Fridge-How long on house batteries

[InterBlog]

Originally Posted by booster

.... it appears the life vs discharge depth charts have been misinterpreted over the years and then the incorrect conclusions made got transformed into a hard and fast rule that would have folks believe that their batteries will die very quickly if taken below 50% SOC. If you look at the actual energy in/energy out life, which is what really matters, you lose around 10% of life by going to 20% SOC on every cycle not the 50% to immediate doom we often hear. .....

How does this reconcile with the common observation that new Class Bs are often delivered with the batteries already damaged beyond recovery for lack of appropriate charge maintenance while in transit from the manufacturer and while sitting briefly on the sales lot?

The "immediate doom" fear has its roots in an observed phenomenon. There's a perception that there really hasn't been time to kill the batteries any other way, so it must be true. Hence the mantra, do not sign the paperwork and accept the rig until you've had a thorough opportunity to test its batteries and verify that they are still viable.

[booster]

Originally Posted by Saldar

If there is a solar/line charger interaction I'd sure like to get a grip on it. I believe the issue would be endemic to all Travatos because they share the same stock chargers, so your thoughts might help others. Or maybe the story is obvious to everyone else.

The 3 charging stage voltages (last is float) for the Travato equipment:
For the Zamp solar charger: 10-14 V, 14.4 V, 13.6 V
For the PD line charger ------: 14.4 V, 13.8 V, 13.3 V

It appears the Zamp might dominate the PD, by making it think its 2nd stage trigger voltage (14.4) has been reached. Do you suspect the PD might not do bulk charging sometimes even if it was needed?

I read 14.4 V often during sunny days. Can the Zamp be misleading by deciding to put out 14.4 V before the battery has reached it's physical absorption mode?

I have the pendant to control the PD. Is the amperage supplied by the PD different in the 1st and 2nd stages? If the first stage supplies higher amperage, is it dangerous to force that phase if the battery is in absorption?

I like the PD charger with a pendant as you can force the charger into the different modes. I don't know anything about how the Zamp thinks or what it does that is specific to it.

There are a number of interactions between shore power chargers and solar chargers that can be in the "not so good" category and the brands all handle thing differently. You usually can figure what is going out from the voltage readings somewhat, but you really need to see amps and volts to the batteries to be certain (battery monitor recommendation for all RVs again ). The engine charging can do similar issues, but not as many of them.

Some of the things that can happen:

1. The solar can keep the shore charger from going to absorption mode when you plug in, thus preventing a full charge cycle by the shore charger. If the solar is holding the voltage above the voltage the shore charger is looking for to indicate full batteries (12.7-12.8v usually) the shore charger will go straight to float charge stage, even if the batteries are not truly full. The same thing can happen if the voltage is up due to surface charge from driving with alternator charging. Batteries need to see the full absorption voltage to get a good charge, so this can leave you short of getting the batteries full and keeping them in good condition.

The solution, if you have the PD charger and a battery monitor, is to use the pendant to force the PD into absorption mode, if it doesn't go there by itself when you plug in, and then look at the battery monitor to see how many amps are going to the battery. You need to get to a low amp threshold to know the batteries are truly full. The PD will then run a 4 hr charge cycle at absorption (14.4v) and go to reduced voltage of something like 13.8v. To check if the batteries are full, you would need to force it back into absorption and check the amps, so best just to check it before it switches, so you know if you need to do another absorption cycle. Properly programmed, a battery monitor will tell you if it got to the right amps at absorption voltage by lighting the charged light (Trimetric) so you can tell from that very easily.

2. The solar can run a full absorption charge on full batteries when it shouldn't. This is just the opposite of what happens with the shore charger not doing absorption. If the solar doesn't check the voltage of the batteries when it wakes up in the morning, it will run the full cycle on the batteries at 14.4v based on it's time setting (unless it is a higher end shunt based solar controller like Blue Sky). This problem was first found when we had a Morningstar solar controller, and we found that when sitting in a campground for 14 days on shore power, our wet cells use a whole lot of water even though the shore charger stayed in float the whole time. The solar was putting 8 hours of 14.4v on them every day when they were already full. A member on the Yahoo board had her Morningstar controller destroy her battery by boiling it dry, while it was stored in the yard for an extended time and plugged in. The same thing can happen while driving, although the van voltage is usually too high anyway at that point, but once you park, the solar can stay at absorption on the full batteries.

You will be able to see this one really easily, as if you charge fully with the PD, based on a monitor, and leave it plugged in, if the voltage goes to 14.4v during the next day you have the issue. The normal solution would be to put a switch on the solar panels, not the controller, so you can shut it off, or get a shunt based solar controller.

Unfortunately, all of this takes manual input with the PD charger and non shunt based solar controller if has the issue. Most of the issues can be taken care of with different equipment that makes it much easier, but it certainly isn't a cheap or easy to do in most van.

As always you really can't start to address any of this stuff reliably off of voltage only for the most part, because it is extremely hard to tell what SOC your batteries are in at any given time. You need to have a battery monitor that is setup properly to do this type of thing.

One side thing is that even though the charger say there are different stages for bulk and absorption, to the charger there is really no real difference in voltage setting. In bulk, the voltage target is the absorption voltage (14.4v approx), but the charger doesn't have enough amp capacity to achieve that voltage and it will be lower than 14.4, slowly climbing as the battery charges and the amps to it drop until the amps are enough to sustain the 14.4v on the system. At that time the voltage target doesn't change as it got to the target and will stay at target, but they start a timer or watch a shunt to complete the charging before going to float.

[booster]

Originally Posted by InterBlog

How does this reconcile with the common observation that new Class Bs are often delivered with the batteries already damaged beyond recovery for lack of appropriate charge maintenance while in transit from the manufacturer and while sitting briefly on the sales lot?

The "immediate doom" fear has its roots in an observed phenomenon. There's a perception that there really hasn't been time to kill the batteries any other way, so it must be true. Hence the mantra, do not sign the paperwork and accept the rig until you've had a thorough opportunity to test its batteries and verify that they are still viable.

That certainly happens at dealers and transport, we had it on our Roadtrek. It is likely that the batteries went totally dead and sat a while, which will kill than, and most of the chargers in RVs are horrible at getting batteries full anyway, much less bringing one back from the dead. The dealers I have seen just seem to give the a bit of a boost so the lights come on and call it good, with the batteries still sitting at way less than full. Any lead acid battery sitting less than full for extended times will likely be damage no matter how low the SOC is.

[booster]

Originally Posted by mojoman

When we go into a hotel, I have an aux 75AH AGM battery I switch to to run the fridge 12v compressor (7CF), the battery has its own 40watt solar panel. It allows me to shut down/isolate the lithium bank. We stayed in a resort in Vegas, 100F+ for 4 days. The battery never got below 50%. The van was parked in the sun so the panel was working well.
By putting 4 frozen 24oz water bottles from the freezer into the fridge helped, It took 2 days for the bottles to thaw upon which I replaced them more frozen ones from our room's freezer.

Why do you want the main batteries shut down? IIRC, you have low parasitic losses, or is there some other reason?

[Saldar]

Originally Posted by booster

Voltage is a bit tough to tell much about state of charge, but your numbers are pretty low. To tell for sure, you would have to shut everything off for an hour or so, and then read the voltage, as loads can really mess things up.

I meant to say I see 14.4 V a lot (not 12.4). 14.4 is the Zamp solar absorption level and the PD line charger bulk level. Sorry for the red herring. Booster, I still benefited from your post.

For most line chargers is the difference between "bulk" and "absorption" stages only the voltage they provide. It isn't power? Do most chargers always provide as much amps as the battery will take (up to their limit) for both stages?

It would be great to have a meter like a Trimetric. I think it's a difficult install under the Travato. It may take a long time to earn that many brownie points from DH. AFAIK, even the Travato DIY gurus Wincrasher and FitRV didn't install a monitor in their vans until they went so far as to switch to lithium batteries.

[booster]

" For most line chargers is the difference between "bulk" and "absorption" stages only the voltage they provide. It isn't power? Do most chargers always provide as much amps as the battery will take (up to their limit) for both stages?"

That is a pretty close way to put it. The charger is running at full absorption voltage setpoint for both, but can't get to that voltage for a while because it hits the maximum amps it can provide. Eventually, the amps drop enough for the charger to get to and hold the absorption voltage and the voltage stays there until the amps taper down very low or the absorption timer runs out.

The charger itself doesn't set the amps going to the battery directly, it just picks the voltage it wants to get to. The acceptance of the battery determines how many amps it will take at any given charge voltage.

The charger and battery manufacturers often refer to the bulk as "constant current" and the absorption at "constant voltage" which is exactly what is happening. The constant current will be the nominal amp capacity of the charger, and the constant voltage will be the absorption voltage.

The actual power going to the battery will be almost constantly changing because power is volts times amps, and only one of those is held the same at any given time in the cycle, with the other changing over time.

[Saldar]

Originally Posted by booster

The charger is running at full absorption voltage setpoint for both, but can't get to that voltage for a while because it hits the maximum amps it can provide. Eventually, the amps drop enough for the charger to get to and hold the absorption voltage and the voltage stays there until the amps taper down very low or the absorption timer runs out.

The charger itself doesn't set the amps going to the battery directly, it just picks the voltage it wants to get to. The acceptance of the battery determines how many amps it will take at any given charge voltage.

The charger and battery manufacturers often refer to the bulk as "constant current" and the absorption at "constant voltage" which is exactly what is happening. The constant current will be the nominal amp capacity of the charger, and the constant voltage will be the absorption voltage.

It makes sense. The charger is doing one thing in both stages, and the battery state limits what you measure. But there are two separate PD pendant (manual) settings for bulk and absorb. Are they just "idiot buttons" -- the charger is electrically doing the same thing for both stages? Are you maybe just affecting the timers: Starting from the sequence from scratch by forcing bulk, and starting 4 hours later in the sequence by forcing absorb?

[booster]

Originally Posted by Saldar

It makes sense. The charger is doing one thing in both stages, and the battery state limits what you measure. But there are two separate PD pendant (manual) settings for bulk and absorb. Are they just "idiot buttons" -- the charger is electrically doing the same thing for both stages? Are you maybe just affecting the timers: Starting from the sequence from scratch by forcing bulk, and starting 4 hours later in the sequence by forcing absorb?

I think you are right on with that for the PD. The Bulk button would start an entire charge cycle and if the battery was low it would run through the Bulk and absorption stage observations as you are used to seeing, like the climbing voltage and then constant. If the battery was near full, the voltage would go to 14.4v right away and it would start the timer and be in absorption. If you push Absorption button, I think the timer would start right away whether it was a 14.4v or not, but I don't know that.

PD also uses odd names for the stages so it all could be a bit different. I will have to look up the names they use and the voltages for them, as they are different than everyone else's.

[booster]

I just looked, and PD does not differentiate between bulk and absorption, just calling the combined stage "boost" and they run a timer of 4 hours for the combined stages. The timer being for both wouldn't be my choice, though, as a big bank will not get full in that time if the charger wasn't large enough.

The good is if you have a PD is that you can watch a battery monitor for amps or SOC and force it to run another boost cycle until it is full. The "storage" mode they have is a bit high for a totally full battery but not terrible, but you can force it to "storage" after the charge is done and that is more of a true float voltage. It would switch itself to storage mode, but it will take 30 hours per their charge diagram.

[Saldar]

Progressive Dynamics charger calls the stages "boost, normal, storage, equalization"
(14.4, 13.9, 13.3, 14.4 V). Now I know why PD doesn't use the term "absorb" for stage 2. Absorb describes the battery state, the charger doesn't produce it.

Since the Zamp solar charger uses 14.4 as it's 2nd stage voltage and the PD uses 14.4 for it's 1st stage, I think I'm going to have to observe if they have a bad interaction.

I have a surrogate maker for amps: that's the Progressive Industries EMS 120 V amps-in display. I figure if the van is "off" (no lights, fridge, fans...) and there are amps coming in, they must be drawn by the charger. I do know (?) that 1 120V amp means more 12V amps. But I figure 0 A means pretty close to done charging. It would be great to have better resolution of course. I have seen 8A drawn at 120 V (and van "off") and I think that's the max the 45A charger will draw.

[eric1514]

Originally Posted by Saldar

...
It would be great to have a meter like a Trimetric. I think it's a difficult install under the Travato. It may take a long time to earn that many brownie points from DH. AFAIK, even the Travato DIY gurus Wincrasher and FitRV didn't install a monitor in their vans until they went so far as to switch to lithium batteries.

It is not difficult to install a Trimetric in a Travato G. It takes planning and you need to read the manuals over and over, but it really only took about 4 hours after I had a plan and most of that was spent tidying things up. My wife is also extremely good at this sort of stuff and really helpful.



I built a hard strap for the shunt like Avanti has detailed here on this forum and the rest is just fishing wires through existing holes, protecting them with split loom and zip-tying up everything nice and tight. Programming it to know what full is takes days.

[BBQ]

Originally Posted by eric1514

It is not difficult to install a Trimetric in a Travato G. It takes planning and you need to read the manuals over and over, but it really only took about 4 hours after I had a plan and most of that was spent tidying things up. My wife is also extremely good at this sort of stuff and really helpful.



I built a hard strap for the shunt like Avanti has detailed here on this forum and the rest is just fishing wires through existing holes, protecting them with split loom and zip-tying up everything nice and tight. Programming it to know what full is takes days.

Trimetric and Trik-L-Start !

Nice work !

[Saldar]

Originally Posted by eric1514

It is not difficult to install a Trimetric in a Travato G. It takes planning and you need to read the manuals over and over, but it really only took about 4 hours after I had a plan and most of that was spent tidying things up. My wife is also extremely good at this sort of stuff and really helpful.

That's good news. We have a 59K and I am encouraged that it might also have predrilled holes. I try to be helpful, but I won't too much help hefting the batteries! I noted you alls' creative copper mount for the shunt with an "a-ha". That neat design answers a difficult question on how to the install the shunt on a battery hanging under the van.