lithium & Lead acid

[Jimbo2010]

What about a Kiss system?

charge the lithium on solar independent of the *charger or alternator

Run the lead on the charger and or alternator

*unless the charger can do lithium

[Kettlewell]

This has been discussed and described on here a million times, but the bottom line is that having multiple options for how your main house bank gets charged is advantageous for many. For example, if you cruise Maine in the summer you might go a week in the fog with limited sun, and in the off-season in New England the sun angle is so low your solar output is vastly reduced. Or, no matter where you are something goes wrong with your solar controller. And going the other way is always handy too. You want to be able to top up your starting battery with solar.

[SOLAR SUPPORT]

Originally Posted by Jimbo2010

What about a Kiss system?

charge the lithium on solar independent of the *charger or alternator

Run the lead on the charger and or alternator

*unless the charger can do lithium

If the solar capacity and the LFP battery service bank are large enough, why not? When switching from LA batteries to LFP batteries, battery capacities are generally kept large to reduce kitchen gas usage. With this strategy, you can save nearly the same amount of money you spend on batteries by not using the alternator to safely charge LFP service batteries.

If your solar energy and/or LFP battery bank is not sufficient, it is much more logical to spend the money you will save on them. Continue charging the engine battery with the alternator. You can remove the alternator's cable going to the service batteries and use it where needed. Use a simple and low capacity dcdc from LFP Service batteries that you can use to keep the engine battery constantly charged. There are very flexible, adjustable and inexpensive DCDC chargers.

The charging energy required by the LA engine battery is very low. Let's assume that a 30Hp diesel engine draws an average of 200A current from the LA battery for 5 seconds during normal operation. 200 x (1h/60min/(60/5)) = 0.28Ah The time required for the 10A capacity dcdc charger connected to your LFP battery to charge the LA battery every time you start the starter: (0.28Ah X 3600sec) / 10 = 100.8 seconds. If the engine does not start on the first try, you do not need to wait 100 seconds:-)

You may be spending time on a boat in the winter months when the sun is not enough, or you may live in latitudes where cloudy weather continues for long days even in summer. To safely charge LFP batteries with the alternator, additional installation is required to activate a DCDC charger when necessary.

[wholybee]

Originally Posted by Kettlewell

This has been discussed and described on here a million times, but the bottom line is that having multiple options for how your main house bank gets charged is advantageous for many. For example, if you cruise Maine in the summer you might go a week in the fog with limited sun, and in the off-season in New England the sun angle is so low your solar output is vastly reduced. Or, no matter where you are something goes wrong with your solar controller. And going the other way is always handy too. You want to be able to top up your starting battery with solar.

I sort of do this. I have a switch to turn charring to the LFP on/off. It is rare I need it. But when I do, I can turn it on, and monitor everything closely, turn it off before fully charged, etc.

[sailorboy1]

Originally Posted by Jimbo2010

What about a Kiss system?

charge the lithium on solar independent of the *charger or alternator

Run the lead on the charger and or alternator

*unless the charger can do lithium

And what are you going to do when it has been cloudy for a week and the wind has the boat pointed in a bad direction for solar?

I think you are only looking at it being a KISS because you are read and got caught up in the science project installations. It was pretty KISS for me to replace my acid house batteries with LFPs as all I changed were setpoint in the alternator regulator, solar, and the battery charge program