Charging House Batteries

[Fred Mc]

I have a question regarding chaging my house batteries.

Currently I have 3 12 volt gropu 31 batteries for starting.(GM PD4106) I also have 2x 6 volt golf cart batteries for the house system. Both the start batteries and the house batteries have separate disconnect switches. So far I haven't used them much (I don't full time) so  I charge the house batteries at home with a charger. When camping I disconnect the start batteries and connect the house batteries. I haven't charged the house batteries while running because I read somewhere that too high a charging rate could damage them.

First of all, can I connect both sets of batteries while running to charge them? Also, when camping can I start the engine on the start batteries and then connect the house batteries and disconnect the start batteries? I am aware that disconnecting all batteries while the engine is running can damage the alternator.

Thanks

Fred Mc.

[robertglines1]

Other will chime in..I see biggest problem charging the 2 6 volt in series I have done it but not along with 3 other 12 volt Bat charging same time. listening to reply curious my self

[Eagle Andy]

Hey Fred I have a very similar set up expect I have 2 8ds for start battries and two 6 volt for house battries , and three solor panels on the roof , that charge things at about 3 to 5 amps with good sun lol . I have a 2000 watt inverter charger that keeps everything charged up when Iam pluged in . When Iam driving the alt can charge everything but I turn off my switch to the house battries . I have a seperate switch isolate the house and start battries . Have I got you confused yet lol Hope this helped

[Tenor]

Yes you can charge your house batteries while driving down the road.  It'll be no big deal.  I do that all the time.  In fact, my alternator puts out enough electricity to run 2 roof airs through my inverter.  I'm not sure why you would start the coach and then switch to house batteries, but it shouldn't be any issue.

Good luck!

Glenn

[bevans6]

My bus is 24 volt but the principle is the same, since I have a 24 volt house battery pack (4 times 6 volt in series with a center tap and a Vanner for 12 volt use).  I just do the first cold start on the start batteries only, ideally I let the alternator charge them for 10 minutes or so, then I add the house batteries in parallel to the starts and leave it that way all day.  When I stop for the night I disconnect the start batteries from the house so any 12 volt or inverter use does not draw them down.

It works fine that way for me.  Now I am unsure of the exact electrical theory here, but I regard the alternator as a constant voltage supply, and the current supplied to each battery bank will be a function of it's state of charge.  The battery with the lowest state of charge will draw the most current, but as it reaches full charge the current drawn by it will drop off.  Certainly my experience so far is that both battery banks seem to stay charged just fine.  I also run my roof air from my inverter on the road, btw, and the house bank still ends up charged at the end of the day.

Brian

[bobofthenorth]

Our system is pretty simple too.  We have 2 x 8D wet cells for start batteries and 3 x 8D AGMs for the house.  They are separate systems with the house charged by a Freedom 25 when we are hooked to a current bush.  When I turn the key on there is a crossover solenoid that connects the two banks for starting and charging on the road.  I can defeat that automatic connection with a toggle switch next to the solenoid but the only time I do that is if I'm running the genset while we are travelling.  The generator output confuses my alternator and causes it to shut down which isn't such a big problem except that my tach signal comes off the alternator.

We've tried to measure how much start current comes from the house bank using the Trimetric but it likely doesn't react fast enough to give a real indication.  It jumps up to around 60 or 70 amps coming out of the house bank while the starter is engaged but my noisemaker starts so quickly that it is hard to get much of a measure.  If we run all day starting with an 80% house bank on the Trimetric we will likely end up close to 100% charged at the end of the day, depending on how much cooking we do on the road.

[gus]

I have two group 31 starters and two group 31 deep cycle house batteries.

I charge the start batteries first while under way and then connect the house batteries and charge them the last two-three hours of driving.

All the batteries were purchased at the same time and are five years old.

[TomC]

Much like others-I have 2-size 31 starting batteries (sealed wet batteries) and two 8D AGM batteries for house.  I have twin 150amp cross over solenoids (to equal the 300amp alternator) in parallel that has a switch on the dash for either working with the ignition switch off the starting batteries, or if the starting batteries are dead, I can activate the crossover solenoid by the deep cycle batteries too.  I have a 130 amp 3 stage charger on my Trace inverter.  So either charge the batteries going down the road with the big engine alternator, or with the genset through the inverter (turn off the crossover, as previously said, it confuses the big alternator), or through the inverter when at the power pole.  Has worked well.  Have even started the bus on the 2 8D AGM batteries when the starting batteries were dead.  And can use it as a booster to start in cold weather.

Highly recommend AGM batteries-no maintenance at all.  The terminals do not get dirty since there is no out gassing.  And as long as your alternator is not higher then 14.1 volts, can pump in as many amps charging as you can.  On my truck I'm going to use the Lifeline L16 6v batteries-6 total for 1200amp/hrs.  Good Luck, TomC

[rv_safetyman]

I try to keep the start and house systems separate at all times.  Like others, I have 31 start batteries (3).  My house batteries are golf cart.  I started out with 8 (marginal capacity if you keep them above 50% SOC for my pretty thirsty needs).  I just lost one golf cart, so I am down to 6 now.  The golf cart batteries were going to be my "first cut" but they lasted over 5 years, so I never got a change to go to the "next level".  I had thought that the next level would be L16s but I don't have the funds to step up to a new set right now.  Guess I will have to limp along on the 6 GC batteries for a while.

Back to the subject.  For the house batteries I charge them from the inverter when static and from a second alternator mounted on the engine when driving.  I went the second alternator route, as my main alternator is the original truck unit (135 amps?) and, since I wanted to keep everything separate, it just made sense.  The mounting configuration for the second alternator is the same as the main unit, so I could switch them out if I loose the main unit.

I have asked myself if charging from the alternator may have accelerated the death of the one battery.  Engine alternators typically are only one stage and that voltage can be pretty high in my opinion.  That is a good thing if my batteries are down, but if I have been on the post for a while and the batteries are fully charged, the voltage still seems high to me (over 14 volts when my float would be about 13.4 volts).

Typical Shepherd rambling

Jim

[gus]

Jim,

My understanding is the alt voltage stays up but the amps drop as the batteries approach full charge.

The alt volts need to stay up to keep power flowing from the alt instead of the batteries.

[pvcces]

Our batteries charge from three different sources, together or separately. The only time we notice any odd behavior is that the bus engine generator will kick off line if a different source is carrying the whole load. It immediately comes back on line if the load exceeds the other sources.

The three different sources are the bus engine generator, the inverter and solar system. Each does it's own regulating and we have never suffered any failure because of the setup, that we know of. We have had the relay that turns on the bus generator get oxidized contacts, but dressing the contacts puts it right back in operation.

For what it's worth.

Tom Caffrey

[Doug1968]

Fellows,

Some of you mention having installed a second alternator on the engine and using it to charge the house batteries. How are you doing this? I have a 8v92 and it does not have a free v pulley to drive a second alternator? Is there pulleys designed with more belt locations?

Doug

[luvrbus]

Doug, you should have a free one on the right side off the cam shaft if not I have a pulley that will bolt to crankshaft were you have belts now, no space left on the rear on a MCI with out doing major changes .


good luck

[Ed Hackenbruch]

I have the belt driven 24V alt. with 4 belts. The PO added a 12V alt. and just used one belt from the 24v to run it.

[Doug1968]

Clifford, there is a pulley on the r/h side. Not a very large diameter? Does this pulley turn the same RPM as the crank? It must I assume.

Clifford, this location works well for driving the spare alternator?

Doug