House battery voltage under draw?

[tommymsw]

I have a new (to me motor home) and an upgrade from my old one. In my old RV, I had to check the house battery voltage manually. With the new rv, I have a switch on the wall.
However, when I check the batteries while I am using them, they quickly get below 11.9 (to 11.6 or so), but later, when not in use, seem to be OK again at low to mid 12. They are BRAND new. Like one day old!

So, do they read lower when under draw? And I should only read them when they are not in use? Or is something wrong with my readout on the wall?

[landyacht318]

mike-s wrote:

landyacht318 wrote:
The Costco interstate 6v sold in my part of California are apparently Trojan t-605s, with 210AH and 58Lbs of lead.

Pictures?

As I said, I saw somewhere a claim that they were Deka. But, looking into it myself, I'm pretty sure they're JCI.

I borrowed a scale, and the costco interstates I got last year at some point were 58 Lbs on the dot.

Are they indeed trojan t-605 in a different color case?
Who the F knows.

Who interstate gets to build their batteries likely varies greatly in different parts of the country, and probably changes fairly often.

[Almot]

tommymsw wrote:

I didn't realize that plugging them in would be SO much better than driving...

... My hope was to run the generator or plug in at a park and only rely on the solar to keep the batteries topped off from normal drain while it sat empty in my driveway.

My generator pushes 40A I think and that sounds like that will also not be enough (Still working on getting it running).

So I guess the best thing would be solar. I have the 10W and that is clearly too small (wonder why it was even an option). I wonder if it is as simple as just putting a 100w panel where the 10w is? Or if I need an entire new system. Not sure if you need a different controller for a more powerful panel of if it will just charge quicker with the better panel.

Depending on your alternator and how it is wired, driving half a day can be better than plugging it in 20A overnight. Doesn't seem to be the case with your bus, though.

10W solar is small, but not terribly small to maintain 2*6V batteries from discharging.
Really bad 200AH bank could self-discharge 1AH a day.
10W solar could harvest up to 2AH a day, often it will be less, still it doesn't look like it absolutely can't maintain 200AH bank.

But there can be devices in your bus that are always ON, you didn't investigate this. Then there is more draw than self-discharge. How much more, you don't know. Replace 10W panel with 25W and if there is no controller of any kind installed, or it's smaller than 3A, - install some 3A-4A controller. They probably don't come smaller than 5A.

[Almot]

Boon Docker wrote:
Oh such a friendly place.

It was, before he came.

[BFL13]

All you need now is a single 12v Walmart "Marine/RV" battery and take it inside your house when the Rv is not being used to maintain the battery on a small maintenance charger.

Total waste of money to get solar or do anything else with the scenario you describe (shore power on converter nearly always, except at home)

[tommymsw]

Ok... I see the problem now and thanks for all the help.

My old RV charged fast all the time (even while driving), but I only had one 12v battery and I was able to plug it in to my house. (only at 20A)

I didn't realize that plugging them in would be SO much better than driving.

I am 99% sure I do have a 3 stage charger on my new RV. (I am pretty sure I read that in the HUGE manual).

The new RV is too big to pull into the spot in my driveway where I could easily plug in.

I will likely never need to stress the batteries as I don't plan on boon docking. I will likely always be at a RV park aside from the 8 or so hours at a Walmart to sleep. But I do want them to stay charged all the time (for health). My hope was to run the generator or plug in at a park and only rely on the solar to keep the batteries topped off from normal drain while it sat empty in my driveway.

My generator pushes 40A I think and that sounds like that will also not be enough (Still working on getting it running).

So I guess the best thing would be solar. I have the 10W and that is clearly too small (wonder why it was even an option). I wonder if it is as simple as just putting a 100w panel where the 10w is? Or if I need an entire new system. Not sure if you need a different controller for a more powerful panel of if it will just charge quicker with the better panel.

[red31]

Costco, 9/17 and 10/17 date sticker look different than older ones!!!

interstate 'value' 6v are 210ah, 58lbs.

[mike-s]

landyacht318 wrote:
The Costco interstate 6v sold in my part of California are apparently Trojan t-605s, with 210AH and 58Lbs of lead.

Pictures?

As I said, I saw somewhere a claim that they were Deka. But, looking into it myself, I'm pretty sure they're JCI.

Here's a Costco/Interstate one:


Note that the case is very different, it doesn't have the ribbing toward the bottom which a Trojan has:


Now, look at a couple of batteries known to be JCI. Varta:

and Delkor:


The cases match. Also, the post insulator/nut holder is the same (there are other pictures of the JCI/Varta showing that, too). The specs for the Varta 300 208 000 match the Interstate/Costco - 208 Ah, 63 lbs (28.8 kg). And, you can find pictures where the cap opening mechanism looks identical.

[BFL13]

pianotuna wrote:
BFL13,

Thanks for the tidbit about PD dropping down to 13.6 volts at 97% SOC. When I had the large marine battery bank (875 amp-hours) it would take days and days to drop to 13.2, even with the solar contributing to charging.

The 97% is approximate of course. Can't remember where I got that info from several years back.

In general I remember reading that the Absorption Stage has to be ended somehow or it will go to infinity, so they put the artificial cut-off into the chargers.

AFAIK the drop from 13.6 to 13.2 has a different protocol to do with battery activity during the 13.6.

On Interstate 6s, yes there are two sizes same as Trojan has, and probably Costco is selling the smaller size same as they did before when Interstates were US Battery with a 208 size and a 232.

[landyacht318]

The Costco interstate 6v sold in my part of California are apparently Trojan t-605s, with 210AH and 58Lbs of lead.

I would not say that north america Wide that costco interstste gc-2s are trojan t 605.

I installed a pair in a friends rv a year or so ago. They took a lot of time when new for specific gravity to rise up. They did weigh 58Lbs on th dot.

T-105's weigh 62Lbs

[pianotuna]

BFL13,

Thanks for the tidbit about PD dropping down to 13.6 volts at 97% SOC. When I had the large marine battery bank (875 amp-hours) it would take days and days to drop to 13.2, even with the solar contributing to charging.

[BFL13]

theoldwizard1 wrote:

pianotuna wrote:
Hi tommymsw,

The batteries have never been fully charged. They need to get to 14.8 volts. Driving for 9 or 10 hours for a few days might get the job done.

It is almost impossible to fully charge a house battery bank by simply driving, especially if they are deep discharge batteries ! This has been discussed many times before.

The only way to get a 100% charge on a deep discharge battery bank is by using a top quality multi-stage charger and depending on their state of charge, it could take more than one day.

You don't need a multi-stage charger at all. You just need a single voltage charger set to the specified Absorption Voltage for the battery being charged.

The battery will go through its Bulk and Absorption stages (it might skip the Bulk stage if it is already high enough in SOC to do that) All that is then needed is to put the battery on a maintenance charge.

Beware of automatic chargers though, which mostly seem to shut off before the Absorption stage is complete. Often at about 97% SOC. This is where the multi-stage converter comes in handy (but is not essential) The PD gets to about 97% and drops to 13.6 and stays on, in hopes that the battery will get that 97-100 part done while in Float.

The best way is with the single stage at Vabs and with an ammeter, note when the battery is not absorbing any more amps, indicating it is full at 100%. Then you do the switch over to a Float charge.

[DrewE]

theoldwizard1 wrote:

pianotuna wrote:
Hi tommymsw,

The batteries have never been fully charged. They need to get to 14.8 volts. Driving for 9 or 10 hours for a few days might get the job done.

It is almost impossible to fully charge a house battery bank by simply driving, especially if they are deep discharge batteries ! This has been discussed many times before.

The only way to get a 100% charge on a deep discharge battery bank is by using a top quality multi-stage charger and depending on their state of charge, it could take more than one day.

This very much depends on the RV. For a trailer, it's true that it's hard to fully charge the house battery bank by driving, at least without major upgrades to the systems. For a motorhome, on the other hand, it's not at all uncommon to be able to reliably fully charge the house bank while driving. I know mine does a quite decent job over a day's journeying, and I haven't done anything to improve it over the factory setup.

[theoldwizard1]

mike-s wrote:
Citation needed, because Costco sells Interstate, and are reportedly made by Deka (too lazy to find that reference). The specs don't match the T-105s.

The Internet rumor is that Interstate GC2 batteries ARE Trojan T105s. Interstate markets SEVERAL different GC2 batteries and I do not know which model is sold through Costco. T105s are speced at 447 minutes @ 25A and 225AH @ 20 Hrs. Very few batteries are going to match these specs.

Deka batteries are made by East Penn Manufacturing. East Penn DOES make Duracell lead acid batteries.

[theoldwizard1]

pianotuna wrote:
Hi tommymsw,

The batteries have never been fully charged. They need to get to 14.8 volts. Driving for 9 or 10 hours for a few days might get the job done.

It is almost impossible to fully charge a house battery bank by simply driving, especially if they are deep discharge batteries ! This has been discussed many times before.

The only way to get a 100% charge on a deep discharge battery bank is by using a top quality multi-stage charger and depending on their state of charge, it could take more than one day.

[red31]

when did JCI drop the kirkland sticker on costco batts for an interstate sticker?

https://youtu.be/PjaB-zZ7640 JCI mexico!

14.4v Deka flooded??? Deka docs show higher than that.