Sunday, February 24, 2019

Lithium Battery Upgrade

Since getting back home from Quartzite we've continued to stay busy.

Friends have stayed nearby in their RV's at Catalina State Park and we've had the luxury
of hanging with them, while using the house as a home base.

We took some nice hikes in the park

The 50yr trail in Catalina State Park
We got an annual pass so that we can enjoy all the Az Parks

This doesn't look like England.
5 couples and 5 dogs all spent some quality time in the desert.

The Gang on the trail.

We had some snow fall in the mountains.

We we arrived back home we found that our
 back yard landscaping had been completed:

A new look to the back yard
We had the gang over for a few get togethers and 1 birthday party

Happy Birthday Kevin
After a couple of weeks the group started to scatter and it was back to
just Kate, Me, and the doodles.

Then this past weekend, we had even more snow fall at the house

Snow on the Saguaro
Saturday morning I woke up to the falling snow.
It's a rare chance to get a different view of the Sonoran Desert.

Our house sits on the shoulder of the Tortolita Mountains at 2,600'.

Snow on the Tortolita Mountains

Look quickly and enjoy the view.
In the desert as quickly as the snow comes....
it goes.

Snow on the Catalina Mountains

And of course we have had endless great sunsets.

When the walls turn orange....    We call that the "sunset alarm",
we know it's time to go watch the nightly show.

The sunset alarm is going off!
And it never fails...

Another beautiful end to the day!

Lithium Battery Install in the PartyBus

The signature project during this time period, and one that many are interested
in hearing about are the batteries.

The post now gets technical so unless you are interested in hearing about
Lithium Batteries, Charging Profiles, and solenoids,  you can tune out till next time.

 I upgraded the batteries in the bus
to new LiFePo4 (Lithium Iron Phosphate) batteries.

I went with 5 Battle Born 100ah drop in replacements.

Each battery can discharge at 100amp continuous, or 200amps for 30 seconds.
In parallel wiring it is additive, so I have 500/1000amp capacity which is more than
enough to start the generator which calls for 450cca.

I went with 500ah because:

My existing bank was totally sufficient at 900ah.
That gave me 450ah of capacity (50% discharge) if needed
without drawing the batteries down
too far as to shorten their life excessively.

I preferred not to discharge the AGMs below 75%

I normally draw my batteries down 150-220ah by the morning.
That was 75% of my 900ah AGM bank and I needed to recharge them,
but I can easily double that amount with the lithiums without issue.

At the lower end of the Lithiums capacity curve, they still maintain most of their voltage
unlike LA which as the % of capacity drops, so does the voltage.
This means they can still deliver the power to start the generator at say 20% of capacity.

That means I can go thru some cloudy days and still not need to start the generator.

While the Battle Born Batteries are called "drop in"  there still are a
few minor modifications needed.

I had to replace my Charging Solenoid (battery interconnect) and change the charging
profiles on my Magnum Charger and my Solar Controller.

They arrived 2 days after I placed the order in perfect condition.

5 Brand New 100AH Lithium Batteries

First off was the replacement of my existing charge solenoid.

The Charge solenoid will connect the Chassis and House banks when the alternator
is running, allowing charging current to be directed to both banks.

When both banks are of a similar chemistry this is not a problem.
The lithiums however, with their almost unlimited charge acceptance, will draw so much power
from the alternator, that they could cause it to over heat.

Unlike Lead Acid batteries which accept less and less power as they charge up, 
LiFePO4 will accept 100% of the alternators (or other source) output until they are fully charged.
This means that they will charge much faster than L.A. batteries.

To solve this, I replaced the existing Charge Solenoid with a specialized
Lithium Battery Isolation Manager.

The LI-BIM-225 will supply current to the house bank on a timed schedule, 15 minutes
out of every 35 minutes, and continuously monitor both banks voltage.
It will connect and or isolate as needed.

It still can serve the same function as the original solenoid ie: the emergency
cross connect can be used to supply power from the house to the chassis
batteries in the case of a dead chassis (starting) battery.

Diagram how I wired my BIM
The ignition switch side of the BIM shares that post with power to the slide solenoid.
In my coach, the ignition needs to be turned on to operate the slides.
The slide solenoid gets it power from the ignition switch from the post that it shared
on the charge solenoid.

Here (below) it is wired into the spot previously occupied by the charge solenoid.
The large cable on top goes to the house bank and the large one on the bottom
goes to the chassis bank.

Under the appropriate circumstances both the large cables would be connected
to each other via and thru the BIM

Rats nest wiring: Courtesy of, and typical of, Tiffin Motorhomes

Second on the list was some modification to the battery compartment.
Since the lithiums do not give off gas - there is no need for ventilation.

They are also more particular to temperatures.
The built in BatteryManagement System will not allow them to accept a charge
 below 25°F so I wanted to close off the compartment and install some insulation
on all outside surfaces to try and moderate the temperatures a bit.

Insulated Battery Compartment and Battery Tray

Insulation installed, and .25" plywood base for the batteries to sit on.

I needed to make up new interconnects due to the new layout.

2/0 Interconnects

Here they are wired up

Batteries set in place

Finally, some wood blocks screwed to the plywood base to prevent side to side movement,
and tie downs installed.
The batteries are now solidly in place

Secured and ready to go

The battery tray is slid back in, it now has almost 425 lbs less weight
sitting on it.

Storage Solar is attached to provide power while in covered storage

Lithium Batteries do not require multi step charging.
Simply charge them at maximum current up to 14.4v, then hold that voltage for
20 minutes per cell for a balancing charge and you are done.

I set my Magnum for 14.4v absorb and 100 minutes.   Float was set at 13.4v.
Float charging is not needed for Lithium Batteries so I set the float charge
at the batteries resting voltage of 13.4v.

So, when charging the batteries will take maximum current until they reach 14.4v
at which point they are full.   
Then 100 minutes of balancing charge at 14.4v (the old absorption stage)
and the charging devices either go to standby, or a 13.4 "float".

Temp compensation is not needed, and could actually cause the BMS to disconnect the
charge source due to excessive voltage, so it needs to be turned off.   
On the Magnum, I needed to disconnect
the Temp Sensor to disable Temp Compensation.

My Solar Controller was set with similar parameters. 

In all cases, Equalization is either turned off, or limited to 14.4v.

Once everything was hooked up I started the generator to take a look as
what the charge cycle would look like.

The batteries were only down about 30 ah (per the Magnum BMK)
so I did not expect to bulk charge for very long.

Generator is first turned on and registers 100amps charge rate at 14.3v

In a few minutes that settles in to a balancing charge at the maximum
charge voltage of 14.4v.

These batteries are quite expensive so why did I make the switch?

First was a lifestyle choice:

We dry camp extensively.
Being able to run our batteries down to 10% and leave them partially charged during long
periods of dry camping means even less need to run the generator.

No worries about getting the batteries back up to full charge after each cycle.

The high charge acceptance means that I can accept 100% of my solar output back into
the batteries all the way back up to 100% full charge.

With my AGM batteries, I would get a big jump on recharging early on during bulk charge, but
once I went into absorption phase I would only be using a diminishing %
of my solar output for hours on end, as the bank slowly finished recharged.

The rest of my solar potential went unused.

Many days by 1pm I'd see 20 amps or less going into the batteries,
with 50 amps or more of potential solar charge not being used since the batteries
would not accept a charge any faster.

The LiFePo4's will accept all that I have on board till they are full!

The 400+ lbs of shedded weight off of the bus will be a huge plus.
Don't tell Kate.... she'll do more shopping!

Supposedly they have a much much longer life span.
Time will tell on that one.  Fingers crossed.

I'll reserve final judgement till we spend this summer in Alaska and get to put them
thru a full season.   I'm looking forward to tweaking the systems and putting them to the test.