Lifeline (or others) charging times

[avanti]

Originally Posted by booster

I assume that the temperature throttling would be coming from the Balmar, and not the internal of the alternator? I wonder if the internal temp reductions that are built into the alternator are disabled when you use an external regulator like the Balmar. If so, there might be a totally different charge pattern if running of the internal alternator stuff.

Did you happen to notice what the battery temps were during the high rate charging? I would think that at some point, that may get to be the maximum charge rate determining factor. I don't recall if you have the Balmar sensing battery temp or not.

I think I need to run ours down to 20% SOC and go for a ride on a hot day to see what we get with no Balmar, running off the internal regulator in the 250 amp alternator. If we watch the battery temps, it should get pretty obvious if we could charge faster, or not, or if we need to be concerned about battery temps.

Yes, the Balmer (I assume) is responsible for the throttling. I am actually unaware of any active control inside the alternator, other than an intrinsic drop in efficiency at high temperature. I could be wrong, though. In any event, there is nothing to "deactivate", as far as I can see.

Yes, we do have both the alternator and the battery temp sensors, so there is some ambiguity about what was causing the effect (although judging from the relative fast cycling, I think it is more likely the alternator). Sorry, I have no temperature data other than the fact that the weather was in the 90s that day.

[Davydd]

The Balmar has the temperature sensor. I actually know something. If you can see them, you can read the codes on the Balmar as to what is going on. My Balmar is mounted upside down under the dash so I had to video the sequence and then flip the video to read it. It was too cryptic otherwise. What I know is a Balmar temperature sensor can fail and you'll get no charge as it will shut things down.

[booster]

Avanti's excellent information with his charging curve got us inspired to see what we really will have happening in a full discharge situation. It wasn't truly a worst case, as it wasn't horribly hot (70's-80's), but it was starting right out from 20% SOC. System is 440ah of 6v Lifelines, 3/0 cable from engine to rear, 250 amp DC Power alternator with internal Denso style regulator. We use only one alternator, so it also is running the engine. No Balmar or other addon regulator, but we can see amps and volts from the cockpit, and can easily get battery temp from the Magnum by going to look at it.

When first connected after a little bit of warmup, we got 181 amps at 12.7v to the coach, at idle speed of 677rpm, which is somewhat a fast idle.

We started driving and at 55mph got 210 amps at 13.2v which then dropped to 199 amps at 13.2v after 3 minutes.

Within the first 10 minutes, the amps fell to 193 and the voltage climbed to 13.3v, so it appears that the batteries were already starting to regulate the amperage with voltage increase.

We had a stoplight at 13 minutes so we got to see hot idle output, which was very interesting. It came in at 140 amps at 13.0 volts, running at 645rpm. This is odd because hot idle for our Chevy is 545rpm, and it was very stable at 645rpm. The only thing I can think of is that there is a wire to the alternator that feeds the field current percent back to the engine computer, even thought he computer does not control the alternator. It must increase the idle speed if it sees a large field current, and thus output, kind of like it would when you turn on the air conditioner. This is actually a bonus for us, I think.

In about one hour and 45 minutes, we were at 50% state of charge, and had returned 132ah of capacity to the batteries. We were charging at 167 amps and 13.7 volts. Battery temp had climbed from the starting 77* do 91*.

At about 2 hours things got kind of weird, as the amperage started to repeatedly jump down about 20 amps and immediately return to where it was. We first saw it when we were at 160 maps and 13.7v, and it would drop to 140 amps. It would do it every few minutes. It continued to do this type of drop for entire rest of the test, although the drop got lower as the charge amps got lower, with the last test point at 83/93 amps at 14.1 volts.

We stopped and did some shopping and then headed back on the same route and let the test continue, but not taking a bunch of points. After a hour and 45 minutes, we were at about 18 amps and 14.5v, so I turned off the alternator and turned on the solar to control better. We were getting 10-14 amps at 13.8v off the solar. Idle was back to stock 545 at this point. Battery temp was up to 104*.

We let the solar run for 3 hours when we got home and wound up at +20ah on the counter. To be totally full, we would need to see a bit over +35ah to cover charge efficiency, so not all that bad. Battery temp dropped about 8* in the first 15 minutes after stopping driving, so the heat from driving must be about that much. It then leveled off and stayed at 96* for a couple hours.

I am now going to move it in and run a cycle off the Magnum, which will take to to totally full by amps, so it will be interesting to see how long that takes, and how many amp hours we will really need to recover the 80% of capacity. That will determine if a drive, some solar, and overnight on shore power get us all the way to the totally full condition in the real world.

[booster]

I just got back from the shop, and was surprised to find that the Magnum charge cycle had finished in just about 3 hours.

In rough numbers, what we got for charging from 80% down, to fully charged at .5%C amps (Lifeline spec) is:

4 hours of driving (amps at end about 15-1 +

3 hours of solar at 4-12 amps from 2:30 to 5:30 (amps at end about 4-4.2) +

3 hours of shore charging in absorption. (amps at end 1.9)

The total time of 10 hours is substantially less than I thought it would be by at least 5 hours. The time shortening seems to have come at the end of the charging when comparing to charging that same amount of % SOC on the shore charger. I have to think that the very high rate early charging does something to make the last 25% SOC charging go faster. Lifeline has been trending toward higher and higher charge recommended charge rates for deep discharges, and this may be an indicator as to why.

This also shows that on the times when we are going to a place with shore power to do our periodic totally full charge (every 5-7 charge cycles), we shouldn't have any problem with not having enough time overnight to get totally full. The amps were down under 100 amps after only two hours of driving, so the 100 amp shore charger could take over there, even without any solar or more driving. If it works out the same, the shore charger would need to cover the 2 hours of less driving, 3 hours of solar, and 3 hours of shore charger, in our test. That is only 8 hours, so even pulling into a site late would give plenty of time.

If we weren't going for an electric site, we would need 4 hours of driving and 6+ hours of good solar to get full, so that would be tougher. It would probably take a 6:00am start and then solar from 10:00 to 5:00 to get there. Possible, but not as easy, but even if you didn't get totally full, you would probably be at 98% capacity.

For us, this is very encouraging, and should easily cover how we would be using the system in real camping. I would guess the we would hardly ever be at 80% down, with even 50% down being on the deeper end of usual.

[booster]

The other thing that comes of our test is how different the charging profile was compared to Avanti's. As far as I know, there are very few differences in our systems. The Balmar on Avanti's is probably the biggest difference, battery brand is different but both AGM, and the pulley ratios are likely a bit different. We have only one alternator.

We did not see the large reductions in output in the early charging stages that Avanti did, and it would have to be assumed that the Balmar was doing that based on the alternator temperature (I don't think it could be battery temp because the batteries could never cool in that short a time). We saw an initial drop of about 20 amps, which is similar to what Avanti indicated he got (but it didn't show on the graph), but then we leveled off there for over 30 minutes, while Avanti had the reductions on/off starting. We didn't start to taper off until the voltage came up a bit and we had recovered about 100ah. We then had a uniform taper of amps as the voltage went up.

We had always heard that the alternators have a stepped output reduction based on temperature, but we did not see that at all, so we either didn't get that hot, or it is not there. I took the temp of the alternator when we stopped after two hours and it was at 185*, which is about the same as the rest of the engine. By then we were under 100 amps charging, so it may have cooled some, though.

The very short duration drops in output we saw, of 10-20 amps, seemed pretty weird, but I have seen similar even when the batteries were not very low, in the past. DC Power has told me that the Denso regulator is a kind of smart charger profile, but had no details of how it did it. My guess would be is that they do a quick drop of amps to see what happens to the voltage. If the voltage drops quickly, it knows that there is either a big load on the system or that the batteries are not full. If the voltage holds, it would indicate that the batteries are getting full enough to cover whatever load is running for a short time. If it thinks they are getting near full, they would reduce amps, if they don't think so they would go back up where they were. We saw it do both of these examples in our test run.

After watching the battery temps, I don't think we would want to charge much faster than we did. We saw a battery temp increase of 29* total from start to finish. We saw an ambient change of about 15* over the time period of the test. By checking the battery temp just before we stopped, and then after sitting for a while, we could get a feel for how much of the temp was coming from the driving itself heating the battery post mounted sensors. Best guess on the amount from driving is 8-10* which is about how much they drop in under 15 minutes, and after that barely drop 1* per 2 hours as the batteries have very large heat capacity. With no temp correction in voltage available, with the temps we saw, we were right at the high end of the recommended charge voltage for the Lifelines (if you subtract the driving temp rise, which isn't really what the batteries are at). I ordered an aquarium digital thermometer, wired, that I am going to try to locate on the battery case to see how it tracks with the post mount sensors. I should be able to mount the readout, which also has min/max, on the dash so we can see it while driving.