Lithium battery in the step well

[Johnynorthland]

I have a 2019 Redhawk 25R class C. I’m thinking of replacing my lead acid coach battery, located in the step well, with lithium, (and converter/charger).

Has anyone done this? If so how is the battery holding up being this area is not totally water tight and subjected to outside temps.

[craigav]

My house battery is in a slideout compartment (not under the steps) but it is still exposed to the weather and I have replaced the lead acid battery with a Lithium (LifePo4) 100a battery. In fact, I plan to add a few more LifePo4 batteries in the future (not sure where just yet, likely in a couple of oem battery boxes mounted to the frame as Ford supplies for E450 ambulances).

Things to consider, you don't want to allow the converter to charge a LifePo4 battery when the temps are below freezing (or charge the battery by any other means) as that will damage the battery (discharging below freezing is ok and some people use a battery heater mat to get around this issue). Also, another item to consider is that a LifePo4 battery when not at a full charge and then you turn the engine on (which should charge the battery) that action will provide more charge current to the LifePo4 battery than what the factory charge wiring and setup is designed for. In other words, the battery would likely pull as many amps off the alternator as it could which will cause issues for the alternator and likely exceed the 80a circuit breakers in the charge circuit to the coach battery. (LifePo4 batteries have very low resistance compared to lead acid, and that is why they pull a lot of current when charging if you don't limit the charge current, and a bank of them would be even more concerning)

To prevent that from happening, I purchased a Renogy 40A DC to DC charger that will limit the charge rate from the engine alternator\battery to the LifePo4 battery. Although I haven't installed that yet, I plan to do so before my next adventure... which could be early spring. ~CA

[Johnynorthland]

Originally Posted by craigav

My house battery is in a slideout compartment (not under the steps) but it is still exposed to the weather and I have replaced the lead acid battery with a Lithium (LifePo4) 100a battery. In fact, I plan to add a few more LifePo4 batteries in the future (not sure where just yet, likely in a couple of oem battery boxes mounted to the frame as Ford supplies for E450 ambulances).

Things to consider, you don't want to allow the converter to charge a LifePo4 battery when the temps are below freezing (or charge the battery by any other means) as that will damage the battery (discharging below freezing is ok and some people use a battery heater mat to get around this issue). Also, another item to consider is that a LifePo4 battery when not at a full charge and then you turn the engine on (which should charge the battery) that action will provide more charge current to the LifePo4 battery than what the factory charge wiring and setup is designed for. In other words, the battery would likely pull as many amps off the alternator as it could which will cause issues for the alternator and likely exceed the 80a circuit breakers in the charge circuit to the coach battery. (LifePo4 batteries have very low resistance compared to lead acid, and that is why they pull a lot of current when charging if you don't limit the charge current, and a bank of them would be even more concerning)

To prevent that from happening, I purchased a Renogy 40A DC to DC charger that will limit the charge rate from the engine alternator\battery to the LifePo4 battery. Although I haven't installed that yet, I plan to do so before my next adventure... which could be early spring. ~CA

Hi Craig.

Thanks for the info. I was thinking about replacing my alternator with a mechman high output alternator so I can fully charge the lithium’s traveling between campgrounds. But I need to do much more research before I pull the trigger. I’m thinking of just installing a inverter/converter/charger with a built in transfer switch and 2 lithium bats for now. Then see how it goes and add solar down the road if We keep our rig.

Rather than do the alternator, your suggestion of that DC to DC charger sounds good. I just don’t know how to work that in to my system if I installed a inverter/converter/charger?

[craigav]

Originally Posted by Johnynorthland

Hi Craig.

Thanks for the info. I was thinking about replacing my alternator with a mechman high output alternator so I can fully charge the lithium’s traveling between campgrounds. But I need to do much more research before I pull the trigger. I’m thinking of just installing a inverter/converter/charger with a built in transfer switch and 2 lithium bats for now. Then see how it goes and add solar down the road if We keep our rig.

Rather than do the alternator, your suggestion of that DC to DC charger sounds good. I just don’t know how to work that in to my system if I installed a inverter/converter/charger?

I have an AIMS inverter/converter/charger now which works well. I agree that would be a good plan. Before that I was using a PowerMax PM3-100 (the pm3 has an adjustable voltage output that I set to 14.4) and using the smaller inverter the RV came with.

Regarding the alternator and my research on that, these LifePo4 batteries will take all the power they can get, and even the high power alternators that are available are not designed to run at 100% constant duty as they will overheat and have a short life (based only on my research). In addition, the factory wiring for the alternator is not sufficient for a lot more amps than the factory alternator puts out.

I would suggest to look at the Renogy website as they have the install docs there to review as well as information on their different dc2dc chargers (20,40,60a). I went with the 40, as my thoughts were that at say 5 hours drive time, that would be enough power to replenish ~200 amps of discharge and not require running new wires. Although you do have to bring in the input wires to the charger, and output wires, my plan is to do this near where the relay is under the hood. You can see a picture of the relay in another post regarding "relay by the battery". If you find other articles from RV'rs in other places, you will find that these high power alternators do not get great reviews in regards to longevity, probably because they get to hot (imo).

Keep in mind that you can consider this in two different aspects, the inverter/converter/charger whether or not you install one doesn't change how the engine charging circuit will work. You have a charge circuit you can leverage from the engine alternator, and the other being from the park power supply\or onboard generator. Each circuit is independent of the other, similar to how it is from the factory. Neither circuit needs to be wired differently because of the other circuit. Let me know your thoughts and plans and I can add more detail if that would help. FYI, I started to go with the 60a dc to dc charger, however at the time Renogy had a sale on the 40a dc2dc chargers saving me about $100.00

Last thought to share, the engine alternator and charge circuit depending on several factors, will reduce the voltage output to around 13.8~14v while driving, the renogy charger is designed to charge the Lifepo4 batteries at a constant voltage until they reach 14.4 (maybe 14.6v I don't recall exactly and I think it is adjustable), in any case, even if the alternator is at 13.8 volts, the charger will still charge the LifePo4 batteries at the 14.4 voltage until they reach full capacity.

~CA

[Johnynorthland]

Originally Posted by craigav

I have an AIMS inverter/converter/charger now which works well. I agree that would be a good plan. Before that I was using a PowerMax PM3-100 (the pm3 has an adjustable voltage output that I set to 14.4) and using the smaller inverter the RV came with.

Regarding the alternator and my research on that, these LifePo4 batteries will take all the power they can get, and even the high power alternators that are available are not designed to run at 100% constant duty as they will overheat and have a short life (based only on my research). In addition, the factory wiring for the alternator is not sufficient for a lot more amps than the factory alternator puts out.

I would suggest to look at the Renogy website as they have the install docs there to review as well as information on their different dc2dc chargers (20,40,60a). I went with the 40, as my thoughts were that at say 5 hours drive time, that would be enough power to replenish ~200 amps of discharge and not require running new wires. Although you do have to bring in the input wires to the charger, and output wires, my plan is to do this near where the relay is under the hood. You can see a picture of the relay in another post regarding "relay by the battery". If you find other articles from RV'rs in other places, you will find that these high power alternators do not get great reviews in regards to longevity, probably because they get to hot (imo).

Keep in mind that you can consider this in two different aspects, the inverter/converter/charger whether or not you install one doesn't change how the engine charging circuit will work. You have a charge circuit you can leverage from the engine alternator, and the other being from the park power supply\or onboard generator. Each circuit is independent of the other, similar to how it is from the factory. Neither circuit needs to be wired differently because of the other circuit. Let me know your thoughts and plans and I can add more detail if that would help. FYI, I started to go with the 60a dc to dc charger, however at the time Renogy had a sale on the 40a dc2dc chargers saving me about $100.00

Last thought to share, the engine alternator and charge circuit depending on several factors, will reduce the voltage output to around 13.8~14v while driving, the renogy charger is designed to charge the Lifepo4 batteries at a constant voltage until they reach 14.4 (maybe 14.6v I don't recall exactly and I think it is adjustable), in any case, even if the alternator is at 13.8 volts, the charger will still charge the LifePo4 batteries at the 14.4 voltage until they reach full capacity.

~CA

After reading through all of this I think your right the DC to DC charger is the way to go. I am thinking of going with the Aims 2500 inverter/converter/charger with transfer switch, and 2- 200 Ah SOK lithium batteries. So correct me if I’m wrong, but what you are telling me the DC to DC charger for the batteries is necessary other wise I will be pulling to much from the alternator? I’ve watched LoLoHo on YouTube he had same issue and had electrical issues with his Ford pickup truck due to the same thing we are talking about. He went with a Mechman alternator and solved his problem. He never mentioned upgrading his alternator wiring, or at least I didn’t catch that part. Makes perfect sense to me though!

I will keep researching and post back when inclined.

Thanks Craig

[craigav]

Originally Posted by Johnynorthland

After reading through all of this I think your right the DC to DC charger is the way to go. I am thinking of going with the Aims 2500 inverter/converter/charger with transfer switch, and 2- 200 Ah SOK lithium batteries. So correct me if I’m wrong, but what you are telling me the DC to DC charger for the batteries is necessary other wise I will be pulling to much from the alternator? I’ve watched LoLoHo on YouTube he had same issue and had electrical issues with his Ford pickup truck due to the same thing we are talking about. He went with a Mechman alternator and solved his problem. He never mentioned upgrading his alternator wiring, or at least I didn’t catch that part. Makes perfect sense to me though!

I will keep researching and post back when inclined.

Thanks Craig

Yes, with lithium batteries, the best option I am aware of to avoid lots of issues is to use the dc to dc charger as the batteries will pull lots of current off of the alternator. A larger alternator certainly helps with that, but brings in other issues as well. Other companies besides renogy make dc2dc chargers, however it appears to me that renogy has the best value for the money.

I will have more details in the future as even though I have purchased everything I believe I will need, I haven't installed it all due to being delayed because of shoulder surgery. I hope to install the charger along with several other things early this spring.

~CA

[Johnynorthland]

Originally Posted by craigav

Yes, with lithium batteries, the best option I am aware of to avoid lots of issues is to use the dc to dc charger as the batteries will pull lots of current off of the alternator. A larger alternator certainly helps with that, but brings in other issues as well. Other companies besides renogy make dc2dc chargers, however it appears to me that renogy has the best value for the money.

I will have more details in the future as even though I have purchased everything I believe I will need, I haven't installed it all due to being delayed because of shoulder surgery. I hope to install the charger along with several other things early this spring.

~CA

Thanks Craig. Have a speedy recovery. Keep in touch, PM me if you’d like. But I’ll keep posting.