Lithium Conversion

[kennharriet]

Seriously considering switching to lithium. I have a Honda BF90D that puts out 44 amps. I understand the alternator needs to charge direct to my AGM battery. Should the dc-dc charger be rated at 20 amps (50% of the alternator output)? Then the dc-dc charger charges the lithium house batteries. I currently have 200w of solar charging the existing AGM house batteries through a 40 amp MPPT charge controller. Also in this scenario is there any advantage to the dc-dc charger being MPPT? Thanks in advance. Ken

 

[ssobol]

If you have a DC-DC charger with MPPT you can charge the battery with DC, solar, or a combination (depending on the charger, some are one or the other).

I would set this up so that the engine alternator charges the AGM. The DC-DC/MPPT charges the Li batt. Some DC-DC/MPPT chargers will also charge the engine battery once the Li batt is fully charged.

Something like this:

 

[robhwa]

I have a newer Honda 100 on a 2003 CD22. A year ago, I put in a 50A Renogy DC/DC charger with 2 100A LIFePO4 batteries and a 200A Renogy solar panel on the roof. After a Will Prowse recommendation for this combo for a van or camper, I had already put the equivalent on my 4-wheel camper with good luck. So far so good on the CD22 also. The nice thing about the combo is that the DC/DC charger integrates solar and alternator charging. After the house batteries are charged, it then keeps the starting battery charged through the solar panels, a nice touch. I put the batteries and DC/DC charger under the sink area and Wallas stove. I do worry about moisture there, but it seems to stay mostly dry there and very dry when the Wallas is on. Downside is if the combo unit fails, I guess you have nothing, but all good so far. I have heard many bad things about Renogy, particularly online, but I also set up a system in a remote yurt last year (with heated batteries) and it seems to work fine as well so far.

 

[shad]

A diagram of my current lithium setup is below. A couple of negative bus bars are omitted from the diagram.

I was originally going with the cheaper Victron 30A DC-DC charger, but Sunbeam recommended the XS model. The XS current limits are adjustable up to 50A, and it's a relatively small unit with Bluetooth. The charger seems to be working well and displays incoming and outgoing voltage/current via the app. I limit it to 15A for my older E-Tec stator that charges up to 25A'ish. The kicker charges up to 7A and has been doing fine so far.

The battery is a budget Litime 100Ah with Bluetooth. The battery also seems to be working as intended, and the Litime app voltage/current can be used to confirm the Victron app outgoing data.

A separate Victron MPPT charger could be added to the mix for solar.

 

[kennharriet]

SoBelle, A question about the diagram… #12 Accessories, it seems the loads should be wired direct to the Li house battery instead of the dc-dc charger? I’m a bit confused?

 

[freedomvango]

You TECHNICALLY need a number of things if you are going lithium

Battery, Shore Power Charger, DC to DC Charger, MPPT (If yours doesn't do it, you would typically charge the house battery instead of the engine in this case), Class T fuse for battery connection, Battery monitor with low state of charge alarm

these are kind the minimum for ABYC compliance and safety.

https://vanpartswarehouse.com/products/ ... 55e0&_ss=r
https://vanpartswarehouse.com/products/ ... 0762&_ss=r
https://vanpartswarehouse.com/products/ ... 2cc3&_ss=r
https://vanpartswarehouse.com/products/ ... 2cc3&_ss=r
https://vanpartswarehouse.com/products/ ... 87fe&_ss=r

You would reuse your existing battery charger to charge your engine battery at the dock, an wire in a second battery charger for your lithium

this is my r23 layout
Screenshot 2025-04-10 at 4.02.12 PM by Grant Wilson, on Flickr

 

[thataway]

SoBelle, A question about the diagram… #12 Accessories, it seems the loads should be wired direct to the Li house battery instead of the dc-dc charger? I’m a bit confused?

I agree with that.

 

[shad]

SoBelle, A question about the diagram… #12 Accessories, it seems the loads should be wired direct to the Li house battery instead of the dc-dc charger? I’m a bit confused?

To take a crack at an answer for SoBelle without knowing the actual unit, either way will work assuming the charger output, ACC circuit, and battery are on a common circuit. My assumption is that there are multiple "output" terminals on the unit, or two wires are connected to the same output terminal. It also could be done with one wire running to a positive bus bar.

When the charger is running, the accessories use some of the current with the remainder charging the battery. When the charger is off, the accessories use the battery.

Overall, the "#12" diagram is not much different than connecting the "ACC" circuit directly to a battery with appropriate fuses/breakers. However, you might save some wire depending on where the charger is located relative to the accessories and battery.

Ensure you use the correct wire gauge for the round-trip (pos+neg) length:

http://circuitwizard.bluesea.com

I'd include a main fuse/breaker on the ACC circuit close to the charger/battery just in case the charger goes haywire. Definitely a fuse/breaker close to the positive battery terminals.

https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

Personally I use one fuse for the charger and a 2nd fuse for the load circuit directly wired to the battery.

https://www.bluesea.com/products/2151/D ... 30_to_300A

Disclaimer: I am not a marine electrician, and this is just how my pea brain processes it.

 

[thataway]

Seriously considering switching to lithium. I have a Honda BF90D that puts out 44 amps. I understand the alternator needs to charge direct to my AGM battery. Should the dc-dc charger be rated at 20 amps (50% of the alternator output)? Then the dc-dc charger charges the lithium house batteries. . Ken

You want to limit the charge from the start battery to the DC/DC charger output to keep from over stressing the "alternator" of the Honda 90 (44 amp output). I used a Sterling DC to DC, because it was easily programable and was a 30 amp charger max. You also want to be sure there is enough current output from the engine charging system for maintenance of any other circuits (such as necessary to keep the engine running). I never allowed more than 30 amps--theoretically leaving 14 amps available for the other systems thru the DC to DC charger between the engine start battery and my 200 amp hour LiFePO4 battery bank.

I prefer to keep the solar system separate, from the engine charging system. Both can be easily monitored with bluetooth systems.

 

[thataway]

I may be "technically" over fusing the circuits--but there is a relatively huge amount of current and a short could cause a fire in very short order. Anything going into or out of the LiFePO4 battery is fused within a few inches of the battery. Same for current going from DC To DC charger off the engine--with a fuse before the wire run to the Li battery.

My solar system is much larger than we use on our boats (and semi fixed), so it is also fused on the solar and MPPT controller ends--plus to the battery bank.

I personally don't see the need for the more expensive Victron DC to DC battery charger (XS "smart" controller)--If I was running it on my RV, powered by a Mercedes Diesel and 200 amp alternator, I might consider it. It is designed to be used with a "smart" alternator regulator system. The 18 or 30 amp Victron works fine for our C Dory (depending on the "alternator" output.

 

[shad]

I personally don't see the need for the more expensive Victron DC to DC battery charger (XS "smart" controller)--If I was running it on my RV, powered by a Mercedes Diesel and 200 amp alternator, I might consider it. It is designed to be used with a "smart" alternator regulator system. The 18 or 30 amp Victron works fine for our C Dory (depending on the "alternator" output.

I initially tried an Amazon warehouse deals Victron 30A model that turned out to be a Frankenstein refurb lemon unit. I was going to replace it with the same new unit, but Sunbeam recommended the XS or an 18A. (The 30A was too much for my outboard, but I justified it thinking the dual lead acid batteries never burned up the stator, so why would a charge going through a charger?)

Benefits of the Victron XS relative to the 30A are:

1. Adjustable current limits.
2. Smaller size.
3. Less weight.
4. More efficient.
5. Runs cooler.
6. The app reports both input and output current/voltage. (The 30A model only reported input current/voltage and output voltage.)

The only con is the price.

Overall, if you're going to the expense/trouble and can stomach the price difference, I recommend the XS. Especially if installing in the space-constrained lazarette.

 

[ssobol]

SoBelle, A question about the diagram… #12 Accessories, it seems the loads should be wired direct to the Li house battery instead of the dc-dc charger? I’m a bit confused?

Item #12 is an input to the charger (from the vehicle ACC bus) to tell it that the vehicle is on. The diagram is from the Renogy website.

 

[kennharriet]

That makes sense thank you. I read where some of the dc-dc chargers sense the alternator being on eliminating the need for a wire.

 

[thataway]

I was originally going with the cheaper Victron 30A DC-DC charger, but Sunbeam recommended the XS model. The XS current limits are adjustable up to 50A, and it's a relatively small unit with Bluetooth. The charger seems to be working well and displays incoming and outgoing voltage/current via the app. I limit it to 15A for my older E-Tec stator that charges up to 25A'ish. The kicker charges up to 7A and has been doing fine so far.

The Orion 18 amp would have been a better choice over the Orion 30 for your limited DC output. I have been using an Orion 18 with my "mobile" Li battery bank in the SUV. In a boat or RV with a larger alternator, the SX would make a lot of sense.

Sunbeam--that is a name out of the past. I thought she had given up C Dory's. The last time she was active on the C Brats was about 9 years ago.

Benefits of the Victron XS relative to the 30A are:

1. Adjustable current limits.
2. Smaller size.
3. Less weight.
4. More efficient.
5. Runs cooler.
6. The app reports both input and output current/voltage. (The 30A model only reported input current/voltage and output voltage.)

The only con is the price.

Overall, if you're going to the expense/trouble and can stomach the price difference, I recommend the XS. Especially if installing in the space-constrained lazarette.

Yes all of the above is true. I do feel that current into and out of the LiFePO4 bank is very important, and I use a victron system with a read out in the cabin(I phone may not always be handy).

The difference in efficiency is about 12%--in our little boats I don't believe that makes much difference. The heat is not significant in my experience--and probably is a function of the efficiency. There should be good ventilation for any products which get warm. Size--not a lot of difference--but it could be an issue.

If you take the "Best" to the next level, then why not use Battleborn or one of several batteries which are better built and marketed to the marine trade? Yes they are about 4x the cost of the "LiTime". I have the "LiTime" in my large home system, but on the boat, I used what battery seemed ot be the best at the time. The BB are more robust, and there is an electrical engineer available to talk to if there are questions. (He also facilitated my direct contact with engineers at Victron.). Our boat batteries can take a real beating if we get into heavy seas.

 

[shad]

If you take the "Best" to the next level, then why not use Battleborn or one of several batteries which are better built and marketed to the marine trade?

After watching teardowns of the batteries by Will Prowse on Youtube and reading some recommendations from other C-Brats, the LiTime batteries seemed like a reasonable gamble. No question that the Battle Born and Victron batteries are better built and supported.

 

[ssobol]

That makes sense thank you. I read where some of the dc-dc chargers sense the alternator being on eliminating the need for a wire.

Depends on whether you have a "smart" alternator or not.

A dumb alternator is easy to detect from the bus voltage. A smart alternator has variable output depending on the load (this is to increase fuel economy). With a smart alternator, you have to "tell" the charger that it the engine is on.

 

[ssobol]

...
If you take the "Best" to the next level, then why not use Battleborn or one of several batteries which are better built and marketed to the marine trade? Yes they are about 4x the cost of the "LiTime". I have the "LiTime" in my large home system, but on the boat, I used what battery seemed ot be the best at the time. The BB are more robust, and there is an electrical engineer available to talk to if there are questions. (He also facilitated my direct contact with engineers at Victron.). Our boat batteries can take a real beating if we get into heavy seas.

Something like 98% of the lithium batteries sold are manufactured in China. The difference between a US manufactured battery and a Chinese battery may be in the assembly of the component parts and the case. I think you'd have a hard case saying that all US batteries are better than all Chinese batteries.

 

[freedomvango]

That makes sense thank you. I read where some of the dc-dc chargers sense the alternator being on eliminating the need for a wire.

Depends on whether you have a "smart" alternator or not.

A dumb alternator is easy to detect from the bus voltage. A smart alternator has variable output depending on the load (this is to increase fuel economy). With a smart alternator, you have to "tell" the charger that it the engine is on.

totally correct


there's tons of ways to do it from "old school" that people swear by,, all the way to current tech.

Do what you'd like, but more data is always better than less data. Ill pay more for knowledge of what my system is doing any day

 

[shad]

That makes sense thank you. I read where some of the dc-dc chargers sense the alternator being on eliminating the need for a wire.

The Victron Orion-Tr Smart DC-DC and XS chargers have engine auto-detection and Bluetooth. For what it's worth, engine detection and charging works fine with my old 2014 Evinrude E-Tec 90 and Tohatsu 9.8 kicker. The chargers have the option of connecting an ignition switch wire if the auto detection is not sufficient. When a 120V Victron Blue Smart IP65 Charger is connected to the lead acid battery, the DC-to-DC charger automatically turns on and can charge the lithium battery, too.

The cheaper non-Smart Victron units DO NOT have Bluetooth or engine auto-detection, so a manual switch or wiring to the ignition circuit will be required. Monitoring will require extra components.

An important distinction if evaluating the Victron ecosystem.

 

[kennharriet]

Sure appreciate all of the experienced wisdom from the group. I ended up ordering the Renogy 20amp non MPPT dc-dc charger (50% of BF90D alternator output of 44 amps). I also ordered two 100ah Renogy Core mini Li batteries, mostly because of their small size and fit in the lazerette. My planned layout is AWG 4 ga wire from the motor to an 85 ah Vmax AGM located in the port lazerette. Then 8 ga wire from the AGM through a 30 amp ANL fuse to the dc-dc charger in the starboard lazerette. From the charger through a 40 amp ANL fuse to the Li batteries also in the starboard lazerette. 200w of solar will also feed the Li batteries through a 40w MPPT charger and 50 amp ANL fuse. The house load will be fed through a 60 amp breaker to a new Blue Seas distribution panel and fuse panel. Everything is marine tinned wire and connectors. Per Bobs earlier advice the windless is on the house battery. I like he simplicity of this set-up. I removed the Yardina Combiner used in the previous system.

Does anyone see any holes in this setup? Looking forward to three months on the water starting in Skagway May 18, with our heads full of stories from Jay and Jolee. Thanks again for the discussion, Ken