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Topic: Battery Replacement Questions LiPo (Read 392 times) previous topic - next topic

Battery Replacement Questions LiPo

I am planning on replacing the House Battery with some LiPo batteries with a BMS. These are sealed and have been used in high power applications. The Batteries have all been tested as good. The issue that I have is that the batteries are 3.7v ea. I can series them with 4 batteries to get 14.8v nominal. Charging them to a full charge is 16.8v. I plan on charging them to 16v normally to keep them at 80% charge. if I discharge to 20% this will give me around 1050AH of capacity.

The issue for me is the Higher voltage. What items on the coach will not be able to handle the higher voltage? The lights (mostly LED) should be able to handle it, but I'm worried about the Fridge (Dometic Royal RM4804)  on 12v and the std 12v circuitry for the eng battery side of the coach. Am thinking of keeping the Eng side lead acid. I realize that this may need a DC-DC converter to keep the eng battery topped off. Also plan on installing a Magnum MSH3012RV as it can charge to 16v. Tips on how to do this and any pitfalls appreciated. I am electrically knowledgeable a have resources that know these batteries. Thanks
1995 U-240 GrandVilla 36'
FMC# 18675
Lookingglass, OR
"There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." - Ed Howdershelt Abintra Press "If you have to lie to gain Support, you are not worth Supporting" "I just want to go somewhere where there's chocolate and nobody talks." - Ynez Reinschmidt

Re: Battery Replacement Questions LiPo

Reply #1 –
Most LiPo batteries are 3.2 volt you are going into uncharted waters with 3.7 volt
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Battery Replacement Questions LiPo

Reply #2 –
Would you be able to install a voltage regulator that would keep the output voltage at a lower voltage where you would not have to worry about anything that is connected not likening the higher voltage?
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Battery Replacement Questions LiPo

Reply #3 –
Need more info on your batteries. If you have the option, you may consider running at 24v and having a step down voltage regulator like an Orion by victron to run all of your 12v applications.

As a consideration, I am running tesla batteries that have nominal 3.8v and a max of 4.2v per cell x6 cells or 25.2v. I don't run them this high and have an Orion going to the original AGM house batteries. This allows large loads like 'boost' to be used but I'm able to recharge the house batteries with the orion from my lithium bank. In order to charge to the specific voltage required for the tesla batteries, I use Victron charge controllers and multiplus.
1999 U320 WTFE #5586
2014 Subaru Forester 6sp
4000 watts of solar
650 aH @ 24v

Re: Battery Replacement Questions LiPo

Reply #4 –
I had not considered running 24v. Will need to look at the Victron to see the specs.
Here is the spec sheet. I have 72 of these to run in series parallel as well as the BMS to manage them.
I plan on running them at 80% SOC that would be 15.6v for a 4 in series or 23.4v for 6 in series. I could run 7 at 27.3v and only use 70 cells. The magnum will charge up to 16v which would be about 90%SOC. it will accept up to 17v so I could top the batteries off externally occasionally. 100% is 4.2v/cell.
1995 U-240 GrandVilla 36'
FMC# 18675
Lookingglass, OR
"There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." - Ed Howdershelt Abintra Press "If you have to lie to gain Support, you are not worth Supporting" "I just want to go somewhere where there's chocolate and nobody talks." - Ynez Reinschmidt

Re: Battery Replacement Questions LiPo

Reply #5 –
Is there a reason you want to keep them at 80%? So, from reading the documentation, the range is 2.7-4.2. With 4 cells, that's 10.8-16.8. With 7 cells, 18.9- 29.4. 7 Cells would be The right amount for a typical 24v battery. A victron multiplus or quattro will run 19v-33v, so you can pretty much utilize 100% of your battery that way. The Magnum 4024 works from 18-33.6v, so that one could work as well.

Unfortunately, those particular cells aren't great for 12v because of the higher voltage. They'll work, but you won't be able to utilize them to their full capacity.
1999 U320 WTFE #5586
2014 Subaru Forester 6sp
4000 watts of solar
650 aH @ 24v

Re: Battery Replacement Questions LiPo

Reply #6 –
was looking at 80% due to the 12v range. but also, 72 cells would give me around 1050AH capacity at 80%. if I can go to 100% it will be 1350AH. even 1050AH would be more than enough capacity and at 80% the cells should last almost forever. I'm going to look at the 24v options. I would need to add a DC-DC converter unless there is the capability within the converter to output 110v AND 12v.
Thanks for the feedback.  7 cells in series per 24v block makes sense and would give me 70 cells at 750AH @ 24v. 
1995 U-240 GrandVilla 36'
FMC# 18675
Lookingglass, OR
"There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." - Ed Howdershelt Abintra Press "If you have to lie to gain Support, you are not worth Supporting" "I just want to go somewhere where there's chocolate and nobody talks." - Ynez Reinschmidt