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Old 05-12-2021, 12:09 PM   #1
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Lipo batteries

2019 Ventana 3412. I'm changing to Lipo batteries. What do I need to do to protect my alternator if the batteries are low before hitting the road? Do I need a DC to DC charger? If so where do I hook it up? Installing 600AH of Lipo.
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Old 05-12-2021, 01:44 PM   #2
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Lipo batteries

Many on here say that you must have a DC to DC charger to keep from burning up your alternator. Itís true that Lithium batteries can absorb huge amounts of charge, and if the cable run from the alternator is short enough, and the wire is big enough, I am sure it can happen.

In my case, I added four 280ah lithium batteries to my 2020 DS4369. The alternator wiring runs from my alternator on the left rear of the engine, over to the chassis batteries on the passenger side, thru the battery charge/isolation controller, then all the way up front just behind the front tires, back to the drivers side, and then attaches to my batteries.

I too was thinking that I would need a dc to dc charger. But in testing the amperage load and the alternator temperatures, I decided that in my case it it unnecessary. The run to my batteries is so long and the wiring is small enough, that it self limits the amps my batteries can ever draw. Even when fully discharged, the most Iíve ever seen going to my house batteries is 90 to 100 amps and another 40 or so to the chassis batteries right after start. After a few minutes, my chassis batteries are only drawing about 5 amps.

So, I have an alternator rated at 240 amps, and the largest draw I have ever seen is about 160 amps total. Usually it is 100 amps or less. I have also never seen any alternator temps above what I would consider normal, or what I saw prior to adding the 1120 amp hours of lithium. So in my case, I have now driven about 5000 miles and have had no issues.

In fact, many times the chassis battery management system shuts down the charge to the lithium house batteries after only a short time while they are still far from fully charged. When that happens, I just close the house/chassis switch on my dash to reconnect the battery isolator. Since I have Bluetooth monitors on each of the batteries, I can keep track of their charge state to manage them.

To date they are awesome, last for 2 full days boon-docking, and I have had no charge related issues, or any issues actually. I will never go back to lead acid batteries again!
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Old 05-12-2021, 09:38 PM   #3
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Same here , no dc to dc charger. I have 1400AH of LPO4 and the most I have seen while driving is 86a with one AC on. This is during the day with solar. You can buy a blue tooth clamp on ammeter for $60 and and do your own test so you know for sure.
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Old 05-13-2021, 10:39 AM   #4
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Correction on my earlier post, my Allegro Bus 45LP had a 240 amp alternator, my current DS4369 has a 210 amp alternator.

Also, some asked why the B.I.M. or battery isolation module disconnects my LifePO4 batteries before they are fully charged. I am not sure why, but I believe it is the different voltage and charge profile of the lithiums vs the lead acid. Sometimes they stay connected for hours until almost full, and other times they are disconnected after a short time. Either way, if needed, I just lock the dash house/chassis battery combiner switch until they at the charge level I want. I have seen no bad side effects from doing so.

Like 10 fan, I used a couple of clamp on amp meters to keep track everything. I didnít want to burn up an $800 alternator or buy expensive and unnecessary equipment.
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Old 05-13-2021, 10:56 AM   #5
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Quote:
Originally Posted by tqqest View Post
Correction on my earlier post, my Allegro Bus 45LP had a 240 amp alternator, my current DS4369 has a 210 amp alternator.

Also, some asked why the B.I.M. or battery isolation module disconnects my LifePO4 batteries before they are fully charged. I am not sure why, but I believe it is the different voltage and charge profile of the lithiums vs the lead acid. Sometimes they stay connected for hours until almost full, and other times they are disconnected after a short time. Either way, if needed, I just lock the dash house/chassis battery combiner switch until they at the charge level I want. I have seen no bad side effects from doing so.

Like 10 fan, I used a couple of clamp on amp meters to keep track everything. I didnít want to burn up an $800 alternator or buy expensive and unnecessary equipment.
I am looking to do the same conversion this yearÖor soon after. Where would you clamp on the meter? Is there a place that is easy to get to?

And did you ever think of getting a lithium BIM to help prevent any alternator issues?

Thanks
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Old 05-13-2021, 03:09 PM   #6
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Lipo batteries

richpatty,

In the test phase, I had the clamp on amp meter first on the charge cable right at the back of the alternator. Then I ran the coach with my lithium house batteries at about a 10% state of charge. I wanted to make sure I wasnít running the alternator too hard. Then I moved it to the cables at the chassis batteries. Finally, I moved it to the cable from the alternator right before it enters the 4 way splitter right at my lithium house batteries.

As I said, the cable length and size is limiting the amps that the alternator can send to my batteries. Frankly I am disappointed that I am only getting about 90 amps on average. I am thinking about upgrading the cable from the chassis batteries a couple of sizes to get more. My 210 amp alternator should easily be able to run more than the 75-110 amps average that it is currently putting out once the chassis batteries come back up to a full charge.

As for the lithium B.I.M., I looked at it but I was not interested. It is money that I didnít need to spend. One source said it only charges for 15 minutes and then shuts down for 20 minutes over and over again. Another said it will charge both for a max of one hour, and then will only reconnect if the house batteries are below 80% or 13.4 volts. With over 1100 amp hours of batteries, if my batteries are low, I need every minute of charging I can get while driving. Also, I am charging the batteries at 13.9 to 14.4 volts while driving.

That is why I am already manually overriding my current B.I.M. using the dash battery switch. I have driven 6 hours straight with the house lithium batteries connected to the alternator and have never seen any excessive amp draw or alternator temps. Nor have I had any issues with the current B.I.M.

As a plus, with the lithium batteries always at 13+ volts, I just hold my dash house/chassis battery switch (up or down position, whichever gives me the higher voltage) while running my slides in and out. No engine running, power hooked up, or generator needed. The voltage stays at 13 volts or more and the full wall slide never strains!
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Old 05-13-2021, 03:22 PM   #7
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Keep in mind that the alternator and its regulator likely will not bring LifePo4 batteries up to a 100% charge, a DC2DC charger will. However, that is not necessarily bad, many articles I have read indicate that less than a full charge will allow them to last longer, just something to be aware of.
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Old 05-13-2021, 06:28 PM   #8
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Interesting... As I also have wired a switch so I can run my front A/C to run off the inverter/batteries (still 8 Lead acid) with the solar and alternator helping out. I always was concerned that I would be overtaxing the alternator doing this. But maybe not?

I do want to swap out the 8 Lead acid for 8 lithiums. I am just tired of the corrosion, mess and maintenance. And doubling the AHs is a nice bonus.

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Old 05-13-2021, 06:36 PM   #9
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Quote:
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Keep in mind that the alternator and its regulator likely will not bring LifePo4 batteries up to a 100% charge, a DC2DC charger will. However, that is not necessarily bad, many articles I have read indicate that less than a full charge will allow them to last longer, just something to be aware of.
Hi craigav,

In my case, with the alternator pushing 13.9 to 14.1 volts to my lithium batteries, I can easily get them up to 90%. They can be charged up to 14.4-14.6 volts, which I would have to do with the generator or shore power, if I really needed every last bit of power. But with the amount amp hours I now have, I can easily go for at least a couple of days if they start out at 85%. 3 days or more if I want to take them down to 5%. Which is nice because it doesn't hurt them. I do my best to keep them between 20% and 80% as that is easy to do and seems to be their sweet spot.

You are right that lithiums do not like to stay at full charge for long periods of time, especially in high heat. They seem to last the longest if they are stored at a 40-60% state of charge. When I park for long periods of time, or store my rig at home, I set my Magnum charger to float them at 13.3-13.4 volts. That keeps them at about 65%. Then when I am on the road and boon docking, I set the charger to float at 14.0 volts and run them up to 90%.

Even though they take a little more management, I love the lithium batteries and will put them in any rig I get. Because I built them myself from a group order, and used Overkill Solar Bluetooth BMSs, I only have about $2,300 total in the 1,120 amp hour setup.
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Old 05-13-2021, 07:07 PM   #10
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Hi Tad,

I am in full agreement and have my setup similar to yours although I still consider it work in progress. I have a 40a dc2dc charger that I plan to install soon, but like yourself I prefer not to charge my LifePo4's up to 100% anyway unless I know I am going to need the extra capacity such as when I am boondocking. I am a bit more limited on the weight I can carry but I still have ~400 ah of LifePo4 capacity which with lithium batteries isn't all that heavy (comparatively speaking to lead acid batteries).

If/when I sell my RV and upgrade, I likely will take the batteries out before I even offer the RV for sale and then install them in my next RV. I suspect most people are not aware of the battery management you are speaking about, but with such management I suspect I can get 10~20 years out of my batteries. Currently my setup is with the stock converter that also is setup for lead acid batteries which also doesn't bring them up to 100%, more like 85~90% as you stated, although I have a separate 100a Lifepo4 charger that I can turn on whenever I want to get them to 100%. For me, the 400a (likely 300a usable seeing I don't charge to 100% and try to stop at around 20%), in any case that will last me 3 or 4 days, although I usually charge them some anyway when I start the generator for other purposes.

~Craig
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Old 05-13-2021, 07:27 PM   #11
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I used to think I didn't need a DC-DC charger either......after all I have a 260A alternator right???.......and it's only 1-year-old right????

So after about 12 months of charging our 840Ah battery bank with the alternator, even with 1600W of solar on the roof........... The alternator failed

It probably won't happen to you......Right???


In our case, it's all moot now as we upgraded t a 24V system with dual inverter/chargers and the only way to charge the house batteries while underway is Solar and our current DC-DC converter(s), 2 actually!

hope your alternator hangs in there............but to be clear charging the house batteries with the alternator is like driving your Toad at 6500 RPMs all the time......will it work? Yup it sure will, but for how long
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Old 05-13-2021, 09:10 PM   #12
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Quote:
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Hi Tad,

I am in full agreement and have my setup similar to yours although I still consider it work in progress. I have a 40a dc2dc charger that I plan to install soon, but like yourself I prefer not to charge my LifePo4's up to 100% anyway unless I know I am going to need the extra capacity such as when I am boondocking. I am a bit more limited on the weight I can carry but I still have ~400 ah of LifePo4 capacity which with lithium batteries isn't all that heavy (comparatively speaking to lead acid batteries).

If/when I sell my RV and upgrade, I likely will take the batteries out before I even offer the RV for sale and then install them in my next RV. I suspect most people are not aware of the battery management you are speaking about, but with such management I suspect I can get 10~20 years out of my batteries. Currently my setup is with the stock converter that also is setup for lead acid batteries which also doesn't bring them up to 100%, more like 85~90% as you stated, although I have a separate 100a Lifepo4 charger that I can turn on whenever I want to get them to 100%. For me, the 400a (likely 300a usable seeing I don't charge to 100% and try to stop at around 20%), in any case that will last me 3 or 4 days, although I usually charge them some anyway when I start the generator for other purposes.

~Craig
Craig,

I shed over 300 pounds off of my front axle by changing my 8 AGM batteries to the 4 Lithium. I too will swap the original AGM batteries back into the coach when I sell mine and reuse the Lithium set for my new coach. I thought about the DC to DC charger, but they are expensive if really big and would require a couple of them to charge my batteries in a 6-7 hour drive. Glad you are figuring it all out. They make my life easier when off the grid.
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Old 05-13-2021, 09:39 PM   #13
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Quote:
Originally Posted by paul65k View Post
I used to think I didn't need a DC-DC charger either......after all I have a 260A alternator right???.......and it's only 1-year-old right????

So after about 12 months of charging our 840Ah battery bank with the alternator, even with 1600W of solar on the roof........... The alternator failed

It probably won't happen to you......Right???


In our case, it's all moot now as we upgraded t a 24V system with dual inverter/chargers and the only way to charge the house batteries while underway is Solar and our current DC-DC converter(s), 2 actually!

hope your alternator hangs in there............but to be clear charging the house batteries with the alternator is like driving your Toad at 6500 RPMs all the time......will it work? Yup it sure will, but for how long
Hi Paul,

I am sorry to hear about your alternator experience, they are pricey beasts! I hate it when things fail. But are you really sure it was the lithium charge load that caused the failure, or was it just coincidence? I lost 2 alternators on my 2014 Allegro Bus in seven years, and was not using any lithium batteries at that time. If I had just added lithium batteries, I would have figured that was the cause. Especially the second time. Just bad luck though in my case. If I had been running lithium batteries, like you, I am sure that I too would have gone to a dc/dc charger just to be safe.

Anyway, I am not worried at all about the alternator on my rig. I checked with the manufacturer of the alternator and got the max working temp and other data. The alternator on my 2020 coach if a very different beast than ones even a few years old, and has several different protections built in. It will reduce the output on its own if the temps get too high. And as I stated above, I very carefully tested the alternator output and temperatures while it was running my max load of 160 amps. The customer service rep response was LOL when I asked if my alternator could run that level for several hours.

All this is why I always state that for ME, I am fine and feel no need for dc/dc chargers or a special lithium B.I.M. For others, they should test and make their own decisions. If they get the same results as I have, I don't believe that they will have any problems either.

Regards

PS I am envious of your solar, I have not added any yet, but it would be really nice!
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