Travato LiFePO4 Battery Install

[booster]

Time to pick 8.33 hours like the do on The Price is Right.

[wincrasher]

I'm afraid it didn't make it that long. At 4 hours, I was at 12.1 volts and the generator started. From the chart on Smart Battery's site, that should be essentially empty, but I have no real way of telling. Interestingly, the gauge on my Onan remote was reading 12.1 volts, but the gauge I have in the cabin was reading 11.8. I think I can attribute that to the 12v pickup on the generator is a straight line to the battery, whereas the 12v outlet in the cabin has the block and fuse panel and wiring between it.

Anyways, I have some observations on charging. Firstly, the charger is running flat out - both fans spinning. Even though the spec is the same as my old charger (725 watts/45 amp) it must be putting out more of that because I popped my GFCI in the garage (running on a 15 amp drop cord). Could just be a coincidence, but the only time it's done that was with the AC and other things running and a long drop cord.

Secondly, the voltage showing on the gauge is not the same as I was seeing at the shop. When I first installed the battery, it was reading 14.5 volts. I now suspect that the battery was delivered fully charged and not the 30-40% charge I was led to believe. Now, with the depleted battery, the voltage in the cabin started at 13.2 and is rising. After 2 hours it's bouncing 13.8 to 14.0. So instead of the constant 14.5 this charger claims to put out, it either ramps up until it peaks when the battery is full, or it's just the method of how we are measuring the voltage, I don't know.

As I said before, I started this test with a hot refrigerator - above 80 degrees inside (it's quite hot here). So I suspect that it was needing 15 or more amps trying to cool down. It did get close to desired temps inside in the 4 hours, which was better than I was expecting.
My fans, lights, tv's etc, must be using 4 or 5 amps. 1 light in the bathroom is incandescent, so it's probably 1 amp by itself. Same for the 2 fans. The TV and stereo are negligible. The CO detector is probably 1 amp. I have no idea on the LP system - the manual says to engage the cutoff switch when not in use to avoid draining the battery, so it must have some parasitic load.

I've been on the charger for almost 3 hours. I really expected to be fully charged by now, but I guess not. I'll report back when the voltage is back at 14.5. I don't think it needs to sit for any length of time when it reaches that point.

One last thing, even though the current voltage is reading 14.0 volts with the charger running, if you shut it off, the voltage reads 13.4 volts, which would indicate a full battery. But you have no way of knowing if it's truly full. Good thing with lithium is that it doesn't really matter - it is just fine to be partially charged.

[markopolo]

Deleted.

I used the chart from here: 12V 100 AH Lithium Ion Battery | Deep Cycle Lithium Ion Battery | Smart Battery

As Wincrasher points out below - it's not right.

This chart looks better: 12V 100AH Lithium Ion Battery | Chargers and Voltmeters | Smart Battery - Products

[wincrasher]

That is curious. Maybe 12.1 is not nearly empty for one.

I'm pretty sure it was full - I had charged it overnite, then I disconnected the shore power and shut off the internal disconnect switch until today. It sat for 2 weeks in my shop. Then I got the van out of my shop, engaged the switch, and drove the van into town to get the LP filled. I drove about 20 mins, then sat for 20 mins, then 20 mins home. So the alternator should have kept it topped off, I'd think.

But I don't understand that table. How can you more than double the load, but still have the same run time?

[markopolo]

That chart doesn't make sense .............. ignore my last post

Here's a better one:

better chart.JPG

[markopolo]

It's starting to make more sense to me.

Maybe 100ah used in 4 hours. So 3hrs on the 45 amp charger to recharge seems OK to me.

[wincrasher]

That makes more sense. Could be that I can go alittle lower on voltage. The BMS will protect it from going too low. I'm also pretty sure that the charger is not putting out the full 45 amps, nor should I probably expect it too. I may re-run this test and see how she does with alternator charging. I'd expect it to be a good bit quicker.

[wincrasher]

OK, at 3.5 hours, the voltage is reading 14.5 volts. The charger is cool and the fans not blowing. So now I'm pretty sure that the battery is now full. But also, it doesn't appear it is putting anything into the battery, and could probably be just left online.

It just strikes me that it shouldn't work this way. But the charger may be putting out a constant voltage to the battery, but the 12v system in the coach is not reading it that way.

[markopolo]

Re: your earlier post - I think the GFCI tripping was coincidence. 725 watt charger on a 1800 watt circuit is fine.

Re: charger voltage
Booster's explanation of charging here: http://www.classbforum.com/forums/f5...html#post29459

makes it easier to understand charging. He was talking about the alternator but it applies to the charger as well.

Ohms Law
Voltage = I (current in Amps) x R (resistance in Ohms)

This page is a good read: How Three Stage Battery Charging Works | All About Lead Acid Batteries

You can ignore the references to lead acid batteries.

Two quotes from the site:

if we want to maintain a constant current in a circuit with rising resistance, we must raise the voltage.

and

If voltage is held constant and resistance increases, current must decrease.

My take on it is that the charger is trying to push the full 14.5v through the circuit (without exceeding the 14.5v limitation) and eventually succeeds as the battery becomes fully charged.

Somebody else here will be able to explain it better than me

[wincrasher]

Today I re-ran the test with a few tweaks.

First, I left the RV plugged in over-nite. The refrigerator was cold to start with. Started at 13.4 volts.

Turned everything on again. I suspect the refer is now drawing less. Not a whole lot though.

I adjusted the setting for the Onan autostart to 11.9 volts.

I heard it come on after 5 hours. So that's an additional hour run time. I turned off the generator and started the engine.

After an hour of idling, if you shut down the engine, the system shows 13.2 volts. That's a bit short of the full charge 13.4. After two hours, it was reading 13.3, so I shut it off. Close enough.

Not sure if driving the van would do any better.

[booster]

I was just looking at the spec and install sheets on the converter you got, and it appears to be a constant 14.6 volt output, without any added stages or cutoff. That also appears to be what you are seeing in you tests. That would make it basically a two stage, constant current/constant voltage charger, with no cutoff.

We have heard from a bunch of sources that you shouldn't have lithium batteries on float because it is hard on them, and the 14.6 volts you are seeing continuous is even higher than float by a whole bunch, so it may be even worse.

I think a call to Smart battery would probably be in order to see what they say about it.

Here is a link to how Magnum does one of their profiles that looked good for lithium at first glance, and when I spoke to them they said it is what they recommend for lithium. It is basically the same as the PD charger you have, except it has a full shutoff when fully charged, so no float or continuous charge on the batteries until they discharge some and need it.

http://www.classbforum.com/forums/f5...hium-3679.html

[Jostalli]

Booster is right. If you are charging LiFePO4 batteries to 14.6V you need a charger that will turn off at 14.6V.

[wincrasher]

I'm not sure I agree Booster. The booklet says it drops current as the battery fills. So is sitting at that 14.6 with essentially no amperage a bad thing? I'm probably going to call tomorrow to talk to the folks at Progressive Dynamics about what this charger is doing.

[booster]

Originally Posted by wincrasher

I'm not sure I agree Booster. The booklet says it drops current as the battery fills. So is sitting at that 14.6 with essentially no amperage a bad thing? I'm probably going to call tomorrow to talk to the folks at Progressive Dynamics about what this charger is doing.

If you are staying at constant voltage (14.6) the current will slowly drop as the batteries get charged, and then level off and not drop more once the batteries are full. At that point the small current that is still being put out will be doing damage and generating heat, for sure in wet cells and AGM, and from what we hear, even more so with lithium.

The charge profile in the link shows the charger shut off, and monitoring the battery status only, once charged. The charger is shut off when it gets to a preset amperage to the batteries (so you could stop early if you wanted), a preset SOC (which doesn't work well on the Magnum), or on a straight timer (poor way of doing it). You can chose which you want.

I think a call to PD would be in order, as we may be misinterpreting how the unit is supposed to work.

Sidenote on edit--the amperages we are talking about are very small. Our 440ah of AGM batteries that I have been testing stop at only 1.7 amps when full.

[booster]

A little more reference material.

Here is a lifepo4 charge profile that is pretty typical of what I have seen elsewhere. It specifically shows a total shutoff, monitor, and retop.

[wincrasher]

So ideally, if the charger was "off" or more likely in "idle" mode, it would wake up and provide enough amperage to cover ongoing loads like from the CO detector or other parasitic loads like the stereo?

[booster]

Originally Posted by wincrasher

So ideally, if the charger was "off" or more likely in "idle" mode, it would wake up and provide enough amperage to cover ongoing loads like from the CO detector or other parasitic loads like the stereo?

Actually, that is one area that the lithium profiles appear to be radically different than the lead/acid profiles. Lead/acid would go into float and run the accessories, and the batteries would stay full.

In lithium, because they don't want continuous float, they shut the charger off when the batteries get full, then you run off the batteries until the voltage drops a bit, then the charger comes back on to retop the batteries, repeat, repeat. It is the voltage dip and bump back up on the right side of the profile chart.

This is could be an issue if you don't have a lot of battery capacity because you could be less than full when you unplug from shore power.

[booster]

Originally Posted by wincrasher

I'm probably going to call tomorrow to talk to the folks at Progressive Dynamics about what this charger is doing.

Did you happen to be able to get through to Progressive Dynamics?

[cargovanconversion]

Originally Posted by wincrasher

Just as a follow up, I let the battery charge overnight on the converter.

When I went out to the shop to check on it, the guage still reads 14.5 volts. The charger was warm to the touch. The battery was not warm at all - felt room temperature.

I pulled the power plug and turned the battery disconnect switch, so it will sit dark until the next time I use the coach.

I'm undecided if leaving the shore power connected and the converter activated is a good idea or not.

AFAIK Lithium does better long term if NOT 100% charged; that's certainly true when your van is in storage.

Van Williams

[wincrasher]

I had a great call with the tech support at Progressive Dynamics. Pretty much the converter/charger operates as I suspected. The amperage falls to zero at the maximum voltage of 14.6.

So what I was seeing was that the low voltages (when the battery was depleted), the charger is putting out maximum amperage. As that goes down as the battery fills, the voltage will rise.

If there are loads that demand amperage, then the converter will match it. I did observe that with a full battery, and all my loads (incl the refer) that the voltage drops by 1/2 a volt.

They couldn't answer definitively if it's OK to leave the shore power connected with a full battery. It should be OK, as there is no demand other than the parasitic loads of the radio and the CO detector.

He did acknowledge that some battery manufacturers want charging turned off completely, and some do not. They are working on a charger that will communicate with a battery's BMS, but he couldn't tell me any more than that.