diy solar

diy solar

Many here say that an alternator should not be connected to LiFePO4 and that one should use DC-DC Charger

I get 80A continuous from a single 12mm green stripe V belt. Probably get 90A
* align pulleys perfectly
* smooth pulleys
* EB <50°C

Regarding "Have to".
I also know of people with LiFePo4 and no bms, and temp controlled auto stock alternators that have been that way for 5yrs
and have no problems.
I'm more cautious and need a little more security.
 
I don't get this. Why do you rely on an alternator to charge lithium? Its so easy with solar. No moving parts. No burning fossil fuels. Lithium and solar were made for each other. Our 8x280Ah cells run the whole boat at anchor with just 720w of solar. We cook electric, make hot water on the immersion heater, make our water on the watermaker and run fridges and freezer.
We have a basic 60 amp alternator that will give us 17amps of charge to the lithium when the engine is running via Victron B2B. Its not our primary source of power as we are a sailing boat. The solar harvests about 4kw per day quietly, at anchor.
 
LiFePo4 and no bms, and temp controlled auto stock alternators
What stock alternator has temperature control? I dunno, maybe its more common these days... my buddy has a brand new sprinter that did not have a heat controlled alternator (it died from heat due to direct to LiFePO4 installation (not me!)) in a matter of days.

The whole point of using a B2B charger or any other means of controlling the charging is to control the heat.
 
I don't get this. Why do you rely on an alternator to charge lithium? Its so easy with solar. No moving parts. No burning fossil fuels. Lithium and solar were made for each other. Our 8x280Ah cells run the whole boat at anchor with just 720w of solar. We cook electric, make hot water on the immersion heater, make our water on the watermaker and run fridges and freezer.
We have a basic 60 amp alternator that will give us 17amps of charge to the lithium when the engine is running via Victron B2B. Its not our primary source of power as we are a sailing boat. The solar harvests about 4kw per day quietly, at anchor.
On my Ericson 27, there just isn’t much room for solar panels. I’ve got 120W on the dodger, and another 200W portable that I can unfold. The rest of the boat is primarily sailing hardware.

Plus, the dirty secret when it comes to sailing on my part of the world is that realistically, you’re probably motoring half the time anyway, especially if you want to drop the hook in time for Happy Hour. You might as well charge the batteries while putt putting along.
 
On my Ericson 27, there just isn’t much room for solar panels. I’ve got 120W on the dodger, and another 200W portable that I can unfold. The rest of the boat is primarily sailing hardware.

Plus, the dirty secret when it comes to sailing on my part of the world is that realistically, you’re probably motoring half the time anyway, especially if you want to drop the hook in time for Happy Hour. You might as well charge the batteries while putt putting along.
Have you thought about hanging some panels on the guardwires? They act as spray dodgers at sea and fold them up to horizontal to catch the sun or what ever angle the sun is atIMG_20220505_100128.jpg
 
Have you thought about hanging some panels on the guardwires? They act as spray dodgers at sea and fold them up to horizontal to catch the sun or what ever angle the sun is atView attachment 151117
I mean, we could, but I also admit to a bit of vanity and don't really want her to look like a floating power station. The reality is that we're probably motoring 4 to 5 hours a day when we're actively using her, so that's more than enough to keep the batteries topped up. When we're doing a longer stay the 320 watts combined solar, plus the large size of our battery bank, will get us through 3 or 4 days without any hassle.
 
I'll jump in on this thread vs opening a new one.
I am about to try the alt > lifepo4 charging route
I tried it before with a large AGM bank but cooked the alt so gave up on it until now

We are an ex trawler, big slow spinning motor, often doing 6+ hour runs
We never, ever go into marinas so never see shore power
And this has worked for us for 7 years now

We have 840ah @ 24v of lifepo4 in and running for 18mths
2500w of solar through a midnite classic 150mppt
24v Victron multiplus 5000/120 inverter charger
7kva diesel genset

We are in Australia so costs can get out of hand here which is why we have avoided this path thus far but, I have got onto a
* unused genuine Delco Remy 36si 105 amp @ 24v alt cheap enough to buy a 2nd as a spare
* Wakespeed ws500 from an Oz supplier for $500
Making it around $800 spend.

Looked at a Balmar alt but as our engine is a slow spinner it was pointed out that a $2300 140amp Balmar would only put out 60 amps at our cruise RPM whereas the 105 amp Delco has a much steeper curve -and should be able to get 80 amps doing our 1150rpm.
 
So, my choices will be:
Wakespeed vs DC - DC charger

My concern with the oft touted DC - DC charger is 2 x 35 amp (Sterling for $350 each) chargers pulling from the starts will still be loading up the alt enough to cook it.
 
If you can solder and arent relying on warranty coverage, installing an external rectifier should remove most of the heat generation from the alternator case. An alternator typically has a 3 phase stator which means it needs 6 diodes to get full-bridge rectification. Each diode drops something like half a volt, which multiplied by the current in amps will equal the watts in heat being generated in the back of the case (right next to the brushes, coincidentically). Giant 200a full bridge rectifiers are cheap, like $20 on amazon. Youd probably want to mount it to a large heat sink and put it in the airflow of your engine cooling fan, or mount its own fan to it. But the actual process of converting an alternator to external rectification is basically just soldering 3 large wires onto your stator leads and routing them out the rear of the case to the new rectifier location.

It may not be something i would do on a very expensive alternator because if im paying a lot of money for an alternator it would only be to buy the privilege of not HAVING to do anything to it myself in the first place!

There are also water cooled alternators in some cars which might be easy to reftrofit. For example, my old 2005 Porsche Cayenne has a water cooled alternator and it is a ‘self-exciting’ design that doesnt need ANYTHING hooked up to it to work. You just spin it and it powers up. Ive done it on the bench. Some V8 BMWs have them as well. My assumption is that it mostly has to do with the Autobahn, so German cars are where i would look for water cooled alternator donors. ?
 
I'll jump in on this thread vs opening a new one.
I am about to try the alt > lifepo4 charging route
I tried it before with a large AGM bank but cooked the alt so gave up on it until now

We are an ex trawler, big slow spinning motor, often doing 6+ hour runs
We never, ever go into marinas so never see shore power
And this has worked for us for 7 years now

We have 840ah @ 24v of lifepo4 in and running for 18mths
2500w of solar through a midnite classic 150mppt
24v Victron multiplus 5000/120 inverter charger
7kva diesel genset

We are in Australia so costs can get out of hand here which is why we have avoided this path thus far but, I have got onto a
* unused genuine Delco Remy 36si 105 amp @ 24v alt cheap enough to buy a 2nd as a spare
* Wakespeed ws500 from an Oz supplier for $500
Making it around $800 spend.

Looked at a Balmar alt but as our engine is a slow spinner it was pointed out that a $2300 140amp Balmar would only put out 60 amps at our cruise RPM whereas the 105 amp Delco has a much steeper curve -and should be able to get 80 amps doing our 1150rpm.
Where do you buy that alternator at that low price?
 
Where do you buy that alternator at that low price?
I bought a new 24v bus alternator, 155A @24v for £200. I will be adding Wakespeed reg. The reg will cost more than the alternator. Happy if I can run it at 75A at 24v
 
Where do you buy that alternator at that low price?
I got mine on Facebook marketplace
Commercial vessel took them off new engine and replaced with bigger units before boat was launched.
 
Decided to go the DC to DC chargers for a few reasons


1) Ben Sterling from Sterling UK got back to me within hours, talked me through it and assured me that a 36si @105 amps will run 70amps of chargers without cooking the alt - 70% load is what the target is and, in reality, what the wakespeed would deliver from the alt if saving it.

2) redundancy
if the Wakespeed craps out I have zero alt charge
It's unlikely I will have both Sterling chargers die

3) the Wakespeed dealer in Oz I was going to buy from still hasn't got back to me

4) the Wakespeed setup needed "extras" if wanting to charge and protect the start battery
All that made the Sterling's the more affordable choice
 
This seems to be a nice Diesel battery charger.

Hatz (German and very old well respected company) single cylinder with a Hatz designed and built 56v 100 amp *PMG* attached to the flywheel of the engine. J1939 CAN bus equipped from the factory.

There is a 24v version if thats your voltage with 2 differnt 24v units available - 24v @100 amps and they have a 24v version that has *TWO* inverters attached to the 3 phase output of the PMG to give 200 amps at 24v (1 x 100 amp + 1 x 100 amp attached to the one engine)

They also do a 115v unit and a 230v /13amp unit with the same PMG setup. That is, the one AC unit can do either 115v **OR** 230v by adjusting jumpers on the unit. From the data sheet............

***Voltage output (Factory Setting) Volt out nom.: 230/115 Volt AC. Selectable by mean of JMP1*** - Seems to be very versatile and something I have never seen or heard of before.

Choice of engines - the 1B30E which is 347cc and the bigger 1B50E which is 517cc. Diesel usage listed as 1.2L per hour at 3/4 load on the bigger 1B50E

Here......... https://www.auroragenerators.com/product-page/battery-charging-dc-generator a US based manufacturer uses the same Hatz 1B30E engine but uses a different approach to generating the 56vdc. I prefer the PMG method built by Hatz myself as there are no external parts or belts to maintain over time.

Note the diminutive size of the 56v 100amp PMG unit....

Dimensions (mm) - 357 x 440 x 480
net-weight (kg) - approx. 71
packing dimensions (mm) - 570 x 570 x 820
gross-weight (kg) - approx. 82

Seems like a nice solution.
 

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The amount that i want to repower one of my tiny tractors with one of those is.. A LARGE AND POWERFUL URGE.

Probably not as large as the price tag? I havent looked. But i LOVE that. ?
 
I too think it’s downright absurd that it’s so difficult to fast charge LiFePO4 from perfectly capable alternators.

I’ll offer a few ideas that have come to my mind to generate some more conversation:

1. I’ll call this approach, cheap and big
2. I call this one alternating alternators. This idea I’ll credit to my algorithms instructor for teaching me to think outside the box. This approach assumes that overloading the alternator is safe until it reaches a maximum temperature, at which point it only needs to cool down. Is this a safe assumption? That would be useful to know.
  • Add a second high output alternator to your engine so you have two alternators, a1 and a2
  • Create circuit c1 that charges the LiFePO4 and circuit c2 that charges the vehicle starter battery
  • Configure c1a1 and c2a2
  • Once a1 gets too hot, swap c1a2 and c2a1 using temperature sensors, relays, and either hardware or an arduino to control when the circuits get swapped. I’m not aware of a DPDT relay large enough for this application, so I think you’ll need 4 of the above 500amp relays to swap the circuits, but there may be a way to simplify the circuit I’m thinking of.
  • Note: If the alternator heats up too quickly, this will become a non-solution.
3. Let’s return to first principals for a second.

How does a battery charge anyway? It seems to me it would require a voltage to be applied that is greater than the battery’s internal, open circuit voltage - otherwise how could it charge if the net circuit voltage is 0v? After all, isn’t this the exact same thing as hooking up another 12v battery at an equal charge in parallel? No charge is transferred if the batteries are at equal voltage - they merely sit there maintaining their capacity. Therefore, I conclude by intuition that the battery charger by definition must apply voltage greater than the battery open circuit voltage.

From there, Ohms law seems to indicate the battery charges at a rate of (chargerVoltage - batteryVoltage) / (batteryInternalResistance). The issue with LiFePO4 is allegedly that its internal resistance is lower than lead acid and therefore it needs a charger to “walk” it up the charge curve maintaining a voltage lead on the battery such that the amps it consumes does not exceed acceptable levels. Lead acid allegedly doesn’t need this since it’s internal resistance is high enough to limit the charge current given a relatively high constant charge voltage of 14.4ish volts from the alternator.

Therefore, it seems to me that if we can “simulate” the correct internal resistance for LiFePO4, we can hook it to a constant 14.4v alternator charge voltage and expect it to charge at the amps we desire, at least momentarily. One academic paper I read measured its test 100Ah LiFePO4 battery at 0.0018 Ohms internal resistance. So given a 14.4v alternator current, we can charge a LiFePO4 at 10% capacity (12v) at a current of 100A if we simulate a battery internal resistance of R = V/I = (14.4v - 12v) / (100A) = 0.024 Ohms. As battery voltage rises to approach our alternator voltage, we need to decrease the simulated internal resistance to maintain the same 100A charge current. I’m guessing at about 70% - 80% we could stop simulating additional resistance and let the battery’s internal resistance take it to full charge.

So now the only question is how? How can we dynamically simulate with resistors the internal resistance of the battery such that the battery charges at 100A until full? Do they make variable 12v 100A resistors in the 0.024 Ohms - 0.0018 Ohms range? Did I just ask how you design a DCDC charge controller? Idk, I’ve reached the end of my expertise now. I’ll let others chime in. :)
 
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Therefore, it seems to me that if we can “simulate” the correct internal resistance for LiFePO4, we can hook it to a constant 14.4v alternator charge voltage and expect it to charge at the amps we desire, at least momentarily. One academic paper I read measured its test 100Ah LiFePO4 battery at 0.0018 Ohms internal resistance. So given a 14.4v alternator current, we can charge a LiFePO4 at 10% capacity (12v) at a current of 100A if we simulate a battery internal resistance of R = V/I = (14.4v - 12v) / (100A) = 0.024 Ohms. As battery voltage rises to approach our alternator voltage, we need to decrease the simulated internal resistance to maintain the same 100A charge current. I’m guessing at about 70% - 80% we could stop simulating additional resistance and let the battery’s internal resistance take it to full charge.

So now the only question is how? How can we dynamically simulate with resistors the internal resistance of the battery such that the battery charges at 100A until full?
I had for years a 200AH directly connected to my Alternator in Parallel with the lead starter battery.

Two things which made that work - I had the LFP in the back of the Van - with 25ft of wire going to it. Further I used the vehicle frame as return path. That introduced plenty of resistance, further wiring resistance has a inverse relationship to amps flowing - when the wire gets warm - it has more resistance - when the current drop - it cools down and the resistance goes down again.

I had a 180A alternator - installed breakers into the wire going the to LFP with 100A - which never tripped.
Next - as a smart alternator it dropped to 13.8V after the initial 15-20 minutes of driving. So no 14.4V even with higher load.

13.8V is pretty close the resting voltage of LFP with 13.6V so charging rate is reduced.

I actually was more annoyed that I hardly ever saw more then 60A flowing.
 
My previous post:

It has now all survived 9 years of full-time travels and still faultless.
No DC-DC charger involved.
 
My previous post:

It has now all survived 9 years of full-time travels and still faultless.
No DC-DC charger involved.
You’re using the Argo diode type isolator. They can have some voltage drop under higher loads which in turn decreases current, but that might not be a bad thing for YOUR setup. Perhaps this could be a contributing factor to the long service life. The perfect moderator? If it ain’t broke, don’t change a thing.
 
In response to ehahn’s post i do personally subscribe to the whole DC to AC to DC thing for cost, control, convenience.

In my RV i do let the lifepo4 charge directly from the alternator if they are at a low voltage, but the wiring is highly non optimized and i dont get anything crazy from it. On the other hand i can use my 5000w msw inverter to power 4x30a power supplies and get a faster charge rate while allowing the voltage at the input to the inverter to drop to say 11 something, because who cares.

Yes, more conversion losses but if im trying to charge batteries at the equivalent of only 1-2hp off the back of a ~7 liter v10, efficiency has already gone out the window imo.
 
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