Replacing start batteries with deep cycle ones

luvrbus · August 27, 2019, 05:37:04 PM

I worked on a few cell tower generators the starting batteries were part of the backup electrical system for the tower no separate starting batteries for the 750kw 12v92 generator surprised the hell out of me

buswarrior · August 27, 2019, 07:42:04 PM

In this situation, a set of dedicated start batteries would be the ones that couldn't be trusted and require extraordinary observation

Completely the other way around, the cell back-up is thought of as more reliable and measured...

It's all about perspective and monitoring

Happy coaching!
Buswarrior

HB of CJ · August 27, 2019, 08:25:06 PM

This might nowadays be a more philosophical question than a strict MODERN engineering solution. Separating the main engine starting batteries from the auxiliary power batteries. It might be more practical to separate the two. This includes separating ALL House or Coach functions from the automotive chassis. This includes the whatever engine starting batteries from the house Bus Conversion Motor Home batteries.

If your can not start the main coach engine and drive out of whatever dire emergency situation that might occur, then you might, (might) be setting yourself up for a major failure that may have far reaching consequences. Flash floods. Fast moving wild fires. Tsunamis. Civil unrest. Separate the house from the chassis. This is common sense. You do not want non cranking main engine batteries in a critical situation.

Another good reason to have the ability to separate main engine fuel from the generator fuel tank. Another good reason to carry a spare tire, (maybe two) with the ability to repair OR CHANGE OUT the leaky tire. Another reason for a comprehensive spare parts collection. Lots of tools plus the ability to make hasty road repairs. No cell service. No roadside rescue. None whatsoever. Only you. Yikes indeed!

richard5933 · August 28, 2019, 02:33:25 AM

What do you have in place to protect this combines house/chassis battery system from inadvertently running it down too far? Sounds like it's capable of starting the bus, but what happens if it gets discharged too far? Are you just planning to use the generator and/or solar to recharge or is there something to protect things against going below a set point?

When we camp, especially when dry camping, our chassis batteries are disconnected unless they're on the charger. I want to know that I can crank the engine should an emergency arise and we need to move quickly. Not saying that your system can't do this, but I'm curious how.

luvrbus · August 28, 2019, 06:21:51 AM

It will work for you JC ,you may think about using a MT 39 starter when your 42 goes bad a friggin lawn mower battery will start one with the MT39 starter

DoubleEagle · August 28, 2019, 06:33:20 AM

Quote from: HB of CJ on August 27, 2019, 08:25:06 PM

Another good reason to have the ability to separate main engine fuel from the generator fuel tank. Another good reason to carry a spare tire, (maybe two) with the ability to repair OR CHANGE OUT the leaky tire. Another reason for a comprehensive spare parts collection. Lots of tools plus the ability to make hasty road repairs. No cell service. No roadside rescue. None whatsoever. Only you. Yikes indeed!

I agree. While some people rely on others to do things for them, the virtue of being self-sufficient and resourceful is very satisfying and practical. I carry tools and spares, and I try to always have one or more ways to solve a failure of some part. Isolating the batteries from each other, but having a way to connect them when there is a problem, is part of that. Even if you have a road service plan, there are times when a prepared person can get things fixed long before a service person shows up.

lostagain · August 28, 2019, 07:16:07 AM

I feel totally prepared and self sufficient. Like I said earlier in this thread, I do not let the bank get down below 50% state of charge. It will easily start the engine at that. I have a generator with it's own dedicated battery that is charged by solar, generator, or shore power, so it is always ready to go. I remember a few years ago when my batteries were old and weak and sometimes would not crank the engine. All it would take was 5 minutes of generator time to boost the batts enough to turn the engine over to start it.

My inverter quits at a set voltage (I don't remember exactly what at the moment) to protect the batteries.

I know I have gone out on a limb with this where many of you wouldn't dare venture. It is working great, not just on a weekend trip, but on extended journeys. And I am not the first one to do it.

Don't we all drive cars with only one battery? With no solar or generator back up...

I have driven many modern passenger coaches with only one set of starting batteries, off which many auxiliary systems are fed, like a Webasto coolant heater, audio/video to rival a concert hall, AC outlet and USB ports at every seat, lighting, etc, that can all be operated with the coach shut off. As in my bus, the inverter shuts down at a set voltage to protect the batteries to be able to start the engine.

We all do it our way...

JC

richard5933 · August 28, 2019, 07:38:49 AM

True - many ways to go about this.

The comparison to passenger vehicles is a little different though, as they don't typically camp for days on end using the batteries.

On our system I added the Victron battery protection device. It's an automatic battery disconnect that you can program to whatever voltage you want, and it will disconnect at that point. Took a little fiddling to get the voltage set right on mine so that it didn't shut down from a monetary voltage drop due to a large draw, but I like knowing that if I forget to shut something off it will prevent damage to the batteries. Also had to move my charger feed to allow battery charging once the Victron shut things down.

buswarrior · August 28, 2019, 10:16:47 AM

If a busnut wants to spend money defending against imagined Boogey men, personal mistakes, or faulty run-out equipment, we are free to do so.

If a busnut has their systems, personal wetware and equipment, up to snuff, and wants to dispense with the duplication, we are free to do that.

Or, boldly going forth in ignorance in either direction, or some other one?

This isn't a religion, it's a hobby. There's more than one way to do things...

Happy coaching!
Buswarrior

chessie4905 · August 28, 2019, 12:36:55 PM

Maybe one of these lithium ion battery jumpers rated for coach engine might be a consideration. They're very compact.

Scott & Heather · August 28, 2019, 10:52:34 PM

I haven't bothered to read through all the responses but I did just this years ago. My starting batteries are entirely made up of deep cycle AGM batteries. Never been a problem in the three years I've run them. Do what works for you.

chessie4905 · August 29, 2019, 04:19:49 AM

Mine are 2-8d deep cycle, with the Vanner to pull the 12 volt loads. Previous owner was talked into removing the big alternator completely with no replacement. Currently, house and start batteries get recharged by the generator or plugging into shore. Has worked ok so far. Generator has it's own start battery, and I have switches and relays to boost start or gen batteries from house batteries.

Bill Gerrie · August 29, 2019, 05:27:52 AM

I use 6 of the 6 volt golf cart batteries for the house and I thought I had 2 group 31's for the start batteries. I had to replace the start batteries today and when I took them in the guy told me they were deep cycle ones. It turns out the date on them was 9 years old. The only difference in the two types of batteries are the thickness of the separators inside. I replaced them with start type batteries because they were $55 cheaper each. If I get 9 years out of these I will be happy but I probably won't. Five years seems normal. So it turns out the deep cycle ones were working fine for all those years as a start type. Sure changed my thinking on using deep cycle type for a start application. The place where I bought them only sells batteries for many many years so he knows what he is talking about.

richard5933 · August 29, 2019, 05:59:30 AM

The battery on our genset is an 8D deep cycle from Napa. When I first got this bus, that battery was also serving as the house battery, hence the larger-than-necessary battery to start the Perkins.

Sounds like we're talking about two different but related issues here. One is whether or not deep cycle batteries can be used as start batteries. Apparently we have evidence they can.

The other issue is how much redundancy each of us feels comfortable with (or without). Some prefer separate house and chassis system, others are okay with combined systems. Apparently both can be made to work just fine.

Jim Blackwood · August 29, 2019, 07:16:23 AM

Sorta depends on your paranoia level maybe? How many redundant systems do you need? I mean you can go all the way down to a small pull cord generator and if it starts reliably that can get you up and running. Or, if you are more relaxed, you can always drive off in the toad and go buy another battery or two when you have to. Or maybe your bicycle has a basket to carry one...(yeah, wouldn't THAT be a trip!)

I do like the concept of making fuller use of all your batteries, but I absolutely despise going to start the rig only to find it won't turn over. BTDT and hated it. Hated it so much that even once is too much. So, separate chassis batteries for me.

Jim