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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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M2Cw-  No experience with Cruzpro & haven't read manual

It seems to be going straight from soft start On to absorb (constant V, diminishing current), no bulk, probably as batteries are up there with already a surface charge.

I dont know any lead acid batteries that charge at 14V. So that parameter is weird. Discrepancies as noted at  by IT.Voltage peak ragged and varying?

As IT said (sense connection), or varying load? (-6A whilst motor off.)

My FLA Vset parameter is 14.7V

Never heard of 15min setting for absorb, can't be temp trip or would trip to float as soon as you rebooted.

Quick and dirty for mean time would be to put a on/off switch on the CruzPro power supply wire from ignition switch.

Switch off for ten seconds switch on to reboot CruzP. & reset for 15mins. If multiple repeats I wouldn't run < 2.5A tail current though and monitor if switched to "hot rated".

I presume your motor is switched off with ign via fuel solenoid, so reboot requires stop motor and restart.

Mine has kill cable, so just switching ign off kills external reg processor not the motor. Only difference is I reboot every hr.

 

As soon as Covid lets up I'm changing chemistries. Keeping the Bosch alts though. (Doubling up) 230A which I will derate.

Wakespeed is niice ...and expensive. $750US with harness , sensors, shunt, data cable.

 

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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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