Battery Upgrade

[peirek]

First let me set the stage. We boondock 1-2 weeks a year. The rest of the time the trailer is plugged into shore power either in storage or at campground with hookups. We have one house GP27 wet cell battery in a rear storage compartment. The battery is in a sealed box and is vented bottom and top. The house battery is approximately 8' from charger (WFCO WF-8935AN-P) connected with 6AWG wire (I am estimating ~10' of wire). I have been taking a second deep cycle battery and connecting to front vehicle connector. This is approximately 20' from charger. I know this is not at all efficient and is mildly effective, but it has served us ok. We run the genny (Honda EU2000) for ~4 hours a day which gets the batteries back up but not fully charged.

I would like to add a second battery to the rear storage compartment but have to consider venting etc. I am leaning towards using two AGMs (6V or 12V?) so as to not worry about gassing and venting. The compartment is big enough to contain both batteries and it will still have a vent top and bottom.

I am looking for guidance on AGM batteries (6V or 12V) and brand. I have learned the Trojans are the best but are they needed for my situation (1-2 wks a year)? I suspect upgrades to the charger will be in order so would like opinions on that. I believe Progressive Dynamics is the preferred brand. I also believe the 14.8 is recommended for AGMs. Is the 6AWG sufficient for a 45A upgrade?

Thank you for your suggestions, directions, and opinions in advance.

[BFL13]

"The PM3LK will always be 13.8 volt max on the 4 stage mode. Just got a Boondocker and it's 14.7, up from 14.6 on the 4 stage mode and has the adjustable lithium mode as well"

That is not correct.

The PM3-LKs have their three-stage mode and the adjustable voltage mode all in one unit. The boost voltage in the three-stage mode is 14.6v and it stays at that for 30 minutes from start -up.

bestconverters gets its "Boondocker" converters from PowerMax to specs as ordered by bestconverters. These specs may be different from PowerMax specs in some cases.

bestconverters seems to be selling their adjustable voltage models as "lithium" chargers. They changed the photo from the external knob pot recently to a photo of a standard old model (external fan, etc), but the above post suggests it is now an LK type with the internal fan and holes in the side for accessing the internal pot. Someday it might all get sorted out with everyone's website clear on what's what.

You can get the specs and operating instructions for the LK on the PowerMax website (use the "products" link first)

[Cydog15]

I think they are probably exhausting the the older models and I don't blame them but like I've said before (maybe here or on a European group I follow) many of your internet experts think they have it all figured out ahead of time without talking to any of them. I got me a great unit from bestconverter and if they do indeed jack the voltage in the bulk to 14.7, everybody wins.

[Cydog15]

BFL13 wrote:

pianotuna wrote:
Hi

Even better may be a boondocker converter:

http://www.bestconverter.com/Boondocker-Converters-_c_154.html this charges at a maximum voltage of 14.6

I'd look closely at the Iota line as well:

http://www.bestconverter.com/DLS-Series-12-Volt_c_144.html this charges at a maximum voltage of 14.76 with the "IQ4" module.

Make sure the wire from the converter to battery bank is capable of the maximum current output.

peirek wrote:
I am starting to lean towards the following upgrade:
1) Upgrade converter to PD 4655 MBA ($193.00). This will enable bulk mode charging (14.4v).


Always welcome critique and opinions.

You don't get a Charge Wizard with the earlier standard Boondocker/PowerMax converters. You would want a previous adjustable voltage model or the new standard PowerMax "LK" model that is replacing the older model.

The LK has adjustable voltage from 13-16.5 and that makes it way better than the Charge Wizard with its limited voltage options.

bestconverters is not showing he has transitioned to the new LK models yet. You can get the PM3-LKs on Amazon

The PM3LK will always be 13.8 volt max on the 4 stage mode. Just got a Boondocker and it's 14.7, up from 14.6 on the 4 stage mode and has the adjustable lithium mode as well. When I talked with them, the PM3 will always be the toned down OEM model and not the hotrod for the aftermarket that bestconverter has.

[JimBollman]

MEXICOWANDERER wrote:
"Does a GC battery allow deeper discharge or do they just have more capacity to start with?"

You need to specify what type of construction. GC flooded batteries are fundamentally different from auto jar batteries.

Golf car AGM batteries have taller plates of the same construction as their car jar batteries.

Flooded GC batteries can tolerate and recover from far worse abuse than can the same campany's car jar RV battery. It's more a question of durability than capacity.

AGM batteries have better voltage level retention under load compared to any flooded RV or GC battery.

If a person believes that there isn't a universe of difference between a premium brand and a membership warehouse battery then they are going to learn the hard way. This does not apply to weekend warriors who do not tax capacity and performance.

What is almost never discussed is how easy or not a flooded battery gets recharged. The difference is generator run time versus ampere hours returned not just claimed or believed. I've seen newer bargain batteries act like aged premium batteries in ease of recharging.

Driving all the way across town to save ten cents a gallon on gasoline reveals a person's mental structure. Fussy about food, near superstitious about tires. Picky about flashlight battery brands, wait a week and pay triple for a haircut but then drive-across-town for a gasoline bargain battery (metaphor for battery knowledge).

Thanks for the education, now I need to do some measuring.

[peirek]

CA Traveler wrote:
Medium duty full extension drawer slides and this box (has to be sealed) and you're good to go.

I’ll have to get creative with the bottom vent as it is currently in the box bottom through the floor and out. Thinking..........

[CA_Traveler]

Medium duty full extension drawer slides and this box (has to be sealed) and you're good to go.

[peirek]

Thanks CA Traveler - I don't have vertical access so I would need to load the batteries and then slide into place given the base of this box is 13" tall. It would also make life really difficult to connect/fill/maintain at the height of this box.

I was considering installing a sliding tray into the compartment but it would further reduce the height of my opening (currently @ 14.5") and probably not allow this box to work. Also would need serious anchor for the tray frame to handle the 120# cantilevered force when opened out.

Still believe I am back to my 2 options listed above.

A wet cell GC2 just does not seem in the cards without a custom built box - which may be doable. Fiberglass lined 1/4" plywood with .75 x.75 framing?

[CA_Traveler]

We used this battery box which we sealed and vented for mounting inside my son’s 5er storage area.

But we had vertical access so no weight issue.

Hopefully you could seal a variety of boxes, JB Weld some PVC for venting and T into the existing venting.

[peirek]

peirek wrote:
@CA Traveler: Great idea about modifying a new box capable of housing the GC2s. I found these Single GC Box but cannot tell if they are capable of being sealed. I suspect not without some mods.

I was correct. When posing the question I received several responses that said no to sealing the case.

[peirek]

No worries BFL13. Always good to be educated!

[BFL13]

OP, sorry for sliding this into the thread--all done now.

Mex, thanks for the clarification. I can manage that.

I have an 8D 250AH AGM and two 27 size 100AH AGMs banked. All three have exactly the same data sheet specs for recharging. They want 14.5-14.9 for "cycle use" and 13.8 for "float use". So a little higher voltage for "cycle use" than Lifeline and some others.

I can do the 250 with my 55 amper and two 100s next, so they all get 20% when needed. The max of 27 per 100 is also kept by doing two 100s with the 55. All good.

I don't need to break out the Honda 3000 at home to use higher amp chargers, which would be a nuisance.

Thanks again for the good info!

[MEXICOWANDERER]

BFL13, communications companies use chargers designed to match their bank. A gigantic bank may have 8 chargers. Or 12. And shutdown of the emergency system happens before their bank gets an over draw down. Discharges are not common. So the 20% rule may not apply. If a bank were drawn down only 30% the 20% recharge rule is far less important than it the bank was drawn to 40% or 50% remaining capacity.

Battery chemistry just has to make itself complicated. The recharge rate is affected by the percentage of recharge achieved. Recharging slowly and constantly underachieving 100% makes life miserable for the battery.

This is why I hammer the hell out of my AGMs when power is restored. The BORG cannot do C1 but it can do 80 amps and that's what the Lifeline is hit with. The power may go off again before even 80% is restored. But I can tell you for a fact that a whamjam recharge makes it easier to achieve .5% later on. Once capacity is lost it's either play a guessing game or do a full on capacity test.

As a GUESS I would offer that if you discharge your AGM to no less than 70% remaining you can forget about the 20% rule altogether, but you cannot forget the .5% rule (ever). Once a week on the .5% followed the 2nd and third week by a recharge as much as is easily doable. Eqvt to your 50-90 rule, only 70-90%

Is the 70-90 doable or is it a real pain?

[peirek]

120+ lbs, I think you are right.

[CA_Traveler]

2 batteries in a box would be very heavy to move. Use 2 boxes with a T on the vent hoses.

[peirek]

@CA Traveler: Great idea about modifying a new box capable of housing the GC2s. I found these Single GC Box but cannot tell if they are capable of being sealed. I suspect not without some mods.
The other issue I face is access. The batteries would need to be installed into the box and the box slid through the opening and into place due to height restrictions. Still doable.

@MEXOCOWANDERER: Duly noted that Deep Cycle Car/Marine batteries will NOT perform equivalent to a GC2. And AGM is the best way to go.

If these darn batteries were on the tongue it would be a very simple decision.