Lithium batteries and alternator protection.

[N6WT]

The six 6 volt lead-acid house batteries in my class A DP have gone bad. I am looking to replace them with 6 Battleborn 100Ah 12v LiFePO batteries. Eventually I will be adding solar.

I am not looking for recommendations on what batteries and components to buy, I have made up my mind so please don't try and change it.

The reason for this post is, I am reading that in class A motorhome when you switch batteries you should install a DC to DC charger to protect the alternator of the motorhome from overheating. I would like to know if anyone here has done this to their motorhome, what did you use to do it and where inline did you install it?

[CA_Traveler]

OK Apparentlly you choose to set the unit to 20A output so no need for further comment on that subject.

With 400AH batteries and 380AH usable I would definitely set the limit to the max provided there was not a alternator or wiring issue. For my MH there would have to be a very significant house DC usage before a 30A+ draw would be a concern.

So yes I would operate the unit at max at times. For me the pros of getting the battery fully charged initially or for short runs would be the deciding factor.

I respect what you choose to do and I think that I better understand your posts.

Cheers

[time2roll]

OK to delete all the search, tracking, referral and marketing codes after the "?" question mark.

https://www.amazon.com/Orion-Tr-12-30A-Isolated-Charger-Booster/dp/B07ZKG396Y/ref=sxin_15_pa_sp_sear...

[Tom_Barb]

CA Traveler wrote:
Tom/Barb From the Victron specs it does not have the ability to display amps.

mine does with blue tooth.

Click here for Link

Mod Edit: Fixed URL into clickable link to avoid skewing the browser window.

[Tom_Barb]

CA Traveler wrote:
Tom/Barb From the Victron specs it does not have the ability to display amps. Did you determine the 20A from say a battery monitor? Then the Victron could be supplying 10A to house loads plus 20A to the battery or 30A on it's output. This is how charging systems work - amps supply house loads and what is left charges the battery.

Your 30A unit is spec'd for 30A output not input. I didn't read the manuals but wondering if it can be downgraded to 20A. The voltage can be adjusted and that could reduce the amps.

At 10% efficiency your unit would draw 33A on the input at 36A for 20%. However the unit can be wired (and should be) to sense the actual battery voltage (both batteries). That means that wiring losses are a factor and the input amps could be larger drawing more input amps but IF your wiring (size and length) is per Victrons specs then wiring losses would be limited.

Just trying to see if we can get a better understanding of your system.

You can set any parameters you like, would you operate your equipment at max capacity at times?
Just because you can, should you?
when I installed my Victron equipment I was in contact with the Victron and set the parameters IAW direction.
and yes I have a AMP meter installed in the couch.

[BFL13]

CA Traveler wrote:
For Victron documents a MH is non isolated. The emergency start solenoid could still be used for starting.

OK I am confused what Victron means there. Renogy uses the MH frame as common.

Was a guy on here recently where his DC-DC installer left the OEM alternator charging and emerg start path open, which by-passed the isolation feature of the DC-DC, so he had to get that fixed.

[CA_Traveler]

For Victron documents a MH is non isolated. The emergency start solenoid could still be used for starting.

[BFL13]

CA Traveler wrote:
BFL13 For an isolated system both the + and - wires are sourced from the charger to the remote battery, no common ground. All RVs use a common ground and hence are non isolated.

The Renogy uses a common neg but only charges the house and isolates engine side from house like LFP guys want.

Means no MH emerg start

[CA_Traveler]

BFL13 For an isolated system both the + and - wires are sourced from the charger to the remote battery, no common ground. All RVs use a common ground and hence are non isolated.

[CA_Traveler]

Tom/Barb From the Victron specs it does not have the ability to display amps. Did you determine the 20A from say a battery monitor? Then the Victron could be supplying 10A to house loads plus 20A to the battery or 30A on it's output. This is how charging systems work - amps supply house loads and what is left charges the battery.

Your 30A unit is spec'd for 30A output not input. I didn't read the manuals but wondering if it can be downgraded to 20A. The voltage can be adjusted and that could reduce the amps.

At 10% efficiency your unit would draw 33A on the input at 36A for 20%. However the unit can be wired (and should be) to sense the actual battery voltage (both batteries). That means that wiring losses are a factor and the input amps could be larger drawing more input amps but IF your wiring (size and length) is per Victrons specs then wiring losses would be limited.

Just trying to see if we can get a better understanding of your system.

[BFL13]

Two days off grid for 60 AH ?
(3 hr drive at 20a)
Should make you suspect something needs checking with your monitor too.

[otrfun]

Tom/Barb wrote:

BFL13 wrote:

Tom/Barb wrote:
This is what we did, A 30amp DC to DC charger gives you the ability to charge the coach battery bank while running the coach engine.
This limits the engine alternator to 30 AMPs thus prevents overheating the engine alternator....

Do you still believe that ?
Hope the OP doesn't .

Yes.
Our equipment is operating as it should, 2 years in, set IAW Victron's settings .
So why shouldn't I believe that?

Some folks wouldn't believe, even when the proof is in front of them.

A 30a dc to dc charger producing only 20a of charge current indicates 1) a very inefficient dc to dc charger with only 66% conversion efficiency, 2) an installation experiencing excessive voltage drop due to undersized cabling or bad terminations, and/or 3) a 20a dc to dc charger that is improperly rated as a 30a charger.

Our 40a dc to charger outputs 40a of charge current with only a 43.5a draw on the alternator—-92% conversion efficiency. The manufacturer recommended 4 gauge for our run length. We used 2 gauge cabling to minimize voltage drop and maximize conversion efficiency.

[Tom_Barb]

BFL13 wrote:

Tom/Barb wrote:
This is what we did, A 30amp DC to DC charger gives you the ability to charge the coach battery bank while running the coach engine.
This limits the engine alternator to 30 AMPs thus prevents overheating the engine alternator....

Do you still believe that ?
Hope the OP doesn't .

Yes.
Our equipment is operating as it should, 2 years in, set IAW Victron's settings .
So why shouldn't I believe that?

Some folks wouldn't believe, even when the proof is in front of them.

[CA_Traveler]

In that case my 09 RV, 14 Jeep and 19 Lincoln don't have smart chargers.

My understanding is smart chargers lower the voltage to compensate for the increased car electronic load and hence less alternator load. However the batteries still have to be first charged at higher voltage. So how does that translate into a MH with 2 larger battery banks and higher loads?

[time2roll]

Tom_M wrote:
I have had my Renogy 170ah lithium battery for 2 years and have had no issues with it hooked directly to the alternator.

Any chance a measurement of the charging amps was noted? Please post if available.

[BFL13]

https://cdn.shopify.com/s/files/1/2204/8993/files/How_do_I_know_which_alternator.pdf?982824305232304...

Says the 50A Redarc has rating 50A output at 750 watts with 60A fuse for both input and output. 750/50 = 15v

see specs link here:

https://redarcelectronics.com/products/dual-input-50a-in-vehicle-dc-battery-charger