I'll start the bees nest since that seems what I'm best at here. So, you install Lithium house batteries and want to insure that you don't smoke your alternator. What do you do? The majority of us here seem to want to install a battery to battery charger in between the alternator circuit and the house bank. Right?
Do you eliminate the isolator or not?
Simple question, right?
Go.
The Foretravel Duvac, Diode block house battery charging system is actually well adapted to supporting lithium as long as you keep battery capacity reasonable and you also consider other connected loads while driving, charging. The at rest voltage and with the proper charger or inverter/charger settings the boost system with the maintained switch can also be used to charge and keep AGM chassis batteries maintained. For my Nimbus I did drop in replacing 3, 210 A/H Lifeline AGM with 2, 300 A/H LiPuls. After seeing how well it worked, I added a 3rd. With the Victron battery monitor I see sometimes up to 140 amps during alternator charging. This works well with the 270-amp alternator. The charge rate tapers down to about 80 amps, and you can see when the batteries are fully charged the battery BMS turns charging off and the draw is .45 amps for the 3 batteries. This works the same way with the inverter/charger. I did upgrade the inverter charger to a Xantrex, 3,000 watts with 150-amp charger. I don't have a residential fridge so no load there. I have considered moving one of the ACs to the inverter but then some additional management is needed such as waiting for the batteries to be fully charged before turning on the AC.
My Nimbus also has the battery compartment in the center of the basement. The Oasis keeps it warm just being there so no problems with winter operation. If you would like some help with the details, battery sizing and stuff reach out. You may direct email
d23haynes57@hotmail.com or call, text, 631-897-0345. I have some 40 years' experience industrial and motive power batteries and charging. I can help you put together a value priced system that will work.
I replaced the isolator with a B2B. I was following those before me. Seems to be working fine and have had no problems since 2021. Probably have traveled 40k miles with this setup.
Had 2 Lithium pro brand house batteries for years with a delco 28s alternator and isolator,no problems,they have great advice and service,they have a booth at the tent at "Q".
I know where Woody is headed here so I will add the following info. Someone who is not familiar with battery management and is not a gearhead and has lithium batteries installed along with solar should he use the isolator or B to B?
Continue with the flames now.
There is not a one size fits all answer to this. If you have a 1,000 A/H battery bank and a 130-amp alternator you need current control. If you have other loads such as a residential refrigerator or using the Oasis while driving those loads also need to be considered. A 20-amp charger will not keep up with those loads and charger the batteries. If you have a 400-amp alternator and a 400 A/H battery bank, hook it up and let it go. The solution needs to be designed from the power to be consumed, the battery storage, and what is needed to charge them, and how long you want that to take. The design also needs to include charging from shore power and generator to make the most efficient use of generator capacity and minimize needed run time.
Lets add the fact of a original factory alternator on a 25 year old coach with lithium batteries added then. And the question was about protecting the alternator not about usage.
Protecting the alternator and also the related wiring and controls goes back to maximum load management.
Reply #4 "not familiar with load management".
Sorry about the delay in response.
For electrical system there needs to be some control of the loads placed on sources. For this discussion the alternator is the power source. When it is possible that there are loads where the power demand is more than the alternator can deliver then there needs to be some means to manage those loads. Same as when plugging the rig into say a 20-amp outlet. You will not be able to charge batteries, run a residential fridge and air conditioners at the same time. You have similar limitations with the alternator.
Using the alternator to directly charge lithium batteries is not that much different then charging AGM or lead acid. The main advantage of lithium is improved charge acceptance over a longer period of time and this can be harder on alternators running at max loads. The challenge is that batteries are charged with current, and the alternator is a voltage source, delivering as much current as it can to try to reach that set voltage.
How much current a battery can accept from a set voltage source will be a function of state of charge, the difference between the supply set voltage and battery apparent voltage, and the size of the battery bank. Typically for Lithium at a set voltage of 14-14.2 volts it will draw approximately 30% to 40% of the amp hour capacity of the bank. This is now a load on the alternator. As the battery charges this current will go down as the battery voltage raises. Lead Acid will raise very quick, and AGM will be next. These batteries should have charger designed to deliver up to a 25%, 4 hour rate. Lithium can go much higher.
So back to load management if your alternator is straining to charge the batteries maybe you need to turn off the fridge until they are charged is an example. Using DC to DC chargers is a way to control charging current. Note they are rated on output and when input voltage is not high enough, they will increase current in to compensate. A 40 DC-DC may pull up to 50 amps. DC-DC chargers like a regular battery charger should be sized for at 10% to 20% of battery bank capacity, especially with multiple parallel batteries. You also need to consider power requirements for heated batteries. At some point for larger banks and loads a larger alternator is the real solution. Another option is to have a means to switch the batteries, so they do not all charge at the same time. Load management again.
Hope this helps. Any more question please ask, and I'll try my best to answer.
Dennis
Woody and Crane Man currently parked less than 50 yards away here at the Lemon rally in Quartzite. In fact, Crane man spent several hours yesterday putting in a B2B Victron system in my coach. My eternal thanks to him and Tom. Will let you know how it works out but both these guys really know their stuff. Today is day one so will let all know as soon as I actually go somewhere so it gets a tryout.
I used a battery isolation manager from BattleBorn. Have used it for four years with no problems.