Integrating Sterling B2B charger in RV w/Intellitec battery isolation setup

[GeorgeRa]

Originally Posted by woundedpig

…………………..
I'm still trying to understand this, but all the B2B charger manufacturers list wire sizing as an advantage to their systems because of the way the chargers work. Perhaps they mean on the house charging side, where voltage can be boosted to whatever the set algorithm demands, sort of similar to MPPT solar charger design………………………

B2B can boost voltage and compensated voltage drop on long distance wiring, valuable in camping trailers or semi-trucks, not necessary in B-class.
This question was asked before: Can you look at your Victron monitor and see charge current?, perhaps you have one with Bluetooth so you can see it on the smart phone.
Do you have a diesel or LPG Onan generator on board?

[woundedpig]

Why would the voltage boosting of a B2B not be just as feasible and worthwhile in a B class, where the wiring distance are far less, compared to a trailer or semi?

I have a 3.6 kw LP Onan. I have only seen alternator charging while the lithium bank was in a depleted state only a couple of times, so my N is small. Both times, I saw brief outputs of 60 amps, but tailing off quickly, due to the charge profile of the lithiums. I need to pay attention to this more obviously. There are a couple of folks on the Sprinter forum who have lithium banks from different manufacturers, and separate lithium chargers, who have noted as high as 80 amps, but also tailing off quickly. They have manual control over the charge cycle and just shut off charging when bank is full.

[avanti]

Originally Posted by woundedpig

Why would the voltage boosting of a B2B not be just as feasible and worthwhile in a B class, where the wiring distance are far less, compared to a trailer or semi?

I think he just means that the distances tend to be shorter in a B van, so the feature is less important.

I'm not sure I agree, though. The regulator for my second engine alternator is all the way in the front and my house batteries are way in the back. I am really glad that the regulator/charger has a "sense" input.

[woundedpig]

Originally Posted by avanti

I think he just means that the distances tend to be shorter in a B van, so the feature is less important.

I'm not sure I agree, though. The regulator for my second engine alternator is all the way in the front and my house batteries are way in the back. I am really glad that the regulator/charger has a "sense" input.

I was taking the comment and an earlier one, to mean that the 4 AWG wire in the LTV schematic (not my plan - the stock setup) was too small for its job. I just went out and did my best attempt at measuring the distance from the alternator to the relay to the house bank and it is around 9 feet. I would think the voltage boost would be important for a lot of applications, unless someone is running 1/0 or 2 AWG wire, which is not a typical choice.

[GeorgeRa]

B2B voltage booster is not the same as B2B charge controller. Sterling, KISAE, Enerdrive, Red Arc, CTEC provide charge control which is not just voltage boost like this one Powersaver Technologics Limited - Your Power Solution Partner.

Correction - Oops, seems Powersaver has B2B charge conroller now, so now it could be spliting a hair.

[booster]

I would advise everyone to be very careful if trying to control voltage by the cable size and length. It can work to some degree, but is very complicated in the real world of charging.

What you have to remember is that the voltage drop over a cable is variable with the amperage, so you might get a big voltage drop at initial charge with a big alternator, but no voltage drop at the end of charge. Depending on how the system is designed, this can be good or bad. From this it is obvious that it also matters which end of the cable the B to B charger is connected, if it has internal sensing, as the voltage it sees will be different based on amps.

Going further into it, even with a big alternator and a Baldor regulator, you will wind up with different absorption times depending on where the voltage sense wire is connected for all the above reasons. If you are coming of the factory alternator, you will have low voltage at the batteries to start, and the nearly alternator voltage at the end, assuming you use a relay style separator.

The different battery styles have different weaknesses when it comes to charging, and you have to be aware of all of them, from all charging sources, if you are going to have a top of the line charging system and long lasting batteries of any style.

For reference, we have allowed for voltage drop and the companion amps drop in setting up our alternator charging to the coach. We have a lot of over capacity, so we could easily overpower the batteries and overheat them and even the 530amps of alternator, but we turn the alternators down to a level to stay cool at max to the batteries that prevents heating. That setting can be maybe .2-.4v higher due to the voltage drop at those high amperages. We sense at the separator as our coach and starting batteries and alternators are not permanently separated and we don't want the voltage drop over the cable to overvoltage the van electronics and fry a computer.

[tgregg]

Originally Posted by woundedpig

I have only seen alternator charging while the lithium bank was in a depleted state only a couple of times, so my N is small. Both times, I saw brief outputs of 60 amps, but tailing off quickly, due to the charge profile of the lithiums.

If your current system charges at 60 amps and tails off as the batteries charge, what problem are you trying to solve with your proposed system?

And when you say 'tailing off quickly, due to the charge profile of lithiums' what do you mean?

My lithium batteries charge at 60 - 70+ amps depending on SOC ( I have 2awg wire connecting the house batteries to the chassis battery) but the current tails off to zero as they charge. It just doesn't tail off as quickly as AGMs do.

How are you measuring the state of charge? What is the charging voltage measured at the point your 4awg wire connects to your RV charging system? The voltage measured at the lithium batteries will be lower than the charger voltage until the batteries become charged.

[booster]

The charging profile of lithiums is most often touted as excepting pretty much as many amps as you can provide. If you have 100-200ah of lithium that will only accept 70 amps, there is something not normal in that. Plain old AGM batteries will accept more than that, so why spend $1000 per 100ah for the lithium?

[woundedpig]

What I mean is that the lithium batteries accept charge current pretty quickly. That is well known. I will pay more attention to alternator charging amps in the future and measure the volts at the battery at some point.
What problem am I trying to fix? Perhaps there is no problem, if the batteries charge reasonably fast **and** there is no concern about alternator overwork. From what I have observed from a lot of reading is that views on this range from zero worry to grave concern. People talk about their concern about a sizable lithium bank "sucking" huge amps from. the alternator. And again, all my RV has between the alternator/chassis battery and the house bank is a voltage sensitive relay/delay. I really have no clue what the numbers are, but surely a Sprinter driving down the road with a charged chassis battery and headlights or heater/AC on has enough amp reserve to charge a 300-400 AH house bank. Then there is the question of the lack of an appropriate charging algorithm when on alternator charging.

I will share one embarrassing anecdote. I stored the RV for a couple weeks, but, in a hurry, forgot to turn the battery disconnect switch to off. I may have left the lights in the back powered up also, as the unit is parked in enclosed storage and it was dark. A dumb move. Came back to a 15% state of charge. 200 AH bank. I should have watched the amps on the Victron, but after driving to fill with propane, fuel, and then to home, the batteries were recharged per my Victron BMV 702. That was in less than 90 minutes. I put the battery disconnect switch to off, turned off all the loads that I could and read 13.6 volts after 30 minutes. That was with 400 watts solar running also.

The other issue for those of us with B+/C class vans vs van conversions is that our cargo carrying capacity doesn't easily allow a large AGM or lead acid bank without a cost. Four AGM batteries would easily weigh 280 pounds, vs 112 pounds for four BattleBorn's. Some people who have installed their large AGM/LA banks are running above GVWR by their own report.

https://battlebornbatteries.com/comp...teries-series/

[booster]

What you stated are pretty much inline with what we all have heard in the past for lithiums. But..the numbers for charging, voltages, etc just haven't lined up to those parameters, in particular the 70 amps of charging maximum seen.

The discussion has veered a bit from the original direction, mostly I think because the biggest questions have not been resolved. It all comes down to two things.

* How much power do you need to store based on daily use, solar contributions, and driving.

* The above will give a number of amps you need to be able pull from the MB alternator. If that comes out to 40 amps of less, you are within the MB spec, and if it is over you have decide if you are willing to use more than that, with the possible issue risks.

Beyond that, the proposed B to B charger is a good way to limit current to the batteries as long as you can get on big enough for what you need (we can't but it shouldn't be an issue here). All of the wiring needs to be checked and upgraded to be able to carry whatever current you will have running in it.

A couple of notes, though. This is not addressing any of the lithium issues that seem to not even been addressed, that I saw, on the Battleborn site. High and low voltage cutoffs, high and low temp cutoffs, heater needs, temperature storage conditions and charging conditions, charger profiles and controls, etc.

We have to assume that you have the Victron meter setup with the right parameters and also that is getting fully cycled to it's "fully charged" parameters. If it does meet the properly set "fully charged" parameters on a charge cycle, it will not reset to showing true full and can get less accurate on the next cycle. If you don't get full on repeated cycles, it can get way off on the SOC %.

One thing to check out would be the Battleborn site cost comparison by total amp hours to worn out, which I do consider the best way to rate cost.

But, there calculations are severely off, math wise and assumption wise.

Using the numbers they list, and assuming the AGM batteries would have 1100 cycles at 50% discharge (200ah bank 100usable as listed), you would get 110,000ah of life, not 30,000ah as they say.

The calculation for the Battlebot is also off, but not to their favor. Here are how the numbers look to me, again only using their numbers plus the AGM cycle life shown above.

Battleborn --- .316 cents/ah, 100ah battery, probably 80-90ah usable

AGM --- .400 cents/ah, 200ah battery, 100ah usable at 50% down as used for cost, but 180ah available if needed occasionally with very minimal cost/ah increase.

AGm --- .510 cents/ah, 200ah battery, 160ah usable at 80% down (using 550cycle life for 80% down)

Quite different from the huge advantage to Battleborn that the website shows.

[tgregg]

Originally Posted by woundedpig

What I mean is that the lithium batteries accept charge current pretty quickly. That is well known. I will pay more attention to alternator charging amps in the future and measure the volts at the battery at some point.
What problem am I trying to fix? Perhaps there is no problem, if the batteries charge reasonably fast **and** there is no concern about alternator overwork. From what I have observed from a lot of reading is that views on this range from zero worry to grave concern. People talk about their concern about a sizable lithium bank "sucking" huge amps from. the alternator. And again, all my RV has between the alternator/chassis battery and the house bank is a voltage sensitive relay/delay. I really have no clue what the numbers are, but surely a Sprinter driving down the road with a charged chassis battery and headlights or heater/AC on has enough amp reserve to charge a 300-400 AH house bank. Then there is the question of the lack of an appropriate charging algorithm when on alternator charging.

I will share one embarrassing anecdote. I stored the RV for a couple weeks, but, in a hurry, forgot to turn the battery disconnect switch to off. I may have left the lights in the back powered up also, as the unit is parked in enclosed storage and it was dark. A dumb move. Came back to a 15% state of charge. 200 AH bank. I should have watched the amps on the Victron, but after driving to fill with propane, fuel, and then to home, the batteries were recharged per my Victron BMV 702. That was in less than 90 minutes. I put the battery disconnect switch to off, turned off all the loads that I could and read 13.6 volts after 30 minutes. That was with 400 watts solar running also.

The other issue for those of us with B+/C class vans vs van conversions is that our cargo carrying capacity doesn't easily allow a large AGM or lead acid bank without a cost. Four AGM batteries would easily weigh 280 pounds, vs 112 pounds for four BattleBorn's. Some people who have installed their large AGM/LA banks are running above GVWR by their own report.

https://battlebornbatteries.com/comp...teries-series/

Is the Intellec relay a 'voltage sensing relay' or simply a relay tuned on and off by the engine running signal (after the delay time)?

Is it the 100 amp model or the 200 amp model?

As for the charge profile anything that's less than 14.6v (measured at the source, not at the lithium battery) and more than 14.2v is okay per the Battle Born spec.

The important thing is turning off the charging when the battery is fully charged.

Can you set the float voltage on your solar system to match the Battle Born spec?

I have the Victron BM 712 instead of the 702 because Victron says it's more appropriate for Litium because it draws less current.

The relay in the 712 is also a latching relay and draws less current than the relay in the 702.

I use the relay in the Victron to control my battery combining relay.

It's in series with the engine running signal so it turns the combining relay on when the engine is running and the SOC of the battery is below 90 percent and it turns the combining relay off when the SOC is above 95 percent. The percentage are adjustable.

I can manually turn off the combining relay as well to prevent charging below freezing, but I've ordered a battery temperature sensor from Victron and I'm going to try and automate that feature using the 702 / 712 temperature relay parameter.

Once a month or so I charge the batteries with a shore power 10 amp LiFePo4 specific smart battery charger that shuts off when the batteries are fully charged just to reset the Victron BM 712 SOC.

I agree they charge much faster than my previous AGM batteries. A night's usage including a 12v refrigerator and running the furnace all night is recovered in an hour or so of driving.

They aren't damaged by being stored partially charged and most important to me they don't weigh 75 pounds each. Something I can't pick up anymore.

[booster]

There may also be another scenario the OP could use that might take care of staying clear of MB rules and also give him a good limit on his charging rate. It would not negate the need that have been mentioned by many here to accurately determine just how much charge rate he needs, but would just be an alternate solution if his amps needed was within a range that would work with the alternate method.

IMO, the biggest issue we see with engine generator, big alternator, systems is having to have all the components sized to handle the maximum output of the big alternator. All the wiring, relays, etc has to be able to handle nearly 300 amps, even though you don't net that much due to heat cycling.

For a system like the OP mentions that may only need 80amps maximum of charging, there might be an easier, less expensive, and reliable method to do that in a better way using an second alternator. Not as simple as just using the MB system with a B to B charger, but gives the benefit of no MB connections with less cost than the normal second alternator method.

It is likely that the OP has the previously mentioned 4ga cable to the coach batteries from the engine compartment, which is good for 80 amps continuous, even in sleeving, per the very conservative ratings. If that 80 amps is enough for the OP, no major rewiring would be needed, so that downside of an second alternator is taken away as long as the 80 amps is not exceeded.

At the 80 amps max, I think there would be two ways to handle the setup. Both would use the normal aftermarket second alternator bracket setup.

In the first setup, which I think I would do myself, you just get a 200-220 amp max, good quality, alternator, with an internal regulator and put an 80 amp B to B charger on it. The alternator would be much less expensive than the 280 amp Nations one that is commonly used. Fuse it at 120amps to protect things and put the B to B charger in the coach by the batteries so no voltage drop considerations or remote sensing. If the B to B has an alternator overtemp shutoff, that would be a bonus, but likely would not get that hot anyway. Add any relay disconnects, etc if you want. Done

The second method would be similar, but would use an externally regulated alternator of about 160amps and a Balmar external regulator. The Balmar can be set to run at 50% output maximum, so you would get the 80 amps. Remote sense the Balmar at the batteries. Temp sense on the Balmar would not be effective on this setup as it does the same 50% turn down.

Advantages of the first setup are predictability and more window on alternator sizing. You would also be able to get a replacement alternator in nearly any auto parts store. Downside is that you would need a different B to B charger to change amps if you wanted to.

Advantages of the second system would be a bit less of cost and the ability to change amps by changing the alternator instead of the B to B. Downside is lack of precise predictability and that the alternator would need to be run at 50% of rated, which could be pushing the temp limit on normal alternators.

Just some food for thought, if staying off the MB system is considered a desired thing to have (which it would be for me)

[BBQ]

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+1

KISS -- always a winner.