Lithium Newby

[NeedToRetire]

I’m a Lithium battery dolt, though good electrician & troubleshooter. My wife and I purchased a used 2020 28 foot Jayco travel trailer and have been using it for short trips this summer, but are intending on doing a 3 weeks get away in March to Al & FLA. In wanting to be more self-contained, I knew I needed to upgrade the battery that came with it. Jayco had just one single GR24 lead acid battery, I use a CPAP with the 12v adapter and need to use it for the short times we will be off the grid. My plan was to just purchase 2 - 6 Volt golf cart batteries and call it a day, but then I read here and was told that I should seriously consider lithium batteries.
So I upgraded the battery box to be able to hold 2 group 24 batteries and then put the camper in storage. When I was getting ready to buy the golf cart batteries a week or two ago I ended up making a knee jerk decision and went and bought two group 24 100ah lithium batteries. So here I am with two brand new lithium batteries and have a ton of questions and concerns.

1. My Converter does not have a Lithium switch. My thoughts currently are to use the existing Converter and add a 20amp Lithium charger to the system, I have read here that configuration might work ok?

2. I think I understand that 14.8V is Lithium fully charged. How often does this need to occur for batteries to become “Balanced” Can I rely on the converters 13.6V 55 amp charger the majority of the time and maybe once a week clip on a 20amp Lithium charger for as long as it takes to reach 14.8V?

3. What state of charge percentage are the batteries through their usefulness to the campers 12v needs? If 14.8v is 100%, what is 0% ? The manual that came with the Lithium’s I purchased shows a curve at 90% at around 12V and dropping off a cliff to 100% discharge. So is 12V the cut off?

4. I saw a post making me concerned about the alternator in my truck, like I need to add a isolator to prevent damage while towing and having the two battery systems conneted to each other? Is this an issue?

5. I now have the batteries in my heated garage on the work bench and the camper in cold storage. I don’t plan on installing them until a week before we head south. Should I fully charge them now and let them sit? At what point should I recharge, or should I just leave the charger connected?

I know these are a lot of questions, so thanks in advance of any help!

[inthepines]

Originally Posted by NeedToRetire

I’m a Lithium battery dolt, though good electrician & troubleshooter. My wife and I purchased a used 2020 28 foot Jayco travel trailer and have been using it for short trips this summer, but are intending on doing a 3 weeks get away in March to Al & FLA. In wanting to be more self-contained, I knew I needed to upgrade the battery that came with it. Jayco had just one single GR24 lead acid battery, I use a CPAP with the 12v adapter and need to use it for the short times we will be off the grid. My plan was to just purchase 2 - 6 Volt golf cart batteries and call it a day, but then I read here and was told that I should seriously consider lithium batteries.
So I upgraded the battery box to be able to hold 2 group 24 batteries and then put the camper in storage. When I was getting ready to buy the golf cart batteries a week or two ago I ended up making a knee jerk decision and went and bought two group 24 100ah lithium batteries. So here I am with two brand new lithium batteries and have a ton of questions and concerns.

1. My Converter does not have a Lithium switch. My thoughts currently are to use the existing Converter and add a 20amp Lithium charger to the system, I have read here that configuration might work ok?

2. I think I understand that 14.8V is Lithium fully charged. How often does this need to occur for batteries to become “Balanced” Can I rely on the converters 13.6V 55 amp charger the majority of the time and maybe once a week clip on a 20amp Lithium charger for as long as it takes to reach 14.8V?

3. What state of charge percentage are the batteries through their usefulness to the campers 12v needs? If 14.8v is 100%, what is 0% ? The manual that came with the Lithium’s I purchased shows a curve at 90% at around 12V and dropping off a cliff to 100% discharge. So is 12V the cut off?

4. I saw a post making me concerned about the alternator in my truck, like I need to add a isolator to prevent damage while towing and having the two battery systems conneted to each other? Is this an issue?

5. I now have the batteries in my heated garage on the work bench and the camper in cold storage. I don’t plan on installing them until a week before we head south. Should I fully charge them now and let them sit? At what point should I recharge, or should I just leave the charger connected?

I know these are a lot of questions, so thanks in advance of any help!

1) while it is nice to have a lithium capable converter, you will be fine and it is exactly what I do. run an old converter and use a dedicated lithium charger to charge to 100%, the converter will get it close.


2) the battery bms will balance each battery itself, using the charger to top them off will help. The caveat here is; is since they will be in parallel , if one battery does have bad cells, it can bring the good battery down trying to balance off. Charger or not, nothing will fix that except replace the bad battery.


3) yes that is basically it. 0% might be 11.8v 10% is generally around 12V that is the beauty of lifepo4's you get the full 12v the entire discharge unlike lead.


4) If it's a newer truck, you may need a diode/isolator if you leave the trailer plugged in with the truck off. I don't know for sure on this. I don't leave my truck plugged into the trailer any longer than needed but I don't have this and it has not caused harm. Some ppl recommend using a DC-DC charger so the lithiums don't fry your alternator from taking the full charge nonstop-
but in my experience with a properly sized wire with no more than 3% v drop on that run. I've never see a full 30 amp charge going into the trailer batteries.


5) I wouldn't charge them until a month before or I'd charge them to make sure they are good and than I'd discharge them down to 80%.
Personally I charge the new battery and than discharge it completely to make sure it puts out what it is rated for. Than I charge it back up to 80% and store it until I'm ready to use and than top it off.

They will discharge naturally about 1%~ a month so if you store for an extended amount of time, I would put a charger on them every 6 months.

[NeedToRetire]

Originally Posted by inthepines

4) If it's a newer truck, you may need a diode/isolator if you leave the trailer plugged in with the truck off. I don't know for sure on this. I don't leave my truck plugged into the trailer any longer than needed but I don't have this and it has not caused harm. Some ppl recommend using a DC-DC charger so the lithiums don't fry your alternator from taking the full charge nonstop-
but in my experience with a properly sized wire with no more than 3% v drop on that run. I've never see a full 30 amp charge going into the trailer batteries.

Thanks Inthepines for all the insight.

My Truck is a near new 2023 Ford F250 Diesel 6.7L. You mention possibly needing an isolator on newer trucks, if I read correctly? If it matters, I bought this truck with plow package & 5th wheel ready. My Truck spec's say I have a 410 amp alternature with two seperate batteries. I will make sure to unplug trailer from the truck when not towing. Will I be ok as is, while towing and connected? My understanding of vehicle charging systems is that an alternator will maintain the batteries between 14.0-14.5VDC.

Originally Posted by inthepines

5) I wouldn't charge them until a month before or I'd charge them to make sure they are good and than I'd discharge them down to 80%.
Personally I charge the new battery and than discharge it completely to make sure it puts out what it is rated for. Than I charge it back up to 80% and store it until I'm ready to use and than top it off.

At what point is 80% ? 11.84v is 80% of 14.8v, is that correct?

[Persistent]

InThePines covered the issue very well.

For better advice, post make and model# of
current charger,
new portable charger, and
lithium batteries.

[NeedToRetire]

Originally Posted by Persistent

InThePines covered the issue very well.

For better advice, post make and model# of
current charger,
new portable charger, and
lithium batteries.

Persistence, thanks for the chart! That covers it well, you have been very helpful on my path to Lithium and your help is greatly appreciated.

Here's what I current have:

New Lithium Battaries :two Wattcycle LifePO4 GR24 100AH with BMS "I wrongly thought that included a wireless way to monitor the voltage as well"

Current Converter: WFCO WF-8955PEC output 13.6VDC 55 Amp

New Lithium Charger:Wattcycle offered at check out a 20 Amp for $99.00 which seemed pricey, so I didn't purchase a charger yet. I see 20A Lithium LifePO4 chargers on Amazon for $55-$70.

[Marine359]

^^^@Inthepines
If you don’t have a dc/dc charger, there’s no worry about frying alternator. The 7-pin is normally only sending 4-10 amps (depends on vehicle make) when ignition is on. A 20 amp LFP charger works fine as long as you have access to shore power or generator. If not, 200w of solar will top them off from 60% SOC. Figure 150w x 6hrs = 900wh. Resting voltage at 100% SOC is 13.6v. Your existing charger will take a very long time to get there and may never balance. You’ll need a 20 amp charger, or solar to balance, but that doesn’t need to happen often. Maybe only every 5-6 charge cycles.

[SafariBen]

2. I haven't seen a spec for "how often" they need to be fully charged to balance the cells. Once a week is plenty, once a month is probably plenty. You might consider solar if you can find a seller of surplus/used commercial panels nearby. One 3-400w commercial panel and a decent MPPT controller won't be much more than the Li charger, and will add a little charge everyday when you're boondocking, and fully charge when you are not using the trailer.



You can only dream that the charge wire will overload your alternator without a large effort to upgrade the wire. Li has low internal resistance, which is why we're careful with motorhomes connecting the Li to the chassis with short 00 cables, you have 20'+ of probably 14g wire, so the voltage will drop fast as the amps rise, limiting the current to something less than ideal for the rate the Li COULD accept a charge. You'll probably find that if you want to get a decent charge into the Li without driving several hours a day, that you'll want a dedicated 10 or 8g wire from the alternator or truck battery to the TT battery.

[NeedToRetire]

Originally Posted by Marine359

^^^@Inthepines
If you don’t have a dc/dc charger, there’s no worry about frying alternator. The 7-pin is normally only sending 4-10 amps (depends on vehicle make) when ignition is on. .

So being connected to the truck shouldn't be a problem? This of all the potential issues is my biggest concern. The truck is less than a year old and do not want to fry an alternator and then be told by a dealer its my fault after paying two arms and a leg for it new. I gave thought to removing the DC supply from the 7 pin connector.

[Persistent]

Originally Posted by NeedToRetire

Persistence, thanks for the chart! That covers it well, you have been very helpful on my path to Lithium and your help is greatly appreciated.

Here's what I current have:

New Lithium Battaries :two Wattcycle LifePO4 GR24 100AH with BMS "I wrongly thought that included a wireless way to monitor the voltage as well"

Current Converter: WFCO WF-8955PEC output 13.6VDC 55 Amp

New Lithium Charger:Wattcycle offered at check out a 20 Amp for $99.00 which seemed pricey, so I didn't purchase a charger yet. I see 20A Lithium LifePO4 chargers on Amazon for $55-$70.

Here are the instructions for a Wattcycle LiFePO4 100 amp hour battery. There are several other models. Pick the manual for yours. Read the manual and try to understand it the best you can. There are several paragraphs that address your questions.

Yes, fully charge each new battery before connecting them together and before installation. Voltage must be identical before connecting.

Discharge them to 50% for long term storage. Leave them fully charged for short term storage.

Maximum charging voltage is 14.6 volts. This provides finishing charge and balance.

The manual does not tell you how often to fully charge and balance because it assumes you will balance every time you charge. Some batteries require very little balancing. Some require a lot of balancing.

There is variation in the cells used to build the batteries. It depends on the individual cells.

I recommend you permanently mount the 20 amp charger and use it when ever you charge. The two chargers can work together.

The Wattcycle charger is probably better at $99 than the other at $50. Different chargers work differently and you can be sure the Wattcycle charger will be optimum and better quality.

Be careful not to short terminals or connect in reverse polarity. The BMS may not be able to protect in these case.

Note, the BMS may disconnect the internal cells to protect them. Resetting has specific procedures. See instructions. Lots of good advice in the manual. Lots of boring and/or confusing instructions as well. Do the best you can.

https://cdn.shopify.com/s/files/1/08...f?v=1728733803

[SafariBen]

One of the large advantages of Li is they don't need to be fully charged for storage, they're happier being cycled 20-80% most of their life, while lead wants to be charged back to 100% ASAP. The BMS will protect a weak cell by shutting down and you'll know you need a balance. The balancing only happens when you get above 95, 99%? state of charge, so it's not needed every charge, and may even be harmful every charge?



No need to discharge to 50% for storage, even discharging 5-10% is better than leaving at 100%. Some Li chargers will fully charge, then not recharge until 50% or something. Basically you only want 100% immediately before you leave, or when you shut off the vehicle if you're charging from the engine. Some of this may be out of date, or it may be based on sound battery chemistry, that the battery companies are de emphasizing for marketing reasons.

[NeedToRetire]

Here's what I think I'm going do after digesting all the advice.

1: I am going to get the Watcycle 20 amp charger and charge the batteries to 100%
2: discharge them down to 80% and keep an eye on them though out the winter.
3:Late February I will charge them back to 100% and install them into the trailer and hit the road for 3-4 weeks.
4: While away I will turn the 20 amp Lithium charger on once a week for how ever long it takes to hit 14.6V and then shut off.
5: I'm also going to not worry about hurting the alternator on the truck while connected to the trailer and in transit.

Next fall we are planning 6-8 weeks out west, so I am planning on adding a 100-200 watt solar panel & controller then. We want to alternate remote/off grid with the full service camp grounds during this trip. I didn't mention it, but I also will be traveling with a Honda 3000w Inverter gen to use when needed.

[xrated]

A LFP battery is generally considered to be almost fully charged when it is at 13.8V or 3.45 per cell. 14.6V is the very maximum that the battery should be exposed to when charging and many of us do not use that high of a voltage. Personally, my charger tops out at 14.2V and that will fully charge the battery to 100% SOC. The difference between that 14.2V and the 14.6 is simply the amount of time that it takes to charge the battery. Many LFP battery manufacturers will recommend a storage SOC at ~ 50% for long term strorage....in other words, anything longer than a month or so. Every year when I winterize my trailer and get ready for it to go into winter storage time, I discharge the battery down to around 50% SOC and then turn off the battery disconnect switch that I installed so that there is no drain on the battery. Normal self discharge for a LFP battery is around 2%/month. So a winter storage of say 5 months would result in the battery SOC being down to around 40% SOC as long as the battery does NOT have phantom drains on it....things like CO/Propane detectors, AM-FM-CD audio units, any other electronic equipment that doesn't shut off with a battery switch. I installed a 300A battery cutoff switch as a total/complete cutoff for the battery. It's easier to flip the switch off than it is to disconnect a lead off of the battery.

With your new batteries, get them up to a 100% SOC and then drain them down to around 50% SOC and let me sit like that over the winter with nothing hooked up to them. That 50% SOC is right at 13.0 to 13.1 volts and it's not critical to be exact at that point. Just don't fully charge them to 100% and then leave them like that. BattleBorn suggests that be done to their batteries and I wholeheartedly disagree with that.

[dvspl]

Originally Posted by NeedToRetire

Here's what I think I'm going do after digesting all the advice.

1: I am going to get the Watcycle 20 amp charger and charge the batteries to 100%
2: discharge them down to 80% and keep an eye on them though out the winter.
3:Late February I will charge them back to 100% and install them into the trailer and hit the road for 3-4 weeks.
4: While away I will turn the 20 amp Lithium charger on once a week for how ever long it takes to hit 14.6V and then shut off.
5: I'm also going to not worry about hurting the alternator on the truck while connected to the trailer and in transit.

Next fall we are planning 6-8 weeks out west, so I am planning on adding a 100-200 watt solar panel & controller then. We want to alternate remote/off grid with the full service camp grounds during this trip. I didn't mention it, but I also will be traveling with a Honda 3000w Inverter gen to use when needed.

Sounds like a good plan to me. Good luck and enjoy your travels.

[Persistent]

It sounds like a good plan to me as well.

I wish you good luck and happy trails ahead.