Cheap, Relatively, and Simple Lithium Conversion

[JOhn_R_C]

2021 FR3 30DS. It came with two flooded cell lead acid batteries. I thought they were SLAs until I saw acid weeping on top of batteries and a little corrosion on the mounting plate.

What I have in mind is replacing the lead acid batts with two, 100 A Lithium batteries with internal BMS, but no heaters. It looks like some $400 for the pair of generic batteries. I'd like to stop there and let the current solar and convertor units keep the batteries at a perhaps 80% SOC.

Batteries are only used to maintain the 12 V system when unplugged from shore power like when getting groceries at Wal Mart or driving down the road. I have a generator for boondocking, which we have done once when no accommodations were available.

I have a 200W solar panel and controller that is not switchable to Lithium, but puts out 13.8V according to the panel. There is also a 70A, 13.8V convertor feeding the 12V system.

Can I get away with this understanding it is suboptimal?

First fallback would be to change out the solar controller with something like a Renology Adventurer 30A controller to bring the batts to 100% SOC occasionally.

John C

[tomkatb]

I would cram the biggest battery set possible in there. All kinds of shapes and sizes are there.

If it were me. The SOK battery is one of the best. Heaters, battery monitor, easy to work on. Good to zero. Not much more expensive.

I suspect your set up would work. A better purchase would be a fancy new lithium battery charger to use. They also restore sleeping lithium batteries. Also the fancy one we have fixes tired wet cell batteries. Like the lawn tractor. Victron 15 amp I believe.

[Aussieguy]

My solar and 2 x 100ah batteries have no problem keeping up with the 12v demands of my camping
12v fridge + furnace + lights slides etc (NO Inverter)

update the solar based on your roof and your power consumption..
solar wont work if you have a 200w panel and consume 1000w of battery each day

best if you look at your roof to determine what size panels you can fit
the solar controller is then chosen to suit that string...



I have 2 larger residential panels because they fit better ..... 370w each (740w)
the same space would only allow 3 x 200 w panels (600w) so it was a no brainer to maximize that space , with the 2 panels and then add 50amp controller

I can add another string later (800w) if needed.

If your fridge is 120v you can already have (or can add) a small inverter into the system to give your basic needs... moderate size Inverter can allow fridge and some other 120v usage without breaking the bank.

BUT if you go this inverter route ... spend a few dollars more on battery and get a more proven Chin's or Litime battery . The cheapo budget friendly $200 100ah may not handle the higher stresses of running a inverter.

I look at solar as primary power ... if you can get it to work you can then use the generator as backup
Changes the whole camping experience.

If you want air conditioning.... shorepower or generator.
or pick camping spots based on not having to use air conditioning as much

when going with lifepo4 make sure you disable the BIM unless you are sure the alternator can handle the extra demand lifepo4 may/will place on the charging system.

EDIT
adding a bit more battery capacity like Tom suggested moving the battery is doable and worth the effort even if you have to put batteries in another compartment
you want about 3 days of capacity if possible
so if you use 100ah a day you would need 300 or 400 ah of battery

[KMP44]

Originally Posted by JOhn_R_C

Can I get away with this understanding it is suboptimal?

I would say yes - you can get away with that no problem.

Its what I did 2 years ago. Works fine. I planned to at some point upgrade the converter and add a solar charge controller that is made for charging lithium but haven't done it yet since we have not boondocked much. Works fine.

I just have to be aware of low temps late in the season and turn the converter off if its going to be below 30 degrees, but we don't camp in low temps, so not a big deal.

Swapping your charge controller would be a fairly easy upgrade, but you can get by just fine without it if you are OK not charging to the full 100%.

[IsleDog]

You absolutely 100% can do it this way and not really have any issues. I did mine last year (minus solar) and have not had any issues. the only thing i did differently than your plan is to add a small stand alone lithium charger to the mix and we dont have solar. stand alone charger can be removed easily to keep batteries properly charged over winter and converter circuit can be turned on and off at will when necessary.

CHINS batteries are pretty good, and right at your $200 each price point. they do NOT have low temp protection though, and obviously no bluetooth or heaters either.
https://www.amazon.com/LiFePO4-Batte...08FMTRYPT?th=1

[JOhn_R_C]

Thanks everyone for their insights!

I don't have any inverter plans for this rig...fridge is propane and 120V so it looks like this will work.

I thought so but wanted some confirmation before I proceed.

John C

[Larry-NC]

Originally Posted by JOhn_R_C

2021 FR3 30DS. It came with two flooded cell lead acid batteries. I thought they were SLAs until I saw acid weeping on top of batteries and a little corrosion on the mounting plate.

What I have in mind is replacing the lead acid batts with two, 100 A Lithium batteries with internal BMS, but no heaters. It looks like some $400 for the pair of generic batteries. I'd like to stop there and let the current solar and convertor units keep the batteries at a perhaps 80% SOC.

Batteries are only used to maintain the 12 V system when unplugged from shore power like when getting groceries at Wal Mart or driving down the road. I have a generator for boondocking, which we have done once when no accommodations were available.

I have a 200W solar panel and controller that is not switchable to Lithium, but puts out 13.8V according to the panel. There is also a 70A, 13.8V convertor feeding the 12V system.

Can I get away with this understanding it is suboptimal?

First fallback would be to change out the solar controller with something like a Renology Adventurer 30A controller to bring the batts to 100% SOC occasionally.

John C

Originally Posted by tomkatb

I would cram the biggest battery set possible in there. All kinds of shapes and sizes are there.

If it were me. The SOK battery is one of the best. Heaters, battery monitor, easy to work on. Good to zero. Not much more expensive.

I suspect your set up would work. A better purchase would be a fancy new lithium battery charger to use. They also restore sleeping lithium batteries. Also the fancy one we have fixes tired wet cell batteries. Like the lawn tractor. Victron 15 amp I believe.

Originally Posted by Aussieguy

My solar and 2 x 100ah batteries have no problem keeping up with the 12v demands of my camping
12v fridge + furnace + lights slides etc (NO Inverter)

update the solar based on your roof and your power consumption..
solar wont work if you have a 200w panel and consume 1000w of battery each day

best if you look at your roof to determine what size panels you can fit
the solar controller is then chosen to suit that string...



I have 2 larger residential panels because they fit better ..... 370w each (740w)
the same space would only allow 3 x 200 w panels (600w) so it was a no brainer to maximize that space , with the 2 panels and then add 50amp controller

I can add another string later (800w) if needed.

If your fridge is 120v you can already have (or can add) a small inverter into the system to give your basic needs... moderate size Inverter can allow fridge and some other 120v usage without breaking the bank.

BUT if you go this inverter route ... spend a few dollars more on battery and get a more proven Chin's or Litime battery . The cheapo budget friendly $200 100ah may not handle the higher stresses of running a inverter.

I look at solar as primary power ... if you can get it to work you can then use the generator as backup
Changes the whole camping experience.

If you want air conditioning.... shorepower or generator.
or pick camping spots based on not having to use air conditioning as much

when going with lifepo4 make sure you disable the BIM unless you are sure the alternator can handle the extra demand lifepo4 may/will place on the charging system.

EDIT
adding a bit more battery capacity like Tom suggested moving the battery is doable and worth the effort even if you have to put batteries in another compartment
you want about 3 days of capacity if possible
so if you use 100ah a day you would need 300 or 400 ah of battery

Originally Posted by KMP44

I would say yes - you can get away with that no problem.

Its what I did 2 years ago. Works fine. I planned to at some point upgrade the converter and add a solar charge controller that is made for charging lithium but haven't done it yet since we have not boondocked much. Works fine.

I just have to be aware of low temps late in the season and turn the converter off if its going to be below 30 degrees, but we don't camp in low temps, so not a big deal.

Swapping your charge controller would be a fairly easy upgrade, but you can get by just fine without it if you are OK not charging to the full 100%.

Originally Posted by IsleDog

You absolutely 100% can do it this way and not really have any issues. I did mine last year (minus solar) and have not had any issues. the only thing i did differently than your plan is to add a small stand alone lithium charger to the mix and we dont have solar. stand alone charger can be removed easily to keep batteries properly charged over winter and converter circuit can be turned on and off at will when necessary.

CHINS batteries are pretty good, and right at your $200 each price point. they do NOT have low temp protection though, and obviously no bluetooth or heaters either.
https://www.amazon.com/LiFePO4-Batte...08FMTRYPT?th=1

Umm, it seems that responders here have overlooked the fact that the OP has an FR3 30DS Class A motorhome. You can't just swap the batteries. In a motorhome, there's the Coach battery (for the RV functions) and the Chassis battery (for the automotive functions).

On shore power, both the coach and chassis batteries are charged by the converter. When driving, both the coach and chassis batteries are charged by the alternator on the engine.

A battery isolation manager (various types and names) keeps you from draining the chassis battery when boondocking, drawing from just the coach battery. If the converter is not changed and the new batteries are installed, they will not be fully charged. My guess is that the OP can get away with not changing the Battery Isolation Manager.

But the serious problem occurs when driving--especially after camping. The resistance of Lead-Acid batteries goes up as they charge, so decreasing amounts of current flow as the battery is charged. Lithium-Iron Phosphate batteries maintain low resistance as they charge--that's why they charge so fast. The alternator in a regular automotive chassis is not designed to deliver high currents for a sustained period of time and can be destroyed. One common scheme to avoid this concern is to regulate the current flow by introducing a DC-DC converter between chassis and coach.

I'm posting this so the OP isn't misled and considers the issues.

[JOhn_R_C]

Thanks for that, Larry. More food for thought.

John C

[darrellr]

Another tip - if you power cycle your converter once it drops to float charge mode (~13.2v) if might jump back up to bulk mode to get you past 80%. Rinse and repeat as needed. You can get to 100% this way. As others said, your solar may be able to get you to 100% if it has LFP profiles.

[Aussieguy]

as stated in my post .. disable the BIM .

"when going with lifepo4 make sure you disable the BIM unless you are sure the alternator can handle the extra demand lifepo4 may/will place on the charging system."

It only requires one or two wires be disconnected from the BIM..... 2 minute job!

The alternator may already be heavy duty so can handle the extra charging requirements
Before spending money.... check what you got

PLUS
alternator charging is NOT required if you improve/add solar
spending money on the solar is more productive especially if you camp in one spot for multiple days..


Emergency starting if your chassis battery goes flat... you could
a) reconnect BIM so lithium battery will attempt to charge the starting battery enough to turn over ... Disconnect BIM after starting

b) use jumper cables

If your starter battery has a big drain and will often go flat ... fix source of battery drain

OR ..... send some solar power to the starter battery using a diode or manual controlled relay to

There are also multiple choices if on shorepower each day without solar... install small battery tenders to EACH ... house and chassis systems

[Twinboat]

Don't just disconnect the BIM, replace it with a Lithium BIM and you'll still have all of your systems working and the lithium / Lead acid protections you need.

[JOhn_R_C]

Just checked the Moroney sheet on the 550 RV chassis. It's a 175A alternator.

So I just leave the system as is or find the BIM?

John C

[Larry-NC]

Originally Posted by JOhn_R_C

Just checked the Moroney sheet on the 550 RV chassis. It's a 175A alternator.

So I just leave the system as is or find the BIM?

John C

Do it right. You'll never regret it.

[Aussieguy]

How to define what is RIGHT
to me it's based on what are your camping/driving expectations

a) Driving every day?
HOT desert or lots of traffic (stop / start)
Alternator will be stressed upgrade BIM would be a option here

cool mountain driving or highway speeds with a lot of airflow to cool the alternator
could leave the existing BIM

you have to decide what works for you... changing the BIM
OR... just add a switch so you can turn it off , if you get stuck in traffic
OR... Disable it and use something else .... 40amp DC-DC / SOLAR / SHOREPOWER / GENERATOR

A dc-dc charger a 30 or 40amp one will work better than a BIM
as it also increases the charge voltage for lithium 14.2v or more...
you get much faster charging than using a LI-BIM


BTW
the newer LI - BIM is just a BIM with a timer added.
charges for X minutes then shuts off to let the alternator cool down.
you lose around 50% of your charging time
So if you only drive short distances each day batteries may never get correctly charged



----------------------------------------------------------


b) staying at same location for multiple days

If you don't drive a lot... find better alternatives to charging the battery
shore power... generator ... solar




Locating and disconnecting the BIM is fairly easy
You can install your battery and take your time to test out..... what works for YOU

[TitanMike]

Originally Posted by Aussieguy

Locating and disconnecting the BIM is fairly easy
You can install your battery and take your time to test out..... what works for YOU

I wouldn't make a blanket statement like this unless you've actually done it yourself.

Fact is that the BIM commonly used by FR that consists of a control module and Trombetta relay is not just a matter of removing these and replacing with a LiBIM.

The new item has a different shape and connection positions. One needs to be able to fabricate either bus bars or heavy gauge wire connections and still mount unit in space available.

I can say this job will be more than just easy ( because I've actually done it) and how difficult will depend on both skill of owner and how tight everything is where FR has installed BIM.

[Aussieguy]

Originally Posted by TitanMike

I wouldn't make a blanket statement like this unless you've actually done it yourself.

Fact is that the BIM commonly used by FR that consists of a control module and Trombetta relay is not just a matter of removing these and replacing with a LiBIM.

The new item has a different shape and connection positions. One needs to be able to fabricate either bus bars or heavy gauge wire connections and still mount unit in space available.

I can say this job will be more than just easy ( because I've actually done it) and how difficult will depend on both skill of owner and how tight everything is where FR has installed BIM.

But but...

I said disconnect the BIM and install battery
then you got time to test out what works...

there is no rush to buy something........ work out what you got
and what works for this particular system and for the OP's camping style

personally ...... I would not bother with alternator charging of a house bank
upgrade the solar for about the same $$$$ and get much better return on investment. you can use it when stopped!

OP needs to decide or tell us his usage ... simple 12v or power hog with Inverter
How often drives or camps out in same spot for days?
Is shorepower available all the time
All of the above and more will help determine what is best for the OP
--------------------------------------------------------
The actual BIM in nothing more than a solenoid/relay
works nearly the same as what I installed in my boat to charge the house battery...

My boat one is more simple as the brains and the relay are both in the same housing

Trombetta (brains) decides the BIM (relay) is to get power or NOT so then batteries are put into parallel

if you disconnect the control wire to the BIM the
Trombetta (brains ) probably won't even know you did,
and it will send a signal down the wire ... to nowhere!


PS addition
Probably got your definitions wrong.. Trombetta ???

the principle is same though
something makes the decision to join the battery in parallel and the solenoid/relay/BIM does the joining

disconnect the solenoid/relay/BIM from the brains until decide what is best

[JOhn_R_C]

OK, I thought this would be simple...but it's not too simple. BIM was a wrinkle I had not thought through.

My house power need is rather low. As I said fridge is 120/propane and it's my primary concern when on the road. Battery indicator is always 100%. We are on shore power 99% of the time when camped.

My thoughts are that I would disconnect the BIM to seperate the house and chsssis systems. I think this will alsp isolate the chassis battery from the convertor and allow the LFP to be partially charged by it. I'd then upgrade the solar charge controller to a LFP compatible unit as a first step.

A potential second step if I can find it is needed is to get a unit that combines DC-DC charger, solar charger, and 120V convertor for a more optimum isolated house system.

John C

[Reverse_snowbird]

Originally Posted by JOhn_R_C

A potential second step if I can find it is needed is to get a unit that combines DC-DC charger, solar charger, and 120V convertor for a more optimum isolated house system.
John C

I don't have your rig, but the dc-dc charger might be a simpler way to protect the alternator in your rig.
Keep in mind that these LiOn batteries don't give you any warning when they completely discharge, so most recommend a battery monitor. Look for one that can be charged in low temperatures.

[TitanMike]

Originally Posted by Aussieguy

But but...

I said disconnect the BIM and install battery
then you got time to test out what works...

there is no rush to buy something........ work out what you got
and what works for this particular system and for the OP's camping style

personally ...... I would not bother with alternator charging of a house bank
upgrade the solar for about the same $$$$ and get much better return on investment. you can use it when stopped!

OP needs to decide or tell us his usage ... simple 12v or power hog with Inverter
How often drives or camps out in same spot for days?
Is shorepower available all the time
All of the above and more will help determine what is best for the OP
--------------------------------------------------------
The actual BIM in nothing more than a solenoid/relay
works nearly the same as what I installed in my boat to charge the house battery...

My boat one is more simple as the brains and the relay are both in the same housing

Trombetta (brains) decides the BIM (relay) is to get power or NOT so then batteries are put into parallel

if you disconnect the control wire to the BIM the
Trombetta (brains ) probably won't even know you did,
and it will send a signal down the wire ... to nowhere!


PS addition
Probably got your definitions wrong.. Trombetta ??

the principle is same though
something makes the decision to join the battery in parallel and the solenoid/relay/BIM does the joining

disconnect the solenoid/relay/BIM from the brains until decide what is best

You certainly did get it wrong

The "Trometta" in a Precision Circuits BIM (early design) is a high current relay. It works with a separate control circuit module.

As for charging house batteries from alternator, especially in a coach where wiring is already adequate, a DC/DC charger is the way to go. Why waste available charging current when batteries could use it and a DC/DC charger is also an isolator.

It's easy for one living in a sunny climate to push solar but some of us live/travel in areas with tree cover and cloudy.

Lastly, adding solar panels also adds weight. Weight that today's RV's have more than enough of.

[Aussieguy]

Originally Posted by TitanMike

You certainly did get it wrong

The "Trometta" in a Precision Circuits BIM (early design) is a high current relay. It works with a separate control circuit module.

As for charging house batteries from alternator, especially in a coach where wiring is already adequate, a DC/DC charger is the way to go. Why waste available charging current when batteries could use it and a DC/DC charger is also an isolator.

It's easy for one living in a sunny climate to push solar but some of us live/travel in areas with tree cover and cloudy.

Lastly, adding solar panels also adds weight. Weight that today's RV's have more than enough of.

Always stated IF solar works for you.....


Tested my solar with a trip to Toledo In April ... never had a problem 3 adults not really conserving 12v , slides jacks lights PLUS the 12v fridge AND furnace

rained for 2 days in Toledo
was parked in some morning shade and the panels still produced enough power to stop the battery drain... saw ZERO discharge from battery at 8:30 am


We plan many more trips in the North ... to get out of the southern Humidity
should change my username to revrsesnowbird II

I am confident that 90% of the continental USA even up in Alaska (in summer)
people could get solar to work....
Some locations not so good but IF you are MOBILE the next one probably will
--- -----------------------------------
OP now has answered some questions and I would still say:
adding battery capacity is probably all you need if ..... 99% camping on shorepower

The 2 x 100 ah Batteries the OP wants is by all probability more than enough to get him to next campground.
Disconnect paralleling device UNTIL................. OP can decide what works for HIM.
can decide for himself if a LI BIM will fit
or maybe even upgrade alternator
or Solar
or can add a 3rd / 4th battery
or he drives in COLD climate and heat will never affect alternator



My choice is
1... disconnect parallel of the batteries
2... uprade the 200w SOLAR it will work as you are driving and when stopped



Keep the original paralleling device.... use it in emergency it won't blow up if used sparingly once in a while...
especially if no stop start driving or out in the HOT desert!
OP decides if he connects the paralleling device up install a switch to override