[Archived]

talk to jon about drop in. . . the best ones are the prismatic 3.6v cells, but thats a lot of work so probably a non starter for you. Drop ins are not a bad option. I’m a believer of handling some of those issues. the drop in manufacturers will tell you that they can handle some of it, but they dont always tell you the other ramifications if you dont. you hit the nail on the head with low temp and alternator charging. . so you can either choose to address them or not. low temp charging isnt an issue for people located down south. But it only takes 1 time of charging below freezing to permanently damage them.. .

[rafael]

Les … there might not a “drop in Li-Ion solution” yet for mere mortals like you and me.

I want pretty much the same thing you do. Let me know when you find it.

[DON]

Les, I am only speaking for my situation with my Liberty, its single 50 DN alternator, and my Outback inverters. I posted the article about swapping with AGM and 100% of the charging values are within the Li allowable range.

I did not have to do anything else. But………my Relion batteries have charging limitations based on temperature so to be assured I will not screw up and slap them with a high current charge when they are cold I enclosed the batteries, and then as the article shows I have a means of never allowing them to drop below 40F.

The heating system will always be “on” as I have it set up now, but if I have doubts I can look at the temperature controller and verify the battery compartment is 40 or above. If I screw up and forget to verify the batteries are warm, I set the Outbacks so my charge current is below the limits Relion specifies. If the temps fall below 14F I have to reset the Outback currents.

If I screw up and start the engine when it is below 14, and the heating system is not working because I have the switch turned off or if it failed then the alternator output can damage the batteries. I think I will be careful enough and I think the chance I am going to be using the bus where it is in the teens is slight.

As to protecting the alternator if the batteries shut down, in the article I showed a monitor I added that displays the battery voltage and at a very conservative 12.2 volts it emits a loud and very annoying alarm. Relion would like to see auto-start to be triggered at 11.8 so as can be seen I have some margin.

I know Anthem is expressing some concerns, but I believe I have addressed them to the extent I have to date. He apparently feels strongly that the alternator will be damaged if the Li batteries shut down but I have given that a lot of consideration. If they shut down when the alternator is providing charging current, the load on the alternator still continues because the 50DN is still charging the chassis batteries so it will not see a total open circuit.

But I also considered what is the most probable Li shut down, and there are two possible events. The first is they aren’t being charged and they go into a low voltage shut down. In that case the alternator is unlikely to be charging them or the chassis batteries. The second possible shut down is an over voltage condition, in which case something is already wrong, likely a voltage regulator. In that case the coach high voltage warning is going to come on before the Relion shut down voltage is reached. Hopefully I will react appropriately and get the coach shut down quickly. It should be noted a two alternator conversion will not have that high voltage alert.

I hope Anthem stays with the conversation because I think I addressed the issues on my coach, but other Liberty models or other conversions may require some different considerations.

[Art]

Jon – if the alternator is connected to the start (or generator) or /any/ lead acid battery in line with the lithium batteries then you are good and have addressed the alternator issue. Any agm battery will absorb and give the alternator a sink since you are not open circuiting. You will want a battery isolator that is tailored for lithium’s though (like Victron cyrix-li-charge, or sterling also makes one). It has to be lithium specific because most battery isolators (like blue sea) disconnect at too low a level and you end up charging draining the two batteries banks together. The lithium batteries like to sit at 13.2 and agm is 12.8. So if the disconnect is at 12.8 then the lithium batteries end up charging the start batteries until they both drop to 12.8 before separating. Make sure the always connected battery is the agm and not the house. The other option is cutting the field wire on the alternator regulator to the alternator shuts down sending current. But you have the easier method.

as for low temp – if you are in the south in Florida – no issues at all. If you go places where it falls below freezing – if the batteries are in pseudo temperature controlled bay then chances are you are fine. If they are exposed to the elements – then yes – you need to figure out a way to get them above freezing before any charging current goes in. Relion and others list a charging current based on temperature. But it’s pretty low. I would just cut charging at all if the temp is below 40. The problem is – many charge source cannot cut charging based on temperature. So you kind of have to put something to cut the charge in from your charging sources (alternator, inverter/charger, solar, etc ).

You can heat your bay up with temperature outlets and what not. They can be driven via ac or dc (but your battery might drain from it.

Most of these are controllable as long as you have power. The issue is if you are parked somewhere cold. You come back and the house batteries are dead and your batteries are below freezing. How do you prevent charging current from going in to the batteries when you start your coach ?

[Keith]

To specifically address the last paragraph my reasoning is as follows.

First, understand I am ultra-conservative with respect to house batteries so if there is any possibility, no matter how remote that I will do a deep discharge on the house batteries, regardless of type, and now regardless of temperature, I am going to insure they are being charged. I run my generator a lot and my inverters as mentioned in the article are set to charge at 30 amps (60 total) which is way below the allowable charge rate at 32 degrees.

But in addition with the battery compartment heating system working, even if I lose my mind and start the coach, and charging from the alternator, my batteries are going to be warm.

I have to have turned off power to the compartment heat and I have to ignore the cold temps and I have to have the generator or shore power off so I am dumb enough to start the coach in the cold. If I don’t change my habits of 30 years the first thing I do after a night with batteries being drawn down by the lights, refrigerator, water pump, aux compressor, etc. is start the generator and then we make coffee, I get on the computer, usually have all the lights on, etc. but I just figure with the batteries being drained all night, regardless of how much charge remains, I am recharging them. I am not someone who opts to wait for auto-start. If I did start to use auto-start I would definitely make sure charging current settings were so low cold batteries could handle it.

I think I can count on my fingers the number of times I got up in the morning and started the coach, without having first started the generator.

[Jeff]

But the generator is the same issue. You can’t send any real amps (yeah they think 30 might be ok but who knows ) in to the battery bank until the entire /inside/ or the battery is above freezing.

I get that you are super careful and it would be rare. I’m pointing it out for people who aren’t careful. Who occasionally forget and occasionally run their batteries to dead either unintentionally or intentionally.

so if you wake up and the gen start didn’t low voltage start and the bay is too cold – then starting the generator won’t help either. Because that will start your heaters but also start the charging mechanism. You essentially want the battery to start – and not start the charging methods until the battery is at the right temp – and not the battery bag. Because the battery bay can get up to temp but the mass of the battery might still be an hour away from getting say from 25 to above freezing.

again – all of these are exceptions. But if people don’t know – they can be costly exceptions.

[Archived]

If you read my article I set it up so I can screw up and not suffer consequences unless I have multiple screw ups.

At the inverter current settings I can have batteries in excess of 14F and I am well under the charging current limit for batteries below 32.

At 14 degrees as a practical matter it is going to be almost impossible to screw up because if we know it is going to be in that range or below the bus engine or the generator is going to be running. We cannot expect to stay warm with 14 degree outside temps unless we have our Webasto and toe space heaters operating and I am not operating them from inverters or batteries.

Actually, if the temps at night are getting low, such as in the 40’s the generator is going to be running all night.

I cannot address how others need to deal with cold batteries, but based on how I use the bus, and how I set up the compartment heat there would have to be a string of failures or oversights before batteries might have cold temps that would cause them damage.

Can shit happen? Absolutely, but I think I have enough ways in place so I will not harm the batteries. People who tend to not consider the required methods of operating the coach should not have Li, but should stick with batteries and systems less apt to be damaged.

[steve]

Les,

If you’re concerned about temps, you can always go the RELION LT (low temp) route that have internal heat. The down side is they’re only 100 amp and group 31 size, but you could make them work Assuming you’re 12v.

[Archived]

Tom, I think temperature control would be relatively easy for my arrangement.

I’ll be paying attention for a while since next Spring will most likely be my battery replacement time.

I may poll Inverter Specialty for their experience with Magnum inverters and BMK control.

[Archived]

Anthem wrote, “Most of these are controllable as long as you have power. The issue is if you are parked somewhere cold. You come back and the house batteries are dead and your batteries are below freezing. How do you prevent charging current from going in to the batteries when you start your coach ? “

Isn’t the answer that the battery BMS will not allow charge current into the batteries until the internal cell temp is above freezing? If your alternator is set to charge both the Li house battery bank and a LA battery (like the gen start battery) through a proper combiner then there is no harm to batteries or alternator. Attach a heat blanket to the Li bank powered by the alternator or gen/shore power and the BMS will only allow charge current once the Li bank cells are above freezing.

Jerry

[Archived]

You can charge cold Li batteries, but the battery specs make it clear what the charging current should be. As they are charged they will begin to heat.

I would NEVER start a coach with cold Li batteries because the alternator output likely exceeds the current limits for cold batteries.

If the batteries are not in a temperature controlled compartment that keeps them above their cold temperature charging restrictions, set the inverters to an allowable charging current and start the generator. For those that rely on auto-start you have to make certain the inverters are set to the correct current levels based on the battery temps. You cannot spank cold Li batteries with 65 amps of charging current if they got cold before the auto-start kicked in.

I am not an Li expert. I am doing to my coach what I think is required to prevent me from doing something that is going to harm my Li batteries and my guide is the instructions and specifications from my Li battery manufacturer.

The BMS on “drop in” Li batteries will provide protection to a point, but as an owner if you rely on the BMS solely you are likely to get in trouble.

Anthem has made it clear Li batteries are not tolerant of the abuse an AGM will take for example.

[Archived]

Most bms units do not handle temperature cut offs. The relion and a couple others do but the majority so not.

jon is half system and half his diligence. Which works as well. But as he has noted – If someone isn’t as aware as he is – then they might be hit with a costly surprise.

You are close with a method. It’s best to hook inline to a LA battery for diode protection. Then from the battery use a alternator to battery charger or dc dc charger fed by a relay based on temperature. But as mentioned – what if the battery is cold – you have to wait until the entire battery (not the terminal ) reaches above freezing before its safe. Also lithium batteries don’t heat up much when charging like agms which you can’t rely on. They don’t heat much at all

as for heaters be very careful. The ones that are out there (whether silicon or not) frequently are too hot for the plastic lithium cases. Most of the battery thermal wrap manufactures explicitly say – not for use on lithium batteries. Battle born has an expensive patch for warming batteries – as you could use much lower power heaters. But one does need to be careful there.

[Dan]

I specifically stayed away from heater mats or blankets and instead compartmentalized my 4 8D batteries in a sealed compartment. I have that compartment set using a heater control (a fancy word for a thermostat with a temperature read out) powering a small 200 watt space heater that maintains the compartment above 40 degrees F.

The intent with my set up is to insure there are no hot or cold spots, and the batteries are in an environment with a uniform temperature.

If I am in very cold ambient conditions before I do anything, I will look at my compartment temperature readout to verify it is above 40 degrees. If it is below I will insure I adjust the inverter charging current appropriately.

[Archived]

I added another article to update the information previously posted.

Prevost community relion update 4-11-2020.pdf

My confidence level relative to the change to Li batteries is higher now than it ever has been, but the batteries are not AGM, are not going to act like AGM, and because I had not realized how my inverter set up played into the Li battery performance I got blind sided.

Because I got a surprise when I decided to measure performance I will be using this period of time when the coach is not being used to do some tests and use the test results to make more decisions relative to using and managing the batteries.

I still do not know what i do not know so I am hoping I can develop enough solid information through testing to address some of the still unresolved issues like auto-start.

[Archived]

Hi Jon,

Thanks for your helpful articles on Li battery conversion. I recommend them to anyone who is interested in this subject.

The first of what will be a series of articles on Li conversion I have written for Bus Conversion magazine appears in the April edition. I think the information reads more easily as one long article, but the editor felt it would be better broken into four which will appear in the April, May, June and July 2020 editions.

I am finding the two least understood factors in making this conversion from LA to Li batteries for our buses are:

(1) that there are six entirely different battery chemistries that are all called “lithium”. Only one of those, Lithium Iron Phosphate (LiFePO4) is safe and appropriate for use as house batteries. The three that involve alloys of cobalt that give them even more capacity require active heating and cooling along with very sophisticated electronic management that are beyond all but the most skilled and knowledgeable to pull off safely. I strongly recommend we all be very careful with the many You Tube videos of people trying to break open electric car batteries to harvest the cells. That is not something for a novice to attempt or to deploy.

(2) Lithium batteries operate at higher voltages than their LA counterparts all the way from fully charged to nearly fully discharged so looking at voltage at rest gives you little indication of state of charge. In fact, for more than 85% of the charge capacity of a Li battery the indicated voltage at rest will be higher than a LA battery indicates when fully charged. That means that a Li battery will produce more watts to power the devices that do useful work for you in your coach in nearly all conditions over what you can obtain from a LA battery. A lead acid battery looses voltage the minute you start using it and looses voltage very quickly the harder you use it. Li batteries don’t show those undesirable traits nearly as much.

Now here is the controversial part. For most bus conversions you can substitute nearly one third the ampacity in Li batteries for what you have in your existing LA batteries. If you do the calculations showing you can draw 50% from LA and about 85% from Li you will be led to a different conclusion. But, in the real high draw world of buses where the LA batteries loose voltage so quickly, you never really know how quickly they drop below 50% so most LA batteries in buses have depleted their real capacity far sooner than you might think and far sooner than the assumed 20 amp per hour draw those calculations were based on. In short, unless your LA batteries are brand new and properly installed (correct wire sizes, and terminal ends, etc.) the actual capacity you are now experiencing is likely far lower than the rated capacity would lead you to believe. Hence, the conversion from LA to Li is closer to 3:1 than the 1.7:1 or 2:1 the normal calculations would suggest.

Drawing from experience in marine applications it is relatively easy to source the devices you need to properly charge Li batteries from all three charge sources in your bus and protect your engine alternator from either over heating or from the assumed voltage spikes that might occur if the BMSs shut off charge current to fully charged Li batteries at the same time. It is less easy to come up with the proper auto gen start scenario or technique. A closed, insulated Li battery compartment with any form of minimal heat – anything from an blanket if the Li battery case is designed for that, or a heater like Jon describes – will most likely handle the issues of charging a Li battery below freezing. A simple light bulb is likely all most of you will need for heat in that closed, insulated compartment the way our buses are constructed.

While weight savings and 5x to 10x longer life are real benefits, where Li batteries really shine is the vastly shorter recharge times. Solar now becomes a real option that many of you may want to take advantage of given the amount of room available on the top of our buses. Just be sure to use properly sized MPPT charge controllers and proper wire from the solar panels to the charge controller.

Jerry