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Alternator Controller behaviour


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I have been watching closely my alternator performance recently, and I'm seeing some behavior I can't work out.

I have no idea what the alternator is (its Bosch, but that's the only marking I could find)
Alternator Controller is a CruzPro SAR20 (http://www.cruzpro.com/sar20.html)
Batteries are AGM. New. 

Here is what I see

House set sitting about 12.75v,
Start the engine. SAR20 puts no load on the alt for 60 seconds, then slowly loads it up over about 30seconds.
Batteries start charging about 40a. 
After 15mins, the current drops to 3 or 4a

Stop the engine, restart it, 60 seconds later its back at 40a. 15 minutes later, same thing. 

As the batteries charge and the current drops off, (currently at 11a going into the batteries) this still drops right off to 4a ish every 15minutes. 

The SAR20 has a feature to select if you have a 'hot rated' alternator, which is meant to reduce the alternator load to 80% of maximum after 15 minutes. This feature is disabled by a jumper on the box (is currently disabled)

Its a bit tedious having to stop and start every 15minutes. (but it works)

Any thoughts on why?

 

image.png

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Ok, firstly the regulator regulates voltage, not amps.

With the batts at 12.75v, they are basically fully charged.

So, you start the motor. The starter draws several hundred amps (or more, how many watts is the starter?), for however many secs you crank it for.

Start the motor,  now what's important is Volts. Should be around 14.4 with alt going. At this given voltage, the batts "decide" how many amps they will accept, as the resistance of the cells increases as the charged state increases, dropping off the rate of charge (amps).

What is likely happening,  is the regulator has met its "full charge" parameters,  and dropped the voltage to float level. This is working as designed.

So, watch the voltage - is it 14.4 or so to start? Does it drop after your 15 mins? What was the charge rate (amps) just before the voltage drop? If its about 1% of capacity,  the system is working fine.

 

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Ok now I've actually looked a the graphs! Sorry. 

How big is the battery bank?

Looks like the bulk charge time limit is set to 15 mins. Too short, should be a couple of hours.

I've not read the manual for that reg, but most have a time, better ones also watch the tail current, and switch to float when charge rate drops to about 1% of capacity at bulk voltage.

Looks like a reg program problem. 

 

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Bank is 250ah. 

Manual is here. http://www.cruzpro.com/sr20mano.pdf

The settings you can change, Bank size, Alternator Size, 12/24v, Wet or Gel Type, Hot or Not Rated Alt

No adjustment for volatages or times :(

Think I need to find a smarter regulator, or build one.

Have you seen these? http://www.wakespeed.com/

Started as an open source arduino based regulator that was infinitely  configurable .

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The wakespeed looks pretty good. I'll investigate that further. 

Look on page 6 of your manual - the reg is cutting the alt to 80% after 15 mins to protect the alt.

However, you should download the PDS for your batts, the specific one for make and model. It will tell you what voltages to charge at. O.1v is important for peak efficiency and long life. 

I've not read the whole manual, doing it from a phone with that layout is a pita! Agms usually can do 14.7v bulk,  and about 13.6 float.  The batt type selection on this reg sets the voltages. Pick the closest one to your batts requirements.  

I doubt that your Bosh alt is hot rated. Most are not.  But bosch is not too bad, your call as to whether you set the hot rated jumper on. Will likely fix the issue, but may burn out the alternator.

Is the alt a v nept, twin v belt,  or serpentine? If a single belt likely less than 100 amp. I've run the 60 amp bosch units for years set at hot rated with no issues, but it is a risk....

 

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Thanks IT, the reg shouldn't be cutting the alt to 80% as It is currently set as hot rated (see first post)

No idea if it is hot rated either ,but it has always been set that way and hasn't died yet..

Alternator was a single V, I've recently changed it to twin V.

I've got the datasheet for the batterys and have set the solar + shore power charging systems to the spec - but yeah, now being let down by poor alternator control.

Here is todays efforts : You can def see the charge current drop off as the batteries SOC increases.

image.png

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A couple of things would concern me about that graph 

When the alt drops its output, it does not go to the same voltage each time. This could be a voltage drop in the voltage sense wires. Do they go directly to the batts (only via a fuse, not to a bus bar or another cable etc) ? Its essential that the voltage sense cables get the real batt voltage. They MUST go to the batts. The negative for the unit must also have basically no resistance.  An issue in either of these wires will cause malfunctioning. 

Seems to me max voltage a d float is too low. Change the batt settings to wet cell and try again 

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It looks OK to me. It depends on how smart the Reg is and knowing the Cruisepro fello, it is likely to be pretty smart. So there will be a set of "rules" that the controller will be following. Depending on the internals, these rules could be simply basic sense and commands i.e. when Voltage reaches X, do Y. Or there could be a very complex set of algorithms in play that alter the charge as the Battery loads changes as it accepts the charge.

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I agree with Wheels.  It looks okay to me as well.    The graph shows a steady decline in current and drops to a float voltage.  There are defiantly conditions where absorption can be omitted if all other parameters are met. 

But is is really hard to fault find something like this from such a high state of charge.   Try it from 60% SOC and lets see those graphs and make sure you unplug any solar/wind you have.

Another thing that is worth pointing out is that alternator charging is only really efficient for the Bulk stage of a batteries charge cycle,  use solar [or maybe wind] to top off lead acid batteries to 100%.  Well unless you are motoring anyway.  

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6 minutes ago, Winter said:

Lateral I like your idea of an on off switch on the regulator supply, might try that. 

The graph is from a Victron 712, cabled into a Victron Venus GX which uploads data to the cloud, graphs are then from the Victron VRM portal

See here https://vrm.victronenergy.com/installation/36577/advanced (not my boat)

 

Winter : I have the VRM portal as well (except I did it with a Rasp Pi) - its bloody brilliant isn't it?

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1 hour ago, bigal.nz said:

Winter : I have the VRM portal as well (except I did it with a Rasp Pi) - its bloody brilliant isn't it?

It is bloody brilliant, and Victrons willingness to open that up to rasp pi tinkerers is fantastic. the bmv 712 plus a rasp pi cant be beaten. 

puts Victron at the top of my list. their stuff is pretty good value!

 

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Two points among all the conversation. The 14.1V is a tad low. i would suggest 14.4V. All this will achieve is getting a tad more current going in. But 14.1V  is not a problem as such.
The slight differences in Voltages as it cuts in and out is probably an efficiency thing due to Heat. As the Charge load decreases, the ALT would cool somewhat and the heat can make a dramatic difference to it's efficiency. So as it gets a tad cooler each cycle, it is able to increase the output voltage a tad. The increase is not huge and I would not worry one little bit about it.

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On 5/04/2020 at 5:31 PM, wheels said:

Two points among all the conversation. The 14.1V is a tad low. i would suggest 14.4V. All this will achieve is getting a tad more current going in. But 14.1V  is not a problem as such.
The slight differences in Voltages as it cuts in and out is probably an efficiency thing due to Heat. As the Charge load decreases, the ALT would cool somewhat and the heat can make a dramatic difference to it's efficiency. So as it gets a tad cooler each cycle, it is able to increase the output voltage a tad. The increase is not huge and I would not worry one little bit about it.

I've been meaning to comment on this for a few days. Its not often Wheels and I disagree on technical stuff, but in this case the voltage  of 14.1 is not a minor issue IMO. 

That voltage, rather than 14.4 -14.7 (whatever the PDS says for your specific batteries) will make an enormous difference to the time taken to charge the batts, and, in fact, they may NEVER get to 100% if not within the manufactures recommended voltages.

So, before replacing the reg, check the voltage sense connections and cables for correct connection and cable or terminal issues causing voltage drop. 

If the voltage cannot be corrected, change the regulator for one that can. Regs are still cheaper than new batts. 

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No disagreement IT. I thought I had made the same point about the 14.1 should be 14.4. I went back and re read my post and see I did not make that very clear at all and in fact messed up the comment completely. And I can't even use the excuse of posting in the early hrs of the morning either. I see it was 5.30PM. So I stuffed up there.
I don't know enough about what the Batteries are and the finer details of the Reg to personally say go to 14.7, but most certainly 14.4. is the essential Voltage point for the reg to be set to. If you go above 14.4, monitor the bank for a few charge cycles to ensure they are not over cooking. Or as IT said, if you can possibly get that information from the Battery manufacturer.

Question, does the Reg have Temperature monitoring of the Batteries ?? Temperature is very important. The ambient temperature between Summer and Winter can make an enormous difference with the current output that the Reg will make the ALT produce. I used to use the Ambient Temp setting when I wanted to push a higher charge current into the Bank and the Charge Voltage rose, so as the charge time was reduced. But that also means you have to monitor the Bank to ensure they are not getting hot and to watch the ALT that it is not being pushed too hard.  Ambient Temp will also make a huge difference in what the batteries will accept. So having an actual sensor can be a big advantage so as the Reg follows the Banks temp/ charge curve
 

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9 hours ago, lateral said:

You relate this to efficiency as opposed balancing surface charge EMF's Wheels?

 

Surface charge is not a thing in this instance. As a Plate charges, it starts from the surface and the charge works it's way in toward the center of the plate material. Surface charge is when the internals of the plate have no charge (a couple of reasons can cause this) and only the surface has a charge. The Battery can be voltage tested with a good reading of a charged battery. But the Battery actually has no Current available. So with a load placed on it, the Voltage will simply drop away.

The Efficiency part I was referring to is the Efficiency of the ALT itself in relation to the temperature of the ALT. If it is really hot, the resistance of the copper windings change and the magnetic field becomes weaker, thus the ALT will never deliver the Current that it would normally be capable of. Those time intervals where the ALT is not producing a current would be a cooling period on for those Windings. If you also note the graph, the initial leading current peak is higher than the end of the charge period and that could well be the heat rising causing that ALT charge efficiency dropping slightly. As the cycles continue, the peaks are ever so slightly higher ( I think, without going back to check)
There are other mechanical causes that can do this as well, so my comment is not something to take as fact without knowing a lot more about the installation.

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Ideally a reg that is completely voltage adjustable, and has temp sensors for the alt AND the batts, and hopefully a ramp up period to save on belt wear. Plus a hot rated alt. That's the ideal, but as you have discovered, its not inexpensive to do.

I had this on my old motor, although only with a 75amp balmar alt.

On the new D240, it comes with a 115 amp alt with temp sensing - it reduces output if to hot. However its a stupid reg, set voltage, although it has voltage sensing to allow for diodes etc.  I have added one of these http://nordkyndesign.com/product/nordkyn-electronics-vrc-200-charge-reference-controller/ it uses the standard alt voltage sense wire to control the alt, and makes it fully adjustable.

It keeps the temp sense for the alt as standard and has a battery temp sense option. Works great for anyone with a D2 series volvo...

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ok update for the thread. got in touch with mr man that made these units and he gave me some advice on how to adjust them for a higher voltage. now set at 14.5v @20deg c, will try this for a few days and see how I go. 

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7 hours ago, lateral said:

 

Zener diode in lead is a couple of bucks.

 

That's a clever idea as long as your not expecting great accuracy from a simple circuit.  You could do it with a normal diode as well and no need to have a bias current?  More parts though.

Don't forget to check max operating temp of the diode your using as well.  Most are 150 degree-ish rated or less.

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