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blpostma · 03-14-2022, 10:27 AM

Planning to convert from two 12-volt golf cart batteries to 200AH Lithium. Rig is 2005 Fleetwood Soutwind 32VS.
I have purchased a Progressive Dynamics PD9160ALV converter/charger to replace my WFCO. I also bought a Renogy 12V DC to DC converter so the coach alternator can charge the new batteries safely.

The connections will be made at the BCC (Battery Control Center) in the compartment above the propane tank. The BCC is an RV Custom Products CB-115 Rev. M.

I see a big potential problem. When on shore power, the BCC will automatically parallel the Lithium coach (house) batteries with the lead-acid chassis (or engine or starting) battery to keep them both charged.
The new converter charger has a big warning: do not charge lead-acid batteries with this charger!

Am I risking damage to the chassis battery?

On shore power, should I disable the charging of the chassis battery by either pulling a fuse or using the battery disconnect switch above the door?

twinboat · 03-14-2022, 11:18 AM

You simply need to disable the isolation solenoid. That's the solenoid that joins the 2 battery banks when one is being charged.

Your B to B charger will handle the chassis to house charging, so the isolation system is not needed.

You don't want the house to chassis battery charging, so disabling it will give you that. Simply remove one of the small wires going to the solenoid and it won't connect the batteries together.

DavidEM · 03-14-2022, 11:34 AM

I agree that with a lithium specific charger putting out 14.4-14.6 volts, you shouldn't let it charge your chassis battery. In fact the whole BCC is compromised with a DC to DC charger and lithium batteries. I would pull the whole BCC out and rig a bypass switch around the DC to DC charger to use when you really need to charge the chassis batteries or you need to boost the chassis batteries to start the engine.

David

twinboat · 03-14-2022, 01:15 PM

Don't gut the BCC, leave it in for resale so you can keep your lithium equipment when you trade up.

Maybe you can buy a second 10 amp B to B charger to maintain the chassis batteries. Just adjust it to a flooded battery float voltage.

blpostma · 03-14-2022, 01:21 PM

The BCC has multiple fuses for both chassis and house loads, so removing it is not an option. I don't think a 10% increase in voltage is going to bother anything in the BCC, but I will call RV Custom Products and see if they have any ideas.

This seems like it would be a common problem with Class A Ford F-53 chassis, but lots of Googling only brings up the reverse problem - charging LiFePO4 batteries with a charger/converter made for lead-acid batteries.

blpostma · 03-14-2022, 01:38 PM

Quote:

Originally Posted by twinboat

You simply need to disable the isolation solenoid. That's the solenoid that joins the 2 battery banks when one is being charged.

Your B to B charger will handle the chassis to house charging, so the isolation system is not needed.

You don't want the house to chassis battery charging, so disabling it will give you that. Simply remove one of the small wires going to the solenoid and it won't connect the batteries together.

Pulling fuse F22 will also do it.

blpostma · 03-14-2022, 05:51 PM

Quote:

Originally Posted by DavidEM

I agree that with a lithium specific charger putting out 14.4-14.6 volts, you shouldn't let it charge your chassis battery. In fact the whole BCC is compromised with a DC to DC charger and lithium batteries. I would pull the whole BCC out and rig a bypass switch around the DC to DC charger to use when you really need to charge the chassis batteries or you need to boost the chassis batteries to start the engine.

David

I'm getting more confused, not less. I spoke with a very knowledgeable friend, and he informed me that alternators regularly output 15VDC, so charging the chassis battery with the lithium converter/charger is not a problem. I guess I'll try it, and if it smokes the chassis battery, it's not too expensive to replace it. The other thing that makes me think that it's OK is that I'm sure many coaches with this BCC (or the charging function thereof) have been converted, and I can't find a single, not one, nada, nilch, post on any message board, Youtube video, or help article mentioning this as a problem -except mine. I'll post when it's done and let everyone know. If it smokes, you get one official "I told you so."

RichardE · 03-14-2022, 06:31 PM

Hang on,

Although your well informed friend wasn’t exactly wrong, the interpretation of how it applies to your case will result in a shorter life for your chassis batteries.

Yes alternators may spike above 13.9 volts when first recharging the cranking battery, but they don’t stay above 13.9 very long. The purpose of the voltage regulator in the charging system is to ensure the alternator maintains the chassis aka lead acid battery in it’s happy place at 13.9.

If you connect your chassis battery to your li ion charger which is going to charge at somewhere between 14.1 and 14.4 for hours then you will hold your chassis (lead acid) battery at the higher voltage for extended periods of time. The lead acid battery is going to boil.

twinboat · 03-14-2022, 08:45 PM

You only drive 6 to 8 hours a day. Your chassis battery is also supplying the power for chassis loads. 14.0 volts from the alternator isn't to bad.

When on shore power, it's for days, weeks and maybe months.

blpostma · 03-14-2022, 11:48 PM

Quote:

Originally Posted by RichardE

Hang on,

Although your well informed friend wasn’t exactly wrong, the interpretation of how it applies to your case will result in a shorter life for your chassis batteries.

Yes alternators may spike above 13.9 volts when first recharging the cranking battery, but they don’t stay above 13.9 very long. The purpose of the voltage regulator in the charging system is to ensure the alternator maintains the chassis aka lead acid battery in it’s happy place at 13.9.

If you connect your chassis battery to your li ion charger which is going to charge at somewhere between 14.1 and 14.4 for hours then you will hold your chassis (lead acid) battery at the higher voltage for extended periods of time. The lead acid battery is going to boil.

Thanks, I think you are correct. Thinking it through, we never have the RV on shore power more than 4 weeks at a time and that's when parked at home. If we are concerned with the chassis battery discharging, we can hook a float charger up to it, just as we do with a car we have in the garage which is rarely driven. We have never stayed at a campground for more than a week. The only time we ran down the chassis battery is when we left the headlights on. I'll disable the interconnect switch. From what I can see on the BCC block diagram, we will still be able to parallel the batteries for an emergency start with the auxiliary start switch on the dash. We also have a towed car that we can use for an emergency jump. So, no need to take a chance on boiling the chassis battery.

153stars · 03-18-2022, 10:49 AM

Also the issue is the life batteries can draw more amps than your alternator can to deliver for it heat or heat wise continuously. A 200ah Life batt might accept 1C charge Depending on BMS profile . So it could pull 200A from the alternator on its own.

vsheetz · 03-18-2022, 11:00 AM

Installing the Renogy DC2DC charger will require the BCC connection to be disabled. To charge the chassis battery when on shore power install a separate battery maintainer or consider a diversion charger such as LSL AmpLStart.

twinboat · 03-18-2022, 11:04 AM

Quote:

Originally Posted by vsheetz

Installing the Renogy DC2DC charger will require the BCC connection to be disabled. To charge the chassis battery when on shore power install a separate battery maintainer or consider a diversion charger such as LSL AmpLStart.

A diversion charger like the Amp L Start will overcharge the chassis battery.

A second 10 amp battery to battery charger will be able to be adjusted to lead acid float voltages.

BigEvi · 03-18-2022, 05:34 PM

There is a fuse in the BCC you can pull to shut off the isolation solenoid...the big one that ties the 2 battery systems together. Then your chassis battery won't charge on the lithium charger...as well your chassis battery won't drain your lithium down to its level while boondocking. Then if you need a charge on the chassis batts...put fuse back in for a few hours.

You might look into getting a better inverter/charger like the xatrex freedom...I know...not a lithium charger. But it has an AGM profile that will charge the lithiums up to 14.4/.5v at 100amps. This is what I use. My coach already had it...I left it in when i installed the 300ah lithium rather than jumping through hoops to install a lithium charger. So technically I can leave my chassis batts connected for shore power if I want...the xantrex goes into 13.9v float after it hits 14.5v. Yes I know lithiums don't need a float charge.

But...pulling the fuse on the chassis batts does extend my lithium capacity a few hours when boondocking. And when generator running allows more amps to go to charging the lithium.

Just some thoughts.