-
LiFePO4 “Drop in”
I know there has been much debate and research on this subject. I found a company in california that does LiFePO4 with built in battery management. What I wanted to do, was pull out my lead acid, slide in these LiFePO4 and call it a day. I was going to use Tesla cells, but didnt want to monkey with 12/24 volt issues since Tesla are ONLY 24v.
Here is where I ended up http://specializedpower-net.3dcartstores.com
The batteries will be here end of the week. Im going to do a full write up/video of the swap and post.
I will be keeping my 2 Xantrex 2500 inverters.
-
20 Replies
-
I have switched from AGM to Li.
It has been an eye opening learning experience and isn’t cut and dried and certainly was not a simple drop in switch.
If you add your coach information to the signature line your experience will have greater meaning to our members, some who have already made the switch.
Despite being described as “drop in” Li batteries have enough differences and nuances that make them fantastic in some respect, but not an easy trouble free switch in others.
http://www.prevostcommunity.com/PDF/Relion%20Final%2024%20volt%20Installation.pdf
-
Since you have no signature, I assume your coach is 24v. Be sure to confirm the batteries will not have a balance issue when hooked in series.
-
What Jon said…
Interesting article about charging Li-on’s from the alternator. Something you may want to be aware of if you hadn’t already considered it in your setup.
https://shop.pkys.com/Alternator-Lithium-Battery.html
Just had ETLC make the change to LiFePO in BoB (our Big ol’ Bus). We’ll see how things work out going forward, but saved a bunch of weight and space with the change initially.
-
My house is 12v, Chassis is 12/24. House batteries are in parallel. When you say 24v coach, are you referring to the house, or chassis?
-
We got it now Dave, being a CC it’s 12v and much easier to deal with. Mike just did the same thing you’re doing except using RElion, you guys should compare notes.
Mike – Keep us posted, very interested on how your conversion went and the operational differences as you go forward. This is going to be the norm one day and as we move forward as a group, the learning curve will be priceless.
-
So, these arent going to just drop in. The voltages offered on the Xantrex freedom 458 inverter are not in my opinion close enough to the manufacture requirements to charge the lifepo4 batteries. Batteries are here! Exploring inverter options now. Batteries want 14.6 charge and 14 float, inverter only offers that at 50 F, and Arizona is never 50 where I live…. Old inverter charging table pictured below. Here is me removing 6 of the 8 (2 were already out) house batteries in 27 seconds because im VERY fast.
-
Read the charge voltage levels for your new batteries.
Read the information for Li batteries about current levels at 32 or below, or above 32.
The chart show may be applicable for lead acid or AGM batteries, but only the Li manufacturer’s charging specifications are valid for those new batteries.
-
Some of you may have followed my five part article on Li battery substitution in Bus Conversion magazine. I am working on a follow up using quite a different approach for 12vdc house batteries by swapping out only half the existing lead acid house batteries and adding an equal number of Li batteries to create two different house battery banks separated by a large amp combiner. A separate inverter/charger is attached to each house battery bank. High amp draw loads (refer, appliances, etc.) are taken from the Li side and low amp draws (LED lights, flat screen TVs, computer charging, etc.) are taken from the Lead Acid side. The large amp combiner isolates these two when no charge current is present. When a charge current is present the combiner isolates the two house banks so the risk of one bank discharging the other is minimised.
The existing 12vdc alternator can be used while driving as when the BMSs in the Li house battery bank shuts off charge to those batteries the alternator output is absorbed by the lead acid batteries so there is no voltage spike. The inverter/chargers handle charging via shore power or gen power. This may result in slightly over charging the lead acid bank when in float but that will do little if any harm. Two separate MPPT solar chargers are used to keep both banks up when in appropriate sunlight. When the Li batteries reach full charge all the charge current from both MPPT controllers is directed to the lead acid bank so it may eventually become fully charged as well with enough time/sunlight.
While you only achieve half the weight savings, you do so with just half the investment and you don’t need a bunch of new electronics to handle the differences between the Li and lead acid battery characteristics – at least on paper and in design consultation with one of the leading Li drop in replacement battery makers. We will see how things play out in practice.
This approach is only appropriate for coaches with totally separated house and chassis battery banks as you are only dealing with the 12vdc house side only and not impacting the 24vdc chassis side. I will keep you posted as this goes forward.
Jerry
-
When you are considering lithium batteries of any chemistry alphabet, they all stop accepting a charge, shut down by the BMS (battery management system) between 112 and 118 f, depending on the chemistry. When the batteries are working they will generate heat. the more you are drawing or charging as a % of capacity the more heat they generate. It is not uncommon the be 30 degrees or more above ambient. You need to either ventilate the compartment very well with fans or air condition the space.
Example, it is 100 degrees in AZ you are parked on asphalt which is 110. 5 degrees of heat from working shuts the charging off.
Temperature is the Achilles heel of LI batteries.
Everything is a trade off
-
I spent a lot of time speaking to Relion engineers and they are aware I sealed my Li batteries in a compartment with no ventilation but with a heater to never allow the compartment temp to drop below 40.
Since Li is all new to me I have been continuously monitoring them and so far they are doing very well with my unaltered alternator charging, inverter charging using AGM settings, as well as being able to monitor the battery compartment temps.
-
Im picking up a Magnum inverter this week to replace the xantrex, going from dual 2500 watts to 1 2800 watt. If I find the usage is to high for one, I will add a second.
1999 XLV X-6872, liberty #440 -
So do we have a stable solution to adding lithium batteries to our coaches, even the 12/24 volt systems in liberty elegant ladys
-
Yes, but it involves a little change.
First, isolate the 12 and 24 volt cables going from the batteries no in place to the electric compartment. There should be 2 24V cables and 1 12V cable.
Install 4 24V 100 AH 8D LiPoFe4 batteries connected in parallel. You can use all of the existing short jumper cables and may need to add one or two more.
From the batteries connect to the 24V cables that go into the electric compartment. Then connect from the batteries 24VDC to 12VDC converters or reducers.. They are connected in parallel with each other and connect to the 12V cable to the electric compartment.
Depending on how and where you use the coach you might have to consider if you need to enclose the batteries in a compartment that can be kept above 32 degrees, or if you choose develop a procedure to revise the charging current to the battery manufacturer’s allowable current.
http://www.prevostcommunity.com/PDF/Relion%20Final%2024%20volt%20Installation.pdf
-
I “finished” the install tonight! Still have to seal off the battery box from the road, repaint black and gray, clean up wires, etc… but it was inverting, now its charging overnight. I ended up leaving one of the Xantrex freedom 458 inverters even though it wont properly charge the batteries, it can still invert from them, and added the Magnum 2800 to invert and charge. I have the charge on the xantrex turned off. Ill probably end up replacing the Xantrex in a few weeks anyways. I will update the thread after cleaning up the install, then again after the first dry camp.
lifepo4 batteries 200ah each : $1250 x 4 = $5000
Inverter MS2812 with remote : $1900+/-
Total cost so far $6900 + about 4 hours of my labor. If I didnt do this myself, I would have Bordur coach in San Tan Valley AZ do it. That is also where I bought my inverter.
-
Who is the battery manufacturer and what is the group size?
Log in to reply.