Lithium Batteries

[msmith1199]

Just downsized from a Class A DP to a Class B+. I got the residential fridge in the new motorhome so power when off the grid is going to be more of an issue that it was before. I’ve been looking at Lithium batteries and they look like a good solution for me. Only problem I see is physical size. The two current batteries I have are 11.5 inches long and they are a tight fit in the battery compartment. All the lithium batteries I’ve seen are at least 12.5” or longer. So they won’t fit in the existing battery compartment without modifications. But those are all 100AH batteries. I see they also have 200AH lithium batteries. They are a lot longer, over 20 inches, but one of those batteries will fit in the compartment versus two 200AH batteries. So not only does the 200AH battery have a smaller footprint than two 100AH batteries, they are also quite a bit cheaper than buying two 100Ah batteries.

Anybody see any issues in going with one 200ah battery versus two 100ah batteries?

[grizzzman]

pianotuna wrote:
Hi Steve,

But the existing alternator is not going to "see" the LI bank. And the existing alternator is controlled by the Chassis ECM.

In the E-450 the OEM house bank charging circuit is fused at 60 amps (for my unit). The 60 amp are hard to find--so I replaced mine with an auto reset circuit breaker rated at 50 amps. I did add a 2nd charging path with a 2nd circuit breaker, direct to the chassis battery. The wire in both circuits is #8.

Back in the old days when I was using double conversion for limiting shore power, the twin 30 amp fuses on the PD (30 amp) converter did "deform" (i.e. quasi melted). They did not, however, fail.

When I tried double conversion on a GFCI circuit that the Magnum would instantly trip, the surge current was such that the reverse polarity fuses went *poof* more or less instantaneously, due to inrush current from the Magnum.

So, I suspect, that an OEM charging system with replacement LI batteries would blow the fuse before the alternator would fail.

My 2013 F150 output 14.0 at all times. My 2019 F150 output 12.7 to 12.9 over a period of 2 hours. Using a Renolgy 40 amp DC to DC charger is a buck/boost device and bumped the voltage to my preset 14.2 at the cost of less amps(34) If your looking for a solution this is what I would advise you look into.

[pianotuna]

Hi Steve,

But the existing alternator is not going to "see" the LI bank. And the existing alternator is controlled by the Chassis ECM.

In the E-450 the OEM house bank charging circuit is fused at 60 amps (for my unit). The 60 amp are hard to find--so I replaced mine with an auto reset circuit breaker rated at 50 amps. I did add a 2nd charging path with a 2nd circuit breaker, direct to the chassis battery. The wire in both circuits is #8.

Back in the old days when I was using double conversion for limiting shore power, the twin 30 amp fuses on the PD (30 amp) converter did "deform" (i.e. quasi melted). They did not, however, fail.

When I tried double conversion on a GFCI circuit that the Magnum would instantly trip, the surge current was such that the reverse polarity fuses went *poof* more or less instantaneously, due to inrush current from the Magnum.

So, I suspect, that an OEM charging system with replacement LI batteries would blow the fuse before the alternator would fail.

[BFL13]

https://shop.pkys.com/Alternator-Lithium-Battery.html

[steveh27]

Here's a site I found:

https://shop.pkys.com/Alternator-Lithium-Battery.html

[msmith1199]

I won’t be leaving the motorhome plugged in all the time. It will only being getting 110 volts when we’re using it and plugged into shore power or when using the generator. We got the smaller motorhome specifically because we rarely stay in any one spot for more than a few days. So most of the use we’ll only be plugged in two or three days at a time. I do have power in my storage unit, but it’s only 15 amp 110v so I go down the day before I’m going to pick up the motorhome and plug it into that to turn the fridge on.

[BFL13]

Don't have a link, but just an "ISTR" on alternator charging where the issue was, when you added fatter wire etc so you got more charging amps, and ran the fridge etc, that this would be more amps for longer than the alternator could take and it would heat up and die.

It might be bogus for all I know for sure. There is something about the alternators in police cars being able to take more than the ones in regular cars. I ASSume the ones in MHs are regular types. Although in a Class C, which is made from an "incomplete truck" that could have been made into an ambulance instead, maybe it would have the stronger type of alternator.

Here we have a worry that the Li batts might be harmed (can't say--seems situational?) and that the alternator might be harmed from too many amps (Li being low R etc, and the fridge on) so somebody who knows about all this should step in and clear it all up.

[3_tons]

pnichols wrote:
3 tons,

I'm wondering about your last sentence above.

Doesn't your 9245 automatically drop back to a 13.XX volt float voltage at some point when it's charging batteries?

I believe that LiFePo4 batteries have a recommended float voltage such that they can be left hooked up full time to a converter/charger that eventually settles at their float voltage, just like any other type of battery.

For instance Battle Born LiFePo4 batteries can be floated at 13.6 volts or lower indefinitely according to their specifications, so you shouldn't have to disconnect them from your 9245 when it drops down to it's float voltage.

As for when driving with the engine alternator hooked up to the batteries, after just a few minutes when things are warmed up, our RV's alternator settles in around to the mid-13's in voltage, anyway.

True with the 9245!....(except for the 21hr/15 min equalization cycle)...This is why I prefer the standard charger (with charge wizard in boost mode) to PD’s LiFePo4 offering, but once the battery has charged (and subsequently finished it’s BMS dance whereby current and voltage values briefly alternate..), I simply disconnect the battery (via basic knob switch atop battery post)...I mostly dry camp, so rely on solar and battery...

[pianotuna]

msmith1199 wrote:

BFL13 wrote:
She wants to keep the charging to 50 amps each so 100a for the two. Meanwhile there have been posts that the alternator will fry from trying to charge the thirsty Li house batts.

Sounds like the way to go is disconnect/disable alternator charging and just leave in the Aux start from the house feature if ever needed.

So is it likely that in most motorhomes there is no DC to DC charger and the alternator is just wired directly to the house batteries and charges them with whatever output it has?

Hi msith1199,

The alternator is controlled by the ECM of the chassis. Most alternators have a duty cycle rating. In my case, that is 120 amps. But continuous duty is 1/3 of that, or about 40 amps.

The only time one is likely to see greater amperage is if both the starter battery and the house batteries are "hungry" or if a large load is present in the house. For example the water heater on the electric setting.

I deliberately added a 2nd charging path from the Chassis battery to the house bank. I do have manual control of the connection. I have seen 70 amps for brief periods of time. I monitor the voltage on the chassis battery. If it gets to 12.3, I turn off the connection.

I've seen no complaints of burned out alternators. Maybe BFL13 could give us a link?

[3_tons]

Itinerant1 wrote:
I remember reading a thread on another forum that the person added a on/ off switch on the dash so that the charging to the batteries could be turned off during the drive so not to hold the batteries at a high voltage once it was charged. I don't remember all the exact details.

And a possibly more temporary option might be to simply pull the trailer power supply fuse (normally supplies the 7 pin plug) inside the under-hood fuse box - there’s usually a printed fuse diagram just inside the lid...

3 tons

[pnichols]

3 tons,

I'm wondering about your last sentence above.

Doesn't your 9245 automatically drop back to a 13.XX volt float voltage at some point when it's charging batteries?

I believe that LiFePo4 batteries have a recommended float voltage such that they can be left hooked up full time to a converter/charger that eventually settles at their float voltage, just like any other type of battery.

For instance Battle Born LiFePo4 batteries can be floated at 13.6 volts or lower indefinitely according to their specifications, so you shouldn't have to disconnect them from your 9245 when it drops down to it's float voltage.

As for when driving with the engine alternator hooked up to the batteries, after just a few minutes when things are warmed up, our RV's alternator settles in around to the mid-13's in voltage, anyway.

[Itinerant1]

I remember reading a thread on another forum that the person added a on/ off switch on the dash so that the charging to the batteries could be turned off during the drive so not to hold the batteries at a high voltage once it was charged. I don't remember all the exact details.

[3_tons]

msmith1199 wrote:
Not being an electrician I don’t completely understand your question. Are you asking about the existing Converter in the motorhome? If so it’s a PD4560 by Progressive Dynamics. It’s basically the entire 110 volt and 12 volt electrical panel all in one with the converter built into the panel. The one I have has the switch to turn it to Lithium mode. Per their website having that switch is an option. So luckily for me Nexus ordered the panels with that option. So I’m good for charging the batteries with the generator or when I’ve got 110 power. But I have a residential fridge so I want the batteries to charge from the alternator too because on long drives there will always be a draw on them otherwise. I understand it may not fully charge the batteries, but as long as it keeps them going.

So I went to the PD site but did not see any algo specifics on the 4560

https://www.progressivedyn.com/lithium-battery-power-centers/

When PD ‘suggest’ they’ve worked with several LiFePo4 manufacturers, this simply means that they’ve decided on a constant ON 14.4v charge methodology (with no programmability, the easy way out $$), but understand that Li’s don’t like to be stored for an extended period in this way - in fact, in some of their other chargers 14.4v is stated to be an equalization mode (i.e. every 21hrs/15 min for lead acid batts).

So I’ll just assume the 4560 has the same algo as their Li 9100-L series which simply remains at a constant 14.4v throughout the entire charge and never shuts down - ordinarily not an ideal plan IF left continuously on, but since you have a compressor refer (duty cycle enters the pic) I would think that this concern becomes a lesser issue...JMO

My main grievance with these ‘so called’ LiFePo4 chargers is their lack of programmability, thus I just stayed with my 9245 (with charge wizard in 14.4v boost) and (when on shore power) just added a simple battery post disconnect to prevent extended charging....

3 tons

[msmith1199]

Not being an electrician I don’t completely understand your question. Are you asking about the existing Converter in the motorhome? If so it’s a PD4560 by Progressive Dynamics. It’s basically the entire 110 volt and 12 volt electrical panel all in one with the converter built into the panel. The one I have has the switch to turn it to Lithium mode. Per their website having that switch is an option. So luckily for me Nexus ordered the panels with that option. So I’m good for charging the batteries with the generator or when I’ve got 110 power. But I have a residential fridge so I want the batteries to charge from the alternator too because on long drives there will always be a draw on them otherwise. I understand it may not fully charge the batteries, but as long as it keeps them going.

[3_tons]

BFL13 wrote:
She wants to keep the charging to 50 amps each so 100a for the two. Meanwhile there have been posts that the alternator will fry from trying to charge the thirsty Li house batts.

Sounds like the way to go is disconnect/disable alternator charging and just leave in the Aux start from the house feature if ever needed.

X2, 50a per battery is a conservative rate that’ll never but your pricey batteries at any risk, and the actual receptivity rate will typically be even lower (depending on SOC) ..Due to Li’s high receptivity rate, if you have a decent amount of solar (as a fellow Nevadan - lol) you’ll likely not get much value outta the vehicle’s alternator anyway... I would however be interested to know what brand or model of switchable charger your rig has - would be nice to understand the Li charger’s stated algorithm...Of the one’s I’ve considered, most tend to be of the ‘one size fits all’ variety...JMO



Congrats,

3 tons

[msmith1199]

BFL13 wrote:
She wants to keep the charging to 50 amps each so 100a for the two. Meanwhile there have been posts that the alternator will fry from trying to charge the thirsty Li house batts.

Sounds like the way to go is disconnect/disable alternator charging and just leave in the Aux start from the house feature if ever needed.

So is it likely that in most motorhomes there is no DC to DC charger and the alternator is just wired directly to the house batteries and charges them with whatever output it has?