Instant Battery voltage drop

[Timblin]

Batteries on my LTV check out at 12.9 volts no-load. Speicific gravity 'eye' on both batteries GREEN. Will run small loads ( fans, etc.) overnight no problem. If a larger load is offered (tv, electric bed) the batteries instantly drop to 10.4 volts and stay there until re-charged from shore power.

Question 1: are the batteries shot?

Question 2: are they recoverable via desulfation? I am on the road.

[wa8yxm]

Answer both 1 and 2: Unknown.

Where are you measuring voltage? If it is at the battery terminals then the batteries are exhibiting high resistance, this can be due to sulfation and it is possible you may be able to desulfate with one of the better chargers or battery minders. I'd say it's worth the attempt.

If you are measuring voltage elsewhere. .. Say the internal meter in an inverter that has that ability (Prosine 2.0 for example) it may be just a connection that is tarnished or corrorded, clean everything and measure AT THE BATTERY TERMINALS with a good digital volt meter.

[YC1]

Do as above poster recommends but I think you are losing one cell. Clean means clean. Shiny. Take the posts off and use sandpaper where necessary.

And no I do not think you will recover that battery.

[Timblin]

Measuring voltage at battery terminals. Terminals clean as a whistle. Both batteries do it. Measured after voltage drop with batteries disconnected from circuit

Can't find a desulfating charger here in the Traverse City, Mi area. May have to limp home.

[YC1]

Quote:

Originally Posted by Timblin Measuring voltage at battery terminals. Terminals clean as a whistle. Both batteries do it. Measured after voltage drop with batteries disconnected from circuit Can't find a desulfating charger here in the Traverse City, Mi area. May have to limp home.

Seperate the batteries. One could pull the other down if internally shorted. Limp home on one good one then,.

[SUMDALUS]

Timblin,

Shiny battery posts are one thing, but this sounds like a classic case of a corroded battery ground connection.

Follow the primary negative cable to its connection point at the chassis. There is probably a self drilling screw holding the cable to the chassis. Take the screw out, clean the lug at the end of the cable with a wire brush, scrape any rust and paint off of the chassis rail around the hole (where the bolt came out) until it, too, is shiny, put a star washer between the chassis and the lug, and tighten down the screw. If you cannot get good purchase at the original hole, make a new one - but make sure the chassis metal is shiny first.

Poor grounds have a voltage drop across them. Not only will a bad ground connection make a battery appear to be more discharged than it is, but it can also prevent the converter from charging properly as well (esp. if it has 3 stage charging).

Low water and bad grounds are the most common causes of battery problems I find.

Hope this helps.

[Timblin]

Thanks, folks. Found a place to stay plugged in for a week or so then back to PA.. Will get this resolved before heading south in September.