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House battery question

I am going to replace my 3 house batteries.  Any comments on Trojan 8DA GM batteries?  They are advertised as duel-purpose.  My selection is a bit limited.
Thanks, Mike

Re: House battery question

Reply #1 –
Mike, I would almost bet that your house batteries are AGM or GEL type.  If so I would replace them with the same type.  Mixing wet cell, AGM's and GEL batteries is not a good idea and can lead to many problems with charging and maintaining.
Gary B

Re: House battery question

Reply #2 –
We replaced our original gels with Trojan AGM's in 2007 (one started hissing and we had a battery temperature alarm).  The Trojan's have been perfectly fine for 5 1/2 years, now getting a little tired (life probably shortened by "a discharge excursion" during the 2010 roof repair adventure) so we will be replacing them this year.  No complaints (although the installer had to modify the battery tray since the Trojans were slightly larger than the original MK gels).

Be sure to adjust your inverter/charger as appropriate for AGM.

Michelle

Re: House battery question

Reply #3 –
RE:  "My selection is a bit limited"

You may find that NAPA & a few other auto stores can order East Penn gel or agm 8D size batteries.

Re: House battery question

Reply #4 –
If you put AGMs in should you also change over your start batteries as well?

Re: House battery question

Reply #5 –
Quote from: John S –
If you put AGMs in should you also change over your start batteries as well?

Our OEM-equipment start batteries were Optima AGMs (and were replaced with same) so no issues for us.

Re: House battery question

Reply #6 –
The required charge rate of AGMs and wet cells is very similiar and can often be charged at the same time off the coaches converter charger.  GEL batteries require a higher charge rate which is to high for AGM or wet cells, there fore can not be mixed with them.  Both AGM and GEL cell batteries are almost maintenance free while wet cells require continuous maintenance to insure the electrolyte levels are where they are suppose to be. 

You can find a real good tutoral concerning the types of batteries here:  http://www.dekabatteries.com/assets/base/0139.pdf.  You especially want to read page 9, "What are the advantages and disadvantages of the different types of battery designs?"  Those advantages and disadvantages will help your choose which type of battery is best for your coach.

The East Penn batteries that Barry mentioned are the very same company as the Deka batteries.  You can find them at most auto/truck parts stores.  But not the big box type stores who carry their own store brands.  East Penn is the worlds largest battery manufacturere.  EAST PENN manufacturing co., inc.: Lead-Acid Batteries; Battery Manufacturers;

Re: House battery question

Reply #7 –
Quote  Pat C "GEL batteries require a higher charge rate which is to high for AGM "

Pat, I think you have that reversed??
John H

Re: House battery question

Reply #8 –
If "higher charge rate" is referring to the bulk/float voltages, then John is correct, the GEL battery must be bulked at no more than 14.2 volts, while AGM will tolerate 14.4 volts (or higher), while floaded batteries require 14.6 volts (or more).

The reason for these different bulk/float voltages is the lower internal resistance of sealed batteries, with GEL batteries having the lowest internal resistance.

It is possible to mix battery types, if and only if, the voltages each battery sees is appropriate for that type of battery. I have AGM batteries behind the rear tires and a GEL battery behind front tire with the GEL seeing 0.2 volts less then the AGM batteries.

I also do NOT have a seperate "start battery bank", three 8D "deep cycle" batteries work just fine in my 1996 U320.

Re: House battery question

Reply #9 –
Quote
I have AGM batteries behind the rear tires and a GEL battery behind front tire with the GEL seeing 0.2 volts less then the AGM batteries.

Are the AGM's the chassis bats and the GEL for the house?
What's your setup to get different voltages?

Re: House battery question

Reply #10 –
I do NOT have a "start battery bank", I have one start/coach battery bank with three 8D batteries. The three 8D batteries do coach and start functions.

The voltage drop is caused by 35 feet of the negative and 35 feet of positive 000 battery cables between the front battery and the starter/rear batteries when charging (alternator, converter, or solar). In the future, I plan to move the front battery to behind the rear tires on the driver side so that all batteries can be GEL, which is the deep cycle king (I have a 10 year old GEL which is out performing three year old AGM batteries).

Fasinating, that the RV world believes that you must have a "start battery bank", however, I have not had a "start battery bank" for eight years. I am not the only one, I know others. I normally do not talk about this because of the volume of negative feedback. Folks just do not believe that a big diesel can be started from "deep cycle batteries" - but "deep cycle batteries" do have "cold cranking amps". You may not believe that the cranking voltage at the starter with three deep cycle 8D batteries is higher than with three red top Optima batteries, however, my measurements have convinced me that, the cranking voltage with three 8D deep cycles is 1 volt higher than the cranking voltage with three red top Optimas. Lower voltage equates to higher amperage and more heat. Heat is the enemy of a stater.

If you have three 8D deep cycle coach batteries, you do not need "start batteries", however, the position of the batteries, the charger, the inverter, the alternator, and the solar controller must be considered for this "no start batteries" to be successful.

Quote

Quote

I have AGM batteries behind the rear tires and a GEL battery behind front tire with the GEL seeing 0.2 volts less then the AGM batteries.

Are the AGM's the chassis bats and the GEL for the house? What's your setup to get different voltages?

Larry Rubin
2004 U295 38'
2005 Element

Re: House battery question

Reply #11 –
Thanks for the details Wyatt.  Very informative.
Quote
If you have three 8D deep cycle coach batteries, you do not need "start batteries", however, the position of the batteries, the charger, the inverter, the alternator, and the solar controller must be considered for this "no start batteries" to be successful.
I've always wondered about why you couldn't use that type of set up.  Of course, if you are without shore power, the solar charging system has to be working.


A side question:
My 2004 295 came with 3 YELLOW top Optima's in the chassis bank.  Understanding the difference between red and yellow top, anyone know why the factory installed yellow top?

Re: House battery question

Reply #12 –
Quote from: Larry Rubin –
Are the AGM's the chassis bats and the GEL for the house?
What's your setup to get different voltages?
When I got the coach it had two 8D MK Gel batteries for the coach and two wet cells for the chassis. It was not a good mix if I wanted to used the boost to charge the chassis batteries.  Now it has two 8D Deka AGMs for the coach and two new wet cells for the chassis.  Deka (East Penn) says you can use the battery charger's wet cell setting for their AGMs, so all is compatible .

And yes, I did have the voltages reversed in my previous post :-[ .