Can I have LiFePo4 as House batteries and Lead acid as Chassis Batteries?

[Dynasty_09]

Hi everybody,

In my Monaco Dynasty Yorkshire 2009, I replaced my 4 big AGM 6 volts house batteries (They were 400A each for a total of 400A of usable power) by 5X170A Renogy LiFePo4 batteries (Total usable power of 850 amps).

I also replaced my solar panels and controler (Heliotrope HPV-30DR) by a Renogy Rover LI40A Charge controler.

I had to replace the Magnum remote controler to accept charge rates for Lithium.

Now my questions are:

• Can I keep the chassis Lead acid batteries since the BIRD is bridging both batteries and the Lithium are charging at 14.4 volts?

• If not, is there a Lithium battery able to crank my ISM engine (I need 1800CCA)?

Thanks in advance for your help and have a great day!

[Isaac-1]

You will need to disable the BIRD and probably install a DC-DC charger to charge your LiFePo4 batteries from your engine alternator in order to prevent the sustained high amp draw of the LiFePo4 batteries from killing your alternator.

[twinboat]

With disabling your BIRD, you will need a battery maintainer to keep your chassis batteries charged while on shore power.

[Rocketman3]

The lithiums are not going to be able to start the big Diesel engine. The lithium’s bms will shut down and off (at 100 amps per battery? - check your battery specs).

You need to disable the Bird. If you can figure it out put a manual switch in so if your chassis battery needs some extra juice - you can hit the switch & give it the juice. Think very fast charge…

I believe some people change out to the Blue Sea ACR and set it for manual.

You need to be careful and treat those lithium’s right or they will die an expensive death.

FYI - I have Lithium’s for my house and AGM Lead for the chassis. It can work. There is no direct connection beteeen the two batteries. I have:
1. Victron DC-Dc charger to charge Lithium’s from the alternator.
2. (Original) a charger that charges the chassis from the house. LE415 Lambert.
3. (Original) A boost solenoid - manual operation.

Good Luck!

[windsorbill]

Couple options you can do, depending on your situation.

If you leave the BIRD in place, you'll likely burn out your alternator. It needs to be disabled. As mentioned, you can install a DC to DC charger to charge them from the ISM.
or,
You could also relay only on solar when not on shore power or generator to charge your batteries.

LiFePO4 batteries are not designed to start a big diesel. Most are rated at only 100amp draw/battery. Not even close to your 1800 draw required to start that ISM. Stick with the starting batteries you already have.

[Timaz]

Originally Posted by Dynasty_09

Hi everybody,

In my Monaco Dynasty Yorkshire 2009, I replaced my 4 big AGM 6 volts house batteries (They were 400A each for a total of 400A of usable power) by 5X170A Renogy LiFePo4 batteries (Total usable power of 850 amps).

I also replaced my solar panels and controler (Heliotrope HPV-30DR) by a Renogy Rover LI40A Charge controler.

I had to replace the Magnum remote controler to accept charge rates for Lithium.

Now my questions are:

• Can I keep the chassis Lead acid batteries since the BIRD is bridging both batteries and the Lithium are charging at 14.4 volts?

• If not, is there a Lithium battery able to crank my ISM engine (I need 1800CCA)?

Thanks in advance for your help and have a great day!

The short answer is yes as I do and I have not disabled any alternator charging. But I am careful to charge the batteries up a little over 90% before I start the engine so the alternator really doesn’t work very hard for very long. I’ve only seen my 200 amp alternator putting 75 A max into the lithium batteries. But if you don’t want to do what I’m doing you can wire in a DC to DC charger.

Tim

[Persistent]

The general rule is "do not charge batteries of different chemistry on the same charging circuit". They have different charging profiles. See battery manufacturer's specs.

Do use lead acid batteries for chassis start batteries. Even a Tesla has a lead acid battery.

As posted above a large lithium battery bank can destroy many engine alternators. This usually does not happen if you have a large enough lead acid chassis battery. It may depend on how things are wired.

The voltage spike the alternator generates when the Li BMS disconnects can fry the alternator winding insulation. This link explains it better than I can.
https://marinehowto.com/drop-in-life...ated-consumer/

[153stars]

Like older weaker jump packs it might take time to recharge start battery. The boost could be used to recharge the chassis batts enough to restart the diesel. The lifepo4 batts won't be resting at 14.7 v so charge to chassis might be at 100amps tops and would drop as chassis batts got higher. The auto combine from chassis is usually disabled like mentioned.

[Dynasty_09]

Wow,
A bunch of good stuff there and you'll certainly saved me a lot of money.

I'll disable the bird asap and install a dc-dc charger. Renogy seems to have good one.

I was thinking of installing a manual switch to bridge them if needed.

Thanks again, excellent knowledge base on this forum. A lot better than Google can provide.

P.s. Since the batteries are always bridged when unhooked from the wall. Wouldn't the Lithium try to equalize with the lead-acid and bring them down faster than expected???

Sent from my Lenovo TB-X505F using iRV2 - RV Forum mobile app

[Isaac-1]

You don't want them bridged for a number of reasons, but no the Lithium's will not drag down the lead acid batteries in most situations, since across most of their discharge curve they would be at above the 12.8VDC of a fully charged lead acid (12.8VDC is about 17% SOC for LiFePo4).


Note the DC-DC charger I have is a Renogy model, which also includes an MPPT solar charge controller, and provides back feed charging for the Lead Acid starting battery once the Lithium is topped off. It is not perfect, and has a few annoying traits like limiting alternator input to no more than half its 50 amp capacity if there is ANY solar input. In other words it is a 50 AMP DC-DC charger, that will only draw 50 amps from the alternator when driving at night, in the daytime even in early morning cloudy weather where it is barely making 1 amp from my 400 watts worth of solar panels it will charge at 26 amps, 25 from the alternator and 1 from the solar panels. It also limits Solar panels to 25VDC which means you can't string them in series like you can with most other good MPPT solar controllers. Overall nice in theory, but I sure hope they fix these flaws with the next version.

[HarryStone]

I use a magnum smart battery combiner instead of a dc to dc converter. Works great

[Isaac-1]

A smart battery combiner can't boost input voltage a good DC-DC charger can, this way you can charge your Lithium batteries without overcharging your lead acid.



For example on my Renogy DC-DC charger the alternator can be putting out 14.0VDC charging the mostly charged lead acid starting battery, yet the DC-DC charger will boost this to 14.4VDC for charging the LiFePo4 battery.

[Dynasty_09]

Originally Posted by Isaac-1

You don't want them bridged for a number of reasons, but no the Lithium's will not drag down the lead acid batteries in most situations, since across most of their discharge curve they would be at above the 12.8VDC of a fully charged lead acid (12.8VDC is about 17% SOC for LiFePo4).


Note the DC-DC charger I have is a Renogy model, which also includes an MPPT solar charge controller, and provides back feed charging for the Lead Acid starting battery once the Lithium is topped off. It is not perfect, and has a few annoying traits like limiting alternator input to no more than half its 50 amp capacity if there is ANY solar input. In other words it is a 50 AMP DC-DC charger, that will only draw 50 amps from the alternator when driving at night, in the daytime even in early morning cloudy weather where it is barely making 1 amp from my 400 watts worth of solar panels it will charge at 26 amps, 25 from the alternator and 1 from the solar panels. It also limits Solar panels to 25VDC which means you can't string them in series like you can with most other good MPPT solar controllers. Overall nice in theory, but I sure hope they fix these flaws with the next version.

I was more thinking the lead-acid would drag the Lithium down. Does it make sense?

Sent from my Lenovo TB-X505F using iRV2 - RV Forum mobile app

[Isaac-1]

Yes, and that is an issue, though not one that will keep your engine from starting when you get done dry camping.