Battery and USB Advice Please

[VLWino]

This is my first post, so please bear with me.

After living by candlelight and feeling like a hostage to the two 12v interstate batteries, that have already been replaced, with our 2017 25FB FC we are looking to upgrade to the lifeline 6ct 6v batteries. We typically dry camp for up to a week depending on the trip. We have 200 watt solar installed at the dealer. I'm including a picture of the solar monitor to help clarify.

Questions:

Do we need to install a new multi stage charger? I had heard the newer stock ones were better and I wasn't sure if the solar influenced that as well.

Is the 6ct (300ah) overkill? We'll have to lift the lid of the battery box to accommodate it and I believe the 4ct (220ah) will fit without modification. I'm of the opinion that more is more in this case, but thought I'd ask.

Are there any other considerations I'm not thinking of?

Lastly, we burned out both sets of USB ports in the FB and the blue ray cabinet? USB cables were plugged in when it happened. Is this normal or is it a sign of some other problem?

Thank You all for any advice!

-Victor

[uncle_bob]

Hi

Assuming you are going from stock batteries, you had 160 to 200 AH of lead acid on the trailer before. Going to 220 AH is not going to change things much. If you toasted the old batteries by running them down, you probably will toast the new ones as well. Ten or twenty percent more power just isn't enough to change the way things work.

Going up to 300 AH is a boost over what you had. Keep in mind that with lead acid, you only get half the capacity number as usable amp hours. The "stop using" point at 70 F is 12.2V on most of them. If it's cold outside, that point may be up around 12.8V. Go past that and the battery wears out quickly.

With 150 AH *usable* (and a 100% charge to start) with no solar you get 30AH a day for 5 days. That's an average load of just over 1A ... good luck ....

With 200W of solar in the sun, you should get 10 to 12A of charge current. If you get it for an effective 8 hours a day that's 80 to 96 AH. You are running lead acid's so about 20% of that vanishes in the lead acid chemistry. Net is a charge of 64 to 77 AH per day. If you run big loads during the day that would change a bit.

So, if you can stay inside a roughly 70 AH per day budget and live in the sun, you can go on forever and ever. Of course that was also true with your old batteries and they didn't make it.

So what have you gained? On a 5 day trip in the sun, your old power budget was 70 AH. Your new budget is 70 + 30 = 100 AH. Like any budget, in order to keep to it, you need to be able to track what you are doing. A shunt based battery monitor is the key to doing that. If you are already tearing out the batteries .... might as well toss one in.

Another cute device to think about is a battery cutoff device. It monitors the battery voltage for you and shuts off all the loads when you hit the magic voltage. They aren't terribly expensive. Way cheaper than a new set of batteries

So, could you upgrade your solar controller? What did the dealer put in already ? No matter what he used, there is probably something out there for more money that is in some way better. So yes, you could upgrade it. Will it keep your batteries from frying? Probably not. Only proper monitoring and shutting things down will do that. Sorry about that.....

Of course you could go for the same amount of weight in lithiums .....

Bob

[Snowy]

USB ports should not burn out.

What are you connecting to them?

Is the cable USB-IF logo certified or something else? If it's certified the logo should be printed on it or on the packaging it was supplied in.

Typically if USB ports are failing you are drawing too much current from them or shorting them.

Yes, USB ports do also fail. They have electronics in them that do a DC-DC conversion from 12v battery to 5v USB. They can and do fail once in a while but all of them seems strange

[waninae39]

consider lion instead, they can go down to 20% capacity vs only 50% for lead acid
plus they weigh less

[uncle_bob]

Originally Posted by waninae39

consider lion instead, they can go down to 20% capacity vs only 50% for lead acid
plus they weigh less

Hi

If you go lithium, you will indeed need to swap out the shore power converter / charger and the solar converter / charger. You may also decide to drop in a DC/DC converter between the TV and TT as well .... If you are tossing most of this stuff out already, the ones for lithium batteries are not much more than their lead acid counterparts. The gotcha is that to make that be true, you need to be shopping for the *good* lead acid gear.

Bob

[CruizinDux]

Here is a recent thread re USB's
http://www.airforums.com/forums/f37/...ml#post2070405



Bob

[DKB_SATX]

It's true that USB ports SHOULD NOT burn out. However, I think the ones Airstream used by the beds and the blu-ray player are not the best, and if you run them at capacity they may get hot and die. I killed the one by my bed with a phone and an iPad plugged in (with a compliant USB A to C cable on the phone and an Apple OEM USB to Lightning cable on the iPad.) I bought a Blue Sea dual USB port to replace it and haven't looked back.

Originally Posted by Snowy

USB ports should not burn out.

What are you connecting to them?

Is the cable USB-IF logo certified or something else? If it's certified the logo should be printed on it or on the packaging it was supplied in.

Typically if USB ports are failing you are drawing too much current from them or shorting them.

Yes, USB ports do also fail. They have electronics in them that do a DC-DC conversion from 12v battery to 5v USB. They can and do fail once in a while but all of them seems strange

[VLWino]

As usual, the forum experts deliver!

Thanks to everyone! (I have an uncle bob btw. Cool dude)

If I understand correctly:

I'll get a modest boost in power with the lifeline AGM 6ct series (300ah) that, if managed with a battery monitor, should definitely improve our lives where dry camping power is concerned. Just to confirm, these can be run down to 50% per the solar battery monitor before serious damage would occur? (For the record, I don't plan on getting close to 50%). Also, I'm open to battery monitor recommendations. Or can I get by with the solar monitor?

Question: uncle_bob referenced that 12.2v is about the 50% mark if I read that right? Our current stock interstates register that somewhere between 65-75% on the solar monitor if memory serves. Is this due to these being two 12v VS the two 6v batteries in question or is the solar monitor wrong? I feel like at 100% we are at about 13.1v currently.

As for Lithium, I hadn't really considered that yet. I don't look forward to replacing more electronics and we rarely go over 7 days straight of dry camping. I will keep an eye on the tech in the coming years though. That will probably be battery upgrade 3.0.

The USB thread supplied by CruiziDux was fantastic! The verdict: We are not crazy. AS installs sub-par USB ports and these need to be replaced with the Blue Sea brand DKB_SATX mentioned. Should take care of the problem, assuming my issue is the same as all the others on the thread.

[uncle_bob]

Hi

Yup, the 12.2V is indeed the 50% / don't go below point for a lot of lead acid batteries. The exact voltage depends on the temperature and ( believe it or not ) the alloy of lead used in the plates. If your "solar monitor" is saying you are at 75% at 12.2 V ... yikes ....

So why might it say that? Well, the voltage is temperature dependent. Some solar controllers have built in temperature sensors. That's fine if the controller is mounted next to the batteries. If the batteries are .... errr ... outdoors and the monitor is on the wall indoors ... not so good.

Even with a temperature probe at the battery, you still are guessing at what is what. You just can't do things right only from voltage.

So some math:

How much did 300AH of lead acid cost you? If it was under $800 (delivered) you probably didn't get what you though you did. With the best of care and a good deal of use, they will last for four years or so ( to the 2/3 capacity level). How much capacity do you need? Well ... that depends. If you went to 300AH in the first place that sort of suggests you *need* more than 200AH.

So, a really good monitor ( Victron ) is in the $140 to $220 range. Sort of 1/4 of a battery.
A new charger / converter is roughly $200 ( again 1/4 of a battery ). A fancy solar charge controller is about $150 or so. All prices delivered of course. Compared to what you burn on the battery, they each are about 1 year's worth.

Indeed, lithium cells will cost you. They also *should* last a lot longer. Will they last 5X longer? Who knows .... there simply is no data on anything you might buy to substantiate a claim like that ( = none of these guys have been around for 5, let alone 10 or 20 years). If they *do* last for 10 to 15 years, then they are cost competitive.

The other big deal with lithium's is that they weigh a lot less and take up less space. Weight matters very much in a TT. You never have enough room for "stuff". How much that part of it means to you .. who knows. I have 400 AH of lithium and have not lost any real space in the trailer. Weight is slight less than the stock "100 AH usable" lead acid setup.

Lots of fun !!!

Bob