Charging deep cycle batteries - unimportant questions . . .

[GrumpyDad]

So sometimes my mind wanders. If someone isn't in a rush, and wants to do the best for their deep cycle batteries, is it best to charge them at a low amerage or high amperage? On of my chargers is the little battery tender junior, which has a max amperage of 750 mA. My other smart charger has a few settings 2,10, 15 or Auto. On Auto, it usually ramps up to around 9 amps after a couple of hours. If I turn it to the 15A setting it usually maxes out around 13A.

Anyway, I don't think any of this matters, but over winter when I've got lots of time to do this any way I feel like, any advantage to lower or higher amperage? My setup is 2x Trojan T105 6V if it matters.

Also wondering what the converter in the TT I'm picking up next week will charge at.

Man winter give me too much time to think about this stuff.

[jimp]

750mah is not much, it may keep up with the parasitic drain on the house battery, and maybe on the cranking battery. A 2amp maintainer would be better, can pick 'em up at WM for about $20 or so, or could last year. Haven't priced 'em lately. A smart charger is the best bang for the buck.

[Mustang65]

The best deep cycle battery controller takes into consideration:

- Battery voltage
- Battery temperature
- Charging modes (3 or 4)
- Time in each mode

The charge controllers in the newer TT's use the following in their charging algorithms.. Battery Voltage, Charging modes, and time in each mode. The battery temperature monitor is usually only used with SOLAR battery charge controllers.

Your TT will more than likely have a 30+ amp controller. I doubt if you will ever see a greater than 15 amp charge, and that would be if you were dry-camping for a day or 2 without charging.

The battery determines how many amps it needs the charger determines the voltage. So if the battery only needs 2 amps at its current level, and you have a 15Amp charger, the battery will only take 2 amps from it.

If your TT will have shore-power there is no need to connect a battery charge controller to the TT's batteries. The TT's battery charge controller will do a much better job at keeping your batteries topped off all winter.

Deep cycle batteries unlike their Automotive relatives, do not like a FAST charge, they like a slow charge. It can take a few days to bring a deep cycle battery to fully charged, using the proper charge controller.

No, they will not freeze it they are kept topped off.

Deep cycle batteries also like to be "Equalized" occasionally. Mine get a 15Volt Equalization (3 hours) at least 3 times a year. Unfortunately, since the TT charge controllers do not have a battery temperature sensor, they can not raise the voltage that high.

Below are a few charts that may be helpful. The top one is the charging cycles of a regular TT battery charge controller. The second is the life cycle chart. Best is never let your batteries drop below 12.0VDC (50% rule).

Hope this helps

Don


My Registry

RVing with SOLAR

[GrumpyDad]

Originally Posted by jimp

750mah is not much, it may keep up with the parasitic drain on the house battery, and maybe on the cranking battery. A 2amp maintainer would be better, can pick 'em up at WM for about $20 or so, or could last year. Haven't priced 'em lately. A smart charger is the best bang for the buck.

That 750mA (not mAh) tender isn't used when the batteries are hooked up. Mostly use that on vehicle batteries when I'm not driving them often.

The 2-10-15 A charger is a smart charger, it just allows you to select a target amperage, or it has a fully automatic mode.

I don't need any more chargers and I agree that I don't need to hook up an external charger when the batteries are installed in the trailer.

But through the long Canadian winter, I do bring the batteries indoors.

[ctbailey]

Temperature is monitored for the newest chemistry like the various lithium chemistries. And absolutely the newest fangled LiPo batteries. I’ve not seen any charge controllers that monitor battery temperature for wet cell lead acid batteries.

It does make sense, because you don’t want to boil off the acid, but I havnt seen one yet.


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[Mustang65]

Originally Posted by ctbailey

Temperature is monitored for the newest chemistry like the various lithium chemistries. And absolutely the newest fangled LiPo batteries. I’ve not seen any charge controllers that monitor battery temperature for wet cell lead acid batteries.

It does make sense, because you don’t want to boil off the acid, but I havnt seen one yet.

If you have SOLAR with an MPPT charge controller they have battery temperature sensors. These controllers use temperature, time, voltage and amps in their algorithms for calculating their charging cycles.

One of the main uses is for battery "EQUALIZATION", where the voltage used is 15+ volts. With 15 VDC you get a lot of battery heat, add that to an older battery (higher internal resistance) and you have even more heat. You can set the SOLAR charge controllers to automatically activate the equalization mode or you can do it yourself. My batteries are EQUALIZED at least 3x a year (manually, so I can use the battery disconnect switch to disconnect the TT from the batteries during equalization) or if they have been discharged to 12VDC a lot of times I will manually increase the number of times.

RV battery charge controllers do not have the brains for monitoring battery temperature... due to cost and most batteries are not the TRUE deep cycle batteries. The other issue with EQUALIZATION is that it is pumping 15+ volts into your RV's electronic circuit boards (fridge, radio, CO sensor...) and a lot of mfrs do not recommend voltages greater than 14.5VDC and cringe on 15+ volts. I think that most modern day electronics all use voltage regulators in their circuits, but I would not want to test them out.

Maybe in the future they will start to incorporate them into their models, but I would not bet on it.

Don


My Registry

RVing with SOLAR

[GrumpyDad]

Still thinking . . .

When the batteries (2x Trojan T105) are out of the trailer all winter, and I want to get them charged up, and maybe reconditioned, what's the absolute best charger?

Those CTEK units have apparently 8-stages of charging, and they have temperature sensors so that's nice. They also have a really great reputation.

Speed isn't an issue, so lower amperage is probably fine, unless higher amps actually does something that could improve the health of the batteries.

Even on my vehicles, when I'm charging, I usually have at least overnight, so I've always been of the opinion that I don't need particularly high amperage.

Anyway, any thoughts?

[NH_camper]

One of my past hobbies was restoring and showing farm tractors. They have something in common with a lot of rv's, they sit a lot and their battery doesn't get used often enough. Despite some owners using battery maintainers, etc., battery life can be 1-2 years.

The problem is sulfate building up on the plates. This doesn't happen to batteries that are used frequently, like cars and trucks. The purpose of the equalization Mustang65 referred to is to de-sulfate a battery. It's a "controlled" overcharge.

The unscientific de-sulfating hack I came up with for my farm tractors was a cheap household timer. I plugged a dumb 8 amp battery charger into the timer which was set to run an hour once a week. I used this method for maybe 10 years. I think I had 1 battery that failed around 5 years old. Most lasted 7-9 years.

I don't recommend anyone try this or do this themselves. These days there are better ways. Just something to think about.

[SkyBound]

I have twin Trojan T-105s as well. I have a Progressive Dynamics PD4655 converter upgrade in the trailer to make sure the batteries get exactly what they need, when they need it.

I also bring my batteries inside for the cold Canadian winter. I leave them wired in series and maintain them as one big 12V battery using a Battery Tender (not the Junior) that puts out 1.25A. It is safe to leave it connected to the batteries all winter.

[GrumpyDad]

This forum is bad for my wallet. I've never thought so much about trailers and all the goodies I "should" be buying as I do now that I hang around here.

My trailer spends very little time hooked up to shore power. I don't think a better converter is money well spent for me. Although I do want one anyway.

[Atlee]

I also just upgraded from the WFCO 8955 to the Progressive Dynamics PD4655L converter. I wanted to do this prior to changing from the Group 24 12V to the pair of 6V golf cart batteries, which I did to day.

Since we don't get quite so cold here in Virginia as you do in Canada, I leave my battery(ies) in year round, and keep my TT plugged into shore power here at the house also. I'm expecting the PD4655 converter with Charge Wizard to keep the new batteries healthy for a while.

Originally Posted by SkyBound

I have twin Trojan T-105s as well. I have a Progressive Dynamics PD4655 converter upgrade in the trailer to make sure the batteries get exactly what they need, when they need it.

I also bring my batteries inside for the cold Canadian winter. I leave them wired in series and maintain them as one big 12V battery using a Battery Tender (not the Junior) that puts out 1.25A. It is safe to leave it connected to the batteries all winter.

[GrumpyDad]

I'm in the market for a new portable charger for other reasons, so I was wondering how it would handle the big trailer batteries over the winter when they are out of the trailer.

Sent a note to CTEK, will see if they get back. Wonder if the high Ah capacity will be a problem for the desulphating/maintenance programs in their units like the MUS 4.3

[GrumpyDad]

Got a note back from CTEK: Here it is:

Originally Posted by CTEK email support

HI

Well, I cannot recommend a small charger for such pair of batteries.
I assume you are willing to charge and maintain them in series, and that makes me recommend the MUS 25000 due to the big size (225Ah each)
I understand your thoughts and mostly for maintenance , the Mus 7002 could be big enough.
But i cannot recommend MUS 4,3 or MXS 5.0 for this.

regards, CTEK

Not really a surprise that they said that, as those small chargers aren't rated to charge such large batteries, they just don't put out enough amps. I'm not 100% convinced that the smaller charger couldn't be used to maintain a large battery of a pair of 6V batteries once they had been bulk charged either by the trailer converter or a larger amperage "less smart" charger, but obviously CTEK isn't going to suggest that.

Don't think buying the MUS 25000 is in the cards for me, that's a really expensive unit. At least double the price of something like the MUS 4.3, and that smaller one would work fine for my vehicles.

Of note, the recommended Ah capacities for some of the various CTEK chargers are this:
3.8A charges - 130 Ah
5.0A charges - 160 Ah
7.0 A chargers - 225 Ah
10A charges -up to 300 Ah
25A chargers - up to 500Ah

Anyway, I'm not convinced I'll be buying anything, but I may get bored one day and place an order.