sailboat charging system - battery question

[SayWhen]

I am a newly registered SBO user but have followed the forum here for years. I’ve been having some lurking questions as to whether my current house bank is behaving as it should. I thought I would ask what others experience has been. I've read many posts by Maine Sail and have poured through the pbase site in addition to posts here.
Here are the details:
1998 Tartan 4100 - new to me in Spring 2014
Two 8D west marine gel batteries (rated at 225 AH ea. New in fall 2009) plus a class 31 starter battery (new in 2014) for backup.
Alternator is a Balmar 90 series 100 amp alternator.
Balmar external regulator MC-614.
Balmar SmartGuage for detecting SOC
My daily amp usage comes in around 105 amps.
Typical sailing is 3+ days out prior to dockside power
1-2 weekly trips before shore power is available

Here is what I experience. During bulk loading (house bank only) when my battery SOC is ~65-70% I can test the alternator output with a clamp on amp meter. The amp current is ~40 amps. I test this both at the alternator and the bank itself. They’re both the same. So I know I’m not getting much voltage drop from the alt to the house bank. This is lower than I would expect and I would have thought the bulk loading would be pushing way more current that 40 amps. When the regulator steps into acceptance, the amp current drops to ~15-20 amps. I realize that you’re only going to charge to approx. 80% and will get a significant diminishing return beyond that point. Typically, I will see bulk charge for about 30 minutes then go to acceptance. So I always feel as though I’m never able to push back into the batteries what’s being used.

When I return and plug into shore power I have a 100 amp Freedom 2000 inverter/charger. When that charger turns on, it’s only pushing ~40 amps while in bulk also. So the good news is that I see the same amp current while on shore power as I do from my alternator. The bad news is I still think it should be pushing in more amperage.

Do you monitor anything similar on your batteries and charge mgmt. system? What is your experience? I’m trying to understand whether I have an issue with my batteries just being old or whether what I’m experiencing is in line when batteries are at this SOC.

I would greatly appreciate any feedback or further questions.

SayWhen

 

[TechAnnMarie]

A 100 amp "rating" alternator will only put out 100 amps when cold into a low voltage load, say 11 volts, at optimum RPM on a test bench. In the real world you would expect about 80 to 90 amps when it starts bulk charging and this will drop off rapidly as the battery voltage rises and alternator temperature increases.

Your 40 amp reading at that level of charge may not be unreasonable however if you think in used to do better, have the alternator checked to see if you have lost any rectifiers. Although modern rectifiers have superior ratings they can still be damaged by disconnecting the load while they are charging at high current (for example by turning the Perko switch to OFF if the charging line is going through it and assuming you don't have a field disconnect).

 

[Stu Jackson]

Battery acceptance limits alternator output to what the batteries will, uhm, accept based on their SOC.

 

[Ralph Johnstone]

Balmar external regulator MC-614.

What voltage is the regulator programmed for bulk charging ?

I I realize that you’re only going to charge to approx. 80% and will get a significant diminishing return beyond that point.

That is what happens with fixed voltage internal regulator. You should be getting 100% return with an external regulator providing the bulk and acceptance voltages are set correctly along with reasonable running hours.

 

[SayWhen]

Ralph,
Thanks for the feedback. The external regulator is set for the gel profile so the bulk voltage is 14.1 and the acceptance voltage is 13.9. Per Maine Sails posts I've got the positive sensing wire from the regulator directly connected to the house bank. My next step would be to also wire the ground from the external regulator directly to the ground on the house bank. I. should then have something like what's described here http://www.pbase.com/mainecruising/regulator_voltage_sensing


Say When

 

[Ralph Johnstone]

Ralph,
Thanks for the feedback. The external regulator is set for the gel profile so the bulk voltage is 14.1 and the acceptance voltage is 13.9. Per Maine Sails posts I've got the positive sensing wire from the regulator directly connected to the house bank. My next step would be to also wire the ground from the external regulator directly to the ground on the house bank. I. should then have something like what's described here http://www.pbase.com/mainecruising/regulator_voltage_sensing


Say When

Wiring sounds good. Same thing I did to ensure I had the ACTUAL battery voltage.

Two other thoughts are:

1. Is the input from the alternator being limited by the max. temp. limiter in the regulator ?

2. Is the the belt manager setting too low ?

 

[jlp0217]

" I can test the alternator output with a clamp on amp meter. The amp current is ~40 amps. I test this both at the alternator and the bank itself. They’re both the same. So I know I’m not getting much voltage drop from the alt to the house bank"

Current doesn't drop along the wire, voltage does. Check the voltage at both ends, not current. Check with the probes on the alternator and battery terminals to see if you have good clean connections. You can also measure voltage drop directly, with one probe on the Alt + and the other on the Bat + and same with -'s, 3% would be 0.42 volts (sum of measure of + and - drops). Remember you can only measure voltage drop when current is flowing.

 

[Maine Sail]

Need to know physical battery terminal voltage at 40A as well as back of the alt voltage at 40A. You can't use an amperage clamp to determine voltage drop, you'd use a volt meter for that..

Because GEL batteries charge at a lower voltage the duration for which they accept high current is shorter...

If battery voltage or alt voltage are not at 14.1V, when at 40A, check regulator settings such as small engine mode, temp sensor or belt manager..

Also keep in mind that when new you had 450Ah's and removing 105Ah's only leaves you at about 80% SOC +/- so it is likely your bulk charge duration is only a few minutes befor the batts come up to the "limiting voltage". Once the regulator begins limiting voltage accepted charge current goes down...

Ignore the Smart Guage SOC for a few days and discharge until you hit 11.7V at your normal house loads then turn on the alternator and you will probably see more current for a longer time....

 

[SayWhen]

Thanks for the feedback. In my post I've misstated the comment about voltage drop. What I mean to say is the batteries are seeing the same current off the alternator that I'm also measuring directly at the battery when there is no load. As for the suggestion on looking at the belt manager, at this time, there is not a sensor set up for the load, or the alternator or the battery temperature sensors. That's something I'll need to purchase and wire up.
I'm beginning to think that the Balmar SmartGuage may need to go through a few more weekends out on the water before it gets closer to the actual battery condition. At this time, it's only been a few weekends with that sensor in place. Also, I now have a better understanding that because the house bank is Gels, they're going to go from bulk to acceptance more quickly due to the voltage limit difference. Ultimately, the batteries only accepting 40 amps of current in bulk more likely is an indicator the batteries are at a higher overall SOC than the SmartGuage is currently reading.

 

[Stu Jackson]

1 As for the suggestion on looking at the belt manager, at this time, there is not a sensor set up for the load, or the alternator or the battery temperature sensors. That's something I'll need to purchase and wire up.

2 I'm beginning to think that the Balmar SmartGuage may need to go through a few more weekends out on the water before it gets closer to the actual battery condition. ............ Ultimately, the batteries only accepting 40 amps of current in bulk more likely is an indicator the batteries are at a higher overall SOC than the SmartGuage is currently reading.

1 Belt manager is a completely different feature than temp sensing. Belt manager can be done without temp sensing. Also consider Small Engine Mode (search for it on this forum, it's been discussed quite often).

2. Probably quite true.

Good luck.

 

[SayWhen]

1 Belt manager is a completely different feature than temp sensing. Belt manager can be done without temp sensing. Also consider Small Engine Mode (search for it on this forum, it's been discussed quite often).

2. Probably quite true.

Good luck.

Stu, while on the boat this weekend I do know that the setting for the belt manager is at b-0. This is the default that comes from Balmar and my interpretation is that it's disabled according to the manual.

Another sailor I spoke with offered the following suggestion: Some morning when I'm at an anchorage and the batteries are discharged to approx 70% SOC to perform the following. Start the engine and check the current flow to see if it's showing approx ~40 amps. Verify the external alternator is in bulk mode. Next, enable the built-in on-board inverter. Then, plug in a hair dryer and see if the current output increases. His opinion was the alternator should increase the current output to the batteries to compensate for the draw from the batteries resulting from the hair drier. This makes sense to me. What do others think? I guess if this were the case I would know the alternator is capable of outputting more current, however, my usage hasn't dictated more than the ~40 amps I've been seeing.

 

[Maine Sail]

Stu, while on the boat this weekend I do know that the setting for the belt manager is at b-0. This is the default that comes from Balmar and my interpretation is that it's disabled according to the manual.

Another sailor I spoke with offered the following suggestion: Some morning when I'm at an anchorage and the batteries are discharged to approx 70% SOC to perform the following. Start the engine and check the current flow to see if it's showing approx ~40 amps. Verify the external alternator is in bulk mode. Next, enable the built-in on-board inverter. Then, plug in a hair dryer and see if the current output increases. His opinion was the alternator should increase the current output to the batteries to compensate for the draw from the batteries resulting from the hair drier. This makes sense to me. What do others think? I guess if this were the case I would know the alternator is capable of outputting more current, however, my usage hasn't dictated more than the ~40 amps I've been seeing.

This is how any good professional would test the alternator output. I suspect the problem is that the alternator regulator is seeing 14.1V and is simply limiting the voltage. If you test across the regulator black wire and regulator volt sense/red and it is saying 14.1V then that is what's going on. It does not matter whether the alt reg is in bulk or float if you apply a load that is larger than alt capability, which drags battery voltage down, the regulator will automatically re-enter bulk.. No need to discharge your bank for this test just apply a 1500W load to the inverter and clamp the alternator positive output wire........

 

[SayWhen]

Just thought I would add a follow-up post that I was able to confirm the alternator was capable of outputting more than the 40 amps current I had seen in the past.
With the engine running, and all the electronics off, I enabled the onboard inverter and started the microwave. I was seeing current upwards of 65 amps from the alternator positive output. I believe the microwave is only 800 watts so that's about perfect.