Trailer Battery Load Support

As a followup to my recent discussion about my newly acquired CTEK Multi US 7002 Charger I'd be interested in some further input on the subject of trailer battery load support. :)

First, I should clarify that we normally camp on electric sites, only occasionally "dry camp" when campsite shore power either brown outs or fails completely. :M The few times this happens each season we'd still prefer to power a few devices, most particularly the toaster (650 watts) and coffee maker (550 watts) and to that end last year I installed a 1000 watt PSW inverter. I've also since installed dedicated duplex receptacles in the camper which are powered directly from the inverter so there's no need for a transfer switch, turn the converter off, or force the fridge to gas. The only catch has been that my single G27 Interstate battery does struggle with the toaster load, the obvious solution being to upgrade to a pair of GC-2s or G31s. This however is beginning to strike me as "overkill" considering the very few times each season we'd need this much battery reserve. I'm also reluctant to invest in a pair of new batteries when I know how unsuitable the WFCO 8955 converter in our trailer really is for properly maintaining those batteries. The CTEK will solve that but only for one battery since it's rated to properly bulk charge a battery reserve of no more than 150 AH. Yes, I could recharge a pair of G31s individually but couldn't if I alternately chose a pair of 6 volt GC-2s.

This morning I plugged the trailer Bargman into the truck for load support and with the truck running found that instead of battery voltage dropping into the 11s and causing the inverter to alarm with the toaster running that voltage didn't drop any lower than 12.3 volts. :) Next I dug out a 12' booster cable, connected the truck battery directly to the trailer battery, and with the truck running the lowest voltage I saw with the toaster operating was now 13.35 volts. :B This result has me now thinking, considering the limited number of times we'd camp without shore power, that I might just forego dual batteries, replace my aging G27 with a new G31 next spring, run the truck for the limited number of minutes I'd need to provide load support for the trailer battery, and use the CTEK instead of the WFCO to properly maintain this battery.

Any input on this idea of using the truck (running) as occasional load support to the trailer battery when powering the inverter would be appreciated. :)

landyacht318
Explorer
Oct 04, 2016
BFL13 wrote:
Adjusting the voltage would not help much to lower the amps into a low AGM usually.

Next time I deplete my battery low and plug in meanwell i'll get you some data on that.

Does Phil have 6v full river GC-2?

They have 1.7m OHM each, or 3.4m Ohm for 2 in series for 12v

the full river group31s have 3.8 m ohm

My Northstar-27 had 2.6m Ohm resistance when new, so should suck more juice at lower voltage all other factors being equal.

I often plug my meanwell to depleted NS at 12.2v when MW voltage was set to 13.6v, and the amps are not maxed out at 40 until I crank it upto into the 14's.

What is the lowest voltage your adjustable powermax allows?

I have little doubt you can limit amps to 27 by twiddling the voltage.
I think my buddies powermax 100 amper goes as low as 12.1 volts IIRC.

If it's like Niner's tellycom maybee it will self limit amperage at 14.x volts

Your Stark battery shape and terminals appears kind of similar to the Vmaxtanks AGMS sold on Amazon or even the UB12100 battery

https://www.amazon.com/gp/product/B00B79DPAA/ref=s9_acsd_hps_bw_c_x_11

https://www.amazon.com/Universal-Power-Group-45978-Battery/dp/B0044Z8DJW/ref=sr_1_3?ie=UTF8&qid=1475544450&sr=8-3&keywords=Ub12100

Compare the specs on this page for the UB121000 to your Stark

https://www.wholesalesolar.com/cms/upg-ub-121000-agm-battery-specs-753736796.pdf

http://www.hespv.ca/hesproductspecs/HES/Stark_Battery_TD_ENG.pdf

But also different enough to possibly rule them out as sticker slapper clones. who knows in this day and age of relabelling, reboxing, offshoring, outsourcing and marketing mumbo jumbo( outright lying)
BFL13
Explorer II
Oct 04, 2016
So your old 8a24 that you did the high amp discharges with also had the 30 percent recharge limit, so does that mean you can discharge faster than you can recharge and not wreck these things?

PT mentions gassing with too high a load as a problem with his AGMs (telecom) Does that apply to the Deka 8a too (and perhaps my Stark?

Thanks

full_mosey wrote:
SoundGuy:

Here is the Deka info you need.

I urge you to read page 2 - Charging, and page 3 - Temperature Compensation.

Note that there are only two Volt ranges, Charge and Float. You don't need 8 stages, but no harm will come to your battery. Your 7A charger is less than the 30% rate limit and it will be fine.

If you don't have a temp-comp charger, you might want to get an IR Gun to read the battery post temperatures to watch for the 95F limit.

HTH;
John
pianotuna
Nomad III
Oct 04, 2016
Hi BFL13,

The telecom jars are intended for UPS service--but that doesn't mean the loads are small on them. They rate them right down to 15 minutes of run time to dead.

Telecom cells are a surplus acid design and I'm treating mine as if they were flooded. Too big a load and they gas. Too big a load for too long and they will vent (but so would starved acid design). I set up conservative charging numbers, too. Of course, I went with temperature compensated charging.

BFL13 wrote:

Then you get these "telco" AGMs but are they all UPS type? Acid starved vs not acid starved? Is the not acid starved in danger of venting gas inside your rig same as a Flooded?

Or is there more than one type of "telco" and some are good for Rv deep cycle work and others not?

Then Mex or somebody said AGMs should not have high draws just low draws, but then we have (some?) AGMs being real good at handling high draws with less voltage sag. Do you pay a price for that smaller voltage sag by killing the AGM "before its time?"
full_mosey
Explorer
Oct 04, 2016
SoundGuy:

Here is the Deka info you need.

I urge you to read page 2 - Charging, and page 3 - Temperature Compensation.

Note that there are only two Volt ranges, Charge and Float. You don't need 8 stages, but no harm will come to your battery. Your 7A charger is less than the 30% rate limit and it will be fine.

If you don't have a temp-comp charger, you might want to get an IR Gun to read the battery post temperatures to watch for the 95F limit.

HTH;
John
BFL13
Explorer II
Oct 04, 2016
Adjusting the voltage would not help much to lower the amps into a low AGM usually. Phil keeps telling us he gets his 7345 going full blast into his AGMs at the 13.8 fixed voltage it has due to the low R of the AGMs.

The manual for these Stark batts warns they will vent if overcharged. Then says that means going over the voltage, no mention of going over the 27 amps.

These seem to be rebranded, maybe modified too, versions of some other brand AGM and being used as a house brand. Cannot find a real tech support guy to ask questions, just the local in- house guy in coy robot mode saying we cannot comment on not following the specs, etc.

Industrial espionage might be needed. :)
landyacht318
Explorer
Oct 03, 2016
BFL13 wrote:

With the 55 amp converter and a low battery there is no way to limit the amps to 27.

Sure there is, use 18 gauge wire :)

I take it this is not your adjustable voltage 55 amp converter?

If it were just lower output voltage to just above battery voltage. I do this with my meanwell to lower amperage but my Meanwell only goes down to 13.12v, and on one sealed flooded maintenance free battery drained to 9.6v,this was still in the 25 amp range and the battery was heating quickly and i aimed fans at it, and just kept bumping up voltage slowly as battery voltage rose and amps tapered.

My northstar-27 rated at 90Ah weighs 68Lbs according to spec sheet. Looking forward to your experiments.
brulaz
Explorer
Oct 03, 2016
full_mosey wrote:

...
And the truth will set you free! Four x 66lb 6V GCs = 264lbs and can you outperform 100lbs of AGM for high Wattage draws?

No idea. But so far it's working for our 60A draws. Will soon be trying 90A, prolly the max our 1000W inverter can handle.

full_mosey wrote:

Of course, that 440AH bank will run your furnace fan longer.

HTH;
John

Bingo!

Also we only have solar, and go for days without fully charging our batts when boondocking. Afterwards, or when the sun comes out, I equalize them hard with ~16V.

And the solar charger isn't a particularly fast charger when it's cloudy. Have heard AGM's like a high Amp charge, but not a high V (equalization).

Anyway, AGMs don't particulary like that sort of abuse, or so I've been told.

And weight hasn't been an issue since we got the RAM 2500.

And FLA are cheaper. Especially as I already had two GC2s and so just added two new ones. (I know, I know, not the best idea but then it's not a perfect world).
BFL13
Explorer II
Oct 03, 2016
landyacht318 wrote:
Instant absorption voltage reached is what happens, perhaps.

Or perhaps sides bulge excessive and vents start whistling.

27 amps max per 100Ah capacity at 20 hour rate.

How Is this acceptable to mr parallel charger for 155+ amps??
:)

-------------

EDIT--Oops, if it will only take 27a charging, how can it take 100a discharge running the inverter stuff? What can possibly go wrong?----
--------------

:) No generator goes with the TC, just some solar, so no high amps fast charging anyway, then when home slow is fine.

With the 55 amp converter and a low battery there is no way to limit the amps to 27. Thank goodness I still have the 35a Vector. Or I could use the 40a VEC1093DBD set to 20a.

I will have to rig this AGM up in the 5er to use the Trimetric with the inverter and MW, toaster, etc and see how it does for high draw and voltage sag, then assume it does the same in the TC with its similar inverter. MW set-up.

I will report results.
landyacht318
Explorer
Oct 03, 2016
Sounds like a happy medium and a good plan.

As little as you actually plan on cycling it, perhaps a High CCA pure starting flooded battery would suffice and be even cheaper. It certainly would be more OK with the 7 amp charge rate.

not much info available from Eastpenn as to charge rate

http://www.eastpennmanufacturing.com/wp-content/uploads/EPM-Heavy-Duty-AGM-Guide-Technical-Update-1401.pdf
westend
Explorer
Oct 03, 2016
BFL,
At 64 lbs., you're getting a pretty good amount of lead.
Good choice, let us know how that battery works for you.