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Best boondocking batteries?

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On 8/8/2017 at 3:37 PM, BlueLghtning said:

Thanks for sharing that, as I didn't know those existed. In my case though I have a Shorai motorcycle battery (Lithium) that I've just been hanging onto that should work and it has it's own specialized charger. I think in this case, I could just run a wire to a house plug that's in the storage compartment and let it charge when every I'm plugged in. 

I've installed similar products to the Amp-L.  Try a search online for "voltage sensing relay" 

 

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On 8/8/2017 at 5:09 PM, BlueLghtning said:

So I wanted to ask some suggestions feedback on my thoughts here.

Our toy hauler currently has two exide 12v (80amp hr each) batteries that are split between a side compartment and front compartment. We were told they were a year old, but just in the time we've been trying to get the trailer ready to leave for full time, we seem to draw them down fairly quickly with some slide use, jack use, and what ever else is hooked to them. I think we had some parasitic draws too that was causing issues and really drawing them down, but hopefully I got that fixed. There is no inverter at this time in the trailer, so just the normal 12v things that run off the battery.

We finally were able to put a trickle charger on them for the past couple weeks to keep them topped off while in storage, but that doesn't really tell me how they might work in the real world since we haven't even really camped in the trailer yet. However they've been really dead at least 3 times already that I know of in a very short time period, before we kind of learned what we were doing in that time frame, so I'm in the mind set just to replace them and start with known fresh batteries. I would hate to get out there and find these are absoolute crap and we have to dive into this right away on the road. The last time they were dead, they were down to about 3.5v each which is crazy low I know, so I'm thinking they are pretty much done, plus they seem to come up to full charge way too quickly which I know isn't right either. They are probably very sulfated and I think the battery tender is just masking it right now. When I checked the water after we bought it, they were all pretty low and one cell had exposed plates, so I don't think the previous owners treated these batteries very well.   

My first thought was to just get two 12v Trojan 1275's which are rated at 150Ah each and I can get them for $150ea. That's about 300Ah total, but yeah no more than half of that available. However, I did some measuring and I should be able to fit two 6v T105's in the side battery compartment and easily 2 more in the front, maybe even up to 4 in the front, not sure? Just 2 T105's alone gives me 225Ah which is more than I have now and if I get four, that puts me at 500Ah which is probably overkill for what I currently need, but a good base to start with once we have an inverter. Four T105's would probably be the max I would get right now, even if I could possibly fit two more in the front compartment, and yes I know you are supposed to get all your batteries at the same time, but if we decide to add 2 more in 6 months, is that really a big deal? It seems if we plan on boondocking more with an inverter, it would be smarter to go the 6v route and 500ah is probably a decent start although 750Ah would probably be pretty nice? We are currently in Peachtree City, GA which if you don't know is a huge golf cart community and so I can get new T105's for about $103 each. 

I think the hardest thing about this is just not having experienced any of this yet? 

It sounds like the 2 -12V are done. On our trailer after the first night 2 -12V would at approx (60%) 12.3V.  

When we are off the grid we need at 4 - 6V to keep things running for 3 nights. Then the fun starts....getting the Ah back into the batteries. A generator will give the batteries a bulk and part of an abortion charge in 6 hrs but rarely get into float...that is what solar is best for.

Since you have lots of room for batteries maybe going with 3-4 used 12V ($40) batteries and adding as needed. This is what I did to start.  I'd have 4-12V batteries in parallel on the ground and use a set of jumper cables to connect those batteries to the trailer.  Now I have 4 cheap 6V but even those are not the permanent. The permanent batters will go in when once the solar system is done.

 

 

Edited by J-T

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I did go out and buy four T105 batteries today. I started the generator a few times with just one of the 12v batteries hooked and it started dropping like a rock so it confirmed what I suspected. Also, by removing the parallel connection from the two 12v batteries, I was able to verify where I thought the converter was coming in and charging that battery and that the other battery just connected to the battery is a stand alone so I can easily put the generator on it's own battery.

Two of the T105's fit nicely in the side battery compartment. I just need to figure out a double battery tray solution and way to secure the batteries. The front bay has plenty of room for two batteries. 

I was just reading the other thread about connecting an inverter and I had no idea there were some pretty easy way to do it. I might have an inverter quicker than I thought and then I can concentrate on learning more about solar and their chargers. 

It's kind of fun to figure this all out, I just need more time. :D It's quickly running out. 

 

 

 

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41 minutes ago, BlueLghtning said:

I did go out and buy four T105 batteries today. I started the generator a few times with just one of the 12v batteries hooked and it started dropping like a rock so it confirmed what I suspected. Also, by removing the parallel connection from the two 12v batteries, I was able to verify where I thought the converter was coming in and charging that battery and that the other battery just connected to the battery is a stand alone so I can easily put the generator on it's own battery.

Two of the T105's fit nicely in the side battery compartment. I just need to figure out a double battery tray solution and way to secure the batteries. The front bay has plenty of room for two batteries. 

I was just reading the other thread about connecting an inverter and I had no idea there were some pretty easy way to do it. I might have an inverter quicker than I thought and then I can concentrate on learning more about solar and their chargers. 

It's kind of fun to figure this all out, I just need more time. :D It's quickly running out. 

 

 

 

I wonder if time has always run faster when we are not waiting for it......:D

Thought I'd let you know that with our 50amp charger at 14.8V it would take a little more than 6 hour to bring 2-6V (240Ah) from 12.1 V to a float at 13.4V.

 

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If the focus of this conversation was solar power vs generator power to charge those batteries, would the concepts change much? My house batteries are flooded lead acid, but when I buy batteries as I add solar, I am likely going to bite the financial bullet and spend the small fortune for 2 lithium ion batteries that can hold 100aH each. Given that they can be used almost to complete discharge and not be damaged, plus the amount of cycles the OEM guarantees, they will end up being less per cycle over the life of the batteries. The data on speed of recharging time under optimal sunlight looks good too. The home run for me was that they only weigh 32 pounds.

This has all been very informative reading here. You guys know your stuff! I do understand that this discussion has been mainly about the house batteries that are charged by the generator, but I just wondered how much changes from the theory perspective when the subject turns to solar outside of some additional hardware.

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On 8/10/2017 at 0:06 AM, eddie1261 said:

If the focus of this conversation was solar power vs generator power to charge those batteries, would the concepts change much? My house batteries are flooded lead acid, but when I buy batteries as I add solar, I am likely going to bite the financial bullet and spend the small fortune for 2 lithium ion batteries that can hold 100aH each. Given that they can be

The important difference with solar/gen charging is that the LiFEPO4 will not have an absorption period in the normal sense.  This greatly simplifies charging.

Here's what I mean.  Generator (or alternator) charging with lead is usually one of these scenarios:

  1. charge with gen/alt until absorption is finished.  This requires a long duration with minimal current;  an inefficient use of a generator.
  2. charge with gen/alt until bulk is finished.  This is great for gen efficiency but leaves the batteries at less than 100% SoC, which is damaging to lead chemistries.
  3. charge with gen/alt + solar.  A good combo because gen/alt can do the heavy lifting in Builk then solar can handle the long duration / low current work. 

The first two problems go away with LFP, and having [gen or alt] + solar as in #3 is still a good combo.  But here is something to consider...

[CAVEAT:  I am still wearing out my golf carts so I don't have LFP yet. The following is a theoretical approach to #3]

Gen/alt are by definition intermittent sources of charging, so we can charge LFP all the way (13.8v?) if desired and let it fall back;   no danger of holding at 100% SoC too long. 

Solar is a relatively constant source of energy so it may be productive to reduce solar charging setpoints to whereever we want the bank to hang out most of the time.  80% SoC?  60%? 50%?  I suppose this would be a function of capacity and overnight loads.

 

 

 

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