Alternator Size with LiFePo4

[bobatkins]

Originally Posted by newhaul

Why try to reinvent the wheel.
http://www.cruisersforum.com/forums/...tor-78787.html

I've already investigated them. There is almost no way to mount those alternators to a Yanmar engine. The cases are not designed for the typical saddle mount with top tensioning bar.

[evm1024]

Just a side note, I use one of the hand-held optical tachs to measure the crankshaft RPM and the alternator RPM. This gives me the actual ratio of the pulleys.

Just st the engine to 1000 RPM and then measure the alternator RPM.

Works for transmission reduction ratios as well.

[rgleason]

Bobatkins wrote:

Charging LiFePo4 batteries would likely kill my alternator without a water cooling jacket as they would draw everything it could put out for hours.

I always thought you would program the alternator regulator to reduce the top end load. Maybe starting out at 50% of the alternator capacity and run it into a fairly discharged lifepi starting at say 20% SoC and watch everything like a hawk, infra red temps, voltage, amps, belt, batts, amps in, waterpump and engine, running it for an hour. Then move top load up 5 or 10% if everything looked ok.

Thanks for the detailed response, very helpful. I hope you'll post pics of your water / heat pipe exchanger when you finish. I am very interested.

Some of these on line cnc 3d printing shops create stuff in alu. If you want some drawings for that purpose I could do some for you and export to dwg. No cnc path definition though. That would be the print service.

[john61ct]

Yes, why the derating VR is essential.

In colder weather can bring output up

[newhaul]

Originally Posted by bobatkins

I've already investigated them. There is almost no way to mount those alternators to a Yanmar engine. The cases are not designed for the typical saddle mount with top tensioning bar.

sometimes when you want/ need something specific you just make the appropriate parts to geter done.( make the mounts that will allow you to use the larger water cooled alternator)

[jram]

I've read this thread with interest and, with one season's experience with my 540Ah of LiFePO4, I thought I'd share my experience.

My installation is a practical one. Alternators are expensive and an 'investment' - at least for me. I have Volvo D2-40s in my catamaran with the 115A 'dumb' alternators that have been the subject of much discussion on other threads. (For dumb - read fixed, internal regulation).

I was concerned by the theory put forward in other threads that these alternators would self-destruct after a while due to prolonged running at high output current so I instrumented them with temperature sensors and monitored their performance. In short, the stator cooling fins never reached more than 100C (212F) when I pushed them as hard as possible (empty batteries, high RPM). More normally, at cruising RPM, they were 80-90C. I considered this to be OK, compared with the design spec for automotive alternator performance. (A document that has been referenced in other threads.) The output was typically 90-100A, falling to 80-85A after a while. (One engine). With 2 engines, I can see up to 150A but I generally have no reason to run both engines at once (at cruising rpm anyway)..

My alternators are linked to my batteries (LiFePO4 - house and LA for start) through a no-drop charge splitter (Mastervolt - rated to 130A). This may be the reason for the lower than expected output currents. However, I consider these charge currents sufficiently low that the alternators are running 'derated'. So, for steady-state charging, the output currents and temperatures are (in my view) perfectly acceptable.

When the bank is 'fully charged' (13.8V is the limit I work to) the alternators are disconnected. I throttle back for a few seconds as a courtesy to the diodes (still connected to the LA batteries anyway) and disconnect the charge bus from the LiFePO4 bank. If I forget, my BMS will complain at me till I do disconnect them or if I'm really persistent, it will do it for me. (DIY BMS).

I understand that others will want to take advantage of the high charge acceptance rate of the LiFePO4 banks and I will, in the future do so as well. However, I'm not prepared to replace 2 perfectly good alternators that have life in them just to save a few minutes charging time.

My view on using the engines is that I only use them when I have to. My main charging is from solar. I'm happy to take the 'reduced' charge rate from the alternators (still much improved over LA) since its not my primary charging source. Moreover, I still have to remind myself that these batteries are happy NOT to be fully charged all the time and so we are content to float around in the middle somewhere just accepting what charge comes our way from solar or wind. If we need to motor, I decide whether to take some charge (or not). On a sunny day, I'm happy to motor without taking charge from the alternators (to the house bank) - it saves fuel.

(I note the interest in MOSFET switched rectification. I have a board for my wind generator sitting on my desk. Its one of my winter projects. I also have a board for an ideal diode to allow the charge bus to provide currents to the house loads while the House bank is disconnected from the charge bus but I'm not going to hijack this thread.)

Its an interesting topic - I'll be interested to see the final choices and reasons for them.

[bobatkins]

Originally Posted by rgleason

Bobatkins Do you mean 350 cfm for the fan? Looks like a good alternator. How wide is the saddle 3.15". Does it look like if you were to mount the recitifier remotely that you would get better cooling?
Which model denso so I can look it up?
Your space is tight too, but you don't seem to have a heat exchanger right behind. I am going to try to find a dimensioned drawing

This is very good baseline information. Does the denso have two internal fans? It looks like it.
Were you thinking of a D shaped transfer channel wrapped around the black center of the alternator? or perhaps something welded? What material? I suppose you could wrap multiple copper tubes around that area. What would you use to ensure good heat transfer? Would copper be ok considering the heat involved?
Using the cooler side of system water would be best.

The fan is a 12V 42CFM squirrel cage blower which may sound small until you realize that it circulates the air within the engine compartment about 6 times per minute. Compared to no air circulation (which is the typical engine compartment) the additional circulation helped to cool the alternator rectifier down to <225F which eliminated the need to engineer a remote rectifier solution. It also did keep the stator from getting hotter than 425F (I said 450F in my earlier post but when I checked my data it was actually 425F maximum)

This is the blower that I purchased:
https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

UTUO Brushless Radial Blower Dual Ball Bearing High Speed 12V DC Centrifugal Fan with XH-2.5 Plug 120mm by 120mm by 32mm (4.72x4.72x1.26 inch)

42CFM @2800RMP (max.) 61dB-A
12V DC Voltage,0.95A Current
2-pin XH-2.5 Fan Connector with 20cm+/-0.5 (8 inches) Cable
120x120x32mm,Weight only 202g/pcs
2 pcs Ball bearings With Long Fan Life Expectancy

Yes, the saddle is 3.5" - typical of a Chrysler 7509 alternator saddle. I use a spacer to take up the gap on the backside of the smaller Yanmar 2" saddle mount. I also use a spacer between the adjuster bar and the top mount of the alternator that you can see in the pictures. Otherwise mounting was very straightforward and belt alignment wasn't a problem.

Yes, the alternator has two internal fans they are stock. The forward fan draws in from the front and exhausts just forward for the stator coils and the rear fan draws in from the back through the diode pack and exhausts just behind the stator coils.

I have no idea what the base Denso part number is. The unit I purchased was from Nations Starter and their website doesn't list the alternator I purchased for some unknown reason but here is the part number:

7509-MF-200
Billet 200 Amp Denso High Amp Alternator
converted to external voltage regulator

I believe that Nation's made the billet cases for the alternator that I purchased from them.

I was thinking of a sorta fat/stumpy 'T' cross section where the wide stump of the T would go into the valley between the cases and contact the stator and the top part would overlap the existing cases slightly. Space has to be provided for the case through bolts and I need to figure out possible locations for the inlet and outlet fittings so that they don't interfere with anything on the engine after the alternator is in place.

Running raw water for cooling would just be ill advised - galvanic corrosion would be a real problem. The engine coolant loop run at about 180F and would be more than sufficient delta-T to suck away the stator heat.

[bobatkins]

Originally Posted by rgleason

Bobatkins wrote:

Charging LiFePo4 batteries would likely kill my alternator without a water cooling jacket as they would draw everything it could put out for hours.

I always thought you would program the alternator regulator to reduce the top end load. Maybe starting out at 50% of the alternator capacity and run it into a fairly discharged lifepi starting at say 20% SoC and watch everything like a hawk, infra red temps, voltage, amps, belt, batts, amps in, waterpump and engine, running it for an hour. Then move top load up 5 or 10% if everything looked ok.

Thanks for the detailed response, very helpful. I hope you'll post pics of your water / heat pipe exchanger when you finish. I am very interested.

Some of these on line cnc 3d printing shops create stuff in alu. If you want some drawings for that purpose I could do some for you and export to dwg. No cnc path definition though. That would be the print service.

Thank you for the offer. I do work with a CAD/CAM guy here who can go all the way to final 3D print files. I need to get a sample alternator to him so that we can dimension everything out. Trouble is he moved about 50 miles away from me so the logistics of getting with him is slowing things down.

I always find it interesting that everyone wants to purchase a high output alternator and then use a regulator to derate it to the point where it doesn't self-destruct. For small case alternators that is usually around 70-80A maximum. I say, rather then buy an expensive, high output alternator and then program a regulator to de-rate it to 70A - just buy an 80A alternator and be done with it.

I would like to figure out how to get maximum continuous power from a high output alternator as that would mean far less engine runtime to charge batteries which in itself would save fuel and wear on the engine.

[bobatkins]

Originally Posted by newhaul

sometimes when you want/ need something specific you just make the appropriate parts to geter done.( make the mounts that will allow you to use the larger water cooled alternator)

If you thought engineering a cooling jacket was difficult - engineering a way to mount the existing water cooled Bosch alternators onto a Yanmar engine is next to impossible however, if you figure it out I would be happy to buy a kit from you.

[newhaul]

Originally Posted by bobatkins

If you thought engineering a cooling jacket was difficult - engineering a way to mount the existing water cooled Bosch alternators onto a Yanmar engine is next to impossible however, if you figure it out I would be happy to buy a kit from you.

send me photos and specs of the mounts for the engine and the alternator .
I will design it for you or one of your friends to build.
( if you patent it give me design credit and a 10% royalty.)
pm the specs .

[rgleason]

Jram, thankyou for your good report. Your experience with the alternators is encouraginf.

[bobatkins]

Several people were interested in seeing pictures of the squirrel cage blower that I installed to cool the alternator on my Hunter 41.

The fan is a 12V 42CFM squirrel cage blower which may sound small until you realize that it circulates the air within the engine compartment about 6 times per minute. Compared to no air circulation (which is the typical engine compartment) the additional circulation helped to cool the alternator rectifier down to <225F which eliminated the need to engineer a remote rectifier solution. It also did keep the stator from getting hotter than 425F (I said 450F in my earlier post but when I checked my data it was actually 425F maximum). You may notice a round air duct fitting on the back cover of the alternator. I did that because I initially was planning to run a scat tube air duct between the blower and the alternator to force air into the back case but I found that it restricted the airflow way too much so I didn't hook up the scat tube between the blower and the alternator. Instead the blower bathes the entire alternator in significant airflow that helps radiate the heat away from the alternator case and cool the stator somewhat but not enough for full power operation for extended (>20 minutes) periods of time.

This is the blower that I purchased:
https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

UTUO Brushless Radial Blower Dual Ball Bearing High Speed 12V DC Centrifugal Fan with XH-2.5 Plug 120mm by 120mm by 32mm (4.72x4.72x1.26 inch)

42CFM @2800RMP (max.) 61dB-A
12V DC Voltage,0.95A Current
2-pin XH-2.5 Fan Connector with 20cm+/-0.5 (8 inches) Cable
120x120x32mm,Weight only 202g/pcs
2 pcs Ball bearings With Long Fan Life Expectancy

[deluxe68]

Originally Posted by bobatkins

Thank you for the offer. I do work with a CAD/CAM guy here who can go all the way to final 3D print files. I need to get a sample alternator to him so that we can dimension everything out. Trouble is he moved about 50 miles away from me so the logistics of getting with him is slowing things down.

I always find it interesting that everyone wants to purchase a high output alternator and then use a regulator to derate it to the point where it doesn't self-destruct. For small case alternators that is usually around 70-80A maximum. I say, rather then buy an expensive, high output alternator and then program a regulator to de-rate it to 70A - just buy an 80A alternator and be done with it.

I would like to figure out how to get maximum continuous power from a high output alternator as that would mean far less engine runtime to charge batteries which in itself would save fuel and wear on the engine.

You are assuming that people know beforehand that their small frame alternator must be derated by a huge percentage. In my case I started with a stock 80A alternator on a Yanmar that was only putting out about 50 amps. I took my yard managers recommendation and went with the Balmar 165. It is derated about 20% and still overheats at any output over 120A. If I would have done more research I would have known better and gone with a different brand. Hindsight is great, but all I can do now is try to cool the alternator or relocate the diodes.

[john61ct]

Far better for longevity, if you can't fit a large-frame unit designed to put out near-max rated amps all day,

to install an alt max-rated for double the output you actually need, and

then de-rate it to match your setup's temperature regime.

may well be possible to increase output in colder locations / seasons.

[OceanPlanet]

FWIW, we're getting near max rated, continuous output from the MGDC small case units, IF used with the MGDC remote rectifier, and run at adequate rpm (upgraded pulley kit)...