another DIY roadtrek lithium - newb needs help

[booster]

Originally Posted by avanti

Actually, there is a third option, and it is a pretty good one in many cases:

You can use the DC from your engine alternator to power a large inverter (say, 2,000 watts). Use the 120VAC output from this inverter to power the "shore power" input to your coach's charger, which will then charge you battery just as if you were plugged in to shore power, using whatever profile you have programmed. Good chargers let you limit the shore-power takeoff, so you can use this feature to limit the current demanded from your alternator to any level you desire.

This is probably what I am going to do in my new Transit.

That does seem to be more popular lately as it is pretty easy to do. It would save hardware a bit if you could use the same inverter to switch to coach AC when on batteries, also, but more complex by some amount.


With a big system you may get in to having the inefficiencies drive you past the limits of the alternator(s) and/or wiring though. Depending on where they are running in the capacity range, I would expect both the inverter and charger to be in 5-15% range for inefficiency so it could be a big number if you are looking for the 300 amp charge rate for 4/0 cable.

[GallenH]

Originally Posted by booster

In marginal alternator size applications you would be way better off in cost and complexity to just put in a higher output alternator in place of the standard one then you can get higher output with a larger B to B with maybe only wiring size changes. Once you get much above 80 amps charging rate, it starts to tilt to using a separate alternator, IMO.

Any leads to vendors of HO alternators? Are there any risks to original equipment in using a HO Alt? IOW: Can you damage existing?

as always........thx.glenn

[avanti]

Originally Posted by booster

That does seem to be more popular lately as it is pretty easy to do. It would save hardware a bit if you could use the same inverter to switch to coach AC when on batteries, also, but more complex by some amount.

I have seen folks who put an A/B switch to select house vs. engine AC. This provides some redundancy in case of a house inverter failure.

With a big system you may get in to having the inefficiencies drive you past the limits of the alternator(s) and/or wiring though. Depending on where they are running in the capacity range, I would expect both the inverter and charger to be in 5-15% range for inefficiency so it could be a big number if you are looking for the 300 amp charge rate for 4/0 cable.

Yes, I should have mentioned the efficiency penalty. However, it seems ideal in the case of the Transit dual alternator, since there is more power available than one is likely to use, so the inefficiency isn't really important. As we have discussed elsewhere, I like having the charge parameters in one place. It is also likely to be significantly cheaper than the large/multiple B2Bs needed in a large system. And, remember, if you put the engine alternator in the front, you don't need the typical long 4/0 cable--it is replaced by a small 120VAC run.

[booster]

Originally Posted by avanti

I have seen folks who put an A/B switch to select house vs. engine AC. This provides some redundancy in case of a house inverter failure.


Yes, I should have mentioned the efficiency penalty. However, it seems ideal in the case of the Transit dual alternator, since there is more power available than one is likely to use, so the inefficiency isn't really important. As we have discussed elsewhere, I like having the charge parameters in one place. It is also likely to be significantly cheaper than the large/multiple B2Bs needed in a large system. And, remember, if you put the engine alternator in the front, you don't need the typical long 4/0 cable--it is replaced by a small 120VAC run.

Yeah, we have discussed numerous times who simplifying the controls for lithium could be a good thing in relation to that kind of setup.



How big a charge rate are you looking for? If it is moderate, absolutely no reason to worry much about efficiency. Is all you equipment going near as you can get it to the front?

[booster]

Originally Posted by GallenH

Any leads to vendors of HO alternators? Are there any risks to original equipment in using a HO Alt? IOW: Can you damage existing?

as always........thx.glenn

I would start with Nations alternators as they do a lot of that kind up upgrade stuff as well as the second alternator systems.


They carry a bunch of high output models that are made by DC Power Engineering, which are good units. The Denso style hairpin wind units are quite efficient and with extra pole count get less ripple, so all good. Nations should be able to tell you if you van has any particular limitations to upsizing.


Getting up to a 240 or 250 amp alternator, as long as it has good low rpm performance also (many cheap ones don't), lets you use in the range of 125 amps total continuously so less critical on making sure you don't pull off too much and not leave enough to run the van if you are running lights, heater blower, etc at the same time.


Good high output, new not rebuilt is best, alternators are not cheap though, but going cheap on something that can spoil a trip isn't a good idea IMO.

[bumpersignal]

Thanks for everyone's advice. You've changed my mind and I will go with the simpler route of getting a Balmar and connecting that to my 2nd alternator (Mercedes-280XP) and then straight to lithium.

[bumpersignal]

Originally Posted by booster

A B to B works well and simply with a single alternator or parallel alternators but is more trouble with standalone. A Balmar will also have the same issue is the lithium batteries go offline and removed it's reference from the Balmar.

Now that I've decided to go the Balmar route, I'm interested in understanding what to do if I run into this situation where my lithium goes offline, how do i get the alternator to turn on to charge it?

[booster]

Originally Posted by bumpersignal

Now that I've decided to go the Balmar route, I'm interested in understanding what to do if I run into this situation where my lithium goes offline, how do i get the alternator to turn on to charge it?

Others would know better for certain, but if it is off because it hit low charge cutoff there would usually be a button to push and hold to turn it back on enough to get the alternator to charge. If it is in low temp cutoff, you need to have a way to run the heaters or van long enough to heat the batteries so they come back online.


I think if I were doing it, I would have a small AGM that could be cut into the circuit or even better a way to switch the lithium and heaters to main alternator system temporarily until the batteries come back online. Restarting shut down batteries has been one of the issues most often hard to get right, I think. Roadtrek had lots of stranded vans and upset customers for quite a while because of it. Even the earlier ARVs didn't have a way to recover from a cold shutdown other than a recommendation to go someplace warm or a heated building to warm them up. Their batteries were underbody then so no van heat would warm them adequately and the heaters ran off the lithium pack which was shut down.

[avanti]

Originally Posted by booster

How big a charge rate are you looking for? If it is moderate, absolutely no reason to worry much about efficiency. Is all you equipment going near as you can get it to the front?

I haven't really looked carefully yet, but my current thinking is to use something like a 2200 watt engine inverter, maybe this:

https://www.amazon.com/dp/B07CKBJ9KP?th=1

For the charger, probably a Victron Multiplus 3000:

https://www.amazon.com/dp/B06XGFWHBC

I will probably do 24V. At that voltage, the 3000 will charge at up to 70A. I'm thinking maybe 350A@24V of batteries. All of this seems fairly well balanced and is well within the capabilities of the Transit. With dual alternators, it will probably charge near 70A even at idle.

Batteries and charger will probably be in the back, but @120VAC, it doesn't matter much.

[booster]

Originally Posted by avanti

I haven't really looked carefully yet, but my current thinking is to use something like a 2200 watt engine inverter, maybe this:

https://www.amazon.com/dp/B07CKBJ9KP?th=1

For the charger, probably a Victron Multiplus 3000:

https://www.amazon.com/dp/B06XGFWHBC

I will probably do 24V. At that voltage, the 3000 will charge at up to 70A. I'm thinking maybe 350A@24V of batteries. All of this seems fairly well balanced and is well within the capabilities of the Transit. With dual alternators, it will probably charge near 70A even at idle.

Batteries and charger will probably be in the back, but @120VAC, it doesn't matter much.

Small buck converter to get back to 12v for accessory stuff?


How much total alternator you going to have?

[avanti]

Originally Posted by booster

Small buck converter to get back to 12v for accessory stuff?

Yes. Fridge and A/C can both be 24V, also most of the LED lighting. So I won't need much 12VDC--mostly media. I am picturing having a DC power panel that provides 5, 12, and 24VDC (a lot of the automation stuff will be 5VDC).

How much total alternator you going to have?

I think that each alternator is 250A, so 500 total. The upfitter power takeoff is rated at 300A continuous. You can go to at least 350 with a few caveats. SO much better than the Sprinter.

[booster]

Originally Posted by avanti

Yes. Fridge and A/C can both be 24V, also most of the LED lighting. So I won't need much 12VDC--mostly media. I am picturing having a DC power panel that provides 5, 12, and 24VDC (a lot of the automation stuff will be 5VDC).


I think that each alternator is 250A, so 500 total. The upfitter power takeoff is rated at 300A continuous. You can go to at least 350 with a few caveats. SO much better than the Sprinter.

Does Ford publish any output vs temp or duty cycle at load data? Since this is obviously intended to be high output they may use better than normal OEM alternators. Closer to marine rated ones. That would be awesome.

[avanti]

Originally Posted by booster

Does Ford publish any output vs temp or duty cycle at load data? Since this is obviously intended to be high output they may use better than normal OEM alternators. Closer to marine rated ones. That would be awesome.

You can find all kinds of stuff in the Transit BEMM:

https://madocumentupload.marketingas...05185&v5=False

Here is alternator output vs temperature:

alternater-temperature.jpg

Not sure about duty cycle. Remember, though, that there is a load-shed feature.

[booster]

Originally Posted by avanti

You can find all kinds of stuff in the Transit BEMM:

https://madocumentupload.marketingas...05185&v5=False

Here is alternator output vs temperature:

Attachment 12459

Not sure about duty cycle. Remember, though, that there is a load-shed feature.

I think that chart may be the load shedding as they are cutting down the voltage which would likely be field current cut. Makes sense. They do go to 240* so not comparable to the 50% field turndown of the Balmar at 225*, though.


They turn it down about 28% from coldest to hottest if you look at watts and not amp or voltage, so not too bad, but amps will be lower that you get out by the time you invert it and then back to higher voltage than it start at. It will be good to see watts in and watts out of the whole process as that is what really counts. It will be interesting to see what it actually turns out at if you do it that way. Very nice to have the PCM doing it all for you as it will also be looking at the van load which can be substantial depending on what is running. I like it.


We have 530 amps of rated alternator with two DC Power Nations alternators and with the poor airflow overthem that the Chevies have, we can only run about 180 amps at 14.4v continuous before we get to 225*. We can go to 280 amps, which is where the battery acceptance levels to after surging over 300 amps for a little bit of time, for about 20 minutes before the batteries and alternators start to get too hot.

[avanti]

Originally Posted by booster

Small buck converter to get back to 12v for accessory stuff?

BTW: One of the things that is pushing me toward 24VDC is the fact that people have been having issues running some 12VDC devices (e.g., the MaxAir fan's controller) on lithium's 13+V voltages. If I am going to have to regulate the 12VDC anyway, I may as well go to 24V.

[larrylwill]

I am going through the same problems. I upgraded to to a 280A Lipo4 battery. NOT Battleborne, I added a 150A BMS. Eventually I found out that the 2nd Alternator can charge at 280 amps but the BMS can only take 150A before it shuts down' I bought a Renogy Dc2DC then found out that both the dc2dc and the alternator need to be excited with 12v. I called Nations Starter which makes the 2nd Alternator and they said I can send in the Alternator and they will add a Balmer to it cost around $400 plus shipping. I also talked to Battleborne and they suggest NOT To charge there 100A batteries with more than 1/2C or 50 A. You should call to find out how much you can charge your battery. Now Im looking for a simple way to excite the alternator without adding another battery. So far the simplest way is to use a push button from the starter battery to the alternator. The 2nd is to connect the alternator to the starter solenoid. So that when the key is turned the solenoid connects the starter to the starter battery it also connects the 12v to the 2nd alternator. Although this method might be a problem if the starter causes spikes when it turns off.

[bumpersignal]

Originally Posted by larrylwill

I am going through the same problems. I upgraded to to a 280A Lipo4 battery. NOT Battleborne, I added a 150A BMS. Eventually I found out that the 2nd Alternator can charge at 280 amps but the BMS can only take 150A before it shuts down' I bought a Renogy Dc2DC then found out that both the dc2dc and the alternator need to be excited with 12v. I called Nations Starter which makes the 2nd Alternator and they said I can send in the Alternator and they will add a Balmer to it cost around $400 plus shipping. I also talked to Battleborne and they suggest NOT To charge there 100A batteries with more than 1/2C or 50 A. You should call to find out how much you can charge your battery. Now Im looking for a simple way to excite the alternator without adding another battery. So far the simplest way is to use a push button from the starter battery to the alternator. The 2nd is to connect the alternator to the starter solenoid. So that when the key is turned the solenoid connects the starter to the starter battery it also connects the 12v to the 2nd alternator. Although this method might be a problem if the starter causes spikes when it turns off.

Few questions:
1. how come you asked Battleborn (BB) about your setup but the battery isn't battleborn? I assume the question is BMS specific so their answer based on their own BMS might not be applicable to your situation?
2. if you're doing DC2DC (battery to battery?) I don't understand why you need to excite the alternator. The way my RV came from the factory, the alternator that's dedicated to charging the coach is connected to just the AGM batteries, and afaik nothing excites it to turn on.

[larrylwill]

I called Battelborne because I know someone that had hooked up there 2nd alternator to a 100 Amp one, I wanted to check there BMS.
The 2nd alternator does not have a BMS.

I do not have any AGM batteries connected. It came with one and I added a 2nd, but the factory one shorted and shortly after the one I added also shorted.
SO with no AGM on the alternator the alternator wont start unless I connect a 12v source to it. I can manually short it to my lipo4 to get it going but I don't want to have to remember to push a button every time I start to drive.

[booster]

Originally Posted by bumpersignal

Few questions:
1. how come you asked Battleborn (BB) about your setup but the battery isn't battleborn? I assume the question is BMS specific so their answer based on their own BMS might not be applicable to your situation?
2. if you're doing DC2DC (battery to battery?) I don't understand why you need to excite the alternator. The way my RV came from the factory, the alternator that's dedicated to charging the coach is connected to just the AGM batteries, and afaik nothing excites it to turn on.

As soon as you put a B to B in the circuit to the batteries, no matter what kind they are, the B to B isolates the batteries from the alternator so it won't run because it sees no battery capacity or 12v on it's output post. If it started without a reference voltage it would probably spike very high and destroy either/or itself and anything else attached to it.

[larrylwill]

Battery to Alternator to start the alternator, verified with other people and Nations starter.
Besides we talked about this problem in my thread.