Engine battery not being charged??

deerjohn · 12-10-2005, 04:45 PM

Should my engine battery be charged by the converter that is charging my 2 house batteries?? My engine battery is holding 11 volts after setting 2 weeks with the coach plugged in to 110 volts. The house batteries are always showing 13.+ after the same period of 110 volts of converter plugged in. The 11 volts in the engine battery never fail to start the engine, but the voltage does not increase after the converter has been on. Is the engine battery only charged by its alternator?? DEERJOHN

deerjohn · 12-10-2005, 04:45 PM

Should my engine battery be charged by the converter that is charging my 2 house batteries?? My engine battery is holding 11 volts after setting 2 weeks with the coach plugged in to 110 volts. The house batteries are always showing 13.+ after the same period of 110 volts of converter plugged in. The 11 volts in the engine battery never fail to start the engine, but the voltage does not increase after the converter has been on. Is the engine battery only charged by its alternator?? DEERJOHN

Tagalong · 12-10-2005, 05:22 PM

Deerjohn,
You might want to include your coach info when asking a coach/manufacturer question. Most engine batteries are not charged by the converter. To boot, there are parasitic electrical draws on the engine batteries from the engine and the tranny. I've purchased both a BatteryMinder and a solar charger (if I do not have access to 110V) specifically for the engine batteries when the coach is parked for longer than a week. The coach batteries can be disconnected at the dash while in storage so the drain on them is prevented.
Hope this helps,
Tagalong

hogbreth · 12-10-2005, 06:07 PM

You can run a jumper from the coach batteries to the engine batteries positive side only, grounds are common. Shore power will charge both.
CAUTION
Remove jumper before you start the engine.

John_Canfield · 12-11-2005, 01:41 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by deerjohn:
Is the engine battery only charged by its alternator?? DEERJOHN </div></BLOCKQUOTE>That's the way my Horizon was from the factory. I have since added a Xantrex Echo~Charge to charge the engine batteries from the inverter/converter.

There is also a good chance your batteries are candidates for replacement due to their age.

kenbt · 12-11-2005, 06:51 AM

I found that the Trick L Start system works great and apparently so did Winnebago since they are now installing them on new models and have give some to complaning previous owners with dead chassis batteries

kcaravelli · 10-20-2009, 01:30 PM

Why do you have to remove the jumper before you start the engine. I just ordered a Trick L Start so I'm covered but would like to know.

MrTransistor · 10-20-2009, 08:43 PM

Hello kcaravelli,

The best way to explain this situation is with a hypothetical. Say the house batteries are at full charge of 12.8 volts. The engine batteries are at 11 volts, which is essentially completely discharged. Now you hit the starter. The chassis battery will have no output since it’s internal resistance is very high so all the current will come from the house battery. The current required by the starter will be comparatively very high, on the order of many hundreds of Amps. The jumper wire will need to supply almost all the current when it is only rated for 10s of Amps., at best. #10 wire is rated to carry 30 Amps. but the short length of wire required to jumper the coach and chassis batteries will only be several feet long. 3 feet of #10 wire has a resistance of .0029916 ohms and that in series with the starter motor (i.e. .015 ohms) will give a current in the wire approaching something like 250 Amps. The engine may start. But since power is calculated as I2 X R, the power in the wire would be over 3000 Watts. This is enough to heat the three feet of wire to the point that the insulation will melt and will very likely catch fire if the starter is engaged for 10 or more seconds.

This problem is compounded with smaller size wire like 12 or 14 gauge. Larger wire can create a problem when the two batteries are at different states of charge when the wire is connected. 1 Volt across three feet of #4 will cause a current of over 1000 Amps., hence a potentially large arc as the cable touches the terminal. Similar to connecting jumper cables between two cars except that the wire resistance in this case is quite a bit higher since the cable is much longer.

There is also the issue of a power failure, or breaker tripping and leaving the coach without AC power for an extended period of time. If there is a jumper between the banks, then all batteries will be ruined with a complete discharge.

Please don’t take these hypothetical numbers as absolutes. There are too many variables to know the precise resistances, currents, and Voltages and they will in turn cause variances in the calculations but you can see that the condition is extremely unsafe.

Play it safe, use a Trik-L-Start, echo~charge, or a converter that has multiple outputs like the Truecharge2 to keep the batteries topped off.

bgsc · 10-21-2009, 06:18 PM

Installed the Trickle charger a year ago and no more engine battery problems like others have said it works so good Winnebago now install them at the factory

kcaravelli · 10-22-2009, 01:14 PM

Mr. Transitor,

Wow! What an awsome post. Thanks so much for being so thorough. It is great to be able to build my knowledge with the help of people like you. Again, great job and I really enjoyed learning all that.
I also ordered the Trick L Start yesterday.

MrTransistor · 10-22-2009, 01:51 PM

Hi kcaravelli,

Your welcome, disabled now and can no longer work but sometimes the brain still functions.

Dsouthw524 · 10-22-2009, 02:13 PM

I know of one person (not me) that left the jumper connected when he started the coach and had a fire in the battery compartment!

JamesT · 10-23-2009, 10:23 AM

I don't believe you need to remove the cables, you can be 'safe' if you want. This would mean you never could jump start your coach. In addition, there is a 'factory installed' switch on my dash to bypass the battery isolater, which is the same as having jumper cables attached to all the batteries.

wa8yxm · 10-23-2009, 10:58 AM

To answer the O/P's question of "Should it be charged"

In my opinion yes, but alas I'm not an RV manufactures

Some companies share my opinion, Because of this my Damon Intruder has an Intelletec Battery Control System which does in fact charge the chassis battery off the house converter.

Some companies do not share my opinion and if you park with the chassis battery connected for say 2 weeks..> JUMP START time.

The Trick-L-Start or the Xantrex Echo Charger as mentioned above add the function those coaches do not have.

Side note:

Some older coaches have low end converters (Damon gave me an Progressive 9180 with wizard.. It just don't get better than that) and on those..... I'd upgrade the converter before I installed the cross-chargers.

MrTransistor · 10-23-2009, 01:19 PM

Hi James,

You are absolutely correct. There usually is a contactor controlled by a switch (as well as the engine) that will connect the two batteries together to start the vehicle in the event that the chassis batteries won’t (generic name is ‘tie contactor’). But remember that the cabling that connects all this together is on the order of 0 or 00 and not the comparatively small wire that is being discussed of 10 to 14 AWG. The 0 or 00 cable is large enough to carry the high starting currents; the 10 to 14 gauge is not.

This setup should have nothing to do with jump-starting the chassis batteries. If you connect the jumper cables and allow the source vehicle to run for a minute or two before trying to start the destination vehicle, then the source has a chance to put a little charge in the discharged battery so that the entire starter current isn’t passing through the jumper cables. I think it would be very difficult to start a vehicle using jumpers, if there were no battery at all in the jumped vehicle. Unless the jumper cables where fairly short and quite large, the added resistance in the cables would limit the starter current so much that the engine may not turn over. I can remember at least twice that this same scenario happened to me. After acquiring a short set of jumpers with very large gauge wire, the engine started and was drivable to the store for a replacement battery.

Hi wa8yxm,

To address this issue, Winnebago started installing battery disconnect switches for the chassis batteries on the newer model year coaches. I agree that the best way to correct this design oversight would be to install a decent charger that has the ability to connect to two or more banks. The Xantrix Truecharge2 / 40 is one of those, in addition to the one you are using. Winne’s choice of a disconnect switch, I’m sure, had to do with cost. The addition of the Trik-L-Start also has to do with cost. Since Winne won’t spring for the good converter/chargers, we have to deal with the problem ourselves, and that means spending bucks. How many is each owner’s decision and I can’t blame anyone for trying to save some of the aforementioned bucks. Ca. (German for ‘approximately’) $100.00 for the Trik-L-Start versus ca. $450.00 for the Truecharge2 equals over 1,100 miles for me, and I’d choose the miles. (Doesn’t mean I wouldn’t like a Truecharge2 though)

Navy Flier · 10-24-2009, 10:31 PM

The simple answer to your question is that on your coach your engine battery(s) are not charged when plugged in to shore power. There are some manufacturers who have installed this capability in their coaches for quite a while. Winnebago start installing Trik-L-Start in 2005. Therefore, for this capability you will need to install a Trik-L-Start, battery minder, etc.

JamesT · 10-25-2009, 09:20 AM

OP - my engine battery doesn't charge on shore power.

MrTransistor, I am wondering if there is a way, or if it would be wise even, to change the dash switch from a "push to power" to a "on-off" switch? A person would have to be careful with this setup, but it wouldn't require the installation of another charger.
Maybe a person could rig up this battery jump selenoid switch to a transfer switch to be safe. That is to say, when the circuit sees 120VAC it closes the selenoid switch, else it is open.

I have jumped many vehicles without a battery in place, hooked up. This is a great way to start a vehicle that has a battery that is completely dead. The cables are not using the power to charge the dead battery, they are using all their power to start the vehicle. Then once you get the vehicle started you can hook the battery back up and charge it off the altenator.

I do have one question from the other day; my RV was on shore power, I was trying to find a 'DC hot wire', I put my volt meter on a wire and got 18VDC. I pulled the battery cover (the step) and heard the coach batteries bubling. I am wondering if the "regulator" in my charger is bad, or the entire charger. How is the best way to check this for this condition, before it boils the batteries dead? Checking the charger for "no charge" is easy, over charge (?).

MrTransistor · 10-25-2009, 03:38 PM

Hi James,

Seems like a reasonable idea to me. I can’t think of any important reasons why this would not be practical. A simple relay with its coil across the incoming line only and one NO contact to pull up the tie contactor would be all that’s needed. This could be done in the power bay of most Winnes. For those that have the tie contactor located remotely from the power bay, all that would be needed would be two wires from the coach B+ terminal of the tie contactor through the NO contact of the relay, to the + terminal of the tie contactors coil. This would allow the two banks to be tied together whenever shore power is applied but not when the generator or inverter is supplying the AC. Starting should not be a problem if connected to shore power since in theory both banks should be at full charge. Sounds good, can any one think of a negative to this?

Getting a little fancier, a DC relay with NC contacts could be in the coil circuit of the tie contactor that would open the line if the ignition switch were turned on.

I’m not as comfortable with the dash switch change out, too much chance of the switch being in the wrong position at the wrong time. Nice thought though.

18 Volts! Disconnect as soon as possible! That’s high even for an equalize cycle. Pull it and have it checked out. If it still only has an output of 18 Volts, can it and get a better one.