Cruisers Forum
 


Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 15-06-2021, 01:39   #1
Registered User

Join Date: Aug 2019
Posts: 102
Do I just need a DC-DC charger to charge lithium?

I have a small sailboat. Just a single lead acid starter battery and a single lead acid house battery. I was looking to replace the lead acid house battery with a lithium.

To charge the lithium, do I just a need a DC-DC charger between the starter and lithium? Or is it more complicated than that? Boat is kept in a marina on shore power.
Rockinar is offline   Reply With Quote
Old 16-06-2021, 04:00   #2
Registered User

Join Date: Nov 2014
Location: Germany
Boat: Beneteau Sense 43
Posts: 165
Re: Do I just need a DC-DC charger to charge lithium?

If you have frequent access to shore power there is no need for replacing a lead acid battery with a LiFePO4 bank, IMO. LiFePO4 really shines if you need to catch every Joule of energy your scarce charging sources deliver.

That said the same question has been posed and answered a significant number of times on this forum. May I suggest to do some reading and research in existing threads?
mbartosch is offline   Reply With Quote
Old 16-06-2021, 07:47   #3
Senior Cruiser
 
tkeithlu's Avatar

Cruisers Forum Supporter

Join Date: Feb 2012
Location: Carrabelle, Florida
Boat: Fiberglas shattering 44' steel trawler
Posts: 3,482
Re: Do I just need a DC-DC charger to charge lithium?

A lithium system will save you weight, if you need that, or supply more power and slower self-discharge than a lead acid system. Demanding to charge, expensive as hell, but wonderful in place. A mixed system part Lithium and part lead-acid just sounds like a monumental PITA. Two systems, different charging, not easy to parallel, and so forth. I think that leads to two questions that lie before your original post. First, as mbartosch says, do the advantages of Lithium outweigh the disadvantages in your situation? And, second, if so why not completely convert to Lithium?
__________________
Never let anything mechanical know that you are in a hurry.
tkeithlu is offline   Reply With Quote
Old 16-06-2021, 08:00   #4
Registered User

Join Date: Nov 2014
Location: Germany
Boat: Beneteau Sense 43
Posts: 165
Re: Do I just need a DC-DC charger to charge lithium?

Quote:
Originally Posted by tkeithlu View Post
A lithium system will save you weight, if you need that, or supply more power and slower self-discharge than a lead acid system. Demanding to charge, expensive as hell, but wonderful in place. A mixed system part Lithium and part lead-acid just sounds like a monumental PITA. Two systems, different charging, not easy to parallel, and so forth. I think that leads to two questions that lie before your original post. First, as mbartosch says, do the advantages of Lithium outweigh the disadvantages in your situation? And, second, if so why not completely convert to Lithium?
From first hand experience I can confirm that LiFePO4 house and lead acid starter is a good solution. Lead acid has its advantages for starting the diesel engine: only very little energy is needed to start the engine, the battery is immediately recharged to full afterwards. This is the perfect use case for lead acid batteries.
LiFePO4 as starter batt is not optimal in my opinion. Best for longevity is to keep it between 40 and 70 % SoC which becomes difficult over time if you are doing coulomb counting. Which effectively means you will have charge the battery fully every once in a while and discharge to 50 % soon after.
That's not convenient for a starter batt.

If I were to get rid of my lead acid starter batt I'd either completely ditch it and only use the house bank (which will be able to deliver enough current to the starter even if at 0 % nominal SoC/2.8 V cell voltage).
Or the other option would be to to do it right and replace the lead acid starter battery with a small LTO battery. The perfect starter battery, but probably overkill.
mbartosch is offline   Reply With Quote
Old 16-06-2021, 08:58   #5
Registered User

Join Date: Oct 2019
Posts: 395
Re: Do I just need a DC-DC charger to charge lithium?

I would not use the house battery as a starter battery. The two must be kept separate so that if the house if flat you can still start the engine and re charge both.
Stewie12 is offline   Reply With Quote
Old 16-06-2021, 09:00   #6
Registered User

Join Date: Jan 2020
Location: Sweden
Boat: Swan 57
Posts: 98
Re: Do I just need a DC-DC charger to charge lithium?

If you have one lead and one LiFePo4 you can use a Mastervolt Charge Mate Pro 40 to limit the output from your alternator which is very good. If you don't, you need an alternator with a 200Amp charge for a 100Ah LiFePo4 battery, or you will broil your alternator.
Hermia II is offline   Reply With Quote
Old 16-06-2021, 09:10   #7
Registered User

Join Date: Jun 2018
Posts: 37
Re: Do I just need a DC-DC charger to charge lithium?

It's never quite that simple. You'll need to think about building two isolated systems. 1) your lead acid starter battery and 2) your Lion house battery.

If you keep your shore charger it will need to be moved to the lead acid system.
Then you need to make sure your DC-DC charger does not overload your lead acid systems (Shore charger, alternator, cabling etc.).

Make a drawing and work through the details.

There are all in one charger/inverters that make this easier and more fool proof.
kirklkjb is offline   Reply With Quote
Old 16-06-2021, 10:27   #8
Registered User

Join Date: Sep 2020
Location: Im swimming in the Atlantic Ocean right now.
Boat: Approx 25 ft of blubber and muscle with big fins / natural selection- current state of evolution
Posts: 166
Re: Do I just need a DC-DC charger to charge lithium?

At the risk of straying off topic you might want to consider/looking into a Firefly Battery. I recently added one to my small sailboat and the performance has been exceptional.

They would need their own voltage, different from a lead acid so a B to B charger could be used between the two batteries. It would be the closest performance wise to a lithium that would be as close to a drop in replacement as you could get without any major modifications.
BAD ORCA is offline   Reply With Quote
Old 16-06-2021, 10:29   #9
Registered User

Join Date: Oct 2018
Location: Dallas, TX
Posts: 374
Re: Do I just need a DC-DC charger to charge lithium?

Quote:
Originally Posted by Rockinar View Post
I have a small sailboat. Just a single lead acid starter battery and a single lead acid house battery. I was looking to replace the lead acid house battery with a lithium.

To charge the lithium, do I just a need a DC-DC charger between the starter and lithium? Or is it more complicated than that? Boat is kept in a marina on shore power.
A DC to DC charger or maybe a BIM should work.

You typically need 3 alternator protections (I am assuming you meant alternator and not starter):
  1. overload - The DC to DC charger can protect against the huge charging current that a lithium battery can draw
  2. load dump - If the lithium battery's BMS disconnects, the lead acid starter battery will present enough load to prevent a regulator burnout.
  3. overheating at low speeds - This is a "maybe" depending on the current rating of the DC to DC charger. At low speeds, the alternators mechanical fan may not provide enough cooling to cover the heat generated from a decent load.
NPCampbell is offline   Reply With Quote
Old 16-06-2021, 10:48   #10
Moderator
 
Pete7's Avatar

Cruisers Forum Supporter

Join Date: Aug 2009
Location: Solent, England
Boat: Moody 31
Posts: 15,459
Images: 14
Re: Do I just need a DC-DC charger to charge lithium?

Can you confirm why you want a Lithium (LFP) rather than simply fit another flooded lead acid (FLA) battery?

We have just installed a hybrid house bank consisting of one LFP and one FLA. They play nicely together so far. We use the LFP for high current loads like the kettle, toaster and shortly induction hob, oh and the wifey wants a hair dryer.

You can't run these main voltage items off a small house bank likely to be found on a smaller yacht until recently when LFP started to become mainstream.

However, you need to be sure that you need LFP before starting down this route as set up costs are high. Also there is some reading to be done because abuse a FLA battery and they can normally be recovered if you are quick. Not so with LFP over charge or completely discharge and it could end in tears.

Be interested in why.

Pete
Pete7 is offline   Reply With Quote
Old 16-06-2021, 11:12   #11
Registered User

Join Date: Jun 2018
Posts: 37
Re: Do I just need a DC-DC charger to charge lithium?

No endorsement and I have not used this device but it may fit the bill. Precision Circuits Lithium Battery Isolation Manager (Li-BIM). It's a high current continuous connection so your alternator will need to be able to support it.
kirklkjb is offline   Reply With Quote
Old 16-06-2021, 11:58   #12
Registered User

Join Date: Jun 2018
Posts: 37
Re: Do I just need a DC-DC charger to charge lithium?

Here is a nice description with recommendations from Battleborn. https://battlebornbatteries.com/batt...ium-lead-acid/
kirklkjb is offline   Reply With Quote
Old 16-06-2021, 12:43   #13
Registered User

Join Date: Jul 2016
Location: East Coast USA
Boat: Boatless at the moment
Posts: 806
Re: Do I just need a DC-DC charger to charge lithium?

Quote:
Originally Posted by kirklkjb View Post
No endorsement and I have not used this device but it may fit the bill. Precision Circuits Lithium Battery Isolation Manager (Li-BIM). It's a high current continuous connection so your alternator will need to be able to support it.
I see no value in that product. It is essentially a diode splitter that will not charge either bank more than 80%. How they measure that is by voltage which has many serious pitfalls.
kenbo is online now   Reply With Quote
Old 16-06-2021, 12:55   #14
Registered User

Join Date: Jun 2018
Posts: 37
Re: Do I just need a DC-DC charger to charge lithium?

It is recommended by the battleborn folks. Caveat Emptor.
kirklkjb is offline   Reply With Quote
Old 16-06-2021, 13:11   #15
Registered User

Join Date: Jul 2016
Location: East Coast USA
Boat: Boatless at the moment
Posts: 806
Re: Do I just need a DC-DC charger to charge lithium?

Quote:
Originally Posted by kirklkjb View Post
It is recommended by the battleborn folks. Caveat Emptor.
That does not make it a good product. I would guess that Battleborn sees this product as easy to install and should protect their battery. But it does nothing to fully charge a lead acid start battery which is the best way to kill a lead acid and does nothing to protect a small case alternator from overheating.
kenbo is online now   Reply With Quote
Reply

Tags
charger

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Setting Charge Profiles for Lithium - Help UFO Lithium Power Systems 9 24-03-2021 02:27
Lithium Portable Lithium Battery Pack Charging zboss Electrical: Batteries, Generators & Solar 2 01-05-2020 10:33
Unable to Charge Lithium Batteries Harry Brown Lithium Power Systems 7 15-10-2019 21:00
Need help configuring Outback charger/mate/mppt to new ReLion Lithium batteries seahag Lithium Power Systems 21 18-07-2018 10:34
Lithium Ion Breakthrough - forgetful-scientists-accidentally-quadruple-lithium-ion-ba zboss Electrical: Batteries, Generators & Solar 8 22-08-2015 23:35

Advertise Here


All times are GMT -7. The time now is 19:45.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.