[Berk8520]

I have been thinking a lot about my electrical system (and the $1700 cart awaiting the "check out button" on Amazon ) and I really like some of the ideas that Orton has. Having a house AC system available but that does not draw from the batteries under way, also isolating and charging the very expensive house batteries the most efficient way. I was kicking around the idea below and was hoping for comments or suggestions on improving the idea.

Thanks! Berkeley

 

[tthrsn]

Can you provide details about the relays you will be buying?

 

[Bay Marine Supply]

That's a lot of relays. If I'm reading it right, when it's running you want the alternator/start battery to power the inverter which powers the battery charger which charges the house bank, and then to switch over to the house bank, and shut the charger, when the ignition is off. Here's why I think there's a simpler way:

Unless you have a massive battery charger, you won't get anywhere near the potential output from your alternator. I'm guessing that you're worried about depleting the house bank when underway with the inverter on, but a 1000W inverter at full continuous current draws about 80A, which the alternator would easily keep up with. And if you were idling and not putting out much current, the house bank would be in a better position to take up the slack than the start battery anyway. So if you took the path of least resistance (in more ways than one), and just put in an automatic relay between the start battery and the house bank to connect them when charging, you could get rid of the other three relays.

That also gives you the option to go with an inverter/charger (if desired) to save space and $$. Or, at least not having to put in a 70A charger (the most the inverter would power) to maximize charge when running.

There are devices that will help to max out the alternator and charge the battery faster, if that's on the agenda, but that's another story.

If you never plug in, there is a case to be made for having the charger for conditioning purposes, but if you plug in at least once or twice a month, that will usually cover you.

Or am I completely missing the point? (It's happened before, one or twice).

 

[tthrsn]

If you never plug in, there is a case to be made for having the charger for conditioning purposes, but if you plug in at least once or twice a month, that will usually cover you.

Could I ask you about this?

I have read (Lifeline Technical Manual p. 20) that AGMs are very sensitive to not being fully charged and that regular incomplete charging can lead to substantially reduced house battery life. In my application I plan to primarily use alternator charging because in the winter here solar panels are ineffective and serviced campsites are closed. Furthermore I don't intend to drive much each day (just enough to replace the amp-hours used the previous night via bulk charging) so getting through the absorption stage to a fully charged battery becomes a real problem.

To deal with this I am thinking about installing two house batteries and then alternately using one to give the other a full charge via a battery to battery charger. The intention is to get a full charge while protecting the starter battery and minimizing the amount of driving. Here's how it would work:

Morning 1 - House loads are on A which is now discharged to 60% and B is fully charged.
Drive 1 - Bulk charge A from alternator as much as possible during the day's driving, say to 90%.
Evening 1 - Switch loads to B and at the same time use B to complete the bulk and absorption phase of A using a battery to battery charger.

Morning 2 - House loads are on B which is now discharged to 60% and A is fully charged.
Drive 2 - Bulk charge B from alternator as much as possible during the day's driving, say to 90%.
Evening 2 - Switch loads to A and at the same time use A to complete the bulk and absorption phase of B using a battery to battery charger.

This pattern could be repeated indefinitely. I have attached a charging circuit diagram (ignoring fuses, shunts, low current switches, some devices etc.) and a switch table (showing some but not all of the possible settings and uses).

Question: Am I worrying too much about getting a full charge? Will plugging in at least once or twice a month actually give me full battery life?

Note that the incremental cost of this plan is not that large because with the monthly plug in plan I still would need an isolation relay, similar battery capacity for occasional long stationary periods, a battery to battery charger etc. I could eliminate a few switches, some wires, some installation time and some switch setting time each day.

I know that going with lithium batteries would avoid this issue but I'm not ready to do that yet. My next set of batteries (in ten years) will probably be lithium.

 

[orton]

There are advantages and disadvantages to any RV electrical design. For the two inverter design:

Advantages:
1. House battery is always charged with a 3 stage charger (bulk, absorb, float) with the correct charge profile for your house battery.
2. Two batteries of different size, type, make, age, mfg. or mfg. date are not connected together for charging.
3. The house electrical is not connected to the vehicle electrical.
4. 120 volt AC is available with engine running for heating water or heating air or charging.
5. The vehicle inverter limits the maximum load on the alternator.
6. The house 12 volt system does not need to be grounded to the chassis.
7. Does not require a large cable between the house battery and vehicle battery.
8. Does not require a relay connecting the house and vehicle batteries.
9. 120 volt power is available at all the duplex outlets with engine running and with the house inverter off. (If you have an inverter with a transfer switch)

Disadvantages:
1. Can not use a switch to connect house battery to vehicle battery in case vehicle battery will not start the engine.
2. The vehicle inverter limits the load on the alternator. You can only charge at the maximum output of the vehicle inverter.
3. Slightly higher cost.
4. Not what everyone else does.
5. Requires two inverters.

Block diagram of my system:

http://sprinter-source.com/forum/attachment.php?attachmentid=73320&stc=1&d=1453767929

Instead of relays I use three manual selector switches to direct the power to the function that I want to use. The normal setting is to direct the power to the house inverter/charger/transfer switch. The third selector switch was added to allow me to heat shower water with the house battery if weather conditions permit. If I know I will have unsed power available from the solar panel, I can use the houise battery for heating water.

The charging function using the vehicle inverter is a back up system only used if weather conditions force its use. Last year of Sprinter ownership did not require either shore power or vehicle inverter "shore power". All house battery charging was done with the 205 watt solar panel.

In Transit I have a 300 watt panel, Morningstar MPPT solar controller, Magnum MMS1012 inverter/charger/transfer switch and a 255 amp-hr. 8D AGM house battery.

Now back to comments about the "modified" Orton charging system. The diagram is not clear enough for me to clearly read on my computer. But is looks like you are using multiple relays to either use vehicle 12 volt power or power from the house battery to operate one inverter. This can be done with a simple battery selector switch. Select either of the two 12 volt sources to power the inverter. I looked at doing this but it ended up more complicated and not as fexible as the two inverter design.

An example using one inverter:
http://sprinter-source.com/forum/showpost.php?p=261334&postcount=29

Using the three relays and the wiring gets the cost closer to the two inverter system.

The slight extra cost of the two inverter system eliminates a costly hot water system or allows air heating. So net cost is less than the traditional RV design of connecting two different batteries together for charging.

This system is practical for a small RV that does not require massive amounts of power from the alternator. For my application it works well.

 

[stanw909]

I used this on my last van and it worked great for two years. Very simple , just take power from positive on starter battery, run cable to positive on your battery bank and ground to frame. I had 4 Optima blue tops and had very great results. I also had 100 watts of solar. http://www.godrules.net/store3/sunforce-60113-150-battery-isolator-2.htm . Had breaker inline also.

 

[Chance]

....cut....

The slight extra cost of the two inverter system eliminates a costly hot water system or allows air heating. So net cost is less than the traditional RV design of connecting two different batteries together for charging.

.....cut.....

Please remind me why you couldn't have the same hot water system or air heating with a single-inverter system?

All power comes from same sources, and is stored in same house batteries. I don't follow why or how the traditional one-inverter (or inverter/charger) system precludes powering hot water or air heating systems.:s

 

[orton]

Please remind me why you couldn't have the same hot water system or air heating with a single-inverter system?

All power comes from same sources, and is stored in same house batteries. I don't follow why or how the traditional one-inverter (or inverter/charger) system precludes powering hot water or air heating systems.:s

The power for heating water or air with a two inverter system is not stored in the house battery. Goes directly from the vehicle inverter to the heating element.

You could heat water or air with a one inverter system with engine running without reducing the SOC of the house battery.

The major advantage for the two inverter system is charging the house battery with a 3 stage charge with a correct charge profile to match your house battery.

 

[Chance]

The power for heating water or air with a two inverter system is not stored in the house battery. Goes directly from the vehicle inverter to the heating element.

You could heat water or air with a one inverter system with engine running without reducing the SOC of the house battery.

The major advantage for the two inverter system is charging the house battery with a 3 stage charge with a correct charge profile to match your house battery.

Thanks Orton. So as long as the alternator charge rate to house batteries (in a one inverter system) is as high as what is supplied to your vehicle inverter, then the systems' capabilities to heat water or air would be similar. And that could easily be over 1000 watts from Transit HD alternator. Even close to 1500 to 2000 watts may be possible.

What I'm still trying to find is to what degree battery life is affected by not having 3-stage charging. Ford obviously charges Transit AGMs with alternator, so how bad can that really be? As I mentioned before, even if I could extend battery life by some percent, how much is it worth spending for that incremental amount. For example, if you have $500 in house battery(ies), and 3-stage charging only extended life by 20% versus occasional 3-stage charging off shore power, then I'm only looking to save about $100 every time I replace the battery. And if this occurs no more often than once every two years, then spending an extra $50 a year or less on batteries doesn't justify much investment on added equipment.

I want to find hard data on 3-stage-charging's effect on battery life, but can only find statements that it's better. Unfortunately that it's "better" without "how much better" doesn't help me much.

 

[tthrsn]

I've read lots of stories about class A RV owners who were miffed when they had to replace big banks of house batteries in a year or two due to not fully or properly recharging them. That caused quite a stir for a while, until RV manufacturers learned to build in the proper charging systems.

And Chance, the equations change a quite bit as the battery bank gets bigger.

 

[orton]

Would think you have to be careful with inverter size powered by the Transit. There is a Transit electric air heater that provides warm cab air before the engine water gets warm. I think it is around 1000 watts. Ford does allow you to prevent it operating. If you do not turn the temperature dial to full hot then the electric air heater does not operate. At least that is my understanding.

The three Transit customer connections are rated at 60 amps. So anything larger than 1000 watts would require different battery connections.

I also like the idea of using the vehicle powered inverter to limit how much load you add to the alternator.

I have not seen any direct comparison tests between a proper 3 stage charge and an alternator charge. Have no idea how it affects battery life. Have read that it is difficult to get the last bit of float charging of the house battery from a alternator which is why a solar panel is a good solution if your weather conditions are appropriate.

I think the advantages are worth the extra $200. What is $200 when we paid about $40,000 for the vehicle.

This whole idea started because of my fear of connecting to the 08 Sprinters electrical system. Many stories about strange stuff happening with Sprinter electrical systems. The new CAN bus systems are more sensitive. Hopefully the Transit's CAN bus is a more robust design.

I do know that I do not have the fear driving with the Transit that I had with the Sprinter. Never knew when it would quit and was always thinking about how far away the service facility was located. It did quit twice in the first 20,000 miles so I had lost confidence in it.

 

[tthrsn]

Orton 3x60A at 12V is over 2000 watts.

 

[Bay Marine Supply]

Could I ask you about this?

I have read (Lifeline Technical Manual p. 20) that AGMs are very sensitive to not being fully charged and that regular incomplete charging can lead to substantially reduced house battery life.

This is a valid concern, but I don't think the batteries need to go through a full absorption cycle every time they are discharged. If they get to the point that they are taking only a few amps on most charges (ie: 98% or so full), and get an absorption now and then, they should be fine.

Note that getting a heavy charge does a lot to keep the sulphation under control, too. Kicking 20-25C into the battery will cover for not doing an absorption every cycle.

The OP's and Terry's idea of having two banks so one can get a full charge is intriguing. That would be good with a solar, since you could get one bank to 98% with the alternator, isolate it, and let the solar top it off all day - wouldn't need much current, it's the voltage that counts for absorption/equalization. With two banks, though, I'd be careful about bringing one down too far inadvertently - there's more "cushion" with bigger banks.

If you're planning on doing the inverter-to-charger setup, also plan on the losses - give or take 10% on the inverter and 10% on the charger, so you're using 120 AH to replace 100 AH.

I think all the ideas are great - well thought out solutions to the problem. My personal take, though, is usually to keep it as simple as possible. For instance, does a $1000 Honda generator cover for a weekly topping off, and save primary engine run time/fuel expense? And that also lets you use the charger in your inverter/charger, which is a whopping 100A in a typical 2000VA unit.

Also, for Terry - the batt-to-batt charger will only power up when the voltage is over about 13.2 (or thereabouts), as when charging. Wasn't sure if that was in your process. You wouldn't be able to charge from a battery at rest. But on alternator you could turn it to Batt A until it tapers, then switch to both, meaning A would be closer to the 100% point but you would still be getting some bulk into Batt B and not wasting run time.

 

[tthrsn]

... Note that getting a heavy charge does a lot to keep the sulphation under control, too. Kicking 20-25C into the battery will cover for not doing an absorption every cycle ...

Lifeline recommends charging at a bulk rate of at least 20% of C (and up to 500% of C). I'll be bulk charging at a rate of about 40% of C so that looks fine. I'm delighted to know that a high charge rate is a large part of the cure.

... Also, for Terry - the batt-to-batt charger will only power up when the voltage is over about 13.2 (or thereabouts), as when charging. Wasn't sure if that was in your process. You wouldn't be able to charge from a battery at rest ...

Thanks for the heads up on the start up voltage, I forgot about that. Luckily I might be able to work around it by energizing the unit's ignition fed cable when charging house battery to house battery (with the engine off). From the installation manual: "Remember the unit is voltage sensitive. Thus, If the input voltage is above 13.3V (due to alternator, generator or charger) the unit shall start and begin boosting - you can eliminate the voltage sensitive aspect by adding an ignition fed cable (refer to next page for operational modes)".

Later in the manual though it looks a little more complicated than that: "3) Regenerative braking Ignition feed activation. This mode is similar to 2) (above). Ignition feed to ~12V and link Auto w/ Low V. Initial activation input voltage is 13.3V. However, the sleep voltage is below 12.2V. If ignition feed is cut at any voltage the unit enters sleep. To get out of sleep the live feed must be re-established and the input voltage must be above 12.2V - 10 second delay". Maybe I'll have to put it into this sleep mode so that the "start up" voltage is 12.2V.

I'll reread the Sterling and Lifeline manuals more carefully with respect to start up and cutoff voltages and I may have to buy the Sterling unit and test it before finalizing my plans.

And if I can't force the Sterling unit do house battery to house battery charging then I'll work with your advice here:

... I don't think the batteries need to go through a full absorption cycle every time they are discharged. If they get to the point that they are taking only a few amps on most charges (ie: 98% or so full), and get an absorption now and then, they should be fine ...

Thanks for all your help.

 

[Budsky]

What I'm still trying to find is to what degree battery life is affected by not having 3-stage charging. Ford obviously charges Transit AGMs with alternator, so how bad can that really be? As I mentioned before, even if I could extend battery life by some percent, how much is it worth spending for that incremental amount. For example, if you have $500 in house battery(ies), and 3-stage charging only extended life by 20% versus occasional 3-stage charging off shore power, then I'm only looking to save about $100 every time I replace the battery. And if this occurs no more often than once every two years, then spending an extra $50 a year or less on batteries doesn't justify much investment on added equipment.

I want to find hard data on 3-stage-charging's effect on battery life, but can only find statements that it's better. Unfortunately that it's "better" without "how much better" doesn't help me much.

I used to run Optima Deep Cycle batteries in my company truck to power test equipment, and battery life in years was pretty poor. Of course in those days (6+ years ago) I'm not sure I even knew about proper AGM charging. I just had a simple relay- when the truck was running the Optima was paralleled with the starting battery to charge.
I was just glad I wasn't paying for those high dollar batteries every year or two.

 

[orton]

Orton 3x60A at 12V is over 2000 watts.

There are lots of unknowns about the Transit electrical system. Do not know how much power the van requires during its normal operation. What watts are consumed if the lights are on, the heater blower is running, radio on, 1000 watt air heater is on etc?

There is also a reference to a "Smart charging alternator" in the "Major Product Features" publication. I have no idea how the smart alternator functions. Maybe it increases the engine rpm when heavy electrical loads are applied?

I have the 220 amp alternator. At 14 volts that is around 3000 watts. That is its maximum output. If you look at the graphs of alternator output in the BEMM you will see that output is about 150 amps or 2100 watts at engine speed of 740 rpm. Deduct the power used by the Transit and you get less than 150 amps at low engine speeds. So at idle if I used all the 180 amps available at the CCP's then some of the power would be coming from the batteries.

I am not an expert on how this all works so want to be conservative. I will be careful not to run the Transit 1000 watt? air heater at the same time as I have the vehicle powered inverter running. I have selector switches that force only one use at a time. Charging or water heating or air heating. The charging will use the most power which would be about 830 watts at the charger's maximum 50 amp bulk charge rate. The water heating is 625 watts and the air heating is 750 watts. None of the loads have high startup current so will not push the inverter into its surge capacity.

I think it will work but would be concerned if I had a larger inverter powered by the Transit 12 volt system. Simply do not know enough about the Transit system nor the smarts to fully understand anyway. I had a 600 watt inverter powered by the Sprinter 12 volt system and it worked fine.

 

[tthrsn]

... I'll reread the Sterling and Lifeline manuals more carefully with respect to start up and cutoff voltages ...

I've looked at the manuals and it seems that as long as the alternator takes the target battery to about 90% charged, then the Sterling unit (in the regenerative braking mode) should be able to complete the house battery to house battery charge without cutting out due to low voltage in the source battery. The scheme that I have outlined seems viable.

 

[tthrsn]

There are lots of unknowns about the Transit electrical system ...

I agree, though the fact that Clean1 was able to charge at an average rate of 100 amps over three hours with the standard alternator leads me to believe that, while driving or at high idle, I should be able to charge at a rate of 120 amps (1500W) with the heavy duty alternator. I plan on using the connection points for this. We'll see how it works.

 

[tthrsn]

... Do not know how much power the van requires during its normal operation. What watts are consumed if the lights are on, the heater blower is running, radio on, 1000 watt air heater is on etc? ...

I was thinking of installing a shunt on the negative terminal of the alternator (would one work there?) and on the starter battery to measure exactly these sorts of things. But I suspect that my current plan is conservative enough and flexible enough that I don't have to know the exact boundaries of the Transit electrical system. And I'd have to buy something like the Pentametric to record the data. It'd be fun though.

 

[orton]

It would be nice to know what actually happens.

In my case I have enough solar power that charging from the alternator or shore power is normally not required. Only need it in case weather conditions force its use. So maximum charge amperage is not a requirement.

Look forward to hear your results with 1500 watts. If it works then I do not need to be concerned with the 1000 watt inverter. I think it will be OK but never know until I get it installed and use it.

The vehicle inverter will be one of the last things I do. Have the parts.