Coach batteries not charging

[Goodturn]

We have a 2007 MACA 3991 on a WH 25.5 chassis with a IOTA DLS-75 power converter/battery charger, 2 deep cycle 6 volt Interstate 20 amp/ 232 amp hour batteries installed in March 2009, and a 7000 watt Onan. We were hooked to 30 amp service (surge guard installed) in a camp ground last Thursday, and then dry camped Friday through Sunday where we ran the Genset for at least 3 hours each day. When we were packing up, I had to assist the kitchen slide by pushing it in, and the awning would not retract until we hooked up a boost on the house batteries. The chassis battery started the MH with ease. After driving 250 miles home, the house batteries are showing 50% with a hydrometer. The batteries have never run down to the plates and I've only had to add water twice since March 2009. I have cleaned the terminals. Should I plug in the two-step voltage jack and attempt to charge them with a 12 volt battery charger? I don't pretend to remotly understand how the system works, but I have read "the 12 volt side of life" and the 2 other posts on irv2. Any suggestions?

[Luv2go]

Goodturn, you should plug the two step jack in for several hours, check your specific gravity, if not fully charged plug keep charging with the two step jack plugged in until the specific gravity says they are charged. Then remove the two step plug. Also, when dry camping, it is a good idea plug in the two step jack while you are running on the Genset, 3 hours is a good amount of time and should not boil your batteries.

The normal voltage of the Iota is not really high enough to get a good charge on your batteries, especially after a weekend or dry camping.

The best thing to do to prevent this in the future is to get the "IQ4" (their version of a "Charge Wizard") which will automatically provide 3 stage charging, which is what you are manually doing by monitoring the specific gravity and applying a higher voltage until the batteries are charged.

Good Luck!
Stewart

[Goodturn]

Stewart. Thanks for the information. I'm going to the MH now to see if there is an IQ controller built in. I called the company and they said there should be a sticker on the DLS-75 if it is built in, otherwise, it's a $30. plug in option. Spanky

[Brigadoon]

Is your converter charging correctly when you are plugged in to shore power?

[Goodturn]

How would I test to see if the converter is working?

[Brigadoon]

When mine was on the outs, I just checked my battery voltage with a volt meter (while I was plugged in) and found there was no charge voltage going to the batteries. If you are charging your voltage will be in the high 13's or possibly even into the 14's. If you are not charging your voltage will probably be well less than 12.9 volts.

[Goodturn]

Our batteries are at 11.84 by the volt meter as well as the intellec indicator with the generator running. Both 40 amp fuses in the DLS-75 are good. I checked the ground strap to the batteries and it is well grounded. I guess I'm headed to an RV shop to let them figure it out. Thanks for your help.

[Goodturn]

A quick phone call to Master Techs, a distributor for IOTA, and a few more voltage tests indicate that the converter/charger has failed. They suggested that a power surge may have taken it out, but we do have a Surge Guard always in line. A new DLS-75 is on its way via UPS. Thanks again for your help.

[Brigadoon]

There's a possibility that it was not a power surge that took out your converter.

There is a thermister inside the box that can crack under high temperatures. That's what happened to mine. In my converter, it looks like a nickel sized green disc that has two wires extending down to the circuit board. If it is cracked your converter will not work. It can be fixed by crushing the green stuff off the two wires, then carefully twisting the two wires together. Then solder the wires together.

I did that on mine and it worked like a charm. However, I was not able to do a good solder job with the smallish solder gun that I had with me. In about a month the solder job gave way and I had another converter failure. So I bought a new Iota converter and sent the old one back to Iota. They repaired the old one and I now carry it as a backup.

If you get a chance, I would be curious to know if that was the problem you had with your converter. All you need to do is remove the cover and look for the cracked thermister. Let me know if you cannot identify it and I'll try a post a photo of the thermister in my original, now backup, converter.

By the way, the older converter did not have any ventilation holes in the cover. The new converter is highly ventilated. Talking to Iota sort of revealed that the older designs ran a little hot which can lead to the thermister failure.

[siggyd]

The so called "thermistor" is an MOV (Metal Oxyd Varistor)---just short it out or find a replacement and you are good to go.
Perhaps IOTA will send you a replacement.
Siggy

[Goodturn]

The new unit will arrive today and I will disassemble the old one to see what I can find, and report back. Thanks for the input.

[Luv2go]

Originally Posted by siggyd

The so called "thermistor" is an MOV (Metal Oxyd Varistor)---just short it out or find a replacement and you are good to go.
Perhaps IOTA will send you a replacement.
Siggy

Actually, since the component Brigadoon describes was fixed by removing it and shorting the leads together, it was a thermistor. If it was an MOV, it would be connected across the line and if it was shorted it would short out the line voltage on the converter. Here's a Wikipedia explanation of MOV's and their purpose.

The thermistor is either a PTC or NTC thermistor depending on it's purpose. If it was designed to limit surge currents as power is applied to the converter it is a NTC, that is as current increases resistance decreases. If it was designed to limit the current the converter can pull from the line (for example, if the converter is outputting too much current) it will be a PTC, i.e. as current increases resistance increases. Here is a Wikipedia entry on thermistors.

My best guess is it is an NTC thermistor. In any case, as siggyd mentioned it would be best to go to Iota to obtain the replacement unless you can read the part number off the bad one and identify exactly what it is.

If you can't get a part from Iota (or they want an arm and a leg for it) I can disassemble my spare Iota converter and get the part number from it. Most electronics distributors will stock them.

Stewart

[Brigadoon]

For the record, Iota identified the problem part as a thermister. Additionally, the Iota tech that I was talking with advised me to solder the two wires in question together to solve my problem. He even went so far as to say the solder job, if it was a good solder job, was good for a permenant fix. In my case, the solder job did not hold so I sent it in for repairs.

[Goodturn]

I've got the new one in and working. I have the top off of the old one but cannot identify any blown or fried components. What do I look for?