Battery charging

Topic: Battery charging (Read 1344 times) previous topic - next topic

Battery charging

April 25, 2016, 02:13:47 pm

When boondocking it takes about 3 hours of generator time a day to keep the batteries up. It seems like it takes forever to get to float. I generally shut the generator off when it gets down to 20 amps or so. Batteries are 2 year old MK 8d AGM's. Does that sound about right, or do I need to let the generator run until it goes to float?

Re: Battery charging

Reply #1 – April 25, 2016, 02:27:51 pm

Quote from: bbeane – April 25, 2016, 02:13:47 pm

When boondocking it takes about 3 hours of generator time a day to keep the batteries up. It seems like it takes forever to get to float.

Would be interesting to hear what others have to say. When we were up in Death Valley, off the umbilical for three days, never ran the gen, but we have no inverter and are power misers. When we got back to Ajo and hooked-up to the pier, it was amazing how long it took our (fresh) batteries to get to "float". With these sort of coaches, there is a drain at all times, and that, I assume, is the whole deal!

Re: Battery charging

Reply #2 – April 25, 2016, 02:39:53 pm

I have the same issue and usually shut down as the output gets around 20 amps also. Then about every three days I let it go into float to keep the batteries conditioned. This is my way and I am as curious as you are as it seems that to run a 10 kw generator to charge below 20 amps dc is a waste.

Re: Battery charging

Reply #3 – April 25, 2016, 02:51:42 pm

The good thing about the long charge time is that the batteries still have life left. If they charge up quickly after a 50% or more discharge, not much capacity left. Lead acid batteries loose capacity with age. It's like they become smaller electrically speaking. I run my generator until float is reached and then shut it off as very little charge is gained in float. I don't like to listen to the generator run either.

Re: Battery charging

Reply #4 – April 25, 2016, 03:14:20 pm

I went without hookups for about 100 days this past Winter in Az. Only put about 10 hours on my big generator but ran my Honda 2000 a few hours a day or just until I reached float mode with 2- 8d's agm type. Love that Honda sips fuel and very quiet under minimum load. Wouldn't leave home without it even if I had 500 + watts of solar!!

Re: Battery charging

Reply #5 – April 25, 2016, 03:29:47 pm

That answers my question.. the honda.. should augment my 900 watts solar easily. .thanks Doug

Re: Battery charging

Reply #6 – April 25, 2016, 03:55:22 pm

Bruce ---- Just for the sake of knowing, check your gen set output voltage when you are charging batteries. If you have a lot of other load, your batteries may not be getting enough charging voltage and thus less current and therefore it would take longer to get to a float mode. Have a great day ---- Fritz

Re: Battery charging

Reply #7 – April 25, 2016, 03:57:01 pm

Quote from: bbeane – April 25, 2016, 02:13:47 pm

When boondocking it takes about 3 hours of generator time a day to keep the batteries up. It seems like it takes forever to get to float. I generally shut the generator off when it gets down to 20 amps or so. Batteries are 2 year old MK 8d AGM's. Does that sound about right, or do I need to let the generator run until it goes to float?

I notice the owners manual for our old heart freedom 25/link 2000 recommends keeping the batteries between 50 and 90% charged.

Too much gen run time for the last 10% I think was mentioned

Re: Battery charging

Reply #8 – April 25, 2016, 05:41:45 pm

Been there, done that. On the sailboat, months at a time with no "shore power.

Most efficient use of charger/generator run time is charge to 85%, discharge to 50%, recharge to 85%......

Once a week, bring batteries to full charge so their capacity is not diminished..

Charge time is dependent on many factors: Number of amps discharged. Type of battery (AGM's will accept charge faster and turn less of it into heat. Amp output of charger. Voltage of charger (smart charger set to proper battery type, battery bank size and ambient temperature should be pretty close to ideal).

Re: Battery charging

Reply #9 – April 25, 2016, 05:52:13 pm

Quote from: Doug W. – April 25, 2016, 03:14:20 pm

Only put about 10 hours on my big generator but ran my Honda 2000 a few hours a day

I have considered a Honda 2000 several times, but can't convince myself to buy, carry and store a 3rd type of fuel...has anyone tried the LP conversion for the Honda 2000?

Re: Battery charging

Reply #10 – April 25, 2016, 07:08:43 pm

Thanks for the replies. That's about what I figured some where around 85%. Still thinking about solar or 2000 watt Honda. So far we have been doing a lot of dry camping, just hate to hear the 10k run just to run the battery charger.

Re: Battery charging

Reply #11 – April 25, 2016, 07:24:07 pm

On the relatively few occasions we dry camp, we usually draw down around 125 ah according to the Link 2000. That is less than 20% of the rated 750ah capacity of the three 8D AGM house batteries. We use about that amount if stopping overnight in cool weather or camping for a day in moderate temperatures in the desert.

I generally charge the batteries during our breakfast time. That includes running a waffle iron, Insta-Hot, lights, hair dryer, etc. Charging starts at about 100 amps. It takes about three hours to reach float voltage. If we are going to travel, we charge for one to two hours, and then complete charging with the alternator.

A small generator seems like a good idea. However, please consider how it affects your neighbors. My experience has been that our big diesel generators may be less annoying than small gasoline generators. The diesel generators generally are in insulated boxes and have good mufflers. While camping at Quartzite, I moved my coach about 100' (and beyond a few coaches to provide sound buffers) to get away from the noise of two compact Yamaha generators that ran 24 hours/day. (Yes, the coach was a FT. I didn't understand their requirement for 24 hour/day charging with gasoline generators.

) Their exhausts were pointed at my coach, and the constant noise was not consistent with the relative serenity of the desert.

Several folk ran diesel generators in the morning and occasionally during the day or evening. They used them as needed for cooking or entertainment. I hardly noticed those.

Dave Katsuki's solar arrays did not make any noise that I could hear. To the best of my knowledge, he never ran his generator.

Re: Battery charging

Reply #12 – April 25, 2016, 08:33:56 pm

Quote from: bbeane – April 25, 2016, 02:13:47 pm

When boondocking it takes about 3 hours of generator time a day to keep the batteries up. It seems like it takes forever to get to float. I generally shut the generator off when it gets down to 20 amps or so. Batteries are 2 year old MK 8d AGM's. Does that sound about right, or do I need to let the generator run until it goes to float?

That's about what it took me before installing the solar. Now it just takes about three hours of sun to get to 100%. Just got back from Joshua Tree, and in full sun, it was about the same charge time as when I was partially shaded by trees in Moab. Never ran the generator this trip, and what a pleasant trip it was. And I'm pretty convinced that the panels are shading the coach nicely, as well.

With all the shades drawn and those window awnings deployed on the sunny side (south,) the coach was about 74 degrees in the afternoon, when it was 90 degrees outside. The kids we were camping with would come in, faces beet red from rock climbing, just breathe in the cool air and say, "It's so cool in here!"

Re: Battery charging

Reply #13 – April 26, 2016, 12:14:03 am

Doug, will your 2000w Honda supply enough to run your charger if the battery's are real low? I see the max amps is 13.

Re: Battery charging

Reply #14 – April 26, 2016, 09:27:31 am

Bruce is right, you may have to use the "power share/power save" feature of the inverter/charger to limit how many amps of 120 VAC it uses.

Re: Battery charging

Reply #15 – April 26, 2016, 09:56:01 am

Or you can go a different route. I have a "earthquake" 800 watt 4 stroke inverter/generator, [as quiet as a honda 2000] and a 40 amp smart battery charger. Can use it on your coach or carry it over to someone else's.
Jim

Re: Battery charging

Reply #16 – April 28, 2016, 04:13:06 pm

Quote from: J. D. Stevens – April 25, 2016, 07:24:07 pm

Dave Katsuki's solar arrays did not make any noise that I could hear. To the best of my knowledge, he never ran his generator.

We actually do run our generator when we're running the microwave or induction cooker, and on cloudy days

. I moved the microwave and induction cooker circuits off the main inverter, since it's hard on a 2K inverter, and we only have 2 8D AGMs for the coach DC. If we've been using computers at night, I will often run the generator a little to bring the batteries up before shutting things down, since we have a residential fridge (on its own small inverter). Batteries never get below 75% on the Trimetric.

Re: Battery charging

Reply #17 – May 02, 2016, 12:32:50 pm

Update, been running the generator in the morning while making coffee and so on, and in the evening for about an hour and a half. Usually charging starts out at 12.40 V, I stop at about 98% charged that seems to be a good balance so I don't want to hear the generator run three hours all at one time, also fairly easy on batteries by not so deep a discharge.
Looks like we are going to do a lot of dry camping so starting to look into solar pricing and installation , anyone have any suggestions? The portable gen deal doesn't work for me.

Re: Battery charging

Reply #18 – May 02, 2016, 12:38:03 pm

Perchance one of our members has that great pic of a solar array on a FT?

Re: Battery charging

Reply #19 – May 02, 2016, 12:43:37 pm

When I am dry camping and need to run the generator, it starts out with the charger providing just over 100A. I let it run until the rate falls to 50A. After that I feel in getting too little bang for my generator buck.

Re: Battery charging

Reply #20 – May 02, 2016, 01:00:43 pm

Quote from: mike leary – May 02, 2016, 12:38:03 pm

Perchance one of our members has that great pic of a solar array on a FT?

Here are a couple of shots from Joshua Tree. The cool part about the second pic is that my old Bigfoot is in the background. Friends were waiting in line to buy it before it was even for sale, before I found the FT. And now there is a line for the FT, but they will be waiting a while!

Re: Battery charging

Reply #21 – May 02, 2016, 01:03:18 pm

Quote from: Tom Lang – May 02, 2016, 12:43:37 pm

When I am dry camping and need to run the generator, it starts out with the charger providing just over 100A. I let it run until the rate falls to 50A. After that I feel in getting too little bang for my generator buck.

Two or three house batteries? What charger?

Re: Battery charging

Reply #22 – May 02, 2016, 01:06:12 pm

Quote from: bbeane – May 02, 2016, 12:32:50 pm

Looks like we are going to do a lot of dry camping so starting to look into solar pricing and installation , anyone have any suggestions?

Seems like a few members have had solar done up in Oregon, the company name escapes me.

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