Two Similar 12V battery in parallel and other questions

Well I just bought a second battery for my RV. My other battery is only a couple of months old so both are new this year. The one battery didn't make it through an unplugged camping weekend so we decided another was needed.

I'm not sure if I should hook them together as one bank in parallel or just swap the connecting cables when one is less than 1/4 full on the battery meter in the trailer.

We are only weekenders - and maybe a week or two here and there. Not full timers at all. And when we camp we are not running a lot of power.

One of my concerns is the batteries are not identical.

One is Canadian Energy's P27 MHC (CDN Energey P27 MHC) The other is an Everstart from Walmart it is the 27DC-850N apparently by Johnson Controls (CDN made)

Both are 27 "RV MARINE DEEP CYCLE" batteries. Both cost about the same ($111 & $119)

But not all the ratings are not exactly the same. The Everstart's MCA is 850 on and only 750 on the "Canadian Energy" battery

The Cold Crank on the Everystart is 675 vs only 600 on the CDN Energy battery.

Both have a "RC" of 180.

The Everystart lists its AMP/H as 120 the CDN Energy does not list AMP/H on the battery or website

As my converter is caput and I have not got around to replacing it I run off of my batteries all the time. I was using a old 6 amp trickle charger to charge up the battery but just bought a Genius Mini 2 charger. It is a waterproof unit and a "smart charger" indeed their marketing gimmick is "wicked smart". Each battery is connected to one of the wires from this charger 100% of the time. It is intended to be mounted on the RV (or boat or whatever) and left on all the time. It does say it is for RV's. The Mini-2 is really 2 4 amp chargers combined in one unit designed to keep two batteries charged. Genius GEN Mini2

I've emailed the manufacture for clarification on whether I should keep both batteries hooked directly to the the charger when they are hooked up in parallel. Or when I connect the two batteries does that make it like one big battery? I am concerned as the GENmini which I bought is intended for a battery with a max capacity of 120 amp/hr. If I hooked the two together are they then considered one battery with 200-ish amp/hrs?

I also have two Coleman 40W Solar systems - each has its own 7 amp charge controller. I will also be hooking these up to the batteries. I can hook them up together (parallel) to have 80w running through one of the controllers or keep them separate and charge each battery independently. Not sure which is the best approach.

SO - connect them in parallel OR keep them separate and just manual swap the connections when the battery charge is getting low. (I suppose there is some sort of switch that could be installed to make this easier).

Besides the inconvenience of switching the cables is there a downside to not hooking them up as one parallel bank? IF isolated that would ensure that we are never totally out of power. (been there done that didn't like hand cranking the slides).

I also wonder about the need to replace our converter. It's $300 for the WFCO OEM 55amp replacement $400 if I upgrade to Progressive Dynamic's unit. (CDN prices) What do I gain? Besides not using the batteries when I have shore power. If I keep them charged what is the difference?

David

Bumpyroad
Explorer
Jul 26, 2014
I thought, and this was back in the dark ages, that the TVs trickled in a little juice to make it easier on them and quicker when you turned it on. pre LED days however???
bumpy
NinerBikes
Explorer
Jul 26, 2014
18 to 24 amp hours parasitic drain, over 24 hour period, just having the battery hooked to the camper at the same time as while charging. 80 watts might get you 4.5 amp hours, times maybe 6 or 7 hours, maybe 8? Do the math. If all you want to do is recharge, disconnect the battery from the trailer while charging, you'll get more into the battery.
Fortkentdad
Explorer
Jul 26, 2014
The trailer's been on battery power all week without any charging. Checked the volts 12.58. Hooked up the two 40 watt panels this evening - going to give it 24 hours and check again tomorrow evening and see what the volts reads. The trailer is sitting idle so only the minimum power draw of the CO monitor and TV/Stereo ready setting. (I'm thinking that it might be wise to pull the fuse on the TV/Stereo when not in use as it does draw something and does nothing - how much does that standby status on a stereo system with TV draw anyway???) Does anything else draw power when not in use? No lights on, fridge is turned off, water heater off, tank heaters off, water pump off.
Fortkentdad
Explorer
Jul 26, 2014
Well I contacted the sales people at "Best Converter" and explained what I was looking for. They recommended the "Boondocker" PM4B-55 MBA replacement unit. At $159 + $43 shipping I decided to pull the trigger. I did not find anything negative about this Boondocker and did read good reviews of this "Best Converter" site. I also returned my Walmart $111 battery and have ordered an exact replacement battery to match the one I bought earlier this year ($109 in Edmonton at the Battery Doctor - $165 locally in town, going to the city on the 1st anyway so will pick it up then). Returned the Genmini2 as well. I do have 80 watts of solar panels to keep the charge up on the batteries. I know that won't be enough to keep them full while boondocking but will extend my camping time a little I hope. I'll see how well this Coleman pair of 40 watt panels works. Maybe I'll need to add another couple of panels.

Thanks for all the advice.

Will post the installation with pictures once the unit arrives.
wa8yxm
Explorer III
Jul 21, 2014
Fortkentdad wrote:

Is the PD really worth twice the money?

Take a look at the Mean Time Between Failures

The PD is cheaper (long term) than the WFFCO

it is also made in the USA not China (WFFCO made in China)
AllegroD
Nomad
Jul 21, 2014
RJsfishin wrote:
To answer some of the questions,.....hook them in parallel,.....less chance you will run them down beyond the 50% rule.
If you use more power than 50%, charge them,...one way or another, even if connecting jumper cables from TV.

x2
50% is 12.24v. If they get less than that, you are sucking the life out of them
MEXICOWANDERER
Explorer
Jul 21, 2014
" But for batteries in parallel.. You can mix and match so long as they are the same voltage and chemistry"

Chemistry includes the age and conditions of individual cells. A sick battery can kill a healthy battery so fast it'd surprise you. /it's always best to cull prospects if specific gravity cannot be matched, or CCA load test amperage differs more than 5%.
tenbear
Explorer
Jul 21, 2014
Fortkentdad wrote:
Gotta figure out which bulbs to order off of eBay. Any recommendations?

I bought most of mine from this vender.

I had mostly 1141 bulbs to replace and I found that warm white 36-3528 (1210) panels and 18-5050 cob lights were a close match. It is probably best to buy a couple and try them before replacing all your incandescent bulbs.
pianotuna
Nomad III
Jul 21, 2014
Hi,

The only time a larger converter is useful is when one attempts to recharge using a generator. If you are plugged into shore power it will make only a tiny difference.

Iota, PD, and Power Max are three good brands. Another is the Parallax Paramode with TempAssure. The last is good in extreme climates.

One feature of the PD is the wizard which allows it to be "forced" into bulk charging for four hours at a time.
Fortkentdad
Explorer
Jul 21, 2014
tenbear wrote:
Lots of good advice re batteries. You might also consider reducing your battery power drain. If you haven't already switched over to LED lighting you might consider that. Switching to LEDs can reduce your lighting power drain by about 80%.

Yes - looking into that.

Gotta figure out which bulbs to order off of eBay. Any recommendations?

And in the mean time we have been using three rechargeable portable lanterns (a Coleman one that looks like the classic lantern - I have two batteries for that one) and two Reactor flashlights that give off considerable light using a bank of LED's. Between these three units we have plenty of light in the trailer without using the conventional lights most of the time.