Charging Start Batteries

CharlesMoore · 07-05-2019, 08:34 AM

I read in the manual of my 2002 36DL that you are supposed to disconnect the batteries by pulling the ground before charging with an external battery charger. Is this really necessary for the Start Battery? I have never done this with any car, truck, tractor or boat I have ever had. I apologize if this question has been asked before as it is a fundamental question.

Jim_HiTek · 07-05-2019, 08:58 AM

In an emergency situation, I wouldn't bother as getting the rig to a safe place is paramount. But if it's not, then yeah, do what they recommend. Reason is the sparks and arcs that can be caused by connecting and disconnecting the camps can travel up the line and damage the computers in the engine, tranni, and/or a bunch of different sensitive electronic devices on board.

But if you do choose to just jump the battery, make sure the charger or car/truck you're using to jump from is off or not running, be careful when you clamp onto the RVs battery to minimize arcs and sparks.

In many RVs though, the NEG cable is easy to access...like they manufactured it that way on purpose just for this situation...and it only takes a few seconds to disconnect.

**creativepart** · 07-05-2019, 10:18 AM

I have a Gas Class A, not a diesel, but I've not seen this warning for the chassis battery. And, as a result I have charged my starting battery without disconnecting anything.

I'm not sure this applies to you and your question - I just wanted to mention this.

When my RV was delivered from the factory the BIRD relay was defective and my starting battery would run down over time even while plugged into shore power for months. That's why I needed to recharge the starting battery. Of course, after the BIRD relay was replaced this was not a problem any longer.

CharlesMoore · 07-05-2019, 11:30 AM

Thanks for the comment. According to Winnebago Tech Svc my coach does not have a circuit like this, I guess it was an option and the first owner did not get this option. However, the alternator does charge both house and chassis batteries when the engine is running but not when on shore power. Therefore, the chassis batteries will slowly go dead by parasitic drain and self-discharge. Right now my chassis batteries are at 12.2 VDC so I want to get them back up to full charge.

On my boat the circuit to do the charging from shore or generator power was called a "combiner" and it first charged the start battery and at 13.8VDC it would parallel the house batteries until 14.2 VDC was reached. There is a similar circuit which was an option I am told. I guess this is what you call the BIRD relay.

**creativepart** · 07-05-2019, 11:37 AM

On older WBGO RVs without the BiRD Relay people install a Trik-l-Start. Even WBGO will provide instructions for you to install one yourself.

https://www.lslproducts.net/TLSPage.html

CharlesMoore · 07-05-2019, 11:55 AM

Hey, thanks for the tip. I may very well get one and install it permanently and add a switch that allows me to disconnect it if I want to (so it does not drain the house batteries too). In the summer we do not use it for periods as long as 4 months at a time but start the generator every month but I may want to bypass the Trik-i-start for some reason.

Jim_HiTek · 07-05-2019, 12:01 PM

The Trik-L-Start and the Amp-L-Start both have reverse flow preventers so there's no worry about them discharging one or the other.

If you don't have it plugged in for long periods...just disconnect the two grounds. Batteries will slooooowly self discharge over months but reconnecting to shore power will perk them up soon enough. Won't harm them either. If you leave them connected up in the RV with no shore power they will be flat in just a couple weeks due to all the phantom draws on them.

I use to keep a pair of gloves and an end wrench in the battery compartment so I could quickly disconnect the battery negatives when I would leave the RV for more than 4 days without shore power.

CharlesMoore · 07-05-2019, 02:02 PM

Good ideas. Yes, I will need a pair of gloves as I put that awful red, sticky, messy corrosion protector on all the terminals.

I'll say thank you to Harbor Freight for their inexpensive gloves of all types. Thanks for all.

Jim_HiTek · 07-05-2019, 02:13 PM

Quote:

Originally Posted by CharlesMoore

Good ideas. Yes, I will need a pair of gloves as I put that awful red, sticky, messy corrosion protector on all the terminals.

I'll say thank you to Harbor Freight for their inexpensive gloves of all types. Thanks for all.

You can avoid that red spray by putting 2 oz of 3-in-1 oil (mineral oil) in each cell of your batteries. This is an over 100 year old hack, endorsed by Edison, that vastly reduces the maintenance you need to do on your batteries...especially if you have a proper modern multi-stage charger in your RV. It will not damage the batteries and pretty much eliminates corrosion.

SaltLife · 07-10-2019, 04:31 PM

It's just Winnies way to cover their butt. A safety thing. Batteries create a gas that can explode if ignited by a spark. I bet every car, truck manual sez the same thing. I've been around many batteries in my over half century on this earth ⁷and never disconnected cables when charging...

JoeC · 07-11-2019, 08:05 AM

Get an Amp-L-Start (a big brother to the Trick-L-Start) and forget about the external charging forever. Plugging in to shore power or driving the rig is all you need to do to charge all of the batteries, coach and starter.

For storage, use the battery load disconnect switch to isolate the batteries from the RV loads and plug in to shore power occasionally to maintain charge. Or you can remove the batteries and charge externally on your workbench. Now which one do you think is easier?