Switching to Lithium batteries

Jrampey · 10-26-2021, 07:51 PM

I just purchased a new to me 2019 Forza 34T. Unfortunately I've discovered that the house batteries (4) are in poor condition - I checked the water levels and found all of them dry? (after buying). I have refilled with distilled water and recharged, but 8 hours of inverter idling with fridge on and they are exhausted! So it's time for Lithium batteries.

The plan is 400 to 600 amp/hours-12 volts LiFPo- 2 or 4 12 volt batteries in parallel.

I think I can tweak the charge profile of the standard inverter to match the needs of the batteries, however, I'm concerned that I'll scorch my alternator trying to charge these batteries. So, what do I do? Use a DC to DC converter 40 to 60 amps? Any recommendations on brand/specifications?

I plan to add 600 to 800 watts of solar later possibly changing the inverter at that time.

I've found myself liking the Firefly systems monitor - I'm wandering how much of its functionality I will lose as I make the changes to the electrical systems.

Who has done this before - what advise can you offer so I can navigate these tweaks with a minimum of frustration

Joe

**creativepart** · 10-27-2021, 08:18 AM

While switching to LiPo4 batteries is a great idea, in my experience 8hrs running the residential fridge on inverter is fairly good. I tested mine and got 12hrs (depleted to 50%) but I have 300w of solar, as well.

My Adventurer came with AGMs and not flooded batteries but mine are two years older than yours.

As to your question there are two standard solutions to charging via the alternator. One is a DC to DC charger connected to the alternator output to protect the alternator and better charge the batteries with a LiPo4 charge profile. The other is a battery isolation device that switches on and off to prevent damage to the alternator by limiting it’s output.

The DC to DC charger appears to be the most popular. Though some people ignore this step entirely.

TravatoJohn · 10-27-2021, 11:28 AM

Just curious. Will your stock converter/inverter accept the batteries. Also what type of BMS will you have to monitor the batteries. I believe someone could chime in and give you some information. Travato John

**creativepart** · 10-27-2021, 03:13 PM

Quote:

Originally Posted by TravatoJohn

Just curious. Will your stock converter/inverter accept the batteries. Also what type of BMS will you have to monitor the batteries. I believe someone could chime in and give you some information. Travato John

Pretty sure John, that he has a inverter/charger and he mentioned that it has a Lithium charging profile in his post. A 2019 Forza would likely have a Magnum 2000w inverter/charger and these have a LiPo4 charge profile and you can also manually set all the various charge profiles if you wish as well.

Jrampey · 10-28-2021, 06:01 PM

Yes, I have a Magnum inverter- I need to review the documents to determine if it has a preset charge profile for Lithium, but I do know it has a custom charge profile that can adjust to the parameters needed for Lithium.

**creativepart** · 10-28-2021, 06:44 PM

My Adventurer is 2-years older than yours and has a lithium charge profile on the Magnum MS1202 Inverter. I upgraded to the ME-ARC50 remote which gives a lot of additional settings. The RV came with a ME-MR 3-button remote which was pretty basic. I don't know if it had as many choices.

Clydesdale · 11-01-2021, 09:05 AM

I have a 2017 Forza and had the three button Magnum control panel. I had to buy the more deluxe one (don't remember the model number) in order to program the inverter for new Lion lithium batteries I bought at Quartzsite last winter. Even then I had to custom a profile to the settings supplied by Lion as there was no preset option.

I have been dragging my feet on any DC to DC device for charging off the alternator. I do have 1320 watts of solar so I don't rely on the alternator much. Especially in sunny Arizona.

Should I be looking to install one anyway?

**creativepart** · 11-01-2021, 09:30 AM

Quote:

Originally Posted by Clydesdale

I have been dragging my feet on any DC to DC device for charging off the alternator. I do have 1320 watts of solar so I don't rely on the alternator much. Especially in sunny Arizona.

Should I be looking to install one anyway?

I think it's agreed that it's best practice. Is it absolutely necessary? That depends on who you ask.

One point. whether you rely on your alternator or not, it will be charging your batteries if your engine is running.

While the engine is running your solar charge controller all but shuts down any solar charging. The same is true when you are on shore power or generator.

Your solar charge controller is charging only when the batteries are below 12.7v. And, anytime one of the other charging sources are applying a charge to your batteries they are putting more than 12.7v into the battery bank - and that is the voltage your solar charge controller sees. This is why when you check your battery voltage when your on shore power or generator or alternator the voltage shows between 13.6 and 14.7 volts.

It's likely that your alternator is not doing a great job of charging your expensive batteries. That is the best reason for adding the DC to DC charger. It takes the alternator's output and supplies a custom lithium specific charging profile to your batteries. And it protects the alternator from overheating, as well.

You could disconnect the alternator from your batteries so that it doesn't attempt to charge them at all. That will let your solar panels do all the charging while driving during daylight hours. Or you could do like another of out members has done and put an off/on switch between the alternator and your batteries. That way you can decide how you want to charge things.

Clydesdale · 11-01-2021, 10:14 AM

I am not sure I totally agree with you. I have monitored my solar controller and house batteries many times while driving. If it is sunny and I am driving, the solar controller is continuing to charge the batteries and not the alternator. The coach battery disconnect did not engage. I can confirm this by activating the battery switch on the dash that manually engages the solenoid and watch the charging current. The solar controller puts out enough power that the coach thinks the batteries are charged. The house batteries should not be automatically connected to the coach batteries any time the engine is running.

**creativepart** · 11-01-2021, 10:26 AM

Well, perhaps your coach is doing something different. On my 2017 Adventurer, which generally is very similar to the Forza and Journey models only on an F53 chassis, the alternator always charges both the chassis and house batteries when the engine is running.

Not to argue with you, honestly, but I guess you are saying that you are activating the momentary battery boost switch on the dash and looking at the dash charging "meter"? If that's what you are doing I don't see how this illustrates your point. Because that charging meter on your dash is monitoring the alternator output, not your battery's voltage. But maybe you are saying something different and I am misunderstanding.

BobC · 11-01-2021, 10:45 AM

Quote:

Originally Posted by Clydesdale

I have been dragging my feet on any DC to DC device for charging off the alternator. I do have 1320 watts of solar so I don't rely on the alternator much. Especially in sunny Arizona.

Should I be looking to install one anyway?

You don't have to spend a ton of money, Renogy makes three models, a 20A @ $130, a 40A @ $180 and a 60A @ $234. If you don't need to rely on the alternator much, just go for the 20A model and be confident that you're safely charging your expensive batteries.

Clydesdale · 11-01-2021, 10:47 AM

Nope, no disagreement here. Allow me explain further. This and my past coach which was a Thor, have a device such as a BIRD to disconnect the coach and house batteries especially when the engine is shutoff. It also disconnects the house batteries when they do not require charging. I have a Victron solar controller and a Victron battery monitor which are Bluetooth to my phone. So I can monitor how much charging current and where it is coming from are going into the house batteries. I have had occasions in the past on partly cloudy travel days where I was wanting my batteries to charge faster that the solar would provide. In those cases I actually wedge a dental pick into the spring loaded battery connect switch to force it to charge from the engine. It is then on my Victron monitor I can see the increase in charging current. I would have thought there would have been some kind of regulator on the alternator that would limit its power output to protect it from some kind of overload, but maybe not. Next time I drive I will pay more attention to just what the charging current is from the engine. I have 5 lithium batteries. I wanted 4 Battleborn, but Lion had such a great deal going I couldn't resist.

**creativepart** · 11-01-2021, 01:55 PM

Quote:

Originally Posted by Clydesdale

I would have thought there would have been some kind of regulator on the alternator that would limit its power output to protect it from some kind of overload, but maybe not.

Most alternators do have a kind of regulator but they are built to expect to be charging a lead acid battery. The chemistry of the LA battery is automatically limiting. When the battery is discharged there is low resistance within the battery and it can accept a large amperage from the alternator. As it gets closer and closer to fully charged the internal resistance to the flow of electrons increases to the point that the output from the alternator is reduced and reduced and reduced to just a few amps. So, it is sort of self-regulating.

That's the problem with an alternator charging Lithium batteries. LiPo4 batteries do not build resistance as they reach full charge. In fact, the resistance inside the battery is so low that the alternator can overheat trying to pour enough amps into the battery - without internal resistance the alternator can't keep up with the battery's demands for power.

It won't hurt the battery because of the BMS inside the battery. But it can destroy the alternator. Also, the charging voltage/profile of the alternator isn't ideal for LiPo4 batteries, either. And they can be routinely undercharged.

This is why the DC to DC charger is the preferred approach. The alternator connects to it, not the batteries and it applies the proper charging to the batteries AND protects the alternator from burning itself up.

Jrampey · 11-01-2021, 07:27 PM

Quote:

Originally Posted by BobC

You don't have to spend a ton of money, Renogy makes three models, a 20A @ $130, a 40A @ $180 and a 60A @ $234. If you don't need to rely on the alternator much, just go for the 20A model and be confident that you're safely charging your expensive batteries.

That’s what I needed to hear - maybe 40A is right for me.

Thanks

Adven2011w24 · 11-03-2021, 07:49 AM

I have a 145 watt alternator on my 8.1 L GM engine. I have a Renogy 60 amp DC to DC Charger with a switch on the dash to turn it on or off. I also have 680 watts of solar but use the DC to DC charger when the solar panels are obscured. The DC to DC charger has protected my alternator and allowed me to fully charge my lithium batteries, it seems like a win-win to me.