Ultimate Battery Thread

they do deteriorate over time, even just sitting around on a trickle charger.  3% a year or so.  5 years old means 15% less AH capacity than when new.  

https://expeditionpo...storage.175797/

 

That doesn't explain why your system wasn't getting back up to snuff by the end of the day though.  Have you been following Hoyden's adventures with charging/batteries?  Lots of good info there.  

http://www.wanderthe...r-solar/page-12

I suspect it is because the fridge is still running while the charging is happening. So during times of driving and solar, I may gain some charge. During times of solar but not driving, I stay even at best. and overnight the battery gets drained more. So a net drop over a few days finally gets me to where I am. 

 

I have followed Hoyden laments and considered the replies here. I did a test yesterday - batteries were at 13 v. Turned on the fridge at 3 pm. This morning the batteries were at 12.2. Not dead but not great. We have two weekend trips coming up that should not be a problem. But we will replace the batteries before our next longer trip. And Patrick, yes, upgraded wiring and alternator would likely help also, but not so easily done on a finished package. We are considering an additional remote solar panel that could be plugged in as an easier charging boost.

True deep cycle batteries? What charge controller? Does your battery monitor show S.O.C:? (state of charge).

Just want to bring up and option that I'm pursuing that I don't see discussed in the forums (apologies if I missed it).

I'm going with a packaged Li-ion system -- Goal Zero or Inergy Kodiak.

 

There are 3 disclosures that really make this work for me:

 

1) I can get a very good discount on Goal Zero products -- as in cheaper than it would cost me to cobble something together.

2) I am starting from scratch so I am not retrofitting or changing technologies.

3) I am an energy sipper. A 1 KWhr supplemented with solar and onboard DC charging will allow me to meet all my expected energy needs and keep the discharge to 50% or less for optimal life and cell health.

 

Both Kodiak and the GZ Li 1000 are NMC batteries that come with a PWM controllers. The GZ has a MPPT available that I consider necessary. They are also coming out with a DC vehicle charger in a couple weeks (Kodiak already has that, I think) and a better 300W wall charger (absolutely necessary, IMO). Kodiak has a better charging profile.

 

Let's see... other differences

The larger GZ systems have WIFI but that makes little sense to me for camping. However, they are coming out with bluetooth capability, so that's nice.

 

A big plus for Kodiak is the claimed wt. - 20 lb. The GZ is 40 lb. which is ridiculously heavy for Li-ion batteries. The difference is all packaging. Regardless of the exact NMC technologies used, there is not that big of a difference in the specific energies to account for a 100% wt. penalty. I'll be bringing the battery indoors to store and charge on cold days (even while on the road, maybe), so that could be an issue as I age and weaken. Kodiak also has more outlets and battery chaining with Pb acid (ugh), if you want to expand capacity on the cheap.

 

Even though there is a huge marketing discrepancy w/ regard to battery life, they are about the same (they just use a different DOD benchmark).

 

Anybody use either of these - or a similar Li-ion/BMS package? It seems LiFePO4 batteries are favored in the forum discussions but I think that is just b/c of one popular supplier.

 

Also, do the campers usually come with 12G wiring. I can't imagine ever needing more ampacity than 12G can handle (I'll have to check the NEC but I think it's like 20A continuous). However, I know some of you have pretty big solar systems.

 

Thanks.

The reason that LiFePO4 batteries are favored is because of their backwards compatibility with 12v lead acid systems and safety.  The Goal zero (and similar) NMC batteries are actually 11.1V batteries, which can cause issues when trying to interface with a vehicle and accessories.   You can't charge NMC batteries from an alternator (directly) and you can have issues running 12v appliances with low voltgae cut off's etc.   LiFePO4 has a 12.8V nominal voltage (13.2V when fully charged) which plays nicely with alternators and other systems that were designed to work with lead acid vehicle batteries.  

 

LiFePO4 are also more tolerant to poor handling the NMC.

 

Unless there is some other motivating factor (in the case is seems like a steep discount), they are likely not the way to go for a vehicle installation. 

Thanks Rando. Just got my truck yesterday, so my attention is a little scattered. Forgot about the NMC low voltage. The GZ spec gives a nominal voltage of 10.95. I assume that would wreak havoc with a Dometic fridge. Can you adjust the voltage cutoff on the fridge and, if so, how much does it help? What other appliances would be problematic?

 

I just chatted online w/ GZ and the said they are coming out with a voltage regulator to regulate the battery DC output ports. That's their solution and it should be out "by the end of the year".

 

I'm not sure this is a show-stopper b/c I could just run the fridge off the inverter (2 outlets). The efficiency penalty is not a factor b/c it's small and I am over-specing my battery capacity.

 

On the other hand, I see my big discount eroding fast with these add ons -- voltage regulator, MPPT controller, forthcoming DC charger (for alternator charging). However, I do like the portability (although I could probably package a home brew system for easy camper removal).

 

The LiFePO4 compatibility benefit might go away with the new voltage regulator. I don't know. Would like to hear your thoughts. Also, you mention that "LiFePO4 are also more tolerant to poor handling...". Do you mean temperature limits for charging/discharging or are you talking about the robustness of the cells with regard to vibrations and stuff.

 

Thanks for the feedback. I welcome any other advice. 

 

Thanks.

Obviously just my opinion here - but this seems like a lot of kludges to get a a round peg into a square hole. 

 

You need a DC-DC converter to charge the battery off the alternator (which may or may not be available "soon").  This is both an extra device and extra expense, but also limits the charging current to whatever the DC-DC converter is spec'd for.  With a direct connection the the alternator (either lead acid or LiFePO4) the only limit to charge is the size of you alternator and wires. 

 

You will need to convert the DC output to AC to run the fridge (figure 10 - 20% efficiency loss right there) then the fridge will have to internally convert that AC back to DC to run the compressor (maybe another 10 - 20% efficiency loss).   Also the inverter has to run all the time, regardless if the fridge compressor is running or not, so you also have the inverter quiescent current being drawn 24/7.   

 

As to the robustness issue - the LiFePO4 chemistry is inherently more tolerant of abuse (over charging, over discharge, mechanical damage) than the NMC chemistry without posing a fire risk.   Not that the NMC battery will represent a fire risk inside the GZ, but you are relying on the protection circuits to avoid this.  

 

So yeah, you can probably get it all to work, but at this point is the extra complexity and loss of efficiency really worth what ever savings you may have?

 

In the context of this being the 'ultimate battery thread', I think it is important to point out that for most people this is not a great battery solution. 

Edited by rando, 01 November 2018 - 02:04 AM.

I added some links to recent posts on batteries and battery chargers as well as to East Penn (Deka) company battery info  - on page 1 post #2

I looked through all the faq's can't find my answer.

I have a interstate deep cycle, topped off yesterday @ 15.75dcv
Using a Sears 1.5 amp charger
Battery at rest of rest+/- 13.6

I have a Napa DP coach battery that I keep topped off using the inverter in the camper and it tops at 13.7 dcv, at rest the DP is +/- 12.5 dcv. Why the 2dcv difference in the floating voltage?

Voltage of about 13.5-13.7 is the battery charger float voltage rather than the battery resting voltage.  The charger will keep the voltage there to ensure the battery remains fully charged in storage.

 

Your voltage of 12.5 volts is the battery resting voltage. If fully charged on a newish AGM battery, expect about 12.7-12.9 volts.  That more closely represents the battery resting state of charge. To me 12.5 represents an older battery and possibly a Flooded Lead Acid (FLA) battery. I assume the DP means Dual Purpose but it could be either AGM or FLA.

 

If you see 13v plus, the battery is being charged or has just come off charge. That is why you need to wait several hours after charging stops to see what its full charge resting voltage is.

 

Paul