I'm trying to figure out the best method to connect my 50dn alternator to my LifePo batteries. First, allow me to layout the components in play:
- A Delco Remy 50dn alternator (24v 270amps) - http://www.delcoremy.com/alternators/find-by-model-family/50dn
- 6x12v 100ah Battle Born LifePo batteries in 3x2 series/parallel for 24v (300ah)
- 2 Group 8D 12v starter batteries in series
Battle Born has told me that it should be fine to simply use a relay (auto or manual) to connect the starter batteries to the house bank, but for multiple reasons, I'm not sure I want to do that:
- My understanding is that Lithium batteries have a very low internal resistance and thus, when deeply discharged, could potentially draw a very large load to charge up again. (Maybe up to the maximum AH of the battery bank)
- I certainly do not want to run wire capable of handling 250+ amps from my start batteries to the lithium batteries.
- The alternator, obviously, does not abide by the optimum charge profile for LifePo batteries.
I believe the correct solution includes a DC-DC battery charger. In theory, a DC-DC charger designed for LifePo batteries could provide phased charging and voltage correction to insure that no damage is done to the batteries. I've researched several chargers from Victron (Orion), Sterling, Renogy, and MasterVolt. The issues with most of the chargers is relatively low output (30amps or less). Because my intention is to run my mini split while running down the road, I'd like to get as much out of the alternator as I can. Afterall, I've removed nearly all of the heavy load DC devices from the bus. (i.e. fans, lights, metro gear, etc.)
The one exception to the list is the Sterling model AB24100 https://www.sterling-power-usa.com/24volt100ampalternator-to-batterycharger.aspx (https://www.sterling-power-usa.com/24volt100ampalternator-to-batterycharger.aspx). This charger includes 4 stage, LifePo aware charging profiles and claims to output 100amps. At first glance, it looks perfect. However, when reading the install manual, there is this little warning:
QuoteBefore connecting the unit to your alternator(s) make sure that your alternator-to-battery charger is rated for the maximum output of the alternator(s) total combined ( if 2 are used ) current.
This seems to indicate that not only is this particular model too small, even their next unit up (AB24200) may not be "rated" to handle the 50dn. And even if there was a model capable of handling 300amps, the wire would be so egregiously large, it would hardly be worth wiring it all together. Please feel free to correct me on these assumptions; I'm certainly not an electrical engineer.
Keep in mind that I have reached out to multiple vendors and have either not yet received reply or received replies that do not fully satisfy the questions. So, I have the following questions for any that might know:
- My understanding is that a DC-DC charge controller, limits the current going from one side to the other. Why all this fuss about input current if the unit is designed to only charge at some designated amperage?
- Is this input current warning perhaps only applicable in cases where the charger is directly connected to the alternator?
- Would not, in my case, the starter batteries act as a sink for any extra current in the system once the house batteries are charged?
- Does anyone out there have experience doing this with their heavy alternator and Lithium batteries?
- Is there a smarter/better way to accomplish this?
If you're so inclined to investigate Sterling's charger, here's a link to the install/owner manual:
https://www.sterling-power-usa.com/library/Alternator%20to%20Battery%20Charger%20Owners%20Manual%20and%20Installation%20Instructions%20for%20all%20models%20excluding%20AB12130.pdf (https://www.sterling-power-usa.com/library/Alternator%20to%20Battery%20Charger%20Owners%20Manual%20and%20Installation%20Instructions%20for%20all%20models%20excluding%20AB12130.pdf)
Their wiring diagrams show clearly that this device is designed to sit between the alternator and batteries. My intended use would be to source the charger from the + terminal of the start battery and only use one side of the charger. The manual does state:
QuoteIf you are only going to charge one bank of batteries, then use the
"DOMESTIC BATTERY" output only. The "START BATTERY" output can remain unused without affecting the performance of the unit.
Thank you for any and all feedback. It's much appreciated.
I've been running a Sterling BTB charger to charger our 12v house bank from our 24v bus 50DN for years with no problem.
Not sure why the output of the 50DN is a concern here. My understanding is that they don't 'push' current to devices, but rather devices 'pull' current from them. Otherwise, you'd never be able to connect any device to a 50DN that couldn't handle all the possible output from it.
Our Sterling can pull a max of 35 amps @ 24v and output a max of 70 amps @ 12v and obviously our 50DN is capable of outputting much more than 35 amps.
I'd have no problem doing what you're planning.
The US rep for Sterling is quite responsive to questions, so I'd suggest that you give him a call if you're unsure.
All the the new RV class A and bus conversions like Liberty using LifePo are using a separate alternator completely separate of the chassis system but that could be and probably is because of all the sensitive electronics on the chassis with the CAN system
I currently have a 400 ah @ 24 volts lifepo4 house bank. I charge the bank from the 50dn while under way using a 400 amp relay controlled by a magnum SBC. (The sbc keeps the engine batteries full while parked, and a relay enrgized from an ignition source controls wether or not the big 400a relay is online or offline. This way the 400a relay only engages when the engine is running and the sbc sees a charging source.) After some experimenting I have found that it works quite well with the voltage regulator set at about 27.6 no load. The lifepo4 bank doesn't pull more than about 50 amps even when soc is very low. The trick is in the voltage, the higher you set the voltage, the higher the amp draw. If i switch on an ac unit or two while under way, the 50dn carries them no problem and the battery bank still gets its charging.
My understanding is that with regular automotive alternators(don't know if this applies to the DN50)the lithium batteries can draw so much power that the alternators are overworked and will overheat eventually destroying them. I asked this question on a lithium discussion blog but didn't get a definitive answer.
Great information guys. Thanks for the real world thomasinnv! Your experience with your LifePo4 batteries seems to contradict what others are saying about low SoC and current draw. Are you ever worried that under very low SoC (10%) your bank will pull more amps than your your relay connecting wires can handle? I currently have 2AWG from the starter batteries to my electrical bay, so I'm not wanting to pull much more than 100 amps continuously through it.
I got in touch with Adam at Sterling Power USA today and he said that the unit I was considering (AB24100) is not what I would need for two reasons: 1. The charge profiles are not inline with what LifePo batteries need. 2. The 50DN (24v at 270amps) is too large for the AB24100 (rated up to 100amps). He recommended their B2B charger model number BB242435, but it's only 35amps. I could run two of them in parallel, but they are pretty pricey to start doing that.
If my research is correct, my mini split system (https://www.ajmadison.com/cgi-bin/ajmadison/LMU24CHV.html (https://www.ajmadison.com/cgi-bin/ajmadison/LMU24CHV.html)) draws up to 1480 watts in cooling mode and 1800 in heating. This means I'll need around 100 amps from the alternator to run the mini split and not dip into the battery bank while running down the road.
I also called Battle Born again and got in touch with a gentlemen named Eric. Super helpful and spent 15-20 minutes on the phone with him talking over options. He's recommended looking again at smart battery combiners, so I'll go back and again research them. He suggested looking at Victron's Cyrix Lithium series, Balmar's MC624, and one by a company I've never heard of; Wakespeed.
I certainly like the simplicity and efficiency of a relay over a B2B charger. It seems like the market for these switches is just now coming up to speed with Lithium battery peculiarities.
Thomas did not contradict the conventional wisdom that LiPo banks can fry your alternator. Repeating what was said. the current into the LiPo bank can be controlled through the voltage setpoint on the alternator regulator. You would have to experiment with the voltage setpoint, and your bank. Set the voltage high enough on the alternator, and the bank could easily draw 2 to 3 times it's nameplate capacity. It's not a precise way of charging the batteries, but physics is physics.
You sort of have listed three requirements that don't want to play well with one another. Limit the current output of the alternator, run mini split with engine alternator, and no desire to install 4/0 battery cables.
You do have the 50DN working for you. Most setups have a much lesser alternator. I am assuming yours is oil cooled?
I really like Thomas's solution for simplicity and safety. Use a 400 amp continuous duty solenoid to merge the alternator to the LiP0. If possible find a way to monitor the temp of the alternator so that you can switch the solenoid off if it starts to overheat.
I just don't think the DC to DC chargers out there were intended to power an AC unit while going down the road.
There is a very good reason the Prevost converters are using a separate alternator to power their LiPo setups. They run into the same problem you have outlined.
I don't run my AC's off the engine. I do have a 1000 Ahr bank that I have had for 6 years. I have the merge/disconnect solenoid. And I hardly ever use my engine alternator to charge the LiPo's.
My .02, and not the gospel.
Thanks for the input Richard. Yes. My 50dn is oil cooled.
I had read about voltage regulation also controlling the current draw of the batteries, so that's finally clicking in my mind now. I've decided to go with the Cyrix Lithium series smart relay (https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-Li-ion-230-A-EN.pdf (https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-Li-ion-230-A-EN.pdf)) for now, so we'll see how that works for me. I'll report back after some tests.
Installed the Cyrix battery combiner today. The install is very straight-forward; before the Quattro, positives of the start and house batteries, and a ground wire to the start battery to measure voltage. When the voltage on the start battery exceeds 26.8 volts, the relay engages, combining the start batteries and the lithium batteries. It also has various time delays on engaging for various voltage ranges. This allows the start batteries to replinish before they feed the lithium bank.
In practice, I'm not 100% sure how well the setup is working. Here's the cycle I'm seeing with the bus running and shore power disconnected:
* Inverter on and under load (heat gun and shop vac), I can see the amp draw from the batteries for 4-5 seconds
* At around the 5-6 second mark, I see a current inrush (about 120 amps) and a voltage spike (30V) for less than a second and I hear the engine bog slightly
* Repeat ad infinitum
The state of charge was around 95% and falling slowly. It seems to indicate that alternator is not engaging for long enough periods of time to recharge the lithiums. I expected that the alternator would continue to run (engine bog slightly) continuously until the lithiums no longer accepted charge.
Maybe this is all normal. I need to run the lithiums down to a lower SOC and try again to see if the cycle changes.
In the meantime, does anyone have any feedback on what I'm observing?
What is the recommended voltage for charging the lithium batteries?
I am not sure that a straight combining will be good for them?
Also whether the simple voltage regulator in the coach charging system is competent to be charging lithiums?
I have only read enough about lithiums to know that that i need to read more.
Don't accidentally murder some part of your systems!!!
Happy coaching!
Buswarrior
Battle Born (makers of my batteries) advised me on two different phone calls that it is an acceptable way to charge the batteries. They recommended this specific battery combiner and others have used the same technology on various vehicles with various alternators including many high-amp models.
Spec. charge voltage range for my batteries is 28.4V - 29.2V. The combiner, designed for this, has voltage protection. (disengages outside of safe parameters).
The voltage regulator on the alternator may be an issue, but it's been said that others using a 50DN have successfully charged their lithiums in the same manner. Understanding that my setup my be different in some regard, there may still be a variable I'm not accounting for. I do not like the spikes to 30V that I'm seeing and is why I'm still using it in a strictly test capacity at the moment. Hoping to get some more answers before I atttempt to run it for long periods of time.
This method of charging the batteries is critical to my air-con plan going down the road, so I need to have high confidence that it's not damaging the batteries or the alternator.
You are lucky in respect that your alternator is belt driven ,the gear driven 50D does not do good with spikes at all just buy extra belts
The Victron Cyrix-CT is very interesting and relatively inexpensively device for it functionality.
I wonder if there is someway to trigger it once the RPM is above 1000 RPM, so it only draws power when you are driving?
Sure. The voltage control line on it, when open, disengages the relay. So, in theory, I could add a relay to that line that only engages when the ECM shows > 1000 RPM or any other variable.
Im planning a similar setup with oil cooled 50DN feeding 560amp 24 lifepo bank.
.
I think Battleborn has an integrated BMS that protects the battery from overcharge/discharge but it also may not be able to handle the 50DN 200+ amp charge
rate.
.
There are some interesting alternator regulators available that can taylor charge profile for lifepo and one does have a sort of current limit function available in the form of belt load limit.
.
If you want some good info on lifepo check out diysolar.com forum.
.
I wish there was a 24v version of this available:
https://www.victronenergy.com/battery-management-systems/battery-management-system-bms-12-200
In reviewing what I've done, I think I may have purchased the wrong relay. I've installed the "Cyrix-ct" combiner and I think I need the "Cyrix-Li-ct" combiner. I must have just clicked on the wrong thing in Amazon.
https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-ct-120A-230A-EN.pdf
(https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-ct-120A-230A-EN.pdf)
vs
https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-Li-ion-230-A-EN.pdf
(https://www.victronenergy.com/upload/documents/Datasheet-Cyrix-Li-ion-230-A-EN.pdf)
I also think that I've wired it incorrectly with the voltage sensor on the start battery instead of the Lithium side of things. It's possible that the BMS on the batteries (Yes, each BB battery has an integrated BMS) is cutting in and out with the voltage regulator causing the cycle that I described above. I'll play around with it a bit and report back here.
I saw a 2.5 mil Prevost they changed over to AGM from Lifepo the charging rate was killing all the electronic for the house system I am guessing the Crestron system didn't like it ,shouldn't be problem without all the electronics
Right you cannot just ADD lithium to existing system. It really requires a rethink/redesign with current limiting alternator for sure.
Cost no object would have LTO start batteries with LifePo4 house batteries.
LTO can handle any temp and can be 100% discharged without damage.
Plus the top and bottom charge limit can be higher than LifePo4. Finally LTO cranking amps are several times higher than FLA.
But LifePo4 is incredibly high density power source requiring less babysitting than AGM/FLA hence it popularity with the offgrid solar group.
Voltage sence line choices...
How are you going to protect the start batteries from over-charging, when the Lithiums are still calling for a charge?
Mixing battery types with one charge source has always been a devil...
Keep your money in your pockets!!!
Happy coaching!
Buswarrior
Here's my experience on this.
Last year I started doing a Li-Ion house battery upgrade. The starts are two Group 31 24v. They got a bit abused so were pretty pokey so I figured I'd explore using the house bank, alternator, and PV as sources to keep Group 31 happy.
I experimented with connecting the start battery to the house bank then tested charging from the alternator (DN50 gear) to the starts then to the house battery. The first thing I noticed is the wiring (jumper cables) between the house and start getting hot. The current meter was showing over 200 amps @ 24v. That experiment stopped and time to ponder.
After some research, I decided it was not very smart to connect Li-Ion to LA bank which was connected to the alternator. These batteries have are very different technical specifications. And as was pointed out unless you monitor and control the flow of current between the house and starts you are completely exposed to overcharging and draining your precious and expensive li battery bank. Maybe the BB battery with internal BMS can do the job but I'd not trust it.
After much more pondering where I went was based on my own goals and that is to be 100% self-sufficient off-grid with supplemental external power only in worst-case, emergency scenarios.
I'm using a PV system to fully charge the Li-Ion 24v 480aH bank each day, no other charging source at the moment. The PV generates over 50Ah @ 26v or about 1500 watts of the rated (1800). This is more than adequate to run everything the same as in your home residence.
However, recent trials have shown that the Norcold 3-way absorption refrigerator is a massive energy hog, over 4kWh per day. By the afternoon with the house bank full, it will draw down several thousand watts overnight, so around 70% SOC in the morning. The system can easily handle this but it is disturbingly excessive energy to keep such a small cooler going. I'm planning on swapping out with a small apartment unit that will use much much less energy.
The other huge hog is the electric water heater. It draws thousands a day too as seen in the diagram. Each regular rise is about 450 watts and lasts for some time, around the clock. I called Sure Marine about this and he did not seem to know it cycled in this manner. Maybe the thermostat needs replacing? Meanwhile, when not lazy I manually switch on the hot water heater for an hour during the day and shut it off. The water stays plenty hot so it works as an interim solution.
The backup plan on the electric refrigerator is simply to switch to propane. It works fine, just uses propane. Part of getting totally off-grid self-sufficient includes ditching propane and 100% self generating electricity.
Long story short, I started down your path but as you see my journey went off on a totally different path. One last piece of the story which is coming next. There is a huge diesel generator taking up half a bay and weights a lot. I want that gone! I'll get a small quiet portable generator to supplement charign the house bank when extended days of lack of sun power. Based on my planned daily consumption a couple hours on a 2kW should be fine to top off the battery bank.
Finally, they may say you can do what you want but just the basic mismatch of LA and LI connected together is generally not the optimal configuration and incurs some real risk with respect to keeping both banks in their happy zones.
Thanks for the info WindTrader.
I watched this video some time ago and it provides some interesting information on the challenges and possible solutions for sovling this:
https://www.youtube.com/watch?v=dzU_pQFa19s
(https://www.youtube.com/watch?v=dzU_pQFa19s)
The real stuff starts around the 9 minute mark.
OK. Got to 18 minutes. Had enough of the marketing of Victron products to solve charging paths that are not typically done. OK, so sure you can do this sort of stuff and Victron more than happily will offer up some product to solve that niche integration issue.
I'm still on the side that this is not an option unless you are forced into or don't have other options. This video convinced me charging via alternator to house bank is not the preferred method.
Quote from: buswarrior on May 17, 2021, 10:21:24 AM
Voltage sence line choices...
How are you going to protect the start batteries from over-charging, when the Lithiums are still calling for a charge?
Mixing battery types with one charge source has always been a devil...
Keep your money in your pockets!!!
Happy coaching!
Buswarrior
This is very interesting indeed. I'm trying to integrate my big LifePo4 pack into the vehicle charge system too.
What I found is the LA start batteries max charge voltage actually
exceeds the LifePo4 safe limit and would potentially degrade/destroy the expensive Lithium house pack.
If the 50DN (or other big alternator) charge profile is set for LifePo4 the LA start batteries will slowly degrade due to never being run through the full three state LA charge cycle.
I'm tired of baby sitting LA batteries though so I've been considering a design that replaces the LA start batteries with Lithium Titrate Oxide (LTO) pack. LTO is too expensive for house batteries but are ideal as start batteries
for the following reasons:
1) permissible upper voltage is higher than LifePo4
2) can be 100% discharged without damage
3) very wide temperature range
4) Ultra high safe discharge capability (cranking duty)
5) Unlimited cycle life! (for our purposes)
A relatively small LTO pack could replace a couple of 8D starts. An intelligent battery combiner can be used to charge the LifePo4 house when LTO pack voltage high
enough and optionally back charge the LTO starts from LifePo4 bank when needed.
A
REAL current limiting alternator regulator is still needed and so far I have not found any that offer that feature yet.
That said the premade Lithium packs usually have protection circuits integrated into the pack to help protect them as a last line of defense.
I think its worth mentioning that LifePo4 cannot be charged below 32F! For that reason they are usually located within the living space or some other temperature controlled area.
-----
Why you "baby sitting" LA batteries?
I confess the same past concern. That is now resolved and no longer any concern. As my electrical system supplies all the energy today, I just flip a switch or plug in a device. What I now do is whenever it seems like the starts might need a bit of TLC, I just plug in the small charger and starts are happy again. so easy - no muss - no fuss.
Quote from: windtrader on May 17, 2021, 02:08:19 PM
Here's my experience on this.
However, recent trials have shown that the Norcold 3-way absorption refrigerator is a massive energy hog, over 4kWh per day. By the afternoon with the house bank full, it will draw down several thousand watts overnight, so around 70% SOC in the morning. The system can easily handle this but it is disturbingly excessive energy to keep such a small cooler going. I'm planning on swapping out with a small apartment unit that will use much much less energy.
I switched my NorCold over to a DC compressor setup and it works great for me!!! Which I got from:
https://jc-refrigeration.com/ (https://jc-refrigeration.com/)
More detail is on my build thread:
https://www.busconversionmagazine.com/forum/index.php?topic=34318.msg405259#msg405259 (https://www.busconversionmagazine.com/forum/index.php?topic=34318.msg405259#msg405259)
Like you I do have electrically driven water heaters as part of my hydronic system. However my hydronic system makes use of a diesel boiler as it's main heat source. I only use the electric water heaters to dump power too when I have too much solar input or when I have shore power available.
Hi Fred,
Sill playing tag - I think you're it! LOL. one day we'll connect
I have explored products from this same company. They seem very knowledgeable and will gladly provide adequate support both pre and post-sales. The brochures are in the tickler file but I've since decided if going to this amount of effort, I may as well get more space, as it just doesn't support the sorts of stuff we put in the refrigerator. Stuff always not fitting or banging into something else. And that is with not many items at all. Like a two liter soda bottle won't go in upright and needs to lay on the side on a shelf. does not fly in my bus.
Two options - slide in a 10 cf small compressor-based apartment style refrigerator if it fits through the door. Or custom build an insulated storage box then run the compressor from a bay. 120v of course. Need to do calcs on actual efficiency before running down that path.
The hot water system does have a webasto loop but that uses diesel. Yeah better than propane but still non-renewable energy source. There is a small inline pump. The webasto control has two on states - one is labeled exchanger and the other is burner. I use burner for interior heating. I think the exchanger setting is for block heating and the water heater loops.
This is a timely topic because I'm needing to get the mini split installed and need space for the condensor/fan unit. Where I'd like to place it is where two 5 gal propane tanks live. I think an earlier measuring confirmed it would fit with the tanks. If that is not right then just one more reason to dith propane now.
Quote from: windtrader on May 18, 2021, 10:58:17 AM
Why you "baby sitting" LA batteries?
....
Just that traditionally they are problematic requiring periodic replacement and "special" charging regimes. Plus full of acid, gives off hydrogen, dies when discharged 100% etc.
Currently I just ignore start batteries special needs and periodically put them on a charger to keep them happy.
QuoteCurrently I just ignore start batteries special needs and periodically put them on a charger to keep them happy.
Is that not good enough? Just curious for taking time and energy on this
Quote from: windtrader on May 18, 2021, 06:28:23 PM
Is that not good enough? Just curious for taking time and energy on this
I think so since converting the 4106 to 24v. With 12v
everything had to be 100% or it would struggle.
With 24v even a couple of car batteries will easily start it. I will revisit LTO batteries when replacement time comes.