In preparation for replacing my two Optima yellow tops with three Optima red tops, I removed the yellow tops from the RV. After more than a day, they still both showed more than 13 volts DC. I expected any surface charge to have dissipated by then. Why are they reading so high? After charging my three red tops, they quickly went to about 12.7 volts and slowly decreased from there.
One of the reasons for replacing the engine batteries was because starting the engine quickly pulled the voltage very low (6 - 8 volts), from which they soon recovered. I thought the trouble was with the batteries. Now I am wondering if something else is drawing the voltage during engine cranking. Anybody got any ideas about what else I should investigate before using my new red tops to avoid ruing them? (Although the initial testing of my old yellow tops does not look like they really needed replacing.)
And then I have the final mystery: After removing the yellow tops, I noticed the voltage reading on my two plugin DC meters on my dash. The coach batteries read about 13.4 volts (The Magnum display showed 13.7 volt float charge). The meter for the chassis batteries read 13.2 volts, without any batteries in the RV! The only thing that comes close to making sense is that I still have my Echo Charger hooked up; is this what is causing my "ghost" voltage? Is this going to cause a problem hooking up my new battery cables and bus bars?
Any advice or explanations gladly accepted.
Thanks,
Trent
Yes the Echo Charger would be trying to put voltage to the batteries even if no batteries were hooked up in the coach
Can you take the two yellow tops to a battery shop and have them load tested to find out what condition they are in?
I bought a "cheap" battery tester that has done a good job of testing batteries for me. With the tester, I have identified a couple of Red Tops that have failed. Good batteries have registered "cranking amps" on the meter that are comparable to published numbers for the batteries. Bad batteries have show good resting voltages, but failures on the "load test." The "weenie little" test can't put much "real" load on the battery, but it does seem to provide a sufficiently valid measurement to classify a battery as good or bad.
You may want to buy a cheap battery tester (or borrow a good one) and test the batteries. Your local auto supply will probably test batteries for free. Also, clean all the connections you can find. Clean the surfaces on the cable lugs, as well as terminals and clamps.
The last time I had a serious lack of voltage for starting, the culprit was a dirty connection between the lug on the ground cable and the battery post clamp. Everything looked good. I had pulled clamps, and cleaned posts and clamps. I finally isolated the problem by measuring the voltage across the connection. With any significant load (key on and running lights and headlights), there was a significant voltage drop between the lead battery clamp and the copper lug on the cable. I used sandpaper to clean the lug and the area of the clamp that mates with the lug. We started up and set out on our adventure.
I also added additional 4/0 cables from batteries (+) to starter (+), from starter (-) to chassis, and from batteries (-) to chassis. The improvement in cranking speed is significant.
I found a "phantom voltage" on my coach when I was installing an automatic generator starter. With the coach unplugged and ALL batteries disconnected, I found 8.5 volts on some wires in the dashboard. The voltage dropped to zero when I put a blanket over the single solar panel on the roof. :facepalm:
Trent - Just replaced my 10 year old original Yellowtop D31T starting batteries. I removed the batteries and took them to Pep Boys and had them tested. While the surface charge was 13+ all 3 load tested at much less than half their cranking capacity.