[Jon]

While the use of Li and AGM may be made to work, the question is why?

If 2 Li, (or 3 if desired) works why waste time, energy and complexity to screw with AGM batteries? I know Li cannot be economically justified, but we Prevost owners do a lot of things than may not make economic sense. This is especially true for a Liberty which requires removal of the entertainment center just to be able to see the batteries so anything that eliminates the need to screw with the shorter lifespan of the AGMs is a huge plus.

[Jon]

Good question, Jon, for which there are several good answers.

First, one can use the AGMs for a much longer period of time if they are freed of trying to also power the 120vac loads through the inverters. The voltage on Lead acid batteries sags so badly under such a load that the amp draw is higher and some appliances will suffer. Li batteries do not sag nearly as much powering 120vac loads through an inverter so amp draw remains lower and some appliances will run better and live longer as a result.

Second, by leaving some of the lead acid batteries in place and using a BtoB charger to allow the existing alternator to also properly recharge the Li batteries there is no need to alter anything in the existing house battery charging design or implementation like you have to do if you go to all Li. If a voltage spike occurs when the battery monitor on the Li batteries suddenly shuts off the fully charged Li battery with the alternator still turning, the Resistance in the LA battery will absorb that spike without potential harm to the rest of the system. No re-engineering required.

so, the owner benefits from being able to extend the life of their existing LA batteries with no need to alter what they already have other than the simple installation of a BtoB charger to keep the Li batteries properly charged while driving and an inexpensive standard RV converter/charger to keep the LA batteries charged while on shore/gen power. Much simpler for most older buses than having to reengineer everything to match the recharge profile of Li batteries while driving and while on shore/gen power.

With the prices of high quality Li batteries falling so rapidly it is cost effective to gain the benefits of Li rather than simply replacing the existing AGMs with new AGMs in older busses. My take, anyway.

A much more expansive discussion of the many benefits of keeping some of your LA batteries to power just the 12vdc loads and adding new Li batteries to power just the 120vac loads through your existing inverter/charger(s) is contained in the articles that I wrote that have already appeared in Bus Conversion magazine and the follow on article that will appear in the next edition.

Jerry

[Jon]

I don’t doubt you are correct, but if you do not mind stretching every amp hour of service from your AGM batteries it is important to you.

It is not how I manage my coach, evident by the fact I set a life limit on a lot of my bus components such as 10 years for air bags and 5 years for AGM batteries. I realize I sit at one end of the scale and others that use components to failure are both right. If you can open a bay door and see and touch batteries having an AGM in your system makes more sense than a Liberty in which it takes an act of congress to see or measure the condition of house batteries because the entertainment center needs to be removed.

[DON]

I found a good article on the net that jtjoint/Jerry Work wrote for BCM. Thank you Jerry. It is very helpful & educational. For others thinking about switching, here is the link: LINK

[Jon]

And here is another good article Jerry wrote on BMC about switching to Lithiums: LINK

[Bernie]

Good article by Jerry, the only thing I didn’t see was low temperature charging and the need to keep the batteries warm, although I might have missed it.

[Jerry]

Free advice: If Li batteries are installed it not only is a requirement to keep the batteries warm, or have the ability to seriously limit charging current, but it should be automatic. By making it automatic the potential to forget and destroy a set of very expensive batteries is possible and maybe even likely.

Li batteries are an incredible improvement over all other types but their drawback is use in cold temperature environments requires significant changes in how they are charged or keeping them warm (above 30 degrees F).

[Jeff]

Keep in mind that different Li chemistries tolerate charging at different low temps so it is somewhat manufacturer dependent. One way to handle low temp charging is to place the Li batteries in the living portion of they coach. If you are warm enough to travel, so are the Li batteries. Another is to rely on the auto on feature of most Webasto implementations. I rarely travel when it is really cold, but I do keep my Webasto set to come on and protect the water tanks if parked where it might freeze. That will also keep the Li batteries warm enough if they are mounted in the bays. The no charge while freezing referenced is cell temp below around 28F, not ambient. Most modern battery management systems built into most modern Li batteries have a low temp cut off anyway so the BMS will prevent charging if the battery cells are at too low a temp. They will deliver power just fine at much lower than freezing temps.

‘Jerry