Seeking advice on 12v upgrade- Ch. 1: Batteries

Part II of my answer...

The temperature -difference- will be more than 80F Yes you need to address this however the engine alternator regulator setting is a lot gentler than some charger's absorbsion limit. Therefore, as far as vehicle charging is concerned the difference is not an issue. Hope this helps.

smkettner wrote:
I would have the L16 pair in one spot.

X2 (but I'm biased :)). I would agree with PT in that they're heavy and large. If you have the room, they're definitely my pick.

Hi,

The L-16 dimensions are so large--it makes it hard to deal with. That may be the same problem as the 8-D

I would have the L16 pair in one spot.

If you and your RV can handle the weight of the two GPL-L16T, that appears to be a rather elegant solution. With an average usage of 70ah/day, you would be bumping up to three days without any sun before enlisting shore power, solar harvesting, or a generator to keep to a 50% discharge rate.

When configuring two banks, the exercise gets more complex--more wiring, switching between banks, monitoring both, etc. It's unlikely that any existing DC wiring from the engine compartment to the distribution center will be large enough to adequately handle typical charging or discharge.

Hi,

I would go with twin banks. I use switches from Napa so I can use one bank while charging the other, or turn them both off, or use them together.

Napa DC switch

You must fuse of course.

If the compartments are big enough and your pockets are deep enough 8 D might be better than group 31 as then you don't have as many cells to deal with.

I'd go with poly solar panels and lean towards the 500 watt mark. Of late, high voltage panels have become less than $1.00 per watt so MPPT controllers are beginning to make sense again.

Here is a place to look at panels: Solar Blvd

Duct,

This is exactly the kind of question that I answered regularly when I did a lot of work on performance cruisers before the depression.

First, I like your choice of Lifeline AGMs.
Second, Lead/Acid (LA) batteries don't play well together. If you make up the bank of two strings, please put in switches and gonzo mama fuses.
The switches are so you can periodically charge each part of the bank to independently so as to get all the cells to full density.
The fuses are there as protection in the case that one jar shorts a cell. (This failure is very rare with AGM, but it can happen.) When this happens the good bank dumps all its available power into the shorted cell and the result is not good.

Other than that, go for it.

Matt

Believe it or not ductape, some of your issues have to due with how long you plan on RV'ing With me I'm afraid it's a few years more and that's it. Cycling an AGM down to say 40% of capacity will knock perhaps 10% of its lifespan but that 10% added capacity can be tempting in a borderline situation.

Yours IMHO is a perfect post, it states what you want and why. Kudos.

Alwsys design on "worse case". 125 amp hours = 375 amp hours and you need a battery system with double that (750 amp hours for 50% discharges). From there you can start backpeddling because you say your pig-out days are few.

Your stated average of 210 amp hours of consumption means of course 420 amp hours of batteries. Four group 31 Lifelines seem like a glove fit capacity wise.

If you run your generator "anyway" for hours on end then the following point is moot.

Those four lifelines can swallow a 150 ampere initial charge rate without so much as a burp. If you are going to split up the batteries, keep this in mind. You are going to have to measure with string the accurate cable length, then consult a chart to determine correct length. Beware of single length wire charts, the negative has to return and this is going to DOUBLE the wire length.

IMO your so-far unaddressed issue is having enough charging power. BFL13 has proven to be highly experienced in this department and I hope he chimes in.

Your solar is going to help but I wouldn't stake a trip on guaranteed solar output delivery. It simply means you can run the generator for a shorter length of time and that's it.

Make sure your charger's profile agrees with what Lifeline specs recommend, ESPECIALLY float voltage while plugged in at home.

I am shortly going to take possession of a Lifeline group 31 thanks to an unforeseen miracle thunderbolt from heaven. I have no choice, it has to go under my bed. So, an LCD monitor for me is a must. One that can be seen by twisting my head while in bed. This is a shore-power setup so recharging is going to be gentle as can be. But I may have to, on occasion, cycle it down to 20% of capacity. For those readers about to scream bloody murder, A fan is going to exit any possible slight venting and carry them to a house exit fan intake area. If I lug the monster 150' to the generator shed 2 40 amp MegaWatt chargers are going to feed it for a period that agrees with the recharging time needed for the 24 volt bank. I need my yero (son in law) to smooth the rough path between house/RV and generator/battery/inverter shed. Why do I sleep in the house? Try a 5" thick memory foam mattress!

If the Rolls' bank needs 2 hours at 500 amps then the Lifeline has to recharge as much as it can in that two hour period. The 12.5KW Kubota is not going to laugh and dance and eat lobster while powering a 1200 watt load.

You could configure them as two banks with a marine battery switch to select either bank or both. That way you can disconnect one bank if it has problems or for service without loosing power. i would go with the larger batteries if you have the room.