Overland Explorer Expedition Cabin on 2020 Ford F350

RAM5500 CAMPERTHING

OG Portal Member #183
Its some of OverlandEx's magic sauce. As I understand, an automatic relay directs the alternator's output to the house batts once the truck batts are fully charged. The same system also charges the truck from shore or solar power once the house batts are full.
Id suggest maybe looking into exactly what it is a little more.

They have DCDC chargers now that will charge at 120amps at idle, which would replenish most battery banks fairly quickly.

It would save a lot of $, SPACE, and hassle, just recharging the batteries by idling the truck than running a generator and having another motorized gizmo to maintain.

that’s my .02
 

Trail Talk

Active member
It would save a lot of $, SPACE, and hassle, just recharging the batteries by idling the truck than running a generator and having another motorized gizmo to maintain.
Good points. I am a complete newbie when it comes to electrical, but eager to learn from other's experience. Our rig has dual alternators rated at 397 amps combined. Current is first directed to the truck's two batteries; an automatic relay switches to the house batts once it reads full voltage. I don't know the charge rate; is it governed by our Xantrex inverter/charger? If so, it would be 80 A.

Edit: just read a real world test on recharging AGMs from 50% to 100% SOC at the safe recommended rate of .2C (20%) and it took over 5 1/2 hours! My head is spinning!! How Fast Can An AGM Battery Be Charged?
 
Last edited:

RAM5500 CAMPERTHING

OG Portal Member #183
Good points. I am a complete newbie when it comes to electrical, but eager to learn from other's experience. Our rig has dual alternators rated at 397 amps combined. Current is first directed to the truck's two batteries; an automatic relay switches to the house batts once it reads full voltage. I don't know the charge rate; is it governed by our Xantrex inverter/charger? If so, it would be 80 A.

Edit: just read a real world test on recharging AGMs from 50% to 100% SOC at the safe recommended rate of .2C (20%) and it took over 5 1/2 hours! My head is spinning!! How Fast Can An AGM Battery Be Charged?
It’s almost impossible to say what charge rate your alternators will charge at nowadays with the technology what it is now.

I have 440amps of dual alt juice, but in the grand scheme of things, that won’t mean much as far as getting it to the house batteries unless done right.

Im not an expert by any means, but I’ve done enough I can figure it out.

if you have a Victron battery monitor, draw your bats down to 60% or so, start the truck, and open the app and see how many amps it’s getting. That’s an easy and accurate way to see what’s going on.

The other issue that comes into play is the charging profiles. Most alternators won’t correctly charge lithium batteries without some sort of gizmo installed, and there’s many various options for that.

On my 2020 Ram 5500 my original plan was to have one alternator charge the truck and one charge the house. Due to the pretty complicated charging system, that’s not an option for me.

so every vehicle will be different

first thing I’d do in your shoes is see how much charge you’re actually getting to the house when the truck is running, and go from there

Inverter has zero influence on battery charge rate from alternator
 
Last edited:

DiploStrat

Expedition Leader
Some comments:

-- It is probable that Overland are using a Blue Sea ACR or similar voltage sensing relay. These are a great solution assuming that your camper batteries and starter batteries are both grossly of the same type, eg., both lead acid.

-- A voltage sensing relay does NOT charge the starter battery first, it merely measures the voltage at one or both batteries and connects when either hits the target voltage (typically a bit over 13v) and disconnects when either drops to about 12.7v, the so-called "full" charge voltage of a lead acid battery. But, as the starter battery typically recovers almost immediately, and it is the camper battery that is deeply discharged, the net effect is close to being the same.

-- Assuming that your alternator charges at a bit over 14v AND that the cables between your starter battery and your camper battery are large enough, typically around 0 AWG, you will get very good performance.

How fast will your lead acid battery charge? A LOT slower than you think. Charge rate is determined by:

-- The difference between the voltages of the battery and the charge source. So the starting charge rate is the highest, dropping as the voltage of the battery rises.

-- The depth of discharge. With lead acid, the highest rate is typically achieved when the battery is about 50%. But as noted, this rate drops rapidly as the battery voltage rises. According to Lifeline, you want a charger/alternator/generator which can supply more amps than the battery will take when it is taking at its highest rate. Anything more than that will NOT lead to faster charging. May keep the alternators from overheating, but you will not charge any faster than the battery will accept.

-- Finally, to avoid sulfation, the battery needs to be held at a high voltage (with low amps) for a L O N G time, 30 minutes to an hour for every 100Ah of battery.

I find it useful to think of things this way:

-- Alternator or generator - use for bulk charge.

-- Solar - use for absorb charge.

-- Shore power, use for both, assuming that your shore charger has a proper absorb stage. Some, eg. Progressive Dynamics, famously don't.

Lithium is a bit different:

-- Lithium batteries tend to have a much flatter curve - discharging the voltage tends to hold very stable until it drops and, when charging, it stays low until the end. For our discussion, that means that a lithium battery sucks up amps - which may be a danger to your alternator.

-- The resting or float voltage of a lithium bank tends to be around 13.5v, thus it is higher than the combine voltage of most intelligent relays. (Victron makes one with voltage settings for their lithium batteries.) So the relay will never open, potentially letting your starter battery, even fully charged, put a load on the camper battery.

-- The opening voltage of 12.7v is too low for most lithium batteries.

-- Scholars debate, but while most lithium banks are made of 3.65v batteries and this would tend to indicate a charge voltage of around 14.6v, there is a lot of anecdotal evidence, that lithium banks last longer when only charged to around 90%; call it 14v.

In the real world, where most of us can't get inside the vehicle's computer controlled wiring, a battery to battery charger is a better option for a lithium camper battery.

YMMV, caveat emptor, etc.
 

Trail Talk

Active member
-- A voltage sensing relay does NOT charge the starter battery first, it merely measures the voltage at one or both batteries and connects when either hits the target voltage (typically a bit over 13v) and disconnects when either drops to about 12.7v, the so-called "full" charge voltage of a lead acid battery. But, as the starter battery typically recovers almost immediately, and it is the camper battery that is deeply discharged, the net effect is close to being the same.

How fast will your lead acid battery charge? A LOT slower than you think.
Thanks for this, easily understood (y) Life before RV was so carefree, I just plugged stuff into wall outlets :unsure:
 

gregmchugh

Observer
Thanks for this, easily understood (y) Life before RV was so carefree, I just plugged stuff into wall outlets :unsure:
The Xantrex inverter/charger is not involved in charging from the engine alternators so it will not limit the charging amps there, it is only used to charge the batteries from 120v shore power or generator power.
 

RAM5500 CAMPERTHING

OG Portal Member #183
Some comments:

-- It is probable that Overland are using a Blue Sea ACR or similar voltage sensing relay. These are a great solution assuming that your camper batteries and starter batteries are both grossly of the same type, eg., both lead acid.

-- A voltage sensing relay does NOT charge the starter battery first, it merely measures the voltage at one or both batteries and connects when either hits the target voltage (typically a bit over 13v) and disconnects when either drops to about 12.7v, the so-called "full" charge voltage of a lead acid battery. But, as the starter battery typically recovers almost immediately, and it is the camper battery that is deeply discharged, the net effect is close to being the same.

-- Assuming that your alternator charges at a bit over 14v AND that the cables between your starter battery and your camper battery are large enough, typically around 0 AWG, you will get very good performance.

How fast will your lead acid battery charge? A LOT slower than you think. Charge rate is determined by:

-- The difference between the voltages of the battery and the charge source. So the starting charge rate is the highest, dropping as the voltage of the battery rises.

-- The depth of discharge. With lead acid, the highest rate is typically achieved when the battery is about 50%. But as noted, this rate drops rapidly as the battery voltage rises. According to Lifeline, you want a charger/alternator/generator which can supply more amps than the battery will take when it is taking at its highest rate. Anything more than that will NOT lead to faster charging. May keep the alternators from overheating, but you will not charge any faster than the battery will accept.

-- Finally, to avoid sulfation, the battery needs to be held at a high voltage (with low amps) for a L O N G time, 30 minutes to an hour for every 100Ah of battery.

I find it useful to think of things this way:

-- Alternator or generator - use for bulk charge.

-- Solar - use for absorb charge.

-- Shore power, use for both, assuming that your shore charger has a proper absorb stage. Some, eg. Progressive Dynamics, famously don't.

Lithium is a bit different:

-- Lithium batteries tend to have a much flatter curve - discharging the voltage tends to hold very stable until it drops and, when charging, it stays low until the end. For our discussion, that means that a lithium battery sucks up amps - which may be a danger to your alternator.

-- The resting or float voltage of a lithium bank tends to be around 13.5v, thus it is higher than the combine voltage of most intelligent relays. (Victron makes one with voltage settings for their lithium batteries.) So the relay will never open, potentially letting your starter battery, even fully charged, put a load on the camper battery.

-- The opening voltage of 12.7v is too low for most lithium batteries.

-- Scholars debate, but while most lithium banks are made of 3.65v batteries and this would tend to indicate a charge voltage of around 14.6v, there is a lot of anecdotal evidence, that lithium banks last longer when only charged to around 90%; call it 14v.

In the real world, where most of us can't get inside the vehicle's computer controlled wiring, a battery to battery charger is a better option for a lithium camper battery.

YMMV, caveat emptor, etc.
Best explanation I’ve seen in awhile

yeah... what he said 👍🏼
 

Buddha.

None of this matters
Nice looking setup.
What size fuel tank do you get with the gas chassis cab 350? Is the spare tire still behind the axle? Is there any complication with insuring the chassis cab?
 

Trail Talk

Active member
Nice looking setup.
What size fuel tank do you get with the gas chassis cab 350? Is the spare tire still behind the axle? Is there any complication with insuring the chassis cab?
Our configuration has a 40 gal. gas tank at the rear of the frame so no factory spare tire or jack was included. It was a two day adventure to secure insurance. The chassis cab VIN came up as "incomplete vehicle" which wasn't accepted by the software. I eventually sent them a detailed email with photos and receipts that was passed on to the underwriter, and they issued an auto policy for the truck and separate property policy for the cabin, as they would for a standard truck camper. I had prepared with an independent valuation but, in the end, they didn't want it.
 
Top