DC-to-DC + Isolator

[reilym]

Originally Posted by Rlum

Would you consider leaving wiring without changes? Change out the alternator to a 270 amp or 370amp? Do you think this would work for large battery bank without overloading the wires/fuses?

If I had your battery bank, I think a bigger alternator pushing more current would work fine and the two fat cables could handle 150 or 200 amps easily. With my two stock lithiums, I felt that 150 amps was too much for the batteries and for the alternator. If I add more battery capacity, I will need to rethink my setup. I like the 2nd alternator idea, but I am not sold on adding more hardware under that tight engine bay.

[Rlum]

Originally Posted by reilym

If I had your battery bank, I think a bigger alternator pushing more current would work fine and the two fat cables could handle 150 or 200 amps easily. With my two stock lithiums, I felt that 150 amps was too much for the batteries and for the alternator. If I add more battery capacity, I will need to rethink my setup. I like the 2nd alternator idea, but I am not sold on adding more hardware under that tight engine bay.

Just found out, going larger on alternator is not the way to go. Went to the Travato FB forum. Lots of folks are adding 600ah lithium banks.

They recommend Li BIM (lithium battery isolation management). Apparently some kind of smart battery bank separator. Prevents alternator overheating by turning on and off. FYI for people who do not like low amp charging of dc to dc chargers.

[@Michael]

Originally Posted by Rlum

\They recommend Li BIM (lithium battery isolation management). Apparently some kind of smart battery bank separator. Prevents alternator overheating by turning on and off. FYI for people who do not like low amp charging of dc to dc chargers.

Perhaps they are referring to the Precision Circuits LI-BIM?

From the Battleborn web site:

The LiFePO4 Battery Isolation Manager (BIM) monitors voltage and connects batteries when needed. Under normal charging conditions, the BIM will connect for 15 minutes every 35 minutes. That means that the BIM will connect for 15 minutes, disconnect for 20 minutes, and repeat this cycle until the coach battery is charged.

[Bud]

Originally Posted by Rlum

Just found out, going larger on alternator is not the way to go. Went to the Travato FB forum. Lots of folks are adding 600ah lithium banks.

They recommend Li BIM (lithium battery isolation management). Apparently some kind of smart battery bank separator. Prevents alternator overheating by turning on and off. FYI for people who do not like low amp charging of dc to dc chargers.

Something like this:

https://www.amazon.com/Battle-Born-B.../dp/B07DY8S815

What are they doing with the 600 amps? add'l inverter? a/c?......

[reilym]

Originally Posted by Rlum

Just found out, going larger on alternator is not the way to go. Went to the Travato FB forum. Lots of folks are adding 600ah lithium banks.

They recommend Li BIM (lithium battery isolation management). Apparently some kind of smart battery bank separator. Prevents alternator overheating by turning on and off. FYI for people who do not like low amp charging of dc to dc chargers.

This never really made sense to me. The alternator is pushing unregulated current to the coach batteries for 15 minutes and nothing for 20 minutes. That's a 43% duty cycle. If the battery is taking 150 amps during the 15 minute charge cycle, that amounts to 64 amps on average. Why isn't a steady 60 amps from DC-DC charger (which is less money) easier on both the alternator and the battery? Also, while the BIM is isolating the batteries, the loads (fridge, etc) will be draining the battery making for many discharge/charge cycles.

[booster]

I don't get it either. Average amps are what counts do if you are going to cycle the alternator it is much better to do it off temps rather than time, IMO.


Low amp charging off a B to B is not necessarily so. You can get a 120 amp B to B from Sterling the last time I looked and they were working on a 180 amp one.


Bottom line you can keep the alternator from getting hot by reducing output so it can run continuously without over heating or cycle it on and off to do the same thing. Net average amps will likely be similar but I prefer reduced output and not cycling. Cycling to high/low load puts big thermal cycles on all the alternator parts which can shorten life.


I think all those folks pushing their isolator control cycling on a timer don't seem to understand something or are justifying their choice.


A 600ah lithium setup needs a second alternator if you want to get them charged in any reasonable amount of time, IMO.

[@Michael]

[QUOTE=booster;133512]I don't get it either. Average amps are what counts do if you are going to cycle the alternator it is much better to do it off temps rather than time,[QUOTE]

Adding to that line of thought, if I charge with a 60A B2B at 100% duty cycle instead of 120A at 50% duty, I can use smaller gauge, easier to route wiring.

Originally Posted by booster

A 600ah lithium setup needs a second alternator if you want to get them charged in any reasonable amount of time, IMO

For me, I can see a large bank without fast charging as being useful if I were driving longer distances between sites and staying longer at each, or occasionally staying at electric sites and recharging overnight.

[Rlum]

https://www.youtube.com/watch?v=u8wnqlNguYw

I recommend installing an LI-BIM-225 instead of a DC-DC converter. The DC-DC converter is a more difficult install to get right (tricky to install without losing boost function and needs special cabling), and charges very slow. The high current charging that is dangerous to the alternator only happens for the first 20-30 minutes when the batteries are really low (under 10% soc), which shouldn't be enough to overheat the alternator, especially with the LI-BIM duty cycle of 15 minutes.

Found this on FB Travato Forum from someone who installs for other owners. Any thoughts on his boost function and special cabling?

Thanks

[booster]

Originally Posted by Rlum

I recommend installing an LI-BIM-225 instead of a DC-DC converter. The DC-DC converter is a more difficult install to get right (tricky to install without losing boost function and needs special cabling), and charges very slow. The high current charging that is dangerous to the alternator only happens for the first 20-30 minutes when the batteries are really low (under 10% soc), which shouldn't be enough to overheat the alternator, especially with the LI-BIM duty cycle of 15 minutes.

Found this on FB Travato Forum from someone who installs for other owners. Any thoughts on his boost function and special cabling?

Thanks

If you have a decent size bank 20-30 minutes isn't going to give you much charge toward filling the batteries, since most factory alternators are probably going to be in the 80-130ish range of output. Only 40-65 amp hours per hour at best. Especially with lithium, it should go back up to that range of acceptance until you get to near full. If they are charging the previously mentioned 600ah banks from a deep discharge they are going to be at it a while, like a 10 hour driving day.


I could see it if you were a low to moderate power user and needed to recover a day's power to stay a day longer, but I just don't see the benefit for big banks.


Are these diode type isolation or are the contactors?


On edit: I think if I wanted to use the standard alternator and not overheat it without a B to B, I would go with one of these instead as they actually limit the current rather than turn it on and off. They come in 40 and 90 amp versions for the coach battery, with the starting battery having priority and no limit as it will turn down the coach battery rate.


https://www.mastervolt.com/products/...e-mate-pro-90/

[Davydd]

I know the MB Sprinter alternator can contribute 40ah to the house battery while driving. I don’t know about the Chevy, Promaster and Transit alternators but it cannot be good to be outputting at a maximum rate while driving. If say I use 200ah overnight with an all electric Sprinter cooking, coffee making, charging iPhones, lights, and misc. electrical (about the maximum sans any CPAP and AC) it would require 5 hours of driving with just the chassis alternator to replenish. So far I’ve been using about 150a maximum in an overnight stay on the average. Whereas with my second alternator it would easily replenish a night’s stay in less than 30 to 45 minutes of driving. I can get a steady 270a+ for an hour with my Delta 330 second alternator. I have 576ah lithium ion battery capacity with no solar. I actually reduced my capacity down from 800ah from my previous van considering I do drive just about every day and rarely stay more than 2-3 days sitting at a CG without shore power. You have to get out and about anyway just to sightsee, go to trailheads, restaurants, shopping, etc. I rarely use air conditioning since I like to travel in the proverbial 70 degree temperatures depending on the season and locations.

BTW, high capacity lithium battery systems and second alternators make solar unnecessary in the overall picture unless set up and needed or desired for long term storage outdoors. Every day touring and camping they contribute nothing compared to their cost and maintenance and with active vans where you use your roof for observation, bikes, kayaks and storage they can be a hogging real estate nuisance. I also had 460w solar on my previous van and that much didn’t contribute diddlely. I learned.

[Rlum]

Originally Posted by booster

If you have a decent size bank 20-30 minutes isn't going to give you much charge toward filling the batteries, since most factory alternators are probably going to be in the 80-130ish range of output. Only 40-65 amp hours per hour at best. Especially with lithium, it should go back up to that range of acceptance until you get to near full. If they are charging the previously mentioned 600ah banks from a deep discharge they are going to be at it a while, like a 10 hour driving day.


I could see it if you were a low to moderate power user and needed to recover a day's power to stay a day longer, but I just don't see the benefit for big banks.


Are these diode type isolation or are the contactors?


On edit: I think if I wanted to use the standard alternator and not overheat it without a B to B, I would go with one of these instead as they actually limit the current rather than turn it on and off. They come in 40 and 90 amp versions for the coach battery, with the starting battery having priority and no limit as it will turn down the coach battery rate.


https://www.mastervolt.com/products/...e-mate-pro-90/

Sorry, I do not know if diode or contractors.
As a side note. I run my gas genny to charge the battery bank. it puts out about 80-85 amps per Victron712. Very quiet so will get with alternator 100ah plus 80 or 180. Seems way more than what is needed for me since I stay 4 nights at a site. Use about 170ah per evening. So use generator to recharge lithiums.

[avanti]

Originally Posted by Davydd

I know the MB Sprinter alternator can contribute 40ah to the house battery while driving. I don’t know about the Chevy, Promaster and Transit alternators but it cannot be good to be outputting at a maximum rate while driving.

The Transit (which I have been looking at carefully) has a much more sophisticated and capable PTO system than the Sprinter. They support 60A unconditionally, but up 175A (and in some cases 200A) by use of the load-shedding signal which I have mentioned before. It also can automatically adjust idle speed in response to PTO conditions. I believe that if one follows the engineering guidelines, these currents should be perfectly safe.

Originally Posted by Rlum

The high current charging that is dangerous to the alternator only happens for the first 20-30 minutes when the batteries are really low (under 10% soc), which shouldn't be enough to overheat the alternator, especially with the LI-BIM duty cycle of 15 minutes.

Sorry, I just can't get my head around a design philosophy in which one deliberately builds a system that drives a component beyond its steady-state capabilities in hopes that you may not be doing it long enough to do harm.

Note also that the charge current data that I have posted showed evidence of temperature cycling at 5-10 minute intervals and did so for an hour. And, that was with FLA batteries. This isn't so bad with the Balmar, which simply throttles back the current. If it were doing bang-bang on/off, it would scare me.

Originally Posted by booster

I don't get it either. Average amps are what counts do if you are going to cycle the alternator it is much better to do it off temps rather than time, IMO.

Low amp charging off a B to B is not necessarily so. You can get a 120 amp B to B from Sterling the last time I looked and they were working on a 180 amp one.

Bottom line you can keep the alternator from getting hot by reducing output so it can run continuously without over heating or cycle it on and off to do the same thing. Net average amps will likely be similar but I prefer reduced output and not cycling. Cycling to high/low load puts big thermal cycles on all the alternator parts which can shorten life.

I think all those folks pushing their isolator control cycling on a timer don't seem to understand something or are justifying their choice.

A 600ah lithium setup needs a second alternator if you want to get them charged in any reasonable amount of time, IMO.

Agree. It seems obvious to me that a B-B is the correct tool for this situation. Since they can be used in parallel, you can have all the current you think is prudent. Combined with the Ford dual-alternator power management system, it seems pretty optimal to me. With proper selection of B-B, you can easily meet the guidelines of any OEM.

There is also a small community that advocates using a DC-AC-DC approach, using a dedicated inverter used to power your existing charger. Other than efficiency, this is also a reasonable approach, since choice of inverter will inherently limit current.

[booster]

Originally Posted by Rlum

Sorry, I do not know if diode or contractors.
As a side note. I run my gas genny to charge the battery bank. it puts out about 80-85 amps per Victron712. Very quiet so will get with alternator 100ah plus 80 or 180. Seems way more than what is needed for me since I stay 4 nights at a site. Use about 170ah per evening. So use generator to recharge lithiums.

Unless the voltages match identically, at the the battery not their sources, one or the other of the sources is not going to contribute as much to the charging as it would by itself. Depending on how it all splits up, which will likely be highly variable because alternator voltage varies a lot over time, you could be wasting a lot of generator time. Have you ever seen the 80 amps plus the 150 amps that you listed for the individual sources, at the same time to the batteries?

[ovsa]

To those that have replace their 4 post chevy RT isolators with the Renogy DC2DC charger, what do u do with the extra wires coming of the relay and the two switches on top?

[Rlum]

Originally Posted by booster

Unless the voltages match identically, at the the battery not their sources, one or the other of the sources is not going to contribute as much to the charging as it would by itself. Depending on how it all splits up, which will likely be highly variable because alternator voltage varies a lot over time, you could be wasting a lot of generator time. Have you ever seen the 80 amps plus the 150 amps that you listed for the individual sources, at the same time to the batteries?

Hi: I have seen 80 amps from my inverter/charger using genny and another 100 amps from alternator. Total of 180 amps. I have only seen one time. Generally do not run down battery bank so it was a one time test. I like using my generator to charge bank with new inverter uses way less gas and creates less noise. For it to produce 80 amps, genny would be running about 1/2 load or about .25 gallon/minute.

If I wanted to get a decent 80 amp dc to dc charger, what would guys recommend? I want something easy to wire. Use the existing 2.0 guage wire from separator to bank. Easy to adjust settings. I really like Victron smart products for this. I have both MPPT solar controller and 712 BMS.
Do not need all bells and whistles, you guys use. Just something easy adjust for lithiums, dependable, won't break bank and easy to wire.

Thanks

[reilym]

Originally Posted by booster

On edit: I think if I wanted to use the standard alternator and not overheat it without a B to B, I would go with one of these instead as they actually limit the current rather than turn it on and off. They come in 40 and 90 amp versions for the coach battery, with the starting battery having priority and no limit as it will turn down the coach battery rate.


https://www.mastervolt.com/products/...e-mate-pro-90/

This is an interesting looking device... It appears to be a essentially a current limiting smart battery isolator. If I can mount this under the hood where the battery separator used to be, I could potentially replace my DC-DC charger, clear up valuable space under the ottoman, and get up to 50% more charging current. It would also minimize the initial alternator load while the starter battery gets topped off. The IP65 rating would suggest that external mounting is OK, but the 148F operating temperature limit might be too low for under hood operation. Do you see any downside to replacing the DC-DC charger with one of these?

I have emailed Mastervolt for more details. As an aside, PleasureWay is using Mastervolt DC-DC chargers in at least some of their coaches (like the Lexor) now.

[Rlum]

Originally Posted by reilym

This is an interesting looking device... It appears to be a essentially a current limiting smart battery isolator. If I can mount this under the hood where the battery separator used to be, I could potentially replace my DC-DC charger, clear up valuable space under the ottoman, and get up to 50% more charging current. It would also minimize the initial alternator load while the starter battery gets topped off. The IP65 rating would suggest that external mounting is OK, but the 148F operating temperature limit might be too low for under hood operation. Do you see any downside to replacing the DC-DC charger with one of these?

I have emailed Mastervolt for more details. As an aside, PleasureWay is using Mastervolt DC-DC chargers in at least some of their coaches (like the Lexor) now.

Very interesting! Will wait to see what you find out. Thanks everyone. Great ideas and input!

[markopolo]

Originally Posted by reilym

................. Do you see any downside to replacing the DC-DC charger with one of these? ................

There's no specific voltage control with the Charge Mate. A DC-DC charger allows you to choose a specific voltage and/or a LFP specific charge profile such as no float for example.

[booster]

Originally Posted by markopolo

There's no specific voltage control with the Charge Mate. A DC-DC charger allows you to choose a specific voltage and/or a LFP specific charge profile such as no float for example.

That is the same problem that the previous LiBIM has. Certainly not a good for the batteries or getting to a consistent charge as the alternator is going to be controlling itself and choosing voltage and field current.


The benefit over the LiBIM is that this controls output so no thermal cycling, which is a big deal.


IMO, the best setup is still a B to B with settable voltage so you can charge the lithium to a set voltage and thus SOC consistently. I choose the Mastervolt over the LiBIM by a large margin with only those choices.



One thing that is basically unknown with the alternator charging is what effect the ripple in voltage has on lithium batteries which have a lot of electronics in them. Some alternators have 10% or more and the better ones still around 6% and I am pretty sure the worst is under high load situations. Lead acid batteries work sort of like a big capacitor to help smooth that out and it has no major affect on them that I know of. We haven't heard of wholesale problems to this point, but would be interesting how much ripple lithium batteries can handle, especially the BMS.

[GeorgeRa]

Originally Posted by booster

On edit: I think if I wanted to use the standard alternator and not overheat it without a B to B, I would go with one of these instead as they actually limit the current rather than turn it on and off. They come in 40 and 90 amp versions for the coach battery, with the starting battery having priority and no limit as it will turn down the coach battery rate.

https://www.mastervolt.com/products/...e-mate-pro-90/

I was looking for such a device before I installed my Magnum ME-SBC but didn’t find one. ME-SBC is OK but it limits current to 25A and I wanted 40A. If demand is higher than 30A it cycles on/off until demand drops below 30A (or 25A, I don’t remember) so it can take 30min. of driving to stay on.
https://www.donrowe.com/Magnum-Energ...hoC6QEQAvD_BwE