Replacing an Oshkosh large-frame alternator would be very expensive...and the entire rest of the truck, from starter motor, to half a dozen computers, to dozens of exterior light bulbs, not to mention the wiring sizes, are all designed for 24V...
Exploiting a large alternator via battery-to-battery chargers?
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Replacing an Oshkosh large-frame alternator would be very expensive...and the entire rest of the truck, from starter motor, to half a dozen computers, to dozens of exterior light bulbs, not to mention the wiring sizes, are all designed for 24V...
Sorry I assumed was just an auxiliary unit
I'm working on a sketch for a system based upon a 24-volt house battery bank, and so I'm looking for 24VDC to 24VDC chargers that are either large and/or can be paralleled to get me to (or near) the 0.4C point on a 200Ah 24-volt lithium house battery bank (80A), and I'm not finding a lot of options.
So I went back to my 12-volt sketch, and started looking for 24VDC to 12 VDC chargers to do something similar- something either large and/or that can be paralleled, to get me to (or near) the 0.4C point on a 400Ah 12-volt lithium house battery bank (160A) and I'm finding more choices. Some of the first ones that I looked at did not have adjustable output voltage...
...but then I found the Victron Orion 24/12-70. It has adjustable output voltage, and if I parallel two of them, I will have 140A (rated) of charging current. They're less than $150 each, and they're fan-cooled. My only concern is that the spec sheet says that they max out at 85A, which would be 170A with two of them in parallel, which would be 0.425C.
Is that bad for the batteries? Under what conditions would it even go beyond it's rated output to reach it's max output? I read 96 pages of Orion downloads this morning, and I don't see a 24VDC to 24VDC version- is there one?
So I went back to my 12-volt sketch, and started looking for 24VDC to 12 VDC chargers to do something similar- something either large and/or that can be paralleled, to get me to (or near) the 0.4C point on a 400Ah 12-volt lithium house battery bank (160A) and I'm finding more choices. Some of the first ones that I looked at did not have adjustable output voltage...
...but then I found the Victron Orion 24/12-70. It has adjustable output voltage, and if I parallel two of them, I will have 140A (rated) of charging current. They're less than $150 each, and they're fan-cooled. My only concern is that the spec sheet says that they max out at 85A, which would be 170A with two of them in parallel, which would be 0.425C.
Is that bad for the batteries? Under what conditions would it even go beyond it's rated output to reach it's max output? I read 96 pages of Orion downloads this morning, and I don't see a 24VDC to 24VDC version- is there one?
Your decision as to whether go 24V vs 12V should be based on more than a cursory search for available chargers, tail wagging the dog.
The Ah capacity size should also be determined by your daily consumption rate, and how many days' buffer you need.
Don't be too hung up on the 0.4C bit, that is just a rough guideline for maximum longevity, plenty go faster, going over by a little is NBD, and many are far lower. Do you always need to be charging as fast as possible?
It is the nature of LFP to draw at a very high rate, the point of a DCDC is to **limit** that draw in a controlled fashion.
Is that Orion an actual charger - automatically stops charging when its algorithm determines the target bank is Full?
Or just a DC-DC converter like a PSU you need something external to determine the stop charge?
Personally I would just stick with Sterling by default. Very few other DCDC allow for current rate or setpoint adjustment, and they definitely could be paralleled.
If you are getting into Victron, do not buy on price, establish a relationship with a knowledgeable dealer and pay their extra margin for support.
Alan Farber at Bay-Marine, and Bruce @OceanPlanet are good if you don't have one local.
The Ah capacity size should also be determined by your daily consumption rate, and how many days' buffer you need.
Don't be too hung up on the 0.4C bit, that is just a rough guideline for maximum longevity, plenty go faster, going over by a little is NBD, and many are far lower. Do you always need to be charging as fast as possible?
It is the nature of LFP to draw at a very high rate, the point of a DCDC is to **limit** that draw in a controlled fashion.
Is that Orion an actual charger - automatically stops charging when its algorithm determines the target bank is Full?
Or just a DC-DC converter like a PSU you need something external to determine the stop charge?
Personally I would just stick with Sterling by default. Very few other DCDC allow for current rate or setpoint adjustment, and they definitely could be paralleled.
If you are getting into Victron, do not buy on price, establish a relationship with a knowledgeable dealer and pay their extra margin for support.
Alan Farber at Bay-Marine, and Bruce @OceanPlanet are good if you don't have one local.
DiploStrat
Expedition Leader
And I rarely disagree with you - but until you provide some examples of your own installation(s), and what you have done right and wrong, it can be tricky to judge your creds. You must admit that you tend to be a bit judgmental of any of us who don't have the good fortune to build with a clean sheet of paper and an unlimited budget.
(And yes, you are completely correct that an integrated design, from one end to the other, is much better.)
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So can somebody explain to me Sterling's A to B (Alternator to Battery) chargers? They have two 24VDC to 24VDC models(100A and 200A), but after scouring the web site and reading all of the downloadable manuals and spec sheets, I'm still not clear.
It appears that they "trick" the alternator's integral regulator into thinking there is a load on it, which causes the alternator to ramp up it's amperage output, to the point that it drags down the voltage. Then the A to B takes that increased alternator output and converts it to a higher voltage. It then functions like a DC-DC smart charger, to charge the house bank as efficiently as possible.
One of the things that confuses me, is that they appear to be sized by alternator output, not by the output of the A to B charger itself.
So will these things effectively "hot wire" the alternator until it burns up, or what? Our truck has a military-grade large-case 150-amp alternator, but I don't want to run it wide-open until it fails- I'd like to take a lot of power from it, but still be within relatively safe operating conditions.
The whole point of using a DC-DC charger, was so that a large discharged lithium house bank doesn't smoke my alternator when recharging...
It appears that they "trick" the alternator's integral regulator into thinking there is a load on it, which causes the alternator to ramp up it's amperage output, to the point that it drags down the voltage. Then the A to B takes that increased alternator output and converts it to a higher voltage. It then functions like a DC-DC smart charger, to charge the house bank as efficiently as possible.
One of the things that confuses me, is that they appear to be sized by alternator output, not by the output of the A to B charger itself.
So will these things effectively "hot wire" the alternator until it burns up, or what? Our truck has a military-grade large-case 150-amp alternator, but I don't want to run it wide-open until it fails- I'd like to take a lot of power from it, but still be within relatively safe operating conditions.
The whole point of using a DC-DC charger, was so that a large discharged lithium house bank doesn't smoke my alternator when recharging...
You pretty much got it.
They functionally do the same thing as the B2B units
but only work with old-school USA style dumb VRs
not more modern Euro style vehicles engineered with electronics maximising mpg efficiency.
Sterling's ampacity ratings are deceptive, based on the maximum input tolerated.
Given conversion inefficiencies, the maximum output is a fair bit lower.
The whole point wrt current is to **prevent** the alt from getting burned up.
Normal alt/VR may (or may not) have overcurrent "protection" against too high a draw, but when that kicks in charging is in effect halted. Same with overtemp conditions.
With the DCDC in between, you can throttle down the amps drawn by your thirsty bank, until you find the output level your vehicle alt/VR can safely produce continuously.
Which is usually far below the alt max output rating.
With lead banks, usually current is not an issue, most chemistries only pull sub C rates.
But LFP will try to draw currents **far** higher than what is healthy for them, and can easily fry stock alternators.
But voltage issues alone often justify DCDC regulation.
They can often be stacked in parallel to increase current if needed.
My reco is Sterling's BB series, consider it part of the LFP bank, rather than the vehicle.
Lets you use any old charge source, no need for fancier mains chargers / DC genset / solar controllers.
Should outlive whatever vehicles you put it in.
They functionally do the same thing as the B2B units
but only work with old-school USA style dumb VRs
not more modern Euro style vehicles engineered with electronics maximising mpg efficiency.
Sterling's ampacity ratings are deceptive, based on the maximum input tolerated.
Given conversion inefficiencies, the maximum output is a fair bit lower.
The whole point wrt current is to **prevent** the alt from getting burned up.
Normal alt/VR may (or may not) have overcurrent "protection" against too high a draw, but when that kicks in charging is in effect halted. Same with overtemp conditions.
With the DCDC in between, you can throttle down the amps drawn by your thirsty bank, until you find the output level your vehicle alt/VR can safely produce continuously.
Which is usually far below the alt max output rating.
With lead banks, usually current is not an issue, most chemistries only pull sub C rates.
But LFP will try to draw currents **far** higher than what is healthy for them, and can easily fry stock alternators.
But voltage issues alone often justify DCDC regulation.
They can often be stacked in parallel to increase current if needed.
My reco is Sterling's BB series, consider it part of the LFP bank, rather than the vehicle.
Lets you use any old charge source, no need for fancier mains chargers / DC genset / solar controllers.
Should outlive whatever vehicles you put it in.
DiploStrat
Expedition Leader
Sterling products had their genesis on English narrow (canal) boats when Charles Sterling Sr. tried to find a way to get better performance out of large, deep cycle, "house" or camper batteries. He figured out that the low voltages of most alternators were a real problem as they could not overcome the internal resistance of the large lead acid battery banks in use. He started demonstrating that ramping the voltages up to the stratosphere of 14v greatly reduced the charge time and improved battery life by reducing sulfation. (This at, perhaps, the cost of extra water for the batteries.) This gelled into his line of A2B and B2B. And it spawned lots of competition.
When the alternator manufacturers responded with new systems that ran at 14v, Chris Gibson, of SmartGauge fame. (http://www.smartgauge.co.uk/) responded touting the advantages of intelligent relays. The Blue Sea ACR is very popular with many of us.
But note that both of these gentlemen were saying the same thing - lead acid needs higher voltage; how you get it is up to you.
I installed a A2B on my Chevrolet back in the day. It works as advertised, but had a 15v hard maximum input, so when, in cold weather, the Chevrolet ramped up to 15.5v, the Sterling alarmed and shut down. (Newer models may take up to 16v, but as noted, this is a much older product.) It had a temp probe to protect the alternator from overheat. Once I realized that the regulator/computer on my Chevrolet was accomplishing the same thing as the A2B, I sent it back to Charlie (Jr.) - who runs Sterling Power USA, and went with a large intelligent relay system. I confess that I never really understood the advantages of the A2B vs. the B2B, but it soon became moot.
Life was good. Who needs those bulky, inefficient, heat producing B2B's?
Enter lithium batteries and, a bit like ink jet printers getting a new lease on life with color, suddenly a B2B was looking like essential kit. But not to boost voltage, but rather as a buffer between the black hole of a large (or even not so large) discharged lithium battery and your alternator. Modern US pickups are sprouting ever larger alternators, running at nice high voltages, but most are not real high capacity units, rated for a 100% duty cycle. I suspect that most are aimed at advertising bragging rights or, perhaps, which type loads.
A modern B2B still works the same way and still gives you the profile of your choice, but now it may actually reduce the input voltage and, most important of all, it will never draw more than its rated load. So, if your B2B is rated at around 50% of your alternators - say a 70-100A B2B on a truck with alternators rated at 200A, you should be a happy camper.
You could, of course, replace the factory alternator with a real, high capacity unit, but increasing this would put you in conflict with an elaborate computer system, one whose manufacturer will not document to you. With a B2B you are nicely insulated from all of this, the front end of the B2B presents a simple, dumb load to the vehicle battery, typically shutting off if the battery drops to a target voltage, say 13v. Most vehicles can stand that all day, especially if the draw is only about 50% of the peak output of the alternators.
Techie Digression - For an overland camper, what you REALLY want is an alternator/regulator system sized for your camper battery. Then from that you can install a small engine starting battery, fed by a small B2B. If you have the skills, and an older, simpler truck, this may not be that hard. With a modern, computerized truck, it is probably impossible.
In my case, a B2B solved my problem of integrating a 24v truck and a 12v camper. I went with REDARC as they approached me first and their unit is wonderfully easy to install as it is small and has no fan. (I have the older version of this: https://redarcelectronics.com/products/dual-input-50a-in-vehicle-dc-battery-charger) Had I known that Sterling had a larger unit (https://www.sterling-power-usa.com/...-12volt-dc-to-dc-batterytobatterycharger.aspx) I might have gone with it as I have the space. The REDARC allows you to get some of your power from a solar panel, the Sterling lets you develop your own profile, which may especially important with home brew batteries.
So buy the appropriate B2B and B happy!
(As always, apologies for id skids or typos.)
When the alternator manufacturers responded with new systems that ran at 14v, Chris Gibson, of SmartGauge fame. (http://www.smartgauge.co.uk/) responded touting the advantages of intelligent relays. The Blue Sea ACR is very popular with many of us.
But note that both of these gentlemen were saying the same thing - lead acid needs higher voltage; how you get it is up to you.
I installed a A2B on my Chevrolet back in the day. It works as advertised, but had a 15v hard maximum input, so when, in cold weather, the Chevrolet ramped up to 15.5v, the Sterling alarmed and shut down. (Newer models may take up to 16v, but as noted, this is a much older product.) It had a temp probe to protect the alternator from overheat. Once I realized that the regulator/computer on my Chevrolet was accomplishing the same thing as the A2B, I sent it back to Charlie (Jr.) - who runs Sterling Power USA, and went with a large intelligent relay system. I confess that I never really understood the advantages of the A2B vs. the B2B, but it soon became moot.
Life was good. Who needs those bulky, inefficient, heat producing B2B's?
Enter lithium batteries and, a bit like ink jet printers getting a new lease on life with color, suddenly a B2B was looking like essential kit. But not to boost voltage, but rather as a buffer between the black hole of a large (or even not so large) discharged lithium battery and your alternator. Modern US pickups are sprouting ever larger alternators, running at nice high voltages, but most are not real high capacity units, rated for a 100% duty cycle. I suspect that most are aimed at advertising bragging rights or, perhaps, which type loads.
A modern B2B still works the same way and still gives you the profile of your choice, but now it may actually reduce the input voltage and, most important of all, it will never draw more than its rated load. So, if your B2B is rated at around 50% of your alternators - say a 70-100A B2B on a truck with alternators rated at 200A, you should be a happy camper.
You could, of course, replace the factory alternator with a real, high capacity unit, but increasing this would put you in conflict with an elaborate computer system, one whose manufacturer will not document to you. With a B2B you are nicely insulated from all of this, the front end of the B2B presents a simple, dumb load to the vehicle battery, typically shutting off if the battery drops to a target voltage, say 13v. Most vehicles can stand that all day, especially if the draw is only about 50% of the peak output of the alternators.
Techie Digression - For an overland camper, what you REALLY want is an alternator/regulator system sized for your camper battery. Then from that you can install a small engine starting battery, fed by a small B2B. If you have the skills, and an older, simpler truck, this may not be that hard. With a modern, computerized truck, it is probably impossible.
In my case, a B2B solved my problem of integrating a 24v truck and a 12v camper. I went with REDARC as they approached me first and their unit is wonderfully easy to install as it is small and has no fan. (I have the older version of this: https://redarcelectronics.com/products/dual-input-50a-in-vehicle-dc-battery-charger) Had I known that Sterling had a larger unit (https://www.sterling-power-usa.com/...-12volt-dc-to-dc-batterytobatterycharger.aspx) I might have gone with it as I have the space. The REDARC allows you to get some of your power from a solar panel, the Sterling lets you develop your own profile, which may especially important with home brew batteries.
So buy the appropriate B2B and B happy!
(As always, apologies for id skids or typos.)
DiploStrat
Expedition Leader
This is one of the best/most interesting ideas I have heard in a while. Got any examples/plans? How would you do this in the real world?
Sorry no idea what is unusual or in need of more detail?
As an extreme example, imagine a big ammo can containing your cells, a BMS and a Sterling BB, with outside switches, ports / terminals and a voltmeter or BM gauge.
Like those commercial "generator" powerpacks but cheaper and more powerful.
As an extreme example, imagine a big ammo can containing your cells, a BMS and a Sterling BB, with outside switches, ports / terminals and a voltmeter or BM gauge.
Like those commercial "generator" powerpacks but cheaper and more powerful.
DiploStrat
Expedition Leader
All of this. Very clever, especially for those who can build their own lithium cell/BMS combo.
I am asking about the nutz 'n bolts. Seems you could simply run a properly sized cable to the alternator and (as we have beaten into the ground, let the B2B handle that.)
-- How would you do solar panels which AFAIK, would be coming in at about 20v, or more, if in series.
-- What would you do for shore power?
Ah, I don't mean you don't still need the other device types. The output from sources needs to still be within the input requirements of your DCDC, just not necessarily matching exactly the needs of your shiny new LFP bank.
So if you already have the B2B, less need to replace existing / older lead-intended gear
with fancy adjustable-setpoint units.
For mains, can use even an old garage style charger
For solar, keep a simple $40 SC going with old low voltage panels.
Visit a location with wind or hydro can ask to plug in, so long as the input Vdc is in the ballpark.
Plug your LFP pack into a different vehicle, don't need a fancy alt/vr in each.
Also can deal with long wiring runs from source with too much voltage drop.
If like OP everything is set up for 24-24V
then another 12-24V B2B is needed if there are 12Vnom input sources to tap into.
As for nuts and bolts, the output from the source is connected to the input of the DCDC, your bank remains connected to its outputs.
The pack's B2B is the only charge source that touches the cells directly, the voltage setpoint precisely regulated, the current safely limited.
Of course safe for the pack, still need to ensure the source can handle drawing that amps level, or that it at least has decent current protection.
Sterlings' current limiting allow you to you cut the level by 50% if needed.
So if you already have the B2B, less need to replace existing / older lead-intended gear
with fancy adjustable-setpoint units.
For mains, can use even an old garage style charger
For solar, keep a simple $40 SC going with old low voltage panels.
Visit a location with wind or hydro can ask to plug in, so long as the input Vdc is in the ballpark.
Plug your LFP pack into a different vehicle, don't need a fancy alt/vr in each.
Also can deal with long wiring runs from source with too much voltage drop.
If like OP everything is set up for 24-24V
then another 12-24V B2B is needed if there are 12Vnom input sources to tap into.
As for nuts and bolts, the output from the source is connected to the input of the DCDC, your bank remains connected to its outputs.
The pack's B2B is the only charge source that touches the cells directly, the voltage setpoint precisely regulated, the current safely limited.
Of course safe for the pack, still need to ensure the source can handle drawing that amps level, or that it at least has decent current protection.
Sterlings' current limiting allow you to you cut the level by 50% if needed.
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