AGM to Lithium, do I need to change Isolator or upgrade alternator?

[68camaro]

Hi, My two 6v batteries died and I would like to upgrade to three Lifeline Heated 12v 100 ah batteries.

My electrical power center under sink area has option for Lithium so I am good there, my solar charger is good, but do I need to upgrade my battery Isolator or move to a DC to DC Converter instead? My alternator is stock heavy duty so will it put out enough amps for the 300 ah lithium batteries?

My concern is making sure Alternator charging capabilities are good and alternator can cool itself with lithiums higher current and protecting alternator and engine battery from load dump?

Thanks

[chin_k]

I don't think you suppose to use the lithium to jump start your engine, so the question is whether you can use your alternative to charge your lithium. I think you do have to get a DC-DC converter, since the lithium has such high current draw that it will overwork your alternator, and maybe make your engine hotter than it needs to if you are climbing hills.

[68camaro]

I don't think you suppose to use the lithium to jump start your engine, so the question is whether you can use your alternative to charge your lithium. I think you do have to get a DC-DC converter, since the lithium has such high current draw that it will overwork your alternator, and maybe make your engine hotter than it needs to if you are climbing hills.

Thanks Chin, I understand I cannot jump start engine with lithium. From my research, I think I do need the DC/DC to replace existing isolator.

[chin_k]

Yeah, that is what I hear too about the need for a converter. You need to figure out the maximum sustainable current that can be draw from the alternator without causing it to overheat or shorten its life.

BTW, did the 6V batteries died from aging, or there is something that we can learn from them? IIRC, you got them a few years ago, and I was surprised that it only last a couple of years.

[Scott]

LFP batteries can gobble up a lot of power in a short period. When alternator charging, that can cause overheating and failure. DC-DC units simply throttle back the current. Temperature-controlled is ideal for closed-loop operation. If possible, keep it simple and stick with solar or shore charging so you don't threaten driving reliability on the road.

I used two 6V golf batteries continuously in my Chinook for over six years. I took them out simply to change to LFP. Those golf batteries are still in use in an off-grid solar backup system.

[68camaro]

BTW, did the 6V batteries died from aging, or there is something that we can learn from them? IIRC, you got them a few years ago, and I was surprised that it only last a couple of years.

I actually purchased the batteries in Dec 2018, installed spring 2019 so they are only a bit over 4 years. They still work but draw down quick. This gave me excuse to move to lithium and increase ah. Warranty is only 2 years.

Honestly, probably my fault for not taking better care of in charging.

[68camaro]

LFP batteries can gobble up a lot of power in a short period. When alternator charging, that can cause overheating and failure. DC-DC units simply throttle back the current. Temperature-controlled is ideal for closed-loop operation. If possible, keep it simple and stick with solar or shore charging so you don't threaten driving reliability on the road.

I used two 6V golf batteries continuously in my Chinook for over six years. I took them out simply to change to LFP. Those golf batteries are still in use in an off-grid solar backup system.

Scott, manu rep told me that to keep alternator safe don't charge with alternator when lithium batteries are below 40% (13.1v) unless I have a DC-DC Charger. Not everyone installs the DC/DC Charger so I will try it without one, but ultimately I will get a 30 amp Victron and may even run two parallel to get 60 amps for quicker charging.

I ordered three Lifeline 100ah heated batteries on sale for 699 and might pull trigger to get a fourth. 300ah will be fine but extra 100 certainly will never hurt, and at 26lbs, they will still weigh less than two 220ah 6v.

I was surprised my 6v only lasted 4 years but attribute it to user mistakes. Electrical is my Achilles heel.

[Scott]

Camaro, I don't completely follow the rep's advice. 40% doesn't really mean much unless you know the size of the bank. Also, LFP is going to take in huge amounts of power up until almost full. I would need more information to feel comfortable with this advice. It's not so much a concern for the batteries as it is the Ford charging system, which was never designed for this task. I would definitely install a DC-DC unit if you plan to go this rout. The Victron stuff is top notch. Unless I'm lost in the weeds, using two in parallel won't do anything to spare your alternator. It'll just be doing two small jobs instead of one big job, if that makes sense. If you really want to do some heavy alternator charging, a second alternator is another way to go, but they typically need high RPM operation to stay cool, and that's annoying if you're stationary. Personally, I'd get a big LFP bank, charge with shore power before leaving, and use solar while camping. Leave the alternator to serve the chassis. But many people feel differently and seem to do just fine.

[68camaro]

Scott, thanks. There is so much conflicting information out there it is tough to discern what really is best thing to do.

I have decided to get the Victron DC/DC charger because that at minimum will protect Ford charging system. At $200 it is not too expensive insurance, only down side is "maybe" restricting some flow from Alternator. The question is do I need to disconnect Eaton Smart Solenoid, not sure I need it.

The 300AH lithiums will be 3x more than I currently have so charging at home ( I have 30v at home) before trip should last me my typical weekends plus I may add forth lithium for total of 400ah (lithiums on big sale), If I add 4th battery I will upgrade Power Center to 60w from current 45.

As far as solar, I have to make sure my BMS in batteries do not allow solar to overcharge as I need to see if batteries should charge less than 100%. I boonedock in the woods with almost no sun so except when driving this should not be a concern.

[Scott]

I have decided to get the Victron DC/DC charger because that at minimum will protect Ford charging system. At $200 it is not too expensive insurance, only down side is "maybe" restricting some flow from Alternator. The question is do I need to disconnect Eaton Smart Solenoid, not sure I need it.

Restricting current flow from the alternator is what you want. That's your goal with the DC-DC unit. Less flow means less work for the alternator, which means less heat, which means less wear/failure.

I don't know what an eaton solenoid is so I'm not exactly sure what it does. But if it's only used to auto connect for charging and/or jump starting, I would eliminate it from the system, personally (if you switch to LFP).

I don't know about your use patterns, but for us, your suggested 400ah bank would be A TON. I mean, easily a week's worth, and that's running a compressor fridge.

The battery BMS doesn't care where the power comes from, be it solar or otherwise. The power coming in from solar panels would be regulated by the solar controller before it goes into the bank. The charge profile would be dictated by the controller.

For this type of battery chemistry, charging to 100% before a trip is perfectly fine. Some say not to store long term above 80% but personally I don't worry about it. LFP batteries can cycle thousands of times, and before I get anywhere close to that number, there will likely be something else to come along. I don't get hung up about it.

I use LFPs for power backup in my home, and I keep them around 90-100% all the time. And I've very deeply discharged them many times. I let the BMS decide when to shut them off. Not ideal, but having them full and ready is what they're for...