Our Next Upgrade?

[thataway]

Yes, Pat, the $500 battery is plenty for your needs--you don't need that self heating battery. It appears to also have Bluetooth transmitter, which is excellent for your function.

I am not skilled at drawing circuits with CAD. You really want a pictorial, not the electrical/electronics circuit design. The Battery to Battery and DC to DC chargers are the same thing.

The 12.7 volt at rest Flooded Lead Acid battery cannot charge safely the 13.4 volt at rest LiFePO4 battery. The charging profile of the FLA battery is different than the LI battery. The battery to battery charger makes it safe both physically and electrically to charge the li battery on the boat. A single cell of a FLA battery is 2.2 volts. A single cell of LIFe battery is 3.2 volts. A whole volt difference. That does not sound like much, until you put them in series. A 12 volt battery FLA is 6 cells at about 2.2 volts . LI FE battery is 4 cells at 3.2 volts.

If you were to hook the Li battery directly to the FLA battery there would fireworks and most likely serious damage to the batteries and boat.

Picture: engine start FLA or AGM battery hooked up directly to your outboard positive and negative cables. Then off the positive terminal of the engine start is a cable with the appropriate amperage fuse going to the Battery to battery charger.

The output of that battery to battery charger is fused, and depending on the run Lengthand size of the battery to battery charger, is probably at least 10 guage, and maybe as heavy as 6 gauge. That runs thru another fuse to the LI Fe PO4 battery.

That is the engine charging circuit. You can also hook your quality battery charger to the start battery (and I would want a battery charger higher output than the Guest 10 amp which comes with the boat.). Blue Seas, ProMariner, ProNautic, Sterling, Victron, Master Volt, all make these chargers which are fan cooled, and higher output--at least 30 amp--chargers. So you can charge your LI battery thru this when on mains power. But you want to turn off the battery to battery charger when not charging from mains.

The next question is do you want the solar hooked up to the LI or LFA house batteries?

[Pat Anderson]

As I envision it, the LifePO battery will replace the FLA battery bank completely. Everything connected to the prior FLA battery bank will be connected to the LifePO battery, fused of course (most of it already is). One side of the VSR will be connected to the FLA starting battery, and the other side will go through a DC to DC charger to the LifePO battery. The solar controller, set to lithium, will be connected directly to the LifePO battery. The Guest charger will be replaced with (??) that can charge both the FLA starting battery and the LifePO battery from shore power. Does this sound feasible?

[Salmon Fisher]

Here is a link from Renogy that includes a video with a pictorial diagram.

https://renogy.com/dcc50s-12v-50a-dc-dc-on-board-battery-charger-with-mppt/


This is from an earlier discussion. Excellent, IMHO, diagram using the Renogy DC-DC equipment:

http://www.c-brats.com/viewtopic.php?t=29106&postdays=0&postorder=asc&start=30

[thataway]

[hardee]

[journey on]

Pat,

To answer some of your questions. Dr Bob has covered a lot of ground, and I'll be short. BTW, it'll be easier and cheaper if you just replace the FLA batteries. Cheaper, but not as much fun.

1. The Suzuki alternator is internally regulated for FLA batteries. Cannot be changed to a Li cycle. This means that there has to be a lead acid battery connected to the Suzuki to prevent over voltage damage.

2. A DC-DC battery charger is a fancy name for a battery charger that connects in parallel with the FLA battery. When the engine is running, it can charge the Li battery. When the engine is not running, it will draw from the FLA battery (and house charger) to keep the battery charged.

3. The batteries you have selected have a BMS, which shuts off the charge and balances the cells. Both of these are good.

4. You need to keep a FLA battery in parallel with the DC-DC charger to take the alternator current when the DC_DC charger stops charging. Also, the Li battery will NOT start the Suzuki, not enough current.

5. You need your existing house battery charger to keep the FLA battery charged. Remember, the DC-DC charger will draw from the FLA battery when the engine isn't running, i. e. when you're on shore power.

6. You didn't ask, but most DC-DC chargers have a input to activate the charger when the engine is running and producing voltage. Install a manual switch so that you can charge when the motor isn't running. Also hook up a switch for the 1/2 rate charge.

Boris

[starcrafttom]

I am sorry but after reading all this I have to ask what is the point other then less weight? Just seems like a lot of money is being spent for little gain. Yes you save weight and get a few more hours sitting doing nothing on anchor. I run the boat when we are out almost every day but even with just the two start batterys and the big ( dont remember the model right now but its used for floor waxers and wheel chairs and that sort of stuff) that runs my fridge and windlass I can still on anchor for 3 to 4 days with out a problem. I know its new and cool and if a boat or camper were weight is really a problem, its not really in a cdory 25, Then I just dont see the need for all the money that is being spent just to be cool. Some one please explain it to me. Pat already has solar panel. If my battiers start to get low and I am not running that day and hour on the kicker while on anchor is more then enough to top me off for the day. Also another reason for a single and kicker is that with a pull/electric start kicker I never have to worry about a dead battery. I just pull start the kicker and let it run while I have breakfast then start the main. Not a great practice but it works in a pinch.

[ssobol]

There is some wisdom in "If it ain't broke, don't fix it."

[colbysmith]

Tom. Exactly!

[johnr]

[bshillam]

We are limited by the number of batteries we can carry. The charge/discharge profile is greatly increased as well as the floor. One group 31 is like carrying two standard batteries because the floor is so much lower.

My Battleborns have a 10v cut off. Recommended floor is 10.5V
standard leaded battery is depending on what article you read is about 40%

That means I get to use more of the battery and don't have to worry about pulling a charge as much. It depends on how long you plan to keep your current boat too. The long game, shows LifePO batteries are a great investment for deep cycle. Specially if you are already changing out battery chargers and making other upgrades.

https://battlebornbatteries.com/wp-content/uploads/2019/01/BB10012-Data-Sheet-4-29-2022.pdf

[starcrafttom]

Thank you bill for that explanation. Not sure I agree but at least I understand what you are aiming for. As I have always said it just depends on your use.

[thataway]

Another feature of the LiFepO4 battery is that they can be charged faster than FLA batteries. You can charge at 100% of capacity, although I have limited this to 80%. This means I can use an 80 amp charger on a 100 amp hour battery. Some have advocated for 2X or even 5x. Capacity in charging rate. There are more who feel that this is not wise for the longevity of the battery.

I would not want to draw any LiFePO4 battery down as low as below 12 Volts. !2 volts is at 9% charged--or 91% discharged. !2.5 volts is 14% charged or 86% discharged. Although one can discharge to 10 volts--it is basically 99.9% discharged, and actually can do damage to the cells.

A regular FLA battery is 50% discharged at 12.2 volts. (Which is the level below which one generally does not want to take a FLA battery. This assumes voltage is read at a steady state, with no discharge or charge for at least an hour.

So, one is actually getting more power out of a LIFePO4 battery, in that the voltage is over 12 volts until is is almost fully discharged.