Having battery issues

[gbpack]

Was wondering if anyone can think of possible reasons this is happening. We have two 6-volt golfers (in series) that are 18 months old. They have performed well and there have been no issues until recently. We store our 21BHS in a warehouse when we're not camping and they always put a battery tender on it to keep it fully charged. About 3 weeks ago they called and said that they were having an issue with the batteries. They said that the light on the tender never turned to  green after we the last time we dropped it off (about a month ago). They said that the light would just stay on red (charging) and then eventually it would flash red (indicating a problem). So we picked up the camper and brought it home to load some things into it and while it was home I checked the volts and they were at 12.8 which I believe is fully charged. While it was at our house we had it plugged into shore power so the battery should have continued to get some current. Before we took it back to storage (two days later) I checked the batteries again and they were at 13.2 volts (probably because I had just disconnected the shore power). We took it back to the storage place and now (two weeks later) they are telling me that they are having the same issues...... the light on the tender never turns green and this is a different tender than they used the first time. Then they even disconnected the two batteries and put a separate tender on each one, and that hasn't helped either (both just stay red). Nothing is "on" in the trailer except the CO and propane detectors. Do you think there is something wrong with the batteries or could it be an electrical issue? We need to get this resolved soon because some of the campgrounds on our Maine trip this summer have no shore power (i.e. Acadia NP). Thanks for your thoughts and ideas.

[tinkeringtechie]

Maybe an issue with the tender? When they separated them, did they switch to a 6v tender? (or does it automatically detect?). I'd just do a load test to make sure the batteries are okay first. There's a chance that the self-discharge rate of those two batteries actually exceeds the current output of the tender. The one I have only puts out an amp or two and with BIG batteries you might never get to the float voltage.

[gbpack]

I don't think it's due to malfunctioning tenders as they have used many different ones with the same result. And yes, the tenders automatically sense if it's a 12 or 6-volt battery. There may be something to your thought about the tenders not being able to bring them up to full charge, however the guy at the storage facility says that the tenders will provide more than a trickle charge initially (if needed) before switching over to a trickle charge, so I'm not sure what's happening.

[Merlin]

So if I'm reading the details right, when either battery is disconnected from the trailer, the tender can't bring it to float charge and turn green. That probably means the trailer is ok.

12.8V is full charge, but may not be high enough to have the tender go to float? (Assuming it's a 3 stage tender).

How old are the batteries. Does the date code indicate they were new when installed a year and a half ago? 

Several things seem odd. The flashing red of the tender indicating a problem, the fact the tender couldn't go to green even when you brought the trailer to storage with fully charged batteries, and the fact this is new behavior and things have been ok until now.

If it's not the trailer, the tender(s), or the connections, it seems likely the batteries are just not able to get to float charge any more. What brand and are they wet cell or AGM?  Have you noticed any odd behavior from them while using the trailer like unusually fast discharge or flames shooting out the battery box? 

[DavidM]

I suspect that the batteries may have one or more partially shorted cells due to sulfation. That requires more charging current than the battery tenders can supply to get to 13+ and turn green.

Or an abnormally high resting load on the batteries- check with a clamp on ammeter. Also check the charging current supplied by the tender.

If the batteries are sulfated, they will discharge when the charging source is removed. Check the resting voltage after sitting for a day or so with the batteries disconnected. If it quickly drops below 12.6, they are bad.

David

[gbpack]

Thanks guys. We may have to buy new batteries even though we only bought them in November 2015 and they were manufactured 9 months prior to that. They are wet cell Interstate batteries that we purchased at Costco. If it is the batteries, then it seems very unusual to me that both of them would be having the same problem after such a short period of time. What could have caused them to have problems this quickly? Maybe we'll just use them for a little while and watch the rate of discharge.

[Merlin]

It would be extremely unlikely they both failed without an external cause. Wet Interstates are usually good batteries and so long as they were not completely discharged when you bought them, they are still "young".

As David pointed out, sulfation is bad and it could be both are sulphated from not being charged properly by either the storage facility or the trailer converter. We may be back to what TT brought up and the tenders used by the storage facility are not caring well for the batteries.

I think your approach of using them and watching the discharge rate is fine. GC2 batteries are easy to find, so if you do have complete failure it will be an easy fix.

Do you have an easy way to monitor the batteries?  Voltage is ok, as long as you're consistent in how/when you check it.

[gbpack]

A voltmeter is all we have at this point. Is there something else that I should purchase? Also, any suggestions as to how to monitor and measure?

[Merlin]

A voltmeter is fine. There is a chart in this link that shows the voltages at various states of charge (resting battery at 70F). There is lots of other good (and accurate) info in the link too and also in the more general FAQ it's part of.

https://www.solar-electric.com/learning-center/batteries-and-charging/deep-cycle-battery-faq.html#Battery%20Charging

If both batteries are sulfated (gunk built up in the bottom of the battery that won't recombine in the plates to give them full capacity) to the point they won't get to float voltage, they will also appear to discharge relatively quickly. But, here's where it get tricky.....you probably don't have any info on charge/discharge rates of the batteries prior to this problem and there is no good "standard" reference for your specific installation. I think my advice is to just monitor the voltage and if you see it dip below 50% charge regularly (resting and warm), replace them. I know that's not very helpful, so maybe others will weigh in with something more substantial.

Sulfating is often caused by too deep a discharge or too low a charging rate for the battery capacity and type. There are some devices on the market that claim to restore a sulfated battery, but I've had no luck with the one I tried a few years ago.