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LiFePO4 Conversion
Looking to crowd-source some ideas:
When my AGMs aged-out I decided to do a lithium upgrade. Original configuration was four 8D Lifelines and two Xantrex 458s. New configuration is a single 320ah Lithionics with internal BMS and heater and a single Xantrex Pro3000.
I have a LTV Unity-MB on order and the Lithionics/Pro3000 is a popular DIY upgrade to run the roof air off battery to keep pets cool – say doing on-street parking downtown to grab lunch. I figured I would use the same config on the bus to get some experience.
My big headache is the alternator charging circuit. On my CC, I have a 12V oil-cooled 50DN dedicated to the house (zero interconnection with the 24V chassis batteries). CC ran two 2/0 cables (instead of one 4/0) from the alternator to the battery bay.
Lithium batteries have such low internal resistance (as low as 3 mOhms) that even with 30-some feet of cable they could try to pull say 1,000 amps from the alternator. Victron has an interesting video showing a bench test of an alternator being smoked at lower RPMs and apparently many builders use temperature sensing regulators.
The most widely used solution I have seen uses a DC-DC Charger as a current limiter between the alternator and lithium battery. The alternator charges the lead-acid chassis batteries and the DC-DC charger (say a 60a Victron) connected between the chassis and house charges the lithium.
So on my setup I tried to use a Victron unit in between the 50DN and the Lithium (No lead-acid in the picture) as a 60a current limiter. Nothing. Zero voltage from the 50DN. Did some digging and I think the issue is that the 50DN Voltage regulator does’t see a battery (a 12V signal) so doesn’t output a charge.
I know the club has a lot of smart owners and builders so ideas welcome!
BTW, I find it way cool to use the BMS app on my iphone and monitor the battery (especially the time-to-empty at current draw). Sadly won’t work on Jon’s flip phone 🙂
Attached is a screen shot during my first stress test (making 6 cups of coffee) which took 5% off the charge.
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8 Replies
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Isn’t a single 320 amp Lithium a little light for your coach? If you had 4 Lifelines that would be 1020 amps at 50% or 510 amp hrs usable. Lithionics was a good choice.
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I only dry camp once or twice a year and other than watching TV, the big load is my wife making coffee and toast. I could have used an 8D lithionics (600 some aH) but $10K is crazy. I wish I could run bedroom roof air on battery but that would be a major re-wire on the coach.
I am impressed that Lithionics is UL certified as that isn’t easy.
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You are correct, you need a connection to a battery for the alternator to work. Instead of using the victron charger, have you looked at the Wakespeed WS500 alternator regulator? Search on youtube for “Camp Prevost”, where he has installed one of these. I intend to go the same route when I do my lithium conversion.
Jeff and Lindsay
91 Marathon XL -
Over the last couple of years I have written a series of articles for Bus Conversion magazine on a safe and cost effective way to make such a conversion. I used my CC as the implementation vehicle. A final set of articles will be in the next two upcoming editions. Two of the newest 400 amp hour Li batteries in a slightly larger than 8D form factor will serve you well for your intended use. One might turn out to be a bit light, as Tom suggests.
Some of these new generation, large capacity Li batteries show exceptional build quality, like the one I feature in the upcoming articles. I like the stainless steel cases, internal automatic heaters, very high quality BMSs and bluetooth battery monitors all built in for a very reasonable price. You can install them in the same battery rack CC used for the LA batteries when built without issue.
For your current alternator to work, you need to leave one lead acid battery in the system with the alternator connected to it so the alternator and voltage regulator will think they are still charging the same LA batteries they were designed to do. Use one or more B-to-B chargers between that lead acid battery and your Li batteries.
The two cables used by CC from the alternator are easily accessed at the back of the black panel between your two inverter/chargers. Use one or both in parallel. The current crop of B-to-B chargers will limit the amp draw to well below what one of those cables can handle so no issue there. They also will automatically isolate the LA and Li so no issue there, either. Easy, fast and safe. Paralleling two or more B-to-B chargers simply allows you to recharge faster if you think you need to.
The latest B-to-B chargers also feature a MPPT charger built in if you ever also want to also use solar recharging.
CC made all of this easier since they wired for two battery banks (paralleled) and two inverter/chargers with isolated house and chassis batteries from the factory. Also behind that black cover between the two inverter/chargers you will find the cables that run to the house 12vdc circuits and the one running to the LA gen start battery. You can run the house 12vdc line to one of your new Li batteries, but do not connect the LA gen start battery to the Li banks without a B-to-B charger to isolate the two. Connect the gen start battery and its “boost” circuitry to the one remaining LA battery instead.
Jerry
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Hi Group,
I replaced the 23 yr old fridge with a 17 cf frigadaire which seems to draw much less when inverting which was a big daily draw on my 6x8D Lifeline bank which was 2.5 in use. I replaced the 6 with 4x 200a Amperetime LiPo4.I have a 97 Royale with DN50/12v to an adj regulator (used with the AGMs) which direct feed the LiPo4 bank. What a difference there. 100% charge from 50% SOC during our average 4-5 hours on the road. I always had to charge the AGMs after stopping for the night.
I have 2 Magnum 2812s which charge the LiPo4 bank. They are set at a 14.6v / 150amp max charge rate when both chargers are running, 75amps when 1 charger is going. Custom settings not CC/CV. From 50% SOC full blast I am 100% SOC in 1.5 hr of charging. Much less generator run time to charge, which is a big plus and 600-800watts of portable solar panels will now be useful.
I spend last week traveling with nights in the teens and 20s. I have no heaters in the batts or the bay. My Aquahot ran with all zones on, I could get up at my 5am and make coffee, and I held off running the generator just to keep enough voltage to keep Aquahot happy and me warm and anger free.
I am impressed so far, when we need A/C in the heat….I run the Powertech. The only other addition to the 12v bank was 1 Magnum BMK monitor. It gives me the accurate numbers needed to monitor the LiPo4 system. So far after tweeking the chargers for my use….HAPPY CAMPER!
JONATHAN
1997 XL40 ROYALE #201
Homol’ovi SP, Winslow, Az……right now.
(I cant get a pix to post with my profile…) -
My current house battery set up is as follows.
Two Xantrex Freedom 458 2500w inverters (new 2 years ago)
Four Lifeline GPL 4DL AGM 200 amp hour 12v batteries (older batteries not holding charge for more than 6 hours)
I want to upgrade my house batteries to lithium batteries without replacing the Xantrex inverters since they are working and relatively new.
I know there are some very experienced owners in this community that may have some ideas on how I can make this upgrade. All suggestions are welcome.
My coach is a 1997 Prevost Royale XL45, series 60 DD with a 50DN 12v oil cooled alternator for charging house batteries while driving.
Do I need to be concerned about protecting the alternator while charging lithium batteries while driving?
The lithium batteries I am interested in replacing the AGM batteries are 4 Weize 12v 200 amp hour batteries. Same form size and configuration for drop in replacement. Weize states that my current Xantrex inverters charging protocols for AGM batteries will work with their lithium batteries.
Let’s suppose I drop in these new lithium batteries and do no other changes. Do you expect them to work properly without changing anything else? My main concern is protecting the alternator. Not concerned with keeping the batteries warm. Thoughts, concerns, and suggestions welcome.
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See my post above or go to Bus Conversion magazine web site for a whole series of my articles that detail how to properly do what you want to do. You need to provide charging from the engine alternator, from shore power, from gen power or (optionally) from solar all without user intervention. You also need to make sure Li and LA batteries never get connected together as the higher voltage of the Li batteries could send a dangerous current surge into the LA batteries if they do. Watch especially “boost” circuits designed to connect your house to the gen starting battery on some implementations. This is a long way from the “drop in replacement” task you might have been lead to believe. Proceed carefully!
Jerry
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Do the math before you try to run AC units through inverters using 12vdc batteries, either Li or LA. The amp draw, especially on start up, is very significant and run times will be much shorter than you might imagine no matter how large your battery bank.
Jerry
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