM or flooded cell battery to the lithium bank. This DC to DC charger will provide the proper voltage and charging curve for the lithium batteries.

While what you have done will work, this setup will work better.

The only reason to keep an AGM starter battery between charging device and Lithium and using a DC to DC charger is to protect the alternator (in any case if the alternator is a bit simple). Also feeding the shore charger through the AGM (and presumably solar too? that would really be weird) would be a waste of available charging power and certainly not better.

[pbiJim]

Originally Posted by HeinSdL

The only reason to keep an AGM starter battery between charging device and Lithium and using a DC to DC charger is to protect the alternator (in any case if the alternator is a bit simple)....

Depending on the size of your bank, the current required to start the motor may exceed the maximum discharge rate of the lithium batteries. Some 100ah drop in lithium batteries have 100 amp BMS systems. Some have 50 amp. A lead start battery may be able to provide higher starting currents, as well as alternator protection.

[HeinSdL]

Originally Posted by pbiJim

Depending on the size of your bank, the current required to start the motor may exceed the maximum discharge rate of the lithium batteries. Some 100ah drop in lithium batteries have 100 amp BMS systems. Some have 50 amp. A lead start battery may be able to provide higher starting currents, as well as alternator protection.

Oh I agree with that, keep the AGM starter battery and use a DC/DC charger to charge the Lithium from that battery. But I would not ALSO pass eg the shore charger through the AGM (as suggested in the earlier post) as it is not necessary and adds inefficiency in the form of losses in the DC/DC charger.

[newhaul]

Originally Posted by HeinSdL

Oh I agree with that, keep the AGM starter battery and use a DC/DC charger to charge the Lithium from that battery. But I would not ALSO pass eg the shore charger through the AGM (as suggested in the earlier post) as it is not necessary and adds inefficiency in the form of losses in the DC/DC charger.

Agreed except i use FLA a 65 amp alternator and a 40 amp dc dc
But my 30 year old inverter charger is fully settable for voltage to stop charging as well as from 1 amp to 120 amp charging. Why restrict it to 40 amps.

[s/v Jedi]

The context of the boat that Lithium is installed on is important. When the house battery is for navlights, electronics some dc outlets and refrigerators then yes, a simple drop-in scenario is fine.

In that case you take out the house battery and replace it with the lithium battery and you’re done because the battery manufacturer says you’re good to go and gives you a 5-year warranty on that use case.

On the other hand, there are boats who want much, much more than that. For starters, they want to get rid of propane. They also want a big watermaker, a dive compressor and they even want to run the A/C off lithium or inverter.

For that use case, it starts with removing any chargers, inverter/chargers etc. aboard. Now comes the hard choice: 24V or 48V battery? 12V option is out because it’s crazy to invest a substantial amount of money on a system that is on a dead end road. I went for 24V because I couldn’t getall the components I wanted in 48V but this was years ago and I’m sure 48V has more options now.

So after that you have to choose inverter capacity. You want to run an induction cooktop simultaneously with a convection oven? You did when still on propane so you probably want it on electric too. This quickly puts you on the 6kVA route that I choose and show in all the reference diagrams. This is done with two inverter/chargers for redundancy.

Now comes the dilemma of estimating your power consumption… how big your solar arrays need to be and how much battery capacity. This easily sets you on a path that costs tens of thousands of dollars so much different from buying $1k of drop in batteries. Still, I’m busy proving that drop in batteries can be used for this, but no there ain’t no AGM charge profiles used for this house bank

[Pete7]

Originally Posted by HeinSdL

Oh I agree with that, keep the AGM starter battery and use a DC/DC charger to charge the Lithium from that battery. But I would not ALSO pass eg the shore charger through the AGM (as suggested in the earlier post) as it is not necessary and adds inefficiency in the form of losses in the DC/DC charger.

I will offer an alternative view, not right or wrong just different.

We still have the 40A Sterling Power shore power charger connected to the AGM engine start, as it always was. The old VSR to charge the house bank now removed when LiePO4 installed. We can use the 40A of the Shore Charger via the 30A DC>DC (actually about 27A) to charge the LFP, but what for? or at what level. The only time we would use this is during the winter and then only to replace power used for internal lights the blown air heater, hardly heavy loads.

We have an electric galley via the inverter, but if shore power is available in the winter, we will plug directly in to that rather than charge batteries and use the inverter to create 230v AC for cooking.

We could move the shore charger to the domestic bank, but it doesn't have a LFP setting being 15 years old, easier to let the DC>DC control it all. Plus we rarely use it.

Pete

[sailorboy1]

[QUOTE=sailorboy1;3841949]Just an info update:

I have now had my $306 100Ah LFP drop-in Power Queen batteries 11 months (they are cheaper now)./QUOTE]

Been over a year and the batteries are working great

[newhaul]

[QUOTE=sailorboy1;3862084]

Originally Posted by sailorboy1

Just an info update:

I have now had my $306 100Ah LFP drop-in Power Queen batteries 11 months (they are cheaper now)./QUOTE]

Been over a year and the batteries are working great

Glad to hear thanks for the update.

[akopac]

[QUOTE=sailorboy1;3862084]

Originally Posted by sailorboy1

Just an info update:

I have now had my $306 100Ah LFP drop-in Power Queen batteries 11 months (they are cheaper now)./QUOTE]

Been over a year and the batteries are working great

Been 4 years on my Firefly’s.
Never really pay attention to them.
Out of sight out, out of mind…