Solar charge controller coupled to power converter question

Well I just read a post from another rv forum relating to the same issue. The guy that made the post confirmed with interstate customer service that the gc2 series batteries need to be charged at a voltage of 15.3v due to the chemistry of that battery series. This is also the voltage specified for absorption on the interstate charging sheet. So this voltage requirement is quite a bit higher than any converter I know of...

This is why I was looking into either a step up converter or a solar controller, because in theory you can set the voltage. Anybody got any ideas?

No solar charge controller is going to make the output voltage higher than the input. They can make the output lower than the input but that's not what you want to do.
I think adding some sort of add-on to a less than ideal controller is the wrong way to approach the problem. Why not swap out the converter for a better one?

Morningstar controllers are programmable. I Have a 185W high voltage (70V no load) that produces usable current from sun up to sun down and in a shaded camp site. Our 10A Morningstar MPPT Sunsaver works very well.

Since it is an internal timer and you made a "dongle" for it, I'd simply click the dongle a 2nd time, and a 3rd time, etc.

sfpcservice wrote:
It is actually a WFCO 8845. I can get it to go into boost because I built a charge wizard type of remote. My controller has a remote plug and it was pretty easy to figure out what the 3 pins did. If a solar controller won't work my next thought was a dc-dc step up controller. I could set the voltage where I want and the amperage at max, and I assume it would pump full current in and taper of as the voltage I set was achieved...?

Also the main problem is mine will only hit 14.25v and timeout after 4 hours... this is where a hydrometer shows I am just above dead...

Use this for a boat anchor and get either a progressive dynamics or iota. The WFCO's are junk. The 8955 I had would never go into boost/bulk mode; only absorb and float. Many others here have the same complaint.

How many amp hours is your battery bank?

Why will it not fully charge from whatever you started at to 80% full in just 4 hours?

Will unplugging the charger re-set the 4 hour timer? If you take away the 120 volts for say 10 minutes, and put enough load on the battery to get it below say 12.4 volts?

Why not just install a few solar panels, and let that system keep the battery full all the time?

You can buy a 140 watt solar panel for about $229 with aluminum frame. If you wanted to wire a bunch of them in series, then a MPPT controller will give you the higher than average voltage you are looking for. Or a PWM controller is very low cost, and will leave more of the budget for buying panels.

SunElec.com

By the way, a MPPT controller should be able to switch 12 volt power up to say 14.5 volt power, but I have not tried it. I did consider it as a way to charge a trailer battery from the long line leaving the truck alternator, but find that solar panels are much less expensive. But I have also heard that a MPPT controller will short circuit the panel output while charging it's internal capacitors, so not sure if it might work, or short out the system?

14.25 volts should be enough to fully charge a battery in a reasonable time, without overheating the battery. I found that my golf cart batteries got warm when charged at 45 amps with my Trace M1215 inverter/charger in my RV, it has a 70 amp charger max rate, but I normally adjust it to only 50% charge rate to both keep the fan off, and keep the battery voltage from getting so high that the battery might warm up. Personally I do not like the charge voltage over 14.0 volts.

Good luck,

Fred.

It is actually a WFCO 8845. I can get it to go into boost because I built a charge wizard type of remote. My controller has a remote plug and it was pretty easy to figure out what the 3 pins did. If a solar controller won't work my next thought was a dc-dc step up controller. I could set the voltage where I want and the amperage at max, and I assume it would pump full current in and taper of as the voltage I set was achieved...?

Also the main problem is mine will only hit 14.25v and timeout after 4 hours... this is where a hydrometer shows I am just above dead...

Is that a Progressive Dynamics or a Boondocker? I assume it is a PD and it will work great for your batteries. Have verified charging voltage? WFCO is notorious for NEVER going into 14.4 boost mode.

No there are no programmable converters.

Good solar controllers are very programmable. Really need 100+ watts of solar to drive it though.

Could also get a manually controlled power supply if you really want to hold 14.8 volts for an extended period. This is not a set it and walk away option.

sfpcservice wrote:
I've noticed through several days of testing that my converter drops out of bulk charge mode loooong before the batteries are where they should be, and in float mode it would take a couple weeks (if ever) to finish the charge acording to hydrometer readings.

I was considering adding a charge controller between the converter and batteries. I'm hoping this would maintain a charge voltage high enough to deliver a decent charge, and the higher current would lower the voltage between the converter and controller enough to kick the controller into boost and provide the amps for the charge.

The logic in the converter is that it attempts to reach 14.4v in boost mode or it times out in 4 hours and drops to 13.6v. If the voltage drops below 13.2, it goes back in to boost.

I was thinking this logic might play nicely with the charge controller, and I could set the volts on it to 14.8 which would give me a nice charge.

Will this work?


Also, are there any programmable converters out there?

No, I do not believe that would work. Just one, among other reasons: A charge controller requires a higher voltage on it's imput in order to regulate a charge to the batteries. If your battery charger is dropping down to float charge prematurely, then it is not providing sufficient voltage for a charge controller to work. Fix your battery charger. That is where the problem lies. Is it set for the proper battery type? ( SLA, AGM, GEL ??? )

Edited subsequently: In retrospect, it might work if you use a modern MPPT controller. Still - fix/replace your original controller would be the more elegant solution -- or as some others have suggested, add solar.