Originally Posted by waltdownunder
that enables everyone to run a small/midsized Lithium
bank and charge it savely with your standard alternator
2nd you can easly adapter current
draw, so you always have the ability to safely max out of your alternator
. An alternator has 50% efficeny means it creates 50% heat. So when you create 50Ax12V=1200W then the Alternator creates 1200W heat which can kills your coils if running on low RPM
With this unit if you are running on idle 1000RPM you can limit your standard 80A alternator to 25A and be safe, if you are motoring with 2000RPM you can turn it up to 40A or 50A (on a high quality one) and be safe too as the alternator can cool itself better.
Process to find your current
Just get a cheap
infrared thermometer for 10$ on aliexpress/ebay/amazon, run your alternator on different RPMs with rising current and you can easily find out how much amps your alternator can deliver at which RPM
plus an overall amp limit where the alternator runs safely in all RPM ranges.
Your limit point is when the alternator temp starts not steady after running it for 2min and start to rise or above/close to the temp your isolation lacqur on the alternators coils start to melt. Eg Bosch or Delco have that data and will give it to you on request.
If they don't give you this data, crank your engine
to 2800 RPM go to 60% of the rated alternators current and after 3min runtime measure the temp that is created, then lower the RPM to 2300 and measure the temp after 30 sek. runtime and then crank it immediatly up to 2800RPM again to cool it for min. 2 minutes. this 30sek time measurement is the safe max. temp point of your coils. If between that safe point and the previous measure at 2800RPM is less then 15 degrees celsius, then do the same procedure with 70% of the rated current again...your lucky and have a very good quality alternator.
Now you know your temp limit, go from idle to max. RPM in 100RPM steps and crank up the limiter till the current draw creats a steady temp 10 degrees celcius below the limit. Note all that down and you can maximise the output with given RPMs. The resulting current at idle is your overall save current draw limit and standard limit adjustment. I suggest to limit always to the current limit 300RPMs lower => when you adjust throttle the alternator never gets damaged. More RPMs never hurt, only lower.
And exactly what I was looking for my 24V big lithum bank project
and the only thing that made me a headache till now=> a big balmore alternator with current limiter and temperature control cost a fortune and if breaks in remote
area a lot special parts
you cannot get.
With this unit I buy a cheap
used big truck alternator 24V, overhaul
it, do the procedure above of and it will run relaible/safe.
And a 2nd one as spare for in total for 1/3 the price
of a balmore.
And if they break they can be repaired as super simple with everywhere avaliable parts
. I just order 4 piece of each part I need to order for overhauling it, so I have 2 sets of spare parts if it breaks to repair
To make the truck alternator fit adapt the ratio via the pulley of the alternator. That can be done by calculating it, so its RPM fit to the boat
engines RPM. Original setup should be fare off as a truck engine
is running on low rpms too. Then let a machine shop create a mounting adapter+according size pulley and ready to go.
A car alternator is insufficent, doesn't work
or made to work
properly. But truck works, lot boats have truck alternators as some boat
engines are marinzed truck engines